Preparation of New Nano-MnO2 and Its Molybdenum Adsorption in Manganese Sulfate Solution

Manganese sulfate solution was in this study oxidized, using H2O2 as oxidant, to obtain new Nano-MnO2 in situ. The characterization of new MnO2 was carried out by XRD, SEM, FT-IR and BET. The effect of new manganese dioxide adsorpting molybdenum ion in manganese sulfate solution was also studied. Results showed that the main crystal form of the new MnO2 was γ type, and there was agglomeration of nanospheres with 200∼300 nm diameter from the microscopic morphology, which had abundant surface hydroxyl groups, and its specific surface area was as high as 146 m2/g. MnO2 addition was 1.0 g under optimal adsorption conditions when the pH was 2, and the reaction time was 30 min, with removal rate of 99.2% molybdenum and 0.26 ppm residual amount of molybdenum in manganese sulfate solution, which met the quality standard for high purity manganese sulfate (HG/T4823-2015) with ≤5 ppm molybdenum content. Moreover, the thermodynamics and kinetics of molybdenum adsorption by new manganese dioxide were also studied. The experiments showed that the adsorption process was in accordance with the Freundlich adsorption equation. The adsorption process of molybdenum on manganese dioxide could be described with pseudo second order kinetic model, and the internal diffusion was a controlling link of adsorption rate.