Abstract:

Contemporary mining companies must place as much emphasis on environment, social, and corporate governance (ESG) considerations as they do on conventional profit margins when assessing company performance. Potash mines are no exception to this ideological transition, as they face both internal and external pressures to minimize their environmental footprint. This research proposes a novel approach towards achieving sustainable potash (KCl) mining operations: applying natural zeolite minerals to rapidly recover large quantities of potassium (K) from potash tailings and brines. The K-loaded (“K-form”) zeolites are subsequently recycled and reused as a cost-effective soil amendment intended for the reclamation and remediation of contaminated sites, such as abandoned oilfield sites, and decommissioned mines. Five different Canadian zeolite deposits are investigated, with Juniper high purity crystals (HPC) possessing the strongest affinity for K-recovery, although TransCanada HPC, TransCanada Ore, and Juniper Ore also display K-recovery potential. Experiments demonstrate how zeolite minerals exhibit a selective preference for K⁺ ions over other competing cations in potash brines such as sodium. The innovative zeolite-based K-recovery approach can extract up to 70% of the residual potassium within potash tailings and brines. Existing technologies are used to mix zeolite and potash brines, with heuristic experiments highlighting that the magnitude of K-adsorption onto the zeolite surface can be controlled by selecting the optimal zeolite grain size, adjusting the zeolite-to-brine ratio, diluting the potash brine, and limiting zeolite-brine mixing to 2 adsorption cycles. Isotherm experiments reveal that J HPC (coarse sand-sized particles) K-adsorption is best represented by the Langmuir Model (R² = 0.99) and has a q_max value of 9 mg/g. These results are comparable to other zeolite-based adsorption studies with fine powder-sized particles, which are more expensive to produce. The comparable K-recovery rate and improved cost-effectiveness is a breakthrough finding which further corroborates the feasibility of the zeolite-based K-recovery concept. Following adsorption, the K-form zeolites are tested as a cost-effective amendment for contaminated soil reclamation and remediation. Soil dry-stress experiments are conducted, where petroleum hydrocarbon (PHC)-contaminated soils amended with K-form zeolite are compared against unamended contaminated soils. Results indicate that amended soils display enhanced soil-water retention, and significantly greater bacterial growth, proving the biocompatibility of the K-form zeolite. Providing K (macronutrient) and retaining liquid water is critical for stimulating indigenous PHC-degrading bacteria for effective bioremediation of contaminated soils in cold climates. Upcoming freeze/thaw stress experiments will simulate the effects of cold climates on indigenous PHC-degrading bacteria by comparing the bacterial survival rate in microcosms amended with K-form zeolite against unamended controls. The K-form zeolite is anticipated to act as bacterial microhabitat and shelter the bacteria from freeze/thaw stresses, surpassing the traditional seasonal limitations of effective bioremediation in Canada. This study suggests the K-form zeolite produced from potash tailings and brine can be recycled as a cost-effective biostimulant and soil amendment for enhancing intrinsic microbial activity in contaminated settings. Concluding remarks include an overview of how this research may establish an innovative circular economy approach within the Canadian potash sector by converting mining byproducts into a cost-effective bioremediation agent.

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Dr. Wonjae Chang

Biography