Adsorption of iodide ions on a calcium alginate–silver chloride composite adsorbent

A composite spherical adsorbent for iodide ions was prepared with silver chloride as an adsorption active component, and calcium alginate as a carrier. The adsorbent had an adsorption active component content of 0.96 mmol g−1, a water content of 83%, and a point of zero charge (PZC) of 7.2. The kinetics and thermodynamics of iodide adsorption onto the adsorbent in aqueous solutions were investigated comprehensively, by considering the effects of initial iodide concentration, temperature, solution pH, and coexisting NaCl. The results exhibited that the initial adsorption rate increases with the increase in initial iodide concentration and temperature. In general, the equilibrium adsorption amount was found to be insensitive to coexisting NaCl, and initial solution pH in a range of 1–6. The dominant adsorption mechanism has been proved to be the precipitation transformation reaction. The composite adsorbent used in this study is easy to prepare, avoiding silver chloride from leaching, and has been proved to be an effective iodide adsorbent with an adsorption capacity of 1.1 mmol g−1.