Characteristics of Treated Monazite in Different Particle Sizes to Upgrade the Rare Earth Elements Content by Using Mechanochemical and Roasting Processes

Abstract

Rare earth metals (REE) constitute one of the most crucial groups of elements globally. In Indonesia, deposits of REE have been recognized within monazite minerals extracted from tin mining operations in Bangka. Nevertheless, Indonesia has not used these deposits and has instead heavily relied on imports from other countries. This study aims to recover rare earth metals, specifically Cerium (Ce), Lanthanum (La), Ytterbium (Yb), and Yttrium (Y), from monazite sand, a by-product of tin mining. The method employed in this research is Mechanochemical Decomposition, involving the reaction of monazite samples with a 33 wt% solid Sodium Hydroxide (NaOH) to convert REE-Phosphate compound into REE-Hydroxide. The process begins with sample preparation, involving mechanochemical decomposition using a ball mill, followed by roasting at 400°C, leaching with distilled water, and subsequent steps of filtration and drying at 120°C. Various initial particle sizes, denoted as +65, -65 +100, -100 +140, -140 +170, and -170 mesh, were used to assess their effect on the recovery and grade of REE. Various initial particle sizes, denoted as +65, -65 +100, -100 +140, -140 +170, and -170 mesh, were used to assess their effect on the recovery and grade of REE. The series of procedures revealed notable improvements in the REE content in monazite. The highest recovery of Ce, La, Yb, and Y elements reached 46.43%, 70.08%, 22.69%, and 23.31%, while the highest grade of those elements obtained the values of 4.116%, 1.543%, 0.263%, and 1.681%, respectively. In alignment with prior research, the recovery of Light Rare Earth Elements (LREEs) surpasses that of Heavy Rare Earth Elements (HREEs). However, a unique observation emerges: a diminishing trend in both recovery and grade as particle sizes become finer. This unexpected phenomenon warrants further investigation to elucidate the mechanisms governing rare earth metal recovery from monazite sand under varying particle sizes. 

Keywords

• by-product
• monazite
• particle size
• ree-oxide
• roasting