Enhanced removal of hexavalent chromium from aqueous solution by functional polymer-wrapped gamma-alumina composite adsorbent

Abstract

Here we reported a novel xanthated chitosan-entrapped gamma-alumina (XCSA) composite sorbent that presents effective removal toward toxic hexavalent chromium ions [Cr(VI)] from water. The samples were characterized by FTIR, SEM-EDS, XRD, TGA, and XPS. Batch sorption experiments were performed to investigate the influences of component ratio, initial solution pH, and competing ions on the Cr(VI) removal. An adsorption-coupled reduction mechanism controlled the Cr(VI) removal processes, in which xanthation groups played a key part. The sorption process revealed that ∼ 65% Cr(VI) (50 mg/L) was adsorbed within 5 min, and kinetic data fitted well with the pseudo-second-order model. The sorption isotherm data fitted well with Freundlich model, and the experimental maximum sorption capacity for Cr(VI) by XCSA-1.0 (with the alumina-to-polymer mass ratio of 1:1) was ∼ 110.5 mg/g. In addition, XCSA-1.0 expressed the good anti-interference ability of the competing ions. Moreover, the exhausted adsorbent, which could be regenerated by 1.0 M KCl solution, exhibited good reusability after five cycles. Overall, this study shows XCSA as a promising sorbent for anionic heavy metal removal from water. • Xanthated chitosan wrapping γ -alumina sorbents were prepared for Cr(VI) removal. • Fast kinetics of adsorption (within 120 min) over this composite adsorbent. • A better adsorption capacity ( ∼ 110.5 mg/g) than many other similar sorbents. • An adsorption-coupled reduction mechanism controlled Cr(VI) removal processes.