SORPTION OF BISMUTON (III) IONS FROM AQUEOUS SOLUTIONS BY SILICAS MODIFIED BY ORGANIC REAGENTS

In current paper, adsorbents based on silica L 40/100 modified with 4-(2-pyridylazo)resorcinol, 1-(2-pyrylazo)naphthol‑2, pyrocatechol violet and sodium N, N‑diethyldithiocarbamate were obtained. Adsorbents were modified by non-covalent immobilization of organic analytical reagents on the silica surface. It is noted that the preparation of such adsorbents is fast and easy to manufacture. The conditions of Bismuth (III) adsorption from dilute aqueous solutions by the proposed adsorbents are studied and optimized. The optimal values of the medium acidity for the effective Bismuth (III) preconcentration by the proposed adsorbents based on silica modified with organic analytical reagents have been established. It is shown that the use of modified silicas allows efficient (95–98%) removal of Bismuth (III) from dilute aqueous solutions. Under optimal adsorption conditions, the capacity of modified adsorbents is determined. It is established that the modification of silica leads to a significant (2–3 times) increase in the capacity of the obtained sorbents by Bismuth (III) in comparison with the unmodified silica, which is associated with the processes of complexation on the surface. The desorption of Bismuth (III) from the surface of unmodified and modified silicas by solutions of mineral acids has been studied. It is shown that Bi(III) is quantitatively desorbed from the surface of unmodified silicas by solutions of sulfuric and nitric acids, and in the case of modified silicas the degree of desorption is small and does not exceed 35%. The data obtained can then be used to develop a test system for determination of Bismuth (III) via corresponding colorimetric scales or for quantitative solid phase extraction and adsorption-spectroscopic quantification of Bismuth (III) in some real samples.