Process for the recovery of magnesium

The process of selectively recovering magnesium from an aqueous solution thereof which also contains calcium ions which comprises contacting said solution with a solution of a quaternary ammonium salt of a hydrogen ion exchange reagent in an essentially water-immiscible organic solvent to extract at least a portion of but less than 100% of the magnesium values into the organic phase, separating the magnesium loaded organic phase from the aqueous phase and stripping magnesium from the organic phase, said hydrogen ion exchange reagent being selected from the group consisting of:

• A. .beta.-diketones having the formula ##STR26## where R is phenyl or alkyl substituted phenyl, R' is alkyl, alkyl substituted phenyl or chloro substituted phenyl and R" is H or --CN with the provisos that (1) when R is phenyl, R' is a branched chain alkyl group of at least seven carbon atoms and (2) when R is alkyl substituted phenyl, the number of carbon atoms in the alkyl substituent or substituents is at least 7 and at least one such alkyl substituent is branched chain;
• B. fluorinated .beta.-diketones having the formula ##STR27## where n is a whole integer of 1 to 4, m is 0, 1 or 2 and R is an alkyl group of 1-25 carbon atoms;
• C. benzoxazoles having the formula ##STR28## where R is hydrogen or an alkyl group having from 1 to 20 carbon atoms, R' is hydrogen, chlorine or an alkyl group containing from 1 to 20 carbon atoms, X is H or chlorine and the total number of carbon atoms in R and R' is 6 to 40 with the proviso that one of R and R' must be an alkyl group of at least 6 carbon atoms;
• and
• D. 8-hydroxyquinolines of the formula ##STR29## where R is a branched chain alkyl or alkenyl radical containing about 8 to 20 carbon atoms, R.sub.1, R.sub.2 and R.sub.3 are hydrogen or alkyl groups of 1 to 4 carbon atoms and X is H, chlorine or bromine.