Tungstophosphate Intercalated ZnAl Layered Double Hydroxide for Adsorptive and Visible Light Driven Photocatalytic Decolourisation of Organic Dyes

Abstract

Tungstophosphate (PW₁₂O₄₀^3-) intercalated ZnAl-Layered double hydroxide (ZnAl-PW₁₂) was successfully synthesized through the rehydration of calcined LDH. Chemical analyses and characterizations by powder XRD, FT-IR, and Diffuse reflectance UV-Vis spectra confirmed the intercalation of PW₁₂O₄₀^3- ions equivalent to ~80% of the residual positive charge in the brucite layer. The efficiency of ZnAl-PW₁₂ for decolourisation of four structurally different cationic/anionic dyes through simultaneous adsorption and photocatalysis under visible light irradiation was assessed. Under identical conditions, the photocatalytic efficiency of the ZnAl-PW₁₂ catalyst was found to be much higher than that of calcined ZnAl-LDH, indicating the promoting effect of PW₁₂O₄₀^3- ion. Moreover, the loss of costly polyoxometallate (POM) could be avoided by intercalating the POM ion in the interlayer of LDH, which can facilitate the use of synthesized catalysts for repeated cycles.