Effect of Phosphate Salts (Na₃PO₄, Na₂HPO₄, and NaH₂PO₄) on Ag₃PO₄ Morphology for Photocatalytic Dye Degradation under Visible Light and Toxicity of the Degraded Dye Products

Ag₃PO₄ was synthesized by the precipitation method using three different types of phosphate salts (Na₃PO₄, Na₂HPO₄, and NaH₂PO₄) as a precipitating agent. Hydrolysis of each phosphate salt gave a specific pH that affected the purity and morphology of the prepared Ag₃PO₄. The Ag₃PO₄ prepared from Na₂HPO₄ showed the best photocatalytic activity induced by visible light to degrade methylene blue dye. During the photocatalytic process, Ag₃PO₄ decomposed and produced metallic Ag, and this evidence was confirmed by the X-ray diffraction technique and X-ray photoelectron spectroscopy. The photocatalytic efficiency decreased with the number of recycles used. This Ag₃PO₄ photocatalyst also degraded another cationic dye, rhodamine B, but did not degrade reactive orange, an anionic dye. The degraded products produced by the photocatalysis had lower toxicities than the untreated dyes using Chlorella vulgaris as a bioindicator