Bioleaching of heavy metals from a low-grade mining ore using Aspergillus niger

The main concern of this study is to develop a feasible and economical technique to microbially recover metals from oxide low-grade ores. Owing to the significant quantities of metals that are embodied in low-grade ores and mining residues, these are potential viable sources of metals. Additionally, they potentially endanger the environment, as the metals they contain may be released in hazardous form. Mining industries are seeking efficient economic techniques to handle these ores. Pyrometallurgical and hydrometallurgical techniques are often expensive, energy intensive, or have negative environmental impacts, thus biohydrometallurgical techniques are gaining attention. This study demonstrates the feasibility of recovering metals from mining residues by employing Aspergillus niger, which generates a variety of organic acids effective for metal solubilization. The effectiveness was enhanced with the addition of sulfuric acid, and different agricultural wastes such as potato peels were tested. Various auxiliary processes were also evaluated to improve efficiency or reduce costs. Maximum solubilization of 68%, 46%, and 34% for copper, zinc, and nickel respectively was achieved, with minimal 7% iron co-dissolution.