A novel series of water-insoluble cation-exchange resins was produced by heating a commercial phytic acid solution with any of several organic and inorganic materials possessing multiple hydroxyl functionality. Suitable materials for use as substrates were pure polysaccharides such as starch or cellulose, complex polysaccharide mixtures such as those found in agricultural residues (sugar beet pulp, corn bran, or oat hull), simple sugars such as sodium gluconate, and some polymeric inorganics such as silica and powdered glass. These materials were heated with phytic acid at 180 degrees C for 20-35 min in vacuo. The brown to black material produced had an ion exchange capacity for calcium that ranged from 780-5700 mu equiv/g. The silica- and glass-based resins may be suitable materials for the cleanup of radioactive wastes. They have a low carbon content (1-3%), and subsequent vitrification to stabilize the radioactive elements in an insoluble form is simplified because the matrix of the resin is silica.