Highly selective oxidation of organic contaminants in the RuIII-activated peroxymonosulfate process: The dominance of RuVO species

Ruthenium (RuIII)-activated peroxymonosulfate (the RuIII/PMS process) is one of the most efficient PMS-based advanced oxidation processes for the abatement of organic contaminants. Here we interestingly found that phenyl methyl sulfoxide (PMSO) was significantly oxidized to phenyl methyl sulfone (PMSO2) in the RuIII/PMS process at the pH range of 3.0-6.0, with the conversion ratio of ΔPMSO to ΔPMSO2 was close to 100%, which favored the dominance of high-valent ruthenium-oxo species (RuVO) instead of the widely-recognized radicals (i.e, hydroxyl radical and sulfate radical). Scavenging experiments further indicated that RuVO was unreactive to tert-butyl alcohol, but could be scavenged by methanol and dimethyl sulfoxide. Besides, sulfamethoxazole, acetaminophen, carbamazepine, diclofenac, 2,4,6-trichlorophenol were readily degraded in the RuIII/PMS process, but atrazine, ibuprofen, benzoic acid and 4-nitrobenzoic acid were barely removed, suggesting the high selectivity of RuVO species. This study enriched the understandings on the mechanism of RuIII-mediated PMS activation and the nature of RuVO species.