http://publicationslist.org/data/meng.chong/ref-18/sdarticle.pdf

Recent Developments in Photocatalytic Water Treatment Technology: A Review

Photoinduced reactivity of titanium dioxide

When titanium dioxide (TiO(2)) is irradiated with near-UV light, this semiconductor exhibits strong bactericidal activity. In this paper, we present the first evidence that the lipid peroxidation reaction is the underlying mechanism of death of Escherichia coli K-12 cells that are irradiated in the presence of the TiO(2) photocatalyst. Using production of malondialdehyde (MDA) as an index to assess cell membrane damage by lipid peroxidation, we observed that there was an exponential increase in the production of MDA, whose concentration reached 1.1 to 2.4 nmol. mg (dry weight) of cells(-1) after 30 min of illumination, and that the kinetics of this process paralleled cell death. Under these conditions, concomitant losses of 77 to 93% of the cell respiratory activity were also detected, as measured by both oxygen uptake and reduction of 2,3,5-triphenyltetrazolium chloride from succinate as the electron donor. The occurrence of lipid peroxidation and the simultaneous losses of both membrane-dependent respiratory activity and cell viability depended strictly on the presence of both light and TiO(2). We concluded that TiO(2) photocatalysis promoted peroxidation of the polyunsaturated phospholipid component of the lipid membrane initially and induced major disorder in the E. coli cell membrane. Subsequently, essential functions that rely on intact cell membrane architecture, such as respiratory activity, were lost, and cell death was inevitable.

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Bactericidal activity of photocatalytic TiO(2) reaction: toward an understanding of its killing mechanism.

Band-gap determination from diffuse reflectance measurements of semiconductor films, and application to photoelectrochemical water-splitting

The aim of this review is to offer an overview of the evolution in the use of different anchors (supports) for the immobilisation of a semiconductor photocatalyst, which is titanium dioxide (TiO2). Several supports and immobilisation techniques that are commonly used for the removal of contaminants in wastewater are discussed. Generally, the immobilisation of a photocatalyst onto supporting material has largely been carried out via one of two major routes; physical (the thermal treatment method) route or chemical (the sol–gel method, chemical vapour deposition, electrodeposition, etc.) route. The benefits and drawbacks of various immobilisation techniques to obtain a high surface area TiO2 support are also discussed.

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Immobilisation of titanium dioxide onto supporting materials in heterogeneous photocatalysis: A review

TiO2 powder was immobilised on solid support substrates (stainless steel, titanium alloy, titanium metal, and tin oxide coated glass) using electrophoretic coating and spray coating. Electrochemical anodisation of titanium metal was also carried out to give a thin film of TiO2 on the surface. The coated substrates were annealed in air at elevated temperatures to improve the adhesion of the catalyst to the supporting substrates. The photocatalytic efficiency of the TiO2 coatings was compared using the degradation of phenol in aqueous solution as a standard test system. In the case of the powder derived films, the photocatalytic efficiency was found not to be markedly dependent upon either the substrate used or the annealing temperature employed in the coating process. Surface analysis of the immobilised TiO2 showed no significant differences in the elemental composition or in band gap energies. The electrophoretic coating method was found to be the most reproducible resulting in highly fractured thick films with high photocatalytic activity. (C) 1998 Elsevier Science B.V.

B. McKinney

Papers

Immobilisation of TiO2 powder for the treatment of polluted water