Optimization on homogeneous Fenton advanced treatment of tannery wastewater using response surface methodology

Classical homogeneous Fenton was used to further treat tannery wastewater. Wastewater samples were effluent of A/O biological reactor with COD of 180~200 mg·L ^-1. Based on Box-Behnken response surface methodology, the primary focus of this paper is to evaluate simple and combined effects of initial pH, molar ratio of H ₂O ₂ to Fe ²⁺, H ₂O ₂ dosage, and reaction time, establish an empirical mathematical model between COD removal rate and the above influence factors, and optimize the removal efficiency in Fenton process. The results demonstrated that the significance of influence factors followed the order: pH>H ₂O ₂ dosage>reaction time>H ₂O ₂/Fe ²⁺ molar ratio and the combined effect of initial pH and H ₂O ₂ dosage was significant. Furthermore, a satisfactory prediction second-order regression model was derived by response surface methodology. The optimal reaction conditions with the highest COD removal rate of 55.87% were determined to be pH=4.0, H ₂O ₂ dosage=14.00 mmol·L ^-1, time=3 h and T=25 °C.The experimental results using the above optimal conditions had an average COD removal of 53.35%. The experimental value agreed with the predicted value with 4.51% deviation. Finally, classical homogeneous Fenton process can be adopted for advanced treatment of tannery wastewater to meet the first discharge standard of COD≤100 mg·L ^-1 in Integrated Wastewater Discharge Standard (GB8978-1996).