UTILIZATION OF WASTE PAN FIBERS AS ADSORBENTS BY CHEMICAL AND THERMALMODIFICATION

Polyacrylonitrile (PAN) polymers obtained from industrial waste fibers (i.e. ''Bulana'') were modified with ethylene diamine (EDA) at low an d high concentration. The structural changes after the chemical treatm ent were determined by IR-spectroscopy following dissolution in concen trated sulfuric acid. The cross-linking formation as well as the forma tion of various groups (such as amine, imine, amide, carbonyl) were ob served. The unmodified and EDA-modified polymers were pyrolyzed in a n itrogen stream at temperatures up to 600 degrees C. The weight losses measured by weighing the sample before and after pyrolysis and thermog ravimetric analysis revealed three regions (up to 300 and 500 degrees C having very high weight losses and above 500 degrees C having lower weight losses), while associated changes of the various groups of the polymers were determined by IR-spectroscopy, The adsorption (discolori ng) ability of the polymers was examined by using aqueous solution of methylene blue or alizarin yellow. The experimental results were corre lated with those of model polymers based on polyacrylonitrile, having known structure, and interpreted on the basis of electron donor-accept or (EDA) interaction concept between the main groups of the polymers a nd the dyes. The adsorption ability of the pyrolyzed polymers up to 30 0 degrees C (especially for the unmodified and low amine modified form s) for both dyes were improved in comparison with the corresponding un modified polymer. The pyrolyzed polymers treated above 400 degrees C s howed no discoloring ability because of the absence of nitrile groups (completely lost through cyclization reactions) and other groups.