Estudo comparativo de remoção de Cr(VI) em solução por vermiculita tratada com Fe(II) e sais de Fe(II)
Data
2019-10-25
Autores
Boga, Gabriella de Andrade [UNIFESP]
Orientadores
Shinzato, Mirian Chieko [UNIFESP]
Tipo
Trabalho de conclusão de curso de graduação
Título da Revista
ISSN da Revista
Título de Volume
Resumo
O aumento das atividades industriais e o mal gerenciamento de seus efluentes e resíduos vem provocando a contaminação de solos e águas em muitas localidades do país. Dentre os contaminantes, destacam-se os metais pesados, como o cromo (Cr), que em sua forma hexavalente é extremamente tóxico ao homem. Diante dessa problemática o presente estudo teve como objetivo avaliar dois métodos de remoção do Cr(Vl): 1) uso o mineral de vermiculita contendo ferro(II) e 2) aplicação de sal de Fe(II) seguido de vermiculita natural. No primeiro caso pretende-se reduzir e reter o Cr na estrutura da vermiculita numa única etapa de trabalho e, no outro, espera-se primeiro reduzir o Cr(VI) à sua forma trivalente e em seguida utilizar a vermiculita natural para reter o cromo na sua estrutura. As amostras de vermiculita pré-tratadas (V-Fe) foram utilizadas nos testes de remoção de Cr(VI) em solução em sistema batelada a fim de analisar as melhores condições (tempo, pH e concentração) para remover o íon pelos dois métodos estudados. Os resultados indicaram que V-Fe conseguiu remover 100% de Cr(VI) de soluções com concentrações entre 5 mg L-1 e 100 mg L-1 de Cr(VI) em apenas 1h e em todos os pH testados (2 a 10). A análise da solução final dos testes realizados com V-Fe indicou presença de cerca de 50% de Cr(III), revelando que além de todo Cr(VI) ter sido reduzido, essa amostra conseguiu reter cerca de 50% desse íon e ainda manter grande parte de Fe(II) em sua estrutura. Quando comparados com os dos testes utilizando sal de Fe(II), verificou-se que todo ferro é imediatamente oxidado, inclusive o seu excedente gerando um precipitado e dando à solução forte coloração amarelada. Logo, foi possível verificar que a principal vantagem da incorporação de Fe(II) na vermiculita se dá pelo fato da estrutura do mineral conseguir manter o ferro na forma reduzida mesmo após seu uso na remoção de Cr(VI) e gerar menos óxidos de ferro como precipitados. Quanto ao Cr(III) que permaneceu na solução a sua remoção pode ser realizado utilizando apenas a vermiculita natural que possui elevada afinidade por esse cátion. Portanto o uso alternativo de vermiculita no tratamento e remoção de efluentes contendo Cr(VI) pode ser bastante vantajoso, por se um mineral abundante no Brasil e de amplo uso comercial.
The increase of the industrial activities and the lack of their wastes management have caused soil and water contamination in many brazilian areas. Among the contaminants, heavy metals as chromium(VI) stands out for its toxicity. Therefore, the present study aimed to evaluate two methods of Cr(Vl) removal process: 1) using vermiculite impregnated with iron(II), and 2) by the directly addition of a salt of Fe(II) and natural vermiculite. In the first case it is intended to reduce and retain Cr(III) in the vermiculite structure - just in a single work step; and in the other method, it is firstly expected to reduce Cr(VI) to Cr(III) and then, add natural vermiculite to retain Cr(III) ions. Samples of vermiculite with Fe(II) (V-Fe) and salt of Fe (FeSO4) were used in Cr(VI) removal batch tests using sinthetic solutions to analyze the best conditions of time, pH and concentration. V-Fe was able to remove 100% Cr(VI) from solutions with concentrations between 5 mg L-1 and 100 mg L-1 Cr(VI) in 1h and at all values of pH (2 to 10 ). Analysis of the final solution of the tests performed with V-Fe indicated the presence of about 50% of Cr(III), revealing that in addition to all Cr(VI) being reduced, this sample was able to retain about 50% of this ion in its structure. When compared to the tests using Fe(II) salt, it was found that all iron is immediately oxidized, including its excess, generating a precipitate and giving to the solution a strong yellowish color. Thus, it was possible to verify that the main advantage of the incorporation of Fe(II) in vermiculite is that the mineral structure can keep iron in reduced form, even after its use in Cr (VI) removal and also generate less iron oxides as precipitates. The removal of the Cr(III) ions remained in the solution can be performed using only natural vermiculite, that has high affinity for this cation. Therefore the alternative use of vermiculite in the treatment and removal of effluents containing Cr(VI) can be very advantageous, since it is an abundant mineral in Brazil and of wide commercial use.
The increase of the industrial activities and the lack of their wastes management have caused soil and water contamination in many brazilian areas. Among the contaminants, heavy metals as chromium(VI) stands out for its toxicity. Therefore, the present study aimed to evaluate two methods of Cr(Vl) removal process: 1) using vermiculite impregnated with iron(II), and 2) by the directly addition of a salt of Fe(II) and natural vermiculite. In the first case it is intended to reduce and retain Cr(III) in the vermiculite structure - just in a single work step; and in the other method, it is firstly expected to reduce Cr(VI) to Cr(III) and then, add natural vermiculite to retain Cr(III) ions. Samples of vermiculite with Fe(II) (V-Fe) and salt of Fe (FeSO4) were used in Cr(VI) removal batch tests using sinthetic solutions to analyze the best conditions of time, pH and concentration. V-Fe was able to remove 100% Cr(VI) from solutions with concentrations between 5 mg L-1 and 100 mg L-1 Cr(VI) in 1h and at all values of pH (2 to 10 ). Analysis of the final solution of the tests performed with V-Fe indicated the presence of about 50% of Cr(III), revealing that in addition to all Cr(VI) being reduced, this sample was able to retain about 50% of this ion in its structure. When compared to the tests using Fe(II) salt, it was found that all iron is immediately oxidized, including its excess, generating a precipitate and giving to the solution a strong yellowish color. Thus, it was possible to verify that the main advantage of the incorporation of Fe(II) in vermiculite is that the mineral structure can keep iron in reduced form, even after its use in Cr (VI) removal and also generate less iron oxides as precipitates. The removal of the Cr(III) ions remained in the solution can be performed using only natural vermiculite, that has high affinity for this cation. Therefore the alternative use of vermiculite in the treatment and removal of effluents containing Cr(VI) can be very advantageous, since it is an abundant mineral in Brazil and of wide commercial use.