Preparation And Characterization Of Hemp Bast And Flax Cloth Activated Carbon Fibers

It is well known that activated carbon fibers are one new kind of highly effective, active fibrous adsorbent and environmental material with rich pore structures and special surface functional groups. In this work, hemp bast and flax cloth were used to prepare activated carbon fibers under different activation conditions. Microcosmic figures, pyrolytic process, textural and chemical structure characterizations of the resulting products were characterised in terms of modern analytical instruments and the surface adsorption energy distribution was analyzed using density functional theory (DFT). In addition, the adsorption behavior of phenol, iodine, metal ion Cr³⁺, methyl orange, methylene blue and acid blue 9 onto activated carbon fibers were also studied in order to find the relationships between the adsorption properties, pore structures and surfacial chemistry of the samples. The results are shown as follows:1. Hemp bast activated carbon fibers activated by phosphoric acid not only have a smooth surface but also have a richer pore structures with the specific surface area in the range 986.3～1142.4m²Â·g^-1, and they also have a better adsorption properties. Further, the products activated by phosphoric acid may own some surface functional groups such as carboxyl, carbonyl, hydroxyls, ketone and so on, all of which also exist in the bulk phases, Besides these, some phosphate esters, polyphosphate or phosphate-carbon complexes may be found in the bulk phases of the products, too. Moreover, adsorption energy distribution on the non-micropore surface of the samples activated by phosphoric acid are homogeneous, while the non-micropore surface of the samples activated by phosphoric acid coupled with steam have a gradual change from homogeneous to heterogeneous with the increasing of the activation temperatures.2. Flax cloth activated carbon fibers activated by steam, H₃PO₄ or ZnCl₂ were chosen as the active Agent. At the same activation temperature range between 300 and 700℃, the samples activated by ZnCl₂ have the highest micropores content of 97.02%. The maximum removal of methyl orange onto the sample activated by ZnCl₂ achieved 99.3% when the initial pH value was in the rang of 6～7.