Commercial acrylic fiber samples were first pretreated with hydrazine under various concentrations to give crosslinked structure. Then, the crosslinked fiber samples with different degree of crosslinking were treated with hydroxylamine hydrochloride to develop ion-exchange fibers. These fibers contain amidoxime, amine, amide, and hydrazide groups simultaneously. The effects of reaction conditions on physical properties, thermal characteristics, surface morphology, ion adsorption quantity, and reusability were investigated. The results show that by increasing the reaction time, temperature, and concentration of hydroxylamine hydrochloride, the content of amidoxime groups in all samples were increased, but with noncrosslinked fibers noticeable drop in the mechanical properties were observed, while in crosslinked sample prepared under optimum conditions of reaction, good ion adsorption capacity with keeping mechanical properties was achieved.
The present work describes a new modification process for producing a chelating ion-exchanger fibers with a distinct selectivity for toxic heavy metal ions. Acrylic fibers were reacted with different diamine compounds in similar conditions. Modified acrylic fibers were prepared by partial conversion of the nitrile groups into amino groups under two-step processes. In the first step, the pure liquid diamine was mixed with the fibers and in the second step, water was gradually added to the reaction flask to reach a predetermined 3M concentration at refluxing temperature of 91 C. The aminated acrylic fibers (AAFs) were used as an ion adsorbent in a series of batch adsorption experiments for removal of chromium(III) and lead (II) ions.Experimental results showed that modified acrylic fiber with tetra methylene diamine (TMD) has the highest Pb(II) ion adsorption capacity. Results also showed aminated acrylic with ethylene diamine (EDA) has the most Cr(III) ion adsorption ability. Solubility tests showed, amination treatments give rise to the intermolecular crosslinkage in all samples. The Freundlich and Langmuir models simulated the adsorption equilibrium data of Cr(III) ions on modified fibers and their constants were determined.
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