Recovery of Total Rare Earth Metal from Deep Sea Nodule Leach Liquor by Solvent Extraction Process

Selective separation of total rare earth metals from the deep sea nodule leach liquor was carried out by solvent extraction method. Leach liquor bearing 0.094 g/L total rare earth, 0.23 g/L Mn, 0.697g/L Cu, 0.2 g/L Fe, 0.01g/L Co and 0.735 g/L Ni was subjected for the removal of iron content by precipitation method at pH.3.95, prior to solvent extraction of rare earth metals using D2EHPA as extractant. Effect of equilibrium pH, equilibrium time and D2EHPA concentration was carried out to establish a suitable condition for effective extraction of total rare earth metals. Eq. pH of the solution was optimized at 2.21, where the coextraction of base metals (Cu, Co, Ni) was not observed. Extraction isotherm plot was constructed at A: O =12:1, eq. pH 2.21, 0.8 M D2EHPA for 2-stages and the predicted condition was further confirmed by 6-Cycles CCS study. Stripping of total rare earth from LO was conducted using HCl solution. Mc-Cabe Thiele diagram study carried out at A: O = 1:5, 4 M HCl showed three theoretical stages are required for quantitative stripping of total REMs. Subsequent stripped solution reads to contain total RE metals at about 5.6 g/L, indicating a very good enrichment of total rare earth metals.