Theoretical investigation on the contribution of HO, SO and CO radicals to the degradation of phenacetin in water: Mechanisms, kinetics, and toxicity evaluation.

Indirect oxidation induced by reactive free radicals, such as hydroxyl radical (HO), sulfate radical (SO) and carbonate radical (CO), plays an important or even crucial role in the degradation of micropollutants. Thus, the coadjutant degradation of phenacetin (PNT) by HO, SO and CO, as well as the synergistic effect of O on HO and HO were studied through mechanism, kinetics and toxicity evaluation. The results showed that the degradation of PNT was mainly caused by radical adduct formation (RAF) reaction (69% for Г, the same as below) and H atom transfer (HAT) reaction (31%) of HO. For the two inorganic anionic radicals, SO initiated PNT degradation by sequential radical addition-elimination (SRAE; 55%), HAT (28%) and single electron transfer (SET; 17%) reactions, while only by HAT reaction for CO. The total initial reaction rate constants of PNT by three radicals were in the order: SO > HO > CO. The kinetics of PNT degradation simulated by Kintecus program showed that UV/persulfate could degrade target compound more effectively than UV/HO in ultrapure water. In the subsequent reaction of PNT with O, HO and HO, the formation of mono/di/tri-hydroxyl substitutions and unsaturated aldehydes/ketones/alcohols were confirmed. The results of toxicity assessment showed that the acute and chronic toxicity of most products to fish increased and to daphnia decreased, and acute toxicity to green algae decreased while chronic toxicity increased.