Treatment of cyanide-containing wastewater by activated carbon adsorption catalytic oxidation

This method was developed by Changchun Institute of gold cyanide-containing waste water purification new technology, has been national patent (ZL 91104787.5). It has been successfully applied to the Dongyaoyu gold mine in Qianxi, Hebei Province, and has low treatment cost, comprehensive recovery of Au, Cu, Pb, Zn, and the discharge of the tailings dam outside the “zero discharge”.

The activated carbon adsorption catalytic oxidation process for the treatment of cyanide-containing wastewater is to add a catalyst and supply sufficient oxygen to the wastewater. The following reaction occurs on the carrier carbon to complete the oxidation and cyanide removal:

CN - + O 2 CNO -

CNO - +2H 2 O HCO 3 - +NH 3

NH 3 +H 2 O NH 4 OH

NH 4 OH NH 4 + +OH -

Since the above reaction is carried out under weakly acidic conditions, and the pH of the mine wastewater is 12 to 14, the pH is adjusted to about 7 by adding sulfuric acid to save acid and prevent HCN from escaping. The carrier carbon is first filled with the catalyst after the adsorption catalyst, and then the cyanide-containing wastewater is added, and the air is bubbled into the adsorption catalytic oxidation. Each bed volume of activated carbon, treated with 52 to 51 bed volumes of cyanide-containing 364 mg ∕L wastewater, cyanide can be reduced to 0.5 mg ∕L. The carrier carbon was washed with 6% HCl to obtain regeneration.

In 1992, the mine treated 1908m 3 of wastewater containing cyanide 250~426mg∕L, and the treated tailings contained cyanide reduced to 0.62mg∕L. After being discharged into the tailings dam, it was discharged from the tailings dam. The cyanide content in water is less than 0.00x mg/L, which is far below the national environmental standards.

The ore is treated with liquid chlorination method to treat cyanide-containing wastewater. The unit cost is 21.57 yuan, and the traffic is inconvenient, and the supply of chlorine is tight, which often affects production. After switching to the activated carbon catalytic oxidation method, the unit cost is reduced to 5.82 yuan, 70% lower than the liquid oxidation method, and a large amount of metals such as Au, Ag, Cu, Pb, and Zn are simultaneously recovered.

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