Chromium removal on chitosan-based sorbents - An EXAFS/XANES investigation of mechanism

Author(s)

Vieira, Rodrigo S. ^[1] ; Meneghetti, Emerson ^[2] ; Baroni, Paula ^[2] ; Guibal, Eric ^[3] ; Gonzalez de la Cruz, Victor M. ^{[4, 5]} ; Caballero, Alfonso ^{[4, 5]} ; Rodriguez-Castellon, Enrique ^[6] ; Beppu, Marisa M. ^[2]

Affiliation

^[1] Univ Fed Ceara, UFC, Dept Chem Engn, BR-60455760 Fortaleza, Ceara - Brazil

^[2] Univ Estadual Campinas, UNICAMP, Sch Chem Engn, BR-13081970 Campinas, SP - Brazil

^[3] Ecole Mines Ales, Lab Genie Environm Ind, F-30319 Ales - France

^[4] CSIC US, Inst Ciencias Mat Sevilla, Seville 41092 - Spain

^[5] CSIC US, Dept Inorgan Q, Seville 41092 - Spain

^[6] Univ Malaga, Fac Ciencias, Dept Quim Inorgan, E-29071 Malaga - Spain

• Document type: Journal article
• Source: Materials Chemistry and Physics; v. 146, n. 3, p. 412-417, AUG 14 2014.
• Web of Science Citations: 31

Abstract

Chitosan is known to be a good sorbent for metal-containing ions as the presence of amino groups and hydroxyl functions act as effective binding sites. Its crosslinking, employing glutaraldehyde or epichlorohydrin, may change the sorption properties (sorption capacity or diffusion properties) of this biopolymer, since the available functional groups are different in each case. X-ray absorption spectroscopy (XAS), including extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES), Fourier-transformed infrared spectroscopy with attenuated total reflectance device (FTIR-ATR) was used along with speciation diagrams, in order to identify the binding groups involved in chromate sorption and its mechanisms. In pristine chitosan and epichlorohydrin-crosslinked chitosan membranes, amino groups are most likely responsible for adsorption, although the contribution of hydroxyl groups cannot be excluded (especially for metal-sorbent stabilization). In this case, when adsorbed about 70% of chromate ions remain in the Cr(VI) oxidation state. In the case of glutaraldehyde-crosslinked membranes, the functional groups involved are different. Carbonyl groups and imino bonds resulting from the reaction of the crosslinking agent and amino groups - may be involved in the adsorption mechanism. Additionally, a higher fraction of chromate anions, around 44% are reduced to Cr(III) oxidation state in loaded sorbent. The presence of free aldehyde groups may explain this partial reduction. (C) 2014 Elsevier B.V. All rights reserved. (AU)