Diatomite/silver phosphate composite for efficient degradation of organic dyes under solar radiation

In this study, an effort has been made to synthesize diatomite/silver phosphate (DT/AgP) composites and dye degradation test was carried out to evaluate the photocatalytic activity under solar light irradiation. Diatomite–silver phosphate composites with different DT/AgP ratios were prepared by precipitation of Ag3PO4 on diatomite that led to the formation of small Ag3PO4 particles on the diatomite surfaces. UV–visible diffuse reflectance analysis shows that DT/AgP composites can absorb visible wavelength, whereas TiO2 catalyst only work under UV irradiance. Compared to pure AgP, the composite samples show higher specific surface area measured by Brunauer–Emmett–Teller analysis. Dye degradation test under solar light irradiation reveals that the photocatalytic reaction follows a pseudo-first-order rate law and the composite catalyst with DT/AgP ratio 1:0.8 shows better catalytic activity towards both rhodamine B and methyl orange degradation. As reference, a well-known commercial TiO2 (Evonik-P25) was used in dye degradation test. It could be presumed that deposition of silver phosphate clusters (Ag3PO4, AgP) on diatom frustules (diatomite) provided an efficient photocatalyst activated by solar light irradiation.