Journal of Ecological Engineering (Jul 2020)
Combined Adsorption of the Copper and Chromium Cations by Clinoptilolite of the Sokyrnytsya Deposit
Abstract
In the paper assessment of the impact of heavy metals on water objects, namely copper and chromium is given, and methods for their neutralization are 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. Methods for determination the sorption capacity of natural zeolite for copper and chromium compounds, methods of analytical control of wastewater components are presented. The results of experimental studies of combined adsorption of copper and chromium cations by natural zeolite under static conditions are presented. 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 extraction of heavy metal ions by zeolite is 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. Analyzing the results of experimental studies of the combined adsorption of copper and chromium ions, it was found that copper ions are significantly better adsorbed by the sorbent than chromium ions. Despite of the same concentration of chromium and copper ions in solution, Cu2+ is selectively extracted. 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. Studies of the static activity of clinoptilolite for copper and chromium ions indicate a simultaneous mechanism of the process, which involves ion exchange and physical adsorption. The concentration of chromium ions on the surface of the sorbent after adsorption less depends on the increase of the concentration of Cr3+ in the original solution. The results of studies of combined adsorption of Cu2+ and Cr3+ ions indicate the possibility of their chromatographic separation, which makes possible their further use.
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