Preparation And Photocatalytic Properties Of Polyimide/Inorganic Nanocomposite Films

Polyimide/inorganic nanocomposite films were prepared by ion exchange and in situ deposition,the structure and appearance were characterized by XRD、SEM、EDS、XPS、FTIR and XRF.The photocatalytic activity of the composite films was evaluated by the degradation rate of methylene blue.The results show that:（1）ZnO-Co₃O₄/PI composite films were prepared by ion exchange method.Ion exchange method was successfully applied to the surface of PI,which was loaded with six side wurtzite ZnO and cubic phase Co₃O₄.When the mole fraction of Co was30%,the time of ion exchange was 1.5 hours,the sintered temperature was 460℃,sintered time was 2 hours.The degradation rate of methylene blue was 98%.（2）Co₃O₄-Ag/PI composite films were prepared by ion exchange method.Calcination at elevated temperature resulted in the reduction of Ag⁺to Ag and oxidation of Co²⁺to Co₃O₄ as well as an uniformly dispersion of the metal/oxides on the PI surface.The best content of Ag⁺is 60%,and the temperature is 270℃,showed a degradation rate of methylene blue of 94%in 2 hours.In the five-cycle tests,the degradation rate of methylene blue remained at about 94%,indicating a good stability of the Co₃O₄-Ag/PI composite films.（3）Ion exchange method was used to prepare ZnO-Ag-CeO₂/PI by doping three kinds of ions Zn,Ag and Ce onto polyimide surface.Compared with ZnO/PIand ZnO-Ag/PI,the Zn O-Ag-CeO₂/PIshow higher photocatalytic activity.When the ion exchange time was 1.5h,the ratio of three ions was 7:10:3,the total ion concentration was 0.3mol/L and the calcination temperature was 390℃for 3h,the degradation rate was 96.6%.After 5 times of degradation,the composite membrane still has high photocatalytic activity,A variety of organic pollutants can be degraded by composite films.（4）PI/ZnO composite films were prepared by in situ deposition method.The addition of the chelating agent allows the Zn O particles to be more uniformly dispersed in the PI film,and the photocatalytic activity of PI/ZnO composite film doped with citric acid is greatly improved compared with PI/ZnO composite film without citric acid.When the citric acid and zinc nitrate molar ratio was 2:1,calcined to 350℃for 2 hours,the degradation rate of methylene blue was 97.7%in 2 hours.