Suchergebnisse

The urban environment is facing serious problems caused by automobile exhaust pollution, which has led to a great impact on human health and climate, and aroused widespread concern of the government and the public. Nano titanium dioxide (TiO(2)), as a photocatalyst, can be activated by ultraviolet irradiation and then form a strong REDOX potential on the surface of the nano TiO(2) particles. The REDOX potential can degrade the automobile exhaust, such as nitrogen oxides (NO(x)) and hydrocarbons (HC). In this paper, a photocatalytic environmentally friendly pervious concrete (PEFPC) was manufactured by spraying nano TiO(2) on the surface of it and the photocatalytic performance of PEFPC was researched. The nano TiO(2) particle size, TiO(2) dosage, TiO(2) spraying amount, and dispersant dosage were selected as factors to investigate the efficiency of photocatalytic degradation of automobile exhaust by PEFPC. Moreover, the environmental scanning electron microscope (ESEM) was used to evaluate the distribution of nano TiO(2) on the surface of the pervious concrete, the distribution area of nano TiO(2) was obtained through Image-Pro Plus, and the area ratio of nano TiO(2) to the surface of the pervious concrete was calculated. The results showed that the recommended nano TiO(2) particle size is 25 nm. The optimum TiO(2) dosage was 10% and the optimum dispersant dosage was 5.0%. The photocatalytic performance of PEFPC was best when the TiO(2) spraying amount was 333.3 g/m(2). The change in the photocatalytic ratio of HC and NO(x) is consistent with the distribution area of nano TiO(2) on the surface of the pervious concrete. In addition, the photocatalytic performance of PEFPC under two light sources (ultraviolet light and sunlight) was compared. The results indicated that both light sources were able to stimulate the photocatalytic performance of PEFPC. The research provided a reference for the evaluation of automobile exhaust removal performance of PEFPC.

In this article powdered composites of titanium dioxide and silica with high-developed surface(183–534 m2 / g), synthesized from industrial wastes, are considered as photocatalytic concrete additives. Their composition was studied, and the photocatalytic performance was evaluated by decomposition of the dye "Methylene blue" under UV-irradiation. The surfactant's concentration at which the photocatalytic activity reaches its highest values was determined.

AbstractPhotocatalytic coatings have the potential to contribute to the purification of water via an advanced oxidation process (AOP). A commonly used method for analyzing the mechanism of the photocatalytic performance of a given reactor type is to document the degradation behavior in a solution containing methylene blue. However, since methylene blue is rather unstable, the degradation results should be viewed critically. In this work, the degradation behavior of a test solution with methylene blue on quartz glass surfaces coated with photocatalytic titanium dioxide (TiO2) of the anatase modification was investigated through a variety of different light sources. The coating was deposited by physical vapor deposition (PVD) with the reactive pulsed DC magnetron sputtering ion plating (MSIP) method described in the study by Desch and Lake, while the quartz glasses were coated with a 100 nm thick TiO2 coating on the outside. The same glasses were used for all experiments with TiO2. In the determination of the degradation rate, additional experiments were performed using pure quartz glass without any coating, which made it possible to examine the influence of different light sources on the degradation rate of methylene blue in general. Three different light sources, namely UV‐A, UV‐C, and simple fluorescent lamps were used in this study. The concentration of methylene blue was recorded by photo spectrometer in 10‐min increments throughout the experiment and the experiments were performed for 24 h in all cases. Our data indicates that the methylene blue test is a poor method because the degradation rate is not clearly differentiable due to the low stability of the test substance. Without including reference testing in the absence of a catalyst, data may be subject to misinterpretation.

Semiconductor-based heterogeneous photocatalysis has been one of the most promising processes for the treatment of contaminated water. Among the available catalysts, titanium dioxide (TiO2) presents the best photocatalytic properties, being chemically and biologically inert, stable, non-toxic, cheap and easy to produce. However, its energy bang gap lies in the ultraviolet (UV) range, which is responsible for a reduced spectral activation, since UV radiation corresponds to only 5% of the solar spectrum [1]. For this reason, one of the main purposes of the scientific community has been to improve the photocatalytic performance of TiO2, namely through an adequate doping of this material, or through the creation of nanocomposites, to enable photocatalysis occurrence by the incidence of visible light. One alternative concerns the application of nanocomposites of TiO2 with graphene and graphene oxide to photocatalytic processes [2]. In this work, nanocomposites of TiO2 with different weight concentrations of graphene and graphene oxide (namely 0.5%, 1%, 1.5% and 3%) were synthetized by a one-step hydrothermal method and characterized in terms of morphology, crystalline structure, vibrational modes and optical band gap. The photocatalytic activity of these nanocomposites was then evaluated through the degradation of methylene blue and ciprofloxacin solutions under UV and visible radiation. The results indicated that the studied nanocomposites presented higher degradation rates of the methylene blue than the pure TiO2, which increased with the content of graphene/graphene oxide. However, these composites proved to be less suitable to degrade the ciprofloxacin solution than the pure TiO2 nanoparticles. ; Portuguese Foundation for Science and Technology (FCT) - UID/FIS/04650/2013, PTDC/CTM-ENE/5387/2014 and SFRH/BD/98616/2013; Basque Government Industry Department under the ELKARTEK Program. ...

In the present work, innovative photocatalytic processes were developed for the abatement of harmful N-containing compounds, focusing on selectivity towards innocuous N2, to be applied for the treatment of waste waters to meet legislative specifications. The photocatalytic performance of the samples has been checked for the photoreduction of nitrate ions, the photooxidation of ammonia and of organic N-containing compounds. Catalytic performance was correlated with the properties of the nanomaterials. Two innovative semi-batch photoreactors were specifically designed and optimized for this application. Different photocatalysts have been compared. TiO2 has been prepared in nanosized form by using an innovative flame pyrolysis (FP) approach, able to synthesise in one step single or mixed oxide nanoparticles, characterized by homogeneous particle size and good phase purity. In some cases Pd has been added to TiO2 by post synthesis impregnation. The role of the metal nanoparticles was the enhancement of the lifetime of the photoproduced charges by electron trapping. The same materials formulations have been prepared starting from commercial nanostructured TiO2 supports for comparison purposes. The addition of Pd revealed the key to improve both the conversion and the selectivity to N2. The FP prepared materials were in general more active than the commercial TiO2 P25 sample.

Abstract
Background
The discard of used adsorbents may pose a great threat to human health and ecological environment. This work herein reported a facile and feasible method, with aims of (i) reusing the calcined layered double hydroxide (CLDH) adsorbent after azo dye adsorption, and (ii) being further used as a photocatalyst to enhance the degradation of typical pharmaceuticals. Calcination under inner gas flow has been utilized to carbonize adsorbed azo dye and a kind of novel carbonaceous CLDH composite material (CM-CLDH) was synthesized. This fabricated material was used as a catalyst for Ibuprofen removal in water samples under simulated sunlight irradiation.

Results
According to our experimental results, combination of carbonaceous material with CLDH showed an enhanced photocatalytic performance compared to original CLDH materials. More than 90% of Ibuprofen could be removed in less than 180 min. Introduction of carbon material narrowed catalyst's band gap and turned its conduct band potential to a more negative state, which brought considerable light absorption and higher oxidation ability of photo-induced electrons. Furthermore, photoluminescent spectra and transient photocurrent examination confirmed that carbon material suppressed recombination of photo-induced electrons and holes through faster electron transportation. Under experimental conditions, the removal efficiency of Ibuprofen by CM-CLDH composite kept above 90% during five cycles.

Conclusion
Calcination under inner gas flow can transform organic pollutant-adsorbed CLDH to CM-CLDH composite with higher photocatalytic performance. A feasible way to reuse spent LDH adsorbents was proposed, which is a benefit to reduce second pollution of spent adsorbents in environment.

This paper reports the development and characterization of a multifunctional coating that combines anticorrosion and photocatalytic properties, deposited by means of the electrospinning technique. In the first step, a functional electrospun fiber mat composed of poly(acrylic acid) (PAA) and β-cyclodextrin (β-CD) was obtained, showing high water insolubility and great adhesion increased by means of a thermal crosslinking process (denoted as PAA + β-CD). In the second step, the fibers were doped with particles of titanium dioxide (denoted as PAA + β-CD/TiO2) and titanium dioxide plus iron oxide (denoted as PAA + β-CD/TiO2/Fe2O3). The morphology and fiber diameter of the electrospun mats were evaluated by using confocal microscopy, whereas the presence of the metal oxides in the electrospun fibers was corroborated by scanning electron microscopy (SEM) and X-ray fluorescence (XRF), respectively. In addition, electrochemical tests in saline solution revealed that the sample composed of PAA + β-CD/TiO2/Fe2O3 showed the highest corrosion protection efficiency of all the samples, which was directly associated to lower corrosion current density and higher corrosion potential. Furthermore, the paper reports a novel approach to in situ determination of methylene blue (MB) degradation onto the coating. The results revealed complete degradation of MB, which is perfectly appreciated by total discoloration of the film in the irradiated zone (from bluish to a white spot). The main conclusions of this research are the efficiency of the electrospun system PAA + β-CD/TiO2/Fe2O3 for developing photocatalytic activity and corrosion protection and the utility of the dry MB discoloration tests to evaluate photocatalytic activity. ; This research was funded by the Government of Navarra-Department of Economic Development (Project ARGITU) and by the Public University of Navarre (Project PJUPNA1929).