Synthesis of Manganese-type Ion Exchanger and Its Exchange Kinetics with K~+

Cryptomelane-type hydrous manganese dioxide(CRYMO) precursor was synthesized using potassium permanganate and manganese sulfate as raw materials.CRYMO was obtained by acid-modifying of the precursor and characterized by XRD.Its saturated exchange capacity and ion exchange kinetics for 0.1 mol·L-1 K+ at 25 ℃ were determined.The obtained optimum conditions for preparing CRYMO were KMnO4 concentration 0.5 mol·L-1,MnSO4 concentration 2.0 mol·L-1,n(KMnO4)∶n(MnSO4)=1∶2,reaction temperature 75 ℃ and concentration of HNO3 for acid-modifying 5 mol·L-1.The crystal structure of CRYMO was α-MnO2 and its saturated exchange capacity of 1 g CRYMO for K+ was 181.5 mg.The ion exchange kinetic data of CRYMO for 0.1 mol·L-1K+ were related with different adsorption models and the results showed that the optimum kinetic model was Bangham and the kinetic equation was lg Q=-0.892 23+0.627 47lg t(25℃).