ADSORPTIVE SEPARATION OF RHODIUM(III) USING FE(III)-TEMPLATED OXINE TYPE OF CHEMICALLY-MODIFIED CHITOSAN

The oxine type of chemically modified chitosan was prepared by the tem plate crosslinking method using Fe(III) as a template ion. Batchwise a dsorption of rhodium(II) on this chemically modified chitosan was exam ined from chloride media in the absence and presence of a large amount of tin(II). It was observed that the Fe(III)templated oxine type of c hemically modified chitosan shows better performance for rhodium adsor ption than that of the original chitosan. When Sn(II) is absent from t he solution, Rh(III) is hardly adsorbed on the modified chitosan and t he order of selectivity of the adsorption of Rh(III), Pt(IV), and Cu(I I) was found to be Pt(IV) > Cu(II) approximate to Rh(III). On the othe r hand, adsorption of rhodium is significantly increased in the presen ce of Sn(II) and the selectivity order of the adsorption was drastical ly changed to Rh(LII) > Pt(IV) >> Cu(II), which ensures selective sepa ration of Rh(III) from their mixture. Adsorption of Rh(III) increases with an increase in the concentration of Sn(II) in the aqueous solutio n, and maximum adsorption is achieved at a molar ratio, [Sn]/[Rh], of >6. The adsorption of Rh(III) decreases at a high concentration of hyd rochloric acid. The maximum adsorption capacity was evaluated to be 0. 92 mol/kg-dry adsorbent. Stripping tests of rhodium from the loaded ch emically modified chitosan were carried out using different kinds of s tripping agents containing some oxidizing agent. The maximum stripping of rhodium under these experimental conditions was found to be 72.5% by a single contact with 0.5 M HCl + 8 M HNO3.