Synthesis of a polyacrylamidoxime chelating fiber and its efficiency in the retention of palladium ions

A chelating fibrous polymer with metal complexing ability was prepared by partial conversion of the nitrile groups of melana (an acrylonitrile-based synthetic fiber) into amidoxime groups -C(NH2) = NOH using a solution of 3% hydroxylamine in methanol by refluxing at 80degreesC. The molar ratio of NH2OH/CN and the reaction time were adjusted to values of 0.9 and 2 h, respectively. The amidoximated polyacrylonitrile fiber with a 2.89 meq/g ion-exchange capacity functions as an efficient chelating adsorbent for palladium ions. The pH dependence, the contact time, and the temperature of palladium ion retention from a model solution on amidoximated acrylic fiber were studied. The fibrous chelating adsorbent exhibited high affinity for palladium ions in acidic solution (pH = 2-6) at high temperature (50-60degreesC). The values of parameters q(m) and K-L (from the Langmuir equation) determined at different temperatures of adsorption and the thermodynamic quantities DeltaG, DeltaH, and DeltaS were calculated. The adsorbed palladium ions can be quantitatively desorbed by elution with a 0.3% hydrochloric solution of thiourea. (C) 2004 Wiley Periodicals, Inc.