Degradation of nitrobenzene by sodium persulfate activated with zero-valent zinc in the presence of low frequency ultrasound

In the presence of low frequency ultrasound (US) generated from an ultrasonic cleaning bath, the degradation efficiency of nitrobenzene (C 6 H 5 NO 2 , NB) by Zn 0 -activated persulfate (PS) reached 96% within 2   h, which is much higher than that by PS or Zn 0 alone in the presence of US or that by Zn 0 -activated PS in the absence of US. The synergistic effect in the US/Zn 0 /PS system and the optimum degradation conditions was investigated by batch experiments. The variations of pH and concentrations of Zn 2+ and SO 4 2− over time and the removal of chemical oxygen demand (COD) and total organic carbon (TOC) in different systems were analyzed, which agreed well with the degradation pattern of NB in different systems. The formation of free radicals was measured using electron paramagnetic resonance (EPR) spectroscopy to further investigate the possible mechanism of the enhanced degradation of NB by Zn 0 -activated PS in the presence of low frequency US.