Microwave Synthesis and Photocatalytic Activity of Nano Lanthanide (Ce, Pr, and Nd) Orthovanadates

Lanthanide orthovanadates, CeVO4, PrVO4, and NdVO4, of nanodimensions were synthesized under microwave exposure, and the photocatalytic activities of these compounds were investigated. These compounds exhibit a tetragonal zircon structure, crystallizing in the space group I41/amd with a = 7.3733(4) and c = 6.4909(4) Å with Z = 4. The crystal structure was analyzed by powder X-ray diffraction, and the band gap was analyzed by UV−visible spectroscopy. Particle sizes were in the range of 25−30 nm, as observed by transmission electron microscopy. While the energy dispersive X-ray analysis indicates the formation of LnVO4, thermal analysis of these solids shows stability of the phase up to 1000 °C. The photocatalytic activity of all these orthovanadates has been investigated by degrading various dyes like methylene blue (MB), Orange G (OG), Rhodamine B (RB), Rhodamine Blue (RBL), and Remazol brilliant blue (RBBR) under UV irradiation. Further, these compounds were also used to degrade organic pollutants like phenol, 2,4-dinitrophenol and 2,4-dichlorophenol. The degradation rates of dyes and organics in presence of microwave-synthesized orthovanadates are higher compared to that observed with orthovanadates synthesized by the solid state technique. The microwave-synthesized orthovandates also show chloro-specificity, with the rate of degradation of 2,4-dichlorophenol significantly higher than that observed in presence of Degussa P-25 titania.