Iodine Removal from Carbonate-Containing Alkaline Liquids Using Strong Base Resins, Hybrid Resins, and Silver Precipitation

Abstract

The ability of several material types to remove aqueous iodine from a mildly alkaline, carbonate-rich nuclear waste stream was evaluated: strong base anion exchange resins (SBARs), hybrid resins, Ag-containing materials, and Bi-containing hybrid resins. A combination of batch testing and flow-through column testing was used in the evaluation. In batch testing, hybrid resins CHM-20, SIR-110-CE, and RTBI were shown to have high efficiency for the removal of both iodide and iodate simultaneously, while Ag-containing materials and SBAR demonstrated high capacity for iodide removal. One example of each material type (CHM-20, A532E, and Ionex 400) was further evaluated for their sorption isotherms and column performance. The Langmuir isotherm, or a Langmuir−Freundlich hybrid isotherm, best described the sorption of iodide to the CHM-20 hybrid resin and Purolite A532E. The Freundlich isotherm best described the uptake of iodate to CHM-20 and A532E and for both iodide and iodate to Ag-containing Ionex 400. In column testing, Purolite A532E had exceptional performance for overall iodide removal. However, with the capacity demonstrated, the A532E resin would exceed class C waste classification before breakthrough initiated, and column change-outs in processing would be dictated by eventual waste classification, not breakthrough. Ionex 400, a Ag-zeolite, was observed to degrade over time under mild alkaline column conditions, whereas the hybrid CHM-20 was limited in the single pass through design and would be best suited for applications where iodide and iodate are present and recirculation of the column effluent is feasible. This work highlights the feasibility of commercially available materials to separate radioiodine from liquid environments.

Influence of Interfering Ions and Adsorption Temperature on Radioactive Iodine Removal Efficiency and Stability of Ni-MOF-74 and Zr-UiO-66

“…Previous investigations have demonstrated a significant temperature dependency of iodine capture from both gas and liquid waste streams − To assess how temperature affects the iodine removal efficiency of the MOF adsorbents, the batch-mode experiments were conducted at 25, 40, and 60 °C using a feed solution of 0.125 mmol/L. As shown in Figure a, the increasing temperature had a positive effect on both the amount and rate of iodine capture over MOF-74.…”

Core–shell Ag@polypyrrole for synchronous pre-enrichment and immobilization of iodine (I−, IO3−) from liquid radioactive wastes

“…In practicality, the I − and IO 3 − species commonly coexist as they are both generated in the used fuel reprocessing. 26 Additionally, the introduction of nano-metal is expected to greatly improve iodine removal by metal interactions. However, most metal-incorporated adsorbents are loaded on the surface of the host by the impregnation method, and some exposed active metal components will dissolve under low acidic conditions, resulting in reduced effective utilization and further degrading the adsorption effect.…”