Effective removal of Cr(VI) from aqueous solution by iron‐carbonized solid waste composite: behavior mechanism and factor analysis

Abstract

AbstractBACKGROUNDThe spent bleaching earth (SBE) is a solid waste produced during the refining of vegetable oil, with features of high residual oil and difficult disposal. At present, pollution control by the treatment of waste is a hot issue to attract more and more attention. This study used SBE as the raw materials and developed a new type of iron‐carbon composite (FexOy/SBE@C) by loading iron on spent bleaching earth carbon (SBE@C) to remove Cr(VI) in water. SBE@C was obtained by the pyrolysis of SBE.RESULTSThe behavior mechanism and factor analysis of FexOy/SBE@C for Cr(VI) removal in water were investigated for the first time. At first, one‐factor experiments in the preparation process were adopted to obtain FexOy/SBE@C with optimal performance. By characterization analysis of the optimal FexOy/SBE@C before and after Cr(VI) removal, it was found that the Cr(VI) removal mechanism was adsorption followed by reduction. Specifically, the adsorption kinetic and isotherm behaviors of FexOy/SBE@C for Cr(VI) belong to the pseudo‐second‐order kinetic model and Langmuir isotherm, respectively. Cr(VI) removal by FexOy/SBE@C is spontaneous (△G<0) and endothermic (△H>0). The presence of coexisting anions (i.e., BrO3− < SO42− < PO43−) and the increase of pH (only adsorption at pH>7) are not conductive to Cr(VI) removal by FexOy/SBE@C. Fortunately, N2 atmospheres can promote Cr(VI) removal (~100%) that is significantly higher than those in air atmosphere (63.34%) and natural conditions (82.25%).CONCLUSIONOverall, FexOy/SBE@C has the satisfactory Cr(VI) removal performance through physical adsorption and chemical reduction, and exhibits great potential application value in Cr(VI) elimination from water. © 2022 Society of Chemical Industry.