This paper summarizes recent research dealing with development of titanium dioxide (TiO2) used for environmental applications. TiO2 plays the most important role owing to its excellent chemical and physical properties. However, the TiO2 band edge lies in the UV region that makes them inactive under visible irradiation. In this regard, considerable efforts have been made to increase the visible light activity of TiO2 via the modification of its electronic and optical properties. Doping TiO2 using either anions or cations is one of the typical approaches that has been largely applied. Coupling TiO2 with a narrow bad gap semiconductor (MxOy/TiO2 or MxSy/TiO2) represents another approach. This work aims to encompass the new progress of TiO2 for an efficient application in water and wastewater treatment under visible light, emphasizes the future trends of TiO2 in the environment, and suggests new research directions, including preparation aspects for the development of this promising material.

Modified TiO2 For Environmental Photocatalytic Applications: A Review

Climate change and the consumption of non-renewable resources are considered as the greatest problems facing humankind. Because of this, photocatalysis research has been rapidly expanding. TiO2 nanoparticles have been extensively investigated for photocatalytic applications including the decomposition of organic compounds and production of H2 as a fuel using solar energy. This article reviews the structure and electronic properties of TiO2, compares TiO2 with other common semiconductors used for photocatalytic applications and clarifies the advantages of using TiO2 nanoparticles. TiO2 is considered close to an ideal semiconductor for photocatalysis but possesses certain limitations such as poor absorption of visible radiation and rapid recombination of photogenerated electron/hole pairs. In this review article, various methods used to enhance the photocatalytic characteristics of TiO2 including dye sensitization, doping, coupling and capping are discussed. Environmental and energy applications of TiO2, including photocatalytic treatment of wastewater, pesticide degradation and water splitting to produce hydrogen have been summarized.

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A review of TiO 2 nanoparticles

Organic dyes are one of the largest groups of pollutants released into wastewaters from textile and other industrial processes. Because of potential toxicity of the dyes and their visibility in surface waters, removal and degradation of organic dyes have been a matter of considerable interest. A wide range of methods have been developed, amongst which the heterogeneous photocatalysis involving titanium dioxide (TiO2) appears to be the most promising technology. This paper presents a critical review of novel achievements in the modification of TiO2 photocatalytic systems aimed at: enhanced TiO2 photocatalytic efficiency; complete mineralization of organic dyes; efficient utilization of visible and/or solar light; stability and reproducibility of the modified TiO2; recycle and reuse in real wastewater treatment.

Tailored titanium dioxide photocatalysts for the degradation of organic dyes in wastewater treatment: A review

Chemical deposition method for metal chalcogenide thin films

Bi2S3/TiO2 and CdS/TiO2 heterojunctions were prepared by direct mixture of both constituents and by precipitation of the sensitizer with commercial TiO2 at different concentrations. UV-Vis spectroscopy analysis showed that the junctions-based Bi2S3 and CdS are able to absorb a large part of visible light (respectively up to 800 and 600 nm). This fact was confirmed by photocatalytic experiment performed under visible light. A part of charge recombination that can take place when both semiconductors are excited was observed when photocatalytic experiment was performed under UV-Vis illumination. Orange II, 4-hydroxybenzoique acid (4-HBZ) and benzamide (BZ) were used as pollutants. Photoactivity of the junctions was found to be strongly dependent on the substrate. The different phenomena taking place in each case are discussed.

Bi2S3/TiO2 and CdS/TiO2 heterojunctions as an available configuration for photocatalytic degradation of organic pollutant

Structural characterization of Bi2−xSbxS3 films prepared by the dip-dry method

The dip-dry technique for preparing photosensitive Sb2S3 films

Alloy films of Pb1−xCdxS have been prepared on glass substrates by electroless deposition from a chemical bath Structural characterisation of the alloy was carried out by x-ray powder diffraction technique using Debye-Scherrer camera The study shows that Pb1−xCdxS exists in cubic phase and the lattice constants are found to be greater than individual CdS and PbS value This expansion of lattice is possibly due to interstitials The lattice constants have been found to vary linearly with atomic percent of cadmium sulphide The SEM micrographs show that particle size increases with increase in atomic percent of cadmium sulphide in the alloy

G.B. Mitra

Papers

Structural characterization of Bi2−xSbxS3 films prepared by the dip-dry method

The dip-dry technique for preparing photosensitive Sb2S3 films

Preparation and structural characterisation of chemically deposited Pb1−xCdxS films