METHOD OF REMOVING HEAVY METAL IONS FROM ACIDIC WASTE WATERS Russian patent published in 1998 - IPC

FIELD: waste water treatment. SUBSTANCE: invention focuses on acidic waste waters formed in nonferrous metal ore mining process involving shaft or pit excavation techniques. Method allows removing toxic metal ions such as copper, zinc, and iron and consists in two-stage precipitation of metals using lime milk and sodium carbonate to pH 6.0-6.5 in the first stage terminating by separation of precipitate. In the second stage, precipitate is separated by flotation at pH 7.5-8.0 using, as flotation regent, sodium salts of synthetic fatty acids with hydrocarbon moieties containing more than 21 carbon atoms. EFFECT: decreased alkalinity of dumped waste waters, reduced heavy metal content to maximum permissible concentration, and achieved high-speed separation of suspension. 2 cl, 1 tbl