Synthesis of polyimide from 5,5''-bis(bromomethyl)-2,2':6',2''-terpyridine and investigation of the polymer sorption behavior towards some metal ions.

The synthesis of a terpyridine-based polyimide sorbent for solid-phase extraction (SPE) of some metal ions is described. For this purpose, 5,5''-bis(bromomethyl)-2,2':6',2''-terpyridine was polymerized with the corresponding diimide derivatives of dianhyrides to give polyimides utilizing terpyridine unit in the main chain. This polymer was used for its extraction capabilities for Pb(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II), at different pH. Under competitive conditions and at pH<0.6, the selectivity order was Pb approximately Cd approximately Zn. Enhanced selectivity was observed at pH 3.5, the order was Cu>Ni>Zn approximately Cd approximately Pb. Quantitative recoveries>97% were observed for all metals in case loading was stopped before reaching the point of breakthrough. As the synthesized polyimides are insoluble in water, solid-liquid extractions have been carried out and the resins sorption for mixture of basic and/or precious metals have been studied under various experimental conditions (reaction time and hydrochloric acid concentration).