Extraction of rubidium and cesium from a leach solution of lepidolite with biomass carbon adsorbents

Two biomass carbon adsorbents (BCA@PTS and CBCA@PTS) modified with potassium titanosilicate (PTS) were prepared by a hydrothermal deposition method and characterized by means of SEM-EDS, BET, FTIR, XRD, and XPS. The results show that the adsorbents have mesoporous structures, and potassium titanosilicate ((HK3)O2∙3SiO2∙4TiO2∙4H2O) was immobilized in the biomass carbon structure. The adsorption properties of these two adsorbents for rubidium (Rb+) and cesium (Cs+) from an aqueous solution and the tail liquor after extracting lithium from lepidolite were systematically studied. The adsorption amounts increased with increasing pH and decreased with increasing KCl concentration, which were mainly due to the competitive adsorption between H+ or K+ and Rb+ or Cs+ in solution. The adsorption kinetics of the adsorbents were consistent with the pseudosecondary kinetic model, which indicated that chemical adsorption played a leading role in the adsorption process. The adsorption capacities of Rb+ and Cs+ reached 2.57 mmol g−1 and 2.12 mmol g−1, respectively. The adsorption mechanism of Rb+ and Cs+ on the adsorbents was proposed as the ion-exchange between K+ in the adsorbents and Rb+/Cs+ in the solution. In addition, the adsorbents showed high extraction efficiency for Rb+ and Cs+ from two different lithium extraction tail liquors of lepidolite. Therefore, the obtained adsorbents in this work have excellent adsorption performance and show great potential as adsorption materials for Rb+ and Cs+.