New W doped TiO2 Photocatalysts by the Sol-Gel Method Essay

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In the 1930s, the term photocatalysis was introduced as a new branch of catalysis [1]. Among photocatalytic applications, photocatalytic oxidation and the reduction of organic compounds in water, have become important and have received considerable attention during the last few years [1, 2]. Owing to its excellent catalytic and oxidative properties; titanium dioxide, TiO2, has been frequently employed to degrade most kinds of organic pollutants. Including detergents, dyes, pesticides and herbicides under UV-light irradiation in order to transform them in water, carbon dioxide and some simple mineral acids [3-6]. However, titanium dioxide was used also for other catalytic applications [7, 8]. Among the three common phases of crystalline …show more content…
Various tungsten precursors (H2WO4, W(OEt)5,(NH4)6H2W12O40,WCl6, etc.) and different techniques for doping (impregnation, sol–gel, flame spray synthesis, etc.) were used in these different researches [23,24]. As a result, the different photocatalytic tests and the various experimental conditions used do not allow comparing the obtained results. Moreover, the most prepared W-TiO2 catalysts cited in the literature are of high level of W doping andrelatively weak surface area. Thus, the aim of this research is to prepare, by a simple sol-gel method, a new weakly W-modified TiO2 having a high surface area. It is expected that the new W-TiO2photocatalyst allows a better visible light absorption and a higher photocatalytic activity than the prepared pure TiO2 and the Degussa P25. The Congo Red (CR) (Schema 1) was used as a pollutant model for testing the prepared photocatalysts. Several operational parameters were studied such as the W loading and the heat treatment temperature of the photocatalysts.

Schema 1: Molecular structure of Congo red dye.

2. Experimental
2.1. Materials
All reagents used were of analytical grade and employed as received. Titanium tetraisopropoxide (TTiP) and tungstic acid H2WO4 were purchased from Aldrich Chemicals. Propanol (C3H7OH) and acetic acid (CH3COOH) were obtained from Merck Chemicals.Theazo dye used in the experiments is Congo Red.
2.2. Photocatalyst preparation

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