Adsorption of Co²⁺ on Hydrated Manganese Dioxide

The hydrated manganese dioxide (HMO) was prepared by the oxidation reduction method with potassium permanganate as starting materials, while the resulted HMO was characterized by XRD, BET, TG-DTA and FT-IR. In the adsorption experiment, the influences of various experimental conditions were investigated, and HMO was also applied for the actual treatment of ⁶⁰Co wastewater. Experimental results show a good adsorption property of Co²⁺ on HMO, in the condition of pH=7 and T=298 K, with a maximum adsorption capacity of 132.98 mg/g. The pH of the solution can significantly affect Co²⁺ adsorbed on HMO, and in the experimental pH range, the adsorption capacity increases with pH. Under the same Co²⁺ initial concentration, the adsorption capacity increases with temperature. Co²⁺ adsorption on HMO is influenced while Na⁺, K⁺, Mg²⁺, Ca²⁺, Zn²⁺ and Fe³⁺ coexisted in the solution. The adsorption behavior of Co²⁺ on HMO is well described by pseudo second order kinetic model and Langmuir isotherm model (R²＞0.99), and it is indicated that the adsorption process maybe a chemical and monolayer adsorption. The adsorption thermodynamics data of ΔH=46.96 kJ/mol and ΔG=-26.09 kJ/mol show that the adsorption process is endothermic and spontaneous. In addition, when treating wastewater containing ⁶⁰Co whose initial radioactivity concentration is 2.78×10⁵ Bq/L in the dynamic column experiment, the removal rate is 56.90%.