A Study On The Preparation Of Biomass-Based Active Carbon Fibers And Their Vocs Adsorption Properties

Volatile organic compounds (VOCs), derived from a variety of sources, were difficult to control and hazardous to human and their environment. The 13th Five-Year Plan pointed out that VOCs would be included in the air pollution total emissions control. VOCs treatment study was a profound research for human health and the social sustainable development. Adsorption enrichment technology was an effective way of recycling high-valued VOCs. At present, to improve the adsorption capacity and to enhance the renewable performance of adsorption materials had become an important research field. The biomass based activated carbon fibers which came from biomass fibers were prepared by chemical activation. The as-prepared biomass based activated carbon fibers were employed for the adsorption of medium or low concentrated chloric or benzenoid VOCs and presented superior adsorption performance and regenerability. The main research content was as follows:1. Kapok based activated carbon fiber (Kapok-450) was prepared at 450 ? in inert atmosphere using NaOH and ZnCl2 as chemical activator. In addition, the hollow sisal based activated carbon fiber (SACFs-20%-450), jute based activated carbon fiber (JACFs-20%-450), hemp based activated carbon fiber (HACFs-20%-450) and cotton based activated carbon fiber (CACFs-20%-450) were prepared using ZnCl2 as the activating agent. The yield of Kapok-450, SACFs-20%-450, JACFs-20%-450, HACFs-20%-450 and CACFs-20%-450 were 28.66%,40.10%,38.57%,31.33% and 38.57%, respectively.2. The as-prepared kapok based activated carbon fiber was characterized by scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), Raman spectroscopy and N2 adsorption-desorption. The characterization results showed that Kapok-450 was composed of amorphous carbon with abundant micropores and specific surface area reached 1397 m2/g. Besides, the adsorption behaviors of Kapok-450 for dichloromethane, benzene and toluene at 30? were evaluated. The evaluation results suggested that the adsorption capacity for dichloromethane, benzene and toluene was 130 mg/g, 350 mg/g and 479 mg/g, respectively, which were calculated from the adsorption breakthrough curves. Furthermore, the regenerability and the influence of adsorption temperatures on the adsorption breakthrough curves of dichloromethane over Kapok-450 were examined. It was found that the adsorption capacity decreased with the increase of adsorption temperature. The adsorption capacity of dichloromethane was up to 179 mg/g at the low temperature of 20?.3. The adsorption performances of hollow SACFs-20%-450, JACFs-20%-450, HACFs-20%-450 and CACFs-20%-450 were investigated in fix-bed. The results showed that the saturated adsorption capacities of dichloromethane over the as-prepared SACFs-20%-450, JACFs-20%-450, HACFs-20%-450 and CACFs-20%-450 were up to 126 mg/g,113 mg/g,129 mg/g and 126 mg/g, respectively, which were higher than that of the commercial activated carbon (88 mg/g). The saturated adsorption capacities showed Q (HACFs-20%-450)>Q (SACFs-20%-450)?Q (CACFs-20%-450)>Q (JACFs-20%-450)>Q (AC). The adsorption temperature had a great influence on adsorption capacity. Specifically, the adsorption capacity of dichloromethane was 185 mg/g at 20 ? and decreased to 86 mg/g when it was 40?. Besides, an appropriate amount of activator was better for dichloromethane adsorption. Dichloromethane desorption in a low flowing rate of hot N2 and adsorption recycle were carried out. SACFs-20%-450 showed a good regeneration performance. Meanwhile, SACFs-20%-450 had a good adsorption performance on benzene and toluene with the adsorption capacities of 490 mg/g and 763 mg/g. The adsorption breakthrough curves of the hollow carbon fibers exhibited a big slope and short mass transfer height, indicating that the hollow carbon fibers had a fast adsorption mass transfer rate. N2 adsorption-desorption, FT-IR and XPS characterization results revealed that the hollow activated carbon fibers had abundant microporous structure, large specific surface area and rich functional groups.