ADSORPTION OF Pb2+ AND Zn2+ IONS FROM AQUEOUS SOLUTIONS WITH NATURAL ZEOLITE

Pollution of the aquatic environment with heavy metals, particularly lead (Pb²⁺) and zinc (Zn²⁺) ions, is one of our most pressing environmental problems. Even insignificant concentrations of Pb²⁺ and Zn²⁺ ions in the water pose a serious threat to human health, biodiversity, and the functioning of aquatic ecosystems. The work aims to assess the effectiveness of zeolite as a low-cost natural sorbent for purifying the aquatic environment from toxic metals. The experimental part was carried out by a series of laboratory studies under static conditions at a temperature of 20 °C, with a variation of the initial concentrations of metal solutions within 1–30 mg/dm³. The sorbent interacted with the solutions for 48 hours, after which the residual concentration of ions in the filtrate was determined by ionometry and photometry. The obtained adsorption equilibrium data are consistent with the classical Langmuir and Freundlich isotherms. In particular, for zinc ions, it was found that the equilibrium dependence is well approximated by the Langmuir equation with a high coefficient of determination (R² > 0.97). The Freundlich isotherm also showed satisfactory correspondence to the experimental data, which indicates the heterogeneity of the active centres of the sorbent. A comparative analysis of the adsorption capacity showed that natural zeolite has a higher efficiency in removing Pb²⁺ ions than Zn²⁺, which is explained by the physicochemical properties of the ions (in particular, the radius and hydration energy). The results indicate the feasibility of using zeolite as a sorbent for preliminary water purification from heavy metals.