Use of hydrometallurgical wastewater as a precursor for the synthesis of cryptomelane-type manganese dioxide ion exchange material

Cryptomelane-type manganese dioxide was synthesized in order to use it as ion exchange material for the removal of heavy metals from wastewaters. The synthesis was carried out using hydrometallurgical wastewater simulant that is very typical for mining industry after sulphuric acid leaching of the ore and the recovery of base metals. This raffinate simulant solution, consisting of Al, Fe, Mg, Mn, Ca and Na was used as precursor and pure cryptomelane-structured manganese dioxide was synthesized. The ion exchange properties of the cryptomelane were typical for weakly acidic ion exchangers with selectivity towards transition metals. The obtained capacity of 1.3 mmol/g for copper and distribution coefficient as high as ∼104 ml/g are promising for future applications in metal separation processes.