Abstract- This paper reports the high biosorptive properties of an indigenous plant for Cr(VI) biosorption. The biomass uptake capacity is found 85 mg Cr(VI)/gm of biomass in batch mode. The influence of different experimental parameters such as pH, dose of adsorbent and Cr(VI) levels (15-200 mg/l), effect of contact time etc. on biosorption was evaluated. The adsorption data fitted well to Langmuir and Freundlich isotherm models. Kinetic experiments revealed that the dilute chromium solutions reached equilibrium within 120 minutes. It was observed that the pH had a strong effect on biosorption capacity. Desorption of Cr(VI) was successfully carried out by 0.1 N hydrochloric acid. The interference study of metals like Mn, Fe, Cu, Cd, Mo, Ni, Pb, As, Co (10mg/l) was investigated. Cd showed negative interference in this investigation.

Keywords: Chromium(VI), biosorption, parameters,

adsorption, batch mode adsorption.

I. INTRODUCTION Exposure to Cr(VI) causes cancer in digestive tract and

lungs [1]. Cr(VI) is very toxic in nature. Exposure to Cr(VI) affects human beings, plants, animals and as well as ecosystem. Hence removal of Cr(VI) is essential and important [2]. The untreated effluent from electroplating industry contains approximately 100 mg/l Cr(VI), which is much higher than the permissible limit of 0.05 - 1mg/l [3]. According to USEPA, the discharge of Cr(VI) and its other forms is regulated [4] to below 2 mg/l. Cr(VI) is introduced into the environment through industrial discharges from electro plating, leather tanning, glass, ceramic paints and canning industries [5]. The commonly used procedures for removing metal ions from effluents include chemical precipitation, lime coagulation, ion exchange, reverse osmosis and solvent extraction [6]. These processes may be ineffective or expensive, especially when the heavy metal ions in the contaminated media are high i.e. in order of 1- 100 mg dissolved heavy metal ions/l [7]. Biological methods such as biosorption / bioaccumulation may provide an attractive alternative to physico-chemical methods for the removal of heavy metal ions [8]. Many biosorbents such as wool, rice, straw, coconut husks, peat moss, exhausted coffee [9], waste tea [10], walnut skin, coconut fibre, [11], cork biomass [12], seeds of Ocimum basilicum [13], defatted rice bran, rice hulls,

soybean hulls and cotton seed [14], seed cakes, [15] and mustard seed cakes, [16] were used for metal sorption.

II. BIOSORPTION STUDIES The biosorption capacity of biomass was determined by

contacting various concentrations (15-200mg/l) of 50 ml Cr(VI) solution in 250 ml conical flasks, with 1 gram of biomass. The filtrate containing the residual concentration of Cr(VI) was determined spectrophotometrically at wavelength 540 nm after complexation with 1,5 diphenylcarbazide [17]. For the determination of rate of metal biosorption by biomass

soybean hulls and cotton seed [14], seed cakes [15], and mustard seed cakes [16], were used for metal sorption.

. BIOSORPTION STUDIES The biosorption capacity of biomass was determined

by contacting various concentrations (15-200mg/l) of 50 ml Cr(VI) solution in 250 ml conical flasks, with 1 gram of biomass. The filtrate containing the residual concentration of Cr(VI) was determined spectrophotometrically at wavelength 540 nm after complexation with 1,5 diphenylcarbazide [17]. For the determination of rate of metal biosorption by biomass of plant from 50 ml, the supernatant was analysed for residual Cr(VI) after the contact period of 15, 30, 45, 60, 120, 1440 minutes. The effect of pH on Cr(VI) sorption by biomass was determined at pH values of 1, 1.5, 2, 2.5 and 3. The effect of different doses of biomass 0.2, 0.5, 0.7, 0.9, 1, 2, 3, 4, 5 gm were studied.

III. DESORPTION STUDIES Desorption study was carried out to account for the mass

balance of Cr(VI) in the system. For this the loaded biomass after a single exposure to the known amount of Cr(VI) was carried out using 0.1 N hydrochloric acid for desorption. The result shows that about 85% of the adsorbed amount of Chromium could be leached easily.

IV. RESULT AND DISCUSSION

A. Effect of pH The pH of the aqueous solution is an important controlling

parameter in the adsorption process. The pH was adjusted by adding 1N HCl or 0.1M NaOH. The effect of pH (1-3) was studied using biomass on the removal of Cr(VI) for a constant biosorbant dosage of 1g/50 ml, standing time 120 minutes. Maximum adsorption of 90 mg/l Cr(VI) was shown at pH 1 and a rapid decrease in the adsorption of metal was observed while increasing the pH of the solution.

Efficient Biosorptive Removal of Chromium(VI) Dr. Piyush Kant Pandey Dr. Madhurima Pandey Mrs. Rekha Sharma

Bhilai Institute of Technology, Bhilai Institute of Technology, Shri Shankaracharya Institute of Raipur, C.G., India. Durg, C.G., India. Technology and Management Bhilai, C.G., India drpiyush_pandey@yahoo.com drmadhurima_pandey@yahoo.com rekha.sharma.ssitm@gmail.com

1203978-1-61284-459-6/11/$26.00 ©2011 IEEE

B. Effect of contact time The contact time was varied from 15 to 1440 min. On

increasing the contact time, the percentage removal of 90 mg/l of Cr(VI) was found to gradually increase till 120 min. Hence, the optimum contact time for chromium removal was 120 minutes. At 120 min. the metal removal is 92.22 % which remain constant up to 1440 minutes. For the optimization of other parameters, the contact time of 120 min. was considered as the equilibrium time.

C. Effect of dosage of adsorbent The percentage removal of 90mg/l of chromium

concentration with varying amounts of adsorbent biomass ranging from 0.2-5g was examined in this experiment. The removal of Cr(VI) was complete at 4 gram dose of the biomass. However 1.0 gram of the biomass showed almost complete removal hence, further experiments were carried out at the dose of 1g.

D. Batch interference studies The interference study of metals like Mn, Fe, Cu, Cd,

Mo, Ni, Pb, As, Co (10mg/l) was investigated. Cd shows negative interference in this investigation.

E. Study on the adsorption kinetics Observation revealed a linear trend on [18] plot log (qe-

q) against time following the first order of adsorption kinetics for the adsorption of Cr(VI) onto the biomass. In this kinetic study the experiment was conducted in the concentration of chromium was 90 mg/l (where time varied from 15 min. to 120 min. at 25°C). Results showed that the amount of chromium adsorbed q (mg/g) increased and log (qe-q) decreased from 15 min. to 120 minutes. whereas from 120 min. to 240 min. q (mg/g) decreased and log (qe-q) increased. The value of co-relation coefficient R2 is greater (0.91) than (0.90) showing the effect of time on adsorption process before and after equilibrium time.

F. Sorption equilibria studies The linear plots of Ceq/q vs Ceq show that adsorption

follows the Langmuir adsorption model. The essential characteristics of the [19] can be expressed in terms of a dimensionless constant separation factor or equilibrium parameter, RL, which is defined as

RL = 1/(1+bCo)

Where b is the Langmuir constant and Co is the initial concentration of Cr(VI). According to [20], RL values between 0 and 1 indicate favourable adsorption. The RL were found to be 0.69 to 0.67.

Kf (1.380) and n (9.56) were calculated from the slopes of the Freundlich plots According to [21], n values between 1 and 10 represent beneficial adsorption.

V. INTERPRETATION OF FT-IR SPECTRA

The interpretation of infrared spectra showing the different frequency peaks on unloaded biomass which are chemically different in loaded biomass. The identification of absorption spectrum shows the range, type, vibration and functional groups of the biomass. FT-IR study of unloaded biomass (figure.1) and loaded biomass (figure.2) shows a major differences in the region 1373-1158 cm-1 range and shifting of peaks around 3300-1615 cm-1 is assigned to -NH2 groups in different parts of the biomass. Frequency ranges of biomass indicating bonding of Cr(VI) with the amines groups of biomass. Hence, based on FT-IR spectrum analysis it can be conclude that the metal binding in the biomass takes place by the substitution of amine groups.

Figure 1. FT-IR Spectra of unloaded form of biomass

Figure 2. FT-IR Spectra of loaded form of biomass

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VI. CONCLUSIONS This indigenous plant species is found to be good

adsorbent for the toxic hexavalent form of chromium. In most of the removal technique, chemicals are added to reduce toxic Cr(VI) to low toxicity Cr(III). The selected biomass show the direct adsorption of toxic and carcinogenic Cr(VI). Very high (85mg/g) adsorptive capacity of the reported plant makes it an excellent candidate for technological application.

REFERENCES

[1] D. B. Kaufaman, Am. J. “ Diseases Children”, 1970. 119, 374-379. [2] P.R. Wittbrodt, and C.D. Palmer 1995. “Reduction of Cr (VI) in the

presence of excess soil fulvic acid”. Environ. Sci. and Technol. 29: 255 – 265.

[3] L.F. De Filippis, and C.K. Pallaghy, “Heavy metals: sources and biological effects”. In: RAI, L.C Pollution, E. Scheizerbartsche Press, Gaur, J. P. and C. J. Soeder, eds. “Advances in Limnology Series: Algae and Water Stuttgart”, 1994. p. 31-77.

[4] A. Baral and R. D. Engelken, “Environ. Sci. Pollut.” 2002. 5, 121-133. [5] H. Ajamal, A. Mohammad and S. Anwar, 2001. “Sorption studies of

heavy metals on teak leaves using thin layer and column chromatographic technique. Pollut. Res.” 20 (3): 425 – 428.

[6] R. S. Juang, and R. C. Shiau, “Metal removal from aqueous solutions using chitosan-enhanced membrane filtration”. Journal of Membrane Science, February 2000. vol. 165, no. 2, p. 159-167.

[7] B. Volesky, and Z. R. Holan, “Biosorption of heavy metals”. Biotechnology Progress, 1995. vol. 11, no. 3, p 235-250.

[8] A. Kapoor, T. Viraraghavan, “Fungal involving products of Bessel functions,” Phil. Trans. Roy. Soc. London, vol. A247, pp. 529–551, April 1955. (references) 4, p. 533-540.

[9] M. Dakiky, M. Khamis, A. Manassra, and M. Mereb, “Selective adsorption of chromium(VI) in industrial waste water using low- cost abundantly available adsorbents”. Advances in Environmental Research, October, 2002. Vol. 6, no. 4, p. 533-540.

[10] S. S. Ahluwalia, D. Goyal 2005. “Removal of Heavy Metals by Waste Tea Leaves from Aqueous solution”. Eng. Life Sci. 5: 158-162.

[11] A. Espinola, R. Adamian, and L.M.B Gomes, “An innovative technology: natural coconut fibre as adsorptive medium in industrial wastewater cleanup”. Proceedings of the TMS Fall Extraction and Processing Conference, 1999. vol. 3, p 2057-2066.

[12] N. Chubar, JR Carvalho, CMJ Neiva 2003. “Cork Biomass as biosorbent for Cu (II), Zn (II) and Ni (II)”. Colloids Surf. A: Physicochem. Eng. Asp. 230: 57-65.

[13] M. Melo, SF. D’Souza 2004. “Removal of chromium by mucilaginous seeds of Ocimum Basilicu”. Bioresour. Technol. 92: 151-155. metals using rice milling by-products. Characterization and 73.

[14] W.E. Marshall and E.T. Champagne, “Agricultural byproducts as adsorbents for metal ions in laboratory prepared solutions and in manufacturing wastewater”. Journal of Environmental Science and Health - Part A Environmental Science and Engineering, 1995. vol. 30, no. 2, p. 241-261.

[15] A. Saeed M. Iqbal, MW Akhtar 2002. “Application of biowaste materials for the sorption of heavy metals in contaminated aqueous medium”. Pak. J. Sci. Ind. Res. 45: 206-211.

[16] M. Iqbal, A. Saeed, and N. Akhtar, “Petiolar feltsheath of palm: a new biosorbent for the removal of heavy metals from contaminated water”. Bioresource Technology, January 2002. vol. 81, no. 2, p. 153-155.

[17] A.D. Eaton, L.S. Clesceri and A.E. Greenberg, “ Standard Methods for the Examination of Water and Wastewater”. 19th ed. American Public Health Association Washington, DC, 1995. 1325 p. ISBN 0875532233.

[18] S. Lagergren Handlingar Band. 1898. 24 (4).

[19] I. Langmuir, “The adsorption of gases on plane surfaces of glass, mica and platinum”. Journal of the American Chemical Society, 1918. vol. 40, no. 9, p. 1361-1403.

[20] G. Mckay, H.S. Blair and J.R. Gardener, “Adsorption of dyes on chitin I. Equilibrium studies”. Journal of Applied Polymer Science, 1982. vol. 27, no. 8, p. 3043- 3057.

[21] K. Kadirvelu, and C. Namasivayam, “Agricultural by-products as metal adsorbents: sorption of lead (II) from aqueous solutions onto coir-pith carbon”. Environmental Technology, 2000. vol. 21, no. 10, p. 1091-1097.

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