Flotation-Calcination-Magnetic Separation Hybrid Process for Concentration of Rare Earth Minerals Contained in a Carbonatite Ore

Tesfaye Negeri

doi:10.4236/jmmce.2021.93019

Abstract

A hybrid process consisting of flotation and magnetic separation has been developed to concentrate multi-phase rare earth minerals associated with a carbonatite ore that contains a significant amount of niobium. The deposit is known to contain at least 15 different rare earth minerals identified as silicocarbonatite, magnesiocarbonatite, ferrocarbonatites, calciocarbonatite, REE/Nb ferrocarbonatite, phosphates and niobates. Although no collector exists to float all the different rare earth minerals, the hydroxamic acid-based collectors have shown adequate efficiency in floating most of these minerals. 92% recovery of total rare earth oxide (TREO) and niobium in 45% mass was possible at d80 of <65 microns grind size. It was also possible to reduce the mass pull to 28%, but TREO and Nb’s recovery dropped to 85%. Calcination of the concentrate followed by quenching and fine grinding to <25 μm allowed upgrading the flotation concentrate by magnetic separation. It was demonstrated that at least 87% TREO and 85% Nb could be recovered in 16% of the feed mass. The paper discusses the overall concept of the flowsheet and the experimental strategies that led to this process.

Highlights

Rare earth elements (REEs) include the fifteen lanthanides, yttrium and scandium
A hybrid process consisting of flotation and magnetic separation has been developed to concentrate multi-phase rare earth minerals associated with a carbonatite ore that contains a significant amount of niobium
This paper presents the advancements made in improving the physical separation conditions and upgrading the flotation concentrates by using magnetizing calcination followed by concentrate regrind and magnetic separation techniques

Summary

Introduction

Rare earth elements (REEs) include the fifteen lanthanides, yttrium and scandium. They are found in more than 250 minerals, worldwide [1]. It is possible to liberate them only at fine grinding and is difficult to separate and produce high-grade rare earth mineral concentrates Most of these minerals contain other important elements such as tantalum (Ta), niobium (Nb), uranium (U), and thorium (Th) in varying quantities. The ore was selected for in-depth mineral processing research primarily for its complexity and inadequate response to standard beneficiation methods such as flotation, magnetic and gravity separations. It represents the most important class of primary RE deposit as a carbonatite ore, the only type producing rare earth elements to date. This paper presents the advancements made in improving the physical separation conditions and upgrading the flotation concentrates by using magnetizing calcination followed by concentrate regrind and magnetic separation techniques

Experimental

Flotation

Distributed Addition of Reagents

Flotation Concentrate Upgrading

Conclusions