Preparation and characterization of metakaolin-based Ag0-containing sorbent beads for iodine capture

We report metakaolin (MK)-based sorbents with high metallic silver(Ag 0 ) content for maximizing iodine uptake per unit volume. Spherical beads were fabricated by a droplet method using slurries with various Na/M (M = Na + Al + Si) and H 2 O/Na 2 O molar ratios. Subsequent Ag/Na ion exchange and thermal reduction produced Ag 0 -loaded beads with a dense outer layer and porous core. Increasing the Na/M ratio enhanced the maximum silver loading, total iodine capture capacity, and packing density, while the crushing strength decreased with increasing Na/M and H 2 O/Na 2 O ratios. The resulting Ag 0 MK sorbents exhibited pore sizes larger than the kinetic diameters of relevant iodine species (I 2 , HI, CH 3 I). As a result, their gravimetric iodine uptake reached 0.612 g-I/g-sorbent, demonstrating high efficiency. These findings suggest that Ag 0 MK sorbents are highly effective for iodine capture and hold strong potential for application in off-gas treatment in nuclear fuel reprocessing and reactor systems.