GB808910A - Improvements in or relating to the recovery of gold from aqueous cyanide liquors - Google Patents

Abstract

Gold-bearing aqueous cyanide liquor containing the complex cyanide of copper, iron and nickel is treated with a weakly basic anion-exchange resin derived from cross-linked polystyrene having primary, secondary or tertiary amino groups at the exchange position to preferentially absorb the aurocyanide, which is thereafter recovered by elution with a solution of an inorganic compound, preferably a 2M alkali metal or ammonium thiocyanate aqueous solution. The resins preferably have at the exchange positions, the group -CH2NRR1, where R and R1 are hydrogen, methyl, ethyl or b -ethylamine, R and R1 being the same or different. According to an example, an aqueous cyanide solution containing nickel, iron and copper and 3 p.p.m. of gold was passed through a column of cross-linked polystyrene resin in chloride form, the resin having at the exchange positions the group -CH2N(CH3)2. The gold was concentrated in the upper part of the column together with minor amounts of nickel, copper and iron, and on elution with two molar aqueous sodium thiocyanate, gold, nickel and copper were recovered; the thiocyanate eluate was then subjected to electrolysis when gold (and any silver if present) was electrodeposited on the cathode. After electrolysis the thiocyanate solution was returned for elution of a further batch. Had any zinc been present it could have been eluted from the column prior to the elution of the gold by means of a very dilute aqueous hydrochloric acid solution, e.g. 0.1 N. Further examples relate to absorption on resins having at the exchange position the groups -CH2NH2, -CH2NH.CH3, -CH2N(C2H5)2, and -CH2NH-CH2-CH2-NH2 respectively.