Preparation Of Ag@AgBr/ZnO And Its Photocatalytic Oxidation Performance

Nowadays,the components of organic polluted wastewater are becoming more and more complex,which aggravates the deterioration of the water environment.Traditional sewage treatment methods are difficult to withstand the increasing demand for sewage treatment.Photocatalytic oxidation technology using only light energy as an energy source has gradually entered the field of scientific research because of its advantages of green,high efficiency and no secondary pollution.As a traditional high-efficiency semiconductor photocatalyst,ZnO has excellent optical properties.At the same time,ZnO has a common problem of photocatalysts:excessive dependence on ultraviolet light and electron-hole pair recombination was fast.In order to solve the above problems,this study used hydrothermal method to prepare ZnO photocatalyst and optimize its preparation process.At the same time,the Ag@AgBr system was introduced to modify the ZnO material.The degradation efficiency of rhodamine B?RhB?solution was used as an evaluation index of photocatalytic activity.Finally,cefuroxime sodium solution was used as simulated antibiotic wastewater to evaluate the practical application value of Ag@AgBr/ZnO new photocatalyst.Firstly,ZnO photocatalytic materials were prepared by hydrothermal method using zinc acetate as the main raw material and cetyltrimethylammonium bromide?CTAB?as the surfactant.The results of single factor and orthogonal experiments show that the optimal preparation parameters of ZnO materials were:hydrothermal temperature 140°C,hydrothermal time 3 h,CTAB dosage 2 g,calcination temperature 650°C and calcination time2 h.The photocatalytic performance of the prepared ZnO material was the highest,and the degradation efficiency of RhB solution reached 99%after 90 min of UV illumination.Characterization and analysis of ZnO materials by scanning electron microscopy?SEM?,high resolution transmission electron microscopy?TEM?,X-ray diffraction?XRD?and X-ray photoelectron spectroscopy?XPS?.The results showed that the ZnO material obtained under the optimal preparation conditions exhibits a flower-like morphology composed of porous sheets;it was a hexagonal wurtzite structure with high crystallinity and purity;it has a strong response to light in the ultraviolet range with a band gap of about 3.22 eV.Secondly,a simple one-step hydrothermal method was used to prepare Ag@AgBr/ZnO composite photocatalytic materials and optimize the composite ratio.Characterization and analysis of Ag@AgBr/ZnO materials by SEM,XRD,TEM,XPS,Fourier transform infrared spectroscopy?FTIR?,Raman spectroscopy?Raman?and UV-vis diffuse reflectance spectroscopy?UV-vis DRS?and photoluminescence spectroscopy?PL?.The results showed that the Ag@AgBr/ZnO-2 composites exhibit similar micro-morphological features to ZnO materials,which were flower-like morphology composed of porous sheets;The crystallinity and purity were higher;compared with ZnO,the Ag@AgBr/ZnO-2 composite exhibits stronger absorption in the visible light band,and the band gap was about 3.16 eV;the recombination rate of electron-hole pairs was lower than ZnO materials.Under visible light irradiation,Ag@AgBr/ZnO-2 composites showed stronger photocatalytic activity than P25 and ZnO materials.The degradation rate constant was 10.14 times that of P25 and 11.08 times that of ZnO.Finally,Ag@AgBr/ZnO composites were used to degrade cefuroxime sodium as simulated antibiotic wastewater,and degradation experiments under different light sources.After 60 minutes of UV irradiation,the degradation rate of cefuroxime sodium solution reached 88.13%.After 60 minutes of visible light irradiation,the degradation rate of cefuroxime sodium solution reached 35.08%.After 30 min of simulated sunlight,the degradation rate of cefuroxime sodium solution was reached 74.77%.According to the results of free radical masking experiments,combined with theoretical calculations,a possible photocatalytic reaction mechanism was proposed.The results show that·OH plays a leading role in the photocatalytic process of Ag@AgBr/ZnO composites,followed by h⁺,and·O₂^-has a weak effect on the photocatalytic process.The single-factor experiment was used to optimize the treatment conditions of cefuroxime sodium solution:the dosage of catalyst was 1 g/L;the initial pH of cefuroxime sodium solution was 11;the optimal initial concentration of cefuroxime sodium solution was 5 mg/L.Under these conditions,the degradation rate of cefuroxime sodium solution was up to 90.96%after 30 min of Ag@AgBr/ZnO composite.