Mechanism of thermal decomposition of a pesticide for safety concerns: case of Mancozeb.
Thermal decomposition under both air and inert atmospheres of a commercial Mancozeb product was investigated through thermogravimetric analysis and laboratory scale thermal treatment from 20°C to 950°C, with analysis of gaseous and solid products. The aim of this study is the understanding of the thermal degradation mechanisms of a pesticide under different atmospheres and the chemical identification of the solid and gaseous pollutants which can be emitted during warehouse fires and which can constitute a threat for health and environment. Pyrolysis of Mancozeb takes place between 20°C and 950°C and lead essentially to CS(2) and H(2)S emissions with formation at 950°C of MnS and ZnS. Thermal oxidation of Mancozeb under air occurs between 150°C and 950°C with formation of CO, CO(2) and sulphur gases (CS(2) and SO(2)). The first step (155-226°C) is the loss of CS(2) and the formation of ethylene thiourea, ZnS and MnS. The metallic sulphides are oxidized in ZnO and MnSO(4) between 226°C and 650°C (steps 2 and 3). MnSO(4) is then oxidized in Mn(3)O(4) during the last step (step 4) between 650°C and 950°C. At 950°C, carbon recovery is close to 95%. Sulphur recovery is close to 98% with an equal partition between SO(2) and CS(2).
Giroud
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Laboratoire Gestion des Risques et Environnement, 25, rue de Chemnitz, 68200 Mulhouse, France; TREDI, Service Recherche, Technopôle de Nancy-Brabois, 9, avenue de la forêt de Haye, 54505 Vandœuvre-lès-Nancy, France.
Dorge
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Laboratoire Gestion des Risques et Environnement, 25, rue de Chemnitz, 68200 Mulhouse, France. Electronic address: sophie.dorge@uha.fr.
Trouvé
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Laboratoire Gestion des Risques et Environnement, 25, rue de Chemnitz, 68200 Mulhouse, France.
D006358:Hot Temperature; D008344:Maneb / Q000009:adverse effects / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D010575:Pesticides / Q000009:adverse effects / Q000737:chemistry*; D013818:Thermogravimetry; D015038:Zineb / Q000009:adverse effects / Q000737:chemistry*
D010575:Pesticides; D008344:Maneb; C013099:mancozeb; D015038:Zineb