Descontaminação de água tratada contendo parationa-metílica pelo emprego de radiação UV, ozônio e processo oxidativo avançado

• Ano de defesa: 2013
• Autor(a) principal: Pimenta, Gustavo Gonçalves
• Orientador(a): Queiroz, Maria Eliana Lopes Ribeiro de
• Banca de defesa: Faroni, Lêda Rita D'antonino , Silva, Deusanilde de Jesus
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Mestrado em Agroquímica
• Departamento: Agroquímica analítica; Agroquímica inorgânica e Físico-química; Agroquímica orgânica
• País: BR
• Palavras-chave em Português: Extração; Parationa-metílica; Descontaminação de água
• Palavras-chave em Inglês: Extraction; Parathion-methyl; Water decontamination
• Área do conhecimento CNPq: CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA::QUIMICA ANALITICA
• Link de acesso: http://locus.ufv.br/handle/123456789/2148

The organophosphorus pesticide methyl parathion is an insecticide and acaricide largely effective against wide range of pest, furthermore it represents an advance over the organochlorine pesticides because of their low persistence. On the other hand, residues of this pesticide on the environment can be associated to several risks to human health, like carcinogenicity, neurotoxicity and endocrine disruption. Over the last years, chemical oxidation processes like photodecomposition, ozonation and advanced oxidative processes (AOPs) have been used successfully for degradation of several organic pollutants. The main aim of this work was evaluate the degradation of the methyl parathion pesticide in distillated and drinking water using UV radiation, ozone and the combination of them, characterizing an AOP. To monitoring the pesticide residues after submission to degradative processes, the microextraction liquid-liquid dispersive technique based in low density extractor solvent (LDS-DLLME) and analysis for gas chromatograph coupled with electron capture detector (CG-ECD) was optimized and validated. The results showed that the LDS-DLLME was very efficient to methyl parathion extraction, presenting high extraction recovery (101.1%) and high enrichment factor (57.3). Besides of selectivity, linearity, accuracy, the validated analysis method showed low detection and quantification limits, 83 ng L-1 and 250 ng L-1, respectively. The methyl parathion photodecomposition to UV254nm at pH 3 and 35 ºC achieved 100% after 120 min of process exposition. The ozonation at pH 11 and 15 ºC also proved to be efficient, once it has reached 99% removal of the pesticide residue after 60 min of experiment. The combined system UV/O3 at pH 3 and 35 ºC, presented itself as the most efficient process of chemical oxidation studied, since with only 30 min of procedure, was removed 100% of the pesticide. The degradation by the AOP UV/O3 followed a pseudo-first order reaction providing the highest kinetic rate (kT = 0.1855 min-1), the highest quantum yield (F254nm = 7.79 x 10-5 mol Einstein-1) and consequently, the shorter half-life (t1/2 = 3.74 min) between the processes evaluated. All degradative processes were strongly influenced by pH and temperature. The application of the optimized oxidation processes in distilled and drinking water provided methyl parathion residues, when still existing, below of the maximum allowed value in Brazilian territory that is 9.0 mg L-1.