METAL ION SELECTIVITY OF MACRORETICULAR CHELATING CATION EXCHANGE RESINS WITH PHOSPHONIC ACID GROUPS ATTACHED TO PHENYL GROUPS OF A STYRENE-DIVINYLBENZENE COPOLYMER MATRIX

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To clarify the metal ion selectivity sequence of the phosphonic acid resin named RSPO, in which the functional groups were introduced into phenyl groups of a macroreticular poly(styrene-co-divinylbenzene) matrix, the distribution of 20 kinds of metal ions from 0.0001 mol/L solution of each metal ion onto RSPO was studied in nitric, hydrochloric, sulfuric, and phosphoric acid media. Distribution ratios of divalent metal ions Ba(II), Ca(II), Cd(II), Co(II), Cu(II), Mg(II), Mn(II), Ni(II), Pb(II), Sr(II), and Zn(II) normally decreased with solutions of increased acidity and were not significantly affected by acid species. The clear effect of acid species was observed in the distribution of Fe(III), Mo(VI), and U(VI); although their distributions from hydrochloric and sulfuric acid media normally decreased with increasing acidity of solutions, the minimum was observed in their distribution from nitric acid media, indicating that they were distributed onto the resin from approximately 6 mol/L nitric acid through the mechanism similar to solvation extraction of their nitrate complexes with organophosphorous compounds. Phosphoric acid markedly depressed the distribution of Fe(III), Mo(VI), and U(VI) but not the distribution of Al(III), Bi(III), Cr(III), Gd(III), La(III), and Lu(III). The overall metal ion selectivity sequence of RSPO is the order of Mo(VI) ≅ Fe(III) ≅ U(VI) > Bi(III) ≅ Lu(III) > Al(III) ≅ Gd(III) > La(III) > Cr(III) > Pb(II) > Mn(II) ≅ Cd(II) ≅ Cu(II) > Ca(II) ≅ Co(II) ≅ Zn(II) ≅ Ba(II) ≅ Sr(II) > Ni(II) ≅ Mg(II). The metal ion selectivity sequence was also illustrated on the basis of uptake of U(VI), Pb(II), Ca(II), Ba(II), Ni(II) from 0.01 mol/L solutions of each metal ion.