LEAD SORPTION FROM INDUSTRIAL EFFLUENTS USING AGRICULTURAL WASTES: IDENTIFICATION OF THE BEST METHOD FOR NIGERIA. BY LAIYEMO, MICHAEL ADEMOLA (STUDENT ID: 1123956) A DISSERTATION SUBMITTED IN PARTIAL FULFILMENT OF THE AWARD OF A MASTERS OF SCIENCE DEGREE IN ENVIRONMENTAL SCIENCE: LEGISLATION AND MANAGEMENT
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LEAD SORPTION FROM INDUSTRIAL EFFLUENTS USING
AGRICULTURAL WASTES: IDENTIFICATION OF THE
BEST METHOD FOR NIGERIA.
BY
LAIYEMO, MICHAEL ADEMOLA
(STUDENT ID: 1123956)
A DISSERTATION SUBMITTED IN PARTIAL FULFILMENT OF THE AWARD OF
A MASTERS OF SCIENCE DEGREE IN ENVIRONMENTAL SCIENCE:
LEGISLATION AND MANAGEMENT
SUPERVISOR: DR. ABDUL CHAUDHARY
SEPTEMBER 2012
Laiyemo, Michael A. 1123956
DEDICATION
I dedicate this dissertation to my parents Mr Omololu and Mrs Feyisara Laiyemo, for whom
God has used to be my pillar of support during my course of study. Just to let you know that
out of a billion parents, I will choose both of you over and over again and this work would not
have been possible without you. Thank you very much.
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Laiyemo, Michael A. 1123956
ACKNOWLEDGEMENT
“Instruct the wise and they will be wiser; teach the righteous and they will add to their learning” Prov. 9: 9.
Most supervisors fix appointments for consultation but an exception is Dr. Abdul Chaudhary whose door is always opened for students. My greatest appreciation goes to my supervisor, Dr. Abdul Chaudhary because of his magnificent support and guidance during this dissertation.
I appreciate the support of my sisters; Kofo, Kemi and especially Lamide who has significantly been part of my educational progress.
My brothers from another mother; Mayowa Oshin and Godwin Nwokobia, thank you guys for the moral support, and being there for me in times of need. May God reward you abundantly.
To the almighty God, who has brought me this far in life, continue to guide and protect me in all my ways of life.
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Laiyemo, Michael A. 1123956
CERTIFICATE OF AUTHORSHIP
4
“I, Laiyemo Michael A., hereby certify that:
Each and every quotation, diagram or other piece of exposition which is copied from or based upon the work of others has its source clearly cited and referenced in the text at the place where it appears.
All research studies in this report have been carried out by me with no more assistance from members of the institution than has been specified.
Name: Laiyemo, Michael A.
Signature:
Date: 21st September, 2012
Laiyemo, Michael A. 1123956
ABSTRACT
This study demonstrates why Nigeria as a developing country and having series of lead pollution problems by processing industries should implement a cheap and efficient technology for lead removal from industrial effluent. The Federal Environmental Protection Agency (FEPA) set down policies for processing industries to engage in the best available technology (BAT) during effluent treatment and there has to be reduction of toxic chemicals to a minimum level before effluents are discharged into receiving waters.
So despite the numerous methods to remove lead from a solution, biosorption technology is the most cost effective and environmentally friendly because it makes use of reusable low cost agricultural waste as adsorbent.
In this study, comparative analysis of selected agricultural wastes used in the preparation of adsorbents for the biosorption of lead from industrial effluent was done. The agricultural wastes compared are orange peels, sugarcane bagasse, rice husk and maize cob. The study was performed in order to identify the best agriculture waste in terms of adsorption efficiency and cost effectiveness that can be introduced in the biosorption of lead from industrial effluents in Nigeria.
Each selected agricultural wastes was subjected to SWOT and PEST analyses in which the analyses were based on adsorption capacity of the adsorbent, the adsorption rates, equilibrium time for lead removal, availability of the agricultural waste in Nigeria, desorption rate of the adsorbed lead from the adsorbent, the social and environmental impact and finally the political implications of using the agricultural wastes.
Work done by researchers (secondary data) were used throughout this study and it was discovered that adsorption capacity of the agricultural wastes differ depending on the adsorbent treatment, temperature of reaction, pH of the solution, contact time and adsorbent loading.
However based on the available data, the research showed that modified adsorbents show better adsorption capacities than unmodified adsorbents. Triethylene-tetramine modified sugarcane bagasse has the highest adsorption capacity of 313mg/g compared to the other wastes and further evaluation of the comparative parameters highlighted that triethylene-tetramine modified bagasse is the best method that can be used in lead biosorption from industrial effluents in Nigeria.
(NaCl), 0.2 M hydrochloric acid (HCL), and nitric acid (HNO3).
The mixtures of the metal ion bounded adsorbent and the desorption solutions were shaken
vigorously for about 45 minutes and then filtered, the filtrate which is the saw dust was
analysed to determine the amount of lead ions left after desorption. However, the experiment
was repeated four times using the same adsorbent.
Akissi et al (2010) reported the desorption ratio to be calculated as the amount of lead ion
desorbed/amount of lead ion adsorbed.
The result of the experiment showed that EDTA had the highest percentage of desorption of
about 77.29% and the lowest rate of desorption was double distilled water which was 2.11%.
Further adsorption with the same sawdust reduced the amount of lead ion adsorbed due to the
fact that some lead ions where still present after the desorption process.
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2.7 Industrial application of the biosorption method for lead ion removal from an aqueous solution
36
Metal ion
Acid or Base solutionpH control
Adsorbent vessel
CSTR
Temp guage
pH meter
Desorption solution
Filtration tank
CSTR
Heavy metal solution tank
Treated waste water tank
Filtration tank
Temp. guage
pH
m
tre
Adsorbent recycle
Figure 2.1: Schematic flow diagram showing the biosorption of heavy metals from industrial wastewater using adsorbents
Source: Igwe and Abia (2006)
Laiyemo, Michael A. 1123956
The above flow diagram is the schematic representation of the industrial application of the
biosorption method by removing metal ions from industrial wastewater using an adsorbent as
discussed by Igwe and Abia (2006). It can be seen from the diagram that the wastewater
containing the metal ion for an example, lead ion is introduced into the reactor and also the
adsorbent is introduced into the continuously stirred tank reactor (CSTR). The adsorbent could
have been pre-treated or modified if necessary, and after the introduction of both wastewater
and adsorbent into the CSTR, they are both stirred continuously for a period of time in the
reactor and the adsorption of the metal ion onto the adsorbent takes place. After equilibrium
has been attained for the adsorption process, the adsorbent becomes saturated and no more
metal ion is adsorbed on its surface. The solution goes into the filtration tank and it is filtered
thereby separating the adsorbent saturated with metal ion from the wastewater, the resultant
wastewater is collected in a tank and the adsorbent is ejected into another CSTR for the
purpose of desorption. Furthermore, after the completion of the desorption process, filtration
takes place and gives heavy metal ion solution which is kept in a tank for further purification
and the used adsorbent is recycled for re-use.
Igwe and Abia (2006) concluded by ascertaining that previous experimental data gotten from
isotherm calculations, kinetics studies and intra particle studies are useful in calculating
energy balances and material balances, and the plant specifications for the development of an
industrial biosorption plant. However, as stated by Igwe and Abia (2006), more research is
required for the implementation of such technology in industries.
2.8 ConclusionThe literature review highlighted the importance of using agricultural wastes for heavy metal
removal from industrial effluents in Nigeria, moreover various investigations carried out by
researchers showed that rice husk, orange peel, maize cob and sugarcane bagasse are suitable
agro wastes for the sorption of lead from aqueous solution regardless if untreated or treated.
But their rate of absorption and adsorption capacities differs depending on various factors like
adsorbent pre-treatment methods, their surface characteristics, pH of the solution, adsorbent
loading, contact time and temperature.
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Laiyemo, Michael A. 1123956
However, as the aim of this study depicts, the best method in terms of using agricultural
wastes need to be identified for easy implementation of the biosorption method in Nigeria.
In order to achieve this aim, absorption capacities of these selected wastes have to be
considered in relation to cost effectiveness, also social and political impacts of implementing
this method in Nigeria have to be studied.
The next chapter discusses the methods used for the critical analysis in identifying the best
agricultural waste that is suitable for Nigeria.
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CHAPTER 3: Methodology
3.1 MethodologyIn this study, extensive secondary data will be sourced and analysed to generate a clear
understanding of the aim and objectives. Figure 3.1 below illustrates the overview of the
research study. From various agricultural wastes used as adsorbents for the biosorption
process, four of them, namely; orange peels, rice husk, sugarcane and maize cob were selected
for the study.
Secondary data will be used to undergo comparison between different parameters involved in
the process of biosorption of lead, such parameters include; adsorption capabilities of the low
cost agricultural wastes, their adsorption rates, modification methods, equilibrium time for the
experiment and the availability of the selected adsorbents in Nigeria. Similarly, various
reports and peer review papers that have discussed the removal of lead using the selected
agricultural wastes at different conditions will be sourced. Furthermore, the comparison will
also involve the use of statistical analysis obtained from secondary sources.
Papers from chemistry journals are sourced to characterize the adsorbent surfaces and to
gather information on their physicochemical properties.
Figure 3.1: Overview of the research study
39
BiosorptionProcess
Sugarcane bagasse
Rice husk
Orange peels
Secondary data collection
SWOT analysis
PEST analysis
Nigeria
Results Best method identification
Agricultural wastes
MaizeCobs
Laiyemo, Michael A. 1123956
3.2 Analytical ToolsThe tools that will be used to make comparison between the selected agricultural wastes are S-
W-O-T and P-E-S-T analytical tools.
3.2.1 SWOT analysisBasically SWOT is an acronym for strength, weakness, opportunity and threats, and it is used
as a method for choosing a suitable strategy for embarking on a project by considering the
projects internal capacity (strength and weakness) and its external situation (opportunity and
threats) (Oetomo and Ardini, 2009). However after identifying SWOTs, the strength can be
used as an advantage over weakness and the threats can be converted to opportunities (Miller,
2006).
The SWOT analysis will be aided by the use of a SWOT matrix shown in Table 3.1 below, in
which the strengths, weaknesses, opportunities and threats of each method will be highlighted
upon, and the possible solutions to combat this weaknesses and threats by making use of the
existing opportunities and strengths will be discussed. Further to the discussion, the best
method that is most viable in the Nigerian context will be determined.
Table 3.1: Template of the SWOT matrix
STRENTHS WEAKNESSES
C Strength 1
Strength 2
Strength 3
D Weakness 1
Weakness 2
Weakness 3
OPP
OR
TUN
ITIE
S A Opportunity 1
Opportunity 2
Opportunity 3
E F
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Laiyemo, Michael A. 1123956
T
HR
EATS
B Threat 1
Threat 2
Threat 3
G H
Box A represents the opportunities involved in making use of the agricultural waste for the
biosorption process, box B contains the threats associated with the usage of the agricultural
waste, box C is the strength of the particular agricultural waste, and box D contains the
weaknesses of the agricultural waste. As part of the analysis, box E contains the processes
initiated to take advantage of the opportunities by making use of the strength possessed by the
agricultural waste, box F represents the processes involved to reduce the adsorbent
weaknesses by making use of the opportunities, box G contains suggestions in which the
strength can be used to anticipate or reduce the threats involved in using the adsorbent, and
box H contains the suggestions for reducing the weaknesses possessed by the adsorbent and
also to reduce the threats of using the adsorbent.
3.2.2 PEST analysis
PEST is an acronym for political, economic, social and technology. It is an analytical tool for
comprehending the political, economic, social and technological aspects of an operation
(CIMA, 2007). It is perceived that the PEST analysis coupled with SWOT analysis will give a
better understanding of the scenario being analysed and will in turn produce a better
judgement.
3.2.3 Justification in using SWOT and PEST analytical toolsThese methods of analysis where employed because they are believed to be most applicable
for the caparison between the agricultural wastes for the biosorption process. In addition,
SWOT and PEST analysis best explains thoroughly the strength, weakness, opportunity and
threats involved with the use of the selected agricultural wastes as well as the political,
economic, social and technological views of their application in the Nigerian community.
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Laiyemo, Michael A. 1123956
More so, this approach facilitates judgements based on key factors identified by the SWOT
and PEST analysis, and consequentially a critical evaluation of these factors will bring to a
conclusion of identifying the best agricultural waste method that suits industrial effluent
treatment in Nigeria.
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CHAPTER 4: Results and Discussion
The following parameters are used to identify the data for the SWOT and PEST analysis of
orange peels, sugarcane bagasse, maize cobs and rice husk;
(i) Availability in Nigeria
(ii) Absorption capacities
(iii) Equilibrium time for adsorption
(iv) Adsorption rate
(v) Adsorbent treatment methods
(vi) Desorption rate (Metal recovery)
(vii) Social and environmental impact
4.1 Availability of the selected agricultural wastesIt is of great importance that the agricultural waste for the biosorption process must be
indigenous to Nigeria and as part of the data collection for the analysis of the different
methods for biosorption in Nigeria, the geographical distribution and availability of these
agricultural wastes are required. Hence, the following sections identifies the agricultural
wastes and there availability in Nigeria;
4.1.1 Availability of Orange peel in NigeriaCitrus fruits are well grown in Nigeria but the most produced citrus fruit is the sweet orange
which is grown and cultivated in fifteen states of Nigeria. However it has been reported that
about 0.3 million tonnes orange wastes yearly are generated in Nigeria which implies that the
wastes in form of peels will be in high volume and if not in use will constitute environmental
pollution. (Oluremi, et al., 2006, Ezejiofor, et al., 2011). Moreover to make these waste
materials useful, they can be turned into adsorbent for the biosorption process.
Although peels are thought to be a source of food for livestock, but its low nutrient contents
and bitter taste makes its usefulness limited in that aspect (Oluremi et al 2006), and thereby
give room for such a chunk of produced orange waste to be used in processes like biosorption.
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Laiyemo, Michael A. 1123956
4.1.2 Availability of Sugarcane bagasse in NigeriaSugarcane bagasse is the bit left after the juice of the sugarcane has been sucked out
(Alsharief 2012). Nigeria’s main raw material for sugar production is sugarcane, hence the
availability of bagasse as waste is linked to places with sugar production (Rossi, et al., 2002,
Abgoire, et al., 2002).
4.1.3 Availability of Rice husk in NigeriaErenstein et al., (2003) reported that rice is a cash crop produced mainly for commercial
purposes in Nigerian, but due to the fact that rice production yields a low return, there is
reduction in its productivity and consequentially increase in the cost of production.
Furthermore, policies have not been able to procure a place in the market for locally produced
rice merchants, so rice imports in Nigeria have been reported to have a giant share in the
statistics of imported agricultural produce into Nigeria (Erenstein et al., 2003, Nigerian
Tribune, 2010). Since rice is majorly imported in Nigeria, the existence of rice husk is limited
and therefore be a constraint for its use in biosorption process.
4.1.4 Availability of Maize cob in NigeriaNigeria is regarded as the second largest producer of maize in Africa, moreover the Nigerian
climatic condition favours maize growth. Cob, a part of the maize that bears the grain
represents 30% of maize agricultural wastes and being that about 8 million tonnes of maize is
produced in Nigeria annually with an increase of 23% in the production prediction between
2010 and 2015, there is an indication that corn cobs are produced in large volumes in Nigeria
(Akinfemi and Ladipo, 2011, Saliu and Sani, 2012, Ogunbode and Apeh, 2012).
4.2 Description of other comparison parametersTo understand the significance of the data acquired from work done by researchers used in
this study, it is paramount to understand the following terms;
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Laiyemo, Michael A. 1123956
4.2.1 Adsorption capacity
This is the maximum value of the amount of lead that is adsorbed per gram of the agricultural
waste (adsorbent) at equilibrium time (Knaebel 1995).
4.2.2 Equilibrium timeThis is the time at which the concentration of the metal ions being adsorbed by the adsorbent
is equal to the concentration of the exchanged ions leaving the surface of the adsorbent. At
this time, the surface of the adsorbent becomes saturated and cannot accept any more metal
ions (Site, 2000).
4.2.3 Adsorption rateThe percentage ratio of the adsorbed lead concentration to the total concentration of lead
present in the aqueous solution is termed adsorption rate. So therefore, it is the total amount of
lead adsorbed from aqueous solution by the adsorbent (Site, 2000).
4.2.4 Desorption rateThis is the percentage of removing the adsorbed metal ion from the adsorbent by using a
suitable reagent. The efficiency of the desorption process is known by the difference between
the quantity of lead in the desorption solution and the quantity of lead adsorbed by the
adsorbent (Akissi, et al., 2010).
4.3 Data collectedTable 4.1 below shows the data collected from the work done by researchers comprising of
the comparison parameters described above. All experiments by the researchers were done at
room temperature and they all stated that the adsorption capacities were pH dependent, in the
sense that increase in pH increases the adsorption capacities. The optimum pH whereby the
best lead adsorption occurred has been indicated in Table 4.1. However, pH higher than the
optimum values will encourage the precipitation of lead hydroxide which will hinder the rate
of lead adsorption.
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Laiyemo, Michael A. 1123956
Table 4.1: Work done by researchers on the removal of lead from aqueous solution using the Selected agricultural wastes
Agricultural
wastes;
unmodified/
modified.
Modifica-
tion
methods.
Adsorption
capacity
(mg/g).
Adso-
rption
rate
(%).
Equilibrium
time (min).
Desorp-
tion
rate
(%).
Optimum
pH
Sources
Orange peel
113.5
55.52
64.3
73.5
10
500
-
35.9
5.5
5
Feng and
Guo, 2012
De Souza et al., 2012
Modifiedorange peel
NaOH-
CaCl2
NaOH-Citric acid
209
84.53
99.4
74.9
10
500
-
38.0
5.5
5
Feng and
Guo, 2012
De Souza et al., 2012
Korean mandarin
orange peel 13.5 44.2 50 5 Park,
2010
Rice husk 0.06216 96.8 60 - Elham,et al., 2010
Modified rice Tartaric - 5.3 Wong,
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Laiyemo, Michael A. 1123956
Husk acid
15% alkali
treatment with
autoclave (Biomatri
x)
108
58.1
93
80
120
120-150-
(5.5˗6) ± 0.1
et al., 2003
Krishnani, et al.,
2008
Sugarcane bagasse
6.366 100 120 5 Martín Lara, et al., 2010
ModifiedSugarcane
bagasse
Sulphuric acid
Citric
acid
Triethylen
e-
tetramine
7.297
52.63
313
100
-
-
120
1440
50
-
98
-
5
-
5
Martín Lara, et al., 2010
Dos Santos, et al., 2010
Osvaldo, et al., 2007
Maize cob 1.09 - 90 - 5 Jonglertjunya,2008
Modified maizeCob
Natural fungi
growth
H3PO4
14.75
3.150
-
-
90
90
-
-
5
5
Jonglertjunya,2008
Nale, et al.,
2012
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Laiyemo, Michael A. 1123956
EDTA 144.93 - 60 - 7.5 Igwe and
Abia, 2007
4.4 SWOT and PEST analysis of the selected agricultural wastes used for lead biosorption.As discussed earlier in chapter 3, the SWOT analysis will be aided by a SWOT matrix for a
complete evaluation of each agricultural waste, and to compliment this method of analysis is
the inclusion of PEST analysis.
Table 4.2: SWOT matrix for orange peel adsorbent used for lead biosorption
STRENGHTS WEAKNESSESC •Unmodified orange peel has high adsorption capacities of 113.5 mg/g and 55.2 mg/g according to research by Feng and Guo, (2012) and De Souza et al., (2012) respectively.
•Adsorption rate is also high for unmodified orange peel.
•Equilibrium time for maximum adsorption is 10 minutes according to Feng and Guo, (2012) and this is low compared to other waste adsorbents.
•Modifying with NaOH-CaCl2 gives adsorption capacity of 209mg/g which is relatively higher than some of the adsorbents being compared.
D •Equilibrium time is 500 minutes according to a study by De Souza et al., (2012), and this is relatively high compared with the other agro-wastes.
•The rate of metal recovery is 35.9% which is quite low as indicated by the desorption studies carried out by De Souza et al., 2012.
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Laiyemo, Michael A. 1123956
O
PPO
RTU
NIT
IES
A •Orange peel wastes are in abundance in Nigeria and they are readily available.
•It can be modified with NaOH-CaCl2 for better efficiency.
•When implemented with the biosorption process, it is cheaper than other conventional processes.
•Policies are available for its implementation.
E •Being a cheap method for lead extraction, and because it has a high adsorption capacity and absorption rate for lead removal and coupled with a low equilibrium time makes it a potential adsorbent for the biosorption method even when used untreated.
•Modification with NaOH-CaCl2
gives a better adsorption rate, higher adsorption capacity and low equilibrium time.
F •Modifying the orange peel with sodium hydroxide and citric acid before the biosorption process, increases the desorption rate to 38% which still indicates a low metal recovery rate.
TH
REA
TS
B •Few researchers have carried out studies on the desorption rate of lead from orange peel.
•It may require permits or licencing for implementation and the process of acquiring them may be tasking or expensive.
•Modifying the orange peel may increase the operating cost of the process.
G •Workshops in the form ofdevelopment programs should be initiated and it will make people including government officials perceive the importance of using orange peel for the biosorption process. This will reduce any tariff or licence levy placed on its implementation.
H •Because few researchers have studied the desorption rate of lead from orange peel, other researchers should utilize the opportunity by investigating other avenues for increasing the rate of the metal recovery from orange peel.
Table 4.2.1: PEST analysis for orange peel adsorbent used for lead biosorption
POLITICAL
•There are available policies to implement the biosorption technology using orange peel as an adsorbent in Nigeria.
ECONOMIC
•It is considered as less expensive and an economically viable method of lead extraction from waste water.•Further treatment is required to dispose the metal binded adsorbent due to its low desorption rate, and this increases the operating cost.
SOCIAL
•The method is perceived to be accepted by the people because it is environmentally friendly.
•Reduces environmental pollution caused by orange peels.
TECHNOLOGY
•Biosorption is a new technology that is yet to be implemented at an industrial level.
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Laiyemo, Michael A. 1123956
Table 4.3: SWOT matrix for rice husk adsorbent used for lead biosorption
STRENGHTS WEAKNESSES
C •High adsorption rate of 96.8% for unmodified rice husk.
•Equilibrium time for maximum adsorption is low for both modified and unmodified rice husk.
•Treatment with tartaric acid or biomatrix formation gives adsorption capacities of 108mg/g and 58.1mg/g respectively.
•Adsorption rate is high for both modification of rice husk.
D •The adsorption capacity is 0.06216 mg/g for unmodified husk which is the least compared with the selected agro wastes.
OPP
OR
TUN
ITIE
S
A •It can be modified for better efficiency by treatment with tartaric acid, and forming a rice husk bio matrix also increases its efficiency.
• There are available policies to implement the biosorption technology using orange peel as an adsorbent.
E •It will be a suitable adsorbent upon treatment with tartaric acid because its adsorption rate and capacity will increase.
F •Modifying the rice husk with tartaric acid will increase its lead adsorption capacity.
•Available policies indicate government’s interests in such environmentally friendly project, so therefore the government can be asked to partly fund the project. This shifts the burden of rice husk treatment cost away from the industry.
T
HR
EATS
B •Abundance of rice husk wastematerials are not certain because of reduced rice production in Nigeria compared with other agricultural produce.
• Few researchers have carried out studies on the biosorption of lead using rice husk.
•If modified with chemical reagents or heat, it may increase the cost of the biosorption process compared to unmodified wastes.
•It may require permits or licencing for implementation and the process of acquiring them may be tasking or expensive.
G •The high adsorption rate or low equilibrium time may offset the cost incurred during modification of the rice husk with tartaric acid.
H •More investigation is needed for biosorption of lead using tartaric acid treated rice husk to determine the desorption rate.
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Laiyemo, Michael A. 1123956
Table 4.3.1: PEST analysis of rice husk adsorbent used for lead biosorption
Table 4.4: SWOT matrix for sugarcane bagasse adsorbent used for lead biosorption
STRENTHS WEAKNESSES
C •High rate of adsorption by untreated bagasse.•Equilibrium time is low for untreated bagasse and triethylene-tetramine modified bagasse.
•Treatment with citric acid and triethylene-tetramine increases its adsorption capacity as reported by Dos Santos et al., (2010) and Osvaldo, et al., (2007) respectively.
•Desorption studies by Dos Santos et al., (2010) confirm the metal recovery rate to be 98% which is very high compared to other methods.
D •Untreated sugarcane bagasse gives a low adsorption capacity for lead.
•Treatment with sulphuric acid still gives a low adsorption capacity.
•Equilibrium time is high with the citric acid treated bagasse.
51
POLITICAL
•There are available policies to implement the biosorption technology using rice husk as an adsorbent in Nigeria.
•Major importation of rice by selected people due to political motives threatens the abundance of rice husk required in the biosorption process.
ECONOMIC
•Lead adsorption by rice husk adsorbent requires treatment of the adsorbent in other to achieve a desirable result. However, the treatment is done using chemical reagents and heat. The chemicals contribute additional cost for the project and the heating will increase the energy consumption during the process and will in turn increase the cost.
SOCIAL
• Reduces environmental pollution caused by rice husk.
TECHNOLOGY
• Biosorption is a new technology that is yet to be implemented at an industrial level.
•it is perceived to be an easy and straight forward technology in reducing environmental impact caused by industrial processes.
Laiyemo, Michael A. 1123956
OPP
OR
TUN
ITIE
S
A •Sugarcane bagasse wastes are readily available in Nigeria in millions of tonnes.
•There are available policies to implement the biosorption technology using sugarcane bagasse as an adsorbent.
•It can be modified with triethylene-tetramine and citric acid for better efficiency.
E •Potentially, sugarcane bagasse can be used for biosorption due to its abundance, and because there are available policies requiring the best available technology for effluent treatment and its tendency to be modified with triethylene-tetramine or citric acid for better efficiency.
F •The adsorption capacity is increased upon treatment with triethylene-tetramine or citric acid but treatment only with triethylene-tetramine gives a low equilibrium time of 50 minutes.
T
HR
EATH
S
B •If modified with triethylene-tetramine or citric acid, it may increase the cost of the biosorption process compared to unmodified wastes.
•It may require permits or licencing for implementation and the process of acquiring them may be tasking or expensive.
G •The high adsorption capacity and the high metal recovery rate for citric acid treated bagasse may offset the cost incurred during modification of the sugarcane bagasse because the metal recovered can be recycled and used as raw materials for other industrial processes and the adsorbent can also be reused over again which makes the process cost effective.
H •Workshops in the form of development programs should be initiated and it will make people including government officials perceive the importance of using modified sugarcane bagasse for the biosorption process. This will reduce any tariff or licence levy placed on its implementation.
•Movement to seek for government funding will reduce the cost involved in the adsorbent treatment method.
•Increasing the low absorption capacity and reducing the equilibrium time will be achieved by modifying the bagasse with triethylene-tetramine.
Table 4.4.1: PEST analysis of sugarcane bagasse adsorbent used for lead biosorption
52
POLITICAL
•There are available policies to implement the biosorption technology using sugarcane bagasse as an adsorbent in Nigeria.
ECONOMIC
•It is considered as less expensive and an economically viable method of lead extraction from waste water.
SOCIAL
• Reduces environmental pollution caused by sugarcane bagasse.
•it is perceived to be a totally acceptable technology due to its environmental friendliness and cost effectiveness compared to other conventional methods of lead extraction.
TECHNOLOGY
•It is perceived to be an easy and straight forward technology in reducing environmental impact caused by industrial processes.
• Biosorption is a new technology that is yet to be implemented at an industrial level.
Laiyemo, Michael A. 1123956
Table 4.5: SWOT matrix for maize cob adsorbent used for lead biosorption
STRENTHS WEAKNESSESC •Low equilibrium time if unmodified.
•Adsorption capacity of 144.3mg/g when treated with ethylene diamine tetra-acetic acid (EDTA).
•A low equilibrium time of 60 minutes when treated with EDTA.
D •Low adsorption capacity if unmodified.
•Increased adsorption capacity when treated with natural fungi growth but it is still low compared to other selected wastes.
•Low adsorption capacity when modified with H3PO4.
OPP
OR
TUN
ITIE
S
A •There is abundance of maize cob due to availability of maize crop in Nigeria.
•It can be modified with a natural fungal growth, EDTA, and H3PO4 for better efficiency.
• There are available policies to implement the biosorption technology using maize cob if considered as the best available technology (BAT).
E •It should be modified with EDTA in order to increase its adsorption capacity, to reduce its equilibrium time and the abundance of maize crop makes its cob to be a potential adsorbent in the biosorption process.
F •From the data obtained, to have increased adsorption capacity comparable to other agricultural wastes, the maize cob has to be treated with EDTA.
T
HR
EATH
S
B •There is no information on the adsorption and desorption rate of lead when using maize cob as the adsorbent. So therefore there is limited data on its usage.
•Modifying with natural fungal growth, EDTA, and H3PO4 may increase operating cost.
•It may require permits or licencing for implementation and the process of acquiring them may be tasking or expensive.
G •Further research is necessary to determine the desorption rate of EDTA treated maize cob.
•The high adsorption capacity and the low equilibrium time may offset the cost incurred during modification of the maize cob.
H • To reduce the weakness and threats identified, it is important to treat the maize cob with EDTA.
•More research is needed to gather information on the biosorption process using maize cob as adsorbent.
•Workshops in the form ofdevelopment programs should be initiated and it will make people including government officials perceive the importance of using modified maize cob for the biosorption process. This will reduce any tariff or licence levy placed on its implementation.
Table 4.5.1: PEST analysis of maize cob adsorbent used for lead biosorption
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4.5 Discussion
4.5.1 Outcome of the SWOT analysesThe SWOT matrix helped in highlighting the main points to consider when using each
individual agricultural waste for the biosorption process. These points are discussed in the
following sections below;
4.5.1.1 Orange peelAbundance of orange peel in Nigeria suggests the potentiality of it to be a good adsorbent for
the biosorption of lead. However, the SWOT matrix pin pointed out the factors that made
orange peel to be potentially viable for the biosorption process and ironically also shows the
limitation to be encountered if it is implemented in the biosorption process.
For instance, lead adsorption with orange peel was studied by Feng and Guo, (2012) and De
Souza et al., (2012) and they had its adsorption capacities to be of 113.5 mg/g and 55.2 mg/g.
These are good values because they simply depict the amount in grams of lead adsorbed by 1
gram of orange peels and having the values of 113.5 and 55.2mg/g shows that a substantial
amount of lead is adsorbed by orange peel. However, not just the adsorption capacity is to be
considered for viability because equilibrium time for the reaction is also an important factor to
54
POLITICAL
•There are available policies to implement the biosorption technology using sugarcane bagasse as an adsorbent in Nigeria.
ECONOMIC
•It is considered as less expensive and an economically viable method of lead extraction from waste water.
•Lead adsorption by maize cob adsorbent requires treatment of the adsorbent in other to achieve a desirable result. However, the treatment is done using EDTA and the chemicals may impose additional cost towards the project.
SOCIAL
•Reduces environmental pollution caused by maize cob wastes.
•It is perceived to be a totally acceptable technology due to its environmental friendliness and cost effectiveness compared to other conventional methods of lead extraction.
TECHNOLOGY
• Biosorption is a new technology that is yet to be implemented at an industrial level.
• It is perceived to be an easy and straight forward technology in reducing environmental impact caused by industrial processes.
Laiyemo, Michael A. 1123956
consider in the sense that a low equilibrium time shows that the reaction goes at a faster rate
and saves time spent on waste water treatment.
The equilibrium time of 10 minutes determined by Feng and Guo, (2012) shows good
efficiency unlike that determined by De Souza et al., (2012) which is 500 minutes. This
denotes a longer process for the research by De Souza et al., (2012) to achieve a 55.2mg/g
adsorption rate. But the best value obtained for the biosorption process was using NaOH-
CaCl2 treated orange peel which gave 209 mg/g adsorption capacity, 99.4% adsorption rate
and 10 minutes equilibrium time. This favourable values of the comparison parameters for
orange peel doesn’t mean it is better than the other adsorbent because according to a report by
Ngah and Hanafiah (2008), which stated clearly that chemically modified adsorbent may have
high adsorption capacity for metal ions but in other to realise the motive of obtaining a low
cost adsorbent, there has to be caution on the amount spent on modification chemicals and
treatment methods.
Desorption is the recoverability of the metal ion from the adsorbent and this is important for
the re-use of the adsorbent, to recover the metal for use in other manufacturing purposes and
lastly to avoid discarding the adsorbent and the adsorbed metal into the environment because
by doing so, it may generate into a more toxic substance and cause harm to the environment.
So very few literature reviews have discussed the desorption rate of lead adsorbed orange peel
except for De Souza et al., (2012) in which the desorption rate was as low as 35.9%.
4.5.1.2 Rice husk Amongst the few researchers that have carried out research on the use of rice husk adsorbent
for the removal of lead from aqueous solution, Wong, et al., (2003) gave the best result which
shows 108mg/g adsorption capacity, 93% adsorption rate of lead, and 120 minutes of
equilibrium time upon treatment of the rice husk with tartaric acid. There is no known amount
of desorption rate attached to lead binded rice husk. However, rice husk has limitations on its
use as adsorbent because of its availability in Nigeria. For an agricultural waste to be used as
an adsorbent for biosorption, it should be indigenous and readily available in the area where
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Laiyemo, Michael A. 1123956
the biosorption process is being implemented, and the adsorbent should have little or no
economic value.
Rice crop in Nigeria was discovered to be a crop of political importance because there is
inconsistency in the government policies concerning rice crop, this is a bid by the government
to favour some people of high calibre in the society. So this makes the local farmers to switch
to production of other crops and the only way to meet the country’s demand for rice is by
importation (Daramola 2005). Due to this reason, availability of rice husk becomes an aspect
to consider, because if there is a problem with rice importation in the future, obviously
shortage of rice husk occurs and this will hinder the progress of the biosorption technology.
4.5.1.3 Sugarcane bagasseLike other agro wastes, sugarcane bagasse is readily available in Nigeria because its crop
grows in the wide range of climatic condition present in Nigeria and sugarcane is the major
raw material for sugar production in Nigeria.
Unmodified sugarcane bagasse shows little adsorption capacity for lead from the study
conducted by Martín Lara, et al., (2010), however the best adsorption capacity was achieved
during studies conducted by Osvaldo, et al., (2007) whereby triethylene-tetramine was used to
modify sugarcane bagasse and adsorption capacity of 313mg/g was obtained with equilibrium
time of 50 minutes. The data obtained for sugarcane bagasse adsorption of lead shows that to
obtain the best efficiency of sugarcane bagasse as adsorbent, it has to be modified with
chemicals like citric acid or triethylene-tetramine. Citric acid modified bagasse gave a very
good desorption rate of 98%, implying that almost all the metal adsorbed by the bagasse were
recovered and liable for other processes in the industry but its equilibrium time is relatively
high compared to other adsorbents. There was no information gathered on the desorption rate
of lead adsorbed by triethylene-tetramine modified bagasse, in which if such information was
known and happens to be a high rate of desorption, then it will be a fair judgement to decided
that triethylene tetramine modified sugarcane bagasse is the best agricultural waste for
biosorption process in Nigeria.
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Nonetheless, the citric acid and triethylene tetramine modified bagasse biosorption process
where done using the same agricultural waste but the process conditions and the treatment
chemicals are different for both methods. In view of the foregoing, there is every possibility
that if more research is undertaken for the desorption rate of lead from the triethylene
tetramine modified bagasse, there is every possibility of achieving a high rate of metal
recovery
4.5.1.4 Maize cobStudies highlighted the importance of Nigeria to maize production in Africa, it was reported
by Akinfemi and Ladipo, (2011) that Nigeria is the second largest producer of maize in
Africa. For this reason, maize cob wastes should not be farfetched in the Nigerian
communities. Maize cob can be prepared into adsorbent for lead biosorption process but from
the data gathered, the best efficiency is achieved when maize cob is modified with a chelating
agent like ethylene diamine acetic acid (EDTA). Gathered from the report by Igwe and Abia,
(2007), EDTA modified cob gave adsorption capacity of 144.93mg/g with equilibrium time of
about 60 minutes. Investigation carried out by Nale, et al., (2012) whereby phosphoric acid
(H3PO4) was treated with maize gave a low adsorption capacity and also a study by
Jonglertjunya, (2008), in which natural fungi growth occurred on the surface of the cob and it
was used for lead biosorption gave adsorption capacity of 14.75mg/g.
A huge limitation for maize cob adsorbent is that data on other comparison parameters like
adsorption rate and desorption rate are not available in literature reviews.
4.5.2 Outcome of the PEST analysesDespite the pros and cons of each agricultural waste discussed during the SWOT analyses, the
PEST analyses was able to show that implementing each of the agricultural wastes in an
environmental pollution remediation process like biosorption, it is like killing two birds with a
stone because the process will reduce environmental pollution caused by the agricultural
wastes themselves and also reduce environmental pollution caused by lead metal.
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Nevertheless, the four methods are perceived to be socially acceptable by the public and
government because they are environmentally friendly and the methods show a reduction in
operating cost compared to other convention methods. A significant reason for the reduced
operating cost is because the agricultural wastes do not have economic values due to the fact
that they are readily available in the environment and also, processing industries like fruit
juice, sugar, and cereal manufacturing industries have these agricultural wastes in abundance.
So therefore these industries relieve their selves of disposal problems and the cost of involved
in disposing the agricultural wastes by utilizing the wastes in the biosorption process.
However, it was discovered that rice husk, sugarcane bagasse and maize cob require
treatments in other to modify their chemical and physical structure for better adsorption
capacities and rates.
These treatment methods involve the use of chemicals, reagents and heat, so therefore the
treatments incur additional cost on the process’s operating cost. But from another perspective,
the increased adsorption efficiency achieved from the modified agricultural wastes may offset
the cost incurred during treatment because more lead ions are adsorbed per unit mass of
adsorbent and there is little time spent on the process due to increase in adsorption rate of
lead and reduction in equilibrium time.
Pest analyses also showed the importance of metal recovery after the whole biosorption
process. If the method has a low desorption rate like orange peel, there is every possibility of
spending more money on further treatments and disposal of the saturated adsorbent and the
adsorbed lead.
Furthermore, there are established policies for implementing a technology like the biosorption
process in the Nigerian community. Moreover, the policies which were established by FEPA
(1991) have been discussed in chapter 2 of this study but in summary, it explains the
requirement by every industry to detoxicate effluents and chemicals coming out of the
industry into the environment. In addition, the policy requires the implementation of the best
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available technology (BAT) for the detoxification process, so this justifies the reason for
carrying out the study of identifying the best method for lead biosorption using agro wastes.
CHAPTER 5: CONCLUSION AND RECOMMENDATION
5.1 ConclusionAfter a brain storming SWOT and PEST analysis of the secondary data obtained, the best
method for lead removal from industrial effluent in Nigeria is by using triethylene tetramine
modified sugarcane bagasse as an adsorbent in a biosorption process.
Triethylene tetramine modified bagasse has the highest adsorption capacity of 313mg/g, with
the least equilibrium time of 50 minutes and because it has the tendency to achieve 98%
desorption rate just like citric acid modified bagasse if properly researched, it is therefore the
most cost efficient and reliable agricultural waste adsorbent for the biosorption of lead
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Based on the research done there are data gaps which suppressed the efficiency of the other
selected agricultural wastes compared to the modified sugarcane bagasse. However, it was
discovered that adsorption capacities of the agricultural wastes differ depending on their
treatment methods and the best adsorption capacities are achieved if the wastes are modified
with suitable reagents.
Missing in most of the analysis data obtained for the selected wastes are desorption and
adsorption rate of lead. Furthermore, there is need for more research on desorption and
adsorption rates of all the selected agricultural wastes in order to objectively decide which
method is the best for lead biosorption in Nigeria.
5.2 RecommendationThe proposed recommendations below will give some headway towards implementing
triethylene tetramine modified sugarcane bagasse biosorption technology by processing
industries in Nigeria;
Further studies are necessary in order to actually implement the biosorption technology
in industrial process units.
Workshops in the form of development programs should be initiated and it will make
people including government officials perceive the importance of using modified
sugarcane bagasse for the biosorption process and also it will reduce any tariff or
licence levy placed on the biosorption technology implementation.
Government funding should be sourced for further research on using the modified
sugarcane bagasse adsorbent for the biosorption technology. This will aid the
improvement in its design and its technology knowhow.
There should be more research done on the use of the other comparative agricultural
wastes for the biosorption process in order to achieve enhanced adsorption efficiency
with the wastes and to diversify the methods used for lead biosorption.
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Strict monitoring of industrial effluents discharged into receiving waters is necessary,
and the monitoring team should make sure there is compliance with the standard set by
the Nigerian government with heavy penalty imposed on violators.
Other sources of lead pollution in Nigeria should be identified and assessed for studies
on ways to prevent them from harming the environment.
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