Plasma activation of straw biochar and quantification of ...The Boehm titration method to identify acidic functional groups is mainly used because it is fast and inexpensive. However,

Hannah Rosenqvist 9th Lingfeng Summer Research School

Plasma activation of straw biochar

and quantification of surface

oxygen-containing functional groups

By

Hannah Rosenqvist

Supervisor: Jinjing Luo

Research Assistant: Shiqiang Sun

July 2015


Abstract

Biochar is a byproduct of biomass pyrolysis. Due to its low-cost production process and

environmental friendly material, biochar has the potential to replace more expensive synthesized

carbon materials. To be used as an adsorbent for pollutants, e.g. mercury gas in flue gas, biochar

requires proper activation. Conventional activation methods include baking at high temperatures and

chemical treatment. Those processes are not energy-effective and are also expensive and time

consuming.

This project investigated if plasma modification (21% O2, 79% N2) could sufficiently activate the

biochar. The plasma was produced at > 6 kV using a dielectric barrier discharge. The biochar was

treated for 0, 5, 15 and 30 minutes. The activation was analyzed by measuring the amount of surface

oxygen-containing functional groups by Boehm titration. Boehm titration was originally developed to

analyze activated carbon.

No trends could be seen in the resulting values for surface oxygen-containing functional groups

(SOFG) in the biochar at different activation times. A large part of the results showed negative values

of SOFG, which suggest that something has interfered with the samples from inside the biochar. Due

to time limitations not enough data was collected to produce a reliable foundation for analyzation.

Furthermore, the results hint that Boehm titration might not be a suitable method for biochar due to a

higher content of ash and DOC than activated carbon.

Keywords

Biochar, plasma, activation, adsorbent, Boehm titration,


Table of Contents

1. Introduction .......................................................................................................................... - 1 -

1.1. Objective........................................................................................................................ - 2 -

2. Background........................................................................................................................... - 3 -

2.1. Introduction to biochar .................................................................................................... - 3 -

2.2. Surface oxygen-containing functional groups and Boehm titration ..................................... - 3 -

2.3. Plasma modification of biochar ........................................................................................ - 4 -

3. Methodology......................................................................................................................... - 5 -

3.1. Experimental setup.......................................................................................................... - 5 -

3.2. Preparation of biochar and BPL activated carbon .............................................................. - 5 -

3.3. Base solutions and calibration .......................................................................................... - 5 -

3.4. Plasma treatment of biochar and BPL activated carbon ...................................................... - 6 -

3.5. Measurements of oxygen-containing functional groups by Boehm-titration......................... - 7 -

4. Results.................................................................................................................................. - 8 -

5. Analysis.............................................................................................................................. - 10 -

5.1. Limitations ................................................................................................................... - 10 -

5.2. Sources of error ............................................................................................................ - 10 -

6. Conclusion.......................................................................................................................... - 11 -

7. Acknowledgement............................................................................................................... - 11 -


- 1 -

1. Introduction Pollutants and contaminants in water, air and soil is a continuous environmental problem all over the

world. Ways to remove contaminants in a sustainable, yet cost-effective way is an important topic to

reduce the human impact on the environment.

Mercury is one example of a hazardous compound that we don’t want to emit into our atmosphere.

Usual sources of mercury pollution are coal combustion and waste incineration. Mercury is not easily

degraded and it accumulates in the ecosystem, making it more toxic for e.g. humans that are on top of

the food chain. It has been shown that activated carbon can successfully adsorb mercury gas, although

it is still an expensive method. Therefore biochar is investigated as a supplement for activated carbon

as a mercury adsorbent. (F., et al., 2011)

Biochar has a history of being used as soil amendment, soil remediation and carbon sequestration,

thanks to its pore structure and environmental-friendly nature. Biochar generally increases nutrient

availability, microbial activity, soil organic matter and water retention while decreasing its fertilizer

needs, greenhouse gas emissions and nutrient leaching (Mohan, et al., 2014). However, biochar might

have the right characteristics to be applicable in other fields as well, for example as an adsorbent for

pollutants. Presently, activated carbon is used as a pollutant remover and the similar characteristics

between biochar and activated carbon suggests that biochar could also be used for this purpose.

The advantage in using biochar would be that biochar is produced from natural and sustainable

sources, with no use of fossil fuels. The net carbon dioxide emission from biochar is considered zero

or negative due to the recycling of atmospheric CO2 through photosynthesis (Qian, et al., 2015).

Consequently, biochar would be a more sustainable and environmental-friendly option.

In order to use biochar as an adsorbent it must be activated. The activation aims to increase the

specific surface area (BET) and pore volume. Moreover the activation will increase the amount of

oxygen-containing functional groups on the surface of the biochar, which are important for adsorption

to occur. Common activation methods include high temperature treatment and chemical washing.

These methods are very time consuming and energy demanding. Accordingly, these methods are not

optimal from an economical point of view. However, an effective plasma treatment process could

produce a cost-efficient way of activating biochar. Previously studies show plasma treatment could be

used as a method to activate biochar (Gupta, 2015). This could make biochar available for additional

applications and for further purposes, such as a contaminant adsorbent. Moreover, the plasma

treatment process would be a more environmentally conscious method as it uses less energy and

chemical reagents.


- 2 -

This project is part of a larger project that mainly focuses on removing mercury from flue gas.

Therefore, the method used in this study, if found successful, would be investigated as a way to

remove mercury in flue gas.

1.1. Objective

The purpose of this project was to study if biochar can be used as a pollutant absorbent. Further, the

aim of this project was to observe and measure how the surface oxygen-containing functional groups

changes on the biochar when activated with plasma for different time intervals. The optimal activation

time was also investigated. Finally a comparison to plasma activation of activated carbon (BPL) was

made.


- 3 -

2. Background

2.1. Introduction to biochar

Biochar is a stable solid with high carbon content. It is produced through pyrolysis of biomass.

Pyrolysis means that the biomass is burned in absence of oxygen at a high temperature. The lack of

oxygen prevents combustion and produces a gas, liquid or charcoal. A byproduct from biofuel

production through pyrolysis is a fine-grained residue: biochar. The biochar yield can be controlled by

controlling the pyrolysis temperature. Raw material for biochar production can be biomass consisting

of e.g. crops, wood, manure or sewage (Manya, 2012).

Biochar has, in conformity with activated carbon, a very high surface area due to its porous structure.

Consequently, biochar can be used as an adsorbent for various pollutants. The pore size distribution

and specific surface area (BET) are important properties when using biochar as an adsorbent.

Generally, activated carbon has higher specific surface area than biochar. Some characteristics of the

biochar used in this study and an activated carbon sample are shown in table 1 (Huayi, 2014).

Table 1. Characteristics of biochar and activated carbon.

Material Carbonization

temperature

（℃）

BET

(m2

/g)

lactone groups

（mmol/g)

Phenol

groups

(mmol/g)

Carboxylic

groups

(mmol/g)

Straw

biochar 350 14.33 0.182 0.639 0.39

Activated

carbon 800 110.64 1.003 --- ---

2.2. Surface oxygen-containing functional groups and Boehm titration

Oxygen-containing functional groups (SOFG) on the biochar surface play a central role in the binding

of metal ions and other pollutants (Uchimiya, et al., 2011). Therefore it is of interest to obtain as high

amount of SOFGs as possible. Modifying biochar to attach specific SOFG can also result in specified

adsorption. Important SOFGs are e.g. carboxylic, lactone, phenolic and carbonyl groups. The chemical

structures of these functional groups are shown in figure 1. A larger amount of SOFGs result in

increased adsorption for activated carbon and chars in aqueous solutions (Uchimiya, et al., 2011).


- 4 -

The specific surface oxygen-containing functional groups can be measured from a Boehm titration

experiment based on the following theory: NaHCO3 neutralizes only carboxylic groups, while Na2CO3

titrates both carboxylic and lactone groups. In addition, NaOH reacts with carboxylic, lactone and

phenol groups (CONTESCU, et al., 1997). Finally, CH3CH2ONa neutralizes carboxylic, lactone,

phenol and carbonyl groups. The Boehm titration method to identify acidic functional groups is

mainly used because it is fast and inexpensive. However, the standardization for Boehm titration was

originally made for activated carbon and carbon black and it is still not certain if results of Boehm

titration used on biochar are justified (Fidel, et al., 2014). In this study it is assumed that the Boehm

titration can be used for biochar in the same way as for activated carbon.

2.3. Plasma modification of biochar

Plasma modification of biochar has been proven successful in previous studies (Gupta, 2015). To

produce the plasma a dielectric barrier discharge (DBD) is used. The DBD has proven to produce

negligible contaminants in a semiconductor dry etching process. Furthermore, oxygen plasma has been

shown to be very reactive to glassy carbon which is always found in biochar produced from biomass

pyrolysis. The DBD uses a high voltage to excite the gas in a vacuum chamber, in this case a quartz

tube. The electrons will interact with the gas inside the tube. Some of the interactions are ionization,

excitation and elastic scatterings of the gas. These reactions generate a high amount of reactive species

such as oxygen ions (O+) and excited oxygen atoms (O*) which will react with the biochar. (Gupta,

2015)

Carboxyl group Lactone groups Phenol group Carbonyl group

Figure 1. Chemical structure of four surface oxygen-containing functional groups.


- 5 -

3. Methodology

3.1. Experimental setup

All the chemicals and instruments used in this project were provided from Xiamen University,

Xiang’an Campus, College of Environment and Ecology.

3.2. Preparation of biochar and BPL activated carbon

The biochar used was made from straw and the carbonization temperature in the production was

350 ℃. The biochar was first grounded into a fine powder. However, the powder was blown out

during the plasma treatment so thereafter it was instead cut into small pieces. The BPL activated

carbon (BPL-AC) was also cut into small pieces. More than 5 g of the biochar was placed in a quartz

tube reactor under a N2 flow of 0.5 L/min for 20 min, then heated up to 700 ℃ in a heater at the rate of

10 ℃/min, to increase to pore volume and thereby the specific surface area (BET). In addition some of

the functional groups present originally on the carbon surfaces were removed by the heating. The

temperature program parameters for the biochar are listed in Table 2. The BPL-AC was heated to

1000 ℃.

Table 2. Temperature program parameters for preparation of biochar.

Step 1 2 3 4

Temp (°C) 20 700 700 20

Time (min) 20 120 30 -

3.3. Base solutions and calibration

Deionized water (Milli-Q® Integral Water Purification System) was boiled for 30 minutes in order to

remove CO2 from the water. Using the boiled water four solutions were prepared as can be seen in

table 3. A fifth solution, sodium ethoxide, was also prepared using ethanol as a solvent.

Table 3. Solutions and concentrations used for Boehm titration

Solution HCl NaOH NaHCO3 Na2CO3 CH3CH2ONa

Concentration

(mol/L) 0.1 0.05 0.05 0.05 0.05

The solutions were prepared according to table 3. The HCl and NaOH solutions were calibrated and

the concentrations were measured by titration as follows.

Calibration for NaOH solution


- 6 -

0.2 g potassium hydrogen phthalate (php) was dissolved in 20 mL of deionized water and 2 drops of

phenolphthalein was added as an indicator. The solution was titrated with the prepared NaOH solution

and the consumed volume was noted. The concentration of NaOH was then calculated according to

equation i, where mphp is the mass of php, 204.22 is the molar mass of php and VNaOH is the consumed

volume of NaOH from the titration.

i. 𝐶𝑁𝑎𝑂𝐻 =𝑚𝑝ℎ𝑝

204.22∗𝑉𝑁𝑎𝑂𝐻∗ 1000 (𝑚𝑜𝑙/𝐿)

Calibration for HCl solution

20.00 ml NaOH solution was pipetted with a few drops of bromocresol green and methyl red mixed

indicator. The NaOH solution was then titrated with the HCl solution. The consumption volume of the

HCl solution was recored and the concentration of HCl was calculated according to equation ii. CNaOH

is the concentration of NaOH from equation i, VNaOH is the volume of NaOH and VHCl is the consumed

volume of HCl.

ii. 𝑐𝐻𝐶𝑙 =𝑐𝑁𝑎𝑂𝐻∗𝑉𝑁𝑎𝑂𝐻

𝑉𝐻𝐶𝑙 (𝑚𝑜𝑙 /𝐿)

3.4. Plasma treatment of biochar and BPL activated carbon

In order to activate the biochar and BPL-AC, it was treated with plasma for different time intervals.

The activation times are shown in table 4. The plasma activation was performed using a dielectric

barrier discharge. The voltage used to discharge the gas was > 6kV. The gas used for the plasma was

21% O2 and 79% N2, to assimilate the atmosphere. After the activation, the biochar and BPL-AC was

washed with Milli-Q water to remove any contaminants that could be stuck in the pores.

Table 4. Activation times for plasma treatment of biochar and activated carbon.

Sample 1 2 3 4

Activation

time (min) 0 5 15 30

1 g of treated biochar (alt. BPL-AC) was added to 60 ml of each of the four solutions. The solutions

with biochar (alt. BPL-AC) were then placed in a shaker incubator at 25°C for 24 hours.


- 7 -

3.5. Measurements of oxygen-containing functional groups by Boehm-titration

After 24 hours the solutions were filtered with a 0.45 µm cellulose acetate membrane. Thereafter the

samples were transferred to Erlenmeyer flasks. For each sample two flasks containing 20 mL sample

each was used for the titration. Finally 0.1M HCl was used to titrate the samples. For the NaHCO3 and

Na2CO3 samples, N2 was bubbled for 10 minutes into the solutions after the titration. This was done in

order to remove CO2 that was formed during the titration, which would influence the pH. If needed,

the titration continued after the bubbling. The consumed volume of HCl was noted. The same titration

process was made with blank samples, which were not treated with biochar, to work as references.

The amount of surface oxygen-containing functional groups in each sample was calculated by

equation iii-vi. C is the content of oxygen-containing functional groups and 𝑑𝑖𝑓𝑓𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 is the

difference between the titrated consumption of HCl for the blank and the sample. CHCl is the

concentration of HCl and mAC is the amount of activated carbon/biochar in each sample. Since the

incubated samples are divided into thirds for the titration, mAC is also divided by three.

iii. 𝐶𝑐𝑎𝑟𝑏𝑜𝑥𝑦𝑙 =𝑑𝑖𝑓𝑓𝑁𝑎𝐻𝐶𝑂3∗3∗𝑐𝐻𝐶𝑙

𝑚𝐴𝐶∗100 (𝑚𝑚𝑜𝑙/100 𝑔 𝐴𝐶)

iv. 𝐶𝑙𝑎𝑐𝑡𝑜𝑛𝑒 =𝑑𝑖𝑓𝑓𝑁𝑎2𝐶𝑂3∗3∗𝑐𝐻𝐶𝑙

𝑚𝐴𝐶∗100− 𝑐𝑐𝑎𝑟𝑏𝑜𝑥𝑦𝑙 (𝑚𝑚𝑜𝑙/100 𝑔 𝐴𝐶)

v. 𝐶𝑝ℎ𝑒𝑛𝑜𝑙 =𝑑𝑖𝑓𝑓𝑁𝑎𝑂ℎ∗3∗𝑐𝐻𝐶𝑙

𝑚𝐴𝐶∗100− 𝑐𝑐𝑎𝑟𝑏𝑜𝑥𝑦𝑙 − 𝑐_𝑙𝑎𝑐𝑡𝑜𝑛𝑒 (𝑚𝑚𝑜𝑙/100 𝑔 𝐴𝐶)

vi. 𝐶𝑐𝑎𝑟𝑏𝑜𝑛𝑦𝑙 =𝑑𝑖𝑓𝑓𝐶 𝐻3𝐶𝐻2𝑂𝑁𝑎∗3∗𝑐𝐻𝐶𝑙

𝑚𝐴𝐶∗100− 𝑐𝑐𝑎𝑟𝑏𝑜𝑥𝑦𝑙 − 𝑐𝑙𝑎𝑐𝑡𝑜𝑛𝑒 − 𝑐𝑝ℎ𝑒𝑛𝑜𝑙 (𝑚𝑚𝑜𝑙/100 𝑔 𝐴𝐶)


- 8 -

4. Results

The raw data from the Boehm titration can be found in table A1-A3 in appendices. A summary of the

results from the titration with the calculated amounts of oxygen-containing functional groups are

shown in table 5. The results that show a negative value for the amount of functional groups are

marked in red. It seems that the carbonyl group was especially prone to produce negative values.

Negative values should not occur, since the biochar should take up some of the OH- in the base, and

therefore the biochar samples should show a lower consumption of HCl compared to the blank. In

other words, the results can only be negative if the difference between the blank and the sample is

negative, which theoretically should not occur.

Table 5. Amount of surface oxygen-containing functional groups (mmol/100 g activated carbon/biochar).

Biochar (granule particle) BC700-

P0

BC700-

P5 (1)

BC700-

P5 (2)

BC700-

P15

BC700-

P30 (1)

BC700-

P30 (2)

NaHCO3 Carboxyl

groups

-4,81 -5,91 7,14 5,92 1,77 8,57

Na2CO3 Hydroxyl

group

6,62 15,66 2,00 5,32 7,39 11,11

NaOH Phenol group 10,53 8,87 -3,43 21,60 9,16 -5,40

CH3CH2ON

a

Carbonyl

group

2,68 -8,58 -5,71 -9,49 -22,46 -13,71

Activated carbon (BPL) BPL (1) BPL (2) BPL-

1000 P0

BPL-1000

P5

BPL-1000

P15

BPL-

1000 P30

NaHCO3 Carboxyl

groups

7,09 5,61 -4,15 13,41 3,43 12,70

Na2CO3 Hydroxyl

group

4,72 2,65 18,92 1,43 13,75 6,20

NaOH Phenol group 6,26 10,97 7,14 13,70 11,63 11,31

CH3CH2ON

a

Carbonyl

group

37,89 39,86 10,28 20,65 20,43 15,95

Biochar (powder) BC700 BC700 BC700

NaHCO3 Carboxyl

groups

3,00 1,50 3,60

Na2CO3 Hydroxyl

group

-10,53 13,54 10,85

NaOH Phenol group 35,21 6,30 14,14

CH3CH2ON

a

Carbonyl

group

-15,94 9,98 -17,76

The amount of carboxyl, lactone, phenol and carbonyl groups in the granule biochar at different

activation times are shown in figure 2. No correlation between plasma activation time and the amount

of functional groups could be observed. Furthermore, since many of the resulting values are negative,

no conclusions can be made from the data. The data is very unreliable and should not be analyzed.


- 9 -

Figure 2. Amount of surface oxygen-containing functional groups on biochar (granule particle).

The amount surface oxygen-containing functional groups in the BPL activated carbon at different

activation times are shown in figure 3. There does not seem to be any correlations between the

activation time and the amount of functional groups for the BPL-AC either. For the BPL-AC there was

only one negative value, which could have been a mistake, and that sample is not included in figure 3.

However, from the other samples, it is impossible to see any trends.

Figure 3. Amount of surface oxygen-containing functional groups on activated carbon (BPL).

-0,25

-0,20

-0,15

-0,10

-0,05

0,00

0,05

0,10

0,15

0,20

0,25m

mo

l/g

bio

char

Carboxyl groups

Lactone group

Phenol group

Carbonyl group

0,00

0,05

0,10

0,15

0,20

0,25

0,30

0,35

0,40

0,45

mm

ol/

g B

PL-

AC

Carboxyl groups

Lactone group

Phenol group

Carbonyl group


- 10 -

5. Analysis

The results are impossible to analyze since many of the calculated values of the functional groups are

negative. Negative values mean that there were more negative ions in the biochar samples than in the

blank, which theoretically should not be possible, if the biochar does not add any ions. The carbonyl

groups seemed most prone to produce negative values. This could indicate that there already are acid

functional groups in the biochar, or other compounds that interfere with the titration. For the BPL-AC

there was only one negative value. However, there was no trend to be seen among the other results.

The increasing of plasma activation time did not seem to affect the functional group in any specific

direction. Most of all, there was too little data produced to make any substantial analysis. Further

repetitions of the experiment would have been necessary.

Recent studies show that the Boehm titration method might not be suitable for analysis of Boehm

titration. The Boehm titration was originally developed to measure acidic functional groups on

activated carbon and carbon black. Although there is no standardization for the usage of Boehm

titration on biochar, it has been increasingly used in the same way as for the other carbonic materials.

However, biochar has higher ash content as well as higher carbon solubility. These properties might

influence the result of the Boehm analysis. Efforts to remove ash and DOC before performing the

experiments might increase the reliability of the Boehm titration with biochar (Fidel, et al., 2014). This

could be one reason for why the titration results show negative values for the biochar.

The result from the activated carbon samples does not show more than one negative value. This could

indicate that the Boehm titration method is more suitable for activated carbon than biochar, which

show much more scattered results. However, as previously mentioned, further investigation is needed.

5.1. Limitations

The greatest limit of this project has been the time limitation. The summer research school took place

during four weeks in the summer of 2015. Due to this drawback there is merely one repetition for each

sample (with a few exceptions where there are two repetitions). This is obviously not enough to

conclude anything from the resulted data. If more time was provided, additional repetitions of the

experiments could be made, which would increase the reliability of the data.

5.2. Sources of error

As previously mentioned, there are some doubts about the justification of using the Boehm titration

method on biochar (Fidel, et al., 2014). Furthermore, all the titrations were made manually which

induce the human error.


- 11 -

6. Conclusion

This report of plasma activation of biochar shows neither promising nor desponding results for the

future of plasma and biochar. From the obtained results, no conclusion can be made about the

efficiency of the activation. However, it still stands that the plasma activation is a quick and cost-

efficient method compared to conventional activations processes. Further investigation must be made,

especially to ensure an analyzation method that shows accurate results of the amount of surface

oxygen-containing functional groups in biochar. Additional research about how suitable the Boehm

titration is for use on biochar analysis should be considered. To conclude, even though the results of

this project were unsatisfactory, plasma activation of biochar is still an interesting and promising topic

for further research.

7. Acknowledgement

The author wants to thank Professor Jinjing Luo for supervising this project. A special thank to

research assistant Shiqiang Sun for many valuable comments and explanations about the experiments.

A last thank to the organizers at Lund University and Xiamen University for making the Lingfeng

Summer Research School possible with many memorable moments and cultural experiences.


- 12 -

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OF CARBONS CHARACTERIZED BY THEIR CONTINUOUS pK DISTRIBUTION AND

BOEHM TITRATION. Carbon, Volume 35, pp. 83-94.

F., S., R., C. & A., L., 2011. Elemental mercury vapor capture by powdered activated carbon in a

fluidized bed reactor. Fuel, 90(6), pp. 2077-2082.

Fidel, R. B., Laird, D. A. & Thompson, M. L., 2014. Evaluation of Modified Boehm Titration

Methods for Use with Biochars. Journal of Environmental Quality, Volume 42, pp. 1771-1778.

Gupta, R. K., 2015. Biochar activated by oxygen plasma for supercapacitors. Journal of Power

Sources, Volume 274, pp. 1300-1305.

Huayi, D., 2014. Environmental Adsorption Behavior of Biochar and its Application in Remediation of

Cadmium Contaminated Soil, Xiamen: Xiamen University.

Jung, K.-W., Hwang, M.-J., Jeong, T.-U. & Ahn, K.-H., 2015. A novel approach for preparation of

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345.

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from water with biochar, a renewable, low cost and sustainable adsorbent – A critical review.

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Appendices

Table A1. Raw data from the titration of powder biochar

2015.7.1 BC700 Incubation 24h

Solution Activated carbon

(g)

Titration consumption of HCl (mL)

Surface functional groups

Blank BC700 Diff. mmol/100 g

NaHCO3 1,0026 9,90 9,80 0,10 3,00

Na2CO3 1,0003 19,69 19,94 -0,25 -10,53

NaOH 1,0011 8,88 7,96 0,92 35,21

CH3CH2ONa 1,0010 9,71 9,32 0,39 -15,94



(g)




NaHCO3 1,0010 9,81 9,76 0,05 1,50

Na2CO3 1,0013 19,50 19,00 0,50 13,54

NaOH 1,0020 8,84 8,13 0,71 6,30

CH3CH2ONa 1,0000 9,68 8,64 1,04 9,98


Solution Activated carbon (g)




NaHCO3 1,0040 10,09 9,97 0,12 3,60

Na2CO3 1,0003 19,90 19,42 0,48 10,85

NaOH 1,0009 9,25 8,30 0,95 14,14

CH3CH2ONa 1,0011 9,58 9,22 0,36 -17,76

Table A2. Raw data from the titration of granule biochar.

2015.7.6 BC-P-5 Incubation 24h




Blank Sample Diff. mmol/100 g

NaHCO3 1,0033 10,06 10,26 -0,20 -5,91

Na2CO3 1,0030 19,83 19,50 0,33 15,66

NaOH 1,0030 9,10 8,47 0,63 8,87


- 2 -

CH3CH2ONa 1,0039 9,56 9,22 0,34 -8,58






NaHCO3 1,0033 10,06 10,00 0,06 1,77

Na2CO3 1,0030 19,83 19,52 0,31 7,39

NaOH 1,0030 9,10 8,48 0,62 9,16

CH3CH2ONa 1,0039 9,56 9,70 -0,14 -22,46

2015.7.6 BC-P-30 Incubation 24h T=350 ℃





NaHCO3 1,0006 10,06 9,93 0,13 3,91

Na2CO3 1,0003 19,83 18,51 1,32 35,83

NaOH 1,0009 9,10 7,99 1,11 -6,34

CH3CH2ONa 1,0002 9,56 9,42 0,14 -29,19






NaHCO3 1,0013 9,84 10,00 -0,16 -4,81

Na2CO3 1,0001 19,57 19,51 0,06 6,62

NaOH 1,0009 9,00 8,59 0,41 10,53

CH3CH2ONa 1,0031 9,44 8,94 0,50 2,68



(g)




NaHCO3 1,0017 10,18 9,98 0,20 5,92

Na2CO3 1,0019 19,88 19,50 0,38 5,32

NaOH 1,0018 9,87 8,76 1,11 21,60

CH3CH2ONa 1,0027 9,46 8,67 0,79 -9,49



(g)




NaHCO3 1,0024 10,20 9,95 0,25 7,14

Na2CO3 1,0026 19,71 19,39 0,32 2,00

NaOH 1,0032 9,90 9,70 0,20 -3,43


- 3 -

CH3CH2ONa 1,0039 9,32 9,32 0,00 -5,71






NaHCO3 1,0022 10,20 9,90 0,30 8,57

Na2CO3 1,0036 19,71 19,02 0,69 11,11

NaOH 1,0022 9,90 9,40 0,50 -5,40

CH3CH2ONa 0,9994 9,32 9,30 0,02 -13,71

Table A3. Raw data from the titration of BPL activated carbon.

2015.7.11 BPL Incubation 24h





NaHCO3 1,0030 10,22 9,98 0,24 7,09

Na2CO3 1,0033 19,78 19,38 0,40 4,72

NaOH 1,0001 9,91 9,30 0,61 6,26

CH3CH2ONa 1,0009 10,20 8,31 1,89 37,89

2015.7.13 BPL1000-P0 Incubation 24h





NaHCO3 1,0004 10,20 10,34 -0,14 -4,15

Na2CO3 1,0030 19,68 19,18 0,50 18,92

NaOH 1,0006 9,90 9,16 0,74 7,14

CH3CH2ONa 1,0032 9,58 8,49 1,09 10,28



(g)




NaHCO3 1,0031 10,18 9,71 0,47 13,41

Na2CO3 1,0026 19,68 19,16 0,52 1,43

NaOH 1,0027 9,92 8,92 1,00 13,70

CH3CH2ONa 1,0006 9,76 8,04 1,72 20,65

2015.7.11 BPL Incubation 24h


- 4 -


(g)




NaHCO3 1,0032 10,22 10,03 0,19 5,61

Na2CO3 1,0037 19,78 19,50 0,28 2,65

NaOH 1,0014 9,91 9,26 0,65 10,97

CH3CH2ONa 1,0031 10,20 8,20 2,00 39,86



(g)




NaHCO3 1,0035 10,20 9,77 0,43 12,70

Na2CO3 1,0035 19,68 19,04 0,64 6,20

NaOH 1,0006 9,90 8,88 1,02 11,31

CH3CH2ONa 1,0016 9,58 8,02 1,56 15,95



(g)




NaHCO3 1,0010 10,18 10,06 0,12 3,43

Na2CO3 0,9997 19,68 19,08 0,60 13,75

NaOH 1,0033 9,92 8,91 1,01 11,63

CH3CH2ONa 0,9996 9,76 8,04 1,72 20,43

Plasma activation of straw biochar and quantification of ...The Boehm titration method to identify acidic functional groups is mainly used because it is fast and inexpensive. However,

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