Hydroxylation of electrolytic manganese anode slime with EDTA-2Na and its adsorption of methylene blue

Abstract

Electrolytic manganese anode slime (EMAS) is a kind of waste produced by anode chambers in the process of electrolytic manganese production. In this study, the surface of EMAS was hydroxylated with EDTA-2Na, and a new adsorbent for removing methylene blue (MB) was obtained. The hydroxylation of EMAS (H-EMAS) was characterized by XRD, XRF, FTIR, BET, SEM and XPS. The results showed that H-EMAS contains many pores and cracks and that the specific surface area of H-EMAS was 53.17 m2/g. The maximum adsorption capacity of H-EMAS for MB was 70.74 mg/g when the initial pH was 6.00, the initial MB concentration was 500 mg/L, the reaction time was 120 min and the reaction temperature was 298 K. Adsorption kinetics and isotherms showed that the adsorption of MB on H-EMAS conformed to pseudosecond-order kinetic model and Langmuir isotherm, respectively. Thermodynamic analysis showed that the adsorption process was a spontaneous and exothermic physical adsorption process. Moreover, H-EMAS adsorbent recycling showed that the adsorption capacity of H-EMAS was 55.35 mg/g after four cycles and that the adsorption efficiency for MB only decreased by 21.75%. This study provides a new method for the resource utilization of EMAS.