Solvent extraction, separation and recovery of thorium from Korean monazite leach liquors for nuclear industry applications

[Display omitted] •Extraction, separation and recovery of thorium from Korean monazite was studied.•Phosphorous and nitrogen based commercial extractants were examined.•It was concluded that, Prieme JM-T proved as best extractant followed by D2EHPA>PC-88A.•To minimize cerium co-extraction with thorium, cerium oxidation sate was changed from +4 to +3.•Process was developed for thorium recovery and separation from rare earths. The technology for extraction and recovery of the thorium from its source is one of the significant areas of research Present investigation deals on development of a process for extraction of thorium and its separation from the uranium and rare earths contained Korean monazite leach liquor. In the preliminary study, sulfuric acid treatment of monazite concentrate followed by water leaching was carried out. Furthermore double salt precipitation and acid leaching lead to produce thorium rich leach liquor. Various commercial extractants accomplishing D2EHPA, PC88A, Amine and Primene JM-T were tested and optimized for selective separation of thorium. The effective extraction behavior of thorium followed the order as; Primene JM-T>D2EHPA>PC88A and high separation factor was resulted at high acidity (2.5mol/L) of leach liquor, ensuring on high selectivity of Primene JM-T towards loading of Th. The co-extraction of cerium was prevented by changing thorium oxidation state using Fe2+ and H2O2 and reported. The co-extraction of other associated rare earths was scrubbed with sulfuric acid solutions. Subsequently, stripping studies were carryout with two different types of mineral acids and it was quantitative using high acid concentration (5mol/L).