Chelating Ion-exchange Properties of Copolymer Resins Derived from p-Cresol, Oxamide and Formaldehyde

Copolymer resins (p-COF) synthesized by the condensation of p-cresol and oxamide with formaldehyde in the presence of acid catalyst, were proved to be selective chelation ion-exchange copolymers for certain metals. The chelating ion-exchange properties of these copolymers were studied for Fe(III), Cu(II), Ni(II), Co(II), Zn(II), Cd(II) and Pb(II) ions in the form of their metal nitrate solutions. A batch equilibrium method was employed in the study of the selectivity of metal ion uptake involving the measurements of the distribution of a given metal ion between the copolymer sample and a solution containing the metal ion. The study was carried out over a wide pH range, shaking time and in media of various ionic strengths of different electrolytes. The copolymer showed a higher selectivity for Fe(III), Cu(II) and Ni(II) ions than for Co(II), Zn(II), Cd(II) and Pb(II) ions. Distribution ratios (D) of metal ions were found to be increased by increasing pH of the solutions; hence the resin can be used to recover certain metal ions from waste solutions and used for the purpose of purification of waste water and removal of iron from boiler water. The ion-exchange capacity of metal ions has also been determined experimentally and compared with other commercial resins. Besides ion-exchange properties, the copolymer resins were also characterized by viscometric measurements in dimethyl sulphoxide (DMSO), UVvisible absorption spectra in non-aqueous medium, infra-red spectra and nuclear magnetic resonance spectra. The physico-chemical and spectral methods were used to elucidate the structures of p-COF resins. The morphology of the copolymers was studied by scanning electron microscopy, showing amorphous nature of the resins therefore can be used as a selective ion-exchanger for certain metal ions.