Authors: Saehwa Chong, David L. Bollinger, Nicholas Stone-Weiss, Hong Zhong, Kenita Dahal, Xiaofeng Guo, Brian J. Riley, Scott P. Beckman, and John S. McCloy.
Source: Mixed-Anion (Cl + I) Sodalites for Immobilization of Halide Radioisotopes
Radioactive chlorine and iodine isotopes from nuclear processes and accidents like Fukushima pose significant health risks, necessitating effective immobilization. Washington State University researchers developed mixed-anion sodalites, aluminosilicate frameworks, for this purpose. This guide outlines the hydrothermal synthesis method for creating these sodalites, detailing the process for immobilizing radioactive chlorine and iodine.
- Gather Materials: Obtain analytical-grade zeolite 4A, sodium iodide (NaI), sodium chloride (NaCl), sodium hydroxide (NaOH), and deionized water (DIW). Ensure all chemicals are of high purity for optimal results.
- Determine Anion Ratios: Decide on the desired molar ratios for chlorine/hydroxyl (Cl/OH), iodine/hydroxyl (I/OH), or iodine/chlorine (I/Cl) in your mixed sodalite samples. For Cl/OH and I/OH series, maintain a constant NaOH concentration; for I/Cl series, use a 3 M NaOH solution.
- Prepare Precursor Mixture: Combine the precise amounts of zeolite 4A, NaI, NaCl, NaOH, and DIW according to your chosen anion ratios. To minimize hydroxyl incorporation, use excess iodine and chlorine precursors, ensuring their combined amount is ten times the stoichiometric requirement. The total mixture volume should be approximately 10 mL.
- Load Autoclave: Carefully transfer the prepared mixture into a 125 mL polytetrafluoroethylene (PTFE)-lined stainless steel acid digestion autoclave. Securely seal the autoclave to prevent leakage during the reaction.
- Perform Hydrothermal Synthesis: Place the sealed autoclave in an oven and conduct the hydrothermal synthesis at a constant temperature of 180 °C for 8 days. This controlled heating facilitates the formation of the sodalite framework.
- Wash Sodalite Powders: After the synthesis period, allow the autoclave to cool. Carefully collect the synthesized sodalite powders and wash them three times with fresh deionized water, centrifuging at 9000 rpm for 5 minutes after each wash to remove impurities.
- Dry Final Product: Transfer the washed sodalite powders to an oven and dry them overnight at 90 °C. The resulting dry powder is your mixed-anion sodalite, ready for further characterization and application.