Preparation Of PDMS/OTMS-TiO₂ Composite Sponge And Its Photocatalytic Activity

Anatase TiO₂ nanoparticles are widely used in waste water and gas treatment due to their small size,large specific surface area,stable chemical properties and excellent photocatalytic performance.However,there are many problems with direct application,such as serious agglomeration,difficult recycle,and will cause secondary pollution,which serious limits its extensive practical applications.In order to solve these problems,researchers put TiO₂ nanoparticles on the carriers for recycling,among which the PDMS（weather resistant polysiloxane）with strong weatherability has arisen great concern.However,the current studies mainly focused on the membrane morphology of PDMS,and there are few studies on the other morphology.In this study,we focused on the above key issues,and designed a kind of PDMS/TiO₂ sponge composite material which was composed by photocatalysis TiO₂ nanoparticles supported on the surface of polysiloxane sponge.In this paper,by anchoring modified commercial P25 TiO₂ nanoparticles with silane coupling agent tetramethoxyl silane OTMS,PDMS/OTMS-TiO₂ composite sponge was prepared by the double sucrose particle template method,and regulating the distribution of TiO₂ nanoparticles in the composite sponge,then study the photocatalytic degradation preformance of the rhodamine B dye of the composite sponge.First,using cheap and available commercial P25 TiO₂ nanoparticles as raw material,coupling modified by the silane coupling agent OTMS,by changing the addition amount of OTMS,a series of OTMS-TiO₂ nanoparticles with different anchorage density were obtained.Then study the influence of crystal type and photocatalytic performance of these OTMS-TiO₂ nanoparticles.The results showed that OTMS is successfully anchored on the surface of TiO₂ nanoparticles,and the anchoring density has no effect on the crystal structure and photocatalytic properties of TiO₂ nanoparticles.Secondly,by mixing vinyl terminated silicone oil,hydrogen contained silicone oil,OTMS-TiO₂,Karstedt catalyst and template,and then initiate the two-component silicone oil silicon hydrogen addition reaction to obtain cross-linked polysiloxane containing a large number of templates,PDMS/OTMS-TiO₂ composite sponge would obtained afther the template removed by soaking in water.The effects of the types of the template,the ratio of the template,the degree of TiO₂ nanoparticle anchoring and the content of TiO₂ nanoparticles on the structure and morphology of the composite sponge were studied.The analysis showed that the sucrose is the ideal template,by using the 1:1 weight ratio of white granulated sugar and white soft sugar as template,high porosity and high specific surface area PDMS sponge with good mechanical properties can be prepared.TiO₂ nanoparticles has good compatibility of silicone oil after modified by OTMS,and it can be embedded firmly supported on PDMS sponge.The effects of the amount of TiO₂ nanoparticles,OTMS anchor density and template types on the distribution of TiO₂ particles in the sponge were further studied.It is found that TiO₂ nanoparticles exposed on the surface of sponge to form micro-nano structure,and the exposed situation can be tuned by controlling the content of TiO₂ nanoparticles.When the OTMS anchor density reaches a certain value of 0.09 μmol?（m2?TiO₂）-1,TiO₂ particles can achieve good loading in the sponge,it is unlikely to change the morphology structure of composite sponge when continue increasing the OTMS anchoring density.Finally,on the basis of the above work,the rhodamine B dye molecules were selected to evaluate the photocatalytic performance of the PDMS/OTMS-TiO₂ composite sponge.The effects of the sponge pore structure,the OTMS anchor density,the TiO₂ particle content and the thickness of composite sponge on the photocatalytic properties of the composite sponge were studied,respectively.The results showed that the composite sponge prepared with double sucrose particle template has the best photocatalytic performance due to their large pore structure and opening pore structure.The photocatalytic performance become better along with the increasing content of TiO₂ particles in the composite sponge.Composite sponge with thin and high specific surface area has better photocatalytic performance.The reuse ability,the photocatalytic performance comparison of the composite sponge and its corresponding composite membrane,and the dye degradation properties under sunlight were further evaluated.The results showed that the composite sponge has good reusability,and has better photocatalytic properties compared to the composite film,and also showed excellent fluorescent dye degradation performance,which has good practical application value.This paper focuses on the construction of three-dimensional structure of composite sponge,by constructing high connectivity,high specific surface area and high light absorptivity PDMS/OTMS-TiO₂ composite sponge,and improve the nudity degree of TiO₂ nanoparticles,the utilization of UV light and effective contact with organic matter,to finally improve the photocatalytic properties of the composite materials.The design and development of PDMS/OTMS-TiO₂ composite sponge has the advantages of simple preparation process,controllable morphology,good photocatalytic performance,and so on.Which is helpful to promote the industrialization usage of TiO₂ photocatalytic composite materials.