The bromate formation accompanied by the degradation of 2,4-bromophenol in UV/peroxymonosulfate

Abstract

This study explored the degradation kinetics of 2,4-bromophenol (2,4-DBP) and the fate of bromine affected by different water matrix (i.e., dissolved organic matter (DOC), chloride ions (Cl−)) and operation conditions (i.e., peroxymonosulfate (HSO5−) dosage, 2,4-DBP concentration, and solution pH) in UV/HSO5− process. Results showed that there was a linear positive correlation between the apparent pseudo-first order rate constant of 2,4-DBP degradation (kobs) and HSO5− dosage. The kobs decreased as the initial 2,4-DBP concentrations increased, and significantly increased by raising the pH value from 5 to 9. The presence of Cl− had negligible effect on the degradation of 2,4-DBP in UV/HSO5− process, while DOC showed the remarkable inhibitory effect. In addition, results indicated that the formation of bromate (BrO3−) from 2,4-DBP oxidation exhibited biphasic kinetics under various conditions (i.e., BrO3− was undetectable in the lag phase and rapidly generated in the secondary phase). The yield of BrO3− increased up to 100% when HSO5− dosage was higher than 500 μM. The longer lag-phase of BrO3− formation was observed when the initial 2,4-DBP concentration increased from 1 μM to 10 μΜ, while the formation rate and concentration of BrO3− were promoted. The lag phase of BrO3− formation at pH 5 was shorter than that at pH 7 (i.e., 0 min vs 5 min), while no BrO3− was detected at pH 9. The presence of Cl− (1–5 mM) suppressed BrO3− formation significantly. DOC could scavenge the generated HOBr/OBr− and bromine atom (Br·) to inhibit the yield of BrO3−. This study suggested that bromophenols could be degraded effectively by UV/HSO5− process, whereas the great potential of BrO3− formation should be paid attention to during advanced oxidation of bromine-containing aromatic compounds.