Adsorption of Metal Ions on Gallium(III)-Templated Oxine Type of Chemically Modified Chitosan

Abstract

The oxine type of chemically modified chitosan was prepared by the template crosslinking method employing gallium(III) ion as a template ion. The functional groups of oxine were found to be incorporated into the polymer chain of chitosan at a oxine/glucosamine unit ratio of 1/3. This value agrees with that expected from molecular modeling computation by the molecular mechanics method. Adsorption of molybdenum(VI), vanadium(IV), indium(III), aluminum(III), zinc(II), iron(II), and cadmium(II) together with gallium(III) on this chemically modified chitosan from dilute sulfuric acid solution was compared with that on the original chitosan. It was found that the pH at which the adsorption of these metals takes place on this chemically modified chitosan shifted to a lower pH than that on the original chitosan. The shift was the greatest for gallium(III) among the metal ions examined, which might be attributable to the template effect of gallium(III) ion. The maximum adsorption capacity of gallium(III) was evaluated as 1.17 mol/kg-dry adsorbent. The selective adsorption of small amounts of gallium(III) and in-dium(III) from an excess amount of zinc(II) was confirmed from the breakthrough profile of separation using a column packed with this chemically modified chitosan.