Synthesis and characterisation of diamide extractants for the extraction of neodymium

Abstract

The aim of this study was to prepare a series of amide extractants and to assess their properties as potential metal extractants for the rare earth metal neodymium. A number of diamides and a monoamide were synthesized with different substituting groups, including alkyl chains, cyclohexyl chains and aryl chains. The general method for synthesizing these extractants was to react relevant acyl chlorides with secondary amines in a basic medium. The yields for diamides were in the range 32–50% and the yield was 90% for monoamide. A systematic investigation was carried out on the extraction properties of the extractants synthesized using the neodymium ion Nd 3+ to monitor the extraction of a typical trivalent rare earth species. The effects of the variables: diluent type, structure of diamides, aqueous acidity and salting-out agents, on the extraction of Nd 3+ are discussed. The effect of aqueous acidity on the distribution ratios proved that there was competition between the metal ion and HNO 3 for the diamide coordination sites. When the nitric acid concentration in the aqueous phase was varied, maximum extraction was observed in the region of 3 M HNO 3 for all eight diamides investigated. From the results it can be concluded that the diamides are effective extractants for neodymium in the region of 3 M HNO 3. The neodymium can be stripped by very dilute HNO 3.