Mobilisation of metals from Kupferschiefer sensu strictu in neutral to alkaline environment using bulk and biotechnologically produced organic acids

The European Kupferschiefer deposits constitute a challenging local resource of a broad spectrum of metals such as copper, manganese, molybdenum, silver and zinc. In order to exploit them both efficiently and environmentally benignly, biotechnological leaching approaches are investigated. Commonly used acidophilic bioleaching is limited by high carbonate content of up to 18 % resulting in an increased pH value of more than 2. Hence, alternative processes such as neutral leaching are tested. Experiments were aiming at metal solubilisation using glutamic and citric acid as bulk chemicals, as well as biotechnologically produced citric acid. Subsequently, mobilisation of Cu, Mn, Mo, Co, Zn, Ga, Ag, Au, Ni and Pt has been reported. Results show that mostly the use of organic acids in neutral to alkaline pH range performs better in metal solubilisation than in acidic milieu.