Facile synthesis of thiolated silica-encapsulated magnetic adsorbents: Effective adsorption and rapid separation of Au(Ⅰ) from thiosulfate solution

It is important to develop a facile and highly efficient synthetic strategy to fabricate an adsorbent exhibiting excellent adsorption performance and separation ability to recover Au from thiosulfate solutions. Herein, we report a magnetic silica composite (Fe 3 O 4 @SiO 2 -SH) that was successfully fabricated using an economical, one-pot synthesis method for efficient Au(I) adsorption. The results revealed that the performance of the adsorbent was pH dependent, and the single saturated adsorption capacity was 15.11 mg/g. The adsorption process could be well-explained by the Elovich kinetic model and Langmuir isotherm model, indicating that chemical adsorption dominated the monolayer adsorption process. Furthermore, the adsorption process was exothermic. The chemical structures and properties of the adsorbents were analyzed using various characterization and analysis methods. The chelating interaction between -SH and Au(I) promoted the adsorption of Au on Fe 3 O 4 @SiO 2 -SH. The gold-loaded, highly reusable adsorbent could be readily eluted using Na 2 S 2 O 3 (3 mol/L), and > 90% of the gold could be recovered from the adsorbent in a thiosulfate gold leaching solution with Cu 2+ -NH 3 -S 2 O 3 2- as the leaching system. Most of the adsorbent in the pulp could be collected using a magnet, and this reduced the separation cost. The adsorbent can recover more than 90% of gold in both simulated and actual thiosulfate-based gold leaching solutions, indicating that the results reported herein provide a cost-effective strategy for the fabrication of magnetic silica composites characterized by a satisfactory adsorption capacity.