Synthesis of resin IV: Salicylic acid, diaminonaphthalein, and formaldehyde terpolymer and its ion exchange

This article reports the synthesis, characterization, and ion exchange properties of a terpolymer. The terpolymer resin salicylic acid-diaminonaphthalein-formaldehyde (SDNF) was synthesized by the condensation of salicylic acid and diaminonaphthalein with formaldehyde in the presence of a hydrochloric acid catalyst. Terpolymer resin was characterized by elemental analysis, infrared (IR) spectroscopy, nuclear magnetic resonance spectroscopy, and UV-Visible spectral studies. The number average molecular weight of the resin was determined by nonaqueous conductometric titration. Chelation ion exchange properties have also been studied for Fe³⁺, Cu²⁺, Ni²⁺, Co²⁺, Zn²⁺, Cd²⁺, Pb²⁺ ions employing a batch equilibrium method. It was employed to study the selectivity of metal ion uptake involving the measurements of distribution of a given metal ion between the polymer sample and a solution containing the metal ion. The study was carried out over wide pH range and in a media of various ionic strengths. The terpolymer showed higher selectivity for Fe³⁺, Cu²⁺, and Ni²⁺ions than for Co²⁺, Zn²⁺, Cd²⁺, and Pb²⁺ ions.