Degradation of triclosan and 2,8-dichlorodibenzene-p-dioxin by Fe/Nb2O5/UV system

This study describes the experimental design and optimization of the photocatalytic reaction using catalyst Fe/Nb2O5 immobilized on anginate beads in the degradation of Triclosan and 2.8-dichlorodibenzene-p-dioxin. The techniques employed to characterize the photocatalysts were: Specific surface area, Average pore volume, and average pore diameter, photo-acoustic spectroscopy (PAS), X-ray diffraction (XRD), scanning electron microscopy (SEM/EDS), Fourier transform infrared spectroscopy (FTIR) and zero charge point. The reaction parameters studied were: pH, Catalyst concentration, Catalyst calcination temperature, nominal metallic charge. The results indicated that the immobilized Fe/Nb2O5 catalysts were efficient in the degradation of Triclosan and 2.8-dichlorodibenzene-p-dioxin. The catalysts with nominal metal loading of 1.5% Fe calcined at 873 K showed the highest constant reaction rate and the lowest half-life, 0.069 min-1 and 10.04 min. Tests in different matrices indicated that the photocatalytic reaction using aqueous solution with content Cl- is faster than when compared with the utlrapura water matrix. The 2.8-DCDD generation and its subsequent degradation was carried out in approximately 80 min of reaction. The results presented by the reactions in continuous system were better or equivalent to those presented by the batch system. The parameters studied (wt% Fe and calcination temperature) in Experimental design and optimization were significant for the process.Universidade Tecnológica Federal do Paraná (UTFPR)Este estudo descreve o planejamento experimental e a otimização da reação fotocatalítica utilizando o catalisador Fe/Nb2O5 imobilizado em esferas de alginato na degradação do Triclosan e da 2,8-diclorodibenzeno-p-dioxina. As técnicas empregadas para caracterizar os fotocatalisadores foram: área superficial específica, volume médio dos poros e diâmetro médio dos poros, espectroscopia fotoacústica (PAS), difração de raios-X (DRX), microscopia eletrônica de varredura (MEV/EDS), espectroscopia no infravermelho com transformada de Fourier (FTIR) e ponto de carga zero. Os parâmetros de reação estudados foram: pH, concentração de catalisador, temperatura de calcinação do catalisador, carga metálica nominal. Os resultados indicaram que os catalisadores imobilizados de Fe/Nb2O5 foram eficientes na degradação do Triclosan e da 2,8-diclorodibenzeno-p-dioxina. Os catalisadores com carga nominal de 1,5% de Fe (calcinados a 600 ºC) apresentaram a maior constante de velocidade de reação e menor tempo de meia-vida, 0,069 min-1 e 10,04 min, respectivamente. Testes em diferentes matrizes indicaram que a reação fotocatalítica utilizando solução aquosa com conteúdo Cl- é mais rápida do que quando comparada com a matriz aquosa ultrapura. A geração de 2,8-DCDD e sua subsequente degradação foram realizadas em aproximadamente 80 min de reação. Sendo que o 2,8-DCDD não é totalmente degradado por fotólise. Os resultados apresentados pelas reações em sistema contínuo foram melhores ou equivalentes aos apresentados pelo sistema em batelada. Os parâmetros estudados (wt% Fe e temperatura de calcinação) no delineamento experimental e otimização foram significativos para o processo

Degradation of emerging contaminants: effect of thermal treatment on nb2o5 as photocatalyst

This study describes the use Nb2O5 catalysts – calcined at different temperatures (373–873 K) – in the photo-catalytic degradation reaction of four contaminants of emerging concern: acetylsalicylic acid (ASA), 17α-ethi-nylestradiol (EE2), ibuprofen (IBP) and paracetamol (PAR). The photocatalysts were characterized by different techniques – N2 adsorption/desorption, photoacoustic spectroscopy (PAS), Fourier Transform Infrared (FT-IR) and X-ray diffraction (XRD) – and applied in the photocatalytic degradation tests. Among the tested catalysts, non-calcined Nb2O5 showed the highest photocatalytic activity. The characterization results indicated that this catalyst presented an amorphous (non-crystalline) structure, low band gap and the highest surface area (SBET =182 m2 g-1). A design of experiments (DoE) methodology was applied in order to verify the effects of pH (4–10) and catalyst concentration (0.5–1.5 g L-1) in the four pollutants removal using the non-calcined Nb2O5. Ac-cording to the Experimental Design Analysis, a statistically significant linear effect with a negative coefficient was observed for pH in EE2, IBP and PAR photocatalytic degradation. Tests to verify the influence of the presence compounds together in the degradation reaction of each contaminant, suggested that the photocatalytic degradation of IBP occurs predominantly through the action of radicals O2•-, , with minor contribution from HO•.The authors are thankful to the Brazilian agencies CNPq, CAPES and Fundação Araucária for financial support of this work, C2MMa and Brazilian Mining and Metallurgy Company – CBMM. This work was financially supported by project CIMO (UIDB/00690/2020) through FEDER under Program PT2020.info:eu-repo/semantics/publishedVersio