Resource recovery and water reclamation from acid mine drainage: Market analysis, industry trends, and future research directions

Acid mine drainage (AMD) is a highly recalcitrant wastewater matrix that is typically generated from coal and metal mining activities and contains elevated levels of (heavy) metals and sulfates, along with rare earth elements (REEs) and radionuclides in some instances. This review seeks to elucidate the physicochemical characteristics of AMD and potential resource recovery avenues that can grossly underpin circularity and introduce the waste-to-resource paradigm. Specifically, opportunities for major metals (e.g., iron (Fe), aluminum (Al), and manganese (Mn)) and critical minerals, such as cobalt (Co), nickel (Ni), and notably, REEs recovery, along with other minor constituents, such as radionuclides, were explored. Other valorization avenues, such as sulfates transformation to sulfuric acid and recovery, and water reclamation were further explored. The techniques for resource recovery from AMD, such as precipitation, adsorption, solvent extraction, and ion exchange, were discussed, as well as possible industrial uses of the recovered materials (e.g., coagulants, adsorbents, pigments and catalysts). The beneficiation and valorization of AMD can minimize ecological footprint associated with this notorious mine water effluent, and, to a larger extent, reduce the extraction of virgin resource, such as REEs, while water reclamation can provide water security in water-scarce regions and countries. The recovered resources can provide an important revenue stream by offsetting the treatment costs and even making the process self-sustainable due to the high value of certain products. For example, the REEs global market in 2023 was USD$5.9 billion and is expected to reach USD$14.2 billion by 2033, with a compound annual growth rate (CAGR) of 12 %, thus denoting that recovering REEs from AMD could be profitable, while it also reduces mining requirements and associated environmental impacts. Finally, knowledge gaps in terms of recoverability, along with challenges, prospects, and avenues for further research into this growing field were also distilled.