Modification of malonamide ion-exchange/chelating resins using the Fields-Kabatschnik reaction and their application to metal ion removal from aqueous solutions

A resin containing 2-aminoethyl-substituted amides of malonic acid was modi fied in the Fields Kabatschnik reaction using diethyl phosphite. The result ant ion-exchange chelating resins heve aminomethylphosphonate groups. modif ication proceeds almost quantitatively giving a resin with p = 1.97 mmol g. N = 4.20 mmol g. anf water regain of 0.44 g g. it can be selectively hydro lyzed by treatment with trimethylchlorosilane potassium bromide in dry acet onitrile. Both acidic and ester forms of the resin were used in the removal of Cu(II), Cd(II), Ni(II), and Zn(II) from their diluted 1 x 10 (-4) N sol utions in 0.2 M acetate buffer at pH 3.7 and 5.6. the affinity of the resin in an acid form toward divalent metal cations is high, and at pH 5.6 the l og K-d is 7.54, 3.97, 3.41, and 3.98, respectively. The resins are selectiv e and the presence of an excess of sodium ions does not influence the uptak e of metal ions. The type of complexes formed between the resins and Cu(II) ions was studied using EPR spectroscopy. The ester form of the resin was u sed in the removal tetrachloroaurate anions from hydrochloric acid solution . It has been found that the log K-d is in the range of 3.14 3.94 for the u ptake of AuCl4- from 5.0 0.5 M HCl solutions.