Rare Earth Minerals Processing

There are two major REE ore minerals from which the REE can be extracted with relative ease: bastnaesite and monazite.

Bastnaesite is a fluorocarbonate mineral that contains predominantly either cerium, lanthanum or yttrium.

In the world-class rare earth deposit Mountain Pass the bastnaesite ore is processed according to the following scheme:

The run of mine material is passing through a cascade of physical processing steps: crushing, screening, grinding, flotation and to produce a bastnaesite pre-concentrates from which products with different REO contents are derived in the following thermal and chemical processing steps.

In the following the RE-chloride solution obtained from digesting the bastnaesite concentrate in hydrochloric acid is passed through a solvent extraction with several mixer-settler steps. The products of this element-selective extraction processes are the separated REE-oxides.

In a typical monazite processing flow sheet the heavy mineral sand is first mined by dredging or scraping, screened and then concentrated in spiral concentrators.

It is then washed and dried and fed into magnetic separators to remove ilmenite and other magnetic minerals. In a subsequent step electrically conducting and nonconducting heavy minerals are separated in electrostatic plate separators followed by induced roll separators that help to distinguish induced magnetic from non-magnetic minerals (i.e. xenotime and monazite from zircon).

The former two minerals can then be separated by wet table or air table taking advantage of their slightly different specific gravities.

The monazite concentrate can then be digested in hot sulfuric acid and partially neutralized. Upon addition of Na₂SO₄ the lighter REE can be precipitated from the sulfuric solution which holds the remaining heavier REE.