Search

In the field of heterogeneous photocatalysis, catalyst concentration is one of the main parameters that restricts light availability, specifically in photocatalytic annular slurry reactors design. Therefore, data that describes the dependence of energy on both, distance and catalyst concentration is needed. This paper proposes the local relative light intensity (LRLI) as a quantity that represents the residual energy on radial distance. Experimental measurements of LRLI were made from 0 mm to 25 mm, using two commercial TiO2 powders in a wide range of concentration (200 to 1000 mg/L). Results show that residual energy was less than 80% at 6 mm from the source, for both catalysts in all concentrations. Furthermore, a forward-scattered behavior was detected, the LRLI profiles (LRLI vs radial distance) followed an exponential decay model. All profiles were correlated as a catalysts concentration function. Information obtained was used to develop a methodology to calculate the LRLI values at any radial distance for a settle catalyst concentration. The calculated values of LRLI approaches real data with a relative local accumulated error less than 10% for both catalysts. This methodology may be applied to calculate the energy available in any TiO2/UV-A annular slurry system. [ABSTRACT FROM AUTHOR]

Advanced oxidation processes have gained importance in the last decade because of their application in the treatment of wastewater containing toxic, recalcitrant, and/or colored compounds. The catalyst TiO2, activated with ultraviolet (UV) light, has been used for the degradation of different kinds of compounds, but its activation has been performed with different varieties of UV light without a clear reason for choosing any of the three wavelengths that can be generated with commercially available sources. This work evaluates the degradation speed of acid blue 9 dye through the activation of TiO2 with the different kinds of UV light (UV-A, UV-B, and UV-C). The results indicate that the wavelength of the light used for photoactivation has an impact on the dye degradation speed; shorter wavelengths lead to faster degradation. The analysis of the possible causes affecting the degradation speed was performed by superposing the emission bands of the used UV light with the absorption bands of the dye and catalyst. It is concluded that the interaction zone between the type of UV light and the catalyst notoriously impacts the degradation kinetics. © 2011 American Institute of Chemical Engineers Environ Prog, 2011. [ABSTRACT FROM AUTHOR]

Arsenate adsorption of commercial titanium dioxide (TiO2) Degussa P25 from aqueous solutions was investigated at different temperatures in order to determine the effect of this parameter over TiO2 adsorption capacity of arsenate. The effects of pH and contact time on the adsorption process were examined. Batch experiments were conducted at different arsenate concentrations and temperature values. Results from these experiments were fitted to different empirical models in order to obtain kinetic and equilibrium parameters of the system. Arsenate adsorption reached equilibrium in approximately 50 min. Lagergren and pseudo second order models could describe well the reaction rate at different initial concentration of solution. Maximum adsorption capacities of TiO2 decrease with an increase in temperature, suggesting an exothermic nature of the adsorption process. [ABSTRACT FROM AUTHOR]

The article discusses research on photocatalytic removal of toxic and persistent pollutants from industrial effluents using oxidation processes, titanium dioxide catalysis, and catalyst activation with ultraviolet light. The research uses spectrophotometric analysis to assess the area of influence of an ultraviolet-light source centrally located in a photocatalytic reactor. Experimental trials are described and removal efficiencies achieved for acid blue 9 dye are reported. Reaction kinetics are documented with perspective provided on the comparative effects of catalyst and dye absorption.

This work presents the results obtained from the dosimetric properties of the new radiation detectors of KMgF 3 :Tb + PTFE. The thermoluminescent material was obtained by microwave technique. The polycrystalline powder obtained was mixed with polytetrafluoroethylene resin powder in the ratio 2:3 to make dosimeters in pellet form. The thermoluminescent response of these new detectors presented a linear behavior, in the dose range between 1 and 1000 Gy 60 Co gamma radiation, the repeatability test in the measurements, during ten cycles of heat treatment, irradiation and readouts, showed ± 3.7% DS, the stability test of thermoluminescent signal, during two months showed that the fading is practically null. For the results obtained, this new detector could be very useful for radiation dosimetry, in clinical applications., (Copyright © 2018 Elsevier Ltd. All rights reserved.)