Pretreatment of sulfonic acid wastewater by iron-carbon micro-electrolysis

The treatment of sulfonic acid wastewater poses significant environmental challenges due to its high concentration and non-biodegradable nature. As a typical refractory industrial wastewater, its improper treatment not only causes water pollution but also restricts the reuse of water resources, which is contrary to the goal of improving water conservation. This study focuses on utilizing Fe-C micro-electrolysis for the pretreatment of sulfonic acid wastewater to improve the removal of persistent organic pollutants. A comprehensive investigation of the factors that impact on COD removal, Fe ³⁺ concentration, pH and chromaticity, such as influent concentration, pH, aeration volume and reaction time. Response surface methodology (RSM) was used to investigate factor interactions and optimize operational parameters for Fe-C micro-electrolysis. The optimal conditions were determined as follows: aeration rate = 16.63 L/min, retention time = 79.37 min, and pH = 1.268, achieving a chemical oxygen demand (COD) removal efficiency of 45.24%. The degradation of sulfonic acid wastewater by Fe-C micro-electrolysis followed second-order reaction kinetics (R²=0.996). Furthermore, Various techniques including FT-IR and UV-Vis spectra showed that the water samples of sulfonic acid mainly contained two kinds of organic matter: methanesulfonic acid and alkylbenzene sulfonic acid. In sulfonic acid wastewater, the degradation of highly unsaturated small-molecule pigment compounds and organic moieties with intramolecular conjugated systems occurred through chain cleavage and ring-opening reactions, leading to the formation of other small molecules and partial dismantling of organic pollutants. This approach significantly reduces the pollution load of sulfonic acid wastewater, thereby creating conditions for subsequent advanced treatment and reuse and contributing to enhanced water conservation measures.