Zeolite encapsulated active metal composites and their photocatalytic studies for rhodamine-B, reactive red-198 and chloro-phenols

Abstract

Niobium (Nb), tantalum (Ta) and palladium (Pd) were impregnated in the cavities of a zeolite by the ion exchange method. The impregnation and composites stability were investigated by FTIR, DRS/UV-visible, XRD, XPS, BET, N₂ adsorption isotherms, AAS, FESEM/EDX, TEM, TGA and particle size. The composites denoted as PdY, NbPdY and TaPdY were used as visible light driven photocatalysts in the degradation of Rhodamine-B (RhB), reactive red-198 (RR), 2-chloro phenol (2CP) and 4-chloro phenol (4CP) under visible light irradiation. The composites catalytic ability was determined by UV-visible absorption spectral analysis. The TaPdY, and NbPdY exhibit superior degradation kinetics when compared to that of PdY and NaY, due to the presence of refractory metals such as Nb(V) and Ta(V) in the zeolite cavities. The percentage of degradation and rate of reaction is more for NbPdY and TaPdY. The photo oxidation reaction follows pseudo-first order reaction kinetics and this might be due to the fixed concentration of the reactants, photocatalysts and reaction medium. The NbPdY and TaPdY catalysts are recoverable and reusable for up to five cycles of repeated usage. The recovered and reusable catalyst shows comparable activity with that of the fresh catalyst.