12P

St. Paul’s Convent School

Iron “sucks”! 鐵之吸收術師

By

Zoe Chu (朱曦瑜)

Karen Lau (劉愷寧)

Cherry Liu (廖卓齡)

Cherie Wong (黃意喬)

Stephanie Yeung (楊穎琪)

Teacher Advisor: Mrs. T. Tam (林少欣)

Submitted for participation in the Fifteen Hong Kong Chemistry Olympiad for Secondary Schools

From St. Paul’s Convent School

聖保祿學校 March 2010

Presentation materials: 1 CD-R disc (1 video clip and several digital photographs incorporated in a PowerPoint Presentation)

Abstract

Our research paper involves using a common household waste - used hand warmer powder to treat water pollutants. As the chemical composition of used hand warmer powder might resemble another frequently used industrial adsorbent - hydrous ferric oxide, we hypothesised that used hand warmer powder might exhibit similar effects on heavy metal ions, phosphate and dichromate. We synthesized hydrous ferric oxide to test our hypothesis. We have also investigated the adsorption abilities of materials isolated in the hand warmer powder, treated hand warmer powder and powder of different brands in order to derive a method which optimizes adsorption effects. After experimentation, we found that for adsorbing PO4

3− and Ni2+ ions, the used hand warmer powder should be treated with dilute hydrochloric acid; for adsorbing Cr2O7

2−, Zn2+, Cu2+ and Pb2+ ions, no treatment is needed; and the longer the adsorbents are allowed to stand in the solutions, the more pollutants will be adsorbed. We also packed burettes and a compartmentalized filtration device with the most effective adsorbent among untreated hand warmer powders and passed solutions of heavy metal ions, phosphate and dichromate into it to simulate real life situation, it was found that the burette is a much more effective device.

Contents

Page

Introduction

1 - 2

Part I - Preparation of various adsorbents

IA - Preparation of hydrous ferric oxide (HFO)

IB - Preparation of Processed Hand Warmer Powder (HWP)

3 - 15

Part II - Investigating the effectiveness of anion adsorption on

various adsorbents

IIA - Determination of PO43-

adsorption

IIB - Determination of Cr2O72-

adsorption

16 - 37

Part III - Investigating the effectiveness of cation adsorption on

various adsorbents

IIIA - Determination of Zn2+

adsorption by EDTA titration

IIIB - Determination of Cu2+

and Ni 2+

adsorption by colorimetric

measurement

IIIC - Determination of Pb2+

adsorption by gravimetric analysis

through precipitation

IIID Determination of hardness adsorption by EDTA titration

38 - 77

Part IV Investigating the effectiveness of filtration device and the

regeneration of HFO in the device

78 - 89

Sources of Error and Suggestions for Improvements

90 - 93

Conclusion

94 - 97

References

98

P. 1

Introduction

Water pollution has been a serious problem worldwide. The clean water sources round the

globe have become very limited and waste water such as factory effluents contains many

pollutants like heavy metals ions, harming the wildlife and human environment when

discharged. Many people have been making an effort in finding new and better ways of

water treatment in order to reuse water. But so far most water treatment programs involve

a huge amount of resources and are very expensive even for both commercial and

domestic use.

After reading a number of academic papers as reference, we found that iron compounds

were claimed to be effective in adsorbing anions like phosphate as well as various heavy

metal ions such as copper(II) and nickel(II) ions, the major pollutants found in waste

water. Thus in this project, our group will try to explore a cheaper and more recyclable

way to treat water, using iron compounds. We will also make an attempt in using used

hand warmer powder with iron oxides as its main ingredient to treat waste water. Hand

warmer powder can be commonly found in households and so it would be a good

domestic adsorbent source.

In part I, we will first prepare hydrous ferric oxide (HFO) of different structures by

mixing iron(III) chloride solution and aqueous sodium hydroxide or ammonia and

varying the pH of the supernatant liquid. Since the chemical composition of used hand

warmer powder might be similar to that of HFO, we will identify substances present in

the powder, possibly unused iron, hydrous iron(III) oxide, activated carbon and

vermiculite, and try to isolate them. HFO prepared under different pH, hand warmer

powder of different brands, hand warmer powder treated with hydrochloric acid under

different conditions, iron filings, iron(III) oxide and activated carbon will later be tested

as adsorbents.

Vermiculite + Activated carbon

P. 2

In part II, we will focus on the effectiveness of anion adsorption. For part IIA, we will

investigate the effectiveness of the adsorbents mentioned above on phosphate adsorption

by colorimetric measurement with the addition of ammonium molybdate followed by

tin(II) chloride to the treated water samples. The phosphate content of each treated water

sample can be obtained by comparing the absorbance with a calibration curve.

For part IIB, we will investigate the effectiveness of dichromate adsorption on the

adsorbents mentioned above by colorimetric measurement as the colour intensity of

dichromate solution changes with its concentration. We will also investigate the effect

of time on dichromate solution adsorption of a particular adsorbent by varying the

duration of the adsorbent in contact with dichromate solution.

In part III, we will investigate the effectiveness of the adsorbents on heavy metal ions (e.g.

Cu2+

, Zn2+

, Pb2+

, Ni2+

) and hardness (i.e. Ca2+

, Mg2+

) adsorption. For part IIIA, the effect

of Zn2+

adsorption will be determined by carrying out titration against EDTA. For part

IIIB, the effect of Cu2+

, Ni2+

adsorption will be investigated by colorimetric measurement,

with the addition of ethane-1,2-diamine to the water samples containing Cu2+

and Ni2+

.

For part IIIC, the effect of Pb2+

adsorption will be investigated. Yellow precipitate will be

formed by adding excess KI solution to the treated water samples with Pb2+

. The

precipitate will then be allowed to dry and the Pb2+

content can then be determined

indirectly by measuring the dry mass of the precipitate of each sample. For part IIID,

the effect of Ca2+

, Mg2+

and hardness of mineral water adsorption will be determined by

carrying out titration against EDTA. We will also investigate the effect of time on Cu2+

solution adsorption of a particular adsorbent by varying the duration of the adsorbent in

contact with dichromate solution.

Our ultimate aim is to find out a way of treating hand warmer powder so that its

effectiveness in removing harmful substances in water is at its highest.

In part VI, we will determine the effectiveness of toxic ions removal by hand warmer

powder-packed columns. Known volumes of phosphate, dichromate, copper(II), zinc,

lead(II) and nickel(II) ion solutions will be allowed to pass through the

Warmergotchi-packed columns. The amount of the remaining anions / metal cations in

the resulting solutions will be determined by gravimetric measurement. Moreover, we

will also investigate the effectiveness of the regeneration of hydrous ferric oxide, by

adding dilute sulphuric acid to the adsorbents to reverse the reaction.

P. 3

Part IA Preparation of hydrous ferrous oxide (HFO)

Objective:

To prepare samples of hydrous ferrous oxide under different pH conditions

Principle:

Hydrous ferric oxide are obtained from reacting FeCl3(aq) with NaOH(aq) until the pH of

the supernatant liquid reached pH 5, pH 7 and pH 9. This is to investigate under which

pH would produce a hydrous ferric oxide of a high level of activity. To attain the desired

pH, the pH of the supernatant liquid is determined by using a pH paper, if the pH is too

low, dilute aqueous sodium hydroxide is added and when the pH is too high, dilute

hydrochloric acid is added as needed. HFO can also be produced by reacting FeCl3(aq)

with alkaline NH3(aq).

Fe3+

(aq) + 3OH(aq) Fe(OH)3(s)

The brown Fe(OH)3 precipitate is aged with the mother liquor for 5 days. Then, the

supernatant liquid is filtered under suction and the while being washed with water until

acid free. The aging of the reactant mixture and the washing steps as described are

important to develop the physical properties such as high surface area and abrasion

resistance of the final product. After filtering the precipitate under suction until shrinkage

of the precipitate is complete, it is dried at 60℃ in an air oven for sufficient duration to

reduce the water content of the product. If the drying step is initiated before sufficient

water has been removed by filtering under suction, the product will be too soft. The

product is then prepared for use by grinding.

Fe(OH)3(s) FeO(OH)(s) + H2O(l)

hydrous ferric oxide (HFO)

Chemicals used:

Anhydrous iron(III) chloride

1M sodium hydroxide solution

P. 4

1M ammonia solution

1M hydrochloric acid

Apparatus used:

Electronic balance

Glassware

Suction filter

Oven

Procedures:

1. 7.60g of anhydrous iron(III) chloride was

weighed accurately and was transferred to a large

beaker.

2. 1M sodium hydroxide solution was added to the anhydrous iron(III) chloride until

the pH value of the supernatant liquid has reached pH 5.

3. The above procedures were repeated and the pH values of the supernatants were

adjusted to pH 7, 9 and 11 respectively, in which suitable volumes of 1M

hydrochloric acid were added in order to adjust the pH.

4. 1M ammonia solution was used instead of 1M sodium hydroxide solution in one

condition under pH 7.

The mixtures were allowed to stand for 5 days.

pH 5

(NaOH)

pH 5

(NaOH) pH 7

(NaOH)

pH 9

(NaOH)

pH 11

(NaOH)

pH 7

(NH3)

P. 5

5. The mixtures were filtered under

suction and the residues were washed

and collected.

6. The residues were dried in the oven at 60˚C for about 12 hours, which were then

ground and weighed.

Results:

Mass of HFO obtained under different experimental conditions:

Batch Mass of

anhydrous FeCl3

(g)

1M NaOH

(cm3)

1M HCl

(cm3)

pH

value

Mass of HFO

made (g)

1 7.60 118 (NaOH) - 5 3.30

2 6.08 89.5 (NaOH) - 5 2.75

3 7.60 140.5 (NaOH) 1.25 7 5.18

4 7.60 285 (NH3) - 7 4.40

5 7.60 130 (NaOH) - 9 3.80

6 3.04 123.5 (NaOH) 65 11 1.31

P. 6

Discussion:

Results show that the yield of HFOs was the highest under the pH condition of pH 7. The

thickness and fineness of the solids were after the five-day period was observed to be

different for different pH conditions. The mass of solid after filtration and drying was

found to be the greatest for the condition under pH7. Thus, we found that pH 7 is a

favourable condition for the formation of HFO.

P. 7

The filtration procedure for the

condition of pH 5 was most

time-consuming and repetitive. Not

only did the mixture filter slowly, but

the residues of the condition pH 5

often passed through the filter paper

and entered the filtrate. It can be

deduced that the particle size of the

HFO formed under pH 5 was the

smallest, leading to easier blocking

and passing through of filter paper

pores. This may have an effect on the

adsorption ability of HFO due to an increased surface area.

As seen from the above photo, the supernatant liquid of the second

left beaker (Batch 2) appears to be quite reddish-brown. We

deduced that it may be due to experimental errors during the

adjustment of pH value. The actual pH of the supernatant liquid

may be below pH 5, or that the mixture was stirred excessively,

which results in a lot of iron(III) ions (reddish-brown in colour)

still in aqueous form without being precipitated out, thus giving

the supernatant liquid a reddish-brown colour. It can be deduced

that minimizing the mixing of the precipitate and supernatant

liquid was important to obtaining a higher yield of HFO.

By comparing the yields of batches 3 and 4, the HFO yield of batch 3 which used sodium

hydroxide was higher than that of batch 4 which used ammonia solution. Although 1.25

cm3 of 1M hydrochloric acid was added to the mixture in batch 3, this volume was

considered insignificant compared to the 140.5 cm3 of 1M sodium hydroxide present.

Therefore, we found that sodium hydroxide solution was a better alkali to be used in the

preparation of HFO than ammonia solution.

Batch 3

pH 7 (NaOH)

Batch 4

pH 7 (NH3)

P. 8

Part IB Preparation of Processed Hand Warmer Powder (HWP)

Objective:

To identify and isolate materials remained in used hand warmer powder by different

treatments.

Principle:

The materials remained in used hand warmers were isolated and investigated individually

for their adsorption effects. Used hand warmers usually consist of unused iron, hydrous

iron(III) oxide, NaCl, activated carbon, and vermiculite. Different treatments would be

used to find out which one would produce hand warmer packs with the best adsorption

effect.

Treatments: Changes in the amount of the following substances: Implications:

Fe Hydrous

ferric

oxide

Fe2O3 Vermiculite Activated

carbon

Dilute HCl

(2 hrs, 4 hrs, 6

hrs)

Reduced

*

Reduced

*

Unchanged Unchanged Unchanged Fe2O3 takes up a

much larger

proportion than Fe in

the known mass of

the treated hand

warmer

Dilute HCl +

Heat

(2 hrs, 4 hrs, 6

hrs)

Reduced

*

Reduced

*

Reduced

*

Unchanged Unchanged Fe2O3 takes up a

similar proportion as

Fe in the known mass

of the treated hand

warmer

Conc HCl

(2 hrs, 4 hrs, 6

hrs)

Almost

completely

removed

*

Almost

completely

removed

*

Almost

completely

removed

*

Unchanged Unchanged The treated hand

warmer contains

mostly vermiculite

and carbon, with very

little Fe and Fe2O3. Conc HCl

(48 hrs)

Completely

removed

Completely

removed

Completely

removed

Unchanged Unchanged The treated hand

warmer contains pure

vermiculite and carbon.

* The amount removed increases with time.

P. 9

The adsorption effects of iron powder, iron(III) oxide, and activated carbon available in

the laboratory would also be investigated to see which component in the hand warmer

powder with the best adsorption effect is mainly responsible for adsorbing the ions, and

to see with what treatment can the adsorption effect of used hand warmer powder be

optimized.

Chemical used:



Hand warmer powder (白元)

Apparatus used:

Hotplate magnetic stirrer

Suction filter

Oven

Electronic balance

Glassware

Procedures:

Treatment A

1. 300 cm3 of 2M hydrochloric acid

was added to 20.0g of used hand

warmer powder.

2. The mixture was allowed to stand for

2 hours.

3. The mixture was filtered under

suction and the residue was washed

and dried in an oven.

4. The above procedures were repeated

twice, where the mixtures stood for 4

hours and 6 hours respectively.

P. 10

Treatment B

1. 300 cm3 of 2M hydrochloric acid was added to 20.0g of used hand warmer

powder.

2. The mixture was heated at 60 ˚C for 2 hours.

3. The mixture was filtered under suction and the residue

was washed and dried in an oven.

4. The above procedures were repeated twice, where the

mixtures were heated for 4 hours and 6 hours respectively.

Treatment C

1. 300 cm3 of 2M hydrochloric acid was added to 20.0g of

used hand warmer powder.

2. The mixture was allowed to stand for 2 hours.

3. The mixture was filtered under suction and the residue was washed and dried in

an oven.

4. The above procedures were repeated twice, where the mixtures stood for 4 hours

and 6 hours respectively.

Treatment D

1. 200 cm3 of 11M hydrochloric acid was

added to 20.0 g of used hand warmer powder.

2. The mixture was allowed to stand for 2 days

in a fume cupboard till the remaining powder was no

longer magnetic.

3. The mixture was filtered under suction and

the residue was washed and dried in an oven.

P. 11

Results:

Mass of hand warmer powder (HWP) obtained after treatments

Batch of

HWP

(20.0g

each)

HCl added Time

(hours)

Heated?

(Y/N)

Mass of Processed

HWP made (g)

%

yield

(%)

Volume

(cm3)

Molarity

A1 300 2M 2 N 13.04 Average

12.70

63.52

A2 300 2M 4 N 13.48

A3 300 2M 6 N 11.59

B1 300 2M 2 Y(60 ˚C) 6.46 Average

6.803

34.02

B2 300 2M 4 Y(60 ˚C) 6.26

B3 300 2M 6 Y(60 ˚C) 7.69

C1 100 11M 2 N 6.06 Average

5.33

26.63

C2 100 11M 4 N 5.59

C3 100 11M 6 N 4.33

D 200 11M 48 N 3.22 Average

3.04

15.20

200 2M 48 N 2.86

A1 B1 C1 D

A2

A3

B2

B3

C2

C3

P. 12

Observations and inferences made on the HWP remained

Batch of HWP Treatment Observation Magnetic

Used hand

warmer

powder

-- a mixture of black powder, brown powder

and shiny solids

Yes

A add dil HCl solution turned green, colourless gas

bubbles evolved

Yes

B heat with dil

HCl

solution turned greenish yellow, colourless

gas bubbles evolved

Yes

C add conc HCl solution turned brown, colourless gas

bubbles evolved

slightly

D add conc HCl

(48 hrs)

solution turned brown, colourless gas

bubbles evolved

No

Used Hand Warmer Powder

P. 13

Discussion:

The hand warmer powder manufacturer claimed

that the hand warmer powder contained iron,

activated carbon, vermiculite, and sodium

chloride (assuming negligible mass). Thus we

deduced that the used hand warmer powder

contained unreacted iron, iron(III) oxide,

vermiculite, activated carbon and sodium

chloride. The series of treatments we conducted

allowed us to prepare samples of used hand

warmer powder which underwent different

treatments and enabled us to confirm the constituents present in each of them.

Based on the above results and observations, we made some deductions. If the resulting

powder is magnetic, it can be deduced that iron and iron(III) oxide may be present. The

presence of black powder may be due to the activated carbon. The appearances of shiny

solids may be due to the mineral vermiculite. Any

sodium chloride would have dissolved in the mixture

and thus would not be present in the processed HWP.

As for the original HWP, sodium chloride would also

dissolve in the aqueous solution in which the powder is

to be placed into for adsorption. Therefore, the

presence of sodium chloride can be negligible.

Deduced composition in processed HWP under different treatments

Batch of HWP Treatment Composition in remaining powder

original -- Fe + Fe2O3 +

vermiculite + activated C

A add dil. HCl traces of iron + mainly Fe2O3 +


B heat with dil. HCl traces of Fe + traces of Fe2O3 +


C add conc. HCl traces of Fe2O3


D add conc. HCl for 2

days


P. 14

Processed HWP

Together with the investigation of adsorption effects of

independent materials from the HWP, the adsorption effect of used

HWP under different treatments can be compared. By taking these

results into account when we are going to investigate the

adsorption effects on different ions, we can adjust our treatment for

the HWP to produce HWP with the most adsorption effects.

From the results of treatment A, it was observed that the solution

turned green and colourless gas bubbles evolved. We deduced that most iron has

dissolved in the acid to form Fe(II) ions, producing colourless gas bubbles giving the

solution a green colour. Since treatment A mainly removed iron, what remained in the

residue were traces of iron, mainly iron(III) oxide, vermiculite and activated carbon. In

our further investigations to be followed, if the adsorption effect of untreated used HWP

is higher than that of treatment A, then it can be deduced that iron has the ability to

adsorb. This could be confirmed by comparing the adsorption effect of iron powder

alone.

A1

A2

A3

B1

B2

B3

C1

C2

C3

D

P. 15

From the results of treatment B, the solution was observed

to be greenish-yellow. This shows that the amount of

iron(III) oxide that dissolved in acid to give yellowish Fe(III)

ions was greater than that in treatment A. Thus in the

processed HWP in treatment B, the proportion of iron and

iron(III) oxide would be similarly low. In our following

investigations, if the adsorption effect of processed HWP in

treatment A was much better than that in treatment B, it can

be deduced that iron(III) oxide was effective in adsorption.

For the processed HWP in treatments C and D, the composition in the remaining powder

should be similar, in which there only remains mainly vermiculite and activated carbon.

Since the treatment time for treatment C is shorter than that of D, there would probably

be more iron(III) oxide traces in C than in D. If our hypothesis, iron(III) oxide possesses

adsorption ability, is correct, then the adsorption effect of processed HWP from treatment

C would be better than that of D.

C1 D

P. 16

Part IIA PO43-

adsorption

Objective:

To investigate the effectiveness of PO43-

adsorption on various adsorbents by colorimetric

measurement

Principle:

Phosphate binds to hydrous ferric oxide through a direct ionic interaction between one or

two negatively charged oxygen ions on the phosphate with the ferric ions (Fe3+

) in the

solid. The figure below shows phosphate in solution bound via two ionic bonds, with the

displacement of hydroxide.

Since phosphate binging takes place at the surface of the HFO instead of deep below the

surface, the larger the surface area, the more phosphate the adsorbent can bind.

To investigate the effectiveness of adsorbing phosphates by adsorbents, the Molybdenum

Method is used. Phosphate in water combines with heptamolybdate to form a yellow

complex. When SnCl2(aq) is added, the yellow complex turns blue as the oxidation state

of molybdenum changes +6 to +5.

7H3PO4 + 12(NH4)6Mo7O24 + 51H+

→ 7(NH4)3PO4∙12MoO3 + 51NH4+ + 36H2O

Mo(VI)-yellow complex + Sn2+

→ Mo(V)-blue complex + Sn4+

The intensity of the blue colour produced is proportional to the amount of phosphate ions

present, and the absorbance can be measure using a colorimeter. A calibration curve

O

Fe

Fe

OH

OH

+ P

OH

O-

O

O- Fe

Fe

O

O

+ 2H2O + H+

O

P

OH

O

P. 17

would be first made with the colorimeter readings of PO43-

solutions with various

concentrations. By comparing the absorbance of the water samples treated with various

adsorbents with the calibration curve, the phosphate concentration in the solutions can be

obtained. The types of adsorbents used include the different forms of HFO prepared

previously so as to compare which method would create the best adsorbent for PO43-

.

Chemicals used:

Ammonium Molybdate ( (NH4)6Mo7O24．H2O)

Tin(II) chloride (SnCl2．2H2O)

Sodium phosphate (Na3PO4)

2M Hydrochloric acid (HCl)

11M Hydrochloric acid (HCl)

HFO 1 (prepared with NaOH at pH 5)



HFO 4 (prepared with NH3 at pH 7)



Iron filings (Fe)

Iron(III) oxide powder (Fe2O3)

Activated carbon

Vermiculite + activated carbon

A1 – Processed Hand warmer powder (treated with dilute HCl for 2 hours)



B1 – Processed Hand warmer powder (treated with dilute HCl with heat for 2 hours)



C1 – Processed Hand warmer powder (treated with concentrated HCl for 2 hours)


Ammonium Molybdate

Tin(II) chloride

Sodium phosphate

P. 18


Hand warmer powder (白元)

Hand warmer powder (ドうくん)

Hand warmer powder ( Warmergotchi)

Hand warmer powder ( Pocket Sun)

Hand warmer powder (ホカロン)

Various adsorbents

Apparatus used:

Electronic balance

Colorimeter

Glassware

P. 19

Procedures:

Preparation of ammonium molybdate solution

2.4g of (NH4)6Mo7O24．H2O (molar mass: 1235.86 g)was added to 100 cm3 1M

H2SO4(aq). The result solution has a concentration of 0.0194 M.

Preparation of Tin(II) chloride solution

1.0g of SnCl2(molar mass:325.63 g) was added to 100 cm3 1M HCl(aq). The result

solution has a concentration of 0.0307 M.

Colorimetric measurements of phosphate solutions

1. 0.5g of Na3PO4．12H2O was added to 250.0 cm3 of deionised water. Then the

standard solution of PO43-

(aq) was diluted in different ways listed as follows:

A. 5.0 cm3

of standard solution in 250.0 cm

3 of deionised water

B. 10.0 cm3

of standard solution in 250.0 cm3

of deionised water

C. 15.0 cm3

of standard. solution in 250.0 cm3

of deionised water

D. 20.0 cm3


of deionised water

E. 25.0 cm3


of deionised water

F. 35.0 cm3


of deionised water

G. 45.0 cm3 of standard solution in 250.0 cm3 of deionised water

2. 25.0 cm3

of each solution was pipetted into a 100 cm3

beaker.

A B C D E F G

P. 20

3. 2.0 cm3 of 0.0194 M ammonium molybdate solution was added to each beaker.

4. 12.0 cm3 of 0.0307 M tin(II) chloride solution and 25.0 cm

3 of deionised water

were pipetted to each beaker.

5. The solutions were then transferred to the test tubes.

6. The colour intensities of the solutions were compared with a colorimeter.

Colorimetric measurements of phosphate solutions with various adsorbents

1. 20.0 cm3

of solution G was pipetted into each beaker containing

0.5 g of an adsorbent.

A B C D E F G

A B C D E F G

P. 21

2. The mixtures were allowed to stand for 9 hours.

3. The mixtures were filtered and the collected filtrate was made up to 30 cm3 with

deionised water.

5. 5.0 cm3 of filtrate was pipetted into a 100 cm

3 beaker.

6. 2.0 cm3 of 0.0194 M ammonium

molybdate, 12.0 cm3 of 0.0307

M SnCl2 and 25.0 cm3 of

deionised water were added into

each beaker.

7. The mixtures were transferred

into test tubes.

8. The colour intensities of the

mixtures were tested with a

colorimeter.

P. 22

Results:

Absorbance values of phosphate solutions A to G

Solutions A B C D E F G

Absorbance 0.18 0.34 0.50 0.65 0.85 0.95 1.40

Calibration Graph for Standard Phosphate Solution

A B C D E F G

P. 23

Absorbance of Various Phosphate Solutions after Adsorption

Adsorbent (20.0 cm3 diluted to 30.0

cm3)

Absorbance of

phosphate

solution

(Absorbance x

1.5)

% change in

absorbance

(#)

Concentration

of phosphate

solution

(× 10-4

mol dm-3

)

1. HFO 1 (NaOH, pH 5) 0.05 (0.075) -99.58% 0.37

2. HFO 2 (NaOH, pH 5) 0.02 (0.03) -98.33% 0.2888

3. HFO 3 (NaOH, pH 7) 0.06 (0.09) -95.00% 0.8664

4. HFO 4 (NH3, pH 7) 0.015 (0.0225) -98.75% 0.2166

5. HFO 5 (NaOH, pH 9) 0.33 (0.495) -72.50% 3.1962

6. HFO 6 (NaOH, pH 11) 0.31 (0.465) -74.17% 2.99

7. Hand warmer powder (白元) 0.54 (0.81) -55.00% 5.4236

8. Iron filings 0.98 (1.47) -18.33% 10.44

9. Iron(III) oxide powder 0.90 (1.35) -25.00% 9.50

10. Activated carbon 0.30 (0.450) -28.57% 9.40

11. Vermiculite + activated carbon 0.30 (0.45) -75.00% 2.888

12. A1 – Processed HWP (dil. HCl + 2 hr) 0.045 (0.0675) -96.25% 0.321



15. B1 – Processed HWP (dil. HCl + 2 hr + heat) 0.20 (0.30) -83.33% 1.87



18. C1 – Processed HWP (conc. HCl + 2 hr) 0.295 (0.4425) -75.42% 2.836



21. HWP (ドうくん) 0.22 (0.33) -81.67% 2.07

22. HWP ( Warmergotchi) 0.20 (0.3) -83.33% 1.866

23. HWP ( Pocket Sun) 0.70 (1.05) -41.67% 7.187

24. HWP (ホカロン) 0.34 (0.51) -71.67% 3.302

25. Control / (1.8) / 13.165

# = absorbance of phosphate solution after treatment – absorbance of control

absorbance of control × 100%

P. 24

Concentration of Phosphate Solutions after Adsorption by Different Adsorbents

(From left to right)

HFO pH5 (x2), pH7 (x2),pH 9, pH 11,


Iron(III)oxide, iron filings, A1-3, B1-3, control

P. 25

Discussion:

From the graphs above, we can see that HFO 4 is most effective in the removal of

phosphate while activated carbon is least effective. The absorbance values of HFO were

the lowest in average, while those of processed hand warmer powder varied.

Among the HFO samples, we found that the absorbance of HFO treated in acidic or

neutral mediums (samples 1 to 4) were higher than that of HFO treated in an alkaline

medium (samples 5 to 6). But the general adsorption performance of HFO samples was

very satisfactory.


HFO pH5

HFO pH5

HFO pH7

HFO pH7

HFO pH9

HFO pH11

Control

P. 26

The adsorption power of the original hand warmer powder sample (sample 7) was found

to be higher than those of iron filings, iron(III) oxide and activated carbon alone. But

since suspension was observed in the samples of iron filing and iron(III) oxide powder,

the absorbance values above could not accurately reflect their effectiveness in the

removal of phosphate alone. The effectiveness in the removal of phosphate is higher

when a mixture of the above ingredients is used.


HWP (白元)

Iron fillings

Iron(III) oxide powder

Activated carbon


Control

P. 27

Most of the treated hand warmer powder samples were found to be more effective

phosphate adsorbents than the original hand warmer powder. Among the processed hand

warmer powder samples (A1 to C3), the absorbance values of samples with the addition

of dilute HCl(A samples) were lower than those of samples with addition of concentrated

HCl or heating with dilute HCI. Referring to part I about the preparation of processed

hand warmer powder, samples C1 to C3 are mainly composed of vermiculite and

activated carbon. The experimental absorbance values of C samples matched with that of

the mixture of vermiculite and activated carbon. It is likely that C samples have similar

compositions.

As for samples A1 to B3, A samples mainly comprises iron(III) oxide, while B samples

contains more iron atoms and less iron(III) oxide in composition. As the absorbance

values of A samples were significantly lower than those of B samples, it can be deduced

that iron(III) oxide is more effective than iron in the removal of phosphate ions.


A1, A2, A3

B1, B2, B3

control

P. 28

Among all hand warmer powder brands, Warmergotchi hand warmer powder was found

to be the most effective phosphate adsorbent while the lowest effectiveness was observe

for Pocket Sun hand warmer powder.

From the above data, we can see that some used hand warmer powder samples, like

sample 21 (ドうくん) and sample 22 (Warmergotchi), can also serve as effective

phosphate adsorbents, as compared to the percentage change in absorbance of HFO

samples.

To maximise the effectiveness of the hand warmer powder, the powder can be first treated

with dilute hydrochloric acid and allowed to stand for above 2 to 6 hours, since the

adsorption power of such treated samples have similar or even higher phosphate removal

power than HFO samples.


HWP (白元)

HWP ( Pocket Sun)

HWP ( Warmergotchi)

HWP (ドうくん)

HWP (ホカロン)

Control

P. 29

Part IIB Cr2O72-

adsorption

Objective:

To investigate the effectiveness of Cr2O72-

adsorption on various adsorbents by

colorimetric measurement and the time effect on adsorption abilities.

Principle:

Dichromate ions are stable only in acidic medium and will be converted to chromate ions

at high pH:

Cr2O72-

+ H2O 2CrO42-

+ 2H+

When dichromate ions in the solution are in contact with the basic surface of HFO, the

chromate ions formed would then be absorbed by HFO according to the following

equation due to the high surface positive charge density of HFO. The an electrostatic

attractive force between the solid adsorbent and adsorbate causes the chromate ions to

bind to HFO.

To investigate the effectiveness of chromium(VI) adsorption of various adsorbents, the

colorimeter is used to measure the absorbance of the water samples, the lower the

absorbance, the more effective is the adsorbent used.

To investigate the effect of time on chromium(VI) adsorption of a particular adsorbent,

the time period for the adsorbent being in contact with dichromate solution is varied and

the absorbance values are compared.

O

Fe

Fe

OH

OH

+ Cr

OH

O-

O

O Fe

Fe

O

O

Cr + 2H2O + H+

O

O

O

P. 30

Chemicals used:

0.01M Potassium dichromate (K2Cr2O7)

Various adsorbents

Apparatus used:

Electronic balance

Colorimeter

Glassware

Procedures:

1. 25.0 cm3

of 0.01M K2Cr2O7 was added to 0.5g of different adsorbents in a

beaker.

2. The mixtures were allowed to stand for 9 hours. Solution samples containing

HFO at pH 7 and ホカロン hand warmer powder were allowed to stand for 1, 3,

5 and 7 hours respectively.

3. The mixtures were filtered and the filtrate collected was transferred into its

respective test tube.

4. The colour intensities of the mixtures were determined with a colorimeter.

P. 31

Results:

Dichromate adsorption:

Adsorbent absorbance % change in absorbance

1. HFO (NaOH, pH 5) 1.0 -50.00%

2. HFO (NaOH, pH 7) 0.85 -57.50%

3. HFO (NaOH, pH 9) 0.925 -53.75%

4. Hand warmer powder (白元) 1.50 -25.00%

5. Iron filings 2.0 0.00%

6. Iron(III) oxide powder 1.80 -10.00%

7. Activated carbon 1.30 -35.00%

8. Vermiculite + activated carbon 1.70 -15.00%

9. A2 - Processed HWP (dil. HCl + 4 hr) 1.75 -12.50%

10. B2 - Processed HWP (dil. HCl + 4 hr + heat) 1.80 -10.00%

11. C2 - Processed HWP (conc. HCl + 4 hr) 1.70 -15.00%

12. HWP (original, Pocket Sun) 1.50 -25.00%

13. HWP (original, Warmergotchi) 1.45 -27.50%

14. HWP (original, ドうくん) 1.30 -35.00%

15. HWP (original, ホカロン) 1.20 -40.00%

16. Control 2.0 /

# = absorbance of dichromate solution after treatment – absorbance of control

absorbance of control × 100%

P. 32

Time effect on dichromate adsorption:

Duration Cr2O7

2-

+ HFO (pH 7)

% change in

absorbance

Cr2O72-

+ HWP (ホカロン)

% change in

absorbance

Control 1.7 / 1. /

1 hr 1.4 -17.6% 1.7 0%

3 hr 1.2 -29.4% 1.6 -5.9%

5 hr 1.1 -35.3% 1.5 -11.8%

7 hr 0.9 -47.1% 1.5 -11.8%

Control HFO pH7 (1 hr→3hrs→5hrs→7hrs) HWP ホカロン(1 hr→3hrs→5hrs→7hrs)

P. 33

Discussion:

Dichromate absorption:

From the data above, HFO treated in a neutral medium (sample 2) was found to be most

effective in the removal of dichromate while iron filings (sample 5) were shown to be the

least effective adsorbents.

The average adsorption power of HFO was the highest among all absorbents. HFO

treated in neutral and alkaline mediums (samples 2 and 3) were found to have better

adsorption effects than that treated in an acidic medium (sample 1). It is likely that

neutral and alkaline mediums favour dichromate adsorption of HFO. Moreover,

dichromate ions are likely to be converted to chromate ions at high pH and therefore

absorbed by HFO.


HFO (NaOH, pH 5)

HFO (NaOH, pH 7)

HFO (NaOH, pH 9)

Control

P. 34

According to the data above, the adsorption power to adsorb dichromate was found to be

higher for hand warmer powder than that of each ingredient. However, as suspension was

observed in the samples of iron filings and iron(III) oxide powder, the absorbance values

above could not accurately reflect their effectiveness in the removal of dichromate alone.

Compared with the sample with activated carbon alone, the effectiveness in the removal

of dichromate was found to be lower for the mixture of activated carbon and vermiculite.

It can be deduced that vermiculite is not effective or even hinders the removal of

dichromate.


HWP (白元)

Iron filings

Iron(III) oxide powder

Activated carbon


Control

P. 35

Among the treated hand warmer powder samples, the one treated with concentrated

hydrochloric acid (sample 11) had a slight higher dichromate adsorption power than the

other treated samples. However, the original hand warmer powder was found to be more

effective than all treated samples.


HWP (白元)

A2

B2

C2

HWP (Pocket Sun)

HWP (Warmergotchi)

HWP (ドうくん)

HWP (ホカロン)

Control

P. 36

Among all the brands, hand warmer powder of brand ホカロン was shown to be the

most effective dichromate adsorbent.

Although the average dichromate adsorption power of HFO is the highest, some used

hand warmer powder samples, like sample 14 (ドうくん) and sample 15 (ホカロン)are

also very effective in the removal of dichromate. Thus they are also desirable dichromate

adsorbents because they are easily available for domestic use. They also save much time

and cost spent on the preparation of HFO.

For both and PO43-

and Cr2O72-

adsorption, HFO samples were found to be the most

effective adsorbents. Moreover, the hand warmer powder mixture works better than the

separate pure components do.

However, different treatments of hand warmer powder did not show a big discrepancy in

the effectiveness of dichromate removal, unlike the case in phosphate adsorption. In

dichromate adsorption case, the original hand warmer powder was found to be even more

effective than the treated samples. Thus we recommend used hand warmer powder of the

mentioned brands for phosphate and dichromate removal. As for phosphate removal, an

even more effective way will be treating the powder with dilute acid for 2 to 6 hours

before use.

P. 37

Time effect on dichromate absorption:

Regarding the optimum amount of time for the immersion of adsorbents in dichromate

ion solution, with HFO at pH7 as the adsorbent, the absorbance of the solution was found

to decrease with time. As for ホカロン being the adsorbent, adsorption was generally

more effective when the mixture was allowed to stand for a longer period of time.

However, the percentage decrease in absorbance remained unchanged after 5 hours.

P. 38

Part III Investigating the effectiveness of metal ions adsorption

on various adsorbents

The adsorption abilities of HFO on different metal ions is investigated. At an oxide

surface such as HFO, a surface functional group is typically represented as an amphoteric

hydroxyl group (e.g. =FeOH, =FeO-, =FeOH2

+). An electrostatic attraction arises from

the development of surface charge.

Zinc ions can be removed by HFO adsorption according to this equation.

>FeOH + Zn2+

(aq) → FeOZn+ + H

+(aq)

Copper(II) ions, nickel(II) ions and lead(II) ions are removed by HFO adsorption

according to this equation, similar to zinc ions reaction with HFO.

>FeOH + Cu2+

(aq) → FeOCu+ + H

+(aq)

>FeOH + Ni2+

(aq) → FeONi+ + H

+(aq)

>FeOH +Pb2+

(aq) → FeOPb+ + H

+(aq)

These ions can also be removed by displacement reaction when reacting with iron:

Fe + Cu2+

→ Fe2+

+ Cu

Fe+ Ni2+

→ Fe2+

+ Ni

Fe+ Pb2+

→ Fe2+

+ Pb

Activated carbon can also adsorb some of the metal ions since activated carbon has high

surface area. Individual particles are convoluted and display various kinds of porosity.

These micropores allow adsorption to occur, since adsorbing material can interact with

many surfaces simultaneously.

P. 39

Part IIIA Determination of Zn2+

adsorption by complexometric

titration

Objective:

To determine the effectiveness of Zn2+


complexometric titration.

Principle:

Complexometric titration can be carried out to determine any change in the concentration

of Zn2+

in a given solution. Any decrease in the volume of burette solution

(ethylenediaminetetraacetic acid, also known as EDTA solution) used to reach the end

point would indicate that some Zn2+

has been adsorbed by the adsorbents.

To find out the adsorption effect of various adsorbents on Zn2+

, equal mass of each

adsorbent is allowed to stand for several hours in standard zinc sulphate solution. The

mixtures are then filtered to remove the adsorbents. Eriochrome Black T, which acts as an

indicator for the end point of the reaction, and buffer solution (pH 10), which regulates

the pH of the solution in the conical flask during the titration, is added to the diluted

filtrate in the conical flask. The standard ZnSO4 is treated similarly and is titrated against

EDTA along with the filtrate solutions, such that the volume of EDTA required for

complete reaction with the other solutions can be compared with it to determine whether

adsorption of zinc ions by the adsorbents have taken place. The reaction taking place was:

Zn2+

+ EDTA4-

→ ZnEDTA2-

wine red blue

Colour changes from wine red to light blue at the end point.

Chemicals used:

Various Adsorbents

0.01M ZnSO4 (aq)

0.01M EDTA solution

P. 40

pH10 NH3/ NH4Cl buffer solution

Eriochrome Black T

Deionized water

Apparatus used:

Glassware

Electronic balance

Procedures:

1. 25.0 cm3 of 0.01M ZnSO4 (aq) was added to a

250 cm3 volumetric flask with a pipette.

Deionized water was added up to the graduation

mark. 250.0 cm3 of 0.001M ZnSO4 (aq) was

obtained.

2. 50.0 cm3 of 0.01M EDTA solution was added to

a 250 cm3 volumetric flask with a pipette.

Deionized water was added up to the graduation

mark. 250.0 cm3 of 0.002M EDTA solution was

obtained.

3. 25.0 cm3 of 0.01M ZnSO4 (aq) was added to 0.5

g of each adsorbent and the mixture was allowed

to stand for 9 hours.

4. The mixture was filtered. The obtained filtrate

was made up to 250.0 cm3 in a 250 cm

3 volumetric

flask.

5. 25.0 cm3 of the diluted filtrate was added to a

clean conical flask with a pipette.

6. 4.0 cm3 of pH10 NH3/NH4Cl buffer solution was

added to the conical flask, followed by the addition of

0.1g Eriochrome Black T.

P. 41

7. The diluted filtrate was titrated against 0.002M EDTA solution. The end point was

reached when the colour of the filtrate changed from wine red to light blue.

8. 0.001M ZnSO4 (control) was also titrated against 0.002M EDTA solution.

Results:

1. HFO (NaOH, pH5)

Titration 1 Titration 2 Titration 3

Final Reading (cm3) 31.80 31.40 27.70

Initial reading (cm3) 4.90 4.30 0.90

Titre (cm3) 26.90 27.10 26.80

Mean titre (cm3) 26.93

2. HFO (NaOH, pH7)


Final Reading (cm3) 21.20 22.80 20.70


Titre (cm3) 18.40 18.50 18.50


3. HFO (NaOH, pH9)


Final Reading (cm3) 19.90 21.70 18.70


Titre (cm3) 16.20 16.20 16.10


P. 42

4. HWP (白元)


Final Reading (cm3) 25.10 25.10 47.90


Titre (cm3) 22.00 22.10 22.10


5. Iron fillings


Final Reading (cm3) 22.50 21.40 25.70


Titre (cm3) 20.70 20.65 20.70


6. Iron(III) oxide


Final Reading (cm3) 33.00 29.60 32.70


Titre (cm3) 26.60 26.60 26.50


7. Activated carbon


Final Reading (cm3) 28.00 28.90 27.80


Titre (cm3) 26.60 26.50 26.50


8. Vermiculite + activated carbon


Final Reading (cm3) 30.50 35.00 29.00


Titre (cm3) 25.40 25.50 25.60


9. A2 – Processed HWP (dil. HCl + 4hr)


Final Reading (cm3) 28.80 27.10 39.70


Titre (cm3) 25.00 25.10 25.20


P. 43

10. B2 – Processed HWP (dil. HCl + 4hr + heat)


Final Reading (cm3) 28.60 26.80 31.05


Titre (cm3) 26.20 26.20 26.30


11. C2 – Processed HWP (conc. HCl + 4hr)


Final Reading (cm3) 27.10 32.90 37.30


Titre (cm3) 26.00 26.00 25.90


12. HWP (ドうくん)


Final Reading (cm3) 20.25 38.00 20.70


Titre (cm3) 17.60 17.70 17.80


13. HWP (Warmergotchi)


Final Reading (cm3) 38.25 19.15 36.75


Titre (cm3) 17.50 17.65 17.60


14. HWP (Pocket Sun)


Final Reading (cm3) 17.10 32.85 18.55


Titre (cm3) 15.70 15.75 15.75


15. HWP (ホカロン)


Final Reading (cm3) 41.00 24.20 23.95


Titre (cm3) 22.4 22.4 22.45


P. 44

12. Control


Final Reading (cm3) 29.20 28.00 30.60


Titre (cm3) 27.10 27.00 27.05


Discussion:

Combining the experimental results, we made the following ranking on the effectiveness

of Zn2+

adsorption on various adsorbents.

Rank No. Adsorbent Mean

Titre

(cm3)

% Change in

Mean Titre (#)

1. 14. HWP ( Pocket Sun) 15.74 -41.8%

2. 1. HFO (NaOH, pH 9) 16.167 -40.2%

3. 13. HWP ( Warmergotchi) 17.58 -35.0%

4. 12. HWP (ドうくん) 17.69 -34.6%

5. 2. HFO (NaOH, pH 7) 18.467 -31.7%

6. 3. Iron filings 20.68 -23.5%

7. 4. Hand warmer powder (白元) 22.07 -18.4%

8. 15. HWP (ホカロフ) 22.42 -17.1%

9. 5. A2 - Processed HWP (dil. HCl + 4 hr) 25.10 -7.21%

10. 6. Vermiculite + activated carbon 25.53 -5.62%

11. 7. C2 - Processed HWP (conc. HCl + 4 hr) 25.96 -4.03%

12. 8. B2 - Processed HWP (dil. HCl + 4 hr +

heat)

26.23 -3.03%

13. 9. Activated carbon 26.53 -1.92%

14. 10. Iron(III) oxide powder 26.56 -1.81%

15. 11. HFO (NaOH, pH 5) 26.93 -0.44%

16. 16. Control 27.05 /

(#) =

x 100% mean titre of zinc solution after treatment – mean titre of control

mean titre of control

P. 45

From the above table and graph, we can see that the untreated hand warmer powder

(Pocket Sun) gave the best result in adsorbing Zn2+

ions among all adsorbents, which was

even better than the results of the HFOs. Two other hand warmer powders were also

relatively effective in adsorbing Zn2+

ions as they reduced the amount of ions by around

35%, while HFO at pH9 reduced it by around 40%. Among the HFOs produced, HFO

(NaOH, pH 9) and HFO (NaOH, pH 7) had the best two effects in adsorbing Zn2+

ions.

Conversely, the HFO produced in acidic medium had extremely poor adsorption effects.

It was also found that the untreated hand warmer powder had better adsorption effects

than the treated ones. As for the components of the hand warmer powders, they had worse

adsorption effects than most of the original hand warmer powders, showing that the

original hand warmer powders which contain different components were more suitable

for adsorbing Zn2+

ions.

The best adsorbent for Zn2+

P. 46

Part IIIB Determination of Cu2+

and Ni2+

adsorption by

colorimetric measurement

Objective:

To determine the effectiveness of Cu2+

and Ni2+


colorimetric measurement and the time effect on the adsorption abilities.

Principle:

To find out the reduction on copper(II) ions or nickel(II) ions by the various adsorbents, a

known volume of standard copper(II) sulphate solution or nickel(II) chloride solution is

added to the adsorbents and filtered. The filtrate is then treated with an excess of ethane-1,

2-diamine so that all the Cu2+

(aq) or Ni2+

(aq) can be converted to their corresponding

purple complex ions.

Cu2+

(aq) + 2H2NCH2CH2NH2 [Cu(H2NCH2CH2NH2)2]2+

(aq)

pale blue purple

Ni2+

(aq) + 3H2NCH2CH2NH2 [Ni(H2NCH2CH2NH2)3]2+

(aq)

green violet

The intensity of the purple colour produced is proportional to the amount of

copper(II) ions or nickel(II) ions present, and the absorbance can be

measured using a colorimeter. The colorimeter readings are compared with

that of the original solutions treated with ethane-1, 2-diamine, which act as

the control, to see if any copper(II) ions or nickel(II) ions have been

adsorbed.

To investigate the effect of time on Cu2+

adsorption of a particular adsorbent,

the time period for the adsorbent being in contact with dichromate solution is

varied and the absorbance values are compared.

Chemicals used:

0.1M ethane-1,2-diamine

0.01M CuSO4 (aq)

P. 47

0.01M NiSO4

Various adsorbents

Apparatus used:

Glassware

Electronic balance

Colorimeter

Procedures:

1. 25.0 cm3 of 0.01M CuSO4 (aq) was added to 0.5 g of

each adsorbent and the mixtures were allowed to stand

for 9 hours. In addition to this, solution samples

containing HFO at pH 9 and ホカロフ hand warmer

powder were allowed to stand for 1, 3, 5 and 7 hours

respectively.

2. The mixtures were filtered. 5.0 cm3 of each obtained

filtrate was mixed with 5.0 cm3 of 0.1M

ethane-1,2-diamine.

The mixtures were poured into test tubes respectively to obtain their absorbance in a

colorimeter.

3. Steps 1-3 were repeated with 0.01M NiSO4 and all mixtures were allowed to stand for

9 hours only.

P. 48

Results:

Copper adsorption:

Colorimetric measurement

0.01M Cu2+

0.01M Ni2+

Adsorbent absorbance absorbance

1. HFO (NaOH, pH 5) 0.37 0.05

2. HFO (NaOH, pH 7) 0.15 0.005

3. HFO (NaOH, pH 9) 0.07 0.035

4. Hand warmer powder (白元) 0.32 0.045

5. Iron filings 0.28 0.05

6. Iron(III) oxide powder 0.38 0.037

7. Activated carbon 0.22 0.04

8. Vermiculite + activated carbon 0.35 0.035

9. A2 - Processed HWP (dil HCl + 4 hr) 0.38 0.04

10. B2 - Processed HWP (dil HCl + 4 hr + heat) 0.37 0.044

11. C2 - Processed HWP (conc HCl + 4 hr) 0.36 0.05

12. Hand warmer powder (ドうくん) 0.39 0.055

13. Hand warmer powder (Warmergotchi) 0.34 0.048

14. Hand warmer powder (Pocket Sun) 0.20 0.044

15. Hand warmer powder (ホカロン) 0.23 0.023

16. Control 0.425 0.06


Nickel solutions after adsorption

HFO (NaOH, pH 5), HFO (NaOH, pH 7), HFO (NaOH, pH 9), HWP (白

元), Iron filings, Iron(III) oxide powder, Activated carbon, Vermiculite +

activated carbon, A2, B2, C2, Control

P. 49

Time effect on copper adsorption:

Duration Cu

2+

+ HFO (pH 9)

% Change in

Absorbance

Cu2+

+ HWP (ホカロン)

% Change in

Absorbance

Control 0.38 / 0.38 /

1 hr 0.24 -36.8 0.34 -10.5

3 hr 0.19 -50.0 0.20 -47.4

5 hr 0.16 -57.9 0.17 -55.3

7 hr 0.14 -63.2 0.14 -63.2

Control HFO pH7 (1 hr→3hrs→5hrs→7hrs) HWP ホカロン(1 hr→3hrs→5hrs→7hrs)

P. 50

Discussion:

Copper adsorption:

Based on the experimental results, we made the following ranking on the effectiveness of

Cu2+

adsorption on various adsorbents.

Colorimetric Measurement

0.01M Cu2+

Rank No. Adsorbent Absorbance % Change in

Absorbance

(#)

1. 2. HFO (NaOH, pH 9) 0.07 -83.5

2. 3. HFO (NaOH, pH 7) 0.15 -64.7

3. 14. Hand warmer powder (Pocket Sun) 0.2 -52.9

4. 7. Activated carbon 0.22 -48.2

5. 15. Hand warmer powder (ホカロン) 0.23 -45.9

6. 5. Iron filings 0.28 -34.1

7. 4. Hand warmer powder (白元) 0.32 -24.7

8. 13. Hand warmer powder (Warmergotchi) 0.34 -20

9. 8. Vermiculite + activated carbon 0.35 -17.6

10. 11. C2 - Processed HWP

(conc HCl + 4 hr)

0.36 -15.3

11. 10. B2 - Processed HWP

(dil HCl + 4 hr + heat)

0.37 -12.9

1. HFO (NaOH, pH 5) 0.37 -12.9

12. 6. Iron(III) oxide powder 0.38 -10.6

9. A2 - Processed HWP

(dil HCl + 4 hr)

0.38 -10.6

13. 12. Hand warmer powder (ドうくん) 0.39 -8.2

16. 16. Control 0.425 /

(#) = absorbance of copper solution after treatment – absorbance of control

absorbance of control (From left to right)

HFO (NaOH, pH 5), HFO

(NaOH, pH 7), HFO (NaOH,

pH 9), Hand warmer powder

(白元), Iron filings, Iron(III)

oxide powder, Activated

carbon, Vermiculite +

activated carbon, A2, B2, C2,

Control

x 100%

P. 51

HFO at pH9 and HFO at pH7 were the best two adsorbents of Cu2+

ions among all

adsorbents while the effectiveness of HFO at pH5 was still far lower than that of HFO at

pH9 and HFO at pH7. As for the untreated hand warmer powders, although they were not

as effective as HFO at pH9 and HFO at pH7, two of them led to reduction in absorbance

by over 45%, showing that they can also be used to adsorb Cu2+

ions.

Most of the untreated hand warmer powder had better adsorption effects than the treated

ones. Also, the hand warmer powder named Pocket Sun had better adsorption effects than

the separate components of hand warmer powder.


HFO (NaOH, pH 5), HFO (NaOH, pH 7), HFO (NaOH, pH 9), Hand warmer powder (白

元), Iron filings, Iron(III) oxide powder, Activated carbon, Vermiculite + activated carbon,

A2, B2, C2, Control

HWP ドうくん,

HWP Pocket Sun,

HWP Warmergotchi,

HWP ホカロン

HWP ドうくん,

HWP Pocket Sun,

HWP Warmergotchi,

HWP ホカロン

P. 52

Time effect on copper adsorption:

Concerning the optimum length of time for the immersion of absorbents in Cu2+

solution,

with HFO at pH9 as the adsorbent, the percentage decrease in absorbance was found to

increase with time. As for ホカロン being the adsorbent, adsorption was more effective

when the mixture was allowed to stand for a longer period of time. In short, the

percentage decrease in absorbance was found to increase with time for both adsorbents,

HFO at pH9 and ホカロン.

P. 53

For the effectiveness of Ni2+

adsorption on various adsorbents, the ranking is as follows:

Colorimetric Measurement

0.01M Ni2+

Rank No. Adsorbent Absorbance % Change in

Absorbance (#)

1. 2. HFO (NaOH, pH 7) 0.005 -91.7

2. 15. Hand warmer powder (ホカロン) 0.023 -61.7

3. 3. HFO (NaOH, pH 9) 0.035 -41.7

8. Vermiculite + activated carbon 0.035 -41.7


5. 7. Activated carbon 0.04 -33.3

9. A2 - Processed HWP

(dil HCl + 4 hr)

0.04 -33.3

6. 10. B2 - Processed HWP

(dil HCl + 4 hr + heat)

0.044 -26.7


4. Hand warmer powder (白元) 0.045 -25.0

8. 13. Hand warmer powder

(Warmergotchi)

0.048 -20

9. 1. HFO (NaOH, pH 5) 0.05 -16.7

5. Iron filings 0.05 -16.7

11. C2 - Processed HWP

(conc HCl + 4 hr)

0.05 -16.7

10. 12. Hand warmer powder (ドうくん) 0.055 -8.33

11. 16. Control 0.13 /

(#) = absorbance of nickel solution after treatment – absorbance of control

absorbance of control


HFO (NaOH, pH 5), HFO

(NaOH, pH 7), HFO

(NaOH, pH 9), Hand

warmer powder ( 白元 ),

Iron filings, Iron(III) oxide

powder, Activated carbon,

Vermiculite + activated

carbon, A2, B2, C2,

Control

x 100%

P. 54

The experimental results showed HFO at pH7 was the best adsorbent in adsorbing Ni2+

ions, followed by the untreated hand warmer powder ホカロン being the second best

adsorbent. The untreated hand warmer powder ホカロン led to a reduction of 61.7% in

absorbance, showing that it had better adsorption effects than HFO at pH9, components

of hand warmer powders and the treated hand warmer powders.

In adsorbing Ni2+

ions, two of the treated hand warmer powders (treated with dilute

hydrochloric acid for 4 hours, with and without heat) and three of the separate

components of hand warmer powders (vermiculite, activated carbon and iron(III) oxide

powder) performed better than some of the untreated hand warmer powder. Nevertheless,

it is important to note that the untreated hand warmer ホカロン is still quite effective in

adsorbing Ni2+

ions and can therefore be used to adsorb Ni2+

ions.


HFO (NaOH, pH 5), HFO (NaOH, pH 7), HFO (NaOH, pH 9), Hand warmer powder (白元), Iron filings, Iron(III) oxide powder, Activated

carbon, Vermiculite + activated carbon, A2, B2, C2, Control, HWP ドうくん, HWP Pocket Sun, HWP Warmergotchi, HWP ホカロン

P. 55

Part IIIC Determination of Pb2+

adsorption by gravimetric

analysis through precipitation

Objective:

To determine the effectiveness of Pb2+

adsorption on various adsorbents by gravimetric

analysis through precipitation.

Principle:

To find out the reduction of Pb2+

by the various adsorbents, a known volume of Pb2+

solution is added to the adsorbents and filtered, same volume of an excess of potassium

iodide is added to the filtrate and yellow precipitates is formed.

Pb2+

(aq) + 2I(aq) PbI2(s)

colourless bright yellow ppt

The mixture is then filtered again to obtain the precipitates. The precipitates are washed,

dried and weighed. The mass of the precipitates is proportional to the number of moles of

Pb2+

present, lead(II) ions have been successfully adsorbed by the adsorbents if the mass

of the lead(II) iodide of a particular sample is lower than that of the control.

P. 56

Chemicals used:

Various adsorbents

0.01M Pb(NO3)2

0.2M KI

Apparatus used:

Glassware

Electronic balance

Stopwatches

Procedures:

1. 0.5 g of various adsorbents were added to 25.0 cm3 of

0.01 M Pb(NO3)2 and were allowed to stand for 9 hours.

2. 10 cm3 of 0.2M KI (in excess) was added to the filtrate

to precipitate out all the PbI2(s).

3. The mass of each dry filter paper was measured.

The mixture was filtered and the total mass of the filter

paper and the precipitate was measured after the filter

paper was dried.

4. The mass of precipitate was calculated.

Mass of precipitate (g) =

Total mass of filter paper and precipitate – Mass of each

dry filter paper

P. 57

Results:

Gravimetric analysis

0.01M Pb2+

Adsorbent Mass of precipitate (g)

1. HFO (NaOH, pH 5) 0.10

2. HFO (NaOH, pH 7) 0.12(*)

3. HFO (NaOH, pH 9) 0.10

4. Hand warmer powder (白元) 0.09

5. Iron filings 0.03

6. Iron(III) oxide powder 0.11

7. Activated carbon 0.10

8. Vermiculite + activated carbon 0.10

9. A2 - Processed HWP (dil HCl + 4 hr) 0.10

10. B2 - Processed HWP (dil HCl + 4 hr + heat) 0.11

11. C2 - Processed HWP (conc HCl + 4 hr) 0.10

12. Hand warmer powder (ドうくん) 0.12 (*)

13. Hand warmer powder (Warmergotchi) 0.10

14. Hand warmer powder (Pocket Sun) 0.11

15. Hand warmer powder (ホカロン) 0.10

16. Control 0.12

(*) The colour of the precipitate was not bright yellow, implying that the precipitate

may contain other compounds and so the mass of precipitate was greater than the

control.


Control, HFO (NaOH, pH 5), HFO (NaOH, pH 7),

HFO (NaOH, pH 9)

Hand warmer powder (白元),A2, B2, C2

Activated carbon, Vermiculite + activated carbon,

Iron filings, Iron(III) oxide powder

HWP ドうくん, HWP Pocket Sun, HWP ホカ

ロフ, HWP Warmergotchi

P. 58

Discussion:

The effectiveness of Pb2+

adsorption on various adsorbents were compared and the

ranking is as follows:

Gravimetric Analysis

0.01M Pb2+

Rank No. Adsorbent Mass of

Precipitate (g)

% Change in Mass

of Precipitate (#)

1. 5. Iron filings 0.03 -75

2. 4. Hand warmer powder (白元) 0.09 -25

3. 1. HFO (NaOH, pH 5) 0.10 - 16.7

3. HFO (NaOH, pH 9) 0.10 - 16.7

7. Vermiculite + activated carbon 0.10 - 16.7

8. Activated carbon 0.10 - 16.7

9. A2 - Processed HWP (dil HCl + 4 hr) 0.10 - 16.7

11. C2 - Processed HWP (conc HCl + 4 hr) 0.10 - 16.7

13. Hand warmer powder (Warmergotchi) 0.10 - 16.7

15. Hand warmer powder (ホカロン) 0.10 - 16.7



10. B2 - Processed HWP (dil HCl + 4 hr +

heat)

0.11 -8.3

6. 12. Hand warmer powder (ドうくん) 0.12 0

2. HFO (NaOH, pH 7) 0.12(*) 0

7. 16. Control 0.12 /

(*) The colour of the precipitate was not bright yellow, implying that the precipitate may

contain other compounds and so the mass of precipitate was greater than the control.

(#) = mass of precipitate from lead(II) solution after treatment – mass of precipitate from control

mass of precipitate from control

adsorbance of control


HFO (NaOH, pH 5), HFO (NaOH, pH 7), HFO (NaOH, pH 9), Hand warmer powder (白元), Iron filings,

Iron(III) oxide powder, Activated carbon, Vermiculite + activated carbon, A2, B2, C2, Control

x 100%

P. 59

In the case of adsorption of Pb2+

ions, iron filings was the best adsorbent since iron metal

effectively precipitates Pb2+

ions from its aqueous solution. The second best adsorbent,

untreated hand warmer powder (白元) had better adsorption effects than the HFOs and

the treated hand warmer powders. Some other used hand warmer powders like

Warmergotchi and ホカロン had similar adsorption effects as HFO at pH 5 and 9 and

components of used hand warmer powders like vermiculite and activated carbon. In short,

to adsorb Pb2+

ions, iron filings and the hand warmer powder (白元) are preferred to be

used.

P. 60

Combining results from part IIIA, IIIB and IIIC, we can see that among the HFOs

prepared, HFO(NaOH, pH 7) and HFO(NaOH, pH 9) were the two adsorbents with the

best effects in adsorbing Zn2+

, Cu2+

and Ni2+

ions. However, we noticed that another type

of HFO – HFO(NaOH, pH 5) had relatively

poor effectiveness in adsorbing Zn2+

and Cu2+

ions as compared to the other two HFOs. It was

especially poor in adsorbing Zn2+

ions and

could only reduce the amount of Zn2+

ions by

0.444%. This implies that the pH value of HFO

affects its effectiveness in adsorbing metal ions.

For instance, HFO produced in a neutral or

alkaline medium better adsorbs Zn2+

, Cu2+

and

Ni2+

ions.

Nevertheless, the effectiveness of Pb2+

adsorption on different HFOs was quite different

from that of Zn2+

, Cu2+

and Ni2+

adsorption. The

effectiveness of Pb2+

adsorption on HFO(NaOH,

pH 7) and HFO(NaOH, pH 9) was significantly

lower than that of Zn2+

, Cu2+

and Ni2+

ions

adsorption on them while the effectiveness of

Pb2+

adsorption on HFO(NaOH, pH 5) was still

quite low.

In short, among the three types of HFOs, HFO(NaOH, pH 9) was found to be the most

suitable in adsorbing Zn2+

and Cu2+

ions while HFO(NaOH, pH 7) was found to be the

most suitable in adsorbing Ni2+

ions. As for the adsorption of Pb2+

ions, considering the

fact that the amount of yield of HFO(NaOH, pH 9) during production was greater than

that of HFO(NaOH, pH 5), it was found to be the most appropriate in adsorbing Pb2+

ions.

The effectiveness of metal ions

adsorption on hand warmer powders was

another main focus of this part. It was

found that some used hand warmer

powder had similar or even better

adsorption effects than the HFOs in

P. 61

adsorbing metal ions. For example, in adsorbing Zn2+

ions, the hand warmer powder

(Pocket Sun) reduced the amount of ions by 41.8%, which was greater then the

percentage reduced by the HFOs. Therefore, the hand warmer powders are also effective

in adsorbing metal ions and may even have better adsorption effects than the HFOs.

Having known that hand warmer powders are effective in adsorbing metal ions, we

looked into whether treated or untreated hand warmer powders had better adsorption

effects. It was found that untreated hand warmer powders were generally more effective

in adsorbing Zn2+

and Cu2+

ions. For the adsorption of Ni2+

ions, the hand warmer

powder ホカロン reduced the amount of ions by 61.7% while the treated hand warmer

powders reduced the amount of ions by 25% on average only. While for the adsorption of

Pb2+

ions, the hand warmer powder (白元) performed better than the treated ones while

other hand warmer powders had similar adsorption effects as the treated ones. Therefore,

as most untreated hand warmer powders were more effective than the treated ones or had

similar adsorption effects as the treated ones, the untreated hand warmer powders are

more suitable for adsorbing metal ions so as to save resources for treating them.

P. 62

As the hand warmer powder is composed of

different substances, the adsorption effects of

these substances were investigated too to see

whether these separate pure components of hand

warmer powder adsorb better than the original

hand warmer powder. From the experimental

results, we noticed that for the five brands of hand

warmer powders investigated, most of them had

better or similar adsorption effects than their

components. For instance, 3 brands of hand

warmer powders investigated performed better

than their components in adsorbing Zn2+

ions.

This showed that the adsorption of metal ions

with the original hand warmer powders is

preferred to with the components of hand warmer

powders. Hence, costs and resources of separating

the components of used hand warmer powders

can be saved when preparing adsorbents for metal

ions adsorption.

P. 63

From all the results above, it was shown that

some of the used untreated hand warmer

powders were even more effective in

adsorbing metal ions than the HFOs. Thus, it

is a good idea to make use of used hand

warmer powders to remove pollutants from

industrial wastewater in order to conserve our

environment. This is because there is no cost

in using the used hand warmer powders

which are considered as waste and the used

hand warmer powders are not difficult to

obtain. Also, by using used hand warmer powders to remove pollutants in wastewater, the

volume of solid waste can be reduced which in turn reduce the pressure on the already

over-burdened landfills.

In order to put this environmentally-friendly idea into

practice, collection bins of used hand warmer powders

can be set up in various places, for instance, MTR

stations and lobbies of residential buildings so the

collected powders can be transported to different

sewage treatment station to remove pollutants from

wastewater.

P. 64

Part IIID Determination of hardness adsorption by EDTA

titration

Objective:

To investigate the adsorption ability of used hand warmer powder to remove hardness of

water.

Principle:

Natural mineral water contains calcium and magnesium ions, resulting in hardness of

water which brings about inconvenience in domestic water usage as well as

environmental problems. In this part, we investigated the ability of used hand warmer

powder to adsorb calcium and magnesium ions in both laboratory solutions and in

commercial mineral water. In order to determine the amount of calcium and magnesium

ions present, titration of the solution against a standard solution of

ethylenediaminetetraacetic acid (EDTA) can be carried out in alkaline medium based on

complexation reactions. Calcium and magnesium ions can be removed by adsorption

according to these equations.

>FeOH + Ca2+

(aq) → FeOCa+ + H

+(aq)

>FeOH + Mg2+

(aq) → FeOMg+ + H

+(aq)

In experiment A, the Ca2+

and Mg2+

adsorption ability of various adsorbents will be

investigated using laboratory reagents. Various adsorbents will be stood for several hours

in standard calcium and magnesium solutions respectively. Titration against EDTA

solution will be carried out to determine the concentration of calcium and magnesium

ions after treatment. Control experiments will be carried out for comparison of results. As

calcium ions, magnesium ions, calcium-EDTA complex and magnesium-EDTA complex

are colourless, a suitable indicator that will change colour at the equivalence point has to

be used. Eriochrome Black T. is chosen as the indicator, in which end point is reached

when the wine red colour changes into a blue colour in high pH. A buffer of

ammonium-ammonia at pH 10 will be added to maintain a steady pH value.

Ca2+

+ EDTA4-

→ CaEDTA2-

wine red blue

Mg2+

+ EDTA4-

→ MgEDTA2-

wine red blue

P. 65

In experiment B, the Ca2+

and Mg2+

adsorption ability of different brands of used hand

warmer powder will be investigated using a commercial brand of mineral water. Same

masses of used hand warmer powder will be stood in a fixed volume of mineral water for

several hours. Titration against EDTA solution will then be carried out as in experiment

A to determine the metal concentrations after the treatment.

Mineral water contains other metal ions apart from

calcium and magnesium. Since EDTA solution reacts

directly with many metal ions, the presence of other

metal ions in mineral water may interfere with the

result. The metal cations present in the commercial

brands of mineral water which are in relatively

significant amounts are Ca2+

, Mg2+

, Na+ and K

+. The

alkali metals, sodium and potassium, do not react with

EDTA solution thus their presence can be ignored.

Other metal ions would be precipitated out under high

pH and are not complexed by EDTA, thus their

presence can also be ignored. A control of unadsorbed

mineral water will be titrated as well for comparison. A

smaller volume of EDTA solution used for titration of

filtrates than the control would mean that there is a

reduction in calcium and magnesium ions after adsorption, thereby indicating that used

hand warmer powder is effective in removing hardness of water.

Chemicals used:

Various Adsorbents

0.01M CaCl2 (aq)

0.01M Mg(NO3)2 (aq)

0.01M EDTA solution

“No Frills” bottled mineral water

pH10 NH3/ NH4Cl buffer solution

Eriochrome Black T

Deionized water

P. 66

Apparatus used:

Glassware

Electronic balance

Procedures:

Experiment A

1. 25.0 cm3 of 0.01M CaCl2 (aq) was added to a 250 cm

3 volumetric flask with a pipette.

Deionized water was added up to the graduation mark. 250.0 cm3 of 0.001M CaCl2

(aq) was obtained.

2. 50.0 cm3 of 0.01M EDTA solution was added to a 250 cm

3 volumetric flask with a

pipette. Deionized water was added up to the graduation mark. 250.0 cm3 of 0.002M

EDTA solution was obtained.

3. 25.0 cm3 of 0.01M CaCl2 (aq) was added to 0.5 g of

each adsorbent and the mixture was allowed to stand for 9

hours.

4. The mixture was filtered. The obtained filtrate was made

up to 250.0 cm3 in a 250 cm

3 volumetric flask.

5. 25.0 cm3 of the diluted filtrate was added to a clean conical

flask with a pipette.

6. 4.0 cm3 of pH10 NH3/NH4Cl buffer solution was added to

the conical flask, followed by the addition of 0.1g

Eriochrome Black T.

P. 67


reached when the colour of the filtrate changed from wine red to blue.

8. 0.001M CaCl2 (aq) (control) was also titrated against 0.002M EDTA solution.

9. The above procedures were repeated using Mg(NO3)2 (aq) instead of CaCl2 (aq)

Experiment B

1. 1.0 g of each brand of used hand warmer powder was weighed

separately.

2. 50.0cm3

of “No Frills” mineral water was pipetted into each

sample of used hand warmer powder.

3. The mixture was left to stand for three and a half hours.

4. The mixture was filtered. The obtained filtrate was made up to

250.00 cm3 in a 250 cm

3 volumetric flask.

5. 25.0 cm3 of the diluted filtrate was added to a clean conical

flask with a pipette.

6. 4.0 cm3 of pH10 NH3/NH4Cl buffer solution was added to the

conical flask, followed by the addition of 0.1g Eriochrome

Black T.


reached when the colour of the filtrate changed from wine red to blue.

8. 50.0 cm3

of “No Frills” mineral water was pipetted into a 250cm3

volumetric flask and

made up to 250.0cm3 as the control.

9. 25.0 cm3

of the control solution was also titrated against 0.002M EDTA solution.

P. 68

Results:

Calcium ion adsorption titrations:

1. HFO pH 5


Final reading (cm3) 24.10 44.20 26.50


Titre (cm3) 20.30 20.10 20.20


2. HFO pH 7


Final reading (cm3) 27.10 24.60 28.20


Titre (cm3) 20.60 20.50 20.70


3. HFO pH9


Final reading (cm3) 33.10 17.00 31.20


Titre (cm3) 14.10 14.30 14.20


4. HWP (白元)


Final reading (cm3) 25.40 23.15 23.60


Titre (cm3) 18.30 18.45 18.30


5. Iron filings


Final reading (cm3) 21.60 25.65 35.10


Titre (cm3) 19.20 19.05 19.10


P. 69

6. Iron(III) oxide


Final reading (cm3) 25.50 23.90 21.75


Titre (cm3) 19.80 20.00 20.00


7. Activated carbon


Final reading (cm3) 24.40 25.60 21.10


Titre (cm3) 19.90 20.00 20.00


8. Vermiculite + Activated carbon


Final reading (cm3) 20.20 20.80 39.70


Titre (cm3) 19.00 19.10 18.90


9. A2


Final reading (cm3) 25.40 44.50 19.40


Titre (cm3) 19.05 19.10 18.90


10. B2


Final reading (cm3) 44.30 26.00 27.70


Titre (cm3) 18.40 18.50 18.60


11. C2


Final reading (cm3) 25.40 44.90 25.40


Titre (cm3) 19.30 19.50 19.30


P. 70



Final reading (cm3) 22.40 23.00 23.80


Titre (cm3) 19.80 19.60 19.60


13. HWP (WarmerGotchi)


Final reading (cm3) 21.40 19.70 37.60


Titre (cm3) 18.10 18.00 17.90


14. HWP (Pocket Sun)


Final reading (cm3) 18.60 35.40 20.80


Titre (cm3) 16.90 16.80 17.00


15. HWP (ホカロフ)


Final reading (cm3) 25.90 28.70 39.40


Titre (cm3) 18.60 18.70 18.70


16. Control


Final reading (cm3) 23.00 22.30 41.90


Titre (cm3) 19.80 19.70 19.60


P. 71

Magnesium adsorption titrations:

1. HFO pH5


Final reading (cm3) 28.50 25.20 36.30


Titre (cm3) 23.40 23.20 23.40


2. HFO pH7


Final reading (cm3) 26.50 24.70 24.70


Titre (cm3) 24.20 24.05 24.20


3. HFO pH9


Final reading (cm3) 26.00 49.60 26.40


Titre (cm3) 25.00 24.90 24.80


4. Iron(III) oxide


Final reading (cm3) 24.40 25.60 47.00


Titre (cm3) 24.20 24.10 24.30


5. Activated carbon


Final reading (cm3) 39.30 35.50 35.90


Titre (cm3) 35.00 34.90 34.80


P. 72

6. Vermiculite + activated carbon


Final reading (cm3) 24.30 26.40 25.40


Titre (cm3) 23.70 23.50 23.60


7. A2


Final reading (cm3) 23.30 25.10 23.90


Titre (cm3) 22.10 22.05 22.10


8. B2


Final reading (cm3) 23.00 26.10 40.20


Titre (cm3) 22.15 22.20 21.90


9. C2


Final reading (cm3) 25.20 25.45 25.70


Titre (cm3) 23.85 24.05 23.90


10. Control


Final reading (cm3) 26.00 25.80 49.20


Titre (cm3) 25.30 25.10 25.00


P. 73

Mineral water hardness adsorption titrations:

1. HWP (白元)


1 2 3 4

Final burette reading (cm3) 12.15 19.60 26.90 24.40

Initial burette reading (cm3) 4.55 12.25 19.60 27.00

Titre (cm3) 7.60 7.35 7.30 7.40


3. HWP (Warmergotchi)

1 2 3

Final burette reading (cm3) 14.50 21.05 27.50

Initial burette reading (cm3) 7.85 14.50 21.05

Titre (cm3) 6.65 6.55 6.45


4. HWP (Pocket Sun)

1 2 3 4

Final burette reading (cm3) 7.45 11.90 16.50 20.90

Initial burette reading (cm3) 2.20 7.40 12.20 16.55

Titre (cm3) 5.25 4.50 4.30 4.35


5. HWP (ホカロン)

1 2 3



Titre (cm3) 8.60 8.50 8.50


6. HWP (Control)

1 2 3



Titre (cm3) 10.50 10.50 10.40


1 2 3



Titre (cm3) 8.60 8.50 8.60


P. 74

Discussion:

Effectiveness of Ca2+

adsorption:

From the above graph, it can be seen that most the mean titre for most adsorbents were

lower than that of control, indicating that there was a decrease in calcium content. Among

the different brands of used hand warmer powder, Pocket Sun has the best adsorption

effect while ドうくん has the poorest adsorption effect.

0

5

10

15

20

25

Mea

n t

itre

(c

m3)

Adsorbents

Mean Titre of Calcium Solutions after Treatment

Rank No. Adsorbent Mean Titre

(cm3)

% Change in

Mean Titre (#)

1. 3 HFO (NaOH, pH 9) 14.20 -27.9%

2. 14 HWP ( Pocket Sun) 16.90 -14.2%

3. 13 HWP ( Warmergotchi) 18.00 -8.6%

4. 4 Hand warmer powder (白元) 18.35 -6.9%

5. 10 B2 – Processed HWP (dil. HCl + 4 hr + heat) 18.50 -6.1%

6. 15 HWP (ホカロフ) 18.67 -5.2%

7. 8 Vermiculite + activated carbon 19.00 -3.6%

8. 9 A2 – Processed HWP (dil. HCl + 4 hr) 19.02 -3.5%

9. 5 Iron filings 19.12 -2.9%

10. 11 C2 – Processed HWP (conc. HCl + 4 hr) 19.37 -1.7%

11. 12 HWP (ドうくん) 19.67 -0.15%

12. 6 Iron(III) oxide powder (*suspension observed) 19.93 +1.2%

13. 7 Activated carbon 19.97 +1.4%

14. 1 HFO (NaOH, pH 5) 20.20 +2.5%

15. 2 HFO (NaOH, pH 7) 20.60 +4.6%

16. 16. Control 19.70 /

(#) =

x 100% mean titre of calcium solution after treatment – mean titre of control


P. 75

Certain data obtained were found to be unusual, i.e. the mean titre obtained was even

higher than that of the control, which should not be the case because the concentration of

calcium ions should not be higher than that of the original solution it started with. To

explain this result, we hypothesized that some of the iron present in HFO may have

somehow dissolved into the calcium solution to form iron ions. Since EDTA reacts with

iron ions, the volume of EDTA solution used would be greater than that of calcium ions

alone.

Another possible explanation is due to experimental errors.

Effectiveness of Mg2+

adsorption:

0

5

10

15

20

25

HFO (NaOH,

pH 5)

HFO (NaOH,

pH 7)

HFO (NaOH,

pH9)

Control

Mea

n T

itre

(cm

3)

Adsorbents

Mean Titre of Calcium Solutions after

Treatment of HFOs

Rank No. Adsorbent Mean Titre

(cm3)

% Change in

Mean Titre (#)

1. 9 A2 – Processed HWP (dil. HCl + 4 hr) 22.08 -12.13%

2. 10 B2 – Processed HWP (dil. HCl + 4 hr + heat) 22.08 -12.13%

3. 1 HFO (NaOH, pH 5) 23.33 -7.16%

4. 8 Vermiculite + activated carbon 23.60 -6.09%

5. 11 C2 – Processed HWP (conc. HCl + 4 hr) 23.93 -4.78%

6. 2 HFO (NaOH, pH 7) 24.15 -3.90%

7. 6 Iron(III) oxide powder 24.20 -3.70%

8. 3 HFO (NaOH, pH 9) 24.90 -0.92%

9. 7 Activated carbon 34.90 +38.88%

10. 12. Control 25.13 /

(#) =

x 100% mean titre of magnesium solution after treatment – mean titre of control


P. 76

From the above graph, we can see that processed hand warmer powder (dil. HCl + 4 hr)

and processed hand warmer powder (dil. HCl + 4 hr + heat) had the best two effects in

adsorbing Mg2+

ions among all adsorbents. However, a complete comparison among all

adsorbents was not possible since upon adding buffer solution of pH 10 to magnesium

solution treated by untreated used hand warmer powder, brown precipitate was observed.

Upon adding indicator, colour of solution turns brownish red instead of the usual wine

red, and upon adding EDTA solution, the solution turned light brown, the end point

cannot be easily detected. Thus, the Mg2+

adsorption ability of used hand warmer powder

was unable to be investigated.

Although experimental results were not able to be obtained, we are still able to deduce

the Mg2+

adsorption ability based on available data. With the exception of activated

carbon (in which the results were unusual for both calcium and magnesium), all other

data attained in the magnesium experiment showed positive adsorption results. After

comparison with the adsorption results of the same adsorbents in the calcium experiment,

it can be deduced that used hand warmer powder can adsorb magnesium ions as well,

because all the hand warmer powder were effective in adsorbing calcium ions.

0

5

10

15

20

25

30

35

40

HFO

(NaOH, pH 5)

HFO

(NaOH, pH 7)

HFO

(NaOH, pH9)

Iron(III)

oxide powder

Activated

carbon

Vermiculite

+ activated carbon

A2 -

Processed HWP (dil.

HCl + 4 hr)

B2 -

Processed HWP (dil.

HCl + 4 hr +

heat)

C2 -

Processed HWP (conc.

HCl + 4 hr)

Control

Mea

n T

itre

(cm

3)

Adsorbents

Mean Titre of Magnesium Solutions after Treatment

P. 77

Effectiveness of hardness adsorption from mineral water:

To confirm our conclusion drawn from experiment A which used laboratory reagents,

mineral water was also adsorbed. Results show that all brands of used hand warmer

powder investigated have positive adsorption results. Pocket Sun has the best adsorption

effect, which is consistent with experiment A.

Since EDTA solution reacts with both calcium and magnesium ions, the mean titre

obtained is a reflection of the overall sum of calcium and magnesium ions that have been

adsorbed. Thus, it is not possible to determine the actual decrease in concentration of the

respective two metal ions. Nonetheless, it can be concluded that there is a reduction in the

amount of calcium and magnesium ions after adsorption by used hand warmer powder.

Thus, used hand warmer powder is effective in removing hardness of water.

P. 78

Part IVA Investigating the effectiveness of filtration device

and the regeneration of HFO in the device

Objective:

To determine the effectiveness of toxic ions removal by hand warmer powder-packed

column.

Principles:

To find out the effectiveness of toxic ions removal by hand warmer powder-packed

column, a known volume of phosphate, dichromate, copper(II), zinc, lead(II) and

nickel(II) ion solutions are allowed to pass through the Warmergotchi-packed columns.

After washing the columns several times by deionized water, the amount of the remaining

anions / metal cations in the resulting solutions can be determined by gravimetric

measurement. For phosphate and dichromate, an excess of aqueous lead(II) nitrate is

added to the solutions in order to precipitate out any remained phosphate and chromate

ions as insoluble lead(II) phosphate and lead(II) chromate.

Pb2+

(aq) + PO43-

(aq)→ Pb3(PO4)2 (s)

Pb2+

(aq) + CrO42-

(aq) →PbCrO4 (s)

For metal cations, an excess of aqueous sodium carbonate is added to precipitate out any

remained metal ions as insoluble metal carbonates.

M2+

(aq) + CO32-

(aq) →MCO3 (s)

The precipitates are washed, dried and weighed. The mass of the precipitates is

proportional to the number of moles of phosphate or dichromate or metal ions unadsorbed,

if the ions have been successfully adsorbed by the Warmergotchi-packed column, the

mass of the precipitates would be lower than that of the control.

The reaction for the adsorption of cations by hydrous ferric oxide is as follows:

>FeOH + M2+

(aq) → FeOM+ + H

+(aq)

In order to regenerate hydrous ferric oxide, dilute sulphuric acid should be added to the

adsorbents to reverse the reaction.

P. 79

Chemicals used:

0.01M PbNO3 (aq), NiSO4 (aq), ZnSO4 (aq), K2Cr2O7 (aq), CuSO4 (aq), Na3PO4 (aq)

Hand warmer powder (Warmergotchi)

1M Na2CO3 (aq)

0.5M Pb(NO3)2 (aq)

Apparatus used:

Electronic balance

Glass wear

Procedures:

1. 15g of untreated used “Warmergotchi” hand warmer powder

was packed in each of six burettes as shown.

2. 25 cm3

of each ion solution was pipetted and allowed to run

through the packed hand warmer powder column for adsorption.

P. 80

3. The columns were washed for three times with 25 cm3 of deionised water each time.

4. The filtrate collected was treated with 0.5M Pb(NO3)2(aq) and 1M Na2CO3(aq)

respectively. The precipitates obtained were filtered under suction, washed and dried

in an oven.

5. The mass of the precipitate was weighed and compared with that generated from the

control solution.

Precipitates

formed by

lead(II) control

Precipitates

formed by treated

lead(II) solution

Precipitates

formed by zinc

control

Precipitates

formed by treated

zinc solution

Phosphate solution Dichromate solution

Metal ions solution

Precipitates

formed by

copper(II) control

Precipitates

formed by

nickel(II) control

Precipitates formed by

treated nickel(II) solution

Precipitates

formed by treated

nickel(II) solution

Precipitates formed

by treated

copper(II) solution

Precipitates formed

by dichromate

control

Precipitates formed

by treated

dichromate solution

Precipitates

formed by

phosphate control

Precipitates formed

by treated

phosphate solution

P. 81

Results:

Mass of precipitates formed by

control solution

Mass of precipitates formed by

solution treated by Warmergotchi

Lead(II) phosphate 1.89g 1.44g

Copper(II) carbonate 0.34g 0g

Zinc carbonate 0.30g 0.22g

Lead(II) carbonate 0.70g 0g

Nickel(II) carbonate 0.29g 0.02g

Lead(II) chromate 2.09g 1.20g

Discussion:

From the above table and graph, it can be shown that the Warmergotchi-packed column is

extremely effective in adsorbing different ions. Despite the success of adsorbing different

ions from solutions, it took a long time for some solutions, phosphate solution in

particular, to pass through the Warmergotchi-packed column, resulting in the formation of

iron ions precipitates which came from iron ions washed down from the Warmergotchi

column for treated phosphate, zinc and lead(II) ions solution.

P. 82

However, some solutions, such as copper(II) solution and nickel(II) solution took a

relatively shorter time to pass through the Warmergotchi-packed column. Nickel (II) and

copper(II) solution were therefore used for the second part of the experiment.

Separate nickel(II) solution was treated by the same Warmergotchi-packed column for

three times, the resulting mass of nickel(II) carbonate formed by reacting the filtrate with

sodium carbonate solution is as follows.

1st round 2

nd round 3

rd round Control

Mass 0.02g 0.18g 0.21g 0.29g

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

1st round 2nd round 3rd round Control

Mas

s

Mass of nickel(II) carbonate after different rounds of treatment

P. 83

Separate copper(II) solution was treated by another Warmergotchi-packed column for

three times, the resulting mass of copper(II) carbonate formed by reacting the filtrate with

sodium carbonate solution is as follows.

1st round 2

nd round 3

rd round Control

Mass 0g 0.2g 0.23g 0.34g

The results for both copper(II) and nickel(II) solutions show an increasing mass of

precipitates formed with increasing number of treatment using the same

Warmergotchi-packed column. This shows that the Warmergotchi-packed column

becomes less effective with increasing number of treatments.

1st round 2

nd round

3rd

round

Ni2

+

1st round 2

nd round

3rd

round Cu2+

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

1st round 2nd round 3rd round Control

Mas

s

Mass of copper(II) carbonate after different rounds of treatment

P. 84

Our group tried to regenerate the Warmergotchi-packed

column by adding dilute sulphuric acid to it. Copper(II)

solution was then added to the column. The resulting

solution showed a lighter blue colour than that of the

control solution, indicating that the regeneration was

successful.

Lighter

Cu2+

solution

treated by

regenerated

column

Control

Control

P. 85

Part IVB Comparing the effectiveness of burette columns and

compartmentalized container as filtration device

Objectives:

To compare the effectiveness of toxic ions removal by hand warmer powder-packed

column with that of a compartmentalized filtration device.

Principles:

To compare the effectiveness of ions adsorption by hand warmer powder packed in a

column or a compartmentalized filtration device, a known volume of a mixture of cations

solutions are allowed to pass through the Warmergotchi placed in the two devices. After

washing the columns several times by deionized water, the amount of the remaining

metal cations in the resulting solutions can be determined by gravimetric measurement.

An excess of aqueous sodium carbonate is added to precipitate out any remained metal

ions as insoluble metal carbonates.

M2+

(aq) + CO32-

(aq) →MCO3 (s)

The precipitates are washed, dried and weighed. The mass of the precipitates formed after

passing through the burette and the device are compared to see which is more effective.

Chemicals used:

0.05M NiNO3(aq), ZnNO3(aq), CuNO3(aq)

Hand warmer powder (Warmergotchi)

1M Na2CO3(aq)

Apparatus used:

Electronic balance

Glasswear

NiNO3 ZnNO3 CuNO3

P. 86

Procedures:

1. 50g of untreated used „Warmergotchi‟ hand warmer powder was packed into a burette

and filtration device.

2. 50cm3 of the cations mixture was allowed to run through the packed hand warmer

powder, another 100cm3

of it was allowed to run through the filtration device.

3. The column and the device was washed for three times with 25cm3 of deionized water

each time.

4. The filtrate collected was treated with 1M Na2CO3 (aq), the precipitates obtained

were filtered under suction, washed and dried in an oven.

5. The mass of the precipitate was weighed and compared with that generated from the

control solution.

6. The percentage change in mass for the burette and the filtration device was compared.

Results:

Device used Mass of precipitates

formed by control

solution

Mass of precipitates

formed by treated

solution

Percentage

change in mass

Burette column 0.86 0.04 -95.3%

Filtration device 2.76 2.58 -6%

Precipitates formed by cations

mixture treated by burette

column


cations mixture control




mixture treated by burette

column




mixture treated by

compartmentalized filtration

device

P. 87

Discussion: In view of the long time taken for most

solutions to run through the entire burette,

another device was used for adsorbing

pollutants. Warmergotchi hand warmer powder

was placed in the device, and a mixture of

cations solution was poured into the device.

The cations solution contains nickel(II) nitrate

solution, copper(II) nitrate solution and zinc

nitrate solution. This is to test the

Warmergotchi-packed device‟s ability to

remove heavy metal ions. However, lead(II)

ions is not included in the solution because

upon adding lead(II) nitrate solution to the mixture, white precipitates are formed.

This may be due to impurities like SO42

or Cl present in nickel(II) nitrate, copper(II)

nitrate or zinc nitrate which form precipitate with the lead(II) ion.

The same cation solution

was added to another

burette packed with the

same mass of Warmergotchi

as the one in the device

mentioned above. Separate

cations solution was treated by

the same Warmergotchi-packed

column to see the whether the

column is still effective after

being used once.

The results show that the burette column is much more effective than the filtration device.

Despite the long time required for solution to pass through the burette column, the

increased contact time of pollutants with the adsorbents prove to be very effective in

removing the pollutants. Hence the burette column is a much better device for treating

water.

Control

Cations mixture

solution treated by

Warmergotchi

column for the 1st

round

Cations mixture

solution treated by the

same Warmergotchi

column for the 2nd

round

P. 88

Comparisons between different adsorbents

Adsorbents PO43

Cr2O72

Zn2+

Cu2+

Ni2+

Pb2+

Ca2+

Mg2+

Overall

score

HFO (NaOH,

pH 5)

☆☆☆☆☆ ☆☆☆☆☆ ☆ ☆☆ ☆ ☆☆ / ☆☆☆☆ 2.5

HFO (NaOH,

pH 7)

☆☆☆☆☆ ☆☆☆☆☆ ☆☆☆☆☆ ☆☆☆☆ ☆☆☆☆☆ / / ☆☆☆ 3.38

HFO (NaOH,

pH 9)

☆☆☆ ☆☆☆☆☆ ☆☆☆☆☆ ☆☆☆☆☆ ☆☆☆ ☆☆ ☆☆☆☆☆ ☆ 3.63

白元 (original) ☆☆ ☆☆☆ ☆☆☆☆ ☆☆☆ ☆☆ ☆☆ ☆☆☆ / 2.38

Iron filings ☆ / ☆☆☆☆ ☆☆☆ ☆ ☆☆☆☆☆ ☆☆ / 2

Iron(III) oxide

powder

☆ ☆☆ ☆ ☆☆ ☆☆☆ ☆ / ☆☆☆ 1.63

Activated

carbon

☆ ☆☆☆☆ ☆ ☆☆☆☆ ☆☆ ☆☆ / / 1.75

Vermiculite +

Activated

carbon

☆☆☆ ☆☆☆ ☆☆ ☆☆ ☆☆☆ ☆☆ ☆☆ ☆☆☆☆ 2.63

Processed hand

warmer powder

(dil. HCl + 4

hr)

☆☆☆☆ ☆☆ ☆☆ ☆☆ ☆☆ / ☆☆ ☆☆☆☆☆ 2.38

Processed hand

warmer powder

(dil. HCl + 4 hr

+ heat)

☆ ☆☆ ☆☆ ☆☆ ☆☆ ☆ ☆☆☆ ☆☆☆☆☆ 2.25

Processed hand

warmer powder

(conc. HCl + 4

hr)

☆☆☆ ☆☆ ☆☆ ☆☆ ☆ ☆☆ ☆☆ ☆☆☆ 2.13

HWP (original,

ドうくん)

☆☆☆☆ ☆☆☆☆ ☆☆☆☆☆ ☆ ☆☆☆☆ / ☆ / 2.38

HWP (original,

Warmergotchi)

☆☆☆☆ ☆☆☆ ☆☆☆☆☆ ☆☆ ☆☆☆☆☆ ☆☆ ☆☆☆☆ / 3.13

HWP (original,

Pocket Sun)

☆☆ ☆☆☆ ☆☆☆☆☆ ☆☆☆☆ ☆☆ ☆ ☆☆☆☆ / 2.63

HWP (original,

ホカロフ)

☆☆☆ ☆☆☆☆ ☆☆☆☆ ☆☆☆☆ ☆☆☆☆ ☆☆ ☆ / 2.75

Key:

☆☆☆☆☆: Lowest absorbance/ smallest mass of precipitates formed/ smallest titre

(Lowest concentration of an adsorbate)

☆: Highest absorbance/ smallest mass of precipitates formed/ smallest titre (Highest

concentration of an adsorbate)

/: Poor results (i.e. absorbance close to or higher than that of control; titre close to or greater

than that of control; mass of precipitates close to or greater than that of control)

P. 89

From the table above, it can be seen that HFO (NaOH, pH 9) is the most effective

adsorbent, while HFO (NaOH, pH 7) is the second most effective adsorbent. ホカロン,

Pocket Sun and mixture of vermiculite and activated carbon are also effective adsorbents.

The worst adsorbent is iron(III) oxide powder, followed by activated carbon. Iron filings,

processed hand warmer powder (conc. HCl + 4 hr) and processed hand warmer powder

(dil. HCl + 4 hr + heat) also perform poorly.

Although hand warmer powders do not perform as well as HFO, considering the fact that

used hand warmer powder shows good adsorption ability for phosphate ions, and also

ranks quite high among all the adsorbents used, with ホカロン at 3rd

place and Pocket

Sun at 4th

place, it is still useful to use used hand warmer powder to adsorb pollutants

from wastewater. This is particularly true because HFO, the most effective adsorbent, is

very time consuming to produce, whereas hand warmer powder is a domestic waste that

can be obtained easily. Moreover, hand warmer powder can be used to adsorb pollutants

directly since generally speaking, treated hand warmer powders do not perform better

than untreated ones.

P. 90

Sources of Error

Part IA: Preparation of hydrous ferric oxide (HFO)

1. The adjustment of pH value during the preparation of HFO may not be accurate

due to discrepancies in determining the colour of pH paper.

2. The addition of hydrochloric acid to adjust the pH of the supernatant liquid may

interfere with the formation of hydrous ferrous oxide.

3. There is mass loss during the transfer of hydrous ferrous oxide from filter papers

onto watch glasses for drying in the oven.

4. There is mass loss during the transfer of dried, grinded ferrous oxide from mortar

to watch glass for weighing.

Part IB: Preparation of Processed Hand Warmer Powder (HWP)

1. Although the hand warmer powder used in all four treatments is of the same brand,

the composition in different packets may be different, resulting in an unfair test.

2. There is mass loss during the transfer of processed hand warmer powder from

filter papers onto watch glasses for drying in the oven.

3. It is difficult to judge the proportion of iron and iron(III) ions present in the

mixture by just looking at the colour of the solution, so our deductions about the

composition in the various processed hand warmer powder may not be true.

4. There may be other substances present in the used hand warmer powder, apart

from those that we deduced, which may or may not affect the overall adsorption

ability of processed hand warmer powder.

Parts II: Investigating the effectiveness of anion adsorption on various adsorbents

1. The markings of the colorimeter were not fine enough that discrepancies among

the readings could not be observed or determined accurately.

2. Suspension was observed in some adsorbent samples and thus some colorimeter

readings were affected and could not reflect the actual situation.

3. The samples with phosphate or dichromate solution were allowed to stand for 9

hours without intermittent or continuous stirring. This may affect the adsorption

performance.

P. 91

Part III: Investigating the effectiveness of cation adsorption on various adsorbents

1. The end point of titration in Part IIIA was difficult

to detect and different people might have different

sensitivity to the end point.

2. In part IIIB, suspension was formed so the reading

from the colorimeter might not be accurate.

3. In Part IIIC, ions other than Pb2+

might be

precipitated out which contribute to the mass of

precipitate.

4. In Part IIID, the treated mineral water and the

EDTA solution were both diluted 5 times before

titration, any small amount of addition or loss of

mineral water or solution during handling of

chemicals would lead to a relatively high percentage of experimental error.

5. There may be impurities present in the solution which maybe react with EDTA

solution, resulting in an inaccurate determination of results in Part IIID.

Part IV: Investigating the effectiveness of filtration device and the regeneration of HFO

in the device

1. PO43-

, Cr2O72-

and metal ions solution took a long time to pass through the burette

columns, allowing iron compounds from the burette column to be dissolved in the

ions solution, resulting in the formation of brown precipitates after treatment of

the solution by the Warmergotchi column.

2. PO43-

, Cr2O72-

and metal ions cannot be completely washed out of the

Warmergotchi powder by 3 rounds of deionized water, particularly for the

compartmentalized device since deionized water used to wash the powder would

pass through the Warmergotchi powder much quicker than in the burette columns,

this result in an increase of the mass of the precipitates formed at the end of the

experiments.

P. 92

Suggestions for Improvements

Part IA: Preparation of hydrous ferric oxide (HFO)

1. Measure the pH of the supernatant using a pH meter.

2. Add sodium hydroxide solution slowly and gradually to prevent overshooting of

pH value of the supernatant liquid.

3. Instead of transferring the hydrous ferrous oxide from filter papers to watch

glasses, place the filter papers which hold wet hydrous ferrous oxide after

filtration into the oven for drying directly. The mass of dried hydrous ferric oxide

can be determined by the subtraction of the mass of the piece of filter paper which

has been initially weighed from the total mass of the filter paper and its contents

after drying.

4. After drying in the oven, obtain the mass of the dried hydrous ferrous oxide

before grinding by subtracting the mass of the watch glass from the total mass of

watch glass and its contents.

Part IB: Preparation of Processed Hand Warmer Powder (HWP)

1. Mix all the packets of the used hand warmer powder of the same brand together

and take out samples for treatments from this large batch, so as to ensure more

similar compositions for each sample.

2. Instead of transferring the processed hand warmer powder from filter papers to

watch glasses, place the filter papers which hold powder after filtration into the

oven for drying directly. The mass of dried powder can be determined by the

subtraction of the mass of the piece of filter paper which has been initially

weighed from the total mass of the filter paper and its contents after drying.

3. More conditions for treatments can be conducted on the used hand warmer

powder, such as using acid concentrations in between 2M and 11M or adopting

time lengths in between 2, 4 and 6 hours. Comparisons can be made easier and

more reliable to obtain more accurate deductions about the compositions of the

processed hand warmer powder.

Parts II: Investigating the effectiveness of anion adsorption on various adsorbents

1. Use a colorimeter with finer markings.

2. Use filter paper with finer pores when filtering the adsorbents.

3. Stir the mixtures at intervals evenly throughout the standing process.

P. 93

Part III: Investigating the effectiveness of cation adsorption on various adsorbents

1. Assign one person to carry out all titrations in order to reduce the errors caused by

human factors.

2. Instead of doing gravimetric analysis through precipitation in Part IIIC, use

another determination method to cross check the results.

3. A higher concentration of EDTA could be used to reduce the percentage error.

Another improvement is to perform the titrations for a larger number of times

such that a more reliable result can be obtained.

Part IV: Investigating the effectiveness of filtration device and the regeneration of HFO

in the device

1. Insert cotton wool intermittently between Warmergotchi powder in a burette

column to relieve the pressure from the lower part of the burette column,

resulting in a quicker flow of the ions solution, reducing the formation of brown

precipitates due to presence of iron ions.

2. Increase the number of washings to be carried out after each round.

P. 94

Conclusion

Part I: Preparation of various adsorbents

To create the adsorbents necessary to remove pollutants from water, our group has

chosen to synthesize hydrous ferric oxide from chemicals available in the laboratory

since according to other research, HFO is a successful adsorbent for many pollutants and

may also resemble the composition of hand warmer powder. Our group has also chosen a

second approach towards creating an adsorbent: To use used hand warmer powder to

adsorb pollutants, such that these materials can be recycled and used for water treatment.

In synthesizing HFO, it was noted that a supernatant liquid of pH 7 creates the most

amount of precipitates. A supernatant liquid of pH 5 creates precipitates that are too small,

though the surface area of the precipitates must be significantly greater, it is difficult to

collect. It was also noted that sodium hydroxide is a better solution to use than ammonia

solution since using sodium hydroxide solution would produce more precipitates.

Hand warmer powder was also used to adsorb pollutants. By using different treatments,

we were able to deduce roughly the composition of the hand warmer powder, and we

could use the treated hand warmer powder to carry out further experiments to test which

treatment produces the best adsorbents. Although the hand warmer powder may exhibit

weaker adsorption abilities, hand warmer powder is a domestic waste, and by putting the

used powder into good use, the powder will not be wasted and this is environmentally

friendly.

Part II: Investigating the effectiveness of PO43

and Cr2O72

adsorption on various

adsorbents

For PO43

adsorption, HFO (NH3, pH 7) is the most effective while iron filings is the least

effective. Generally speaking, HFO formed are most effective in adsorbing PO43

ions,

and while the adsorption ability of processed hand warmer powder and unprocessed hand

warmer powder varied, they are still comparable to that of HFO.

Among the HFO samples, HFO produced in an alkaline medium shows better adsorption

effects of phosphate ions than that in acidic or neutral medium. However, the general

adsorption performance of HFO samples is still very satisfactory.

pH 5

(NaOH)

pH 5

(NaOH) pH 7

(NaOH)

pH 9

(NaOH)

pH 11

(NaOH)

pH 7

(NH3)

P. 95

Among the processed hand warmer powder samples, those treated with dilute HCl was

found to be very effective in adsorbing PO43

ions, with the PO43

concentration reduced

by more that 90%. It was also found that iron(III) oxide is more effective than iron in the

removal of phosphate ions.

Among all hand warmer powder brands, WarmerGotChi

hand warmer powder was found to be the most effective

phosphate adsorbent while the lowest effectiveness was

observed for Pocket Sun hand warmer powder.

For Cr2O72

ions, HFO produced in a neutral medium

was found to be the most effective in the removal of

dichromate while iron filings were shown to be the least

effective adsorbents. It was also found that vermiculite is

not effective or even hinders the removal of dichromate.

For HFO, the average adsorption power was the highest among all absorbents. Moreover,

HFO produced in neutral and alkaline mediums were found to have better adsorption

effects than that produced in an acidic medium.

For hand warmer powder, it was found out that the original hand warmer powder is more

effective than all treated samples. For optimized adsorption effects, untreated hand

warmer powder should be used.

Among all the brands, hand warmer powder of brand ホカロン was

shown to be the most effective dichromate adsorbent while the lowest

effectiveness was observed for Pocket Sun hand warmer powder.

Although the average dichromate adsorption power of HFO is the

highest, some used hand warmer powder samples are also very

effective in the removal of dichromate.

P. 96

Part III: Investigating the effectiveness of metal ions adsorption on various adsorbents

HFO produced in a neutral or alkaline medium adsorbs Zn2+

, Cu2+

and Ni2+

ions better

than that of HFO produced in an acidic medium. For Pb2+

ions, HFO produced in acidic

and alkaline medium perform better than that in neutral medium.

It was found that among the three types of HFOs, HFO(NaOH, pH 9) is the most suitable

in adsorbing Zn2+

and Cu2+

ions while HFO(NaOH, pH 7) is found to be the most suitable

in adsorbing Ni2+

ions. As for the adsorption of Pb2+

ions, taking into consideration of the

fact that the amount of yield of HFO(NaOH, pH 9) during production was greater than

that of HFO(NaOH, pH 5), and the production of HFO (NaOH, pH 9) was much was

easier than that of HFO (NaOH, pH 5), HFO (NaOH, pH 9) was taken to be the most

effective HFO in adsorbing Pb2+

ions.

As for used hand warmer powder, they are shown to be just as effective in adsorbing

metal ions as HFOs. It was also found that with the exception of Ni2+

, untreated hand

warmer powders were more effective in adsorbing metal ions than untreated ones,

For Zn2+

ions, the most effective adsorbent is Pocket Sun. For Cu2+

, it is HFO synthesized

at pH 9, followed by Pocket Sun. For Ni2+

, it is Warmergotchi. For Pb2+

ions, iron filings

were the best adsorbent, followed by the hand warmer powder 白元. The adsorption

effect of the hand warmer powder, with the exception of Pocket Sun and ドうくん, were

even better than that of the HFOs and it was found that untreated hand warmer powders

adsorbed Pb2+

ions better than the treated ones.

Considering the adsorption effects of all the ions tested, HFO (NaOH, pH 9) is the best

adsorbent, followed closely by HFO (NaOH, pH 7). The weakest adsorbent is iron(III)

oxide, followed by activated carbon and iron filings.

Although the used hand warmer powders are not among the best adsorbents, they were

proved to be quite effective, in particular Warmergotchi and ホカロン, of negligible cost

and are easily available. They could be potential adsorbents to treat industrial wastewater.

HFO (NaOH, pH9) HFO (NaOH, pH7)

P. 97

Experiments on Ca2+

and Mg2+

were also carried out to test the effectiveness of hardness

removal of different adsorbents. For Ca2+

, HFO synthesized at pH 9 was most effective,

followed by untreated Pocket Sun. For Mg2+

, hand warmer powders processed by dilute

HCl performed the best, followed by HFO synthesized at pH 5.

Part IV: Investigating the effectiveness of filtration devices and the regeneration of HFO

in the device

A filtration device was made by packing Warmergotchi powder into a burette column. It

was found that such device is extremely effective in removing pollutants since it allows a

large contact area and long contact time for the adsorption of different ions, PO43

solution, Cr2O72

solution and all the other metal ions solution passed through the column

all showed a significant decrease in the mass of precipitates formed upon adding lead(II)

nitrate solution and sodium carbonate solution compared with that of the control.

Though the effectiveness of the Warmergotchi-packed column decreases with the number

of times a solution has run through it, regeneration of its adsorption ability was found to

be possible by passing the used column with dilute sulphuric acid.

In view of the solutions taking a long time to pass through the burette columns, a

compartmentalized device was used to see if this could replace the very effective burette

columns. It was found that the reduction in heavy metal ions after being treated in the

new device is significantly lower than that of the burette columns, indicating that such

device is not as effective as the burette column.

Despite the long time it takes for the solution to pass through the burette column, it is still

better to use the burette column to ensure a greater removal of pollutants from effluents.

Cu2+

1st round

Cu2+

2nd round

Cu2+

3rd

round Cu2+

2nd

round

Cu2+

1st round

P. 98

References

Dwyer, Robert F.; Birdsall, Clair M. (1964) Process for the preparation of hydrous ferric

oxide. Union Carbide Corp.

Goswami, Saswati; Bhat, Subhas Chandra; Ghosh, Uday Chand. (2006) Crystalline

Hydrous Ferric Oxide: An Adsorbent for Chromium(VI)-Contaminated Industrial

Wastewater Treatment. Water Environment Research. Department of Chemistry,

Presidency College, West Bengal, Kolkata, India.

De Jager, Pieter Christiaan. (2002) A phosphate sorption and desorption study on an acid

sandy clay soil. Plant Production and Soil Science, University of Pretoria.

Kersten, Michael; Kulik, Dmitrii A. (2005) Competitive Scavenging of Trace Metals by

HFO and HMO during redox-driven Early Diagenesis of Ferromanganese Nodules.

Journal of Soils and Sediments. Geoscience Institute, Gutenberg-University, D-55099

Mainz, Germany; Waste Management Laboratory, Paul-Scherrer-Institute, CH-5232

Villigen-PSI, Switzerland.

Elimelech M;Borkovec M.; Hering J.. (1999) Interfacial and Colloidal Phenomena in

Aquatic Environments - Chemical Processes at the Solid-Water Interface. Preprints of

Extended Abstracts. Division of Environmental Chemistry, American Chemical Society

Lund, Tracy J; Koretsky, Carla M; Landry, Christopher J; Schaller, Melinda S; Das,

Soumya. 2008. Surface complexation modeling of Cu(II) adsorption on mixtures of

hydrous ferric oxide and kaolinite. Geochemical Transactions Journals. BioMed Central

Ltd.

http://chemlab.truman.edu/CHEM222manual/pdf/edta.pdf

http://en.wikipedia.org/wiki/Complexometric_titration

http://chemlab.truman.edu/CHEM222manual/pdf/edta.pdf

http://en.wikipedia.org/wiki/Complexometric_titration

12P

Documents

glassware electronic balance

hand warmer powders

hand warmer powder

11m hydrochloric acid

insoluble metal carbonates

2m hydrochloric acid

1g eriochrome black

hydrous ferrous oxide