The PUREX process is a liquid–liquid extraction ion-exchange method used to reprocess spent nuclear fuel, in order to extract primarily uranium and plutonium, independent of each other, from the other constituents. The current method of choice is to use the PUREX liquid–liquid extraction process which uses a tributyl phosphate/hydrocarbon mixture to extract both uranium and plutonium from nitric acid. This extraction is of the nitrate salts and is classed as being of a solvation mechanism. For example, the extraction of plutonium by an extraction agent (S) in a nitrate medium occurs by the following reaction.
