Radiation absorption and rate constants for carbaryl photocatalytic degradation in a solar collector

We discuss an analytical model for the evaluation of radiation absorption in a tubular photocatalytic reactor. The model has no adjustable parameters and takes into account scattering in all directions. We compare the results of this model with those of Monte Carlo (MC) simulations and of a Lambert–Beer (LB) approximation, for a reactor illuminated by a parabolic solar concentrator. A good correspondence is found with the MC simulations. In particular, the model displays the correct saturation behavior of absorption for large catalyst particle concentrations, which is not obtained with the LB approximation. We have carried out experiments for the degradation of carbaryl in a solar parabolic collector (PC). The model is used to calculate the rate constant for this degradation from the experimental data. The theoretical model predictions reproduce well, the trends observed in the experiments.     

光活性二氧化钛涂层的研究与制备

本文介绍了制备光活性TiO2涂层的两种主要方法，并就一些影响因素进行了简单的讨论。     

Relevance of Photocatalysis prior to Biological Treatment of Organic Pollutants – Selection Criteria

The relevance of a photocatalytic pretreatment prior to a biological process for removal of organic pollutants was examined. Owing to the significant residual amount and toxicity, amitrole was not relevant. High mineralization allowed to remove bisphenol A and 2,4‐dichlorophenoxyacetic acid. Isoproturon and diuron cannot be considered due to the slight evolution of chemical oxygen demand/total organic carbon (COD/TOC) and average oxidation state during irradiation. After photocatalysis, the ratio of biological oxygen demand (BOD₅)/COD remained below the biodegradability limit (0.4) for the rest of the molecules. A favorable COD/TOC trend (decrease during irradiation) was recorded for dimethoate and antibiotics. However, dimethoate and sulfamethoxazole seemed not pertinent due to the long time span for their removal. Since a decrease of toxicity was only recorded for tylosine, it can be selected for subsequent tests.     

Photocatalytic activity of metal ion (Fe or W) doped titania

Iron or tungsten-doped nano TiO₂ were successfully synthesized from TiCl₄. All of the samples showed anatase phase of TiO₂. For the iron-doped TiO₂, Iron ion was well dispersed in the TiO₂ lattice. However, tungsten-doped TiO₂ formed 12-tungstate with anatase TiO₂. As the concentration of tungsten increased, 12-tungstate disappeared. The photocatalytic oxidation of acetaldehyde was evaluated to examine the photocatalytic characteristics of metal-doped TiO₂. Because of the surface containing metal oxide or metal precursors at high concentration metal ion, increasing the concentration of W or Fe ion decreased the reactivity. The reaction rate was drastically increased after 300 °C heat treatment. Furthermore, the photocatalytic activity of iron- or tungsten-doped TiO₂ was higher than that of synthesized pure TiO₂ and commercial TiO₂.     

半导体多相光催化及其应用

介绍了半导体光催化的应用研究现状,用作光催化剂的材料,光催化剂的制备和性能,阐述了光催化在环境治理方面的应用,并简述了光催化在卫生保健方面的潜在应用价值。     

Advanced Surface of Fibrous Activated Carbon Immobilized with FeO/TiO2 for Photocatalytic Evolution of Hydrogen under Visible Light

FeO-doped TiO₂ nanoparticle photocatalysts were immobilized onto the surface of fibrous activated carbon (ACF) via a sol-gel process. As an adsorbent and photocatalyst, FeO-TiO₂ on immobilized ACFs (FeO-TiO₂/ACF) greatly improved the photocatalysis rate of hydrogen production as compared with pure TiO₂ and ACF-TiO₂ under UV irradiation and visible light. The addition of ACFs surface significantly reduced the photogenerated pairs of electrons-hole recombination, thereby promoting the photocatalysis action of doped photo-metal oxides of FeO-TiO₂. Co-doping of FeO onto the lattice of the TiO₂ approach can improve the absorption activity of visible light through photo-metal oxide of TiO₂ and further enhance hydrogen production under visible light. The photocatalytic fabrics (FeO-TiO₂/ACF) were effortlessly split out from the experimental solution for re-utilization and exhibited high stability even after five complete regeneration cycles.     

DyCrxFe(1-x)O3 nanoparticles prepared by wet chemical technique for photocatalytic applications

DyCr_xFe_(1-x)O₃ (0 ≤ x ≥ 0.4) nanoparticles were prepared using facile chemical route. Structural and morphological evaluation was carried out using X-ray diffraction (XRD) and electron microscopy. Formation of orthorhombic DyFeO₃ nanoparticles was confirmed by XRD with crystallite size of 9–10 nm. FESEM images revealed nearly spherical morphology of the fabricated nanoparticles. Energy dispersive X-ray (EDX) technique was employed to confirm the presence of Dy, Cr, Fe and O elements in DyCr_xFe_(1-x)O₃ nanoparticles. FTIR studies illustrated the presence of characteristics stretching and bending vibrations. UV–visible spectroscopy was used to analyze the photocatalytic performance of the DyFeO₃ and Cr-substituted DyFeO₃ nanoparticles and optical band gap measurements. Photocatalytic activities of the prepared substituted and un-substituted DyFeO₃ nanoparticles were conducted using three different dyes. These dyes were (i) methyl orange, (ii) rhodamine B and (iii) methylene blue. Lower band gap and higher photocatalytic performance was observed for Cr-substituted DyFeO₃ nanoparticles with methylene blue dye.