| Photocatalytic technology,as a kind of advanced water treatment method that can be completely degraded and cleaned,has been favored by many scholars.Among many photocatalysts,zinc oxide semiconductor materials have attracted much attention due to their high abundance,low price,easy synthesis,controllable morphology,high thermal stability and non-toxicity.However,ZnO has a wide band gap and low utilization of solar energy.Second,it is easy to produce defects and structural instability,resulting in lower optical stability.Also,nano-powder is not easy to recycle.These three problems greatly limit the industrial application of ZnO.Therefore,obtaining supported ZnO photocatalyst with a simple process,high photocatalytic activity and good photostability is an effective strategy to solve these problems.In this paper,the morphology of ZnO was controlled by adding surfactant citric acid,and TiO2/ZnO binary photocatalyst was prepared by compounding with TiO2.TiO2/ZnO/CQDs ternary composite photocatalyst was prepared by using the unique chemical stability of carbon quantum dots(CQDs)and TiO2/ZnO binary material.TiO2/ZnO@PC composite photocatalyst was prepared by using porous ceramic as carrier.The phase structure,microstructure,photocatalytic activity and photocatalytic stability of the products obtained by different processes were systematically studied.The main contents and conclusions of this paper are as follows:(1)Spherical ZnO particles were prepared by hydrothermal method using zinc acetate and hexamethylenetetramine as raw materials.The effect of the percentage of citric acid on the morphology and catalytic performance of ZnO was studied,and characterized by XRD,SEM and photocatalytic degradation experiments.The results showed that when the content of citric acid is 20%,ZnO with uniform morphology,good dispersion,complete crystal growth and the best photocatalytic performance can be obtained.the photocatalytic degradation rate of ZnO is 94.3%within 90 min.Secondly,the TiO2/ZnO composites were prepared by two steps of hydrothermal method and sol-gel method.The effects of the percentage of TiO2 on the phase,morphology and catalytic performance of TiO2/ZnO were studied.The results showed that when the content of TiO2 was 4%,the cauliflower like and the best catalytic TiO2/ZnO were obtained,and the photocatalytic degradation rate was 96.0%in 90 min.(2)Graphite CQDs with 3-5 nm and 0.22 nm interplanar spacing were synthesized by hydrothermal method using citric acid as carbon source.The effects of hydrothermal temperature and time on the fluorescence properties of CQDs were studied.The results showed that when the hydrothermal time was 4 h and the hydrothermal temperature was 220℃,the fluorescence properties of CQDs were the best.The ternary composite of CQDs with ZnO and TiO2 materials showed that when the addition amount of CQDs was 1 mL,the photocatalytic performance of CQDs was the best,and the photocatalytic degradation rate was 96.7%within 90 min.After five cycles of degradation experiments,the degradation rate remained 80.2%,indicating that the addition of CQDs improved the photocatalytic stability of ZnO photocatalyst.(3)TiO2/ZnO@PC was prepared by hydrothermal method.The effects of hydrothermal times,hydrothermal time and the percentage of sodium carboxymethyl cellulose on the photocatalytic performance of TiO2/ZnO@PC were studied.The results showed that TiO2/ZnO@PC had the best catalytic performance when the hydrothermal number was 1 mL,and the photocatalytic degradation rate was 96.3%within 90 min.The hydrothermal time will affect the surface morphology of the catalyst.The longer the hydrothermal time is,the better the catalytic performance of the catalyst is.When the hydrothermal time is 10 h,the performance of the catalyst is the best,and the photocatalytic degradation rate is 96.9%within 90 min.Sodium carboxymethyl cellulose is a thickening agent,which causes the decrease of catalytic performance of TiO2/ZnO@PC,and the more the content,the more obvious the decrease of catalytic performance. |
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