Uranium recovery and manganese removal from acid mine drainage

This work is aimed at the selection of an appropriate adsorbent for uranium and manganese present in acid mine water drainage. The pH of the acid water is around 2.7, the uranium concentration is in a range of 9-15mg/L, the manganese concentration approximately 170mg/L and the sulphate concentration is near 2000mg/L. The uranium in this solution, where sulphate is present in high levels, is basically in the form of UO2(SO4)(3)(-4) and the manganese is in the form of Mn+2. The removal of these elements has been studied using activated carbons, gibbsite, zeolite, apatite and biological adsorbent. Among all adsorbents tested, the biological material was the one which presented the best performance taking into account the necessity of removing Mn and U simultaneously. The maximum adsorption capacity varied from 10 to 14 mg U.g(-1) and 83 to 123 mg Mn.g(-1). The results, obtained by column experiments, showed that the sulphate had a deleterious effect on the uranium recovery by the biological adsorbent. Mn removal was increased with the increase of pH from 2.6 to 7.0. Adsorption of these elements by activated carbons, gibbsite, zeolite and apatite was lower if compared to the biological material.