Preparation Of N-TiO₂/SiO₂ Photocatalytic Coating And Its Application On The Surface Of Cement-Based Materials

With the rapid development of national economic construction,a large amount of industrial waste gas,wastewater,domestic sewage,and car exhaust are generated in industrial activities,daily life,transportation,and other fields.They are seriously polluting the atmospheric environment and water resources,directly endangering human health.Nano photocatalytic technology become the most advanced environmental purification technology in today’s society due to its advantages such as good photosensitivity,simple reaction conditions,high efficiency,and harmless to the environment and human body.As the most widely used building materials,cement-based materials are not only used as structural materials,but also endowed with more functions.Therefore,the research about combining nano photocatalysts with cement-based materials to prepare photocatalytic cement-based materials with environmental purification functions becomes a hotspot for many domestic and international scholars.In this article,a porous SiO₂loaded N doped nano TiO₂（N-TiO₂/SiO₂）photocatalytic material was prepared using a solvothermal method,and the effect of titanium silicon ratio on its photocatalytic performance under visible light was studied.Then,cement-based photocatalytic coatings and organic photocatalytic coatings were prepared by adding N-TiO₂/SiO₂into cement slurry and organic coatings respectively,their photocatalytic effects and durability were also studied.The main research findings are as follows:（1）Porous SiO₂loaded with N-TiO₂is beneficial for improving dispersion and photocatalytic performance of N-TiO₂.After loading N-TiO₂onto porous SiO₂,the specific surface area increases.As the titanium silicon ratio increases,the specific surface area of N-TiO₂/SiO₂photocatalytic material first increases and then decreases.When the titanium silicon ratio is 10:2,the specific surface area is the largest.SiO₂loaded N-TiO₂is connected through Ti-O-Si bonds,which gives N-TiO₂/SiO₂long-term stability.N-TiO₂/SiO₂has better response to visible light than unmodified TiO₂.（2）Explored the effect of N-TiO₂/SiO₂dosage（5%,10%,15%,and 20%）on the photocatalytic performance and durability of its cement-based photocatalytic coating.The higher content of N-TiO₂/SiO₂,the more exposed nanoparticles on the cement surface.And the more photocatalytic materials that can directly contact air and light,the better the photocatalytic effect of N-TiO₂/SiO₂cement-based coating.The larger the content of N-TiO₂/SiO₂,the better the adhesion between the cement-based photocatalytic coating and the cement test block.Among them,nano SiO₂and TiO₂particles not only synergistically promote the cement hydration process in the cement-based coating,but also react with the hydration product Ca（OH）₂to generate C-S-H.In addition,the moisture absorption of cement-based coatings can be inhibited when the content of N-TiO₂/SiO₂is 5%,10%,and 20%;When its dosage is 20%,the cement-based photocatalytic coating has the best frost resistance.Overall,when the content of N-TiO₂/SiO₂is 20%,the cement-based photocatalytic coating has the best photocatalytic effect and durability.（3）The influence of N-TiO₂/SiO₂content on the photocatalytic performance and durability of silicone acrylic lotion photocatalytic coating was investigated.When the content of N-TiO₂/SiO₂is 3%and 4%,the degradation rate of Rh B by silicon acrylic lotion photocatalytic coating reaches 90.43%and 92.13%respectively.Combined with the influence of the content on the durability of the coating,the optimal content of N-TiO₂/SiO₂in the silicon acrylic lotion photocatalytic coating was determined to be 3%.（4）The influence of coating types（silicone acrylic lotion,acrylic lotion and silicone）on the photocatalytic performance and durability of organic photocatalytic coatings was investigated.The degradation rate of Rh B by acrylic acid and organosilicon photocatalytic coating is higher than that of silicone acrylic lotion photocatalytic coating,reaching 95.97%and 98.33%respectively.The photo catalytic coating of silicone acrylic lotion and acrylic emulsion can form a dense protective film on the surface of cement test blocks;The organic silicon photocatalytic coating cannot form a film,and has the highest water absorption and the worst adhesion.At the same time,the freeze resistance of silicone acrylic lotion and acrylic emulsion photocatalytic coating is better.Taking into account the photocatalytic performance and durability of the coating,the best choice for outdoor practical engineering is acrylic photocatalytic coating.