Study On Adsorption And Decomposition Mechanism Of Nano-TiO₂ Loaded By Activated Carbon And Doped By Metal Ion

With the development of economy and the advancement of science and technology,people's quality of life is continuously improving,and the influence of indoor air quality on people's quality of life and health is increasing.Formaldehyde is the primary pollutant of indoor air.Because of its characteristics of wide source,long duration,and large harm,how to remove formaldehyde with efficient and convenient method has become a hot topci in current research.There are various ways to remove formaldehyde.Among them,nano-TiO₂ photocatalytic oxidation technology is recognized as the most effective and promising method.However,nano-TiO₂ photocatalytic oxidation technology also has some drawbacks.In this paper,nano-TiO₂ photocatalytic oxidation technology is optimized by means of activated carbon loading and Fe3+ doping to improve the photocatalytic oxidation performance.In this paper,nano-TiO₂ was prepared by sol-gel method,loaded by activated carbon and doped Fe3+.The prepared samples were characterized by scanning electron microscopy?SEM?,X-ray diffraction analysis?XRD?,N2 adsorption-desorption?BET,BJH?and other instruments,and the nano-TiO₂ loading was measured.The conclusions are as follows: The prepared nano-TiO₂ has a size between 5 and 15 nm,and is uniformly loaded in the activated carbon.The doping of Fe3+ can promote the transformation of anatase crystals,lower the transition temperature?500??,and can also delay the growth of nano-TiO₂ size.The specific surface area of the sample rises first and then decreases with increasing temperature.The determined composition ratio at the time of preparation determines the loading of nano-TiO₂ in the activated carbon and is not affected by the heat treatment temperature.In this paper,using formaldehyde as the target,the effect of different factors on the removal efficiency of formaldehyde was investigated through the single-factor experiments and orthogonal experiments of formaldehyde removal by nano-TiO₂ photocatalytic oxidant loaded activated carbon and doped Fe3+.Through repeated experiments,the effect of usingtimes on the removal efficiency of formaldehyde was explored.Finally it is the analysis of the dynamics.The conclusions are as follows: Through the results of single-factor experiments,it is known that 500?is the best heat treatment temperature,and the nano-TiO₂ has an anatase-type crystal structure and complete growth and development.0.5% is the optimal Fe3+ doping amount.At the low concentration of formaldehyde,it has the best effect,almost reaching 100%,and the speed is very fast.At this point,the adsorption of activated carbon and nnano-TiO₂ dioxide dominates.15w/m2 is the best light intensity.Excessive light intensity may make the desorption capacity on activated carbon and nano-TiO₂ greater than the adsorption capacity,and the degradation rate of formaldehyde decreases.Through orthogonal experiments,we can see that the primary order of factors affecting the effect of photocatalytic decomposition of formaldehyde on by nano-TiO₂ photocatalytic oxidant catalysts loaded activated carbon and doped Fe3+ are: initial concentration of formaldehyde> heat treatment temperature> light intensity> doping amount of Fe3+ > reaction time.Through repeated experiments,the results show that,with the increase in the number of useing,the effect of nano-TiO₂ photocatalytic oxidant catalysts loaded activated carbon and doped Fe3+ has a slight reduction,but the degree of reduction is not great.The removal rate of formaldehyde can still be close to 90% after five 6hour-cycles.The dynamics model is established and the fitted curve shows that it basically conformed to the apparent first-order dynamics equation.the catalytic oxidation rate constant K = 0.58,and the adsorption rate constant k0=56.5.