Treatment of mining wastewater polluted with cyanide by electrooxidation: A mechanistic study, with integrated Modeling and kinetic study

Electrooxidation offers a promising approach for treating cyanide-contaminated mining wastewater, but performance depends on both electrode material and operating conditions. This study integrates a mechanistic investigation with regression modeling and kinetic analysis to evaluate cyanide removal using boron-doped diamond (BDD), mixed metal oxide (MMO), and graphite anodes. A 3 2 full factorial design was applied, varying current density (10–1000 A m −2 ) and anode type, with additional tests in real mining waters to assess matrix effects. Time-resolved measurements allowed kinetic modeling in MATLAB, targeting reduction of cyanide to below 1 mg dm −3 . Mechanistic pathways were elucidated through ion chromatography and supported by literature, revealing that BDD facilitates both direct oxidation and sulfate-mediated radical generation, while MMO and graphite operate primarily via chlorine-mediated indirect oxidation. BDD consistently achieved the fastest and most complete cyanide removal, with higher current densities driving progression toward highly oxidized chlorine species. MMO demonstrated moderate efficiency, limited by its lower oxygen evolution overpotential, and graphite showed poor performance due to surface degradation at higher current densities and low anodic potential. Regression modeling identified log-transformed current density and water source as significant predictors of early-stage cyanide removal, while electrode material controlled final removal performance. The combined mechanistic and statistical insights support empirical process interpretation within the investigated operating range and provide guidance for further optimization of electrochemical cyanide remediation while considering byproduct formation.