Study On Preparation And Properties Of Zinc Oxide@Alumina Hybrid Structure And Its Photocatalytic Performance

At present,the rapid development of the world economy has produced a large number of pollutants,making environmental problems more serious.Photocatalytic degradation has attracted widespread attention as a mild,low-cost treatment method.ZnO is widely used in the field of photocatalysis research due to its low toxicity,high photosensitivity,and low cost.As a common adsorbent,alumina has the advantages of easy operation and wide application.In this paper,ZnO@Al2O3 hybrid structure was synthesized by low-temperature combustion and hydrothermal methods,respectively,for photocatalytic degradation of organic matter.Investigate the combined mechanism of ZnO photocatalytic performance and Al2O3 adsorption performance to optimize the degradation of pollutants.And the effects of doping different transition metal ions on the photocatalytic performance of ZnO@Al2O3 hybrid structure were studied.The main results are as follows:(1)ZnO@Al2O3 hybrid structure was prepared by low-temperature combustion method combined with subsequent high-temperature calcination,and the photocatalytic performance of the sample was characterized by the degradation of methyl orange solution.Samples with different component contents and firing temperature were prepared.It was found that when n(Zn):n(Al)=2:1 and the roasting temperature was 600?,the sample prepared had the best effect.In addition,when pH=5.91,showing weak acidity,the catalytic performance is optimal.At the same time,by adding different inhibitors,the catalytic mechanism of the sample was studied,and it was determined that the active species of the sample was mainly superoxide radical(·O2-).The sample cycle degradation test shows that it still maintains a high degradation rate and good stability after multiple cycles.(2)ZnO@Al2O3 hybrid structure was prepared by a low-temperature combustion method,and the effects of metal ion doping on the photocatalytic performance of the ZnO@Al2O3 hybrid structure were studied by doping several transition metal ions of Cu,Co,Mn,and Cr.After doping with manganese ions,the photocatalytic activity of the sample is improved compared with the pure sample.After many cycles of degradation experiments,the sample has good stability and repeatability.The addition of copper,cobalt and chromium ions reduced the photocatalytic activity of the sample.And with the increase of roasting temperature,no matter what kind of ion-doped ZnO@Al2O3 hybrid structure,the degradation effect of methyl orange is getting worse.(3)ZnO@Al2O3 hybrid structure with controlled morphology and high purity was synthesized by hydrothermal method and used for photocatalytic degradation of methyl orange.When the zinc/aluminum atomic ratio is 1:1 and the firing temperature is 500?,the sample has many defects,many effective traps for electrons or holes,large specific surface area,and the sample has the highest photocatalytic activity.High degradation rate is maintained after multiple cycles of degradation.The addition of anthraquinone,sodium oxalate,and isopropanol as capture agents for different free radicals confirmed that superoxide radicals(·O2-)were the main active speciess of the sample.