METHOD OF RECOVERING ETHYLENEDIAMINETETRAACETIC ACID FROM SPENT WASHING SOLUTION IN POWER STATION STEAM GENERATORS Russian patent published in 2003 - IPC

FIELD: waste water treatment. SUBSTANCE: spent washing solution is acidified to precipitate free ethylenediaminetetraacetic acid, which is then washed. Method is distinguished by performing acidification and precipitation operation in presence of hydrazine and subjecting solution to continuous stirring under inert atmosphere and bubbling the same inert gas (e.g., nitrogen) to stir solution. Precipitation of EDTA is carried out at temperature above freezing temperature of solution but not superior to 60 C. After the end of EDTA precipitate formation, aqueous solution is drained and precipitate washed with water acidified to pH 1.6-2.0. EFFECT: enabled single-stage process and increased purity of recovered EDTA. 4 cl, 1 dwg, 2 tbl