Caesium Production

The following processes are the methods for the recovery of cesium from pollucite: acid methods, sintering and direct recovery. In acid methods halogen-hydrogen acids, mostly HCl or H₂SO₄, are used. Pollucite is decomposed by H₂SO₄, Cs₃[Sb₂Cl₉] is precipitated from the solution treating it with SbCl₃; after that caesium salt is poured over by hot water or treated by ammonia solution yielding CsCl. Caesium alums CsAl(SO₄)₂x12H₂O are the product of pollucite decomposed by sulphur acid.

Arend's method is the most accepted sintering process: pollucite is roasted with CaO and CaCl₂ mixture, the sinter is leached in autoclave with hot water, the solution is evaporated with H₂SO₄ for separating CaSO₄. The residue is treated by hot water, after which Cs₃[Sb₂Cl₉] is precipitated.

The direct method: granulated pollucite mixture with calcium or aluminium is heated until 900°C in vacuum.

Alums and nitrates fractioning crystallization methods as well as their precipitation and Cs₃[Sb₂Cl₉], Cs₂[SnCl₆] recrystallization are used for separating caesium, rubidium and potassium and obtaining pure caesium compounds. Ion chromatography on synthetic resin and inorganic ionites (for instance, clinoptilolite, etc) also may be used as well as extraction by phenol derivatives, such as 4-sec-butyl-2-methylbenzyl phenol, C7-C9 alkyl phenols etc. Polyhalides are used for high-purity caesium recovering.

Caesium metal may be processed in basic metallothermy via CsC reducing by calcium or magnesium at 700-800°C under 0.1-10 Pa with following rectification and vacuum distillation.