Purifying waste waters contg. cyanide ions - by consecutively adding ferrous salt, alkali and then ferric salt to ppte. prussian blue

摘要

Cyanide-contg. waste waters are treated by (1) adding an Fe (II) salt e.g. FeCl2 or FeSO4 to the waste water and precipitating CN- as Fe (II) ferrocyanide and insoluble Turnbull's blue, (2) adding an alkaline material to convert Fe (II)-ions to Fe(OH)2 and (3) adding an Fe (III) salt e.g. FeCl3 or Fe2(SO4)3 to form Fe (CN)6 4- as insoluble Prussian Blue on addn. of an alkaline agent to waste water. Process allows CN- removal from biologically oxidised waste waters having a low CN- concn.