The Recovery of the Lanthanides from Phosphate Rock - 1985

Rare Earth Deposits & Mining

Habashi reported in 1985 that phosphate rock contains up to 1% lanthanide (rare earths) oxides present in isomorphous substitution for Ca²⁺, Lanthanum, cerium and neodymium form about 80% of the total. When the rock is leached with H₂SO₄ the lanthanides are mostly (about 70% ) lost in the gypsum residue. When the rock is leached with HN0₃ or HCI, more than 80% can be recovered without interference with fertilizer production. At an annual production of 130 million tons. phosphate rock represents an important source of lanthanides. The different met hods of recovery are reviewed.

Recovery is best when the rock is leached with HNO₃. The nitrophosphate solution should be defluorinated by NaNO₃, the free acid partially neutralized with NH₃ to pH 0.2 (no precipitation), then extracted with tributylphosphate. The lanthanides can be stripped with water and precipitated by NH₃ as a phosphate concentrate . The nitro phosphate solution, now lanthanide-free, may be cooled to - 5 °C to crystallize and separate Ca (NO₃)-i 4H₂O then processed further to ammonium phosphate by standard methods. Other methods of recovery based on crystallization at 200°C, or selective precipitation by NH₃ ca n also be used.

The recovery of lanthanides from phosphate rock ca n be done with out disturbing the production of fertilizers, and this represents a step towards the conservation of natural resources.