Removal of Molybdenum (VI) from Mine Tailing Effluents with the Aid of Loessial Soil and Slag Waste

Removal of heavy metals from mine tailing effluent has been a long-standing environmental management issue in the mining industry. This article aims to investigate molybdenum [Mo(VI)] removal by waste slag, which has not been fully tested. In this study, the removal efficiencies of Mo(VI) from aqueous solutions by desulfurization steel slag (DSS), converter steel slag (CSS), and cinder (CI) were examined and compared against that of loessial soil (LS). Results showed that the sorption isotherms fitted the Langmuir model well, and the Langmuir adsorption capacity ( Q 0 ) of the four sorption media generally complied with the following order: DSS>CSS>CI>LS. Adsorption reaction was found to follow the pseudo–second-order rate, and the adsorption of Mo(VI) was sensitive to pH values. The four adsorbents exhibited a significant Mo(VI) removal at low pH values ( e.g. , pH 3–4.5), but such adsorption decreased rapidly when pH was >5; little adsorption occurred when the pH value was >8. The competitive effect of PO 4 3− and SO 4 2− with Mo(VI) for adsorption associated with the four sorption media followed the order LS>CI>CSS>DSS, and moreover, the effect of PO 4 3− on the adsorption of Mo(VI) was observed to be stronger than that of SO 4 2− . Desorption capacity of the four sorption media generally complied with the following order: LS>CI>CSS>DSS.