Pretreatment with Ozone for Gold and Silver Recovery from Refractory Ores

In this work ozonization was studied as pretreatment for two Mexican refractory ores in order to increase the gold and silver extraction. Two methods for contacting ozone with the mineral were studied (indirect and direct). The indirect method did not change the precious metals recoveries for mineral sample A, but increased those of mineral B (from 53 to 88% for gold and from 26 to 78% for silver). The direct pretreatment, only tested in mineral A, did not affect gold and silver recoveries but decreased the extraction time from 40 to 24 hours for maximum metal recovery.