PROCESSES FOR EXTRACTING RADIUM FROM URANIUM MILL TAILINGS

摘要

The removal of radium from acid-leached uranium mill tailings has been difficult due to its strong retention as mixed sulfates and in adsorbed forms. With this invention the leaching action of a complexing agent (reducing the free radium cation concentration in solution) is combined with that of a reducing agent. Thus, high valency metal hydroxides and basic salts (notably Fe3+) which tend to retain radium are converted to the lower valency form which is much more soluble in the complexing agent. The reducing agent employed is sodium hydrosulfite, in combination with various organic complexing agents; the preferred complexing agent is EDTA. Over 90% of the radium in uranium leach tailings from Elliot Lake can be removed in 1 hour contact at room temperature with a solution comprising 0.04M of both sodium hydrosulfite and EDTA, with 1.0M potassium chloride added as a surface charge depressant. The gradual addition of the solids to liquid permits the use of low liquid/solid ratios.