Valence heterogeneous photocatalysis

Heterogeneous Photocatalysis. Heterogeneous photocatalysis is a technology based on the irradiation of a semiconductor (SC) photocatalyst, for example, titanium dioxide [13463-67-7] Ti02, zinc oxide [1314-13-2] ZnO, or cadmium sulfide [1306-23-6] CdS. Semiconductor materials have electrical conductivity properties between those of metals and insulators, and have narrow energy gaps (band gap) between the filled valence band and the conduction band (see Electronic materials Semiconductors). 

Having reviewed photochemical valence adjustment of Np in nitric acid solution, we will briefly consider the effect of heterogeneous Pt particle catalysts on Np speciation reactions in the dark before discussing applications of heterogeneous photocatalysis in Np redox chemistry. 

Homogeneous photochemical and heterogeneous catalytic processes are attractive because they do not increase the volume of secondary waste. Heterogeneous photocatalysis offers the further advantage that, post valence control, any additives such as HAN can be photocatalytically degraded to readily disposable gases such as N2 and C02. This will be explored further in the next section. 

As advanced in chapter I, the basic mechanism of heterogeneous photocatalysis is related to the exciting of the TiOa or other metal oxides. It is generally accepted that this photon-induced state of excitation promotes an electron from the valence band level to... 

Given the importance of the oxidation states of the actinides in reprocessing and the capability of heterogeneous semiconductor photocatalysts to manipulate the valence states of a wide range of metal ions, attention has been given to the potential applications of photocatalysis in nuclear reprocessing scenarios [59-65]. The attractions of this are twofold, and lead to a further minimisation of the environmental impact associated with fuel use and processing ... 

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