| Volatile organic gases?VOCs?such as formaldehyde and toluene are the main components of indoor air pollutants and pose a serious threat to human health.As a method of effectively removing VOCs,photocatalytic degradation technology has attracted wide attention because of its high catalytic efficiency,cleanliness and no pollution.Many scholars have found that the incorporation of photocatalytic materials into traditional architectural interior wall coatings can effectively remove indoor VOCs.However,when photocatalytic materials such as Ti O2 are used alone,there are problems such as low utilization of visible light and poor photocatalytic efficiency.At present,most of the organic components in commonly used wall coatings are silicone-acrylic emulsion and styrene-acrylic emulsion.Such coatings often release VOCs themselves during use,and when combined with photocatalytic components such as Ti O2,the organic matter in the coating will facing the risk of being degraded.In addition,the commonly used coatings have a dense structure,and only the surface can achieve catalytic purification,making it difficult to give full play to the overall photocatalytic performance of the coating.In order to improve the catalytic activity and spectral response range of the photocatalyst,Bi VO4 and graphene oxide were used to modify Ti O2,and the best performance graphene-Bi VO4-Ti O2?Gr-Bi VO4-Ti O2?composite catalyst was selected based on the photocatalytic activity;Treatment of waste shells by calcination,shell powder with loose structure and interconnected pores can be obtained,and combined with Gr-Bi VO4-Ti O2 to prepare porous photocatalytic coatings with ultraviolet-visible light photocatalytic performance.The main research contents and conclusions are as follows:?1?Using the hydrothermal synthesis method,the influence of hydrothermal temperature and hydrothermal time on the catalytic performance of Bi VO4 was studied.It was concluded that under the preparation conditions of 180?and 10h,Bi VO4 with better catalytic performance was obtained,and the removal rate of 100ml 10mg/L Rh B was 49%within 3h;using Bi VO4 modified Ti O2,the effect of the amount of Ti O2 added on the catalytic performance of Bi VO4-Ti O2 was investigated,and it was concluded that when the Ti O2addition ratio was 23.6%,Bi VO4-Ti O2with better catalytic performance was obtained,the removal rate of 100ml 10mg/L Rh B was 65%within 3h,SEM pictures shows that the added Ti O2 is uniformly attached to the Bi VO4 particles,which is beneficial to the improvement of the catalytic performance of Bi VO4-Ti O2;Using graphene oxide modified Bi VO4-Ti O2,the effect of the content of graphene oxide on the catalytic performance of Gr-Bi VO4-Ti O2composite catalyst was investigated.It was concluded that when the content of graphene oxide was 3%,Gr-Bi VO4-Ti O2 composite catalyst with higher UV-visible photocatalytic performance was obtained,the removal rate of 100ml 10mg/L Rh B is 100%within 2h,SEM pictures shows that Bi VO4-Ti O2particles are uniformly attached and grown on lamellar graphene,and there is no cross overlap between graphene;FTIR analysis found that there are no chemical bonds between Bi VO4 and Ti O2,graphene,just simple physical adsorption,and there is a chemical bond between Ti O2 and graphene,forming a Ti-O-C bond,and combined with electrochemical analysis,it can be seen that Bi VO4,the synergy between Ti O2 and Gr accelerates the migration of photogenerated electrons and holes,effectively avoids the recombination of the two,and thus improves the photocatalytic performance of the Gr-Bi VO4-Ti O2 composite catalyst.?2?The waste scallop shell was calcined,and the effects of calcination temperature and calcination time on the composition,structure,morphology,specific surface area and pore size distribution of the shell were analyzed.The results show that:Ca CO3 begins to decompose at 600?,and decomposes completely at 800?,and its decomposition reaction rate is maximum at 774?;As the calcination temperature increases,the calcination time prolongs,and SEM pictures show that the shell powder particles gradually formed a loose porous structure from the initial layered structure,and finally evolved into a plate-like structure;The best optimized treatment condition is calcination treatment at 800?for 1h,and the specific surface area of shell powder obtained under this condition was the largest,3.52m2/g;SEM pictures show that the shell powder particles are loose and porous,and there are many nano-level interconnected pores,the average pore size is 18.6nm.?3?Determine the distribution ratio of each group in the coating,mix each component evenly according to the preparation process,and mix with a certain proportion of deionized water to prepare a shell powder-based photocatalytic environmental protection coating.The degradation efficiency of formaldehyde gas by the coating was investigated,and it was found that after the coating was exposed to light for 6 hours,the removal rate of formaldehyde gas with a concentration of 1.666mg/m3 by the coating was 10.7%;After 5 cycles of degradation of formaldehyde gas,it was found that the stability and durability of the paint to degrade VOCs was well;In addition,after a series of basic performance tests of coatings,it is known that the test results of shell powder-based photocatalytic environmentally friendly coatings meet the national standards. |
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