Leaching of metal ions from black shale by organic acids produced by Aspergillus niger

The main concern of the present study is to find a more feasible and economical method to extract metal ions from low grade discarded ores like black shale by Aspergillus niger. A. niger exhibited a good potential in generating varieties of organic acids effective for metal ions solubilization. The effectiveness of organic acids was enhanced when sulphuric acid was added to the medium. Different agricultural wastes as substrates were evaluated. Maximum solubilization of copper (68.5%), zinc (49.0%) and cobalt (60.4%) was achieved in the media containing mango peel, rice bran and glucose as substrates. The extraction of low concentrations of metal ions from this ore indicated that this low grade discarded ore may be a potential source for metal ions in the future.