Capture of Iodide by Bismuth Vanadate and Bismuth Oxide: An Insight into the Process and its Aftermath.

As a result of the scarcity of iodine, as well as its threat to the environment if it is present in excess, iodine as a waste needs to be captured. Compared with ion-exchange resins and Ag-containing materials, which are popular iodide adsorbents, Bi-containing compounds show some important advantages, such as high iodide-capture capacity and fast kinetics. In this study, two Bi-containing compounds, BiVO4 and Bi2 O3 , were investigated comprehensively for iodide immobilization. The influence of the pH, iodide/adsorbent ratio, temperature, crystallite size, and competing ions was explored, with a view to optimization of the capture process. Further study of the iodide-adsorbed bismuth compounds confirms that the capture of iodide by BiVO4 and Bi2 O3 is a chemisorption process with the formation of bismuth oxyiodide (Bix Oy Iz ). Furthermore, iodide ions are able to penetrate into the bulk of BiVO4 and Bi2 O3 , which is believed to be responsible for their high capture capacity. The application of Bix Oy Iz as a photocatalyst has also been examined in CrVI reduction. This result makes the capture of iodide by BiVO4 and Bi2 O3 even more environmentally friendly as the photocatalytic application of the iodide-containing adsorbents not only avoids the production of secondary waste but may help to solve other environmental issues.