LAUSR

Abstract The purpose of the paper was to investigate the possibility of obtaining lithium from geothermal water using natural and synthetic zeolites applying poly(acrylic acid). The efficiency of lithium ion sorption was determined depending on the type of tested zeolite, pH of the solution and the presence of anionic poly(acrylic acid). It was shown that the adsorption amount on the surface of aluminosilicates depends on their structure (size of specific surface area and porosity). Moreover, it was proved that the amount of adsorbed lithium ions increases with the increasing pH value of the solution. This is due to an increase in the concentration of negatively charged groups on the zeolite surface that capture the lithium cations from the solution effectively. In general, the addition of anionic polymer increases lithium ions sorption from the LiCl solution at pH 9, at which about 100% recovery of Li cations by Na-X zeolite was obtained. Under these conditions the poly(acrylic acid) carboxyl groups are completely dissociated which guarantees effective formation of polymer-metal complexes and results in the increase of amount of adsorbed lithium ions. The important parameter affecting lithium ions sorption amount is the order of adsorbates addition to the system since the polymer adsorption modifies surface properties of the solid thus influencing the ion exchange process of metal cations. The maximum recovery of lithium cations from geothermal water (at the natural pH 5.5) was obtained in the system containing natural clinoptilolite and anionic polymer. It amounted to almost 5 mg/L (with the initial content of Li+ ions in water about 10 mg/L).