Study On Adsorption-photocatalytic Oxidation Of Formaldehyde By Tio₂ Loaded On Activated Carbon

With the development of economy and the improvement of housing conditions,the pollution source and pollution diversify gradually,especially contamination of the building and fitment,so it is very necessary to study the purification technology of formaldehyde in indoor air.At present,it is the best method to oxidize the pollutants,like formaldehyde,into carbon dioxide and water.Loading catalyst on carrier has many advantages,such as selectivity well,contamination few and easy to be recycled.In recent years,the TiO₂ photo-catalysis technology is the purification technology with potential development.In this paper,the photo-catalysis technology and the traditional activated carbon adsorption technology were combined,in addition,the formaldehyde adsorption and degradation by the TiO₂ loaded on activated carbon was studied.TiO₂ photo-catalyst,the preparation of TiO₂ loaded on activated carbon and their effects on formaldehyde adsorption and degradation have been studied systemically,taking formaldehyde as the study object.Taking TiCl₄ as the raw material,the TiO₂ powder was prepared by the method of TiCl₄ hydrolyzation.And TiO₂ loaded on activated carbon was also prepared making use of activated carbon as carrier.The preparation condition of TiO₂ powder has been reviewed emphatically,including hydrolysis temperature,(NH₄)₂SO₄ addition amount and calcination temperature.The effects of TiCl₄ volume and calcination temperature on formaldehyde degradation capacity of TiO₂ loaded on activated carbon have also been studied.It was found that,with the increase of hydrolysis temperature,the formaldehyde degradation capacity of TiO₂ powder rose firstly,then reduced gradually,and lastly almost stabilized.The experimental results showed that the formaldehyde degradation capacity of TiO₂ powder prepared when the hydrolysis temperature was at 70℃,the rate of[Ti/SO₄^2-]was 1:2,was up to 7.78 mg·g^-1 from a 600 mg·L^-1 formaldehyde solution.With the increase of TiCl₄ solution volume and calcination temperature,the formaldehyde adsorption capacity of TiO₂ loaded on activated carbon had the same rule,also rose firstly,then reduced gradually, and lastly almost stabilized.And the formaldehyde adsorption capacity of TiO₂ loaded on activated carbon prepared when the hydrolysis temperature was at 70℃,the rate of[Ti/SO₄^2-] was 1:2,the TiCl₄ solution volume was 5mL,calcined at 400℃for 2h,was up to 10.18mg·g^-1 from a 600 mg·L^-1 formaldehyde solution,which was 6.06 times of activated carbon. In order to study the mechanism of formaldehyde adsorption of TiO₂ loaded on activated carbon,some characterization technologies such as SEM and XRD were used for the TiO₂ powder obtained under different conditions,SEM can be used for studying microcosmic shape and structure of TiO₂ powder,while XRD can be used for testing crystal structure,phase content of TiO₂ powder and calculating the TiO₂ particle dimension.IR was employed for activated carbon and TiO₂ loaded on activated carbon to observe the change of function groups before and after formaldehyde adsorption.The results of SEM and XRD showed that,after adding(NH₄)₂SO₄,the TiO₂ particle dimension was reduced efficiently and the phase transition temperature from anatase style to rutile style was increased.The TiO₂ powder was unshaped prepared when the hydrolysis temperature was at 70℃,the rate of[Ti/SO₄^2-]was 1:2, without calcinations,but after calcining at 400℃for 2h,it was changed into pure anatase style; The results of IR showed that,in the process of adsorbing formaldehyde,chemisorption occurred on the surface of activated carbon,formaldehyde was oxidized into carbon dioxide and water under the TiO₂ photo-catalysis,and the part which has not been oxidized was adsorbed on activated carbon temporarily.