Decomposition and mineralization of sulfaquinoxaline sodium during UV/H2O2 oxidation processes
Abstract Sulfaquinoxaline sodium (N'1 quinoxalin 2 ylsulphanilamide sodium, SQ Na) has been widely used to prevent coccidiosis in poultry, swine, and sheep. The quinoxaline group within SQ Na exhibits mutagenic and carcinogenic properties. The removal of residual SQ Na from wastewater has not been reported before. In this study, the decomposition of SQ Na in aqueous solutions in UV/H2O2 oxidation process was investigated. The results show that SQ Na was completely decomposed during UV/H2O2 oxidation process, and the process fitted a fluence based pseudo first order kinetics model when the initial H2O2 concentration varied from 0 to 160 mg/L with rate constant of kobs 0.802 x [H2O2] 0.206 x 10 3, (R2 0.990) The decomposition of SQ Na via UV/H2O2 process was favorable under acidic and neutral conditions but was inhibited under strong alkaline conditions (pH 11) The presence of bicarbonate, chloride and nitrate ions were shown to have slight inhibition on the decomposition, but humic acids significantly decreased the decomposition rate. As compared with in deionized water, the decomposition rate of SQ Na in surface water and wastewater treatment plant (WWTP) effluent was significantly decreased at 80 mg/L of H2O2, but the decrease was mitigated with more H2O2 addition. The decomposition products of SQ Na were identified using ion chromatography and liquid chromatography with an ion trap and time of flight mass spectrometry (LCMS IT TOF) Based on these decomposition products, the possible decomposition pathways of SQ Na in the UV/H2O2 oxidation process were proposed.