Photocatalytic Conversion of Air Pollutants Energy Efficiencies Overview

PHOTOCATALYTIC CONVERSION OF AIR POLLUTANTS ENERGY EFFICIENCIES OVERVIEW 

Reactor efficiencies can be evaluated for the photocatalytic conversion of water pollutants (Chapter VI) using a number of efficiency factors such as the Electrical Energy per Order (EE/0) (Notarfonzo and McPhee, 1994), the quantum yield, the quantum efficiency (Bockelmann etal., 1993 Valladares andBolton, 1993) and the photocatalytic thermodynamic efficiency factor (PTEF) (Serrano and de Lasa, 1997). 

Extension of these parameters to the photocatalytic conversion of air pollutants is still in the preliminary phases with the quantum yield , a reactor dependant parameter, being the one cuiTently adopted. The quantum yield can be defined as the number of pollutant molecules degraded in a reaction, from either a primary or secondary reaction, over the number of photons absorbed. 

The quantum yield can be in excess to 100% (Cassano etal, 1995). To explain this behavior Ohko et al, (1998) invoke a chain reaction mechanism involving the following steps for the photocatalytic conversion of acetaldehyde  

Preliminary illumination steps leading to the formation of OH radicals TiOi + hv h + e  

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