Applications of Hg(Ⅱ) sensitive polyaniline Sn(Ⅳ) phosphate composite cation-exchange material in determination of Hg~(2+) from aqueous solutions and in making ion-selective membrane electrode

摘要

Polyaniline Sn(Ⅳ) phosphate an 'organic-inorganic' composite material, was prepared via sol-gel mixing of organic polymer polyaniline into the matrices of the inorganic precipitate of Sn(Ⅳ) phosphate. The ion-exchange capacity and distribution coefficients with respect to various metal ions were determined on the column of polyaniline Sn(Ⅳ) phosphate. The distribution studies showed the selectivity of Hg(Ⅱ) ions by this material. However, the sensitivity level of Hg(Ⅱ) ions on the composite material was determined quantitatively. Hg(Ⅱ) ions were separated and determined from the binary aqueous mixtures of Hg(Ⅱ)-Cu(Ⅱ), Hg(Ⅱ)-Ni(Ⅱ), Hg(Ⅱ)-Cd(Ⅱ), Hg(Ⅱ)-Co(Ⅱ), Hg(Ⅱ)-Al(Ⅲ), etc. For the determination of Hg(Ⅱ) ions in aqueous solutions, a Hg(Ⅱ) ion sensitive membrane electrode was prepared by means of this composite cation-exchanger as the electroactive material. The membrane electrode was mechanically stable with quick response time and could be operated over a wide pH range with a slope of 30 mV per decade change in a linear concentration range of 1 x 10~(-1) to 1 x 10~(-6) M. The selectivity coefficients were determined by the mixed solution method and revealed that the electrode was selective for Hg(Ⅱ) in the presence of interfering cations. The practical utility of this electrode was established by employing it as an indicator electrode in the potentiometric titration of Hg(Ⅱ).