Scale up da produção de óxidos nanoestruturados crescidos em liga Ti-W e sua aplicação na degradação fotoeletrocatalítica do fungicida carbendazim em um reator de fluxo
Data
2023-06-14
Autores
Carvalho, Joyce Ferreira de 
Orientadores
Rodrigues, Christiane de Arruda
Tipo
Tese de doutorado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
O carbendazim (CBZ) compõe o grupo dos poluentes emergentes e possui alta potencialidade para causar danos ao ambiente e à saúde humana devido à sua toxicidade, recalcitrância e resistência à degradação por processos convencionais de tratamento de águas residuais. Diante da toxicidade deste fungicida e o bom desempenho do processo fotoeletrocatalítico no tratamento de poluentes emergentes, em escala de bancada, o presente trabalho visa avaliar o emprego de óxidos nanotubulares crescidos em ligas de Ti-W em um reator de fluxo fotoeletrocatalítico, em escala piloto, na degradação do CBZ. As ligas foram preparadas em forno arco voltaico com diferentes composições de tungstênio (0,5, 2,5 e 5,0 m/m % em peso) e, em seguida, passaram por laminação para a extensão da área superficial (52,8 cm2). Placas de titânio foram cortadas nas mesmas dimensões para fins de comparação. Placas de titânio e ligas Ti-W foram anodizadas para a obtenção de diferentes espessuras da camada de óxido nanotubular (1, 2, 4 e 6 µm) que, na sequência, foram calcinadas em condições otimizadas e submetidas à estudos de caracterização morfológica, estrutural e óptica e de fotoatividade eletroquímica. O eletrodo de TiO2 com 4 µm de espessura, anodizado a 20 V por 24 h em uma solução eletrolítica de 0,2 mol L-1 HF, 7 % H2O em etilenoglicol, apresentou maior fotoatividade eletroquímica, sendo usado nos estudos de degradação. Para o mesmo propósito, foram selecionadas as ligas de Ti-0,5W, Ti-2,5W e Ti-5,0W com 6 µm de espessura, as quais foram anodizadas em 120, 120 e 140 V por 55, 60, 50 min, respectivamente, em uma solução eletrolítica de 0,2 mol L-1 HF, 5 % H2O em etilenoglicol, devido às maiores fotocorrentes. Houve o crescimento de nanotubos com alta ordenação por toda a extensão dos eletrodos preparados. Esses eletrodos foram inseridos em um reator de fluxo tubular com a finalidade de avaliar a eficiência dos diferentes eletrodos nos processos fotocatalíticos (FTC) e fotoeletrocatalíticos (FEC) na degradação do CBZ. A vazão foi otimizada em 30 L h-1 sob regime de escoamento predominantemente laminar. Um meio reacional com água e acetonitrila (20:80% v/v) foi usado para permitir a efetividade dos eletrodos hidrofílicos estudados na degradação do composto hidrofóbico (CBZ). O processo FEC empregando nanotubos crescido sobre a liga Ti-5,0W alcançou o maior desempenho na degradação do CBZ, com 78 % de remoção do contaminante em 60 minutos de tratamento, devido à menor taxa de recombinação das cargas fotogeradas em relação aos demais eletrodos, por fim, apresentando menor gasto energético (8,60 KWh m-3 ordem -1).
Carbendazim (CBZ) is an emerging pollutant, that has a high potential to cause damage to the environment and human health due to its toxicity, recalcitrance and resistance to degradation by conventional wastewater treatment processes. Thus, the present work aims to evaluate the photoelectrocatalytic performance of nanotubular oxides grown in Ti-W alloys, which were placed in a pilot-scale flow reactor for degradation of CBZ. The alloys were prepared in an electric arc furnace with different tungsten compositions (0.5, 2.5 and 5.0 at% W) and then passed through a rolling mill to extend the surface area (52.8 cm2). Titanium plates were cut to the same dimensions for comparison purposes. Titanium plates and Ti-W alloys were anodized in different thicknesses of the nanotubular oxide layer (1, 2, 4 and 6 µm), calcined under optimized conditions and then submitted to morphological, structural and optical characterization studies and electrochemical photoactivity assessment. The 4 µm thick TiO2 electrode was selected for degradative studies due to its higher electrochemical photoactivity. This electrode was anodized at 20 V for 24 h in an electrolytic solution of 0.2 M HF, 7 % H2O in ethylene glycol. For the same purpose, alloys of Ti-0.5W, Ti-2.5W and Ti-5.0W with 6 µm thickness were anodized at 120, 120 and 140 V for 55, 60, 50 min in an electrolyte solution of 0.2 M HF, 5% H2O in ethylene glycol. Uniform and highly ordered nanotubes grow along the electrodes. These electrodes were inserted into a tubular flow reactor with the purpose of evaluating the efficiency of the different electrodes in the photocatalytic (PC) and photoelectrocatalytic (PEC) processes in the degradation of CBZ. The flow rate was optimized at 30 L h-1 under a predominantly laminar flow regime. A reaction medium with water and acetonitrile (20:80 vol. %) was used to allow the effectiveness of the hydrophilic electrodes in the degradation of the hydrophobic compound (CBZ). The PEC-NT/Ti-5.0W process showed the highest performance in the degradation of CBZ, reaching 78 % of contaminant removal in 60 minutes of reaction due to the lower recombination rate of the photogenerated charges caused by the greater presence of the TiO2-WO3 heterojunction and surface states, presenting lower energy consumption (8.60 KWh m-3 order-1).
Carbendazim (CBZ) is an emerging pollutant, that has a high potential to cause damage to the environment and human health due to its toxicity, recalcitrance and resistance to degradation by conventional wastewater treatment processes. Thus, the present work aims to evaluate the photoelectrocatalytic performance of nanotubular oxides grown in Ti-W alloys, which were placed in a pilot-scale flow reactor for degradation of CBZ. The alloys were prepared in an electric arc furnace with different tungsten compositions (0.5, 2.5 and 5.0 at% W) and then passed through a rolling mill to extend the surface area (52.8 cm2). Titanium plates were cut to the same dimensions for comparison purposes. Titanium plates and Ti-W alloys were anodized in different thicknesses of the nanotubular oxide layer (1, 2, 4 and 6 µm), calcined under optimized conditions and then submitted to morphological, structural and optical characterization studies and electrochemical photoactivity assessment. The 4 µm thick TiO2 electrode was selected for degradative studies due to its higher electrochemical photoactivity. This electrode was anodized at 20 V for 24 h in an electrolytic solution of 0.2 M HF, 7 % H2O in ethylene glycol. For the same purpose, alloys of Ti-0.5W, Ti-2.5W and Ti-5.0W with 6 µm thickness were anodized at 120, 120 and 140 V for 55, 60, 50 min in an electrolyte solution of 0.2 M HF, 5% H2O in ethylene glycol. Uniform and highly ordered nanotubes grow along the electrodes. These electrodes were inserted into a tubular flow reactor with the purpose of evaluating the efficiency of the different electrodes in the photocatalytic (PC) and photoelectrocatalytic (PEC) processes in the degradation of CBZ. The flow rate was optimized at 30 L h-1 under a predominantly laminar flow regime. A reaction medium with water and acetonitrile (20:80 vol. %) was used to allow the effectiveness of the hydrophilic electrodes in the degradation of the hydrophobic compound (CBZ). The PEC-NT/Ti-5.0W process showed the highest performance in the degradation of CBZ, reaching 78 % of contaminant removal in 60 minutes of reaction due to the lower recombination rate of the photogenerated charges caused by the greater presence of the TiO2-WO3 heterojunction and surface states, presenting lower energy consumption (8.60 KWh m-3 order-1).