Uranium recovery and manganese removal from acid mine drainage

Abstract

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 UO 2 (SO 4 ) 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 123mg 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.

Radiometric Evaluation in a Uranium Mine under a Decommisioning Processs

“…Other studies are evaluating several questions related to the acid mine drainage and the recovery of uranium (Gomes et al, 2011;Santos & Ladeira, 2011;Ladeira & Gonçalves, 2008). It is expected that soon new hydrogeological studies will begin, since a new project that has technical support from the University of Queensland -Australia, was endorsed.…”

The use of limestone, lime and MnO2in the removal of soluble manganese from acid mine drainage

“…1.0mg/L) at pH 9.1 for limestone and pH 10.0 for lime. According to literature [6,9,10] the formation of stable manganese oxides is obtained only at pH above 7.5 and the importance of the pH increase in the removal of Mn is extensively discussed. Figure 1 also shows that the curve for limestone stands below the curve for lime in almost the whole range of pH.…”

Batch removal of manganese from acid mine drainage using bone char

“…Most metal species are precipitated, but the removal of manganese ions from AMD is notoriously difficult due to their complex chemistry in aqueous systems (Bamforth et al, 2006;Robinson-Lora and Brennan, 2010). In fact, for full precipitation of manganese as Mn(OH) 2 , the pH must be raised to approximately 11, which involves a significant consumption of lime (Ladeira and Gonçalves, 2008). After manganese removal, the pH must then be neutralized before discharge.…”

“…Particularly in the state of Minas Gerais, the AMD generated in the region of Poços de Caldas contains radionuclides (uranium, thorium, radium, among others), as well as species like manganese, zinc, fluoride, and iron at concentration levels that exceed those authorized by Brazilian legislation for direct discharge (CONAMA, 2005;Ladeira and Gonçalves, 2008). The current treatment of such acid waters consists of metals precipitation with lime followed by pH correction.…”

“…The rise in the concentration of metal ions in the percolating waters due to AMD is an important source of contamination of water courses, particularly when ions can be spread to the food chain. Aimed at minimizing the severity of such impacts, environmental protection laws require appropriate plans for mine closures in an attempt to increase the life cycle of closed mines, including steps of decommissioning and the recovery of degraded areas (Ladeira and Gonçalves, 2008).…”