Core-shell catalyst applied in the photocatalytic reduction of selenium

In the present work, the synthesis of CoFe2O4@TiO2core-shell photocatalysts was performed by the sol-gel method, followed by their characterization and application to the Se (IV) photocatalytic reduction. To guide both catalyst synthesis and photocatalytic experiments, a central composite design was applied. The considered factors were: calcination temperature, titanium isopropoxide concentration (% v/v) in ethanol used in catalyst synthesis and pH of the solution used in the photocatalytic test. The techniques applied for the photocatalysts characterization were: N2 adsorption-desorption measurement, photoacoustic spectroscopy (PAS), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive Xray spectroscopy (EDS) and point of zero charge (PZC) determination. The results indicated that the most significant factors for photocatalytic removal of Se (IV) were the calcination temperature and the pH of the solution. The best conditions for increasing selenium removal within 2 minutes of photocatalysis are lower calcination temperatures (around 300 ºC) and pH around 3.5. The percentage of isopropoxide in ethanol used in the synthesis had little influence on both selenium photoreduction and catalyst properties. The calcination temperature also significantly affected the specific surface areas, bandgapand structure of the photocatalysts.Universidade Tecnológica Federal do Paraná (UTFPR)Neste trabalho, foi realizada a síntese de fotocatalisadores core-shell CoFe2O4@TiO2 pelo método sol-gel, seguida de sua caracterização e aplicação à redução fotocatalítica de Se(IV). Para orientar tanto a síntese dos catalisadores como a realização dos testes fotocatalíticos, utilizou-se um planejamento experimental composto central do tipo rotacional. Os fatores estudados foram: temperatura de calcinação, concentrações (% v/v) de isopropóxido de titânio em etanol utilizado na síntese do catalisador e pH da solução durante o teste fotocatalítico. As técnicas empregadas para caracterizar os fotocatalisadores foram: medida de adsorçãodessorção de N2, espectroscopia fotoacústica (PAS), difratometria de raios X (DRX), microscopia eletrônica de varredura (MEV), espectroscopia por energia dispersiva de raios X (EDS) e ponto de carga zero (PCZ). Os resultados indicaram que os fatores mais significativos para remoção fotocatalítica do Se(IV) são a temperatura de calcinação do fotocatalisador e o pH da solução. As melhores condições para aumentar a remoção de selênio em 2 minutos de fotocatálise consistem no emprego de temperaturas mais baixas (próximo a 300 ºC) para calcinação e pH próximo de 3,5. O percentual de isopropóxido em etanol usado na síntese apresentou pouca influência tanto na fotorredução do selênio como nas propriedades dos catalisadores. A temperatura de calcinação também afetou significativamente a área superficial específica, bandgape a estrutura dos fotocatalisadores

Reactive Processes for H₂S Removal

Growing demand for renewables and sustainable energy production contributes to a growing interest in producing high quality biomethane from biogas. Despite having methane (CH4) as its main component, biogas may also present other noncombustible substances in its composition, i.e., carbon dioxide (CO2), nitrogen (N2) and hydrogen sulfide (H2S). Contaminant gases, such as CO2 and H2S, are impurities known for being the main causes for the decrease of biogas calorific value and corrosion, wear of pipes, and engines, among others. Thus, it is necessary to remove these compounds from the biogas before it can be used in applications such as electricity production, thermal purposes, and replacement of conventional fossil fuels in vehicles, as well as injection into natural gas distribution networks. In this context, the present work aimed to present a systematic review of the literature using the multicriteria Methodi Ordinatio methodology and to describe processes and materials for H2S removal. The discussion indicated new materials used, as well as the advantages and disadvantages observed and the limitations in industrial implementation

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