Degradation of nitrobenzene-containing wastewater by sequential nanoscale zero valent iron-persulfate process
Jingjuan Qiao, Weizhou Jiao, Youzhi Liu
Abstract
As nitrobenzene (NB) is structurally stable and difficult to degrade due to the presence of an electron withdrawing group (nitro group). The sequential nanoscale zero valent iron-persulfate (NZVI-Na2S2O8) process was proposed in this study for the degradation NB-containing wastewater. The results showed that the NB degradation efficiency and the total organic carbon removal efficiency in the sequential NZVI-Na2S2O8 process were 100% and 49.25%, respectively, at a NB concentration of 200 mg L−1, a NZVI concentration of 0.75 g L−1, a Na2S2O8 concentration of 26.8 mmol L−1, an initial pH of 5, and a reaction time of 30 min, which were higher than those (88.53% and 35.24%, respectively) obtained in the NZVI/Na2S2O8 process. Sulfate radicals (SO4·−) and hydroxyl radicals (OH) generated in the reaction were identified directly by electron paramagnetic resonance spectroscopy and indirectly by radical capture experiments, and it was shown that both SO4·− and OH played a major role in the sequential NZVI-Na2S2O8 process. The possible pathways involved in the reduction of NB to aniline (AN) and the further oxidative degradation of AN were determined by gas chromatography-mass spectrometry.