Chlorination of organophosphorus pesticides in natural waters

• Published in: Journal of hazardous materials Vol. 153; no. 1; pp. 320 - 328
• Main Authors: Acero, Juan L., Benítez, F. Javier, Real, Francisco J., González, Manuel
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.05.2008; Elsevier
• Subjects: Applied sciences; Chemical engineering; Chlorfenvinphos - chemistry; Chlorine; Chlorpyrifos - chemistry; Continental surface waters; Diazinon - chemistry; Disinfection; Drinking water and swimming-pool water. Desalination; Drinking water chlorination; Exact sciences and technology; Freshwater; Halogenation; Hydrogen-Ion Concentration; Insecticides - chemistry; Natural water pollution; Organophosphorus pesticides; Oxidation-Reduction; Pollution; Rate constants; Reactors; Temperature; THM formation; Trihalomethanes - chemistry; Water Pollutants, Chemical - chemistry; Water Purification - methods; Water treatment and pollution; Drinking water chlorination; Organophosphorus pesticides; Rate constants; Chlorine; THM formation; Phosphates; Drinking water treatment; Drinking water; Second order; Chlorination; Pesticides; Disinfection; Surface water; pH; Oxidation; Kinetics; Rate constant; Chemical reactivity; Organic compounds
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2007.08.051

Unknown second-order rate constants for the reactions of three organophosphorus pesticides (chlorpyrifos, chlorfenvinfos and diazinon) with chlorine were determined in the present study, and the influence of pH and temperature was established. It was found that an increase in the pH provides a negative effect on the pesticides degradation rates. Apparent second-order rate constants at 20 °C and pH 7 were determined to be 110.9, 0.004 and 191.6 M −1 s −1 for chlorpyrifos, chlorfenvinfos and diazinon, respectively. A higher reactivity of chlorine with the phosphorothioate group (chlorpyrifos and diazinon) than with the phosphate moiety (chlorfenvinfos) could explain these results. Intrinsic rate constant for the elementary reactions of chlorine species with chlorpyrifos and diazinon were also calculated, leading to the conclusion that the reaction between hypochlorous acid and the pesticide is predominant at neutral pH. The elimination of these pesticides in surface waters was also investigated. A chlorine dose of 2.5 mg L -1 was enough to oxidize chlorpyrifos and diazinon almost completely, with a formation of trihalomethanes below the EU standard for drinking water. However, the removal of chlorfenvinfos was not appreciable. Therefore, chlorination is a feasible option for the removal of organophosphorus pesticides with phosphorothioate group during oxidation and disinfection processes, but not for the elimination of pesticides with phosphate moiety.