Study Of The Preparation Of Ti-fac Composite Photocatalyst And Its Photocatalytic Activity

Suspended pure nano-TiO₂photocatalysts has a high activity, but it tend to reunite in the use process,and its recycling is very difficult. Study on Modification of titanium dioxide photocatalyst has a broadmeaning. In this study, the hydrothermal method, AB liquid method and sol-gel method was used for thepreparation of titanium dioxide photocatalyst, and the carriers are activated carbon from coal and coconutshell. Composite photocatalysts, enable to be separated from water by external magnetic field, wereprepared by hydrothermal-sol impregnation method, which was composed of two steps: Firstly, Mn-Znferrite was supported on activated carbon（AC） by hydrothermal reaction to form soft magnetic activatedcarbon（FAC）. Then, FAC was impregnated with titanium sol, and soft magnetic composite photocatalystsTi-FAC were produced after calcination. Effects of preparation parameters on the photodegradation ofmethylene blue（MB） were investigated and the crystalline structure, morphology and magnetic propertiesof the photocatalysts were characterized by XRD,SEM and VSM..The results show that:（1） The activated carbon supported titanium dioxide composite photocatalystcan be prepared by hydrothermal method, directly sol-gel method and A liquid B liquid sol-gel method. Allthese composite photocatalysts have a higher activity than the same amount of pure titanium dioxide,though the activities are different from each other, as the different preparation methods. The titaniumdioxide loaded on activated carbon was anatase, its grain is very small, nanoscale, and evenly distributed.（2） The structure of carrier has a marked impact on the composite photocatalyst’s activity. Coconutshell activated carbon has more abundant pore volume and greater specific surface area, so it shows betteradsorption effect, and it promote the photocatalytic degradation process.（3） In the preparation of composite, photocatalysts calcined has a significant effect on its activity. Calcination or increasing the number of calcination can play a role in reaming the activated carbon carrier,thereby enhancing the activity of the overall composite photocatalyst. With the increasing of calcinationtemperature, the carrier reaming is more obvious, the anatase type of titanium dioxide loaded on activatedcarbon is more complete, and the composite photocatalyst’s photocatalytic activity is better. And theappropriate calcination temperature does not change the crystalline form of titanium dioxide.（4） Increasing in the amount of titanium dioxide loading on the composite photocatalyst within acertain range can increase the photocatalytic active sites, and the photocatalytic activity also will increase.But if the amount of TiO₂is too high, agglomeration will appears, and it will reduce the photocatalyticefficiency. On the other hand, the excessive TiO₂will plug the holes of the activated carbon,and theadsorption properties of activated carbon will also been reduced, this will reduce the overallphotodegradation rate. The pore volume and pore structure of the carrier are closely linked to this relativeloading amount.（5） Composite photocatalyst’s photocatalytic activity can be significantly improved by addinghydrogen peroxide in the photocatalytic degradation system. The strong alkaline condition is in favour ofthe adsorption of Methylene Blue on the particle surface of the composite photocatalyst. With theimprovement of the initial concentration of Methylene Blue solution, on the surface, the removal rate ofMethylene Blue is reduced, but the absolute amount of removal of methylene blue is increased actually.The increasing of the amount of composite photocatalyst may accelerate the removal speed of MethyleneBlue solution.（6） Composite photocatalysts, enable to be separated from water by external magnetic field, wereprepared by hydrothermal-sol impregnation method. The sample shows excellent soft magnetic propertiesand high stability, feasible to be completely recovered by an external magnetic field and keeping high photodegradation efficiency after6reuse cycles.The innovation of this paper is that the Mn-Zn ferrite was used in the composite photocatalyst, whichnot only take advantage the strong adsorption properties of activated carbon to promote thephotodegradation, but also use the soft magnetic properties of Mn-Zn ferrite to promote solid-liquidseparation, and this is very beneficial to the separation, recycling and reuse of the composite photocatalyst.The study in this paper has a deep theoretical significance and application prospect, which is veryimportant to environmental protection and it is sure to bring social and economical benefits to us.