Study of the chemical durability of a hollandite mineral leached in both static and dynamic conditions

Abstract

Hollandite is a ceramic used for the confinement of cesium. In this study, we synthesized a hollandite of chemicalformula: $K_{0.28}Ba_{0.76}Ti_{7.10}Cu_{0.9}O_{16}$, where K simulates cesium. This new formulation of a copper-containing hollanditewas synthesized by a double calcination; the first one at 950°C during 18 h, and the second one at 1000°C during 6 h.The mineral was identified by X-ray diffraction. Various leaching tests are employed in order to assess the chemicaldurability of this mineral. The static test MCC1 gave elemental leaching rates of: 7.097 $10^{-5}$ g $cm^{-2};d^{-1}$ for Cu, 5.592 $10^{-7}$g $cm^{-2};d^{-1}$ for Ti and 4.630 $10^{-6}$ g $cm^{-2};d^{-1}$ for Ba, after 42 days. This corresponds to dissolved elements percentages of:5.7% Cu, 0.0007% Ti and 0.2% Ba. The equivalent amount of dissolved K is 0.0029%. A static test in the presence of aclay barrier, gave the best leaching rates (at 42nd day, NR