Rapid degradation of atrazine by a novel advanced oxidation process of bisulfite/chlorine dioxide: Efficiency, mechanism, pathway

Recently, (bi)sulfite as the precursor of SOx center dot- generation has drawn significant attention in advance oxidation process based on SO4 center dot-(SR-AOP) due to its low cost and conforming to waste utilization. The current activation on (bi)sulfite mainly employs the transition metals and their composite materials, which limited its application. In this study, chlorine dioxide (ClO2) was employed to activate bisulfite (BS). It was found that the dominant radicals in BS/ClO2 process were ClO center dot and SO4 center dot- according to scavenger experiments and ESR detection. To investigate the performance of the established BS/ClO2 system, atrazine (ATZ) was used as target pollutant. The degradation efficiency of ATZ reached 86.8% within 3 min and nearly half of the degradation occurred at the first 10 s. The optimum ClO2 dosage for the ATZ degradation was 100 mu M when the BS dosage was 200 mu M. The effects of pH, temperature and coexisting substances including halide ions, bicarbonate ion and humic acid on ATZ degradation by BS/ClO2 were investigated. It is predicted that the degradation pathway of ATZ in this study involved olefination, dealkylation and the combination of dichlorination with hydroxylation according to the final products identified after degradation. The system has also shown the ability on degradation of four pharmaceuticals and personal care products (PPCPs) including ibuprofen, bisphenol A, sulfamethoxazole and carbamazepine. This study reveals that ClO2 is capable of activating BS and provides a method for effectively degrading refractory organic contaminants.