METHOD FOR TREATING WASTERWATER CONTAINING METAL CYANIDE COMPLEX

摘要

PROBLEM TO BE SOLVED: To provide a method for perfectly decomposing free cyan and all of metal cyanide complexes in metal cyanide complex containing wastewater at a relatively low cost. SOLUTION: At first, (1) an oxidation accelerator (hydrogen peroxide or the like) is added to metal cyanide complex-containing cyan wastewater of which the pH is adjusted to an almost constant value of 7 or more to oxidatively decompose free cyan contained in wastewater and, next, (2) the oxidation accelerator is added to wastewater wherein free cyan is oxidatively oxidized and this wastewater is irradiated with ultraviolet rays while the pH of wastewater is stepwise lowered from an alkaline side to an acidic side to decompose a non-ferrous metal cyanide complex contained in wastewater. Further, (3) the wastewater wherein free cyan is oxidatively decomposed and pH is held to an almost constant value of 7 or more is irradiated with ultraviolet rays and aerated to decompose a ferrous metal cyanide complex.