Synergistic electrocoagulation in a self-induced airlift reactor: A leap towards energy-efficient and sustainable tannery wastewater remediation

Tannery wastewater is a challenging effluent due to its high concentrations of chromium, total sulfides, and recalcitrant organic compounds. This study presented a novel electrocoagulation (EC) process using a self-induced external-loop airlift reactor (ELAR), which operated without mechanical mixing and relied on hydrogen and oxygen microbubbles for internal circulation. Under optimal conditions (pH of 6, a current density of 50 mA/cm², an electrolysis time of 20 min), the ELAR achieved high pollutant removal efficiencies (88% chemical oxygen demand (COD) removal and 92% Cr removal) with lower energy consumption (10.8 kW·h/m³) and reduced operational costs (1.83 USD per cubic meter) compared to a stirred tank reactor. Artificial neural network (ANN) modeling enabled data-driven optimization, further improving COD removal to 94% with reducing energy input. Kinetic and isotherm analyses confirmed chemisorption as the dominant mechanism. Life cycle assessment (LCA) and solar integration scenarios highlighted the environmental benefits of the ELAR system. Sludge characterization indicated potential for reuse as construction materials. This study uniquely introduced an ELAR system that operates without mechanical agitation, combined with ANN modeling and LCA, representing the first integrated approach for optimizing and assessing EC performance in tannery wastewater treatment. These findings demonstrate that the ELAR system offers a cost-effective and sustainable solution for industrial wastewater remediation.