Study On Preparation And Properties Of The Molecular Imprinting TiO₂ Photocatalytic Film

Nano TiO₂ powder photocatalysts possess some defects when they applied to the photocatalytic degradation of organic pollutants, such as spreading difficultly, easy to aggregate and lose photocatalytic activity, and difficult to reuse, etc. The TiO₂ have poor selectivity when they are used in the Multi-component contaminative waters, those low or non-toxic organic compounds of high concentration are always firstly degraded, while the highly toxic organic pollutants of low concentration is not effectively dealt with. In order to overcome these shortcomings of TiO₂ photocatalysts, TiO₂ photocatalysts immobilization and modification have become attractive.In this thesis, we use the method of liquid phase deposition, through adding P-25 to the deposition solution as crystallization revulsant, to synthesize TiO₂ photocatalytic films on the substrates after deposition several hours in 50℃. Considering the molecular imprinting polymers can selectively recognize the template molecules, we add salicylic acid to the deposition solution as template molecules for preparing the TiO₂ film which have some certain selectivity to the template on the substrate by using the method of liquid phase deposition. We optimize conditions during the deposition, such as the concentration of the deposition solution; deposition temperature; deposition time and the concentration of the template molecules.To evaluate the performance of the molecular imprinting TiO₂ photocatalytic films (MIF), we take the template molecules salicylic acid as the target pollutants, using the MIF to degrade 25 mg/L salicylic acid solution, setting the non-molecular imprinting photocatalytic films (NIF) as the control experiment. The concentrations of the salicylic acid solution after degradation are detected by the UV-visible spectrophotometer, the velocity constant of the salicylic acid degraded by the MIF is 0.005 min-1, and it's 100% faster than that of the NIF. The experiment results show that the molecular imprinting TiO₂ photocatalytic films have very good photocatalytic activity and molecular recognition capability. When we choose the benzoic acid as the interferences in the mixture solution, the concentrations of salicylic acid and benzoic acid in the mixture solution after degradation are detected by the HPLC. The velocity constant of the salicylic acid in the mixture solution degraded by the MIF is 0.00519 min-1, the select factor is 2.57. These results show that the molecular imprinting TiO₂ photocatalytic films can degrade the target pollutants firstly; through repeating the experiments several times it proves that the molecular imprinting TiO₂ photocatalytic films have good reproducibility and regeneration capacity.