Preparation Of Silica Matrix Composites And Their Adsorption/Photocatalytic Performances For Dyes

In this paper,silica hollow sphere with rough surface was used as carrier,ZnO,MgO and ZIF-8 were loaded on its surface by different methods.The composition,structure and morphology of the samples were characterized by different characterization methods such as XRD,SEM,TEM,TG,FT-IR.The prepared ZnO/SiO₂,MgO/SiO₂ and ZIF-8/SiO₂ composites were applied to the adsorption/photocatalytic removal of typical dyes in water.The effects of different samples,different solution components and different light sources on the adsorption/photocatalytic properties were investigated.The main contents of this paper are as follows:?1?A series of ZnO/SiO₂ composites were prepared by impregnation method.The effects of different amount of Zn on the ZnO content,structure and surface morphology of the ZnO/SiO₂ composites were investigated,and the adsorption properties of the Congo red in water were also investigated.The adsorption kinetics and thermodynamic model of Congo red on ZnO/SiO₂ composites were studied,and the effects of pH,temperature and the amount of adsorbent on the adsorption properties of Congo red?CR?were studied.The results show that when the temperature is 30^oC,the maximum adsorption capacity of Congo red on ZnO/SiO₂-1samples is 83 mg/g.The adsorption process accords with the poseudo-second-order kinetic model and the Langmuir isotherm model.In addition,the ZnO/SiO₂ composite sample can be regenerated after calcination,and the adsorption capacity of Congo red can be maintained at 83%of the original adsorption amount after three times of regeneration.?2?A series of MgO/SiO₂ composites were prepared by one-step method,and the results show that the composites have high specific surface area and rough surface morphology.The effects of different amount of Mg on the MgO content,structure and surface morphology of MgO/SiO₂ composites and the adsorption properties of Congo red?CR?were investigated.The influence of different ultrasonic dispersion time on the equilibrium time of adsorption kinetics and the effect of different pH on the adsorption performance of Congo red were further studied.The results show that the equilibrium adsorption capacity of Congo red on 20%MgO/SiO₂ samples is up to4000 mg/g,and the adsorption process of the samples accord with the Langmuir isothermal adsorption model.In addition,the samples of MgO/SiO₂ can be regenerated after calcination,and the adsorption capacity of Congo red remains unchanged after five cycles of adsorption.?3?ZIF-8 modified SiO₂ composites were successfully prepared by in situ growth method.The effects of different content of Zn on the ZIF-8 content,structure and morphology of composites were investigated,and ZIF-8/SiO₂ was used to study the adsorption and photocatalytic degradation of methylene blue.The effects of different materials,different light sources,different dye compositions and pH values on the photocatalytic performance were studied,and the reaction mechanism of photocatalytic degradation of dyes was studied.The results show that the degradation rate of methylene blue?MB?by ZIF-8/ZnO-2/SiO₂ in visible light system was over99%within 30 min.Compared with the catalytic degradation performance of ZIF-8/ZnO/SiO₂ composites under pure ultraviolet light,it was found that the photocatalytic degradation efficiency of the composites was higher than that of the composites under pure UV light.In addition,the ZIF-8/ZnO/SiO₂ composite had good stability and reusability,and after four times of photocatalytic reaction,the photocatalytic degradation of Methylene blue was still good.Through the characterization of the materials,it was found that the composition,structure and morphology of the composites did not change significantly before and after the photocatalytic reaction,and the ZIF-8/ZnO/SiO₂ showed good stability.