Sorption of Eu(III) from solutions of covalently cross-linked chitosan cryogels

Abstract

The efficacy of using chitosan cryogel modified with pyridoxal-5´-phosphate for extraction of 152,154 Eu(III) from aqueous solutions was established. Enhancement of the sorption properties of CCTZ-PP in comparison to CCTZ is due to the possibility of formation of a bond between Eu(III) with ionized phosphate groups. CCTZ-PP can be recommended for separation and concentraton of 152,154 Eu(III) from low-salt technogenic solutions and natural media.The high content of radioactive wastes in open bodies of water is the main cause of many environmental problems. One method of solving them is to fabricate sorption materials that are highly specific with respect to many radionuclides with different physicochemical properties. From this point of view, the use of polymer sorbents of different physical form based on chitosan is very promising. The polysaccharide nature of chitosan and presence of reactive funcitonal groups in its structure make it possible to synthesize sorbents with new properties and a broad spectrum of sorption activity. Modification can be conducted both to increase the capacity of the sorbent and to selectively sorb different elements, including radionuclides. The published data on the use of funcitonal derivatives of chitosan as sorbents basically concerns sorption of transition metals [1]. Research on sorption of radionuclides is usually limited to a few studies of sorption of U and Th and their analogs using unmodified chitosan or chitosan cross-linked with glutaraldehyde. 152,154 Eu is contained in liquid radioactive wastes with a low level of activity. These radionuclides are characterized by a long half-life and can cause long-term contamination. An analysis of the literature on methods of extracting Eu(III) from solutions using different sorbents [2][3][4][5][6][7][8][9][10] showed that the presence of phosphate groups in them increases the sorption efficacy [2,3]. In addition, we know that organophosphorus compounds (OPC) have been used for separating and removing rare-earth elements (REE) [4,5]. It was shown that the reactikon of REE with OPC results in formation of stable complexes in which the elements are bound through a phosphoryl group.In studying sorption of Eu(III) using aromatic compounds, proteins, humic acids, and polysaccharides [6-9], it was found that the sorption capacity of these compounds is a function of the pH of the solution. High distribution coefficients in sorption of europium on chitin and chitosan were obtained in [10]. Based on laser fluorescence spectroscopy studies, it was hypothesized that the sorption capacity of chitosan is not only determined by the presence of nitrogen in amino groups but also oxygen in carbonyl groups and a macromolecular steric effect.In [1], to increase the effectivness of sorbents with respect to alkaline-earth heavy metals and 2 2 UO + , chitosan was modified by incorporating pyridoxal in its strucutre or by phosphorylation of the chitosan. Amorphization, conducted by reprecipitating chitosan from solution and cross-linking with glutara...

Selective recovery of rare-earth elements from diluted aqueous streams using N- and O-coordination ligand–grafted organic–inorganic hybrid composites

“…Hence, it is crucial to graft or modify the support with functional groups that are highly accessible for REE binding in its protonated state. There are numerous functional moieties containing amine [22,41,62,149,173], carboxyl [22,58,150,174], hydroxyl [175] and phosphoryl [176,177], reported as efficient ones for REE sorption. Undoubtedly, amino groups prove to be one of the best-recommended ones, evidenced by this work as well.…”

Physicochemical, Complexation and Catalytic Properties of Polyampholyte Cryogels

“…This is probably due to the capturing of metal ions in dead volumes of networks that are inaccessible for desoprtion. The high adsorption capacity of polyampholyte and polyelectrolyte cryogels can be used for removal of hazardous metal ions [32,33] and dyes [34,35] from waste water.…”

A Brief History of Polymeric Cryogels

“…Judging from the published information, biomedical and biotechnological applications are the primary uses for the cryogels prepared from polymeric precursors. In addition, some other promising implementation fields also exist for such cryogels, including the employment of rubber-based "cryosponges" developed in Turkey as a reusable sorbent for the removal of oil spill from water surfaces [211,212,214,223], crosslinked chitosan cryogels for the absorption of radionuclides from waste water [224,225], crosslinked and partially saponificated poly(vinyl alcohol) cryogel composites containing activated carbon particles for the absorption of dyes [29,199,200], and so forth.…”