It is experimentally proved that adsorption of Fe(3+) and Sr(2+) cations on Cambrian clay is described by the Langmuir isotherm. The adsorption limit is 0.026 and 0.034 mol/kg, respectively, and the capacity of the clay is 73±5 mEq/kg. The landing sites of cations are 38.0 and 28.6 Å 2 , respectively, and the radii of hydrated cations are 348 and 302 pm. The latter value agrees with the Stokes radius of 309 pm. The Langmuir constants are 731 and 294, respectively, and the distribution coefficients between the solid and liquid phases at rn = 3.0+3.5 are 27±4 and 10±1.8. The ion exchange constant for the reaction ½ Sr 2+ (s) + 1/3 Fe 3+ (aq) ↔ ½ Sr 2+ (aq) + 1/3 Fe 3+ (s) is 0.95. Based on the data obtained, it is feasible to clean the pounds from strontium-90 contamination by washing with a Fe(3+) salt solution. Field tests in the 5th quarter of Vasilievsky Island of St. Petersburg confirmed the conclusion. The initial specific radioactivity of the pound reached up to 1.07 10 -4 Ci/kg. At heap leaching the purification degree of 60% was obtained, in conditions of convective leaching 90%. A formula for calculating the conditions for obtaining a given degree of purification is proposed.
