Sorption Properties of Materials Based on Graft Polycaproamide Copolymers

Abstract

Sorption of metal ions with a cation exchanger based on a graft polycaproamide copolymer was studied, and the sorption power of the material was evaluated.Polymer-analogous transformations in grafted copolymer chains are a promising route for introducing new functional groups into pendant chains of polymeric materials [1,2]. A characteristic example is phosphorylation of grafted polycaproamide (PCA) chains. Increased interest in this procedure for preparing ion-exchange materials is caused by the fact that phosphorylation of pendant chains of polymer macromolecules allows not only improvement of the properties of the starting polymers but also preparation of fibrous polymers capable of ion exchange and complex formation depending on the functional groups introduced.Ion-exchange fibrous materials have developed surface and better kinetic characteristics than granular ion exchangers. Their exchange capacity is sufficiently high for practical applications and does not decrease in repeated cycles of regeneration with acids and bases. One of advantages of fibrous materials is the possibility of preparing from them articles of any shape: threads, porous plates, woven and nonwoven fabrics, which is especially valuable when the traditional process implementation is unacceptable [3].Modified polycaproamide fibers with P3OH groups based on graft copolymers of polycaproamide and poly(glycidyl methacrylate) (PGMA) [4] were prepared by phosphorylation of grafted chains with 1-hydroxyethylidenediphosphonic acid (HEDP) [5]. As shown in [6], modification of glycidyl methacrylate (GMA) copolymers at the epoxy group with the aim to prepare a phosphorus-containing sorbent is a promising procedure.The major factor governing the sorption capacity of fibrous cation exchangers is the presence of a sufficient amount of sterically accessible functional groups capable of ion exchange.In this study we examined how the phosphorylation conditions affect the composition and sorption properties of fibrous materials based on PCA3PGMA graft copolymers. The degree of phosphorylation was estimated from the phosphorus content in the modified polymer. Because of possible hydrolysis of the ester group in the grafted PGMA, we performed an experiment on determining the static exchange capacity (SEC) of unmodified PCA3PGMA and obtained the value of 0.4 mg-equiv g 31 . The influence of the phosphorus content on the sorption properties of the fibers is illustrated by Table 1. Table 1 shows that SEC depends on the content of phosphoric acid groups in PGMA, which, in turn, is determined by the structure of the modified PCA and phosphorylation conditions. It should be noted that the phosphorylation of fibers containing 43350% PGMA under the chosen conditions yields a polymer containing 2.9% P, with SEC of 3.9 mg-equiv g 31 . Table 1. Influence of the phosphorus content on the sorption properties of PCA3PGMA copolymer. Graft polymerization: t = 60 min, T = 80oC, [GMA] = 2.35 M; phosphorylation: t = 300 min, T = 90oC, [HEDP] = 4.04 M ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ...

Ion-Exchange Materials Based on Polycaproamide

“…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].…”