Study On The Adsorption Properties Of Modified Polyacrylonitrile Fiber For Dyes And Metal Ions

In this dissertation, polyacrylonitrile fiber was modified for adsorbing dyes and metal ions.Firstly, a series of novel ion exchange and adsorption fibers based on polyacrylonitrile fiber were prepared through amination, amidation and carboxymethylation reactions. The experiment results showed that the reaction conditions had great influence on amination reaction. The amination reaction condition became harder with increasing the molecular weight of modifier. The amination reaction was mainly influenced by reaction temperature. It was found that the mixture of CHCl3 and DMF was best solvent for the amidation reaction. The carboxymethylation reaction was mainly influenced by the concentration of reactants and the pH of solution. The products in different periods were characterized by XRD, SEM, FT-IR and TG.Secondly, the adsorption experiment was carried on for the modified fibers whose saturation point and rate of adsorption were determined. The experimental results indicated that the modified fibers had certain adsorptive capacity to the anion dyes after the amination reaction. The more weight gain of the fiber was after the amination reaction, the more adsorption of the fiber was. Moreover, reducing the amount of fibers or increasing the concentration of the adsorbates helped to enhance the adsorption efficiency. After the amidation, the adsorption efficiency was further raised. Furthermore, weak-polar organic materials could be adsorbed, and this adsorptive process was satisfied with the proposed kinetic modelâ…¡. The pH value of aqueous solution containing dye had also influence on absorption process. In certain scope, when the pH value increased, the amount of the absorbed anion dyes decreased. The fibers showed different adsorption equilibrium time and saturated adsorptive capacity due to the different polarity and the molecular dimension of the dyes. The absorption result for methyl orange is excellent and the concentration of anion dye was reduced to ppm level, the absorption rate could reach 96.5%.Caboxylated fiber could adsorb the cation dye, which showed fast adsorption rate and high saturated adsorptive capacity. The concentration of cation dye can also be reduced to ppm level, and the absorption rate could reach 99.2% at the same time. Caboxylated fiber could also chelate the metal ion. When pH value was 6.2, it had high adsorptive capacity.