Efficiency chloride removal based on mono-variable experimental data in electrocoagulation with aluminium and stainless-steel electrodes

Galvanizing effluent, characterized by extreme chloride concentrations, poses significant environmental and infrastructural risks due to its persistence and corrosivity. Conventional chloride removal methods are often impractical for small-to-medium industries, necessitating cost-effective alternatives. This study optimized electrocoagulation (EC) using aluminium (AI) and stainless-steel (SS) electrodes to treat high-chloride galvanizing wastewater, integrating mono-variable experiments with Response Surface Methodology (RSM) to maximize efficiency. AI electrodes outperformed SS due to favorable electrochemical reactivity, generating Al³⁺ coagulants that adsorb chloride via Al(OH)₃ flocs. Inter-electrode distance (2–10 cm), current (1–3 A), electrolysis time (0–100 min), pH (7–11), and electrode configuration (monopolar, monopolar-sacrificial, dipolar) were the key variables systematically evaluated. RSM analysis revealed a cubic model best described chloride removal dynamics for aluminum, with dipolar (DP) configuration achieving superior current distribution and mass transfer (61.4 % removal at 2 cm spacing, 3 A, 80 min). Optimal pH was critical: peak efficiency (60.7 % chloride removal, 85.6 % current efficiency) occurred at pH 8, where Al(OH)₃ floc formation maximized charge utilization. Deviations (pH 6 or >8) reduced efficiency due to soluble aluminum species. Energy and electrode consumption were minimized (65.9 kWh/m³, 1.08 kg/m³) under optimized conditions. The DP configuration’s uniform charge transfer mitigated ohmic losses and enhanced floc-Cl⁻ contact, proving most viable for real effluents. This work establishes a scalable EC framework, demonstrating aluminum-based electrocoagulation as a robust, chemical-free solution for high-chloride industrial wastewater.