Trivalent chromium removal from aqueous solutions by a sol-gel synthesized silica adsorbent functionalized with sulphonic acid groups

A high capacity hybrid silica adsorbent was synthesized via sol gel processing with sulphonic acid groups as trivalent chromium complex ions chelators from aqueous solutions. The synthesis included co-condensation of tetraethoxysilane (TEOS) with 3-(mercaptopropyl)trimethoxysilane (MPS), and oxidation of thiol to sulphonic acid groups. Chromium uptake kinetic, batch and fixed-bed experiments were performed to assess the removal of this metal from aqueous solutions. C-13, Si-29 CPMAS NMR, FTIR XPS were used to characterize the adsorbent structure and the nature of chromium complexes on the adsorbent surface. Chromium maximum uptake was obtained at pH 3 (72.8 mg/g). Elemental analysis results showed ligand density of 1.48 mmol sulphonic groups/g. About 407 mL of Cr(III) solution (311 mg/L) were treated to breakthrough point reaching <= 0.06 mg/L at the effluent. These results comply with USEPA regulation for chromium concentration in drinking water (<= 0.1 mg/L). The adsorbent shows potential to be used in chromium separations to the industrial level. (C) 2014 Elsevier Ltd. All rights reserved.