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.

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The aim of this work was to synthesize lead zirconate titanate (PZT) nanopowder using a modified solgel processing method. PZT obtained by a sol-gel route using acetic acid had compositions in the morphotropic phase boundary (Ti/Zr, 53/47 and 45/55). All samples were annealed in air at 800°C and sintered at temperature above 1,000°C. Structure and morphology of the samples were determined and characterized by X-ray diffraction, transmission electron microscopy, Raman spectroscopy, dilation, densification and pyroelectric response. Results of X-ray diffraction on samples PZT showed a phase, but not a pyrochlore one, which we determined to be the best pyroelectric response. The samples presented high densification and had appropriate characteristics when used as pyroelectric sensors. Ceramics with a composition of 53/47 had the best pyroelectric response. An average particle size of 20 nm was measured using TEM.

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The current research work presents a methodology for determining the area of influence of the ultraviolet light emitted by a lamp located in the center of a photocatalytic reactor, at different concentrations of the catalyst TiO 2 degussa P25 and of the acid blue 9 dye. The measurements for the development of the corresponding methodology were performed through a novel system that allows the evaluation of light intensity at different distances from the lamp and at real working concentrations (with no dilution). The results obtained from these measurements indicate that for 600 mg L 21 , 450 mg L 21 , 300 mg L 21, and 150 mg L 21 catalyst concentrations there is complete absorption of the light emitted by the lamp at distances of 0.8, 1.0, 1.6, and 2.4 cm, respectively. For the dye it was observed that at 2.4 cm from the lamp, there is an intensity reduction in the order of 91%, 85%, 71%, and 50% The results obtained with the application of the developed methodology for the evaluation of the combined effect of the catalyst and dye absorption, show that, the absorption of the catalyst is more important than that of dye in the concentrations evaluated. With higher catalyst concentration, complete light absorption happens closer to the lamp wall, which produces an increment in the reaction kinetics; with higher dye concentrations, the amount of energy reaching by the catalyst decreases and causes an exponential decrease in the reaction kinetics.

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