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 b efore, or in place of, conventional regenerable exchange resins. Vario us agricultural by-products have been proposed as suitable exchangers for this role, but they generally fail to have adequate capacity and p hysical stability for most applications. Two by-products, soybean hull and sugar beet fiber, were found to have enhanced cation-exchange cap acity and stability upon treatment with epichlorohydrin and base. Exch ange capacity was determined by measuring calcium binding. Physical st ability was judged by three different aqueous extraction regimens. The most efficacious and economical reaction conditions found were: soybe an 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 ap plied at a 0.3 : 1 (v/w) ratio, for 6 h at room temperature. The resul tant cross-linked materials had cation-exchange capacities of approxim ately 0.9 (soybean hull) and 1.3 (sugar beet fiber) meq/g dry weight. These epichlorohydrin-treated agricultural by-products may serve as co st-effective, multivalent-cation exchangers. (C) 1994 John Wiley & Son s, Inc.