Studies on Synthesis, Characterization, and Photocatalytic Activity of TiO2 and Cr-Doped TiO2 for the Degradation of p-Chlorophenol

TiO2 and Cr-TiO2 nanoparticles (NPs) have been synthesized by the sol-gel method using titanium isopropoxide as the precursor of Titania. The prepared samples were analyzed by employing scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared analyses. Under UV irradiation, the photocatalytic activities of TiO2 and Cr-TiO2 were observed by estimating the % degradation of p-chlorophenol (PCP) as a sample pollutant. The extent of degradation was investigated, varying the catalyst dosage, initial PCP concentration, irradiation time, and solution pH. The experimental results show that efficiency of catalysts initially increases but decreases later on, whereas the % degradation of PCP is the highest at its lowest initial concentration. For TiO2 and Cr-TiO2 NPs at their optimal catalyst dosage of 2.0 g/L, acidic pH, and with UV irradiation for 90 min, the observed % degradation of PCP is 50.23 ± 3.12 and 66.51 ± 2.14%, respectively. Thus, the prepared Cr-TiO2 NPs have enhanced the degradation efficiency of PCP with an irradiation time which is four time less than those reported earlier. From the kinetics analysis, the degradation reaction of PCP is found to follow a pseudo-first-order model and the rate constants are 0.0075 and 0.0122 min-1 for pure TiO2 and Cr-TiO2 NPs, respectively. The present study has further revealed that owing to the lower rate of electron-hole pair recombination, the photocatalytic activity of Cr-TiO2 NPs becomes higher than that of TiO2. Therefore, as viable photocatalytic agents, Cr-TiO2 NPs are suggested to be used also for efficient degradation of other organic pollutants.