Abstract:

Acid mine drainage (AMD) remains a significant environmental challenge in mining-impacted watersheds, characterized by low pH and elevated concentrations of heavy metals and sulfates. Building upon prior research demonstrating that seawater irrigation reduces pyrite reactivity and suppresses iron-oxidizing bacteria such as Acidithiobacillus ferrooxidans at chloride concentrations of ~19 g/L or below, this study proposes the use of a lower-concentration chloride solution in a simulated waste rock system to achieve cost-effective in situ remediation.

Column leaching experiments are proposed using columns (16 cm height, 10 cm diameter) packed with pyritic material and exposed to synthetic AMD containing 10 g/L Fe and 0.03 g/L Cu. A total of 2 L of 5 g/L chloride solution will be irrigated from the top at varying inlet fluxes ranging from 8 to 84 L/m²/hr. The experiments aim to investigate changes in Fe and Cu concentrations in the leachate, iron precipitation and chloride breakthrough, and the efficiency of bacterial suppression as a function of irrigation flux, with the goal of preventing ongoing AMD generation through reduced sulfide mineral oxidation and microbial activity.

This work is expected to identify an optimal inlet flux that maximizes iron precipitation, bacterial kill efficiency, and metal retention while minimizing chloride consumption and loss. The proposed approach has the potential to provide a highly cost-effective and sustainable strategy for AMD mitigation using low-chloride irrigation, offering a practical alternative to conventional limestone-based treatments for active and legacy mine sites

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