Electrocoagulation for the simultaneous removal of copper and arsenic from acid mine drainage: Performance and...

Mining activities generate acid mine drainage (AMD), an extremely acidic effluent laden with multiple co-contaminants that pose formidable challenges to conventional remediation technologists. This study systematically investigated the performance and mechanisms of iron-electrocoagulation (Fe-EC) for the simultaneous removal of arsenic (As) and copper (Cu) from AMD. Results indicated that the optimized operational parameters for Fe-EC were a current density of 80 A m^-2, stirring speed at 150 rpm, and without aeration, resulting in removal efficiencies exceeding 98% for both As(III) and Cu(II). Exhibiting remarkable robustness against typical AMD matrix effects (initial pH ≥ 3, 800 mg L⁻¹ Fe(II), and 4000 mg L⁻¹ SO₄²⁻), the system sustained high removal rates of 94.6% for As(III) and 96.6% for Cu(II), demonstrating its potential for practical application. Notably, under Fe(II)-Cu(II)-As(III) coexistence, the optimized Fe-EC strategy leveraged the inherent synergistic interactions to maintain high-efficiency removal of both contaminants. Specifically, Fe(II) and Cu(II) synergistically catalyzed Fenton/Fenton-like reactions, accelerating As(III) oxidation and removal while facilitating the formation of stable Fe-Cu mineral phases such as CuFe₂O₄. Simultaneously, As(III) acted as a path-directing ligand, facilitating copper immobilization through disrupting the Cu(I)-Fe(III) redox cycle. Comparative experiments with chemical coagulation demonstrated the superior performance of Fe-EC, while treatment of authentic AMD samples validated its practical applicability. This work provides critical insights into the fundamental interfacial mechanisms governing multi-contaminant removal in Fe-EC systems, offering a mechanistic and engineering foundation for the rational design of efficient electrochemical treatment strategies tailored to the complex chemistry of AMD.