Removal of drug losartan in environmental aquatic matrices by heat-activated persulfate: Kinetics, transformation products and synergistic effects.

Abstract

In this study, the oxidative degradation of losartan (LOS), a widely administered medicine for high blood pressure by heat-activated persulfate was investigated. Increased temperature and persulfate concentration, as well as acidic conditions enhance the degradation efficiency of LOS, whose rate follows pseudo-first order kinetics. From the respective apparent rate constants in the range 40-60\xa0°C, an apparent activation energy of 112.70\xa0kJ/mol was computed. Radical scavenging tests demonstrated that both HO• and [Formula: see text] contribute towards LOS degradation. LOS degradation was suppressed in real water matrices including bottled water (BW) and secondary wastewater effluent (WW), while other experiments indicated that the presence of bicarbonates and humic acid negatively affected its oxidation. Instead, the addition of chloride ions at 250\xa0mg/L resulted in a positive effect on LOS removal. The combination of heat-activated PS with low-frequency ultrasound exhibited a synergistic effect, with the ratio S being 2.29 in BW and 1.52 in WW. Five transformation products of LOS were identified through HRMS suspect and non-target screening approaches, among which two are reported for the first time. Using the in-house risk assessment program, ToxTrAMs was revealed that most of the identified TPs present higher toxicity than LOS against Daphnia magna.