Meta-cresol degradation by persulfate through UV/O3 synergistic activation: Contribution of free radicals and degradation pathway

The kinetic and pathway of meta-cresol (m-cresol) degradation were studied by persulfate oxidation through UV/ozone activation (UV/O-3-Na2S2O8) to improve m-cresol removal to eliminate ecological risks. Experimental results showed that the degradation effect of m-cresol with an initial concentration of 50 mg/L was 99.8% in 30 min under the optimization conditions. The reaction kinetic model in the UV/O-3-Na2S2O8 system shows that the initial pH value, the respective ozone, and the persulfate dosage were positively correlated with the degradation rate constant value (k). The apparent degradation rate of m-cresol in the UV/O-3-Na2S2O8 system was 0.2216 min(-1), and the synergy factor (f) was larger than 1, thereby demonstrating a synergistic effect of UV, ozone, and persulfate. The dominant free radicals in the system were sulfate radical (SO- 4 center dot) and hydroxyl radical (center dot OH), and the contribution ratio of SO- 4 center dot to m-cresol degradation was higher than center dot OH. The degradation process of m-cresol by UV/O-3 - Na2S2O8 was mainly through the electrophilic addition reaction to substitute the ortho- and para-positions of the hydroxyl group on the benzene ring, followed by the ring-opening reaction and mineralization of the aliphatic compound to achieve the complete degradation of m-cresol. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

The kinetic and pathway of meta-cresol degradation were studied by persulfate oxidation through UV/ozone activation to improve m-cresol removal and eliminate ecological risks. The synergistic effect of UV, ozone, and persulfate was observed in the degradation process, with sulfate radical and hydroxyl radical identified as the dominant free radicals. The degradation mechanism involved electrophilic addition reaction, ring-opening reaction, and mineralization of the aliphatic compound to achieve complete degradation of m-cresol.