A novel biochar (BC) supported nanoscale iron sulfide (FeS) composite (CMC-FeS@BC) combining the advantages of BC, carboxymethyl cellulose (CMC), and FeS was synthesized and tested for Cr(VI) removal efficiency and mechanisms. Structure and morphology analysis showed that FeS particles were effectively soldered onto the surface of BC through –OH, C=C, O=C–O, C–O, and Si–O functional groups, with CMC as a dispersing and soldering reagent. The composite at a mass ratio of FeS: CMC: BC = 1:1:1 displayed an enhanced Cr(VI) adsorption capacity of 130.5 mg/g at pH 5.5 compared to 38.6 mg/g for bare FeS and 25.4 mg/g for plain BC. FTIR and XPS analysis suggested that surface sorption and reduction were dominant mechanisms for Cr(VI) removal. At the equilibrium Cr(VI) concentration of 13.4 mg/L, 57% of Cr(VI) removal was due to reduction, and 43% was ascribed to surface sorption. A pseudo second-order kinetic model adequately simulated the adsorption kinetics, indicating that chemisorption was the rate-controlling step. The fitting results of the mass transfer model suggested that sorption kinetics was external mass transfer limited. The Redlich-Peterson model fitted better than the Langmuir and Freundlich models in simulating the adsorption isotherm data, again suggesting a hybrid sorption-reduction process. Results from this study demonstrated the promise of CMC-FeS@BC composite as a low-cost, “green”, and effective sorbent for removal of Cr(VI) in the environment.

Removal of hexavalent chromium from aqueous solutions by a novel biochar supported nanoscale iron sulfide composite

253rd National Meeting (2017)

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