Extraction of rare earths from monazite in Pulmoddai deposit

Abstract

Rear earth elements (REEs) have considerable demand in the world and higher market value due to various applications, emerging economies, and continuous depletion of rare earth (RE) metals. Monazite is a perfect source for REEs (61%) and consists of RE and Thorium Phosphate. The Phosphate component was removed by alkaline leaching using NaOH (80 W/V%) at 1800° C for 4 hours at 500 rpm. Thorium was removed by acid leaching using (60 W/V%) HCl at 90° C for 1hour at 500 rpm and 15% pulp density. The solvent extraction method was carried out to separate and purify RE-Oxides from other impurities. 50% Tributyl phosphate (TBP) in kerosene was used as an organic phase with available facilities, and an experiment was done for phase ratio 1 and phase ratio 2, for 3, 6, and 12 minutes of contact time. Inductively coupled plasma mass spectrometry (ICP-MS) analysis was done for elemental analysis. Most abundant REEs in Monazite were Cerium (39%), Lanthanum (20%), Neodymium (12%) and Praseodymium (4%). The main objective of this research was to identify an industrial-level efficient method for separating and purifying RE from Monazite. Economically viable industrial level extraction of REEs was obtained when the phase ratio equals one and 3 minutes contact time.