Extraction process for recovery of rhenium

In a process wherein an aqueous solution containing a relatively high concentration of molybdenum and a relatively low concentration of rhenium is contacted by selective organic extractant solution to preferentially extract the rhenium therefrom without an appreciable extraction of molybdenum into the organic solution and thereafter the organic and aqueous solutions are separated and the rhenium values are separated from the organic phase, the improvement comprising:

• a. providing an organic extractant solution consisting essentially of from at least 0.05% to about 0.1% by volume of a quaternary ammonium compound of the formula [R.sub.3 (CH.sub.3)N].sup.+ A.sup.-, wherein R is an alkyl group having from about 8 to 10 carbon atoms and A is an anion derived from a mineral acid as the active extracting agent and at least 50% by volume of benzene, and contacting said organic extractant with an aqueous solution containing molybdenum and rhenium values, wherein the ratio of concentration of rhenium to the concentration of molybdenum is from about 1:2000 to about 1:3000 and the concentration of rhenium is below about 50 mg/liter.
• b. stripping essentially all of the rhenium value from said extractant after the aqueous solution has been contacted by said extractant and the organic and aqueous solutions have been separated, and
• c. continuously recycling said extractant solution to extract further rhenium values without a substantial loss in extraction capacity.