Study On Green Preparation And Photocatalytic Properties Of Porous Hierarchical Heterojunction TiO₂ And Its Composites

Antibiotics are widely used in preventing and treating bacterial infections owing to their excellent efficacy.The usage is huge and increasing year by year.However,antibiotics will produce a large amount of wastewater in the production process.And it is difficult to be completely absorbed by people and animals.A large number of antibiotics are discharged into the water environment,which causes serious harm to human health and the ecological environment.Conventional treatment methods do not have an efficient effect on it,so it is highly urgent to explore effective treatment technologies for removing antibiotics from wastewater.Photocatalytic technology is consideres to be one of the effective treatments to remove antibiotics owing to its great degradation effect,high degradation efficiency,friendliness and low price.The key to this treatment is the research and development of photocatalysts with high activity and high stability.Among the semiconductor materials,TiO₂ is considered to be the most potential photocatalyst in solving antibiotic pollution owing to its advantages.It has been widely studied by researchers and has made great progress.However,the easy recombination of charge carriers and the narrow light absorption range are two important factors that limit further application in industry.Numerous studies have shown that heterophase/heterojunction construction can effectively solve these two problems.However,reported preparation methods of TiO₂ heterophase/heterojunction also face many challenges.Most of the traditional synthesis methods have common problems such as complicated procedures,numerous preparation steps,use of strong acids and bases organic solvents,and high calcination temperature,which bring great pressure to the environment and increase the economic cost of synthesis.Therefore,it is urgent to reduce the use of harmful chemicals and find new green preparation methods.In this thesis,we adopted the Deep Eutectic Solvent（DES）method for the green and controllable preparation of catalyst phase junctions and heterojunctions.A series of novel TiO₂heterophase/heterojunction with high activity and easy preparation were developed by tailoring the structure and properties of deep eutectic solvents.The main innovative work and achievements are as follows:（1）A green synthesis strategy of tremella-like porous hierarchical TiO₂（B）/anatase phase junction was achieved by using the designed DES choline chloride/urea/lactic acid as a solvent,inhibitor,soft template and polymorph inducer.The method is mild,efficient,and environmental friendly.It does not need to add strong acid or alkali regulators,and does not require high calcination temperature.The photocatalytic degradation of common antibiotics in water by the synthesized TiO₂ was investigated.The results showed that the photocatalytic degradation performance of the catalyst was much better than commercial P25 TiO₂,and it also had excellent degradation effect on many antibiotics,including Ciprofloxacin and Chloramphenicol.（2）The morphology of the TiO₂（B）/anatase phase junction was controlled by adjusting the structure of the DES.This further increases the specific surface area of the catalyst and provides more active sites for degradation,thus enhancing the photocatalytic activity.The antibiotic degradation experiments showed that the catalyst can not only degrade a variety of antibiotics,but also has excellent catalytic degradation effect on the refractory antibiotic tetracycline.（3）The green preparation of TiO₂ composite and its photocatalytic properties were further explored on the basis of previous studies.By combining with Ce O₂ to construct a heterojunction,it not only promoted the efficient separation of electron holes,but also broadened the spectral absorption.The high efficient degradation of antibiotics under simulated sunlight was realized.This deep eutectic solvent-based synthesis method has the advantages of simplicity,efficiency,environmental protection and low price.It not only overcomes the problem of relying on organic solvents,templates and inhibitors in traditional synthesis methods,but also simplifies the synthesis steps.The green and controllable preparation of photocatalyst has been realized,which has a broad application prospect in the synthesis of nanomaterials.The research content of this thesis will provide a green,mild and controllable method for the synthesis of nanomaterials,and also provide a new way for the batch preparation of nano-catalysts.