Phosphate enhanced thermal activation of peroxymonosulfate for acyclovir removal: Process comparison and DFT calculation

In this study, phosphate/thermal activated peroxymonosulfate (PMS) process were applied to degrade the antiviral drug acyclovir (ACV) in water. Both Na 2 HPO 4 and Na 5 P 3 O 10 could effectively enhance ACV removal by thermally activated PMS process and the enhancement of Na 2 HPO 4 was more significant. High reaction temperature favored ACV removal and the best removal can be achieved at a certain PMS dosage in both processes. With increasing Na 2 HPO 4 dosage, the ACV removal first increased and then decreased, while increasing Na 5 P 3 O 10 dosage caused the enhancement of the degradation. The ACV degradation by Na 2 HPO 4 /thermal/PMS system was easily affected by initial solution pH, while Na 5 P 3 O 10 /thermal/PMS system operated in a wider pH range. The addition of Cl - and NO 3 - exerted insignificant effect in Na 2 HPO 4 /thermal/PMS process, while posed complicated impact by Na 5 P 3 O 10 /thermal/PMS process. The presence of HA significantly retarded ACV degradation by Na 2 HPO 4 /thermal/PMS system, while in Na 5 P 3 O 10 /thermal/PMS system, high HA concentration accelerated the degradation. In Na 2 HPO 4 /thermal/PMS system, SO 4 •- and •OH were identified as the main active species. Whereas, the ACV degradation was relied on non-free radicals ( 1 O 2 ) in Na 5 P 3 O 10 /thermal/PMS process. The strengthening effect of Na 2 HPO 4 was reflected in its ability to reduce the reaction energy barrier required for O-O bond cleavage in PMS molecules, while Na 5 P 3 O 10 provided an alkaline condition for the self-decomposition of PMS. 10 and 11 intermediate products were detected in Na 2 HPO 4 /thermal/PMS and Na 5 P 3 O 10 /thermal/PMS systems, respectively. Both processes produced intermediates with higher toxicity than ACV according to software analysis.