Synthesis and assessment of spherogranular composite tin pyrophosphate antimonate adsorbent for selective extraction of rubidium and cesium from salt lakes

In this study, a spherogranular porous composite tin pyrophosphate antimonate (SSbPP) adsorbent was developed for the efficient extraction of rubidium (Rb) and cesium (Cs) resources. This granular composite adsorbent was prepared using the anti-solvent method with polyvinyl chloride (PVC) as carrier and the incorporated SSbPP powder as adsorbent. The composition, molecular structure, and adsorption performance of SSbPP, along with the microstructure and adsorption behavior of the granulated PVC-SSbPP adsorbent, were comprehensively investigated. The results showed that the SSbPP adsorbent with superior performance was synthesized at a Sn:Sb:P molar ratio of 0.5:0.25:2. The adsorption behavior of PVC-SSbPP was evaluated using the pseudo-second-order kinetic model and Langmuir isotherm. The maximal adsorption capacities of PVC-SSbPP for Rb+ and Cs+ were found to be 81.3 mg g−1 and 95.23 mg g−1 at optimal condition, respectively. The PVC-SSbPP also exhibited high adsorption selectivity for Rb+/Cs+ in the presence of competitive metal ions such as K+, Na+, Li+, Mg2+ and Ca2+. Furthermore, through dynamic adsorption-desorption experiment using a fixed-bed column, a low-concentration Rb+/Cs+ solution (10 mg L−1) could be concentrated by approximately 140 times. This research offers a promising approach for the selective extraction of low-concentration Rb and Cs resources from highly saline solutions.