In this paper, we examined a new method for decontamination of soils by magnetic separation to reduce the volume of contaminated soils. In this method, we separate paramagnetic 2:1 type clay minerals with strong adsorbility of Cs ions from diamagnetic 1:1 type clay minerals with weak adsorbility of Cs ions. In addition, Cs ions desorbed from 1:1 types by washing are migrated to 2:1 type clay minerals. As a result, the doses of 1:1 type clay minerals can be reduced. First, it became apparent by the particle trajectory simulation that vermiculite, which is 2:1 type clay mineral, could be selectively separated by high gradient magnetic separation using superconducting magnet. Second, we confirmed the separation of vermiculite coexisting with kaolinite, which is 1:1 type clay mineral, by the experiments based on the simulation. Moreover, the experiments using the actual contaminated soils were conducted to examine the migration of Cs ions from 1:1 to 2:1 type clay minerals. As a result, it was observed that Cs ions desorbed from 1:1 types could be adsorbed to 2:1 type clay minerals when using 0.1 mol/L KI as wash solution. It showed the possibility of decreasing the dose of 1:1 type clay minerals.

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