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The sorption of the lead, cadmium and copper cations in static conditions on the rock of clinoptilolite of the Sokyrnitsa deposit (Transcarpathian region,Ukraine) has been investigated using the conventional complexonometric analytical technique as well as quantum chemical calculations. The samples of сlinoptilolite were previously transferred to sodium form, treated with 1M sodium chloride solution for 8 hours at a temperature of 90 degrees Celsius. The grain size of clinoptilolite was 2-3 mm. For the study of sorption, a series of solutions of nitrates of the corresponding metals have been used; the initial concentration of solutions was 0.02 mol / liter. The mass ratio between clinoptilolite and solution was 1:20.Sorption was investigated in the presence of salicylic acid, which has been employed in order to model the behavior of various fulvic acids in the soils. In parallel, the quantum-chemical calculations, in order to check the possibility of sorption of lead, cadmium and copper ions in the presence of salicylic acid, have been carried out. For the above calculations, a fragment of clinoptilolite with an aluminum atom in the T1 position was used, whereas sodium cation has been used as an anti-cation. Optimization of geometry and calculation of thermodynamic parameters were carried out using the PBE/3ζ level method using the software PRIRODA.The results of the calculations of the exchange reaction (1) show the possibility of its spontaneous flow (the negative value of the change of Gibbs energy) for all the considered metals (lead, cadmium and copper).Clin-Na(H2O)3 + (Sal)2Ме(H2O)n + (12-n)H2O→ Clin-Me(H2O)3 + 2(Sal–)(H2O)3 + Na(H2O)6 (1)The presence of salicylic acid leads to a decrease of the sorption ability, but even the 1 : 2 ratio of Me2+ : salicylic acid can reduce the concentration of metal by 70% for cadmium, 48% for copper and 42% for lead.Thermodynamic calculations have been confirmed experimentally, and can readily be used in further investigations on the decontamination, by using clinoptilolite and other inorganic and mineral sorbents, of the soils contaminated and/or polluted with the heavy metal ions. |
