Facile modification of activated carbon with highly dispersed nano-sized α-Fe2O3 for enhanced removal of hexavalent chromium from aqueous solutions

Activated carbon-coated alpha-Fe2O3 nanoparticles (nFe(2)O(3)@AC) were synthesized by a facile impregnation method to enhance hexavalent chromium (Cr(VI)) removal from water. The SEM images confirmed that alpha-Fe2O3 particles ranging from 90 to 500 nm were dispersedly loaded on the AC, which successfully amended Cr(VI) removal. The nFe(2)O(3)@AC was able to remove Cr(VI) with a 3 times higher efficiency of 94% in comparison with the AC. After adsorption, Cr(VI) reduction coupled with AC oxidation and low soluble (CrxFe1-x)(OH)(3) precipitates were eventually formed. The Cr(Vl) removal process was pH-dependent and could be well fitted to pseudo second-order kinetics. The nFe(2)O(3)@AC could be easily regenerated by 0.1 M HCl and showed a good stability as an 80% Cr(VI) removal efficiency was recorded after 4 desorption-adsorption cycles. In addition, this composite had a promising potential for repeated utilization because the AC of the adsorbed nFe(2)O(3)@AC could be refreshed and remodified with nFe(2)O(3) after stripping all the nFe(2)O(3) and (CrxFe1-x)(OH)(3) precipitates from its surface by 1 M HCl and a Cr(VI) removal efficiency of 86% could be achieved. Our results demonstrated that the use of nFe(2)O(3) is an efficient and promising method to modify AC and enhance Cr(VI) removal form aqueous solutions. (C) 2019 Elsevier Ltd. All rights reserved.