GB808909A - Improvements in or relating to the recovery of gold from aqueous cyanide liquors - Google Patents

Abstract

Gold is recovered from gold-bearing aqueous cyanide liquors by contacting the liquor with an anion-exchange resin which is predominately weakly basic in character through the presence, at the majority of the ion-exchange positions, of primary, secondary or tertiary amine groups, but which also contains from 1 to 25 per cent of strongly basic (quaternary ammonium) groups, thereby absorbing the auro cyanide which may be recovered by subsequent elution. The weakly basic groups are preferably of the type -CH2NRR1, where R and R1 are hydrogen, methyl, ethyl or b -ethylamine, R and R1 being the same or different. The invention is particularly applicable to the recovery of gold from cyanide solutions containing also copper, nickel and iron. The adsorbed gold values may be removed by an alkali metal or ammonium thiocyanate solution which will simultaneously elute any cobalt, nickel or silver which has been taken up. The thiocyanate eluate may be subjected to electrolysis to deposit gold and any silver and the thiocyanate solution may thereafter be returned for elution of a further batch of resin. If zinc is present in the initial liquor it is taken up by the resin but may be eluted by means of a dilute hydrochloric acid solution prior to the elution of the gold. The anion exchange resins are preferably those derivable from cross-linked polystyrene by treatment with chloromethyl ether and treatment of the resulting product to aminate the -CH2Cl groups thereof. According to examples an aqueous cyanide solution containing iron, copper and nickel in addition to gold was brought into contact with a cross-link polystyrene resin containing 90 per cent of dimethylamine groups and 10 per cent of quaternary ammonium, -CH2N(CH3)3 + groups. The gold was preferentially absorbed. (2) An aqueous cyanide solution containing gold, silver, copper, nickel, cobalt, iron and also sodium thiocyanate was contacted with a cross-link polystyrene having dimethylamine groups and 8.5 per cent of quaternary ammonium groups whereby the gold was preferentially absorbed. The silver and nickel in such an initial liquor may be recovered by first treating the liquor with an anion-exchange resin having mainly dimethylamine groups and about 8 per cent of strong base groups, thereby removing the gold and then with an anion-exchange resin having 60 per cent dimethylamine groups and 40 per cent. strong base groups, the latter resin adsorbing nickel and silver. The nickel and silver may be recovered by elution of the latter resin with sodium thiocyanate, and the silver may be recovered from the eluate by electrodeposition. The nickel may then be removed from the stripped eluate by acidifying the solution and the thiocyanate solution resulting may be neutralized and re-used. Specification 808,910 is referred to.