Ion-Exchange Materials Based on Polycaproamide

Abstract

Two redox systems were investigated for developing a method to modify polycaproamide with a phosphorus-containing methacrylate. The more effective method was selected to establish the kinetic parameters affecting the yield of the grafted polycaproamide copolymer. The sorption process of Cu, Ni, and Co ions was studied. The sorption capacity of the obtained sorbent was estimated.Ion-exchange technology has great potential and is being vigorously developed for environmental applications [1,2]. Graft polymerization is interesting because polymers with ion-exchange properties can be produced. This can be achieved by modifying available polymers, e.g., polycaproamide (PCA), with new functional groups [3,4]. Fibrous polymeric sorbents and also the variously shaped items manufactured from them (threads, woven or non-woven cloth) are recommended for extracting rare-earth metals from industrial wastewaters owing to their highly developed surface and better kinetics than granular ion exchangers [5].The effect of the graft-polymerization kinetics of PCA with a phosphorus-boron-containing methacrylate (PMB) on the phosphorus (P) content in the grafted copolymer and the static exchange capacity (SEC) was studied in order to develop an effective method for preparing ion-exchange material. The principal factors of graft polymerization of PCA with PMB in the presence of the redox system (RS) Cu 2+ -H 2 O 2 are considered to be the PMB concentration and the polymerization temperature and time. The PMB structural formula is shown below:where n = 1-8.Two RS, i.e., Cu 2+ -H 2 O 2 and Fe 2+ -H 2 O 2 , were studied during development of the PCA graft-copolymer synthetic method. A literature review showed a definite tendency toward the use of these RS. Therefore, namely these RS were used to develop the PCA graft-copolymer synthetic method. Most researchers pay special attention to RS incorporating a redox-active metal so that one of the RS components can bind to PCA, which increases the efficiency of graft polymerization initiation [6]. Table 1 presents the kinetic parameters for graft polymerization using various RS.The results showed that graft polymerization did not occur without Cu or Fe. The reaction rate with Cu 2+ = 0.0049 M was already 2.0⋅10 -4 mol⋅L -1 ⋅s -1 ; with Fe 2+ = 1.53 M, 1.45⋅10 -4 mol⋅L -1 ⋅s -1 .The initial polymerization rate increased by 2.65 times to 14.5⋅10 -4 mol⋅L -1 ⋅s -1 and by 2.34 times to 12.1⋅10 -4 mol⋅L -1 ⋅s -1 upon increasing the Cu 2+ and Fe 2+ solution content, respectively. The Cu 2+ -H 2 O 2 RS was selected based on the experimental results. Table 2 presents the effect of PMB concentration on the polymerization parameters. The PMB concentration varied in the range 10-50% (aqueous).