Combined Adsorption of the Copper and Chromium Cations by Clinoptilolite of the Sokyrnytsya Deposit

In the paper, the assessment of the impact of heavy metals on water objects, namely copper and chromium was performed, and the methods for their neutralization were defined. A scientifically grounded method for the selection of natural zeolite for the purification of wastewater from heavy metals has been developed, provided that they are jointly present. The physicochemical characteristics of two metals related to heavy metals are presented: copper and chromium. The methods for determining the sorption capacity of natural zeolite for copper and chromium compounds, as well as the methods of analytical control of the wastewater components were presented. The results of the experimental studies on the combined adsorption of copper and chromium cations by natural zeolite under static conditions were presented. The changes in the chemical composition of the zeolite surface as a result of heavy metal sorption have been investigated. The influence of the nature of the ions and the pH of the adsorption medium on the selectivity of the heavy metal ions extraction by zeolite was analyzed. A diagram of the composition of the solution, depending on the pH values, was constructed. The pH of the beginning of deposition of the corresponding heavy metal hydroxides on the zeolite surface was calculated. While analyzing the results of experimental studies on the combined adsorption of copper and chromium ions, it was found that the copper ions are significantly better adsorbed by the sorbent than the chromium ions. Despite the same concentration of the chromium and copper ions in solution, Cu²⁺ is extracted selectively. As can be seen from the results of experimental studies, the concentration of copper on the surface of the sorbent increases from 0.628% mass at a concentration of 0.01 g/dm³ to 47.380% mass at a concentration of 1 g/dm³. The studies on the static activity of clinoptilolite for the copper and chromium ions indicate a simultaneous mechanism of the process, which involves ion exchange and physical adsorption. The concentration of the chromium ions on the surface of the sorbent after adsorption depends on the increase of the concentration of Cr³⁺ in the original solution to a lesser extent. The results of the studies on the combined adsorption of the Cu²⁺ and Cr³⁺ ions indicate the possibility of their chromatographic separation, which makes their further use possible.