Bridging Geochemistry and Chemical Engineering: A Comprehensive Approach To Acid Mine Drainage Remediation and Water Recovery

Abstract

Acid Mine Drainage is a persistent environmental problem associated with coal and metal mining. This is characterized by extreme low pH, elevated sulfate levels, and mobilized metals which causes considerable degradation of the surrounding ecosystems. In this study, we develop an integrated approach for assessing the viability of AMD mitigation combining statistical interpretation of water chemistry, geochemical modeling, and engineered treatment design. Multivariate analyses were conducted to determine how pH, sulfate, and dissolved metals are interrelated. It demonstrated distinct co-mobilization patterns that provided insight into the dominant controls on AMD composition. Geochemical modelling using PHREEQC on AMD samples collected from northeastern India was used to assess mineral stability trends correlating saturation index values with Pourbaix plots. The results highlighted pH-dependent precipitation of major metals such as Fe and Al, as well as the importance of redox conditions in determining sulfate degradation and metal speciation. The majority of variance in AMD chemistry was due to the collective behavior of sulfate and several trace metals. A smaller component represented the influence of pH-related parameters, with strong sulfate─metal linkages broadly confirming its key role in governing metal mobility. Utilizing the insights gained from geochemical modelling, a two-step treatment train was proposed. This consisted of an upstream chemical precipitation step (simulated in AMDTreat) followed by a downstream membrane-based separation step that was modelled in AquaGRID. The integrated system demonstrated removal of major contaminants from acidic discharge. The final water quality approached potable standards, while minimising sludge production as well as energy consumption