Use of Agricultural Waste for Removal of Heavy Metals

8/22/2019 Use of Agricultural Waste for Removal of Heavy Metals

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8th

April, 2013

USE OF AGRICULTURAL WASTE FOR THE REMOVAL OF

HEAVY METALS

SUBMITTED BY

Mohammad Haseeb Azam

Student ID: 20500531

A Term paper submitted in Partial fulfillment of the

Requirements of

CHE 674 (Industrial Wastewater Pollution Control) Course

Chemical Engineering Department

University of Waterloo


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Table of Contents

1. INTRODUCTION.......................................................................................................................... 3

2. REMOVAL OF CR (VI) FROM AQUEOUS SOLUTION........................................................... 4

2.1 Materials................................................................................................................................. 5

2.2 Results and discussion............................................................................................................ 5

2.2.1 Effect of Contact Time..................................................................................................... 5

2.2.2 Effect of initial Cr (VI) concentration............................................................................. 6

2.2.3 Effect of pH..................................................................................................................... 7

2.2.4

Effect of Temperature...................................................................................................... 7

2.2.5 Effect of particle size....................................................................................................... 8

2.3 Adsorption Isotherm............................................................................................................... 9

2.4 Adsorption Kinetics Modelling............................................................................................. 12

2.4.1 Pseudo-first-order model.............................................................................................. 13

2.4.2 Pseudo-second-order model......................................................................................... 13

2.5 Fourier transform infrared analysis (FT-IR)......................................................................... 15

3. BIOSORPTION OF HEAVY METALS BY PAPER MILL WASTE ......................................... 16

3.1 Materials and Method........................................................................................................... 17

3.1.1 Chemicals and reagents................................................................................................ 17

3.1.2 Preparation of Biosorbent............................................................................................ 17

3.2 Results and Discussion......................................................................................................... 17

3.2.1 Effect of pH on the removal of the heavy metal ions.......................................................... 17

3.2.2 Effect of Biomass concentration.................................................................................... 18

3.2.3 Effect of contact time and initial concentration of metal ions on % removal............... 18

3.3 Adsorption Isotherm............................................................................................................. 21

4. CONCLUSION............................................................................................................................. 23

5. REFERENCES............................................................................................................................. 25


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1. INTRODUCTIONToday, with the rapidly increasing population, water resources becoming scarcer, there is a

strong need to reconsider the patterns of our consumption and the way we use our water

resources(1). Heavy metals have been excessively released into the environment due to rapid

industrialization and have created a major global concern (2). Ecological systems around the

world are at risk from human activities. These delicate systems need to be conserved so that

we dont disturb the natural balance of processes and therefore continue to make the earth a

Greener Planet.

The pollutants in the waste water are classified into two main types: (I) Organic Pollutants,

which can easily biodegrade and present a low risk factor. (II) The other type is the Non-

Organic Pollutants, which also contain the Heavy Metal Ions. These heavy metals do not

biodegrade into harmless end products and therefore are the main contributors toward

contamination. Moreover, these heavy metals ions are a big concern in the waste water due

their toxicity. Much of the aquatic life is badly affected due the high quantities of the metal

ions being present in this water, and many water-borne diseases have posed serious risk to the

general public. Strong exposure of Cr (VI) causes cancer in the digestive tract and lungs and

may cause epigastric pain, nausea, vomiting, severe diarrhoea, and haemorrhage (3). The

higher concentration of Ni (II) in ingested water may cause severe damage to lungs, kidneys,

gastrointestinal distress, e.g., nausea, vomiting, diarrhoea, pulmonary fibrosis, renal edema,

and skin dermatitis(4).

Metal contaminated waters may contain ions of copper, zinc, nickel, lead, cadmium, mercury,

chromium and uranium; originating from industries like metal plating, tanneries, mining

operations, smelting, alloy industries, textiles, microelectronics, petroleum refining,

pesticides and battery manufacture.


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Conventional bioremediation technologies viz. precipitation-filtration, ion exchange, reverse

osmosis, oxidationreduction and membrane separation are not economical and inadequate to

bring down the level of contaminants in wastewater to permissible. Further, these traditional

protocols generate huge quantity of noxious chemical sludge (5). Adsorption technology by

activated carbon has gained wide acceptance and patronage among researchers, more than

any other form of wastewater treatment technologies, due to their low cost, simplicity, ease of

implementation and effective removal of heavy metals at trace level in effluent streams or

wastewater (6). The other technique widely used is Biosorption. Biosorption is an innovative

technology using living or dead biomasses to remove toxic heavy metals from aqueous

solution. The major advantages of biosorption technology are its effectiveness in reducing the

concentration of heavy metal ions to very low levels and the use of inexpensive biosorbent

material(7).

Low cost agricultural waste by-products such as sugar cane bagasse, rice husk, saw dust,

coconut husk, oil palm shell, neem bark have been investigated for use as novel adsorbents.

Agricultural wastes are characterized by ready availability, affordability, ecofriendliness and

high uptake capacity for heavy metals due to the presence of functional groups which can

bind metals to effect the removal of heavy metal from effluents(8).

2. REMOVAL OF CR (VI) FROM AQUEOUS SOLUTIONChromium exists in either +3 or +6 oxidation states, as all other oxidation states are not stable

in aqueous systems. Chromium (VI) is 100-1000 times more toxic to organisms than Cr (III)

and more readily transported in soils (3).

The main industrial sources of chromium pollution are leather tanning, electroplating, metal

processing, wood preservatives, paint and pigments, textile, dyeing, steel fabrication and

canning industry(3).


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In this case, Adsorption technique is employed for the removal of Cr (VI) ions from waste

water. This study encompasses the use of activated carbon, almond and apricot shells as

adsorbent for Cr (VI) to determine adsorption efficiency as a function of contact time, initial

concentration, particle size, pH, temperature and constants of adsorption isotherm.

2.1 MaterialsAlmond and apricot shells were collected from different sites and prepared from agricultural

solid wastes as adsorbents. The samples were washed several times with deionized water and

dried under the sun. After this the adsorbents were ground in a blender and stored for further

use. Potassium dichromate and other chemicals were used of analytical reagent grade and

were obtained from standard sources(3).

The physical properties of activated carbon have been listed in Table 1.

Table 1: Physical Properties of activated carbon*(3)

2.2 Results and discussion2.2.1 Ef fect of Contact TimeThe figure below (Figure 1) shows the adsorption of Cr (VI) by almond shell, apricot shell

and activated carbon as a function of time. From the figure it can be clearly seen that rapid

adsorption took place in the initial 15 min for all biosorbent but then adsorption gradually


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decreases with time until it reaches equilibrium. Further increase in contact time did not show

an increase in biosorption (3).

Figure 1: Effect of contact time on the removal of Cr (VI)

(3)

2.2.2 Ef fect of ini tial Cr (VI ) concentrationFig. 2 shows the effect of Cr (VI) concentration on the sorbent by varying the initial Cr (VI)

concentration (0.5, 1, 2, 4 and 5 mg/l) for a 30 min time interval. It was observed that the

percentage removal decreased with increase in Cr (VI) concentration. At low concentrations

the ratio of available surface to the initial Cr (VI) concentration is larger, so the removal

becomes independent of initial concentrations. However, in the case of higher concentrations

this ratio is low; the percentage removal then depends upon the initial concentration (3).

Figure 2: Effectof Initial Cr (VI) concentration on the removal of Cr (VI)(3)


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2.2.3 Ef fect of pHOne of the most important controlling parameter in the adsorption process is pH. The results

indicate that adsorption of Cr (VI) was higher at lower pH and decreased with increasing pH

(Fig. 3). Also, the results show the optimum initial pH which was observed at pH 2.0.

Removal of Cr (III) at pH 2.0 is zero whereas its removal percentage is very high at pH 5.0;

however, percentage removal of Cr (VI) is significantly low. At low pH values active sites

are positively charged. Therefore, negative metals adsorption increases significantly whereas

increasing the pH value causes the surface of the adsorbent to become neutral and hence a

decrease in the adsorption is observed.

Figure 3:Effect of pH on the removal of Cr (VI)

2.2.4 Ef fect of TemperatureAdsorption is normally considered an exothermic process; therefore you would expect the

equilibrium concentration to increase (i.e. the amount of adsorbed material decreases) with

increasing temperature. But some chemical adsorption processes are endothermic processes;


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therefore, increase in temperature leads to increase in both adsorption rate and amount of

adsorbed materials(3). This was the case observed in this study.

As shown below (Fig. 4), adsorption of Cr (VI) at different temperatures showed an increase

in adsorption capacity with increase in temperature.

Figure 4:Effect of temperature on the removal of Cr (VI) (3)

2.2.5 Ef fect of part icle sizeFig. 5 shows the effect of particle size on the Cr (VI) adsorption capacity of almond shell,

apricot shell and activated carbon. It is apparent from Fig. 5 that the particle size of sorbents

has a considerable effect on Cr (VI) sorption. The larger sorbent size shows lesser Cr (VI)

removal as compared to the smaller sorbent size. This can be inferred from the available

surface area for adsorption which decreases as the particle size increases for the same dose or

sorbent, providing less active surface sites for adsorption of sorbate.


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Figure 5: Effect of particle size on the removal of Cr (VI) (3)

2.3 Adsorption IsothermAdsorption equilibrium data were fitted to the Langmuir, Freundlich and Temkin isotherms.

Langmuir isotherm is based on the monolayer adsorption of chromium ions on the surface of

absorbent sites and is expressed in the linear form as (3):

Where Ce is the equilibrium solution concentration, x/m the amount adsorbed per unit mass

of adsorbent, m the mass of the adsorbent, Vm the monolayer capacity, and Kis equilibrium

constant related to the heat of adsorption by equation:

Where, qis the heat of adsorption.


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The other common type of adsorption isotherm used for waste water analysis and calculations

is the Freundlich isotherm. This describes the heterogeneous surface energies by multilayer

adsorption and is expressed in linear form as:

Log Log+

Log Ce

Where,

Kfand 1/n are Freundlich constants related to adsorption capacity and intensity of adsorption,

and other parameters are the same as in the Langmuir isotherm.

Finally, Temkin isotherm is based on the heat of adsorption of the ions, which is due to the

adsorbate and adsorbent interactions taken in linear form, is given by(3):

(

) (

)

Where,

b= Temkin Constant- Related to heat of adsorption (J/mol),

A= Temkin isotherm constant (L/g),

R= Gas constant (8.314 J/mol K),

T= Absolute temperature (K)

The theoretical parameters of the above three isotherms along with regression coefficient

have been given in Table 2.


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Table 2:Isotherm constants for various adsorption isotherms(3)

Figs. 6, 7 and 8 show the comparison of the three isotherms with each other. The results

indicate that the Freundlich equation fits the experimental data better than the Langmuir and

Temkin equations(3).

Figure 6:Equilibrium isotherms of Cr (VI) onto almond shell(3)


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Figure 7: Equilibrium isotherms of Cr (VI) onto activated carbon(3)

Figure 8: Equilibrium isotherms of Cr (VI) onto apricot shell(3)

2.4 Adsorption Kinetics ModellingKinetic modelling of the different adsorbents is carried out to determine the potential rate-

controlling steps involved in the process of biosorption. In this study, pseudo-first-order and

pseudo-second-order kinetic models have been tested for each of the adsorbents (i.e. almond

shell, apricot shell and activated carbon).


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2.4.1 Pseudo-f ir st-order modelThe pseudo-first-order kinetic model was described by Lagergren(3):

Where qe(mg g-1) and qt (mg g

-1) are the amounts of the Cr (VI) adsorbed on the adsorbent at

equilibrium and at time t, respectively; and k1 (min-1) is the rate constant of the first order

model. After integrating the above equation and applying boundary conditions, it can be

expressed as follows:

ln (qe- qt) = lnqe k1t

It is important that that the experimental qemust be known for the application of this model.

The pseudo-first-order constants, qe and k1, along with the corresponding correlation

coefficients for initial Cr (VI) concentration of 5 ppm are shown in Table 3.

The calculated qecal value is not in good agreement with the experimental value of qeexp.

These observations suggest that the pseudo-first-order model is not suitable for modelling the

adsorption of Cr (VI) onto almond shell, apricot shell and activated carbon(3).

2.4.2 Pseudo-second-or der modelThe pseudo-second-order model is based on the assumption that the rate-limiting step is

chemical sorption or chemisorption involving valance forces through sharing or exchange of

electrons between sorbent and sorbate as covalent forces (3). The equation of this model can

be expressed in the following form:


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Where k2(g mg-1min-1) is the rate constant of the second-order equation; qe (mg g-1) is the

maximum adsorption capacity; qt (mg g-1) is the amount of adsorbed at time t (min).

After integrating and applying boundary conditions, the above equation will yield:

Values of K2 and qe calalong with the corresponding correlation coefficients for the initial Cr

(VI) concentration of 5 ppm are presented in Table 3.

The correlation coefficient was nearly equal to unity and calculated qe calvalue was very close

to the experimental value of qe exp. The results indicated that the pseudo-second-order

adsorption mechanism is predominant for the adsorption of Cr (VI) onto almond shell, apricot

shell and activated carbon, and it is considered that the rate of the Cr (VI) adsorption process

is controlled by the chemisorption process(3).

Table 3: Calculated kinetic parameters for pseudo first-order and second-order kinetic

models for the adsorption of Cr (VI)(3)


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2.5 Fourier transform infrared analysis (FT-IR)Fourier transform infrared spectroscopy is a very useful technique to determine the changes

in the functional groups and surface properties of the adsorbent (4). The FT-IR spectra of

almond and apricot shells before and after adsorption of chromium have been given in Figs.

9-12. The spectra were measured within the range of 500-4000 cm-1wave number.

The results of the FT-IR spectra clearly indicate that were various functional groups detected

on the surface adsorbents before and after adsorption. These results are presented in Table 4.

As seen in Table 4, these band shifts indicated that it was the bonded OH groups and

aliphatic CH groups in particular which played a major role in chromium (VI) biosorption

on almond shell(3).

Table 4:Some fundamental frequencies of the studied adsorbents (before and after use) (3)

Figure 9:The FT-IR spectra of almond Figure 10:The FT-IR spectra of almond

shell before adsorption(3) after adsorption(3)


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Figure 11:The FT-IR spectra of apricot Figure 12:The FT-IR spectra of apricot

shell before adsorption(3) after adsorption(3)

3. BIOSORPTION OF HEAVY METALS BY PAPER MILL WASTEBiosorption is a relatively new process that has shown a significant contribution for the

removal of contaminants from aqueous effluents. Biosorption can be defined as the removal

of metal or metalloid species, compounds and particulates from solution by biological

materials or a by-product or waste material from another industry(9).

Both living and dead biomass as well as cellular products such as polysaccharides can be

used for metal removal (9). The process of biosorption involves a solid phase (sorbent) and a

liquid phase (solvent) containing a dissolved species to be sorbed. Due to the high affinity of

the sorbent for the metal ion species, the latter is attracted and bound by a rather complex

process affected by several mechanisms involving chemisorption, complexation, biosorption

on surface and pores, ion exchange, chelation, biosorption by physical forces, entrapment in

inter and intrafibrillar capillaries and spaces the structural polysaccharide networks as a result

of the concentration gradient and diffusion through cell walls and membranes(10).


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3.1 Materials and Method3.1.1 Chemicals and reagentsThe stock solutions were prepared by dissolving lead nitrate, cadmium iodide, nickel sulphate

and copper sulphate respectively in milli Q water; each containing 1000 mg l-1concentration

of lead, cadmium, nickel and copper.

3.1.2 Preparation of B iosorbentThe paper mill sludge used in this study is collected from the filter bed of effluent treatment.

It is mainly composed of primary clarified sludge (Kraft pulp & paper based mill). The

sludge is first washed with distilled water to remove the particulate matter before carrying out

the metal adsorption experiments. The sludge is oven-dried at 100oC overnight, pulverized

and stored in a polyethylene bag for further studies.

3.2 Results and Discussion3.2.1 Ef fect of pH on the removal of the heavy metal ions

The effect of pH is given in Fig. 13. It can be clearly seen that the maximum removal took

place at pH 4.5. This indicates that the maximum adsorption affinities take place in

moderately and slightly acidic medium (1).

Figure 13:Effect of pH on the % removal of different metals by paper mill waste(1)


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3.2.2 Ef fect of Biomass concentrationEach of the metals exhibited similar behaviour with change in biomass concentration.

Biosorption of each metal was found to be better with 1% concentration of biomass. The

results are presented in Fig. 14.

Figure 14:Effect of Biomass concentration (w/v) on the % removal of different metals (1)

3.2.3

Ef fect of contact time and ini tial concentration of metal ions on % removal

The results showed some analogous characteristics; adsorption was sharp and up to 70%-89%

of the metal ions were adsorbed within 15 minutes from 100 mg l -1 and 5 mg l-1 initial

concentration respectively. Though Cd, Cu at 50 mg l-1and Pb, Ni at 20 mg l-1

showed a

decrease in absorption in the first 15 minutes, with increase in contact time the adsorption

increased. At equilibrium, adsorption was 99.8% of Ni, 98.0% of Pb, 99.2% of Cu and 99.8%

of Cd by dried paper mill sludge with an initial conc. of about 5 mg l-1of aqueous solution(1).

Even though at higher initial concentration i.e. from 10-100 mg l-1of metals, the adsorption

decreased but it was well above 90% (Fig. 15-18).


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Figure 15: Effect of initial concentration (Ci) of Cd with time of agitation on residual

concentration(1)

Figure 16: Effect of initial concentration (Ci) of Cu with time of agitation on residual

concentration(1)


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Figure 17:Effect of initial concentration (Ci) of Pb with time of agitation on residual

concentration(1)

Figure 18:Effect of initial concentration (Ci) of Ni with time of agitation on residual

concentration(1)


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3.3 Adsorption IsothermBiosorption of heavy metals is a rapid process and equilibrium is established between the

adsorbed metal ions on the surface of the adsorbent (qeq

) and unadsorbed metal ions in

solutions (Ceq)(1).

Langmuir and Freundlich adsorption constants evaluated from isotherms and correlation

coefficients (R2) are given in Table 5. The results clearly indicate that both physico-chemical

adsorption and ion exchange interaction plays a role in binding of lead, copper, nickel and

cadmium from aqueous solution simultaneously. Paper mill sludge is composed of both

organic and inorganic constituents therefore mechanism of adsorption involves both ion

exchange interactions as well as physico-chemical adsorption.

The equilibrium constants of Langmuir and Freundlich adsorption models for each of the

metals (Lead, Nickel, Copper and Cadmium) show a good correlation when compared with

the experimental data, resulting in ( which shows that Freundlich sorption modelfitted well as compared to Langmuir adsorption model throughout the concentration range of

Pb, Ni, Cu and Cd. However, the results show that Cd has favoured Freundlich model

relatively more than the Langmuir.

Table 5:Values of Langmuir and Freundlich adsorption constants evaluated from isotherms

and correlation coefficients (R2).(1)


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Table 6 gives a brief comparison of the biosorption capacity of some agricultural wastes

which can be used as cheap adsorbents.

Table 6:Selected heavy metal adsorption capacities for selected low cost adsorbents

(1)


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4. CONCLUSIONThe removal of heavy metals from waste water/effluent streams has gained much attention

around the world due to the fatal effects of these metals and water becoming a scarce

resource in many parts of the world. Agricultural wastes being economical and readily

available make very good use as adsorbents. However, its extremely important to make sure

that these agricultural wastes are treated or modified before use if necessary in order to

ensure that minimum amount of waste sludge is formed.

The two most common methods for the removal heavy metals have been discussed above. In

the first case adsorption technique was adopted which investigated the use of almond and

apricot shells as effective and inexpensive biosorbents. In the latter case, biosorption

technology was used for the removal of heavy metals. Both of these removal methods depend

on specific parameters such as temperature, pH, initial biomass/metal concentration, contact

time, particle size etc for metal removal efficiency. The Langmuir and Freundlich adsorption

models can be used to represent the experimental data and compare the adsorption capacities.

Adsorption kinetics modelling can be used to determine the rate controlling steps involved in

the biosorption process.

In biosorption technology, living or dead biomass is used to accumulate heavy metals and

this finds a major drawback of cost of growing sufficient quantity of bacterial fungal or algal

biomass. One of the solutions to this problem is to use biomass of another industry for the

development of inexpensive biosorbent. Further physico-chemical characterization of

biomass and application in continuous system should be taken into account for future

research. In addition, more stress should be given on recycling and re-use of biosorbents and

the safe disposal of any toxic sludge produced.

Finally, to conclude, the removal of heavy metals from waste water streams is efficient and

economical if carried out using appropriate methods; hence it is important to employ this


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research at grass root levels in developing countries too where majority of the population

does not have access to safe water supplies.


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5. REFERENCES1. Biosorption of heavy metals by paper mill waste from aqueous solution. Suryan S,

Ahluwalia S.S.: International Journal of Environmental Sciences, 2012, Vol. 2 (3), pp. 1331-

1343.

2. Removal of heavy metal ions from wastewater by chemically modified plant wastes as

adsorbents: A review. W.S. Wan Ngah, M.A.K.M. Hanafiah.: Bioresource Technology,

2008, Vol. 99, pp. 3935-3948.

3. Use of Agricultural Waste for Removal of Cr(VI) from Aqueous Solution. Khazaei, M.

Aliabadi, H. T. Hamed Mosavian.: Iranian Journal of Chemical Engineering, 2011, Vol. 8(4), pp. 11-23.

4. Use of Agricultural Waste for the Removal of Nickel Ions from Aqueous Solutions:

Equilibrium and Kinetics Studies. Manjeet Bansal, Diwan Singh, V.K.Garg and Pawan

Rose.: International Journal of Civil and Environmental Engineering, 2009, Vol. 1 (2), pp.

108-114.

5. Potential of fruit and vegetable wastes as novel biosorbents: summarizing the recent

studies. Patel, Seema.: Rev Environ Sci Biotechnol, 2012, Vol. 11, pp. 365-385.

6. Potential application of activated carbon from maize tassel for the removal. O.F.

Olorundare a, R.W.M. Krause a, J.O. Okonkwo b, B.B. Mambaa.: Physics and

Chemistry of the Earth, 2012 Vols. 50-52, pp. 104-110.

7. Agricultural Waste materials as potential adsorbent for removal of heavy metals from

aqueous solutions. Alfa, Y. M., Hassan H. and Nda-Umar U. I.: International Journal of

Chemical Resources, 2012, Vol. 2 (1), pp. 48-54.

8. Comparative analysis of the efficiencies of two low cost adsorbents in the removal of

Cr(VI) and Ni(II) from aqueous solution. O. Olayinka Kehinde, T. Adetunde Oluwatoyin,

and O. Oyeyiola Aderonke.: African Journal of Environmental Science and Technology,

2009, Vol. 3 (11), pp. 360-369.


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9. Modified barley straw as a potential biosorbent for removal of copper ions from aqueous

solution. E. Pehlivan, T. Altun, S. Parlayici.: Food Chemistry, 2012, Vol. 135 (1), pp.

22292234.

10. Heavy metal uptake by agro based waste materials. Qaiser. S, Saleemi A. Anwar,

Ahmad. M Muhammad.: Electronic Journal of Biotechnology, 2008, Vol. 10 (3), pp. 409-

416.

11. Removal of Nickel ion from Industrial Waste Water using Maize Cob. Muthusamy P.,

Murugan S. and Manothi Smitha.: ISCA Journal of Biological Sciences, 2012, Vol. 1 (2),

pp. 7-11.

12. Agricultural waste as a low cost adsorbent for heavy metal removal from wastewater. J.

N. Egila, B. E. N. Dauda, Y. A. Iyaka and T. Jimoh.: Academic Journals, 2011,

International Journal of the Physical Sciences, Vol. 6 (8), pp. 2152-2157.

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Use of Agricultural Waste for Removal of Heavy Metals