Preparation Of New Gel Adsorbents And Their Adsorption Properties For Simulated Waste Gas Containing Benzene

Volatile organic compounds(VOCs)are one of the main substances causing air pollution in China,belonging to the precursor of PM2.5.Their photochemical reactions can lead to urban photochemical smog,and their reactions with nitrogen oxides under light conditions also affect the production of ozone,posing great harm to the environment and human health.Therefore,strict control of VOCs is imperative.Adsorption method is a widely used treatment process at present,which has the characteristics of wide applicability and good treatment effect.Among them,the selection of adsorbent is the key to whether the adsorption treatment effect meets the standard.The gel adsorbent is a good adsorption and separation material,but the gel adsorbent synthesized directly from natural materials has high cost and poor hydrophobicity,which can not meet the application needs of adsorption and removal of volatile organic compounds in industry.Therefore,a new gel adsorbent with cheap raw materials,low preparation cost,and certain hydrophobicity was prepared in this paper to adsorb benzene-one of volatile organic compounds,this provides a theoretical basis for the industrial application of the adsorbent.Through demonstration,sodium alginate,agar,and diatomite were selected as the main raw materials,polyethylene glycol as the porogen,and phenyltriethoxysilane as the modifier,through single factor experiments,the optimal raw material ratio of the adsorbent was determined as Sodium alginate:agar:diatomite:polyethylene glycol=6∶6∶10∶3.Through various characterization methods such as scanning electron microscopy,Nitrogen physical desorption test,Fourier transform infrared spectroscopy,X-ray diffraction,thermogravimetric analysis,isoelectric point,contact angle,and iodine and methylene blue adsorption values,it is known that:(1)The pores of this adsorbent come from the diatomaceous earth itself and the effect of the pore forming agent-polyethylene glycol;(2)The average pore diameter of the adsorbent is 4.88 nm,the specific surface area is 74.205 m~2/g,and the pore volume is0.087 m~3/g;(3)The main functional group responsible for adsorption is the phenyl provided by the modifier phenyltriethoxysilane,the maximum adsorption capacity for benzene is 236.2 mg/g;(4)Under weakly alkaline condition with the p H of 7.46,the adsorbent can keep the most stable state;(5)No significant mass loss occurred within the range of 0 to 28.94℃,and all other raw materials will not undergo decomposition or denaturation within the range of 28.94 to 100℃,except for a small amount of water in the adsorbent itself and a small amount of thermal decomposition loss of agar;(6)The average pore size of the adsorbent is 4.88 nm,mesoporous pore volume accounting for 83.9%,and the development of mesopores is higher than that of micropores.The adsorption kinetics of benzene on the gel adsorbent conformed to the linear driving force mass transfer equation;freundlich isotherm equation can better described the adsorption equilibrium of benzene molecules on the gel adsorbent,showed a multi molecular layer adsorption dominated by physical adsorption.Adsorption of benzene by the adsorbent is an exothermic,positive spontaneous and entropy increasing process;the regeneration experiment showed that thermal desorption regeneration is the most economical and feasible regeneration method,which can achieved six cycles of use.