Investigation on Photocatalytic Activity of Perovskite ZnTiO3 and CdTiO3 Nanocrystals for Degradation of Crystal Violet and Congo Red Pollutants under Sunlight

Perovskite nanocrystals of ZnTiO3 and CdTiO3 with the cubic and orthorhombic structures were synthesized using the hydrothermal method. The crystal structures confirmed by XRD, morphology and particle size, chemical composition, and surface chemical features of samples synthesized are evaluated through, Fe-SEM, TEM, EDX , FT-IR, and BET analyzes. The average crystallites size ZnTiO3 and CdTiO3 perovskite were determined 12.03 and 43.7 nm, respectively by Debye Scherer’s relationship.The Optical and photocatalytic properties of ZnTiO3 and CdTiO3 are investigated by DRS (Differential reflectance spectroscopy) and UV-Vis analysis, respectively. The Ebg value (band gap energy) of the perovskites was obtained using Tauc plots. The cubic ZnTiO3 showed Ebg=3.11 eV against the CdTiO3 with Ebg=3.39 eV. The photocatalytic activities of perovskite ZnTiO3 and CdTiO3 nanocrystals were evaluated for degradation Congo red (CR) and Crystal violet (CV) pollutants. The ZnTiO3 degraded both the CR and CV dyes with high efficiency (91% and 72%) compared with CdTiO3 perovskite (51% and 9.7%) under 60 min of the sunlight irradiation. This high performance is affected by factors such as narrowing of the Ebg, the larger surface area, smaller crystal size and the existence of the hierarchical porous in the structure of the ZnTiO3 than CdTiO3. The kinetics studies revealed the rate constant of photodegradation of CR anionic dye by both of the perovskite as-synthesized is greater than degradation of cationic CV. The decomposition of the crystal violet fits the pseudo-first-order kinetic, while the degradation of the CR follows both the pseudo-first-order and the pseudo-second-order kinetic according to R2> 0.9.