Study On Preparation Of Nano-TiO₂/zeolite Composite Catalysts And Degradation Of Formaldehyde

As a semiconductive and photocatalytic material,nano-TiO₂ has become one of the most widelyused semiconductor material due to its high oxidative capability,physical and chemical stability,nontoxicity and cheapness,which has been used in the field of environmental pollution control.In this paper,nano-TiO₂ was immobilized on the surface of zeolite through liquid phase precipitation method to synthesize the nano-TiO₂/zeolite composite catalysts,which overcame the tendency of aggregation,bad stability and difficult recycle.In addition,Immobilization of TiO₂ could achieve the organic combination of dispersion,adsorption and catalysis.In the preparation of nano-TiO₂/zeolite composite catalysts,the effects of preparation conditions were investigated and sulfate ions were used to modify the photocatalytic activity of composite catalysts.The experimental results indicated that the composite catalysts showed the highest photocatalytic activity at calcination temperature of 600 °C,TiO₂ loading amount of 40%,and the [SO₄^2-]/[Ti4+] molar rate of 1:1,respectively.Compared with pure TiO₂,the photocatalytic activity of composite catalysts was improved to 4.04 times.Furthermore,the relationship between TiO₂ nanoparticles and zeolite was explored,it was found that zeolite could improve the dispersion of nano-TiO₂ particles,reduce the crytal size of nano-TiO₂ and restrain the TiO₂ crystalline phase transformation from anatase phase to rutile phase in some degree.Inaddition,the photocatalytic degradation experiments showed that a synergistic effect existed between zeolite and nano-TiO₂ immobilized on zeolite.A closed type photocatalytic reaction device was designed for exploring the influence factors in the photodegradation process of formaldehyde with composite catalysts,which included the catalyst dosage,light intensity,air humidity and intial concentration of formaldehyde.The experimental results showed that the degradation rate of formaldehyde increased gradually with the increasing of catalysts.The formaldehyde gas not only could be degradated well,but also could reduce power consumption of the photocatalytic reaction device under the irradiation of eight UV lamps.In addition,the degradation of formaldehyde gas reached the highest level when the relative humidity of air was 60% and the initial concentration of formaldehyde gas was 80 ppm.In the study of kinetics,the degradation process of formaldehyde was better fitted by the first-order kinetics equation,which the kinetic equation was ln?C0/Ct?=9.378?10-4t.