This paper presents results on the characterization and hydrometallurgical studies for the recovery of Rare Earth Elements (REE) from micro-granite type hard rock REE deposit of Bhatikheda, Siwana Ring Complex, Rajasthan, India. The total REE (TREE) content of the ore is 0.36%. Heavy REE (HREE) constitutes about 40% of the TREE by weight. Allanite, zircon and gittinsite were identified as the major REE bearing phases. The nature of occurrence of REE phases in the ore is widely varying with the presence of fully liberated grains to those which occur very finely disseminated in lighter gangue minerals. Physical beneficiation using gravity-based separation techniques gave suboptimal performance. Agitation leaching of ground ore with different mineral acids gave good solubilisation of light REE (LREE), about 75%, but the leach recovery of HREE was only 40%. However, sulfation roasting followed by aqueous leaching (SRAL) yielded leach recovery of 85% of total REE under optimised conditions. The lean tenor of TREE in the leachate coupled with its complex solution chemistry necessitated use of ion exchange (IX) process with strong cationic resin in lieu of conventional solvent extraction based separation and purification. The dissolved REE values from the purified liquor were quantitatively precipitated in the form of TREE fluoride using HF as the precipitant. The final product was about 90% pure on dry weight basis. An integrated process scheme for the recovery of TREE values from the Bhatikhera hard rock deposit is designed-
Uranium mills following the sulfuric acid leaching route produce Uranium Peroxide (UP) as uranium ore concentrate (yellow cake), which is then refined to produce nuclear grade uranium products. Whereas the mills processing ores by alkaline leaching route generate Sodium Diuranate (SDU) as yellow cake, which commonly contains impurities viz. Zr, SiO2, Mo, Organic Carbon (OC). These impurities form muck, interfacial crud and acid insolubles during digestion and solvent extraction (SX) stages in refining process. Hence, SDU needs to be pre-treated before processing in the uranium refinery. India has substantial U reserves (>50%) hosted in carbonate minerals matrix which obviously need alkaline processing for extraction of U. In the present study, the origin of impurities in a SDU produced in an Indian Uranium mill was traced back to the mineralogical composition of the ore, chemical reactivity of minerals to the reagents,and build-up of impurities in process streams due to existence of multiple recycle streams in the milling process flowsheet. A process scheme has been developed for converting SDU into highly pure Heat Treated Uranium Peroxide (HTUP). The scheme involves digestion of SDU in sulfuric acid medium followed by separation of insolubles from the liquor which is later subjected to pH controlled U-peroxide precipitation process. The U-peroxide formed was heat treated to drive-off active oxygen and water of crystallization. A HTUP product assaying about 91% U3O8 was produced from an impure SDU assaying 74% U3O8. Process has been demonstrated at large scale (about 100 kg/batch) and engineering data and scale up parameters have been generated.
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