Research On The Preparation And Adsorption Performance Of Lignin Based Activated Carbon Fibers

Carbonfibers is a kind of new carbon adsorbent and received much attentions. At present, the production of carbonfibers mainly using the viscose, pitch or polyacrylonitrile as the raw materials, which has poor renewable and high cost. When using the alkaline lignin as the raw materials to prepare the activated carbon fibers not only solve the problem of poor renewable and high cost, but also provide the new thoughts for the biomass recycling.This paper used the powdery alkaline lignin as raw materials to produce protofibers by electrospinning. Then we set the protofibers undergoing stabilization, carbonization and activation treatment to preparing the activated carbon fibers. By the way of controlling the weather factor(air humidity) and raw material proportions in the process of electrospinning, and obtained that the summer fine day (RH=50%-60%)and the proportion of alkaline lignin:acetic acid:10wt%PVA is 70:15:15 could pepare the better character protofibers, and the spinnability of the spinning solution is best at the conditions. In the process of stabilization and carbon-ization we studied the stabilization time and carbonization temperature effect. The experiments find that the longer time of stabilization, the more oxygen-containing functional groups the carbonfibers possessed, and when the temperature of carbonization come to 800?,we obtained a kind of activated carbon fibers possessing the optimum BET specific surface area and maximum adsorption capacity for toluene. Besides, we investigated the effect of water vapor activation method, KOH activation method, metal impregnation and in-situ filling catalyst carbonization activation methods on the prepared activated carbon fibers'physicochemical properties and adsorption property. The results indicated that all the three activation methods make various improvement to the activated carbon fibers on the respects of physicochemical property and the toluene adsorption capacity. Above these three activation methods, the activated carbon fibers ACFK adsorbent prepared from KOH activation possessed the optimal adsorption properties.At the same time, the adsorption experiment selected toluene, methanol and acetone three typical VOCs as the research object, and selected ACFK as the adsorbent mainly consist of static and dynamic conditions, which carried out in the static adsorption bottle and fixed bed adsorption device, respectively. The static state experiment indicated that the equilibrium adsorption capacity smaller with the increase of temperature, and the higer the concentration of VOCs, the higher the equilibrium adsorption capacity in the vapour environment. While the three VOCs components exists at the same time in the adsorption bottle, the equilibrium adsorption capacity of three kinds of VOCs both decreased, but the superposition value is bigger than any one component adsorption capacity. In the three components adsorption test, the toluene adsorption capacity is the biggest. In the static liquid conditions, the adsorption capacity of three kinds of VOCs simultaneously varying degrees decreased compared with gas phase VOCs adsorption. Among the three VOCs, the effect of adsorption capacity on toluene is biggest, decreased more than 50%. But in the liquid phase, the toluene adsorption velocity is the fatest, and the equilibrium adsorption capacity is also biggest. Using the adsorption kinetics and adsorption isotherms to analyse ACFK adsorptions for VOCs at the static between the liquid phase and gas phase. In the liquid condition, ACFK adsorption for toluene accorded great with the pseudo-second adsorption kinetics model, ACFK adsorption for methanol accorded great with Werber-Morris adsorption kinetics model, and the adsorption for acetone have great fitting correlation with the Pseudo-first adsorption kinetic model; At the gas phase of static conditions, the adsorption isotherms of toluene and methanol have great correlation with Freundich model, and the adsorption isotherm for acetone using Langmuir model receive better degree of fitting.The dynamic adsorption for VOCs consists of single-component, two-components and three-components adsorption experiments. In the single-component we select the toluene as the representative to study the effect of the concentration, gas flow rate and adsorbent mass on the saturation adsorption capacity. The results indicated that with the increasing of toluene concentration, the breakthrough curves move left, saturation adsorption capacity and the adsorption efficiency of ACFK rose fisrt and then fell. And with the increase of gas flow rate and adsorbent mass, the adsorption efficiency increased; In the two-component adsorption experiments, the combination of methonal with toluene and acetone both existed a obvious competitive adsorption between methanol and toluene as well as methonal and acetone. The peak concentration value of methanol in the exit gas of these two groups respectively are 1.05 and 1.09 times to import concentrations, and the competitive adsorption phenomenon is more obvious in the process of multicomponent adsorption experiment. Besides, these three kinds of VOCs saturation adsorption capacity in two-and multi-components both decreased compared with single-component adsorption.Furthermore, we also studied the effects of water vapor on ACFK adsorption for VOCs. The saturation adsorption capacity of ACFK adsorption for water vapor increased with the rose of relative humidity. In the dynamic adsorption process, the saturation condition happened at 45 min. With the increasing of adsorption temperature, the water vapor saturation adsorption capacity first increase and then decreased, which the peak value of saturation adsorption occurred at 35?; While the water vapour exists in the VOCs mixture gases, the effect degree of saturation adsorption capacity for VOCs by ACFK are toluene> acetone>mathanol in sequence. But with the increasing of amount of water vapor bubbled into mixture gases means RH value increases, the effect degree for VOCs adsorbed by ACFK are toluene>methanol> acetone in sequence.