Preparation Of Hydrotalcite-based Composite Materials And Research On Its Photocatalytic Performance

In order to develop a new type of visible light response catalyst,hydrotalcite / silver silicate composite was prepared with hydrotalcite as the carrier.It was analyzed by XRD,SEM,TG and so on.Methylene blue was used to evaluate photocatalytic efficiency as a target pollutant,and its photocatalytic degradation mechanism was discussed in this paper.The main contents of the research are as follows:(1)The Mg-Al LDHs with the mole ratio 2:1 was prepared by hydrothermal method,and the AgSiOx/Mg-Al LDHs composites was prepared by chemical deposition method with the Mg-Al LDHs as carrier.The structure,composition and morphology of the composite were characterized and analyzed by X ray powder diffractometer(XRD),thermal analyser(TG),scanning electron microscope(SEM),X ray photoelectron spectroscopy(XPS)and transmission electron microscopy(TEM).The crystallization of Mg-Al LDHs was observed by adjusting the crystallization reaction time.Xenon lamp was used to simulate sunlight to degrade methylene blue(MB).The photocatalytic efficiency of the composites was studied by adjusting the loading ratio of the Mg-Al LDHs and silver silicate(AgSiOx).The results show that the composites was combined and formed heterojunction,which effectively improves the dispersion of silver silicate particles and solves the problem of easy agglomeration.It facilitates the migration of photo generated hole pairs,and increases the contact area between AgSiOx catalyst and target contaminants.When the concentration of methylene blue is 40mg/L with the volume 100 mL.the sample AgSiOx/Mg-Al LDHs(5:1)has the best photocatalytic effectand the degradation rate of MB reaches 99% within 30 min.Under the same reaction conditions,the photocatalytic reaction rate is 1.53 times of the pure AgSiOx.(2)In order to explore the effect of hydrotalcite species on photocatalytic performance,Ni/Al,Zn/Al hydrotalcites with the mole ratio of 2:1 were prepared.The structure,morphology and thermal stability were characterized by XRD,TG and SEM.The results show that in the three kinds of Mg/Al,Ni/Al and Zn/Al hydrotalcite,the thermal stability is Mg-Al LDHs>Ni-Al LDHs>Zn-Al LDHs.In the photodegradation methylene blue experiment,the photocatalytic efficiency is AgSiOx/Zn-Al LDHs(5:1)>AgSiOx/Ni-Al LDHs(5:1)>AgSiOx/Mg-Al LDHs(5:1)(3)In order to study the effect of different morphologies of Hydrotalcite on photocatalytic efficiency,in the action of anionic surfaceactive agent(SDS),the flower like Mg-Al LDHs material was prepared by hydrothermal method,and the AgSiOx/Mg-Al LDHs composites was prepared.The results showed that AgSiOx/Mg-Al LDHs(5:1)(flower like)had the best photocatalytic effect.The degradation efficiency of MB(40mg/L)is 99% in 30 min,and the degradation rate of methylene blue MB is 1.83 times of pure AgSiOx.That is,the flower like structure is conducive to the increase of photocatalytic activity.The hydrotalcite(LDHs)applied in the fields of photocatalysis has a good practical and research significance.