Extraction of rare earth metals (REMs) from chloride medium by organo-metallic complexation using D2EHPA

Present report delt with the studies on complexation of rare earth metals (REMs) present in chloride leach liquor of monazite with phosphoric extractant, di-2-ethylhexyl phosphoric acid (D2EHPA). Further, the co-ordination chemistry was studied by determining the complex formation, its structure and validation with standard mathematical model equation. The systematic solvent extraction complexation studies were carried out using 5% D2EHPA diluted in kerosene and mixed with 1% isodecanol (modifier) to form organometallic complex during extraction. After optimizing various process parameters, it was observed that a good separation factors of 17.73 for Nd/La at pH 2 and 12.69 for Pr/La at pH 1.7 were obtained. The value for log D and slope analysis were found 3 as per the expected complex formation (M3+ + 3HA = MA(3) + 3H(+)). Mc-Cabe Thiele plots indicated the requirement of mostly similar to 3 for REMs extraction. The result will be helpful to set multi stage mixer settler unit (MSU) for the recovery of pure solution of individual/mixed rare earth solution. Based on the results of basic scientific studies, the complex formation and number of stage required for the mixer settler units (MSU) in continuous operation in commercial plant can be determined and accordingly designed.