A new hydrometallurgical process for extracting rare earths from apatite using solvent extraction with P 350

Abstract

In this paper, a new process is proposed to recover rare earths from nitric acid leaching of apatite without interfering with the normal route for fertilizer production using solvent extraction with dimethyl heptyl methyl phosphonate CH 3P(O)(OC 8H 17) 2 (P 350, B). In the present work, the leaching conditions are studied. In selected condition, apatite was dissolved in 20% (v/v) nitric acid solution at 60–70 °C while agitating. The most suitable acidity for extraction is 0.4 M HNO 3. More than 98% of rare earths in apatite can be recovered using countercurrent extraction process with six stages when phase ratio = 0.5, and defluorination is unnecessary. The influences of phase ratio, stage number, acidity and salting-out agent on extractabilities of P 350 are studied. The results show that rare earths can be separated with P 350 from Ca, P, Fe and other impurities. Mixed rare earth oxides (REO) of which purity is more than 95% with yield over 98% can be obtained.