A Study On The Preparation Of Vermicompost Adsorbent And Its Adsorption Characteristics For VOCs

Adsorption method disposes coated VOCs,which is a highly efficient and widely applied process.However,the commonly used activated carbon is expensive and has secondary pollution at present,which leads to unsatisfactory treatment of VOCs in paint shop.Therefore,it is particularly important to explore new adsorbents with low cost and high purification efficiency.Vermicompost is not only cheap and readily available,but also contains a large amount of elemental carbon,organic matter and some aluminosilicate substances.In this paper,we can unceasingly optimize the preparation of Vermicompost adsorbent through different modification methods,discuss the application potential of the modified Vermicompost,and preliminary analyze the mechanism of the purification of VOCs,and optimize the process parameters of adsorbing VOCs in a fixed bed.That has great significance for realizing the utilization of Vermicompost and promoting the treatment process of VOCs in the coating industry.The main conclusions of this paper are as follows:?1?In the method of modifying of Vermicompost with inorganic compound reagents,it is found that Vermicompost has the best adsorption performance after modified by a 1:2volume ratio of ZnCl₂:H₃PO₄.Based on the combination of single factor and multi-factor analysis,the optimal preparation conditions for the inorganic chemical modified Vermicompost adsorbent?ICMV?are determined as follows:the activation temperature is600?,and the mass ratio of Vermicompost and modified reagent is 1:3.Activation time is 2h.The characterization found that the 600-ICMV prepared under this condition has a high specific surface area of up to 160.271 m²/g,which is 26.33 times that of Vermicompost,and the average pore size is 3.3381 nm,which is a highly ordered mesoporous adsorbent.Amorphous amorphous SiO₂ and Al₂O₃ in 600-ICMV increased significantly,making its hardness and adsorption activity enhanced.Because of the small number of non-polar functional groups on the surface of 600-ICMV,there are so few active sites that can participate in the chemical adsorption of VOCs,and the adsorption of hydrophobic VOCs is dominated by van der Waals forces.?2?In the method of modifying of Vermicompost with inorganic-organic chemical composite reagents,it is found that the adsorbent?OICAV?produced by 600-ICMV and chitosan hydrochloride has better adsorption capacity.The best preparation conditions determined by the control variable method are as follows:the concentration of chitosan hydrochloride is 30 g/L,the modification reaction time is 3 h,and the modification reaction temperature is 30?.The characterization revealed that the micropores in the shell-OICAV are filled with chitosan hydrochloride which prepared under best conditions,so its specific surface area is lower than that of 600-ICMV,the value is 61.2387 m²/g,and the average pore size is 15.71111 nm.However,chitosan hydrochloride can be evenly distributed on the surface of aluminosilicates and carbon materials,enhancing the synergistic adsorption effect between them.In addition,without destroying the surface chemical structure of 600-ICMV,chitosan hydrochloride reacts with polar groups to add-CH₂ and-NH hydrophobic groups,and the active sites involved in VOCs chemisorption reactions increase significantly.The adsorption of toluene,ethylbenzene and ethyl acetate is about 1.3 times that of 600-ICMV.?3?In order to explore the application potential of 600-ICMV and shell-OICAV to adsorb VOCs,comparing it with coal-based activated carbon and 5A molecular sieves sold in the market,it was found that the adsorption performance of the modified Vermicompost is far less than that of coal-based activated carbon,but the adsorption capacity of shell-OICAV to toluene is only 14.3 mg/g less than that of the 5A molecular sieve,indicating that the shell-OICAV has superior adsorption performance.?4?Fitting the adsorption isotherms of 600-ICMV and shell-OICAV,it is found that both 600-ICMV and shell-OICAV conformed to Langmuir equation and Freundlich equation.but the Langmuir equation can more accurately describe the adsorption equilibrium relationship between toluene and modified Vermicompost.It shows that modified Vermicompost contains not only the physical adsorption force dominated by van der Waals force,but also the chemisorption force brought by the functional group.?5?The dynamic adsorption process of toluene on a fixed bed with modified Vermicompost is investigated.When the adsorption temperature in the fixed bed is 25?,the inlet flow rate is 600 to 750 L/h,and the addition amount of modified Vermicompost is not less than 9 g.It has better cleaning effect on VOCs with large air volume and low concentration in the paint shop.