CROP RESIDUES AS ION-EXCHANGE MATERIALS - TREATMENT OF SOYBEAN HULL AND SUGAR-BEET FIBER (PULP) WITH EPICHLOROHYDRIN TO IMPROVE CATION-EXCHANGE CAPACITY AND PHYSICAL STABILITY

Ion exchange systems for the treatment of process water or wastewater may benefit by the use of inexpensive, disposable exchange materials before, or in place of, conventional regenerable exchange resins. Various agricultural by-products have been proposed as suitable exchangers for this role, but they generally fail to have adequate capacity and physical stability for most applications. Two by-products, soybean hull and sugar beet fiber, were found to have enhanced cation-exchange capacity and stability upon treatment with epichlorohydrin and base. Exchange capacity was determined by measuring calcium binding. Physical stability was judged by three different aqueous extraction regimens. The most efficacious and economical reaction conditions found were: soybean hull and sugar beet fiber hydrated with water at a water-to-solids ratio of 6.4 : 1 and 8 : 1 (v/w), respectively, and epichlorohydrin applied at a 0.3 : 1 (v/w) ratio, for 6 h at room temperature. The resultant cross-linked materials had cation-exchange capacities of approximately 0.9 (soybean hull) and 1.3 (sugar beet fiber) meq/g dry weight. These epichlorohydrin-treated agricultural by-products may serve as cost-effective, multivalent-cation exchangers. (C) 1994 John Wiley & Sons, Inc.