Iron oxides decorated graphene oxide/chitosan composite beads for enhanced Cr(VI) removal from aqueous solution

This study is the first to evaluate the effects of Iron oxides (FeOx) species and their decoration on graphene oxide/ chitosan (GO/CS) composites for Cr(VI) removal and the possibility of Fe secondary pollution. Results show that Fe(III) is a better decoration material than Fe(II) and decoration through immersion-evaporation shows a higher adsorption capacity of Cr(VI) (Q) than co-precipitation. Fe2O3-GO/CS as the only eco-friendly composite for enhanced Cr(VI) removal is further used for batch adsorption experiments, characterization, kinetics, isotherms, and thermodynamic studies. It is found that Cr(VI) removal mainly includes electrostatic attraction between Cr (VI) oxyanions and surface -NHi and -OW, and the adsorbed Cr(VI) partially reduces to Cr(III). Q(e) increases with the increasing initial Cr(VI) concentration, contact time, and temperature, while decreases with the increas- ing pH and mass and volume ratio (m/v). The coexisting ions (Cl-.NO3-, SO42-,PO43-, As, Fe. and Pb) can cause an obvious decrease of Q. The removal efficiency (R-e) and Q(e) are 94.3% and 83.8 mg/g, respectively under the optimal conditions. After five times of regeneration, R-e is still as high as 84% and Q. drops about 2.6%. Cr(VI) adsorption is spontaneous and endothermic. which is best fitted with the Sips model, and the fitted maximum Q(e) is 131.33 mg/g. (C) 2021 Elsevier B.V. All rights reserved.