The Modified Activated Carbon Fibers On The Adsorption Properties And Mechanism Of Toluene

With the development of petrochemical industry and extensive use of all kinds of organic solvent, the pollution of volatile organic compounds(VOCs) has become social effects of pollution which is harm to human health. Thereinto, the pollution benzene hydrocarbon especially catches human's eyes. So research of characteristic, hazardous mechanism and controlling approach of benzene hydrocarbon has become focus in the field of environmental science and engineering. Therefor, the adsorption perfermance and purify mechanism of toluene adsorbed on modified activated carbon fiber(ACF) were studied. Above all, kinds of domestic and overseas treatments and main characteristic of VOCs were dissertated. The application condition and potential problem of any technology were evaluated. So far, adsorption by porous carbonaceous adsorbent is the most widely applied method. Due to microstructures, fine adsorption properties, high speed of adsorption and desorption , fine electric properties and chemical steady properties, the ACF have been widely used in the environmental protection, electron industry, chemical industry, medical treatment and sanitation, etc. In addition, the structure, adsorption characteristic, applied effect and modified methods were summarized systemically. On the foundation of these, toluene was selected as a adsorbed object was studied.Viscose ACF was selected as adsorbent and adsorption capability for adsorbing toluene was investigated in this experiment. The experiment was divided into three parts: the influence of pretreatments on toluene adsorption behavior on ACF, the influence of ACF modified with nitrate of cerium on the toluene adsorption behavior on ACF ,surface structural investigation and modified mechanism analysis.In the pretreatment experiment, the saturated adsorption amount at relative pressure of toluene from 0 to 1.0 of ACF₀, ACF₁ which is treated by distilled water and ACF2 which is treated by (1 +9) chlorhydric acid were measured; the adsorption isotherms at 25℃and 35℃were measured respectively; the influence of different pretreatments on the adsorption behavior of toluene was reviewed; evaluating the datas with equations of Freundlich and Langmuir. The results showed that toluene adsorption equilibrium amount increased from 16.29% to 53.28% and 14.80% to 33.36%(measured in adsorption equilibrium amount) separately comparing the treated ACF₁ and ACF₂ with untreated ACF₀ ; the toluene adsorption capability was remarkably improved on those ACF treated by (1+9) chlorhydric acid and distilled water compared with untreated ACF as well as they have a much higher toluene adsorption equilibrium amount at 35℃even than untreated ACF at 25℃; the adsorption isotherm approached to I model and tally with Freundlich equation comparatively.In the modification experiment, nitrate of cerium was used to modify ACF. The orthogonal experiment was designed according roasting temperature, roasting time, impregnation concentration and pH of impregnation solution; different modified ACF samples were prepared in different conditions. The isothermal adsorption behavior of toluene on the ACF samples at the relative pressure from 0 to 0.35and 25℃and 35℃,were studied. Results showed that at the relative pressure of 0.0223, the toluene adsorption equilibrium amount separately increased by 23.00% to 53.73% and 17.68% to 52.26%(measured in adsorption equilibrium amount) individually; the toluene adsorption equilibrium amount at 35℃was remarkably higher than that of 25℃in the same conditions, which is predicated the endurance to temperature of ACF was also strengthened. The orthogonal experiment at 25℃and 35℃were analysed separatedly on the foundation of toluene adsorbed capcity on ACF; the influence grade of modified experiment parameter was ascertained; Results showed that roasting temperature was always the most key parameter. Finally the benchmark of filtering the fine sample was fixed on the divided pressure cumulative adsorption amount at 25℃and 35℃; the samples of ACF3321, ACF3132, ACF2132 were chosen as the best samples; so the fine modification conditions were ascertained according to their made conditions. Referring to ACF₀, the adsorption isotherm of three picked samples were tested according to the equations of Langmuir, Freundlich and D-R; the testing effects were all ideal, but the result of D-R equation was better than other two equations; it indicated that at relative pressure of toluene from 0 to 0.3440, any toluene adsorption on ACF was regard as monolayer adsorption.The samples of ACF₀,ACF₃₃₂₁,ACF₃₁₃₂ perfermance were determined by thermal and differential thermal analysis(TGA/DTA) and surface structural parameters detection. Results showed the surface area and pore volume of the picked ACF samples treated by nitrate of cerium were increased compared with ACF₀; this phenomenon of ACF₂₃₁₂ was most evident; the total pores volume was increased by 22% and the DFT pore volume was increased by 22.6%; the average pore radius was broaden largely and with that surface area was also increased by 10.5%. The analysis of pore volume and radius of ACF3321, ACF₃₁₃₂ and ACF₂₁₃₂ showed the microporous radius distribution didn't change significantly; but in the comparison of the range of mesoporous, the porous volume and radius were increased and broaden significantly of ACF₂₃₁₂.