Fabrication Of Activated Carbon Fibers And Their Performance On Adsorption Of Volatile Organic Compounds And CO₂

With the development of industrialization,factories emit lots of toxic and harmful gas pollutants,causing serious harm to the ecological environme nt and climate and affecting human survival and development.Problems such as photochemical smog and the greenhouse effect have attracted worldwide attention.There are many treatment technologies for these gas pollutants.Among them,the adsorption technology has many advantages of simplicity,high efficiency,low cost and no secondary pollution,which has good application prospects in the removal of volatile organic pollutants and CO₂ for the recovery and reuse.However,the problem of adsorption technology is mainly the choice of adsorption materials.Activated carbon fibers?ACFs?is a type of widely used adsorption material,which is inexpensive,stable in performance and high in adsorption efficiency,and is a suitable adsorption material for practical industrial applications.In this paper,the traditional activated carbon fibers have poor mechanical strength,low-microporosity,and poor adsorption performance for target pollutants.By adjusting the activation process,the ACFs with high-strength and being suitable for adsorbing different gas pollutants are prepared,which provides a theoretical reference for the activation process of ACFs.The main research contents and results are as follows:?1?In this work,phenolic fiber was used as the raw material and copper chloride was used as the activator.During the activation process,ACFs with different pore structures were prepared by adjusting the ratio of copper chloride to the raw materials.XRD and Raman characterization found that the prepared ACFs were all amorphous carbon without obvious graphitization.SEM and TEM characterization found that most of ACFs were complete and less fractured,indicating that the activation of copper chloride was relatively mild.Specific surface area and pore size distribution tests showed that ACFs contained a large number of micropores.The ACF-8 sample prepared by maximum dose copper chloride activation could be observed apparently a certain amount of mesopores.But its microporosity can still reach more than 90%.At the same time,its specific surface area was also the largest.The tensile fracture test found that ACFs had good mechanical strength and could reach 2-3 times than that of commercial ACFs.It also further confirms that copper chloride is a milder activator,FT-IR characterization find that the ACFs surface has not obvious functional groups,indicating that copper chloride activation is mainly caused by erosion and pore formation on the fibers surface.?2?The prepared ACFs were subjected to dynamic adsorption test of toluene and ethyl acetate,and the sample with the best adsorption performance was selected for the static pressure swing adsorption experiment of toluene.The dynamic adsorption test showed that with the increase of the activation dose,the breakthrough time for the adsorption of toluene and ethyl acetate increases,namely the adsorption performance for VOCs increases.The ACF-8 sample prepared by highest proportion of copper chloride had the best adsorption performance.The excelent adsorption performance was mainly related to the amount of micropores contained in it.Toluene static pressure swing adsorption was performed for the toluene adsorption equilibrium isotherms and adsorption kinetics.The adsorption isotherms of ACF-8 for toluene followed to the Freundlich isotherms model shows that the adsorption of toluene is coexistence of single-layer adsorption and multi-layer adsorption,Adsorption kinetics analysis has a higher model relationship with pseudo-first-order kinetics,indicating that the external mass transfer of toluene molecules on the ACFs during adsorption showed greater effect of the adsorption rate than the internal diffusion function.?3?CO₂ adsorption test was performed on the prepared ACFs.Through static pressure swing adsorption at different temperatures,the CO₂ adsorption amount at different temperatures corresponding to different pressure points was obtained.The CO₂ adsorption performance at25°C and 0.15 bar is more concerned because it is closer to the actual flue gases condition.The ACF-0.1 sample with the lowest copper chloride dose showed the most excelent CO₂adsorption capacity under this condition,which can reach 1.04 mmol/g.It was found through the correlation analysis of pore volume and adsorption capacity,the ultra-micropores were the key to dominate its CO₂ adsorption performance.At the same time,ACF-0.1 also had the highest adsorption isosteric heat and CO₂ adsorption selectivity.Through the dynamic CO₂/N₂mixed gas adsorption test to further prove its high efficiency in CO₂/N₂ adsorption selectivity.In addition,the adsorption-desorption cycle test found that after multiple cycles ACF-0.1 can still maintain a substantially constant adsorption performance,which indicated it had a good stability and regeneration.