Study on the efficiency of manganese oxide-bearing manganese sand for removing Mn2+ from aqueous solution

Abstract

To obtain efficient and rapid manganese removal performance of NMS (natural manganese sand), MOBMs (manganese oxide-bearing manganese sand) were prepared and loaded with manganese oxide formed by forced oxidation of manganese sulfate with sodium hypochlorite onto the surface of NMS. The results of SEM, EDS, BET, XPS, XRD and Zeta potential analyses showed that manganese oxides were successfully loaded on the surface of NMS, with the main components being MnO2 and Mn2O3. The surface of MOBMs is covered by needle-shaped flocculent manganese oxides, with a large number of mesopores. The isothermal adsorption and kinetic adsorption model indicated that the adsorption of Mn2+ by MOBMs occurred through monolayer adsorption and chemical adsorption. The intraparticle diffusion model showed that the adsorption process is dominated by mesoporous and microporous diffusion, which is controlled by adsorption, membrane diffusion, particle diffusion and catalytic oxidation. Under the conditions of the static test, the best adsorption conditions were determined as follows: Df = 2 g/100 ml (q = 0.149 mg/g), pH = 7.5–8.5. Under these conditions, the removal rate of Mn2+ by MOBMs was 84.47%. The presence of competing cations NH4+ and Fe2+ had a negative effect on the removal of Mn2+. The dynamic test shows that the MOBM maturation cycle takes only 7 days. MOBMs can realize the efficient utilization of low-quality NMS, shorten the maturity period of manganese removal filter material, improve the adsorption performance, and ensure the efficient removal of Mn2+.