Study On Preparation And Bactericidal Properties Of Chitosan Composite Modified Titanium Tioxide Nano Coating Material

With the"toilet revolution"in full swing,the sanitation level and environmental quality of rural areas in China have been significantly improved.However,our country’s rural social and economic foundation is relatively weak,and the construction of harmless sanitary toilets is particularly lagging behind.Rural toilets are still dominated by dry toilets,and the pathogenic microorganism pollution caused by traditional dry toilets seriously threatens the health of rural residents.At present,at home and abroad,the photocatalytic suspension or photocatalyst precursor is coated on the surface of building materials,and after high-temperature heat treatment,a layer of photocatalytic film is formed on the surface to achieve the effect of sterilization and disinfection.However,the process technology is complicated,It is not easy to operate,and is only suitable for high temperature resistant materials such as ceramics and glass,and is difficult to be widely used in diversified rural toilet environments.This article aims to develop photocatalytic organic coatings that can be coated on the surface of various facilities to make them suitable for a variety of carriers,reduce economic investment and technical complexity,and expand the scope of application of sterilization materials in rural toilet building materials.In this paper,the most widely used inorganic antibacterial material titanium dioxide（TiO₂）and the only natural alkaline polysaccharide chitosan（CTS）with great application potential are selected as the research objects.Firstly,TiO₂ was modified by silver doping to prepare Ag-TiO₂ photocatalytic bactericidal material with bactericidal effect under visible light.Then use the CTS as the substrate to load Ag-TiO₂ on the inside and surface of the CTS to form a uniformly dispersed and smooth Ag-TiO₂/CTS nano-composite sterilization coating material.The structural properties and bactericidal properties of the materials are systematically explored;ceramic tiles coated with bactericidal materials are placed in the toilet to explore the stability of their bactericidal performance in the actual application environment.The main results are as follows:（1）Ag-TiO₂ photocatalytic composites were prepared by sol-gel method.They were characterized by X-ray diffraction（XRD）,scanning electron microscope（SEM）,transmission electron microscope（TEM）,X-ray photoelectron spectroscopy（XPS）and ultraviolet and visible diffuse reflectance spectrum（UV-Vis DRS）.The crystal form,morphology,ionic valence and optical properties of the materials were characterized and analyzed.The results show that this study successfully prepared the anatase phase Ag-TiO₂,the particle size is between 10-20nm,irregular spherical,and Ag exists in Ag-TiO₂in the form of zero valence.Compared with TiO₂,the absorption of Ag-TiO₂ in the visible light region is significantly enhanced,and its visible light absorption performance is effectively improved,which is beneficial to the photocatalytic sterilization process.（2）XRD,SEM,fourier transform infrared spectroscopy（FTIR）,atomic force microscop（AFM）and thermogravimetric（TG）characterization were used to analyze the morphology,thickness,surface roughness and thermal properties of the material.The results show that the addition of nano Ag-TiO₂ interferes with the original arrangement of the CTS polymer chain.The two form an Ag-TiO₂/CTS nano composite coating film through a strong interaction,and the Ag-TiO₂ is uniformly dispersed in the composite coating film.And surface.At the same time,the appropriate amount of Ag-TiO₂ can reduce the height and surface compactness of the composite film.When the concentration of Ag-TiO₂ is 3%,the height of the composite film is 120nm,and the Ra and Rq Lower,7.23nm and 10.8nm,respectively.Compared with CTS,the composite coating film containing Ag-TiO₂ has higher thermal stability,and with the increase of Ag-TiO₂addition,the composite coating film shows a higher decomposition temperature.（3）Single factor experiments were used to explore the sterilization performance of Ag-TiO₂ and Ag-TiO₂/CTS under different conditions.The results show that the best silver doping amount of Ag-TiO₂ is 1%,the best calcination temperature is 450℃,and the best addition amount of Ag-TiO₂ in the composite coating is 3%.When the dosage is0.20g/L and the light intensity is 1000W,both Ag-TiO₂ and Ag-TiO₂/CTS can show excellent sterilization efficiency.For the initial concentration of 106CFU/m L E.coli,the sterilization rate reaches 99.9999%in 1 hour..Under weak light intensity and no light conditions,the Ag-TiO₂/CTS composite coating film can always maintain a sterilization efficiency of 99.8991%,while the sterilization efficiency of Ag-TiO₂ is greatly affected by the light intensity,which is only 77.9495%.The sterilization efficiency of the Ag-TiO₂/CTS composite coating film after four cycles of use can still reach 99.6988%.The XRD and SEM images after the cycle also show that the composite coating film has good stability.（4）The bactericidal properties of the prepared bactericidal materials Ag-TiO₂ and Ag-TiO₂/CTS nanocomposite coatings in natural toilets were investigated.The results showed that Ag-TiO₂/CTS had more stable germicidal efficacy than Ag-TiO₂ in different positions of toilets,and the initial bacteria amount on the ceramic tile loaded with Ag-TiO₂ was also less.Continuous experiments at the same site also showed that the bactericidal effect of Ag-TiO₂/CTS composite coating was more stable and efficient than that of Ag-TiO₂,less susceptible to the influence of external environment,and had more lasting bactericidal effect.The results showed that Ag-TiO₂/CTS composite coating bactericidal material was more conducive to significantly reduce the microbial community richness in the toilet,which showed more excellent bactericidal performance in the two dimensions of biomass and microbial community composition.By comparing the microbial communities at the genus level,Acinetobacter with the highest abundance,as one of the important opportunistic pathogens causing bacterial infection,accounted for a significantly lower proportion in the microbial community of Ag-TiO₂/CTS group,indicating that Ag-TiO₂/CTS not only has broad-spectrum bactericidal performance,but also has specific bactericidal effect on some pathogenic bacteria,which further improves the efficiency of rural toilet Health and safety guarantee of the Institute.