Degradation of p-nitrophenol (PNP) in aqueous solution by Fe-0-PM-PS system through response surface methodology (RSM)

To develop a technology for the degradation of the toxic and refractory pollutants, the Fe-0-PM-PS system and 6 control experiments were setup in this study. First, effects of Fe dosage (0-18.3 g/L), PM dosage (0-25.0 mmol/L), PS dosage (0-30.0 mmol/L), initial pH value (3.0-11.0), air flow rate (0-2.0 L/min), and feeding times of PM and PS (1-5) on the degradation of PNP in aqueous solution by the Fe-0-PM-PS system were studied through the single-factor experiment. Furthermore, the optimized experimental conditions (i.e., Fe-0 dosage of 11.9 g/L, PM dosage of 15.0 mmol/L, PS dosage of 18.1 mmol/L and feeding times of oxidants of 4) were obtained through response surface methodology (RSM). The result shows that the maximum COD removal efficiency (89.0%) was obtained by the Fe-0-PM-PS system under the optimal conditions, which was mainly attributed to the strong synergistic effect among Fe-0, PM and PS. In addition, PNP degradation pathway was proposed according to the intermediates detected by HPLC. According to the analysis results of SEM-EDS, XRD and XPS, the reaction mechanism of the Fe-0-PM-PS system has been clarified thoroughly. In short, these results suggest that the Fe-0-PM-PS system should be proposed as an effective pretreatment process for the toxic and refractory PNP wastewater. (C) 2016 Elsevier B.V. All rights reserved.