Improvements to mine drainage prediction for CND and REE/Li-bearing mine wastes

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One of the most serious environmental issues facing the mining industry worldwide is the contamination of drainage waters from tailings ponds and waste rock piles. Such contamination may occur when sulfide minerals in the mine wastes oxidize and generate contaminants in the drainage waters, leading to acid mine drainage (AMD) in acidic waters or to contaminated neutral drainage (CND) in near-neutral waters. The successful management and reclamation of potentially harmful wastes greatly depends on the use of predictive tests to determine the potential occurrence of contaminated mine drainage. These tests must be as accurate and representative as possible to ensure that environmental degradation by AMD or CND can be effectively and efficiently avoided or mitigated. The interpretation of these predictive tests requires an extensive knowledge of the composition of the studied materials, as well as of the different geochemical and microbiological mechanisms controlling the release of contaminants from mine wastes. This is especially critical for the emerging commodities of rare earth elements (REE) and lithium (Li), as well as mines in the Arctic. ******Historically, the onset and quality of CND have been predicted using the same techniques which were originally developed for AMD prediction (e.g. acid-base accounting, humidity cells). However, these methods generally seek to assess the onset of acidic conditions rather than to predict the exact concentrations to be expected, which is essential for CND. In addition, knowledge on the microbiological involvement in CND-generation is still relatively uncertain, particularly for cold temperatures; biotic processes might be significantly involved in sub-zero sulfide oxidation. Thus, more research is needed to improve CND prediction and acquire additional knowledge on the microbiology of CND generation. ******In addition, the increasing demand for clean energy has spurred the development of numerous REE and Li mining projects. These new operations require rigorous investigation of the geochemical controls on REE and Li leaching from mine wastes as there are currently only very sparse data found in the literature. Thus, more research is needed in order to significantly improve knowledge on these issues.******The research program is divided into two main themes: (A) Improvements to CND prediction in ambient and cold temperatures, and (B) Evaluation of the metal leaching potential of REE- and Li-bearing mine wastes. The methodology used to reach these objectives combines thorough physical, chemical, mineralogical, and microbiological characterizations with kinetic mine drainage prediction tests to better understand the mechanisms underlying contaminant release. The program will train undergraduate and graduate students, thus providing the Canadian mining industry and research community with much needed experts in the environmental management of mines.