Photocatalytic degradation of organic dyes with Sn 2+ - and Ag + -substituted K 3 Nb 3 WO 9 (PO 4 ) 2 under visible light irradiation

A tunnel structure compositions of Ag+- and Sn2+-substituted K3Nb3WO9(PO4)2 photocatalysts were synthesized by an ion exchange method and characterized by powder XRD, SEM–EDS, UV–Vis (DRS), BET and FT-IR. The ion-exchanged products are isomorphous with parent K3Nb3WO9(PO4)2. Absorption edges of Ag+- and Sn2+-doped K3Nb3WO9(PO4)2 samples were red shifted remarkably into the visible light region. Photocatalytic activity of these materials was evaluated by studying the degradation of methylene blue, methyl violet, methyl orange and rhodamine B dyes under visible light irradiation. The photocatalytic properties of these compounds were explained based on their band gap energies, photoluminescence spectra and the amounts of ·OH radicals generated during photocatalysis. The possible photocatalytic mechanistic pathway was discussed. The stability of all catalysts during photocatalytic experiment was also investigated.