Fotocatálise heterogênea na oxidação de arsênio e sua remoção de águas da região do Quadrilátero Ferrífero - MG

• Autor(a) principal: Mendes, Gisele
• Data de Publicação: 2007
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/2179
• topic: Fotocatálise heterogênea; Águas; Remoção de arsênio; Heterogeneous photocatalysis; Water; Arsenic removal; CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA::QUIMICA ANALITICA

The contamination for Arsenic in waters has been reported in some parts of the world. The element can be found either in organic and inorganic forms. The species of As(III) and As(V) presents higher toxicity and risks to the human health compared to the organic species. Presently, the allowed maximum concentration of As for drinking waters is 10 μg L-1. This study had as objective development of a method and application to removal arsenic of superficial and underground waters, using Advanced Oxidative Process (AOP) for oxidation of the trivalent species and after that adsorption of As(V) in iron hydroxide. As an oxidative process was used a heterogeneous photocatalysis in the internal surface of a photoreactor. As a radiation source was used a mercury vapor light bulb of 125 W. The determination of the As(III) and As(V) concentrations had been monitored by the method of spectrometry of atomic absorption with a hydride generator. The results showed that the best concentration of titanium dioxide for oxidation of a As(III) 1,0 mg L-1 solution was 10% (m/v) in 30 minutes. The pH of work was 7,0 next to the value found in the natural water samples. The oxidation rate of As(III) when used: radiation UV and TiO2, only radiation UV and absence of radiation UV and TiO2, had promoted taxes of oxidation of 90, 78 and 20%, respectively. It was verified that the TiO2 film presented a good resistance and durability, showing that after 12 experiments of 30 minutes during 6 hours, it did not present modification in the oxidation efficiency. The samples, after the oxidative treatment in the photoreactor, had presented concentrations of As(V) nine times bigger than As(III). That is one of the advantages of the oxidative process, because As(V) is 60 times less toxic than As(III). In a subsequent process oxidation, the arsenate was removed of the solution using 50,0 mg L-1 of iron, followed for precipitate formed filtration, what provides superior removals 99%. The processes of oxidation, coagulation and adsorption in iron hydroxides were applied in water samples of mines, pipes, house s tap and a river of the Ouro Preto city, situated in the Quadrilátero Ferrífero, Minas Gerais. After treatments, the Arsenic concentrations had been lower than the detection limit of the technique of Atomic Absorption with the Hydrides Generation, that is 0,2 μg L-1, becoming them proper for the human use.