Robust Dual-Network Hydrogels Functionalized with Thiostannate for Selective Cesium Adsorption from Brines

To achieve efficient and selective extraction of cesium (Cs+) from complex salt-lake brines, this study developed a dual-network hydrogel adsorbent based on ammonium thiostannate (NTS), denoted as NTS@(SA+PAA)-1.0. The dual-network hydrogel, composed of sodium alginate (SA) and poly(acrylic acid) (PAA), serves as a stable support for the NTS powder, endowing the adsorbent with favorable mechanical robustness and high salt tolerance. Static adsorption experiments revealed that the composite adsorbent retains the excellent Cs+ selectivity inherent to the pristine NTS powder. In the presence of competing ions (e.g., Na+ and Mg2+), the distribution coefficient KdCs exceeds 104 mL/g. Dynamic column adsorption experiments further confirmed the material’s significant Cs+ enrichment capability in real brines. A single adsorption–desorption cycle resulted in a nearly 13-fold increase in the Cs+ concentration and an approximately 72-fold increase in the mass fraction. After five consecutive cycles, the material maintained structural stability and sustained its adsorption performance. This study provides a novel composite gel adsorbent with practical application potential for the efficient and continuous extraction of cesium from brine.