SORPTION OF IONS LANTHANUM BY CLINOPTILITE

The patterns of sorption of lanthanum ions from model nitrate solutions by the natural sorbent clinoptilolite were investigated. It was shown that clinoptilolite is a rather effective sorbent of lanthanum ions. The kinetics of adsorption of lanthanum ions by clinoptilolite was studied. Based on the results obtained, it was established that the external and internal diffusion is the limiting stage of the process. Along with this, a certain contribution to the overall rate of the process is introduced and the stage of interaction of the adsorbed ions with the functional groups of clinoptilolite. According to Giles’s classification the isotherms of adsorption of lanthanum ions by clinoptilolite belong to L-type isotherms. To obtain quantitative characteristics of the sorption of lanthanum ions on clinoptilolite, the experimental results were processed using sorption models of Langmuir, Freindlich, and Dubinin – Radushkevich. It has been established that experimentally the isotherm of sorption of lanthanum from model nitrate solutions by the natural sorbent clinoptilolite is well described by all models in the same range of equilibrium concentrations. The obtained value ΔG 0sorb = -36.87 kJ/mol indicates a rather high affinity of the sorbent for the sorbate and the advisability of using clinoptilolite to extract lanthanum compounds from model nitrate solutions. Using the Dubinin-Radushkevich model, which indicates the nature of sorbate sorption on the sorbent, it was calculated average free energy of sorption. Calculations showed that the value of the free energy of sorption E = 12 kJ/mol indicates the chemical nature of the interaction of the sorbate with the sorbent. Thus, the process of sorption of lanthanum ions on the surface of clinoptilolite proceeds according to the ion-exchange mechanism, and the fixation of lanthanum ions has a chemical nature.