N, N -diethyl-m-toluamide (DEET) degradation by •OH and SO4•−-assisted AOPs in wastewater treatment: Theoretical studies into mechanisms, kinetics and toxicity

As an emerging pollutant, insect repellent N, N-diethyl-m-toluamide has a certain impact on the water environment. Therefore, mechanism, kinetics and toxicity were studied by quantum chemical calculations, which could help us better understand degradation of DEET initiated by •OH and SO4•−. The calculated rate constants for the •OH and SO4•−-initiated reactions were 1.18 × 109 M−1 s−1 and 2.95 × 109 M−1 s−1 at 298 K and 1 atm, respectively, which were consistent with the corresponding experimental data. It is indicated that the •OH and SO4•− generated from advanced oxidation processes present the same good performance for degradation of DEET in water treatment. The results demonstrated that •OH-initiated DEET degradation was mostly aroused by hydrogen abstraction (65%) and addition (35%). Moreover, SO4•−-initiated DEET degradation mainly proceeded single electron transfer (63%) and addition (37%). The important and initial intermediates could further react with O2, NO and •OH leading to the end products in which had been detected by experimental methods. DEET parallel to the graphene surface performed good adsorption properties. The toxic results showed that DEET degradation was still at harmful level. DEET and its degradation products were also potentially developmental toxicants, which should cause concern in degradation process of DEET.