Low-temperature conversion of spent adsorbent to iodine sodalite by a mechanochemical route

Abstract

The focus on a ball milling induced conversion as a possible synthesis route of iodine sodalite (Na₈Al₆Si₆O₂₄I₂) from zeolite-based iodine adsorbents in order to treat a radioactive iodine filter for the off-gas cleaning during nuclear facilities is presented. A mixture of silver iodide and zeolite 13X as a simulated adsorbent was mechanochemically milled using a laboratory-scale planetary ball mill. The obtained powders were characterized by X-ray diffraction to determine the effect of milling time on the conversion of the iodine sodalite. The crystal grain size and the lattice strain of the grounded phases were evaluated. After the ball milling, the milled samples were hydrothermally crystallized to form a sodalite phase with a sodium hydroxide solution for 48 h in an autoclave maintained at 150^°C. The iodine sodalite was successfully obtained after hydrothermal crystallization. A leaching test was carried out for the assessment of the order of iodine leachability and chemical durability under reducing conditions. The leaching amount was found to be low on the orders of 10⁻⁴ ∼10⁻⁵ mol dm⁻³ in sodium thiosulfate solution. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2441–2447, 2012