STATIC ADSORPTION OF HEAVY METALS BY NATURAL ZEOLITE

Heavy metals are considered dangerous pollutants because of their toxicity, even at low concentrations and inability to biodegradation. Increased level of heavy metals in natural waterpools poses a serious threat to all living organisms, including humans. Therefore, the aim of this work is to study the simultaneous adsorption of copper and chromium cations on the surface and in the zeolite volume under static conditions. The chemical composition of the surface and internal space of the zeolite was studied by the X-ray fluorescent method. In the course of experimental studies, a decrease in the content of calcium, magnesium, iron and rare earth metals on the surface and in the volume of the sorbent was revealed. We have revealed that during the adsorption process in the zeolite framework, the amount of exchangeable cations and aluminum also decreases. The regularity of the change in the amount of absorbed copper and chromium cations by a zeolite from their concentration in the initial solution was defined. Comparing the concentration of copper and chromium ions under experimental conditions, we see that the concentration of chromium in the samples was lower than the concentration of copper ions at all stages of the study. This is easily explained by the value of the expected pH for the initiation of precipitation of copper and chromium ions on the surface of the sorbent. We have stadied that in spite of the fact that copper in the initial solution is bivalent and chromium is trivalent, selective removal of copper from a two-component solution takes place. We have evaluated the possibility of the following chemical reactions in the adsorbent-adsorbate system at the same time: precipitation – dissolution of contaminants in the form of sparingly soluble precipitates (hydroxides, salts, complex compounds), exchange and non-exchange sorption-desorption on the active surface of the sorbent.