Degradation of Nonylphenol Ethoxylate-40 in High Saline Wastewater by Electrochemical Oxidation.

Nonylphenol ethoxylate-n (NPnEO) is a nonionic surfactant, and can be degraded in chemical and biological ways for short-chain NPnEO with n ≤ 10. However, when n is >10, the degradation of NPEO in wastewater was seldom reported. In this study, the electrochemical oxidation of long-chain NP40EO at high saline wastewater was investigated. The main influencing factors such as current density, plate distance, initial pH, salt type, and salt concentration on electrochemical degradation of high saline NP40EO wastewater were evaluated. The chemical oxygen demand (COD) removal efficiency increased with the increase of current density and reached 73.4% at 45 mA/cm2 after 6 h electrolysis. Plate distance had no effect on the COD removal. As compared with sodium sulfate (Na2SO4), sodium chloride (NaCl) solution led to better COD removal. A high COD removal efficiency was obtained at lower initial pH value. A possible electrochemical degradation pathway of NP40EO was proposed. The energy consumption increased with increasing current density, plate distance, initial pH value, and decreasing NaCl concentration. Based on the energy consumption analysis, the optimal operating parameters were obtained at current density of 30 mA/cm2, plate distance of 2.0 cm, NaCl concentration of 0.50 M, and initial pH value of 3.0. This result indicated that electrochemical advanced oxidation process is a feasible way for the treatment of long-chain NP40EO wastewater at high saline conditions. [ABSTRACT FROM AUTHOR]