The linear adsorption critical values of U(Ⅵ) in sand and clay collected in Jiayuguan area, Gansu Province as typical soil mediums were studied by static adsorption experiments. The experimental results show that the equilibrium adsorption isotherms of U(Ⅵ) in sand and clay both conform to the Freundlich model. The linear adsorption critical value is 7.72×10-4 mol?L-1 in a U(Ⅵ)-sand system. When the equilibrium concentration is 0～7.72×10-4 mol?L-1, the adsorption isotherm is linear and the distribution coefficient corresponding to the isotherm slope KF is equal to 16 mL?g-1. When the equilibrium concentration is 7.72×10-4～5.17×10-3 mol?L-1 with the isotherm index α being 1.78 and the adsorption equilibrium parameter KF being 4.12 L?g-1, the distribution coefficient increases from 19.74 mL?g-1 to 71.25 mL?g-1. For a U(Ⅵ)-clay system, the linear adsorption critical value is 7.50×10-4 mol?L-1. When the equilibrium concentration is 0～7.50×10-4 mol?L-1, the adsorption isotherm is linear and the distribution coefficient corresponding to the isotherm slope KF is equal to 46 mL?g-1. When the equilibrium concentration is 7.50×10-4～2.72×10-3 mol?L-1 with the isotherm index α being 1.89 and the adsorption equilibrium parameter KF being 27.39 L?g-1, the distribution coefficient increases from 79.08 mL?g-1 to 144.73 mL?g-1.
