Showing papers by "Hiroaki Egawa published in 1997"

Preparation of phosphoric acid resins with large cation exchange capacities from macroreticular poly(glycidyl methacrylate-co-divinylbenzene) beads and their behavior in uptake of metal ions

Abstract: In order to prepare phosphoric acid resins (RGPs) with large cation exchange capacities, effects of porosity and cross-linking of the precursory poly(glycidyl methacrylate-co-divinylbenzene) beads on their functionalization with phosphoric acid were studied. Two series of precursory copolymers were prepared: one was prepared by changing the amount of divinylbenzene (1–25 mol %) but by fixing that of isobutyl acetate (porogen) at 140 vol % per monomer mixture; the other by changing the amount of the porogen (40–160 vol %) but by fixing that of the cross-linker at 10 mol %. It was clarified that porosity of the precursors plays an important role in the functionalization. Highly porous precursors were functionalized with high efficiency; for example, even the precursors containing 10 mol % of divinylbenzene resulted in RGPs having cation exchange capacities as large as 6–7 meq/g, so long as BET specific surface areas of the precursors were greater than ca. 30 m2/g. The selectivity study has revealed that RGP exhibits the characteristic metal ion selectivity. Lithium ion was adsorbed in preference to sodium and potassium ions; and so-called hard Lewis acid cations, such as uranyl, ferric, and aluminum ions, are adsorbed even from strongly acidic media (1 < pH < 2). Among common divalent metal ions, in addition, the resin exhibits the highest selectivity toward lead ion. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1327–1334, 1997

Recovery of Gallium(III) from Strongly Alkaline Media Using a Kelex-100-Loaded Ion-Exchange Resin

Abstract: Kelex-100 [7-(4-ethyl-1-methyloctyl)-8-hydroxyquinoline] is an important liquid-chelating ion exchanger in hydrometallurgy and a highly selective extractant for gallium (Ga). In this study, Kelex-100-loaded ion-exchange resins were prepared for the recovery of Ga(III) from sodium aluminate solutions (Bayer solution) used in the Bayer process. When macroporous type ion-exchange resins were used as polymer matrices for loading Kelex-100, the physical pore structure and the ion-exchange group significantly affected the adsorption of Ga(III) from strongly alkaline media on the Kelex-100-loaded resin. In particular, the Kelex-100-loaded carboxylic type resin having a macroporous structure showed a high capacity for Ga(III) in concentrated NaOH solution and effectively recovered Ga(III) from the Bayer solution containing large amounts of aluminum(III).

Metal ion selectivity of a macroreticular styrene-divinylbenzene copolymer-based methylenephosphonic acid resin

Abstract: The selectivity of a macroreticular styrene-divinylbenzene copolymer-based methylenephosphonic acid resin (RCSP) toward 17 kinds of metal ions was evaluated in nitric acid media by means of distribution ratio measurements; the order of decreasing affinity was found to be Fe(III) ∼ U(VI) ∼ Mo(VI) > Bi(III) > Al(III) > Gd(III) > La(III) ∼ V(V) > Pb(II) > Cd(II) > Cu(II) ∼ Ca(II) ∼ Ba(II) ∼ Zn(II) > Mg(II) ∼ Co(II) ∼ Ni(II). Among the tested metal ions, Fe(III), Mo(VI), and U(VI) were highly distributed into RCSP even from 6 M nitric acid as in the case of solvent extraction with organophosphorous acids and esters. However, RCSP did not exhibit as high an affinity with these metal ions in 6 M hydrochloric acid.