PNNL

Abstract

The article demonstrates the complete process of I2(g) capture using Ag-exchanged faujasite (AgX) and Ag-exchanged mordenite (AgZ) zeolite sorbents, the recovery of Ag for recyclability of iodine capture in a Na2S solution, and the immobilization of iodide (from the elution process) into an iodosodalite waste form, which is chemically and environmentally stable. The gaseous iodine, I2(g), was captured in the AgX via chemisorption by Ag and converted to AgI within the aluminosilicate zeolite frameworks. The Na2S elution reaction resulted in the precipitation of Ag2S and dissolution of I– and Na+ into the aqueous solution where powdered material showed higher conversion efficiency than granular forms, which is attributed to Na2S-solution diffusion limitations in the granules. The Ag2S-containing aluminosilicate precipitates were filtered out of the solution and the filtrate (aqueous solution) was used to synthesize iodosodalite to immobilize iodide. The iodine capture using the recovered Ag2S-containing sorbents shows equivalent iodine loadings to the AgX starting material of Qe = 0.355 g/g for powdered material and 0.255 g/g for granular material, demonstrating the potential recycling of Ag for iodine capture as Ag2S-based sorbents.