Preparation, characterization and performance of silica gel-immobilized poly[N-chloranil N,N,N′,N′-tetramethylethylenediammonium di-sulfosalicylate] for chromatographic separation of heavy metals

Chelating resin loaded with 5-sulfosalicylic acid, Poly[N-chloranil N,N,N′,N′-tetramethylethylenediammonium di-sulfosalicylate], was obtained by an ion-exchange reaction with N,N,N′,N′-tetramethylethylenediamine-chloranil copolymer as matrix. A useful chromatographic packing is prepared by immobilizing this chelating resin on silica gel. A detail analytical characterization of this silica-immobilized sorbent was carried out and optimum and selective sorption conditions for some heavy metals under static and dynamic conditions were established. The maximum absorption capacity was found to be 3.95 μmol of metal ions per gram of the sorbent at their respective optimum pH (optimum pH values for selective metal ions are: Cd²⁺, 3.2; Cu²⁺, 4.5; Fe³⁺, 5.0; Co²⁺, 6.9). The typical flow rates of 5 ml/min for Cu²⁺, Co²⁺ and Fe³⁺, and 3 ml/min for Cd²⁺ were found suitable for selective and quantitative separations of these metals from the multicomponent mixtures of heavy metals present in the water samples. After separation of traces of metals on the sorbent and subsequent desorption with 1 M nitric acid, the metal ions were determined in the eluent by employing differential pulse anodic stripping voltammetry.