Effect of waters containing complex cyanides and their treatment in Baja de Aries mountains mining area, Romania

摘要

The cyanidation of gold ore concentrates withdiluted alkali solutions at E. M. Baia de Aries, in the presence ofoxygen, provides the solubilisation of gold, silver as well as ofother metals (copper, zinc, iron, nickel, cobalt etc.) forming bothsoluble cyanide salts (NaCN, Ca(CN)_2, KCN) and complexcyanides (Na_xMe(CN)_y where Me=Cu, Zn, Ag, Fe, Au).Some of these cyanides are found in the wastewaters dischargedin the tailings dam after the precious metals recovery. Thesewaters are presently treated with sodium hypochlorite andoverflows in Aries river, which is top water source of Turdatown. The cyanide content of the treated water randomlyexceeds the accepted limit from the legislation in force and thisis due to the complex cyanides with high stability in aqueousmedium. Because of some disadvantages of this method (such as:high consumption of sodium hypochlorite, and chloride andsodium contamination), other methods were tested too: chemicalmethods (precipitation or oxidation using different chemicalreagents: FeSO_4, FeCl_3, H_2SO_4, H_2O_2), physical andchemical methods (activated carbon adsorption, retention on thevolcanic tuffs, ion exchange, reversible, electrodialysis).