Gadolinium - Production

Production

Gadolinium is produced both from monazite and bastnäsite.

1. Crushed minerals are extracted with hydrochloric or sulfuric acids, which converts the insoluble oxides into soluble chlorides or sulfates.
2. The acidic filtrates are partially neutralized with caustic soda to pH 3–4. Thorium precipitates as its hydroxide and is removed.
3. The remaining solution is treated with ammonium oxalate to convert rare earths in to their insoluble oxalates. The oxalates are converted to oxides by heating.
4. The oxides are dissolved in nitric acid that excludes one of the main components, cerium, whose oxide is insoluble in HNO₃.
5. The solution is treated with magnesium nitrate to produce a crystallized mixture of double salts of gadolinium, samarium and europium.
6. The salts are separated by ion exchange chromatography.
7. The rare earth ions are then selectively washed out by suitable complexing agent.

Gadolinium metal is obtained from its oxide or salts by heating with calcium at 1450 °C under argon atmosphere. Sponge gadolinium can be produced by reducing molten GdCl₃ with an appropriate metal at temperatures below 1312 °C (melting point of Gd) in a reduced pressure.