Determination and separation of Pb 2+ from aqueous solutions using a fibrous type organic–inorganic hybrid cation-exchange material: Polypyrrole thorium(IV) phosphate

Abstract

The separation of Pb 2+ from aqueous solutions was studied using a fibrous type polypyrrole thorium(IV) phosphate cation-exchanger column. This type of organic–inorganic composite material was prepared by incorporating polypyrrole into inorganic precipitate of Th(IV) phosphate, providing a new class of hybrid cation-exchangers with good ion-exchange capacity, higher stability, reproducibility and selectivity for heavy metals. The physico-chemical properties of this material were determined using some instrumental analyses. Ion-exchange capacity, pH-titrations, elution and distribution behavior etc. were also carried out to understand the ion-exchange behavior of the material. On the basis of distribution studies, the material was found to be highly selective for Pb(II) and its selectivity was examined by achieving some important binary separations like Pb(II)–Zn(II), Pb(II)–Al(III), Pb(II)–Mg(II), Zn(II)–Hg(II) etc. on its column that indicate its utility in environmental pollution control in one-way or other. For the determination of Pb(II) ions in solutions, a new heterogeneous precipitate based selective ion-sensitive membrane electrode was developed by means of this composite cation-exchanger as electroactive material. The membrane electrode is mechanically stable, with a quick response time, and can be operated over a wide pH range. The selectivity coefficients were determined by mixed solution method and revealed that the electrode is selective for Pb(II) in presence of interfering cations. The practical utility of this membrane electrode has been established by employing it as an indicator electrode in the potentiometric titration of Pb(II).