Selektive Gewinnung von Salzen aus gemischten Salzloesungen

摘要

1,222,384. Recovering salts from kainite. NATIONAL LEAD CO. 20 June, 1968 [20 June, 1967], No. 29427/68. Heading C1A. Pure kainite salt (MgSO 4 .K 2 SO 4 .MgCl 2 .6H 2 O) (20), preferably purified by flotation (18), is leached (21) with cold water (22) to convert it to schoenite (MgSO 4 .K 2 SO 4 .6H 2 O); the schoonite is separated from the leach liquor and dissolved in water (25), after which it is reacted with Ca(OH) 2 (28) to precipitate a mixed CaSO 4 / Mg(OH) 2 product, the precipitate then being removed and K 2 SO 4 crystallized from the solution remaining. The leach liquor (23) contains MgCl 2 and MgSO 4 and may be reacted with CaCl 2 brine (44) to precipitate CaSO 4 , the remaining MgCl 2 solution being reacted with Ca(OH) 2 (48) to precipitate Mg(OH) 2 and leave CaCl 2 brine (51), part of which is recycled to 44. The Ca(OH) 2 used in 28 and 48 may be obtained by calcining, slaking and degritting a CaCO 3 source. The impure kainite salt (17) is preferably obtained by concentrating an aqueous salt solution (10) containing the ions SO 4 =, Cl-, Mg++, K+ and Na+ to crystallize the sodium, mainly as NaCl (12, 14), and then crystallizing impure kainite (17). The liquid remaining from the kainite crystallization may be reacted with CaCl 2 from (51) to precipitate CaSO 4 and leave MgCl 2 brine. The impure kainite (17) may be purified by flotation (18) employing as a flotation agent a long-chain fatty acid amine of 8-12 carbon atoms, e.g. a fatty amine acetate or chloride, and an aliphatic alcohol as frothing agent, e.g. amyl alcohol.