o-Cresol, thiourea and formaldehyde terpolymer – A cation exchange resin

o-Cresol–thiourea–formaldehyde terpolymer resin was synthesized through the condensation of o-cresol and thiourea with formaldehyde in the mole ratio 1:3:5 in the presence of 2 M hydrochloric acid as a catalyst. The resulting copolymer was characterized with IR and 1H NMR spectral data. The average molecular weight of the resin was determined by Gel permeation chromatography. Thermal study of the resin was carried out to calculate the activation energy (Ea), enthalpy of activation (H^‡), entropy of activation (S^‡), free energy of activation (G^‡), and preexponential factor (A) of various steps of thermal decomposition of the terpolymer. The Dharwadkar and Kharkhanavala method has been used to calculate thermal activation energy and thermal stability. The chelation ion-exchange properties were also studied with the batch equilibrium method. The chelation ion-exchange properties of the copolymer was studied for Fe^3+, Co^2+, Ni^2+, Cu^2+, Zn^2+, Pb^2+ and Cd^2+ ions. The resin was proved to be selective chelating ion-exchange copolymer for certain metals. The study was carried out over a wide pH range and in media of various ionic strengths.