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How does sodium metabisulfite treat gold mine wastewater containing cyanide?

Time : 2021-04-28 Hits :

The cyanide method is the most popular gold extraction method worldwide. During this process, cyanide is heavily used, which will generate a large number of cyanide-containing.

Cyanide is a highly toxic substance. It can kill fish etc. when the concentration of cyanide in water (counted by CN-) reach 0.04~0.1 mg/L.

Therefore, the cyanide-containing wastewater must be treated and meet standard before being discharged into the river.

The principle of sodium metabisulfite treating gold mine wastewater containing cyanide: When the wastewater contains copper ions and the pH value is between 7 and 10, the SO2-3

produced by the hydrolysis of sodium metabisulfite and the oxygen in the air co-oxidize cyanide, turning CN- to CNO- ˈafter oxidization.

Then, after hydrolysis, NH3 and HCO- is produced from CNO-, achieving the purposeof removing cyanide.

The reaction equations are as follow:

公式

Treating cyanide-containing wastewater by this method can not only remove free cyanide and most metal cyanide complexes, but also ferricyanide complexes and ferrocyanide complexes that difficult to be treated by other methods.

The reaction process is rapid and sodium metabisulfite is easy to purchase. Also, the treated wastewater can meet the discharge standards with cost.

The experiment indicates that when the pH value is 9.0, the dosage of sodium metabisulfite is 6g/L , the aeration rate is 130L/min, the reaction time is 1h, the water temperature is 30℃, and the stirring speed of flotation machine is 1600r/min rotation,

the best removing effect of cyanide can be achieved.