Insights into the activation of ozonation by hydroxylamine: Influential factors, degradation mechanism and reaction kinetics

The decontamination of prometon (PMT) by ozone/hydroxylamine hydrochloride (O 3 /HAC) was systematically investigated in this study with focus on the degradation mechanism and kinetics. Experimental results revealed that there was an enhancement of PMT degradation efficiency by 42.1% and the pseudo-first-order rate constant by more than 5.7 times in O 3 /HAC process under low HAC dosage (5 mg L −1 ) after 3 min in comparison with O 3 alone. The second-order rate constant of PMT with hydroxyl radical ( • OH) was determined to be (1.84 ± 0.1) × 10 9 M −1 s −1 and 7.80 × 10 9 M −1 s −1 via competition kinetics and • OH steady-state hypothesis, respectively. The PMT removal in O 3 /HAC process was highly pH-dependent and the optimum degradation performance was achieved under pH 5.0. In addition, • OH and singlet oxygen were identified as the primary reactive oxygen radicals in O 3 /HAC process. Meanwhile, eleven transformation products of PMT were identified and possible degradation mechanisms were proposed. Moreover, a kinetic model based on chemical kinetics and steady-state hypothesis was developed and modified to predict the PMT abatement in O 3 /HAC process. The results demonstrated that the O 3 /HAC process provided a promising alternative for refractory organic pollutants decontamination in water treatment.