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 center dot OH and SO4 center dot-. The calculated rate constants for the .OH and 80'C-initiated reactions were 1.18 x 10(9) M-1 s(-1) and 2.95 x 10(9 )M(-1) s(-1) at 298 K and 1 atm, respectively, which were consistent with the corresponding experimental data. It is indicated that the center dot OH and SO4 center dot- generated from advanced oxidation processes present the same good performance for degradation of DEET in water treatment. The results demonstrated that center dot OH-initiated DEET degradation was mostly aroused by hydrogen abstraction (65%) and addition (35%). Moreover, SO4 center dot--initiated DEET degradation mainly proceeded single electron transfer (63%) and addition (37%). The important and initial intermediates could further react with O-2, NO and center dot 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.

Automated summary

This study investigated the mechanism, kinetics, and toxicity of insect repellent DEET in water environment using quantum chemical calculations. The results showed that the degradation of DEET initiated by •OH and SO4• from advanced oxidation processes had good performance. The degradation of DEET was mainly caused by hydrogen abstraction and addition.