SELECTIVE EXTRACTION OF POTASSIUM CHLORIDE FROM SCHOENITE END LIQUOR Russian patent published in 2017 - IPC C01D3/06 C01D3/08 

FIELD: chemistry.

SUBSTANCE: invention can be used in chemical industry. For extraction of potassium chloride solution close to saturated, method comprises preparing schoenite end liquor containing 4.0–5.5 wt%/vol K⁺, obtained during decomposition of mixed kainite salt in schoenite or seaweed Kappaphycus alvarezii juiece, containing 3.0–4.5 wt%/vol potassium chloride, or sea brine containing 3.25 wt%/vol potassium chloride. Method comprises treatment thereof with sub-stoichiometric amount of tartaric acid, neutralised in half with Mg (OH)₂, to obtain potassium bitartrate and potassium-depleted residue. Precipitated potassium bitartrate is separated and washed with water, wash water added to potassium-depleted residue. Potassium bitartrate is treated with a stoichiometric amount MgCl₂ and Mg(OH)₂ for its conversion into magnesium tartrate with extraction of potassium into close to saturated potassium chloride solution. Magnesium tartrate is washed, wash water is stored separately. Potassium-depleted residue and potassium chloride solution are treated with calcium carbonate and calcium chloride for precipitation of residual tartaric acid in form of insoluble calcium tartrate. Magnesium tartrate is added to fresh portion of schoenite end liquor together with stoichiometric amount of aqueous HCl for repeated precipitation of potassium tartrate. Obtained potassium bitartrate is added to washing of magnesium tartrate. Method includes optionally adding an additional amount of water and treating stoichiometric amounts MgCl₂ and Mg(OH)₂ for repeated precipitation of magnesium tartrate and obtaining a solution of potassium chloride KCl, close to saturated. Tartaric acid is recovered from calcium tartrate.

EFFECT: invention makes it possible to avoid need for natural/solar evaporation of streams for extraction of impurity-free potassium chloride from solutions, use a recycled safe extractant for extraction.

15 cl, 2 dwg, 8 ex