An exploratory study of recovery of rare-earth elements from monazite in mild conditions using statistical-mixture design

Souza A.C.S.P,Giese E.C

doi:10.34256/irjmt2124

Abstract

Monazite is a phosphate mineral, considered an essential source of light rare-earth elements (REE). The present work sought to evaluate different methods of solubilization of REE through the use of different concentrations of inorganic acids (H2SO4, HCl, and HNO3) and organic acids (citric, oxalic, and lactic) in mild conditions at room temperature. According to the results, the inorganic acid solutions favored the solubilization in order of Ce3+, La3+, Nd3+, Pr3+, and Sm3+ elements, while organic acid solutions only favored the solubilization of Ce3+ and La3+. Nitric acid was the more efficient leaching agent for the first group. In the case of organic acids, lactic acid solubilized Ce3+, while mixtures of lactic and citric acids appeared to solubilize La3+.

Highlights

Monazite is an orthophosphate with a predominance of light rare-earth elements (REE)
The inorganic acid solutions favored the solubilization in order of Ce3+, La3+, Nd3+, Pr3+, and Sm3+ elements, while organic acid solutions only favored the solubilization of Ce3+ and La3+
The use of statistical methodologies such as response surface methodology (RSM) and BoxBehnken to optimize monazite ore leaching has been reported in the literature [18]

Summary

Introduction

Monazite is an orthophosphate with a predominance of light rare-earth elements (REE). Radioactive elements, about 0.1-30% thorium (Th) and up to 1.5% uranium (U), can be found in its composition, responsible for imparting electrical, magnetic, and catalytic properties to some REO. In addition to these elements, moderate amounts of iron (Fe), aluminum (Al), calcium (Ca), magnesium (Mg), silica (Si), titanium (Ti), and zirconium (Zr) can be found in monazite [1]. Bioleaching consists of a hydrometallurgical process of dissolving minerals through a group of microorganisms capable of producing acids and or oxidizing agents from the constituents of the ore itself in the leaching process [15].

Experimental

Results and Discussion

Conclusion