Abstract
The Gibbs energy changes for the reaction between the copper, cadmium, and lead ions complexes with gallic acid and clinoptilolite containing single-charged (Na, K) and double-charged (Ca, Mg) exchange ions were calculated. The software PRIRODA with the PBE/3ζ theoretical method has been used for these calculations:
 (GalAn)2X×2H2O + Clin-Me + 2H3O+ → X(H2O)n-Clin + 2GalAn– + (6-n)H2O + 2Me+(Me2+).
 The thermodynamic possibility of spontaneous ion exchange between complexes of heavy metal ions (Cu2+, Cd2+, Pb2+) with gallic acid and exchange ions of clinoptilolite was shown. This indicates the possibility of removal of these ions from the soil, with their coordination by polyphenols. The possibility of a significant decrease in the content of Cu2+, Cd2+, and Pb2+ ions was investigated both in the absence of gallic acid and in its presence in solution (initial concentration of metal ions of 2 mmol/l, the ratio of Me2+: gallic acid is 1:0, 1:1, and 1:2). It has been found that the sodium form of clinoptilolite influences the growth of sorption properties of clinoptilolite, allowing to exclude 22% more copper ions, compared to the natural clinoptilolite of Sokyrnytsya deposit. Two mechanisms for reducing the concentration of heavy metals in soil have been proposed.
 Keywords: clinoptilolite; sorption; heavy metal; quantum-chemical calculations; gallic acid.
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