Preparation And Properties Of Modified Semiconductor Photocatalyst

Photocatalytic oxidation technology has a high degradation rate for printing and dyeing wastewater.Early semiconductor photocatalysts have advantages of high stability,environmental protection,non-toxic and harmless,but single photocatalysts also have some problems,such as the low utilization rate of absorbing only part of ultraviolet light to sunlight,photogenic electrons and holes are easy to recombine,thus reducing photocatalytic activity.Therefore,in this paper,a series of composite photocatalysts were prepared by sol-gel method combined with supercritical drying technology with tetrabutyl titanate,zinc acetate dihydrate,ammonium metavanadate and bismuth vanadate as raw materials.XRD,SEM,TEM,UV-Vis and XPS were used to characterize the crystal structure,microstructure and surface valence of the prepared composite materials.Methylene blue was used as simulated wastewater to evaluate the photocatalytic activity of the composite photocatalyst under ultraviolet and visible light.In this study,three different systems of composite materials were explored,and the results are as follows:?1?Ag-Zn O/ATP composite photocatalyst prepared with attapulgite as carrier and zinc acetate dihydrate and silver nitrate as raw materials.Zn O was successfully supported on attapulgite,and Ag existed in the composite material as a single substance,which could produce plasmon resonance effect,making the absorption band edge of the composite material redshift from 410 nm to 425 nm,reducing the band gap energy and improving the response range of the catalyst to light.The optimum Ag load was 3 wt%,the calcination temperature was 400?,the degradation rate of the catalyst was 98.2%after the catalyst was lowered by UV lamp for 3 h.?2?Sm-Ti O₂/MMT composite photocatalyst was prepared withmontmorillonite as carrier,tetrabutyl titanate and samarium nitrate as raw materials.The comparison between natural drying and supercritical drying shows that supercritical drying can overcome the surface tension in pores,keep the gel structure basically unchanged,so that the composite material has good dispersion.A certain amount of Sm doping can inhibit the production of rutile Ti O₂ and the growth of Ti O₂grains.Sm exists in the composite material in the form of Sm₂O₃.Sm²⁺is unstable,and the electrons are easily transferred to the catalyst surface,where they are obtained by O₂ to form·O^2-,which inhibits the recombination of photogenic electrons and holes.The 4f electron transition energy of Sm can reduce the band-gap energy of the composite material,improve the absorption of visible light by the catalyst,easily stimulate the electron transition to generate holes,and improve the photocatalytic activity.The optimum Sm doping amount was 1wt%,the calcination temperature was 500?,and the photocatalytic activity was the highest.?3?Bi VO₄ and Bi VO₄/Ti O₂ composite photocatalysts were prepared by sol-gel method with bismuth nitrate,ammonium metavanadate and Ti O₂?self-made?as raw materials.The prepared Bi VO₄ is monocline scheelite,the p H and calcination temperature will affect the crystal growth of Bi VO₄,the optimal p H value is 7,calcination temperature is 500?;The addition of Ti O₂ will change the morphology of Bi VO₄ and increase its specific surface area to 13.091 m²/g,increasing the surface absorption and improving the capturing ability of photoelectron-hole.The optimal Ti O₂dosage was 30 wt%,and the degradation rate of methylene blue solution under xenon lamp for 3h reached 77.3%.After three times of recycling,the degradation rate still reached 71%.