Adsorption Mechanism And Process Of VOCs On Modified Sepiolite

In recent years,the dust-haze weather occurs frequently in China.It was found that VOCs is an important factor in the formation process of dust-haze.Therefore,the removal of VOCs is imperative.Adsorption method is one of the most widely used methods in treatment of VOCs.However,the conventional adsorbent(activated carbon)has the disadvantage of high cost,secondary pollution and so on.Sepiolite has drew people attention due to its low price,large storage capacity and potential specific surface area,and has a good application prospect in the field of VOCs pollution control.To get the adsorption mechanism and process of typical VOCs on sepiolite,in this manuscript the static adsorption experiment of acetone and toluene on sepiolite modified by hydrothermal and hydrochloric acid was investigated firstly,the surface morphology,pore structure and crystal type of the sepiolite were characterized by scanning electron microscope,automatic surface area and pore size distribution analyzer and X-ray diffractometer,the effects of modification on the properties of sepiolite and the static adsorption performance were discussed.Then,sepiolite was shaped and the effects of adsorption conditions of temperatures,inlet concentration,carrier gas flow and sorbent loading on dynamic adsorption behavior of acetone and toluene on the shaping sepiolite were investigated.Finally,the adsorption equilibrium,kinetics and the adsorption mechanism of VOCs on sepiolite were discussed.The main conclusions were as follows:The static adsorption capacity is larger,when sepiolite is modified by 13% mass fraction hydrochloric acid with 12 h,up to 57.20 mg/g for acetone and 36.92 mg/g for toluene,respectively.After modification,the BET specific surface area increases from 6.218 m2/g to 62.205 m2/g,total pore volume increases from 0.0140 cm3/g to 0.2103 cm3/g,pore size distributes around 1.4 nm and more micropore and mesopore appear.With the increase of BET specific surface area of sepiolite,the adsorption capacity of acetone increases;with the increase of total pore volume of sepiolite,the adsorption capacity of toluene increases,and both show linear relationship.The adsorption quilibrium data of sepiolite is found to better fit to the Langmuir model,and the adsorption process is a monolayer adsorption process with mainly physical adsorption and easy to carry out.The adsorption kinetics follows the pseudo-second order equation for the adsorbent,the adsorption mechanism depends on the nature of the adsorbent and adsorbate itselfs,and the adsorption process is also accompanied by chemical adsorption phenomena.Intra-particle diffusion studies reveal that the adsorption rates were not solely controlled by the diffusion step.