Organophosphorus based compounds are widely used in the agriculture, industry and for the household for insect control.  Of particular concern is the extensive use of Naled (1,2-dibromo-2,2-dichloroethyl dimethyl phosphate) for mosquito control. In response to serious health threats from mosquito harbored Zika, there has been widespread ariel spraying of Naled in highly populated areas.  We have recently found that Naled is more persistent in the environment than initially reported. Therefore, we report herein the ultrasonic degradation of naled from aqueous solution. GC-NPD was used to monitor the disappearance of naled concentration during the ultrasonic irradiation. Our results demonstrate that more than 50% of naled ([naled] &lt;32.6 µM) was degraded within half an hour upon ultrasonic irradiation in oxygen-saturated aqueous solution at 7°C (±1) temperature. The degradation follows pseudo first-order kinetics with rate constants varying from 0.05<sup> </sup>to 0.01 min<sup>-1 </sup>depending on the initial concentrations over the range of 15.2 – 117.8 µM. The rate constant for the degradation decreases with increasing initial naled concentration implying the process may be controlled by partitioning at the gas-liquid interface. This kinetic behavior is consistent with the Langmuir-Hinshelwood model suggesting also oxidation occurs at the gas-liquid interface. Mineralization of naled to chloride, bromide, and phosphate was also monitored by IC over 5 hours of extended irradiation and an excellent mass balance was observed for those chloride and bromide anions. The diester adducts of naled, dimethyl hydrogen phosphate, are the primary intermediates identified by NMR. These results suggest that sonolytic oxidation may be a very potential way for the decontamination of naled from of aqueous solutions.

Ultrasonic degradation of the Zika pesticide naled in aqueous solution: Kinetics and mechanistic investigation

255th National Meeting (2018)

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