Structural effects of calcination on Cs-exchanged copper hexacyanoferrate (Cs,K)2CuFe(CN)6 loaded on mesoporous silica particles

Abstract Porous silica particles functionalized by potassium copper hexacyanoferrate (KCu-HCF@silica) are investigated as selective sorbents to remove radioactive cesium from contaminated effluents. This article reports the thermal behavior of Cs:KCu-HCF@silica particles at the laboratory scale, in view of developing hot isostatic pressing processes to compact the Cs-loaded particles into dense waste forms. The data show that the spent particles cannot be hot-pressed directly because the release of volatile compounds does prevent compaction. Preliminary calcination in air leads to (i) the decomposition of Cs:KCu-HCF, (ii) the closure of the mesopores of silica and a reduction in the particles’ specific surface area, (iii) the crystallization of silica into cristobalite, all without significant Cs loss. This retention of Cs is due to the in-situ formation of a Cs based silicate glass with the siliceous particles.