Submitted to: Journal of Chemical Technology & Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 22, 2004
Publication Date: November 8, 2004
Citation: Marshall, W.E. and Wartelle, L.H. 2004. An anion exchange resin from soybean hulls. Journal of Chemical Technology and Biotechnology. 79:1286-1292. Interpretive Summary: There is a strong need for inexpensive anion exchange resins for use in environmental remediation. A growing number of serious environmental concerns have arisen over the last several years, including phosphate remediation of groundwater in the Midwest, removal of arsenic from potable water in the Southwest and reduction of selenium in California irrigation water, that could be helped by application of anion exchage resins. A source of cheap resin could arise from the conversion of soybean hulls, a low value, abundant agricultural by-product, to produce an anion exchange resin by chemical modification. This study has developed an optimal procedure for converting soybean hulls to an anion exchange resin that was found to adsorb more toxic anions than a commercial cellulose-based resin. The outcome of these results may be the possibility to develop a less expensive and more effective anion exchange resin from agricultural waste products than more expensive and less effective products already being sold commercially.
Technical Abstract: Agricultural by-products are generally poor adsorbents of anions in solution. Therefore, modification of the by-product could enhance its anion exchange capabilities. The objective of this study was to increase the anion exchange properties of the agricultural by-product, soybean hulls, by chemical modification. Soybean hulls were quaternized with the quaternizing agent, N-(3-chloro-2-hydroxypropyl) trimethylammonium chloride in the presence of a strongly alkaline environment. This modification increased the amount of positive charge on the hulls as evidenced by increased nitrogen content and increased uptake of anions compared to the unmodified hulls. A method to optimize the anion exchange properties of the hulls was developed. Ion exchange properties of the hulls toward anions of environmental significance, namely, arsenate (As), chromate (Cr), dichromate (Cr), phosphate (P) and selenate (Se) were determined. The modified hulls were also compared to commercial cellulose-based and synthetic anion exchange resins in their ability to remove these anions from solution. The experimental and commercial resins were also compared for their ability to remove a mixture of arsenate, chromate, dichromate and selenate from laboratory prepared solutions to levels below the maximum contaminant levels for these anions in drinking water as specified by the US Environmental Protection Agency (US EPA). Our results demonstrate that the soy hull resin is more efficient in anion removal than the commercial cellulose-based resin but not as effective as the commercial synthetic resin.