Tetracycline hydrochloride degradation by heterogeneous photocatalysis using TiO2(P25) immobilized in biopolymer (chitosan) under UV irradiation

TiO2(P25) has been widely used to treat wastewater; however, the elimination of TiO2(P25) suspended in the treated water causes running costs and induces secondary pollution, which greatly restricts its practical applications. Consequently, several methods have been implemented to immobilize TiO2(P25) on various substrates. This work deals with the immobilization of TiO2(P25) in chitosan film by using the cross-linking method. The prepared catalyst was characterized using X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), UV-Vis diffuse reflectance spectra (DRS) and scanning electron microscopy (SEM), and its catalytic activity in tetracycline hydrochloride (TC) degradation under UV light was explored. XRD, FTIR, DRS and SEM characterization indicated that TiO2(P25) was successfully immobilized on chitosan film, the chemical structure of TiO2(P25) did not change after the immobilization and the TiO2(P25) was uniformly dispersed in the composite. Chitosan/TiO2(P25) was used for the removal of TC by photocatalysis under UV irradiation. The effects of operational parameters such as amount of TiO2(P25), agitation speed and the initial TC concentration were investigated. An 87% removal efficiency of TC was obtained with 0.12 g of TiO2(P25) and TC removal was significantly enhanced by the agitation of the solution. The TC removal efficiency decreased from 72 to 44% when TC concentration increased from 30 to 40 mg/L after 60 min reaction time, the photocatalytic reactions followed the pseudo-second-order kinetic.