Eletrodos de nanotubos de TiO2 modificados com B e Sb2S3 e desenvolvimento de novos métodos de tratamento para corantes e efluente de tintura de cabelo usando fotoeletrocatálise e combinação com ozonização
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Data
2017-02-17
Autores
Bessegato, Guilherme Garcia [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O esforço de tratar efluentes e águas superficiais contaminados por corantes tem sido intenso e uma das alternativas de interesse é a fotoeletrocatálise (FEC), baseada no uso de processos capazes de gerar radicais •OH, com grande potencial oxidante. O presente trabalho investiga a preparação, caracterização e aplicação de nanotubos de TiO2 (TiO2NTs) dopados com boro e modificados com Sb2S3 como ânodos no tratamento fotoeletrocatalítico de corantes de cabelo do tipo temporário. Tais modificações podem contornar limitações de filmes de óxido de titânio convencionais. Os eletrodos de nanotubos de TiO2 foram preparados por meio de anodização eletroquímica de placas de titânio metálico em eletrólitos contendo íon fluoreto. A deposição de nanopartículas de Sb2S3 foi realizada por meio da técnica de deposição por banho químico e a dopagem com boro por meio da adição de um precursor no eletrólito de anodização. Tais eletrodos foram caracterizados e aplicados na degradação fotoeletrocatalítica dos corantes Básico Vermelho 51 (BV51), Básico Azul 99 (BA99) e Ácido Amarelo 1 (AA1), escolhidos como modelos de corantes de cabelo para tal tratamento. Ambos os eletrodos mostraram eficiência de degradação significativamente superior à obtida para eletrodos não modificados, além de fotoativação na região do visível. Para contornar a limitação da FEC, que é a baixa eficiência em soluções altamente coloridas, foi investigada a combinação da FEC com ozonização no intuito de melhorar a eficiência de tratamento do corante AA1 em maior concentração e no tratamento de efluentes resultantes de tintura de cabelo. O método combinado foi o mais eficiente dentre os testados e a simples aplicação de uma voltagem (O3+FEC) aumenta consideravelmente a taxa de descoloração (2×), diminui o tempo necessário para mineralização e o consumo de ‘energia elétrica por ordem’, em comparação com um sistema de ozonização+fotocatálise. Por fim, investigou-se as características de um efluente de tintura de cabelo e aplicou-se o método combinado para seu tratamento. Esses efluentes apresentaram alto conteúdo de carbono orgânico e demanda química de oxigênio, cor intensa e alta turbidez, presença dos precursores p-fenilenodiamina e resorcinol, usados em tinturas permanentes, bem como a ocorrência da base de Bandrowski, subproduto mutagênico indesejável. Diferentes combinações de POAs foram aplicadas no tratamento desse efluente: ozonização (O3), ozônio/UV-C (O3/UV), ozônio/fotoeletrocatálise (O3/FEC), O3/UV-C/H2O2 e O3/FEC/H2O2. O sistema O3/FEC/H2O2 apresentou o menor consumo energético e a maior taxa de mineralização, podendo degradar completamente p-fenilenodiamina, resorcinol e base de Bandrowski em menos de 5 min de tratamento. Considerando o amplo uso de corantes capilares, uma grande quantidade de contaminantes pode chegar a águas superficiais ou estações de esgoto, portanto nossos resultados são um passo importante na avaliação de um método eficiente e simples para o tratamento de águas residuárias complexas.
Intense effort has been devoted to the treatment of effluents and surface water contaminated by dyes, and one of the alternatives of interest is the photoelectrocatalysis (PEC), based on the use of processes capable of generating •OH radicals, with great oxidizing potential. The present work investigates the preparation, characterization and application of TiO2 nanotubes (TiO2NTs), doped with boron and modified with Sb2S3, as anodes in the photoelectrocatalytic treatment of hair dyes of the temporary type. Such modifications could circumvent limitations of conventional TiO2 oxide films. The TiO2 nanotubes electrodes were prepared by electrochemical anodization of metallic titanium plates in fluoride-containing electrolytes. The deposition of nanoparticles of Sb2S3 was carried out by chemical bath deposition technique and the doping with boron was done by the addition of a boron precursor in the anodizing electrolyte. These electrodes were characterized and applied in the photoelectrocatalytic degradation of Basic Red 51 (BV51), Basic Blue 99 (BA99) and Acid Yellow 1 (AA1) dyes, chosen as models of hair dyes for treatment. Both electrodes promoted degradation efficiency significantly higher than that obtained for unmodified electrodes, in addition to the photoactivation in the visible region. To circumvent PEC limitation, which is the low efficiency in highly colored solutions, the combination of PEC technique with ozonation was investigated in order to improve the treatment efficiency of the AA1 dye in higher concentration and in the treatment of effluents resulting from hair dyeing. The combined method was the most efficient among those tested and the simple application of a voltage (O3 + FEC) greatly increases the decolorization rate (2×), decreases the time required for mineralization and the consumption of 'electric energy per order' compared to an ozonation + photocatalysis system. Finally, it was investigated the properties of a hair dye effluent and applied the combined method for its treatment. These effluents presented high organic carbon and chemical oxygen demand contents, intense color and high turbidity, in addition to the presence of the precursors p-phenylenediamine and resorcinol, used in permanent dyes, as well as the occurrence of Bandrowski base, an undesirable mutagenic byproduct. Different combinations of AOPs were applied in the treatment of this effluent: ozonation (O3), ozone/UV-C (O3/UV-C), ozone/photoelectrocatalysis (O3/PEC), O3/UV-C/H2O2 and O3/PEC/H2O2. The O3/PEC/H2O2 system presented the lowest energy consumption and the highest mineralization rate, which could completely degrade p-phenylenediamine, resorcinol and Bandrowski’s base in less than 5 min of treatment. Considering the great use of hair dyes, a large amount of contaminants can reach surface waters or sewage stations, therefore our results are an important step in the evaluation of an efficient and simple method for treatment of complex wastewater.
Intense effort has been devoted to the treatment of effluents and surface water contaminated by dyes, and one of the alternatives of interest is the photoelectrocatalysis (PEC), based on the use of processes capable of generating •OH radicals, with great oxidizing potential. The present work investigates the preparation, characterization and application of TiO2 nanotubes (TiO2NTs), doped with boron and modified with Sb2S3, as anodes in the photoelectrocatalytic treatment of hair dyes of the temporary type. Such modifications could circumvent limitations of conventional TiO2 oxide films. The TiO2 nanotubes electrodes were prepared by electrochemical anodization of metallic titanium plates in fluoride-containing electrolytes. The deposition of nanoparticles of Sb2S3 was carried out by chemical bath deposition technique and the doping with boron was done by the addition of a boron precursor in the anodizing electrolyte. These electrodes were characterized and applied in the photoelectrocatalytic degradation of Basic Red 51 (BV51), Basic Blue 99 (BA99) and Acid Yellow 1 (AA1) dyes, chosen as models of hair dyes for treatment. Both electrodes promoted degradation efficiency significantly higher than that obtained for unmodified electrodes, in addition to the photoactivation in the visible region. To circumvent PEC limitation, which is the low efficiency in highly colored solutions, the combination of PEC technique with ozonation was investigated in order to improve the treatment efficiency of the AA1 dye in higher concentration and in the treatment of effluents resulting from hair dyeing. The combined method was the most efficient among those tested and the simple application of a voltage (O3 + FEC) greatly increases the decolorization rate (2×), decreases the time required for mineralization and the consumption of 'electric energy per order' compared to an ozonation + photocatalysis system. Finally, it was investigated the properties of a hair dye effluent and applied the combined method for its treatment. These effluents presented high organic carbon and chemical oxygen demand contents, intense color and high turbidity, in addition to the presence of the precursors p-phenylenediamine and resorcinol, used in permanent dyes, as well as the occurrence of Bandrowski base, an undesirable mutagenic byproduct. Different combinations of AOPs were applied in the treatment of this effluent: ozonation (O3), ozone/UV-C (O3/UV-C), ozone/photoelectrocatalysis (O3/PEC), O3/UV-C/H2O2 and O3/PEC/H2O2. The O3/PEC/H2O2 system presented the lowest energy consumption and the highest mineralization rate, which could completely degrade p-phenylenediamine, resorcinol and Bandrowski’s base in less than 5 min of treatment. Considering the great use of hair dyes, a large amount of contaminants can reach surface waters or sewage stations, therefore our results are an important step in the evaluation of an efficient and simple method for treatment of complex wastewater.
Descrição
Palavras-chave
Fotoeletrocatálise, Nanotubos de TiO2 modificados com Sb2S3, TiO2 dopado com boro, Degradação de corantes de cabelo, Ozonização, Photoelectrocatalysis, TiO2 nanotubes modified with Sb2S3, Boron-doped TiO2, Degradation of hair dyes, Ozonation