Method for removing the actinium contained in a rare earth solution with an organophosphorus solvent and rare earth compositions obtained by this method

A method for removing the actinium contained in an initial aqueous solution of rare earth sulfates, said aqueous solution resulting from ore treatment, said method comprising the following steps:

• contacting and mixing the initial aqueous solution with an organic solvent non-miscible in water, said organic solvent comprising at least one cationic extraction agent,
• separation by liquid-liquid extraction of the rare earths and of the actinium, the rare earths, with the exception of part of the lanthanum, being extracted into the organic solvent,
• contacting the organic solvent comprising the rare earths, with the exception of part of the lanthanum, with an acid solution, to produce a rare earth solution having an actinium concentration lower than the actinium concentration of the initial aqueous solution of rare earth sulfates,
• said rare earth solution constituting a rare earth composition comprising the rare earths Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y, and having an La concentration lower than that of the initial aqueous solution.