Desenvolvimento de reação e calibração de amostradores passivos e ativos para identificação de H2S em ar

• Autor(a) principal: Catai, Marcus Augusto dos Santos
• Data de Publicação: 2021
• Tipo de documento: Trabalho de conclusão de curso
• Idioma: por
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://hdl.handle.net/11449/214095
• topic: Indoor; H2S; Amostrador passivo; Amostrador ativo

H2S is a toxic, corrosive gas and an unpleasant odor. According to Security US Occupational and Healthy Administration (OSHA), the exposure limit allowable (for 8 hours) is 10 ppm. Concentrations of 20 ppm are the limit for basic health problems. In work environments, human exposure to H2S can occur during oil extraction and by workers inside underground galleries of cities. The prior determination of H2S is important from the point of view of hygiene occupational. An interesting procedure, to do this simply, using portable, low-cost and easy-to-handle equipment is the use of passive samplers and assets. First, a passive sampler was mounted with the collecting surface (filter of cellulose) impregnated with basic suspension of zinc hydroxide. H2S is collected in the form of zinc sulfide on the cellulose filter. The filter surface is further treated with acidic solution of N,N-dimethyl-p-phenyldiamine (N-N) and ferric chloride. The product of this reaction is a blue colored compound and is known by the trade name of methylene blue. The intensity of color formed is proportional to the average concentration of analyte (H2S) present during the sampling period. The determination of H2S can be done directly by visual comparison or even by digitizing the image obtained. In this case you can use a simple camera built in mobile phone and use of Digital Image-Based software (DIB). As an advantage of the method, it does not require the energy source and the chemical reaction carried out in the filter Sampled can be done at the sampling site. The concentration of H2S can be known immediately, in situ, at the end of the sampling period. Subsequently, the construction of an active-sampler for the determination of H2S was carried out with direct reading of the analytical signal on a reagent-impregnated cellulose filter fluorescent and through the contact between the gas and the compound the fluorescence of the internal filter and thus it is possible to quantify the amount of hydrogen sulphide in the environment. Both techniques are transparent but the collecting surface is impregnated with the reagent it must be highly homogeneous and difficulties are encountered to obtain such in a period small sampling time.