SORPTION OF Cu(II) AND Co(II) IONS BY A HYBRID ADSORBENT BASED ON ZEOLITE AND HYPERBRANCHED POLYESTER
A hybrid adsorbent based on zeolite NaX modified with hyperbranched polyester with terminal benzoylthiocarbamate groups has been synthesized. The sorption activity of a hybrid adsorbent with respect to a transition metal ions was studied using the example of Cu(II) and Co(II) ions in an aqueous medium under static conditions by the method of constant weights and variable concentrations. Kinetic curves and sorption isotherms of Cu(II) and Co(II) ions were plotted in the concentration range of 2.42-24.2 g/l for Cu(II) and 2.91-29.1 g/l for Co(II). The type of isotherms corresponds to monomolecular adsorption and refers to Langmuir type L isotherms according to the Giles classification. The resulting isotherms were processed within four sorption models: Langmuir, Freindlich, Dubinin-Radushkevich, and Temkin. It has been determined that the adsorption isotherms of the hybrid adsorbent to Cu(II) and Co(II) ions are most adequately described by the Freundlich model, which confirms the occurrence of chemisorption on a heterogeneous surface. The limiting sorption capacity and Gibbs energy of the adsorbent to Cu(II) ions are 34.83 g/kg and -9.66 kJ/mol, to Co(II) ions 18.39 g/kg and -9.58 kJ/mol. Zeolite sorption isotherms are described by the Langmuir equation as follows: 77.80 g/kg and -6.16 kJ/mol for Cu(II) and 81.86 g/kg and -4.89 kJ/mol for Co(II). It has been established that the modification of the zeolite leads to a decrease in the sorption capacity and an increase in chemisorption in comparison with the original zeolite, which is explained by the presence of benzoylthiocarbamate groups in the polyester and carbamate groups in the binder. It is shown that the process of regeneration of the synthesized adsorbent occurs in a more acidic medium at pH 4, which confirms the high stability of the complexes in the sorbent based on zeolite and hyperbranched polyester polybenzoylthiocarbamate.