Treatment of solutions containing nonylphenol ethoxylate by photoelectrooxidation

Abstract

In this work the photoelectrooxidation (PEO) was applied in the treatment of a solution containing nonylphenol ethoxylate surfactant (NP4EO). The use of different lamps (125 and 250W), current density (5 and 10mAcm−2) and treatment time (0, 60, 120, 180 and 240min) were investigated. The samples were characterized by UV/Vis, total organic carbon (TOC), gas chromatography associated to mass spectroscopy (GC/MS) and ecotoxicity. The reaction kinetics were calculated and the light flux and pH were measured. The results of analysis by UV/Vis show that there is degradation of nonylphenol ethoxylated in the treatment time of 240min for all configurations, and the configurations that used a 250W lamp and a current density of 10mAcm−2 obtained better results, with a reduction of 83% in TOC, indicating a high mineralization of the surfactant. It was further found in the GC/MS that the configurations that used the 125W lamp promoted a smaller incident light flux on the solution, and, regardless of the applied current density, it was generated the reaction intermediate nonylphenol, more toxic than the parent compound. The opposite can be observed when a 250W lamp was used, which produced a higher incident light flux. Based on the degradation products detected, a simplified mechanism for degradation of nonylphenol ethoxylate was proposed. Although a treatment time of 240min with photoelectrooxidation with different configurations was not effective in the complete mineralization of the compound, a promising process was developed with the treatment using a lamp of 250W and a current density of 10mAcm−2, which generated a solution with less toxicity than the original one.