title: Kinetic studies of the reaction between pesticides and hydroxyl radical generated by laser flash photolysis.
abstract: BACKGROUND
  Due to contamination of the environment by pesticides and their mishandling, there is the need for treatment of contaminated sites and correct disposal of materials containing them. Thus, studies with advanced oxidation processes are expanding and can determine the rate constant of the hydroxyl radical with organic compounds of great importance in environmental contamination. In this context, the use of laser flash photolysis has been shown to be viable for the determination of these constants.
  
  
  RESULTS
  The reaction rate constants of different pesticides with HO(•) in degassed acetonitrile have been determined. They were 1.6 × 10(9)  M(-1)  s(-1), 0.6 × 10(9)  M(-1)  s(-1), 1.2 × 10(9)  M(-1)  s(-1), 2.4 × 10(9)  M(-1)  s(-1) and 2.2 × 10(9)  M(-1)  s(-1) for the pesticides carbaryl, propoxur, fenoxycarb, ethoxysulfuron and chlorimuron-ethyl, respectively. These values are about an order of magnitude smaller than the diffusion controlled rate and correlate with the relative rates of disappearance of the pesticides in the photo-Fenton reaction in water.
  
  
  CONCLUSIONS
  The correlation of the relative rate constants determined by laser flash photolysis with the relative rates of photo-Fenton degradation of the pesticides is compelling evidence for the participation of the hydroxyl radical in the degradation of these pesticides in the latter system.
authors.affiliation: Institute of Chemistry, Federal University of Mato Grosso do Sul, Av. Senador Filinto Muller 1555, CP 549, Campo Grande, MS, 79074-460, Brazil.
authors.forename: Fábio
authors.initials: F
authors.lastname: Gozzi
authors.affiliation: Institute of Chemistry, Federal University of Mato Grosso do Sul, Av. Senador Filinto Muller 1555, CP 549, Campo Grande, MS, 79074-460, Brazil.
authors.forename: Silvio C
authors.initials: SC
authors.lastname: Oliveira
authors.affiliation: School of Technology, University of Campinas UNICAMP, Paschoal Marmo 188, 13484-332, Limeira, SP, Brazil.
authors.forename: Renato F
authors.initials: RF
authors.lastname: Dantas
authors.affiliation: Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes 748, CP 26077, São Paulo, SP, 05513-970, Brazil.
authors.forename: Volnir O
authors.initials: VO
authors.lastname: Silva
authors.affiliation: Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes 748, CP 26077, São Paulo, SP, 05513-970, Brazil.
authors.forename: Frank H
authors.initials: FH
authors.lastname: Quina
authors.affiliation: Institute of Chemistry, Federal University of Mato Grosso do Sul, Av. Senador Filinto Muller 1555, CP 549, Campo Grande, MS, 79074-460, Brazil.
authors.forename: Amilcar
authors.initials: A
authors.lastname: Machulek
mesh_terms: D017665:Hydroxyl Radical / Q000737:chemistry*; D007700:Kinetics; D007834:Lasers; D015394:Molecular Structure; D010575:Pesticides / Q000737:chemistry*; D010782:Photolysis
chemical_list: D010575:Pesticides; D017665:Hydroxyl Radical
keywords: advanced oxidation processes; hydroxyl radical; kinetics; laser flash photolysis; pesticides; photo-Fenton