Pentacyanoferrate(II) complexes with N-containing derivatives of chitosan and polyallylamine: Synthesis and cesium uptake properties

Abstract

Here we report on synthesis of new organic–inorganic materials based on products of interaction between sodium aminoprusside and polymer ligands (chitosan (CS), N-2-(2-pyridyl)ethylchitosan (2-PC), N-2-(4-pyridyl)ethylchitosan (4-PC), N-(4-methyl-5-imidazolyl)methylchitosan (IC), N-(2-cyanoethyl)chitosan (CC), polyallylamine (PA), N-(2-pyridyl)methyl-polyallylamine (PMPA), N-2-(2-pyridyl)ethyl-polyallylamine (PEPA), N-(4-methyl-5-imidazolyl)methyl-polyallylamine (IPA) and poly(2-vinylpyridine) (PVP)). The composition of the obtained materials was characterized using the element analysis and X-ray diffraction; the Fourier transform infrared (FT-IR) spectroscopy and thermogravimetric analysis data were used to propose the structure of the formed complexes. It was established that ion and ligand exchange were the main reactions, through which sodium aminoprusside interacts with water-soluble polymer salts. Reactivity in complex formation reaction of unmodified polymers changes in a row: PA>CS>PVP. Modification of chitosan with 2-(4-pyridyl)ethyl and 2-cyanoethyl moieties enhances reactivity of chitosan to the level of PA, while introduction of 2-(2-pyridyl) and (4-methyl-5-imidazolyl)methyl moieties, on the contrary, decreases reactivity of chitosan to that of PVP. At the same time, functionalization of PA with 2-pyridylalkyl groups decreases its reactivity in reaction with aminoprusside ion. Thus, reactivity of all studied polymeric matrices changes in the row: PA≈4-PC≈CC>CS>2-PC≈IPA≈IC>PMPA>PVP>PEPA. The distribution coefficients with respect to cesium ions have been determined for the synthesized complexes in cobalt(II) form. It has been shown that the complex of chitosan with pentacyanoferrate(II) has higher distribution coefficient with respect to Cs+ ions, as compared to its N-derivatives and synthetic polymers. Organic–inorganic materials obtained in the matrix of synthetic polymers have shown higher tendency to peptization and, therefore, lower sorption capacities and distribution coefficients.