Study of adsorption mechanism of rare earth cations on electrochemical oxidized graphite by radioactive indicators method

Agreement between isotherm equations and the law of active masses was obtained by studying the adsorption isotherms of cerium and terbium on an electrochemically oxidized graphite (EOG)in a.1 and 0.2 N HClO4 and H2SO4 solutions. This confirms the ion-exchange mechanism of the cation adsorption on EOG. The equations of adsorption isotherms, the pattern of rate of isotopic half-exchange and equilibrium adsorption versus pH showed that upon adsorption of REE (at concentrations below 4.10-4 g-ion/1) in 0.1-0.3 N HClO4 solutions one cation replaces 2 H+ ions from EOG, while 0.1-0.2 N H2SO4 3 protons are replaced. In the former case the MeOH2+ cations are generated and adsorbed at EOG while in the second case predominantly Me3+ ions are adsorbed. Different structure of a double EOG layer enables to explain these results. It was shown that differently hydrolyzed REE cations may be adsorbed at EOG with comparable rates up to pH of complete precipitation of hydroxides Me(OH)3