Electrocoagulation of wastewater from Haldia industrial belt: adsorption, kinetic and process optimization

This study explored the treatment of Haldia industrial belt wastewater (HIBWW), which contains high pollutant loads from chemical facilities in the Haldia region of West Bengal, India. The study uses a customized electrocoagulation cell to remove TSS and other contaminants. The electrocoagulation cell consists of iron and aluminum as the anode and cathode. Key operating parameters, including the pH, oil concentration, electrolysis time, and current density, were optimized using a central composite design within response surface methodology. Adsorption isotherm, kinetic, and thermodynamic analyses were conducted to uncover the adsorption mechanism and evaluate the efficiency of the electrocoagulation system for HIBWW. An optimal TSS removal rate of 72% was achieved with 92% desirability at pH 5, initial oil concentration of 50 mg/L, current density of 30 mA/cm², and reaction time of 35 min, higher than the value reported earlier. Additionally, the removal efficiencies for turbidity, total dissolved solids, chemical oxygen demand, and biological oxygen demand were 90%, 75%, 53%, and 63%. Based on the isotherm analysis, the Langmuir model produced the best fit (R² = 0.9986), suggesting monolayer adsorption on the floc surface. The first-order kinetic model exhibited a higher regression coefficient than the second-order model, indicating physisorption-dominated adsorption driven by charge neutralization and particle aggregation. The Gibbs free energy (∆Go: − 24.16 kJ/mol to − 20.60 kJ/mol) also suggested that adsorption occurred through physisorption. The treatment cost for HIBWW including equipment, waste disposal, power consumption, and labor, varies from approximately ₹470/m³ to ₹479/m³. The findings of the present study offer guidelines for improving the treatment efficiency of HIBWW and support environmental sustainability in accordance with United Nations 2030 Sustainable Development Goals and the long-term sustainability roadmap for 2050.