Remoção de arsênio por oxidação solar (SORAS)
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Data
2020-07-03
Autores
Bragueto, Rafael Enrico Carvalho
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O arsênio é um elemento que pode estar presente em diversas regiões e em alguns destes locais sua ocorrência pode ser natural, presente em minérios e por atividade geogênica, ou pela ação antropogênica pelo emprego de pesticidas, preservantes de madeira e rejeitos de mineração. Os grandes e médios centros urbanos geralmente contam com um sistema de tratamento de água eficiente, que fornece um produto de qualidade para os habitantes, porém há locais remotos ou com menor infraestrutura, que não dispõem destas tecnologias e podem apresentar águas destinadas ao consumo humano com níveis de arsênio acima do recomendado (10 µg L-1) por diversos órgãos de fiscalização e controle, tais como Organização Mundial de Saúde (OMS), e Conselho Nacional do Meio Ambiente (CONAMA). Diante do problema exposto, faz-se necessário o desenvolvimento de métodos e processos alternativos de tratamento de água que sejam eficientes e acessíveis, de modo a garantir o acesso universal a água de qualidade. Este trabalho teve como objetivo a avaliação e otimização do processo empregando a radiação solar para remoção de arsênio conhecido por SORAS (Remoção de Arsênio por Oxidação Solar) e também de um método alternativo, empregando uma câmara de foto oxidação com lâmpada simulando a radiação solar. Inicialmente, foi realizada a triagem das quatro variáveis envolvidas: concentrações de ferro e de citrato, fonte de citrato e ângulo de incidência solar através de um planejamento fatorial completo 24. O ajuste fino do sistema foi realizado por meio de planejamento Doehlert, sendo que as melhores condições determinadas para remoção de As foram 8 mg L-1 de Fe e 32 mg L-1 de citrato com um ângulo de incidência solar de 90 graus. Sob condições otimizadas, foram realizadas a validação do modelo proposto e a aplicação em amostras reais com o uso de radiações solar e artificial, alcançando-se remoções de 100% em amostras sintéticas e de aproximadamente 79% em amostras reais, após um único período de irradiação. A espectrometria de massas com plasma indutivamente acoplado (ICPMS) mostrou-se eficiente na determinação de arsênio nas amostras avaliadas neste projeto, apresentando boa precisão e exatidão, confirmados pelas análises do material de referência certificado (MRC) NIST1640a.
Arsenic is an element that may be present in several regions and in some of these locations it happens by natural sources, in ores and by geogenic activity, or by anthropogenic activity by the use of pesticides, wood preservatives and mining tailings. The great and medium urban centers generally have an efficient water treatment system, that supplies high quality water to the population, however, there are remote places or those with less infrastructure, that doesn’t possess those technologies, might present drinking water with arsenic levels above the recommended (10 µg L-1) by several fiscalization and control institutions, such as World Health Organization (WHO) and Conselho Nacional do Meio Ambiente (CONAMA). Facing the exposed problem, it is necessary to develop alternative, efficient and accessible water treatment methods, to ensure the universal access to high quality water sources. This study aimed to optimize the arsenic removal method known as SORAS (Solar Oxidation and Removal of Arsenic) and also an alternative method using a photo oxidation chamber with a lamp simulating the solar radiation. Initially, a screening of the four variables were made: iron and citrate concentrations, citrate source and solar radiation incidence angle through complete factorial planning 24. The fine adjustment was performed by Doehlert planning and the best conditions to As removal were 8 mg L-1 of iron and 32 mg L-1 of citrate with solar radiation incidence angle of 90 degrees. Under optimized conditions, the proposed model validation and application in real samples were done, with solar and artificial radiations, achieving 100% removal in synthetic samples and approximately 79% in real samples, after a single irradiation period. The Inductively coupled plasma mass spectrometry (ICP-MS) was efficient in the total arsenic determination in the samples evaluated in this project, showing great precision and accuracy, confirmed by reference certified material (RCM) NIST 1640a analisys.
Arsenic is an element that may be present in several regions and in some of these locations it happens by natural sources, in ores and by geogenic activity, or by anthropogenic activity by the use of pesticides, wood preservatives and mining tailings. The great and medium urban centers generally have an efficient water treatment system, that supplies high quality water to the population, however, there are remote places or those with less infrastructure, that doesn’t possess those technologies, might present drinking water with arsenic levels above the recommended (10 µg L-1) by several fiscalization and control institutions, such as World Health Organization (WHO) and Conselho Nacional do Meio Ambiente (CONAMA). Facing the exposed problem, it is necessary to develop alternative, efficient and accessible water treatment methods, to ensure the universal access to high quality water sources. This study aimed to optimize the arsenic removal method known as SORAS (Solar Oxidation and Removal of Arsenic) and also an alternative method using a photo oxidation chamber with a lamp simulating the solar radiation. Initially, a screening of the four variables were made: iron and citrate concentrations, citrate source and solar radiation incidence angle through complete factorial planning 24. The fine adjustment was performed by Doehlert planning and the best conditions to As removal were 8 mg L-1 of iron and 32 mg L-1 of citrate with solar radiation incidence angle of 90 degrees. Under optimized conditions, the proposed model validation and application in real samples were done, with solar and artificial radiations, achieving 100% removal in synthetic samples and approximately 79% in real samples, after a single irradiation period. The Inductively coupled plasma mass spectrometry (ICP-MS) was efficient in the total arsenic determination in the samples evaluated in this project, showing great precision and accuracy, confirmed by reference certified material (RCM) NIST 1640a analisys.
Descrição
Palavras-chave
Remoção de arsênio, Fotocatálise, Química verde, Planejamento fatorial, ICP-MS, Arsenic removal, Photocatalysis, Green chemistry, Factorial planning