Photocatalytic Processes for the Removal of Dye - Green Chemistry for Dyes Removal from Wastewater - page 127

proper collectors for concentration of the solar light, and ii) the inability of
using the entire solar spectra, especially the visible one, as most photocata-
lysts are active under UV radiation (300-400 nm).
Solar radiation can be classified into direct and diffuse radiation. Direct
radiation reaches the earth's surface without being absorbed or scattered
by anything, while diffuse radiation is dispersed before reaching the earth's
surface. Global radiation is basically the sum of direct and diffuse radiation
(Figure 4.2) [1].
Figure 4.1 Dye-sensitization Mechanism for Dye Degradation [20].
Figure 4.2 Direct and Global Solar Radiations [1].