Solar photocatalytic reactors types

Different types of solar photocatalytic reactors have been developed over time. Two main distinctions have been made (i) concentrating versus nonconcentrating reactors and (ii) slurry versus fixed catalyst reactors. These two classifications are not mutually exclusive, and other categories may also be established, for instance, a very important is the one of tubular solar photoreactors. 

Solar photocatalytic reactors can be operated in either continuous single pass mode or discontinuous batch mode. In the continuous single pass mode, complete oxidation of the contaminant is achieved in a single pass with the water flow rate being adjusted for fixed solar flux densities. On the other hand, batch mode operation requires a set volume of water to be treated with varying solar flux densities (Alfano et al., 2000). Table 2.4 reports the main types of solar reactors reported in the technical literature. 

The choice of the light source—form, emitted wavelengths, radiant power— depends inter alia on whether Ti02 is unsupported or supported, and on the type and shape of the supporting material. For example, a Ti02-coated flexible material can be wrapped around a cylindrical lamp placed inside the reactor. A plate covered by Ti02 can be installed perpendicularly to the beam of a lamp located outside the reactor. Obviously, the choice of the lamp, especially of the emission characteristics, also depends on the objective. For instance, in view of solar photocatalytic applications, lamps mimicking solar irradiation at the Earth s level or a solar box can be used in the laboratory. 

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