Removal of dissolved humic acid from water by photocatalytic oxidation using a silver orthophosphate semiconductor

In order to remove dissolved organic matter such as humic acid from water, a silver orthophosphate (Ag3PO4) was newly employed as a heterogeneous photocatalyst. Here, Ag3PO4 was prepared by simple ion-exchange and precipitation methods, and the physico-chemical properties were characterized by X-ray diffraction, ultraviolet–visible diffuse reflectance spectroscopy, scanning electron microscopy, particle distribution measurements and Brunauer–Emmett–Teller (BET) analysis. The degradation of humic acid was faster over Ag3PO4 catalyst than over conventional TiO2 (P-25). The total photocatalytic properties were improved by employing not an ion-exchange method but a precipitation method; humic acid degradation was performed with a removal ratio of dissolved organic carbon of 75% under visible light (λ = 451 nm) for 2-h irradiation.