A synthesized polymeric form of chitosan, electrochemically precipitated and photochemically modified, has been found to have significant value in removal of toxic chromate oxyanions from solution. Fourier Transform Infra-Red (FTIR), Raman and X-ray photoelectron spectroscopy (XPS) indicated that a significant percentage of the amine functional groups were oxidized to nitro groups as a result of reactions with hydroxyl ions formed in the electrochemical process with additional oxidation occurring as a result of exposure to ultra-violet light. The adsorption capacity of the modified chitosan for chromate was investigated in a batch system by taking into account effects of initial concentration, pH of the solution and contact time. Nitro-chitosan showed greater adsorption capacity towards Cr (VI) than other forms of chitosan, with a maximum adsorption of 173 mg/g. It was found that pH 3 is the optimum for adsorption, a Langmuir model is the best fit for the adsorption isotherm, and the kinetics of reaction followed a pseudo second order function. Overall, our results indicate that electrochemical modification of chitosan is an effective method to enhance the reactivity of chitosan towards metals.
References
[1]
Mulligen, C.N.; Yong, R.N.; Gibbs, B.F. Remediation technologies for metal-contaminated soils and groundwater: An evaluation. Eng. Geol. 2001, 60, 193–207, doi:10.1016/S0013-7952(00)00101-0.
[2]
Wilkin, R.T.; Su, C.; Ford, R.G.; Paul, C.J. Chromium-removal process during groundwater remediation by a zerovalent iron permeable reactive barrier. Environ. Sci. Technol. 2005, 39, 4599–4605, doi:10.1021/es050157x.
[3]
Wan Ngah, W.S.; Kumari, A.; Fatinathan, S.; Ng, P.W. Adsorption of chromium from aqueous solution using chitosan beads. Adsorption 2006, 12, 249–257, doi:10.1007/s10450-006-0501-0.
[4]
Baroni, P.; Vieira, R.S.; Meneghetti, E.; da Silva, M.G.C.; Beppu, M.M. Evaluation of batch adsorption of chromium ions on natural and crosslinked chitosan membranes. J. Hazard. Mater. 2008, 152, 1155–1163, doi:10.1016/j.jhazmat.2007.07.099.
[5]
Loyaux-lawniczak, S.; Lecomte, P. Chromium in a polluted groundwater: Redox process and immobilization in soils. Environ. Sci. Technol. 2001, 35, 1350–1357, doi:10.1021/es001073l.
[6]
Wang, J.; Peng, R.; Bao, Z.; Yang, J.; Chen, S.; Liu, Q. Quick Removal of Chromium (VI) Ions from Aqueous Solution by Chitosan and Ferrous Ions. In Proceedings of IEEE 4th International Conference on Bioinformatics and Biomedical Engineering (ICBBE), Chengdu, China, 18–20 June 2010; pp. 1–4.
[7]
Bailey, S.E.; Olin, T.J.; Bricka, R.M.; Adrian, D.D. A review of potentially low-cost sorbents for heavy metals. Water Res. 1999, 33, 2469–2479, doi:10.1016/S0043-1354(98)00475-8.
[8]
Modrzejewska, Z.; Maniukiewicz, W.; Wojtasz-pajak, A. Determination of Hydrogel chitosan membrane structure. Polish Chitin Soc. Monogr. XI 2006, 113–121.
[9]
Nunthanid, J.; Puttipipatkhanachorn, S.; Yamamoto, K.; Peck, G.E. Physical properties and molecular behavior of chitosan films. Drug Dev. Ind. Pharm. 2001, 27, 143–157, doi:10.1081/DDC-100000481.
[10]
Guibal, E. Interactions of metal ions with chitosan-based sorbents: A review. Separ. Purif. Tech. 2004, 38, 43–74, doi:10.1016/j.seppur.2003.10.004.
[11]
Rojas, G.; Silva, J.; Flores, J.A.; Rodriguez, A.; Ly, M.; Maldonado, H. Adsorption of chromium onto cross-linked chitosan. Separ. Purif. Tech. 2005, 44, 31–36, doi:10.1016/j.seppur.2004.11.013.
Halada, G.P.; Jha, P.; Nelson, K.; Zhao, W.; Korach, C.S.; Neiman, A.; Lee, S.J.; Mintzer, E. Formation and characterization of chitosan-based coatings on stainless steel. In Biomaterials; Kulshrestha, A.S., Mahapatro, A., Henderson, L.A., Eds.; ACS symposium series; American Chemical Society: Washington DC, USA, 2010; pp. 159–171.
Beard, B.C. Cellulose nitrate as a binding energy reference in N(1s) XPS studies of nitrogen-containing organic molecules. Appl. Surf. Sci. 1990, 45, 221–227, doi:10.1016/0169-4332(90)90005-K.
[16]
Berger, P.; Vel Leitner, N.K.; Dore, M.; Legube, B. Ozone and hydroxyl radicals induced oxidation of glycine. Water Res. 1999, 33, 433–441.
[17]
Gad, Y.H. Preparation and characterization of poly(2-acrylamido-2-methypropane sulfonic acid)/chitosan hydrogel using gamma irradiation and its application in wastewater treatment. Radiat. Phys. Chem. 2008, 77, 1101–1107, doi:10.1016/j.radphyschem.2008.05.002.
[18]
Hena, S. Removal of chromium hexavalent ion from aqueous solutions using biopolymer chitosan coated with poly 3-methyl thiophene polymer. J. Hazard. Mater. 2010, 181, 474–479, doi:10.1016/j.jhazmat.2010.05.037.
[19]
Verma, B.M.; Krishnaiah, A.; Talbott, J.L.; Edgar, S.D. Removal of Hexavalent Chromium from wastewater using a new composite chitosan biosorbent. Environ. Sci. Technol. 2003, 37, 4449–4456, doi:10.1021/es021013a.
[20]
Aydin, Y.A.; Aksoy, N.D. Adsorption of chromium on Chitosan: Optimization, kinetics and thermodynamics. Chem. Eng. J. 2009, 151, 188–194, doi:10.1016/j.cej.2009.02.010.
[21]
Aksu, Z.; Gonen, F.; Demircan, Z. Biosorption of chromium(VI) ions by Mowital B3OH resin immobilized activated sludge in a packed bed: comparison with granular activated carbon. Process Biochem. 2002, 38, 175–186, doi:10.1016/S0032-9592(02)00053-5.
[22]
Qin, C.; Du, Y.; Zhang, Z.; Liu, Y.; Xiao, L.; Shi, X. Adsorption of Chromium (VI) on a novel quaternized chitosan resin. J. Appl. Polym. Sci. 2003, 90, 505–510, doi:10.1002/app.12687.
[23]
Baran, A.; Bicak, E.; Baysal, S.H.; Onal, S. Comparative studies on the adsorption of Cr(VI) ions on to various sorbents. Bioresour. Technol. 2006, 98, 661–665.
[24]
Sabharwal, S.; Ramnani, S.P. Adsorption behavior of Cr(VI) onto radiation crosslinked chitosan and its possible application for the treatment of wastewater containing Cr(VI). React. Funct. Polym. 2006, 66, 902–909, doi:10.1016/j.reactfunctpolym.2005.11.017.
[25]
Hu, Xin-jiang; Wang, J.S.; Liu, Y.G.; Li, X.; Zeng, G.; Bao, Z.; Zeng, X.; Chen, A.; Long, F. Adsorption of chromium (VI) by ethylenediamine-modified cross-linked magnetic chitosan resin: Isotherms, Kinetics and thermodynamics. J. Hazard. Mater. 2011, 185, 306–314, doi:10.1016/j.jhazmat.2010.09.034.
[26]
OMNIC for Nicolet Almega. version 7.3 service pack 1, Thermo Electron Corporation, Waltham, MA, USA, 2006.
[27]
Sun, X.; Peng, B.; Ji, Y.; Chen, J.; Li, D. Chitosan(chitin)/cellulose composite biosorbents prepared using ionic liquid for heavy metal ions adsorption. AIChE J. 2009, 55, 2062–2069, doi:10.1002/aic.11797.
