%0 Journal Article
%T Synthesis and Properties of Anion Exchangers Derived from Chloromethyl Styrene Codivinylbenzene and Their Use in Water Treatment
%A Hesham A. Ezzeldin
%A Allen Apblett
%A Gary L. Foutch
%J International Journal of Polymer Science
%D 2010
%I Hindawi Publishing Corporation
%R 10.1155/2010/684051
%X Amination of vinylbenzyl chloride-divinylbenzene (VBC-DVB) copolymers is an effective method for preparation of ion-exchange resins. Conventionally, the starting polymer is produced by chloromethylation of a styrene-divinylbenzene copolymer that utilizes chloromethyl methyl ether, a known carcinogen. An alterative approach is to copolymerize vinylbenzyl chloride with divinylbenzene to generate the necessary VBC-DVB. This method provides precise control over the density of the ion-exchange groups. The regiochemistry of the vinylbenzyl chloride methods was realized using solvent-ion exchange groups. In this investigation, an improved solvent system was found for the preparation of anion exchange resins by the vinylbenzyl chloride route. The effectiveness of amination of the intermediate VBC-DVB polymers with a variety of trimethylamine reagents was investigated, and ethanolic trimethylamine produced the highest degree of amination. These resulting ion-exchange polymers were characterized by a variety of techniques such as analytical titrations, nitrogen analysis, Fourier transform infrared spectroscopy and thermal gravimetric analysis. Testing of these copolymers for breakthrough was performed. The results indicate that these anion exchangers have a meaningful increase in thermal stability over commercial anionic exchange beads. 1. Introduction Ion exchange membranes (IEMs) can be used for numerous applications including desalination of seawater, softening of hard water, recovery of metal ions, and purification of products and water [1, 2]. Compared with cation exchangers, the anion exchange membranes have less discussion in the literature despite their growing importance for application in retention of multivalent ions and recovery of valuable metals from the effluent of metal plating industry [3]. Conventionally, anion exchangers based on cross-linked polystyrene are prepared by a method that involves chloromethylation of a styrene/divinylbenzene copolymer using either chloromethyl methyl ether or bis chloromethyl ether as the alkylating reagent. Subsequent treatment with amines then introduces the ion-exchange functionality into the polymer [4]. However, both of the alkylating agents have been reported to be strongly carcinogenic agents [5], and their use was seriously restrained in 1967 [6]. Additionally, the chloromethylation reaction also leads to further cross-linking that is detrimental to the performance of the resins [7]. This secondary cross-linking occurs through methylene group bridging and is thought to affect the capacity of the
%U http://www.hindawi.com/journals/ijps/2010/684051/