On the underlying mechanisms of the low observed nitrate selectivity in photocatalytic NO abatement and the importance of the oxygen reduction reaction.

Semiconductor photocatalysis could be an effective means to combat air pollution, especially nitrogen oxides, which can be mineralized to nitrate. However, the reaction typically shows poor selectivity, releasing a number of unwanted and possibly toxic intermediates such as nitrogen dioxide. Up to now, the underlying principles that lead to this poor selectivity were not understood so a knowledge-based catalyst design for more selective materials was impossible.

The Effect of Interfacial Chemical Bonding in TiO2-SiO2 Composites on Their Photocatalytic NOx Abatement Performance.

The chemical bonding of particulate photocatalysts to supporting material surfaces is of great importance in engineering more efficient and practical photocatalytic structures. However, the influence of such chemical bonding on the optical and surface properties of the photocatalyst and thus its photocatalytic activity/reaction selectivity behavior has not been systematically studied. In this investigation, TiO2 has been supported on the surface of SiO2 by means of two different methods: (i) by the in situ formation of TiO2 in the presence of sand quartz via a sol-gel method employing tetrabutyl orthotitanium (TBOT); and (ii) by binding the commercial TiO2 powder to quartz on a surface silica gel layer formed from the reaction of quartz with tetraethylorthosilicate (TEOS).

Different Roles of Water in Photocatalytic DeNOx Mechanisms on TiO: Basis for Engineering Nitrate Selectivity?

The nitrate selectivity of TiO has important consequences for its efficiency as a NOx depollution photocatalyst. Most emphasis is typically given to photocatalyst activity, a measure of the rate at which NOx concentrations are reduced, but a reduction in NOx concentration (mainly NO + NO) is not necessarily a reduction in atmospheric NO concentration because the catalytic process itself generates NO. With NO being considerably more toxic than NO, more emphasis on nitrate selectivity, a measure of the NOx conversion to nitrate, and how to maximize it, should be given in engineering photocatalytic systems for improved urban air quality.

Properties and photochemistry of valence-induced-Ti(3+) enriched (Nb,N)-codoped anatase TiO2 semiconductors.

Nb and N codoped TiO2s are outstandingly versatile semiconductor oxides. Their high conductivity makes them valid alternatives to commercially available, but very expensive, conductive oxides. They show increased photonic efficiencies compared to the cases of solely Nb or N doped TiO2, when used as visible light sensitised photocatalysts.

Remediation of a chlorinated aromatic hydrocarbon in water by photoelectrocatalysis.

Photoelectrocatalysis driven by visible light offers a new and potentially powerful technology for the remediation of water contaminated by organo-xenobiotics. In this study, the performance of a visible light-driven photoelectrocatalytic (PEC) batch reactor, applying a tungsten trioxide (WO(3)) photoelectrode, to degrade the model pollutant 2,4-dichlorophenol (2,4-DCP) was monitored both by toxicological assessment (biosensing) and chemical analysis. The bacterial biosensor used to assess the presence of toxicity of the parent molecule and its breakdown products was a multicopy plasmid lux-marked E.

The use of 'exotic' framework structures in waste management.

The use of porous framework materials in waste management applications has the potential to be a powerful tool in toxic metal remediation. The properties that these materials possess, including high surface area and ion-exchange capacity, are theoretically valuable. Furthermore, the flexibility of many of these frameworks allows the potential for immobilisation of waste materials with the framework of the material, in addition to the traditional capture in the pore structure.

Synthesis and proposed crystal structure of a disordered cadmium arsenate apatite Cd5(AsO4)3Cl(1-2x-y)O(x)[symbol: see text](x)OH(y).

During a study into the synthesis of minerals composed of mining wastes aimed at improving their immobilisation, a cadmium arsenate apatite has been prepared by hydrothermal methods. The structure of this apatite was analysed by single crystal X-ray diffraction, and was found to consist of a standard apatite framework based on Cd(5)(AsO(4))(3)X, where X represents an anion resident on the (0,0,0.25) site.

New low temperature synthetic route to an ammonium zinc arsenate zeolite analogue with an ABW-type structure.

The synthesis and stability of zeolite analogues are of potential interest to the waste management community as waste metals may be used in the framework of these materials. A new synthetic route to an ABW-type ammonium zinc arsenate is proposed. The stability of this material is then examined in an aqueous environment by quantitative X-ray diffraction and leach testing.