Experimental treatment of pickled vegetable wastewater by electrofenton method based on modified PbO2 electrode

Abstract

The pickle industry is acknowledged as one of the most environmentally harmful sectors within the food industry. The elevated concentrations of chemical oxygen demand (COD), total phosphorus (TP), ammonium nitrogen (NH₄⁺-N), and salinity found in pickle wastewater present significant environmental challenges. To tackle these issues, this study investigates the efficacy of a La-doped Ti/SnO₂-Sb₂O₅/La-PbO₂ electrode employing an electro-Fenton method for the treatment of pickle wastewater. Experimental design was performed using response surface methodology to identify optimal operational parameters. Results demonstrate that all processes adhere to pseudo-first-order reaction kinetics. Under conditions where the degradation temperature is maintained at 65 °C, current density at 100 mA cm⁻², pH at 4.1, FeSO₄ concentration at 3.03 mmol L⁻¹, and H₂O₂ concentration at 2.07 mmol L⁻¹ with six additions over a degradation period of 240 minutes, COD removal achieved an impressive rate of 92.87 %, while ammonium nitrogen removal reached a remarkable rate of 95.26 %. In comparison to traditional electrochemical methods, both COD and ammonium nitrogen removal rates exhibited substantial improvements; furthermore, hydroxyl radicals (•OH) played a pivotal role in facilitating the radical quenching degradation process. The operation cost analysis shows that the electric Fenton process has a lower operation cost, which provides a good opportunity for the food industry to treat Pickled vegetables wastewater. The operating cost for COD removal rate is 1.262 $ m⁻³kg⁻¹, and the operating cost for ammonia nitrogen removal rate is 1.355 $ m⁻³kg⁻¹.