Sorption of terbium on Transcarpathian clinoptilolite

The sorption properties of Ukrainian Transcarpathian clinoptilolite towards aqueous terbium solutions under dynamic conditions have been investigated. The obtained results show that Transcarpathian clinoptilolite most effectively sorbs cationic aqua hydroxo complexes of Tb(III) ions. In addition, it has been found that clinoptilolite samples thermally treated at 350 °C possess the most effective specific surface. Since the content of ion exchange complex of natural clinoptilolite and clinoptilolite thermally treated at 350 °C has been established, it was shown that Na+ cations play a dominant role in an ion exchange process during sorption of Tb(III) ions. The investigation has demonstrated that lanthanide sorption on the Transcarpathian clinoptilolite is caused by the processes of ion exchange and adsorption on the zeolite surface. As a result, the dynamic sorption capacity of clinoptilolite under optimum conditions (zeolite calcined at 350 °C for 2.5 h; 0.20–0.31 mm size of sorbent grains; 3 mL/min flow rate of the 1.0 μg/mL Tb(III) ions solution through sorbent; pH 8.25) was 6.1 mg of terbium per 1 g of clinoptilolite. Moreover, the conditions of terbium desorption from clinoptilolite have been studied. Solutions of HNO3 (7.0 M) and NaCl (1 M) acidified by solution of HCl to pH 2.5 were used, providing 95–100% desorption of terbium concentrated on zeolite.

Figure optionsDownload as PowerPoint slideHighlights
► Optimal temperature of clinoptilolite preliminary thermal treatment is 350 °C.
► OH-groups are Tb(III) sorption active centers of Transcarpathian clinoptilolite.
► Sorption of Tb(III) is a result of ion exchange and of adsorption.
► The best desorbents for Tb(III) are 7.0 M HNO3 solution and 1.0 M NaCl (pH 2.5).