| With the rapid development of the world economy,the living environment is also deteriorating,and environmental pollution has become a major hidden danger that threatens the survival of human beings.Among all kinds of environmental pollution,organic pollution is the widest and most difficult environmental problem to solve.At present,physical adsorption,chemical oxidation and microbial degradation have some disadvantages,such as low efficiency,narrow application range and complex technology.The photocatalytic degradation technology represented by semiconductor Ti O2 is safe and efficient,in line with the concept of environmental protection in today’s society,and has become a new environmental degradation technology.However,Ti O2 has the disadvantages of large band gap and rapid electron-hole recombination,low quantum efficiency and less than 5%utilization of sunlight.In order to solve the above problems,this topic successively reduced the band gap width and electron-hole recombination speed by doping transition metal ions and depositing noble metals,so as to improve the photocatalytic performance of Ti O2.The main results are as follows:（1）In order to improve the catalytic reaction active sites of Ti O2 and delay the recombination of photogenerated electrons,the transition metal ytterbium ion-doped Yb/Ti O2 tubular photocatalytic composites were prepared by sol-gel method and alkaline hot water method.The rich oxygen vacancies and titanium defects will significantly improve the photocatalytic performance of Ti O2.In the experiment,different doping ion concentrations were set to explore the effect on the photocatalytic performance.Finally,the optimum doping concentration of Yb3+is determined,and the residual rate of organic dye degradation of Yb/Ti O2 tubular photocatalytic materials is as low as 14%,and the photocatalytic reaction rate can reach 7.86×10-3 min-1.The doped Yb3+enters the Ti O2 lattice,induces the Ti O2lattice distortion and produces an intermediate energy level to reduce the band gap width.The experimental results show that Yb3+will restrict the growth of Ti O2 crystal size.However,too high doping concentration of Yb3+will produce too many defect structures,and the redistributed electron-hole structure will reduce the redox ability.（2）Using polymer fiber polyacrylonitrile PAN as sacrificial templates,hollow Ti O2 tube structure was constructed under high temperature ablation,and precious metal ions were reduced to realize the deposition of Au nanoparticles.Then,the effects of different chloroauric acid concentration and tetraethyl silicate fumigation time on the photocatalytic performance of Au/Ti O2/Si O2 materials were studied.The experimental results show that too much chloroauric acid will produce larger Au nanoparticles,which will become new composite sites in Au/Ti O2/Si O2 photocatalytic materials.At the same time,excessive tetraethyl silicate fumigation makes the Si O2 insulating layer thicker and limits the electron transfer rate.Finally,the optimum preparation conditions were determined as follows:the concentration of chloroauric acid was 0.5 mmol/L and the fumigation time was 4 h.The residual rate of Au/Ti O2/Si O2 photocatalytic material for the degradation of organic dyes was as low as 15%,and the photocatalytic reaction rate was as high as 5.14×10-3 min-1.It is found that the introduction of Si O2 components can not only maintain the Ti O2 tubular structure,improve the optical path and photon utilization through multiple scattering,but also limit the size of Ti O2 crystals and inhibit the crystal transformation of Ti O2.Precious metal Au nanoparticles not only act as electron acceptors,but also expand the visible light absorption range through localized surface plasmon resonance.In order to achieve the rapid recovery and reuse of Ti O2-based photocatalytic materials,polymer PVA/PVP was used for loading and immobilization.The polymer gel Ti O2-based composite photocatalytic material was prepared by chemical cross-linking and freeze-drying.The degradation residual rate of rhodamine B was reduced to 10%,and the photocatalytic reaction rate constant was 8.48×10-3 min-1.It still had good photocatalytic activity after three cycles. |
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