Bentonite is considered as buffer of engineered barrier for retardation of radionuclide migration. Bentonite has low permeability, high swelling and high sorption capacity for radioactive nuclides. Properties have been widely investigated under various geochemical conditions simulating deep geological environments. The chemical stability of bentonite is an important factor in evaluating the long-term stability of the bentonite buffer. However, the presence of impurities in bentonite clays can reduce the retention capacity for retardation of radionuclide migration value of bentonite. Therefore, the bentonite purification is necessary. In the present study, grade improvement of montmorillonite was conducted using ultrasonic and froth flotation methods. As a result of confirming the grade of montmorillonite according to the optimal ultrasonic intensity for ultrasonic irradiation is 1.0 kHz of bentonite in Gyeongju (KJ-II) increased from 60% to 78%. In case of froth flotation method using PSS (0.1 mM) as a reagent, the grade of montmorillonite increased up to 90%.

• Jang-Soon Kwon(Korea Atomic Energy Research Institute, 111, Daedeok-daero 989beon-gil, Yuseong-gu, Daejeon) Corresponding author
• Ki-Jong Jang(Korea Atomic Energy Research Institute, 111, Daedeok-daero 989beon-gil, Yuseong-gu, Daejeon)
• Bong-Ju Kim(Korea Atomic Energy Research Institute, 111, Daedeok-daero 989beon-gil, Yuseong-gu, Daejeon)