Optimization of cyanidation process for gold-bearing ores from Central Kazakhstan

The possibility of processing of 1.09 g/t gold content ore from Central Kazakhstan by cyanidation on activated carbon has been studied. The results of studies on ore phase composition are presented: the total amount of cyanidable gold in the sample is 80.59%; the share of refractory gold not recoverable by direct cyanidation is 19.41% of the total mass of metal; the total share of free gold with clean surface at ore size of 95% grade –0.071 mm is 36.78%. Based on the results of Preg Robbing Adsorption Kinetics test, the preg robbing property of ore is established. It was found that during the ore cyanidation process, the dissolved gold has a reverse deposition effect on the ore. It is shown that when the contact time of ore with solution is increased up to 60 min, the gold allocation to ore components increases from 23 to 50%. Experiments on cyanidation of ore on activated carbon in CIP and CIL modes in a bottle-type agitator at sodium cyanide flow rates of 0.5 kg/t, 0.75 kg/t and 1.25 kg/t were carried out. Norit RO 3515 activated carbon was used as a sorbent. In all experiments CaO was added to the leaching solution at the rate of 1.2 kg/t. The acidity of the solution was maintained at pH = 11.5. On the basis of comparative test results in CIP and CIL modes the superiority of ore cyanidation in CIL mode is shown. The optimal parameters of ore cyanidation in CIL mode were established: duration = 12 hours; NaCN consumption = 0.5 kg/t; acidity pH = 11; oxygen concentration in the solution 11.5 mg/l. Gold recovery in solution was more than 77%.