Degradation of nitrobenzene-containing wastewater by sequential nanoscale zero valent iron-persulfate process

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.

Keywords

• Nanoscale zero valent iron
• Impinging stream-rotating packed bed
• Sequential NZVI-Na2S2O8 process
• Nitrobenzene
• Degradation pathways