International Journal of Engineering Technology Science and Research
IJETSR
www.ijetsr.com
ISSN 2394 – 3386
Volume 3, Issue 11
November 2016
Removal of Cr(VI) From Waste Water Using Root of
Eucalyptus Tree
Aparna Bhawnani1 and Dr. S.K.Gupta2
1
M.Tech scholar,Department of Chemical Engineering, H.B.T.U. Kanpur, India
2
Associate professor and Head, Department of Chemical Engineering, H.B.T.U. Kanpur, India
Abstract
Chromium (VI) is a highly toxic metal and its removal from effluent stream of industries is very important. Roots are the
part of plants that are not used because of their uneven shape and are a waste, so in present study these roots were used
to removal hexavalent chromium from Cr (VI) from waste water. In this study, roots were treated to produce highly
porous adsorbents to remove Cr (VI). The effect of three parameters was taken into account i.e. adsorbent dose, initial
concentration and contact time. The maximum removal efficiency was at lower concentrations. 5g/L of adsorbent dose
was found optimum. Kinetics of removal was fast as equilibrium was reached in 60 min. The equilibrium data fits
Langmuir isotherm successfully.
Keywords: Adsorption, Eucalyptus root, Langmuir Isotherm
Abbreviations
Co initial concentration of solution (mg/L)
Ce equilibrium concentration of solution (mg/L)
qeamount of heavy metal per unit mass of adsorbent( mg/g)
Vm monolayer capacity
k Langmuir constant
1.
Introduction
Chromium is a highly toxic metal that is being released from effluent streams of various industries such as
electroplating, tanning, metal finishing, nuclear power plant, textile industries and chromate preparation (Sarin
and Pant, 2006). Out of the two forms of Chromium, hexavalent Chromium is more toxic than the trivalent
Chromium. Human toxicity of Chromium(VI) includes lung cancer, as well as kidney, liver and gastric
damage.( Cieslak-Golonka 1995). Maximum permissible limit of Cr (VI) in drinking water is 0.05mg/L and in
surface water is 0.1mg/L ( Demirbas et al 2004) , so with these limits it is essential to remove this poisonous
metal from the effluent stream of industries .
Various methods are reported to remove heavy metals from waste water such as: Chemical precipitation, Ion
Exchange, Membrane filtration, Electro dialysis, Photo catalysis and Adsorption.(Barakat 2011). Out of all
these methods Adsorption proves to be low cost, efficient and easily operated method.
In the present study activated carbon is produced from root of Neem and Eucalyptus tree. Root of a plant
because of its uneven shape is a waste. So we are utilizing this waste to produce the activated carbon which
can adsorb Cr(VI). Activated carbon produced has high surface area than the raw dried form of root so it helps
in reducing the secondary sludge produced.
37
Aparna Bhawnani and Dr. S.K.Gupta
International Journal of Engineering Technology Science and Research
IJETSR
www.ijetsr.com
ISSN 2394 – 3386
Volume 3, Issue 11
November 2016
S.No.
Metal Removed
Adsorbent used
Reference
1.
Cr(VI)
Neem leaves powder
Sharma et al 2004
2.
Cr(VI)
Activated Neem leaves
Babu et al 2008
3.
Cr(VI)
Pineapple leaves
Ponou et al 2011
4.
Cr(VI)
Wool, olive cake, sawdust, pine needles, Dakiky et al 2002
almond shells, cactus leaves and charcoal
5.
Cr(VI)
Rice husk, sugar cane bagasse, Tulsi leaf and Shrivastava et al 2014
branches, coconut shell and coir, and flyash
6.
Cu(II) and Zn(II)
Natural Clay
Veli et al 2007
7.
Cu(II)
Sawdust
Larous et al 2005
8.
Cr(VI)
Eucalyptus bark
Sarin et al 2006
9.
Ni(II)
Baker’s Yeast
Padmavaty et al 2003
10.
Cr(VI)
Eucalyptus roots
Present study
2.
Materials and Methods
Preparation of adsorbents:Eucalyptus roots were collected from nearby village. The roots were washed
repeatedly with distilled water to remove dust and external impurities. The roots were then dried in a hot air
oven at 700C for 24-48 hours. The moisture was removed from the roots and the roots were grinded in a
grinder to get powder. This powder was treated with phosphoric acid (H3PO4) in the ratio of 1:1 by weight and
kept for digestion in hot air oven at 1050C for 1 hour. This mixture was kept in muffle furnace at 4500C for 1
hour. The activated carbon thus produced was washed with distilled water and 1N NaOH to bring the pH of
filtrate to 6, So that the free acid is removed. The washed activated carbon was dried in hot air oven at 100 0C
for 5 hours. The produced activated carbon is crushed, sieved and stored in dessicator.
Preparation of stock solution: A stock solution of Cr (VI) is prepared by dissolving 2.8287g of 99.9%
potassium dichromate ( K2Cr2O7) AR grade in 1000 ml of double distilled water to make 1000 ppm solution.
The stock solution is diluted to prepare various solutions of different concentration. If a solution of 100 ppm is
needed 10 ml of stock solution is diluted to 100 ml by distilled water.
Batch adsorption experiments: Firstly a known sample of chromium (VI) was prepared in a reagent bottle
and to it a fixed amount of adsorbent was added. The reagent bottle with adsorbent was kept in an orbital
shaker for a fixed amount of time and at fixed speed. After that time contents of the reagent bottle were
filtered using what-man filter paper No. 42. The residue on filter paper was dried and stored for further testing
and the filtrate was tested in UV spectrophotometer. Percentage removal was calculated.
% removal =
𝐶0 −𝐶𝑒
𝐶0
× 100%Where C0 is the initial concentration of the chromium solution in mg/L. And Ce is
the final concentration of chromium after adsorption which is determined from calibration curve on the basis
of absorbance in mg/L.
This way the whole experiment was repeated fixing some parameters and varying the others.
38
Aparna Bhawnani and Dr. S.K.Gupta
International Journal of Engineering Technology Science and Research
IJETSR
www.ijetsr.com
ISSN 2394 – 3386
Volume 3, Issue 11
November 2016
3.
Results and Discussions
Given below are SEM images of adsorbent produced at 1000x and 2000x magnification. The SEM images
show that the adsorbent produced has a honeycomb structure. The results from BET surface analyser show
that the structure is highly porous with high surface area and active sites.
BET Analysis
Surface area
Total pore volume
Mean pore diameter
1190m2/g
0.5952 cm3/g
2.004nm
% Removal
Effect of adsorbent dose
The effect of adsorbent dose on adsorption of Cr (VI) was studied at an ambient temperature of (30±2℃) on
100 mL solution of initial concentration 100ppm at a constant speed of 150 rpm. The contact time kept
constant at 40 min. the results obtained arepresented below. It is evident from the curve that the percentage
removal increases from 18.75% to 76.25%. The percent removal of chromium increases rapidly with increase
in adsorbent dose due to greater availability of active sites or more surface area at higher adsorbent dose. The
increase after 5g/L is negligible. Therefore optimum adsorbent dose is 5g/L.
90
80
70
60
50
40
30
20
10
0
0
1
2
3
4
5
Adsorbent Dose(g/L)
Effect of adsorbent dose for 100ppm for 40min at 150rpm
39
Aparna Bhawnani and Dr. S.K.Gupta
6
International Journal of Engineering Technology Science and Research
IJETSR
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ISSN 2394 – 3386
Volume 3, Issue 11
November 2016
Effect of metal concentration
The adsorption of hexavalent chromium on eucalyptus root is studied by varying initial metal concentration.
100 mL solutions of different concentrations (50ppm to 250ppm) are taken in series of reagent bottles and
optimum adsorbent dose of 5g/L is added to them. The ambient temperature of (30±2) ℃, contact time of 40
min and speed of 150rpm are kept constant. The results are signified in graphical form % removal vs initial
metal concentration. It is clear from the graph that % removal decreases with increase in initial metal
concentration due to the fact that at greater adsorbate concentration active sites become overloaded. At low
concentration, the ratio of sorptive surface area to total metal ions is high; so active sites have taken the metal
ions more quickly. The %removal decreases from 100% to 44%.
100
% removal
80
60
40
20
0
0
50
100
150
200
250
300
Concentration (ppm)
Effect of initial concentration at 5g/L for 40 min at 150rpm
Effect of contact time
Batch study of Chromium (VI) removal at different contact time is studied for 100 mL solution of initial metal
concentration of 100ppm , adsorbent dose of 5g/L, constant ambient temperature of 30±2℃ and shaking
speed of 150rpm. It was found that contact time of 60 min was necessary to reach the equilibrium for Cr (VI)
adsorption. A further increase in time didn’t show any significant increase in removal of hexavalent
chromium. The percentage removal increases from 60% to 88.5%.
100
% Removal
80
60
40
20
0
0
20
40
60
80
100
120
Time(min)
Effect of contact time of ER of 100ppm for dose of 5g/L at 150rpm
Adsorption isotherm
Langmuir isotherm models the single coating layer on adsorption surface. The attraction between molecules
decreases as getting away from the adsorption surface.(Unlu et al 2006). The results obtained from the
40
Aparna Bhawnani and Dr. S.K.Gupta
International Journal of Engineering Technology Science and Research
IJETSR
www.ijetsr.com
ISSN 2394 – 3386
Volume 3, Issue 11
November 2016
empirical studies were applied to Langmuir isotherm. The graph is plotted between Ce and Ce/qe. The data is
correlated with R2 value of 0.991.
The linearized form of Langmuir correlation is given by
𝑐𝑒
1
𝑐𝑒
=
+
𝑞𝑒
𝑘𝑉𝑚
𝑉𝑚
The obtained equations are as follows:
𝑐𝑒
= 0.2942 + 0.0438𝐶𝑒
𝑞𝑒
7
y = 0.043x + 0.294
R² = 0.991
6
Ce/qe
5
4
3
2
1
0
0
20
40
60
80
100
120
140
160
Ce
4.
Conclusion
The produced adsorbent is of high surface area and efficiently removes Cr (VI) from the synthetic waste
water. % removal is relatively high at lower concentrations than at higher concentrations. 5g/L of adsorbent
dose was found optimum. Maximum removal efficiency was found to be 99.8% for 50ppm solution. At higher
concentration too the removal was significant. Therefore Eucalyptus roots prove to be a good and low-cost
adsorbent for Cr(VI) removal.
References
1.
2.
3.
4.
5.
6.
7.
8.
9.
Arunima Sharma, Krishna G. Bhattacharya. Adsorption of chromium (VI) on AzadirachtaIndica(Neem) Leaf
powder. Kluwer Academic Publishers. 327-338. 2004
B.V.babu ,S.Gupta Adsorption of Cr(VI) using activated neem leaves: Kinetic studies. Springer. 85-92.2007
JosianePonou, Jungah Kim, Li pang wang, GjergjDodbiba, Toyohisa Fujita. Sorption of Cr(VI) anions in aqueous
solution using carbonized or dried pineapple leaves. Chemical Engineering Journal 172. 906-913.2011
M.A. Barakat,.New trends in removing heavy metals from industrial wastewater. Arabian journal of chemistry, 361377.2011
M. Dakiky, M.Khamis, A.Manassra, M.Mer’eb. Selective adsorption of chromium (VI) in industrial waste water
using low-cost abundantly available adsorbents. Advances in Environmental Research. 533-540. 2002.
Prashant Kumar Srivastava and S.K.Gupta . Removal of chromium from waste water by Adsorption method using
Agriculture waste materials. International journal of chemical sciences and applications.2014.
SevilVeli and Bilge Alyuz. Adsorption of copper and zinc from aqueous solutions by using natural clay. Journal of
Hazardous Materials 149. 226-233. 2007
S.Larous, A.-H. Meniai, M.BencheikhLehocine. Experimental study of the removal of copper from aqueous
solutions by adsorption using sawdust. Desalination 185. 483-490. 2005.
Vikrant Sarin, K.K. Pant. Removal of chromium from industrial waste by using eucalyptus bark. Bioresource
Technology, 15-20.2006
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Aparna Bhawnani and Dr. S.K.Gupta
International Journal of Engineering Technology Science and Research
IJETSR
www.ijetsr.com
ISSN 2394 – 3386
Volume 3, Issue 11
November 2016
10. V. Padmavathy, P.Vasudevan, S.C. Dhingra. Biosorption of Nickel(II) ions on Bakers’s yeast. Process Biochemistry
38. 1389-1395. 2003
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Aparna Bhawnani and Dr. S.K.Gupta