Integrated Remediation of Sulfate, Iron, and Aluminum Present in Acidic Minewater With an Emphasis on Value Added Product Recovery.

Water quality analysis of samples from regions of northeastern parts of India affected by the problem of acidic mine discharge (AMD) revealed high concentrations of aluminum, sulfate, and iron. AMD water in the region is a suitable candidate for in situ ettringite precipitation, serving as a motivation behind the current research. The study explores the effectiveness of integrated nanofiltration (NF), and in situ ettringite (hydrous calcium aluminum sulfate) precipitation for remediation of acid mine drainage (AMD), targeting key contaminants: sulfate, iron, and aluminum. Stagewise chemical precipitation, optimized by precise pH control and reagent dosing, combined with cross-flow nanofiltration in the downstream, demonstrated over 90% contaminant removal efficiency. The presence of aluminum ions was found to have a synergistic effect on sulfate removal, leading to enhanced contaminant removal. NF membranes, integrated into the treatment process were able to remove sulfate concentrations to less than 10 mg/L. Ettringite precipitation were carried out by pH modification. XRD peaks demonstrated crystalline ettringite formation at a precise pH range of 11.5-12.5. In situ ettringite precipitation showed promise as a sustainable remediation strategy, encapsulating contaminants within a stable crystalline structure and achieving 90% aluminum reduction. This integrated remediation technique not only simplifies the treatment methodology but also offers a comprehensive solution for AMD treatment compared to standalone techniques.