Photo-persulfate oxidation and mineralization of benzoic acid: Kinetics and optimization under UVC irradiation.

The strong oxidant, persulfate (PS, S 2 O 8 2−), was applied to treat the synthetic wastewater of benzoic acid (BA) under UV irradiation. UVC light initiated a chain reaction that derived the sulfate radical (SO 4 •-) and hydroxyl radical (HO•) from S 2 O 8 2− ion. The experiment parameters, including light irradiation (UVA and UVC), pH, dose ratio ([PS] 0 /[BA] 0), initial concentration ([BA] 0 , mg/L), was optimized based on degradation efficiency and total organic carbon (TOC) removal of BA, which reached up to 100% and 96%, respectively, under pH 3.0. The best dose ratio was close to equivalent stoichiometry (and [PS] 0 /[BA] 0 = 15) for the treatment of 100 mg-BA/L, suggesting that UV/S 2 O 8 2− was able to completely convert BA to carbon dioxide and water. The scavenging test showed that SO 4 •- contributed to about 60% of degradation rate, which the HO• predominated the mineralization rate, i.e., TOC removal. A consecutive kinetic model was proposed to clarify the reaction sequence and rate-determining factor of photo-persulfate oxidation for benzoic acid. [Display omitted] • The UVC-persulfate oxidation of benzoic acid was investigated. • Up to 100% of Benzoic acid was degraded within 1 h. • Up to 96% of TOC was mineralized within 1 h. • Sulfate radical is the predominant agent in benzoic acid mineralization. [ABSTRACT FROM AUTHOR]