Phosphorus dendrimers, preparation method thereof and use of same for the extraction of actinides and lanthanides

Method for extracting at least one metal chosen from actinides and/or lanthanides present in an aqueous solution, said method comprising, in succession, a step of bringing the aqueous solution into contact with at least one phosphorus-containing dendrimer comprising a core, at least one generation, and an external layer consisting, completely or partly, of identical or different units, the said units satisfying the following formula (I):

• in which R1 and R2, which may be identical or different, are alkyl, alkoxy, or aryl groups, said dendrimer being grafted onto a functionalized mineral particle, said functionalized mineral particle being a silica particle having, before said grafting, one or more groups on its surface that are chosen from —CO2H, dichlorotriazinyl, and epoxyde groups, followed by a separation step so as to separate the dendrimer or dendrimers that has or have trapped the metal(s) of the aqueous solution.