Preparation And Properties Of TiO₂/Montmorillonite Composite Photocatalyst

As a typical semiconductor material,TiO₂ has attracted more and more researchers for its organic pollution treatment ability.However,because of the hydrophilicity and the feature of non-recyclable,TiO₂ is limited in the field of pollution control.Thus,the study of mineral-supported TiO₂ has attracted extensive attention.In this paper,the montmorillonite supported TiO₂ was synthesized by three methods?twice hydrothermal treatment method,once hydrothermal treatment method and hydrolytic precipitation method?.At the same time,the structural characteristics and photocatalytic properties were studied.In twice hydrothermal treatment method,ultra-fine dispersion of montmorillonite has been achieved by adjusting the pH value.Thereby synthesizing TiO₂/MMt composite with high crystallinity and large loading content was synthesized.After that,The effects of secondary hydrothermal temperature,time and pH on the structure and properties of the composite photocatalyst were discussed here.XRD result shows that the sample contains a well-crystallized anatase TiO₂ peak.A weak characteristic vibration peak of Si-O-Ti was shown in FT-IR spectroscopy.The microscopic morphology shows uniform loading of TiO₂ on the surface of MMt,visible light and UV light photocatalytic tests have shown relatively good photocatalytic performance.Under the optimal conditions?the secondary hydrothermal temperature is 180oC,hydrothermal time is 6 h,hydrothermal pH value=4 and loading content is 25%?,the photodegradation rate of methyl orange on the TiO₂/MMt composite photocatalyst after 8 hours of visible light irradiation can be reach to 80%.Replaced the twice hydrothermal treatment method as once hydrothermal method.Changed the alkaline adjusting treatment process in hydrothermal condition to room temperature condition.Furthermore,the sandwich TiO₂/MMt was successfully synthesized by controlling the ultrafine dispersion of montmorillonite and the subsequent self-assembly process by a single hydrothermal method that adjusted the pH value twice.Then we have discussed the influence of hydrothermal conditions on the structure and properties of composite photocatalysts and comparing them with samples synthesized with ordinary hydrothermal method.The results of XRD and FT-IR indicate that TiO₂ chemically combined with the MMt layers through hydrothermal action,which hindered the grain growth and phase transformation from anatase to rutile.The micro-morphology results have shown that TiO₂ nanoparticles were successfully embedded on the MMt layers,and the MMt layer spacing was enlarged.Visible and UV photocatalytic tests exhibit excellent performance under optimal conditions?the hydrothermal temperature is 180oC,hydrothermal time is 6 h,hydrothermal pH=3,TiO₂ loading content is 25%?.The degradation rate of methyl orange can reach to 95%with TiO₂/MMT composite photocatalyst after visible light for 8h.This single hydrothermal treatment with twice pH-adjustment method takes full advantage of the dispersive sheet and solves the traditional shortcomings of low resistivity and low mass transfer efficiency of MMt-supported substrates.To have a comparison with the hydrothermal method,the TiO₂/MMt composite photocatalyst was synthesized by hydrolysis precipitation method.XRD result shows that the sample has a miscibility consisit of anatase and rutile.The PL test shows that the optimal sample has a low photoelectron hole recombination rate.The electrochemical behavior test also confirmed this conclusion.The photocatalytic activity test shows that samples synthesized with this method has the best performance.Methyl orange can be degraded to 100%in the 8 h visible light photocatalytic test,which was 5%-20%higher than that of hydrothermal method.