Oxidative degradation of chloroxylenol in aqueous solution by thermally activated persulfate: Kinetics, mechanisms and toxicities

Chloroxylenol (PCMX) degradation by thermally activated persulfate (TAP) in aqueous solution and the toxicity changes of the system were investigated. PCMX oxidative degradation followed a pseudo-first-order kinetic model. The apparent activation energy of PCMX degradation was calculated to be 130.0 kJ.mol(-1), according to the Arrhenius equation, over the range of 30-60 degrees C. The PCMX degradation efficiency was significantly increased with the reaction temperature and initial persulfate concentration, while it was not influenced by the initial solution pH or water matrices. The hydroxyl radicals and sulfate radicals (SRs) in the TAP system were proved by electron paramagnetic resonance (EPR) spectroscopy. SRs were the predominant radical species at neutral pH, as verified by radical scavenging tests. The possible degradation pathways, including electron transfer, dechlorination, aromatic ring oxidation, side-chain oxidation and a subsequently opening aromatic ring, were proposed based on intermediate detection. The acute toxicity and genotoxicity of the PCMX degradation solution were estimated by the Escherichia coli and Acinetobacter baylyi ADP1_recA_lux bioreporter, respectively. The results suggested that TAP was a feasible and environmentally friendly technology for PCMX-contaminated water remediation.