Budnyak T. Sorption of transition metal ions by chitosan-mineral carrier composites

The thesis is devoted to development of methods of synthesis of organomineral composites chitosan-inorganic adsorbent and investigation of ways of further functionalization of their surfaces, studying of adsorption properties of synthesized hybrid adsorbents with respect to oxoanions and cations of transitions metals. Chitosan-mineral carrier composites were obtained via crosslinking of adsorbed biopolymer and by covalent immobilization, and sol-gel transformations. Synthesized organomineral composites have been shown to display high enough sorption capacity with respect to metal-containing oxoanions in the broad range of medium acidity and kinetical characteristics on a level of inorganic carriers. Optimum conditions of the studied ions adsorption were investigated: the medium acidity values and time of contact of adsorbents and metal solutions. It was determined that V(V), Mo(VI), and Cr(VI) oxoanions are extracted with the highest degree of adsorption from aqueous solutions at the acidic pH medium, and cations of transitions metals Zn(II), Pb(II), Cu(II), Cd(II), Fe(ІІI) from neutral medium in form of aqua complexes, and from slightly alkaline medium in form of mixture of ammine-, acetate- and mixed-ligand complexes of these metals, with the participation of ammonia and acetate ions. Functionalization of surface of chitosan-silica gel composite with iodoacetic acid was conducted for increasing adsorption properties with respect to cationic forms of studied metals. It was shown that adsorption of metal oxoanions in most cases described by the Langmuir equation model, and the adsorption of studied metal cations correlates well with the equations of the Langmuir and Freundlich models.