Bioleaching of oceanic manganese nodules: Current progress and future prospects

The extraction of manganese elements and other strategic elements from oceanic manganese nodules has become a strategic decision to ensure the security of global metal resources and the high-quality green development of metal resource processing and metallurgy industry due to the gradual depletion of high-quality terrestrial metal resources and the increase of difficult-to-select and difficult-to-smelt deposits. In order to achieve the enrichment and separation of diverse elements within oceanic manganese nodules, it is imperative to initiate chemical reactions that facilitate the breakdown of complex oxides, particularly manganese dioxide. Bioleaching is a viable treatment option for oceanic manganese nodules with low operating costs and environmental damage. However, the mechanism of oceanic manganese nodules bioleaching is not fully studied, and the prospect of technology development is uncertain. We have reviewed five influencing factors on bioleaching of oceanic manganese nodules: mineralogical characteristics, chemical reaction equilibrium, thermodynamic characteristics, microbial properties, and operational variables. It then makes new development recommendations and technological system suggestions for the future improvement of oceanic manganese nodule bioleaching, primarily focusing on the development of new technologies for challenging to select and difficult to smelt ores, the practicality of strategic energy metal development, the cell design and its materials revolution, environmental protection and management, and all-round resource utilization. Solving the above critical technical issues will boost the high-quality development of metal industry and environmental protection.