Heterogeneous catalytic ozonation process for removal of 4-chloro-2-nitrophenol from aqueous solutions

This research investigated the efficiency of nanosized ZnO in the catalytic ozonation of 4-chloro-2-nitrophenol and determined the effect of pH on heterogeneous catalytic ozonation. Use of ozone with ZnO catalyst leads to conversion of 98.7% of 4-chloro-2-nitrophenol during 5 min. In addition, it was found that in ZnO catalytic ozonation, the degradation efficiency of 4-chloro-2-nitrophenol was higher at low pH conditions (pH 3.0) than high pH (pH 7–9). This result was not in accordance with ozonation alone, following which higher pH had positive effect on the degradation of 4-chloro-2-nitrophenol. During the catalytic ozonation of 4-chloro-2-nitrophenol, an increase of nitrate ions in water sample solution was observed. At pH = 3, the concentration of nitrate formed during nano-ZnO catalytic ozonation was 7.08 mg L⁻¹ and the amount of total organic carbon was 54.9% after 30 min.