Experimental And Predictive Study On Adsorption Of Typical Gaseous Pollutants In Indoor Environment By Activated Carbon

Indoor organic gaseous pollutants(VOCs)represented by toluene and acetone are a serious threat to people’s health,and activated carbon adsorption filters are the most important equipment to remove VOCs pollutants.The concentration of VOCs in the real environment is only at the ppb level,but most of the experimental research on the filter is carried out at a high concentration,which cannot truly reflect its adsorption performance in the actual environment.However,testing the filter directly at low concentration has high time cost and economic cost.Therefore,the prediction model of filter penetration curve under low concentration was established in this study.Firstly,the breakthrough curves of toluene and acetone adsorbed by two coconut shell activated carbons with different structural characteristics were tested on a small experimental platform,and the breakthrough curves were fitted by Langmuir,Freundlich and Dubinin-Radushkevich adsorption isotherm models.According to the fitting results of adsorption isotherms and the theory of mass transfer kinetics,the mechanism of gasphase adsorption of activated carbon at low concentration and the effect of pore structure on its adsorption were analyzed.It is found that under low-concentration conditions,the mass transfer flux of adsorbate gas to the surface of activated carbon particles was reduced,and the driving force to pass through the interface layer and pores was weakened.The gas molecules cannot contact the micropores because they cannot overcome the resistance of diffusion in the pores,so the adsorption of micropores is lost.On the contrary,activated carbon with larger mesoporous pore volume has stronger adsorption capacity.Next,the prediction model of low concentration gas phase adsorption of activated carbon was established.The adsorption process of non-polar substances such as toluene is suitable to be predicted by Yoon-Nelson and WheelerJonas models.The equilibrium adsorption capacity in Freundlich adsorption model and the mass transfer coefficient in Yoon Nelson mass transfer model are substituted into the modified Wheeler Jonas equation to establish a new mass transfer prediction model.The predicted values of the model are in good agreement with the experimental values,still maintain high accuracy under low concentration conditions,and are suitable for activated carbon with different structures.Polar substances such as acetone have a weak affinity for the adsorption site,and the adsorption rate is determined by the physical reaction rate on the active site.It is more suitable to use the Thomas model that emphasizes that the adsorption rate is controlled by the surface reaction of the adsorbate and the adsorption site to predict the adsorption process.In most experiments,the effects of structural characteristics of activated carbon,types of surface chemical functional groups,types and concentrations of organic gaseous pollutants and adsorption conditions on the adsorption properties of activated carbon are often studied.However,there are few experiments on the effect of solid pollutants on the adsorption of gaseous pollutants by activated carbon.Therefore,in order to fill this gap,the effect of ultrafine particles on gas phase adsorption of activated carbon was studied from three dimensions: adsorption concentration,adsorbent species and structural characteristics of activated carbon.Finally,the adsorption data obtained were compared with the pure gas phase adsorption data,the effect of ultrafine particles on the gas phase adsorption capacity of activated carbon was analyzed quantitatively,and the adsorption characteristics of gas phase,gas-solid two-phase media on activated carbon were compared.