Use of lipophilic derivatives of aminopolycarboxylic acids for the extraction of rare earths from an acidic aqueous solution

A method of extract at least one rare earth from an acidic aqueous solution, the method comprising:

• contacting (i) a first acidic aqueous solution (A1), comprising a rare earth metal, and (ii) an aminopolycarboxylic acid derivative, having formula (I) or (II):
• wherein
• m is 0 or 1,
• R1 and R2 together form a saturated or unsaturated C5 or C6 ring, optionally comprising a substituent comprising linear or branched C1 to C40 alkyl group, a C5 or C6 cycloalkyl group, or a monocyclic aryl group,
• R3, R4, R5, R6, R7, and R8 are independently H, a linear or branched C1 to C40 alkyl group, a C5 or C6 cycloalkyl group, or a monocyclic aryl group,
• X1 and X2, identical to each other, and X3 and X4, identical to each other but different from X1 and X2, are a hydroxy, a —NHR, or —NRR′, with R and R′ being a linear or branched C6 to C20 alkyl group, a C5 or C6 cycloalkyl group, or a monocyclic aryl group,
• X5 and X6, identical to each other, are —NHR or —NRR′, with R and R′ being a linear or branched C6 to C20 alkyl group, a C5 or C6 cycloalkyl group, or a monocyclic aryl group,
• R9 is a linear or branched C1 to C40 alkyl group, a C5 or C6 cycloalkyl group, a monocyclic aryl group, or a —CH2—CONHR or —CH2—CONRR′ group with R and R′being a linear or branched C1 to C40 alkyl group, a C5 or C6 cycloalkyl group, or a monocyclic aryl group, and
• R10 is a —COOH group,
• thereby extracting from the first acidic aqueous solution (A1) at least one of the rare earth metal,
• wherein the aminopolycarboxylic acid derivative functions as an extractant.