DETERMINATION OF RARE EARTH ELEMENT CONTENTS IN THE PULMODDAI-BASED MONAZITE

Rare earth elements (REE) have become significant to our technological world as they have unique magnetic, phosphorescent and catalytic properties. The demand for REE has increasedin recent past because they can be employed as both metals and alloys. ThePulmoddaideposit is the largest known heavy mineral sand deposit in Sri Lanka which extends to about six kilometers in length and with an average width of hundred meters (Ref?). According to predictions it contains six million tons of heavy mineral sands with high radioactivity. Monazite is a mineral containing thorium which can be used instead of uranium for nuclear power generation and is common in the Pulmoddai deposit. The study wasaimed to diagnose the common heavy minerals using physical and optical properties, estimate the heavy mineral composition of Pulmoddai deposit and toquantify the rare earth element contents in Pulmoddai based monazite. A sand sample was collected up to 50 ? 75 cm depths and heavy minerals were separated through gravitational and magnetic separations. Monazite was microscopically recovered using the optical microscopes. Rare earth element analysis was done using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). According to the results obtained, ilmenite, garnet, rutile, zircon, spinal, silimanite and monazite were major heavy minerals present in the mineral sand deposit and their concentrations were 83.31 %,4.64 %, 2.48 %, 2.10 %, 1.40 %, 2.42 % and 1.38 %respectively. The REE percentages contained in monazite were Cerium (̴28%), Lanthanum (̴15%), Neodymium (̴10%), Promethium (̴3%), Samarium (̴2%), Gadolinium (̴2%) and Yttrium (̴1%). About 3.87g of cerium can be obtained by 1kg of Pulmoddai mineral sand. Due to the higher cerium concentration, value of the Pulmoddai monazite is considered to be economically enhanced and avenues for value addition by extraction of REE from Pulmoddai monazite should be critically evaluated.