Preparation And Properties Of TiO₂ Composites Based On Reversed-phase Microemulsion System

Titanium dioxide（TiO₂）,as a semiconductor photocatalyst,has the benefits of being non-toxic,inexpensive,light resistant,high temperature resistant,reactive,and stable,and has a wide range of applications in environmental treatment,sewage treatment,and other areas.However,during the catalytic reaction,titanium dioxide’s limited dispersion and facile aggregation limit its photocatalytic degradation ability,limiting its application in the breakdown of organic contaminants.To address the aforementioned issues,we created high-performance titanium dioxide photocatalysts by increasing the active sites of titanium dioxide photocatalysis and blocking surface photogenerated electrons and holes.Titanium dioxide’s photocatalytic performance was successfully increased,as were its hydrophobic and bacteriostatic qualities.In this paper,the reverse phase microemulsion method was used to prepare nano-TiO₂,silver nanoparticles and micron-sized calcium carbonate.Among them,in the process of preparing nano-TiO₂,using the reversed-phase microemulsion method can not only realize the size control,but also improve the dispersion of materials to obtain TiO₂ nanoparticles with different sizes and crystal types.To further improve the photocatalytic performance,calcium carbonate was introduced to form micro-nanostructures with rough surfaces.At the same time,improving the hydrophobic performance can extend its lifetime and broaden its application range.For this reason,we modified the material.In the experiment,TiO₂nanoparticles were supported with micron-sized calcium carbonate,and the surface of the composite was grafted with polydimethylsiloxane（PDMS）to improve the dispersion of titanium dioxide and to form micro-nano composite structures.This improved the hydrophobic performance of the composite.Furthermore,silver nanoparticles were loaded on the surface of the above TiO₂-CaCO₃ composite to further enhance its photocatalytic performance and to impart certain antibacterial properties to the composite.The composite was characterized by scanning electron microscopy（SEM）,X-ray energy spectroscopy（EDS）,X-ray diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）,transmission electron microscopy（TEM）and contact angle measurement（CAT）,and the structure and photocatalysis of the material were investigated by ultraviolet visible absorption spectroscopy（UV-Vis）.Specific research topics are as follows:In Chapter 1,the physicochemical properties,photocatalytic mechanism,modification methods and related applications of titanium dioxide are reviewed.The mechanism,classification,influencing factors and application of microemulsion were briefly introduced.In Chapter 2,titanium dioxide nanoparticles were prepared by reversed-phase microemulsion method.Polyoxyethylene octylphenol ether-10（OP-10）and medium-chain n-butanol were selected as surfactants and cosurfactants,cyclohexane as oil phase and pure water as water phase to construct microemulsion system.The quasi-ternary phase diagram of the system was drawn by changing the distribution ratio of each group.TiO₂ precursor Ti（OH）₄ was prepared by hydrolyzing tetrabutyl titanate with water in the micropool.The particle size and crystal type of TiO₂ were controlled by changing the molar ratio of water to surfactant（w value）and roasting temperature.The results showed that the smaller the particle size was,the better the photocatalytic effect was.Anatase type has better effect than rutile and amorphous titanium dioxide.In Chapter 3,nano TiO₂-CaCO₃ composite was prepared by reversed-phase microemulsion method.First,spherical micron scale calcium carbonate was prepared by introducing carbon dioxide into a microemulsion ofOP-10+n-butanol+cyclohexane+CaCl₂ammonia solution.Secondly,the titanium dioxide precursor（Ti（OH）₄）was mixed with calcium carbonate and roasted to support the rough surface of calcium carbonate.Since titania and calcium carbonate have strong surface hydrophilicity,we further modified them by surface grafting with polydimethylsiloxane（PDMS）to make them have certain hydrophobicity.The photocatalytic and contact Angle experiments showed that a composite material with both hydrophobicity and photocatalytic activity was prepared.In Chapter 4,silver nanoparticles were prepared by inverting phase microemulsion system.OP-10,n-butanol,cyclohexane and Ag NO₃ solution were used to prepare microemulsion,and ascorbic acid was used as reducing agent.Silver was loaded on the surface of TiO₂-CaCO₃ composite by impregnation doping.Nano silver is a good bactericidal material,particle size and dispersion are the factors that affect the bactericidal performance.The smaller the particle size and the higher the dispersion,the better the antibacterial performance.For the in-situ reduction method with uncontrollable particle size,the dispersion and bacteriostatic effect of silver nanoparticles can be guaranteed by using the micro-emulsion method with controllable particle size and then loading.The photocatalytic activity of the composite was tested,and the antibacterial performance of the composite was detected by the minimum inhibitory concentration method（MIC）.The composite with both antibacterial effect and photocatalytic performance was obtained.In summary,a new reversed phase microemulsion system was used to prepare TiO₂,calcium carbonate and silver nanoparticles.On this basis,two types of titanium dioxide composites were prepared.The performance test shows that the material has hydrophobic,bacteriostatic and photocatalytic degradation properties.It is expected that it will be used in real life applications such as coatings,plastic films,textiles,etc.The research also provides a new idea and a new method for developing and applying titanium dioxide composite materials that meet specific needs.