ИСТИНА

In our works the adsorption of cryptand-222 (Kr) and cryptates of metal cations has been studied for the first time. In this work we have studied the adsorption nonmetallic cations cryptates of NH4+ and H+. The investigations were carried out by the impedance measurements on stationary mercury drop in 0.1M solutions of NH4Cl or H2SO4 and with additions of Kr with concentrations 10-6 – 10-3M. The differential capacity (C) on potential (E) curves show very large surface activity of cryptates under study: the limit surface coverage of electrode takes place even at the Kr concentration 10-6M. The potential region of NH+4cryptate adsorption is about 1.5V at concentration of Kr 10-3M, it is larger on 0.3V, than in the case of cryptates of alkaline metals cations. Mathematical treatment of experimental impedance data was carried out to obtain the adsorption parameters of NH+4 . These parameters are follows : m – the potential of maximal adsorption; m-limiting adsorption of adsorbate, am – the attraction coefficient at =m, Cm – the value of C at = m , Cm2 – coefficient of square dependence of C=1 on E. Mathematical treatment based on the model of two parallel capacitors supplemented by the Frumkin isotherm and was carried out by using the original regression analysis technique. The whole massive of experimental data for all concentrations for investigated system was used. It was established, that the most close coincidence of experimental and calculated with use of found parameters C,E-curves takes place when the treatment is carried out separately for cathode and anode branches of experimental C,E-curves. It can be explained by difference of adsorbed layers of NH4+cryptate at different potentials. Comparison of these and received earlier data allow to conclude, that the packing of adsorbed layer of NH4+cryptate is less dense and attraction interaction between adsorbed particles less strong in comparison with cryptates of alkaline and alkaline earth metals cations. It is known, that NH4+ cryptate belongs to type of anisodynamic supramolecules, that is the bonding of NH4+ with ligand is more weak, than for metal cations. This peculiarity probably can explain described above effects of increasing area occupied by adsorbed NH4+cryptate and weakening of attractive interaction between these particles in adsorbed layer.