Enhanced Uptake of Iodide from Solutions by Hollow Cu-Based Adsorbents

Cu₂O exhibits excellent adsorption performance for the removal of I^- anions from solutions by doping of metallic Ag or Cu. However, the adsorption process only appears on the surface of adsorbents. To further improve the utilization efficiencies of Cu content of adsorbents in the uptake process of I^- anions, hollow spheres of metallic Cu, Cu/Cu₂O composite and pure Cu₂O were prepared by a facile solvothermal method. Samples were characterized and employed for the uptake of I^- anions under various experimental conditions. The results show that Cu content can be tuned by adjusting reaction time. After the core was hollowed out, the uptake capacity of the samples increased sharply, and was proportional to the Cu content. Moreover, the optimal uptake was reached within only few hours. Furthermore, the uptake mechanism is proposed by characterization and analysis of the composites after uptake. Cu-based adsorbents have higher uptake performance when solutions are exposed to air, which further verified the proposed uptake mechanism. Finally, hollow Cu-based adsorbents exhibit excellent selectivity for I^- anions in the presence of large concentrations of competitive anions, such as Cl^-, SO₄^2- and NO₃^-, and function well in an acidic or neutral environment. Therefore, this study is expected to promote the development of Cu-based adsorbents into a highly efficient adsorbent for the removal of iodide from solutions.