title: Kinetic modelling of mancozeb hydrolysis and photolysis to ethylenethiourea and other by-products in water.
abstract: The aim of this study was to propose kinetic models suitable for reproducing and predicting mancozeb (Mz) conversion to by-products as a function of the operational conditions. The main factors (pH, temperature and light) potentially affecting the mancozeb degradation in aqueous models were studied by a multifactorial screening design. In addition, the response surface methodology (RSM) was applied to evaluate the interactive effects of these factors on ethylenethiourea (ETU) formation. The response surface revealed that the best degradation conditions to minimize mancozeb conversion to ETU were low pH (2), low temperature (25 °C) and darkness. Under these conditions, the percentage of mancozeb remained in the solution at 72 h was approximately 10% of the initial concentration and the percentage of ETU conversion was 5.4%. However, according to the model, in surface waters under typical environmental conditions (pH 8, 25 °C and light) the percentage of mancozeb conversion to ETU would be about 17.5%. The proposed model provides a satisfactory interpretation of the experimental data obtained during the hydrolysis of mancozeb.
authors.affiliation: Nutrition and Bromatology Group, Analytical and Food Chemistry Department, Science Faculty, University of Vigo, Ourense Campus, E-32004 Ourense, Spain.
authors.forename: Olalla
authors.initials: O
authors.lastname: López-Fernández
authors.affiliation: Department of Chemical Engineering, Science Faculty, University of Vigo, Ourense Campus, E-32004 Ourense, Spain.
authors.forename: Remedios
authors.initials: R
authors.lastname: Yáñez
authors.affiliation: Nutrition and Bromatology Group, Analytical and Food Chemistry Department, Science Faculty, University of Vigo, Ourense Campus, E-32004 Ourense, Spain. Electronic address: raquelrial@uvigo.es.
authors.forename: Raquel
authors.initials: R
authors.lastname: Rial-Otero
authors.affiliation: Nutrition and Bromatology Group, Analytical and Food Chemistry Department, Science Faculty, University of Vigo, Ourense Campus, E-32004 Ourense, Spain. Electronic address: jsimal@uvigo.es.
authors.forename: Jesús
authors.initials: J
authors.lastname: Simal-Gándara
mesh_terms: D005031:Ethylenethiourea; D005659:Fungicides, Industrial; D006868:Hydrolysis; D010782:Photolysis; D014867:Water
chemical_list: D005659:Fungicides, Industrial; D014867:Water; D005031:Ethylenethiourea
keywords: Aqueous solution; Ethylenethiourea; Kinetic study; Mancozeb degradation; Modelling