Uranium recovery by resin-in-pulp (RIP) from sulphide-bearing material was found to be adversely affected by polythionate formation due to partial oxidation of sulphide minerals. Polythionates are loaded more selectively by the conventional strong-base resins used at uranium plants.A study was undertaken to identify whether polythionates are formed during upstream processing, leaching, or ion exchange recovery steps. It was found that polythionate formation could be minimized by shortening of the leach time, optimizing oxidant and acid addition, minimizing delay between leaching and RIP, and maintaining the neutralization and adsorption retention times as short as possible.These insights could prompt the development of mitigation strategies on commercial plants to reduce or avoid the formation of polythionates and the adverse impact it has on uranium recovery. uranium recovery, resin-in-pulp, polythionate formation.* Mintek, Randburg, South Africa.

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Gold deposits that can be treated by conventional cyanidation/carbon-in-pulp (CIP) processes are becoming exhausted around the world (González-Anaya, Nava-Alonso, and Pecina-Treviño, 2011). Mining companies have thus shifted their focus to the processing of refractory and double refractory gold ores. Commonly, in these types of ores, the gold is associated with sulphide minerals. The presence of sulphides can affect gold recovery via cyanidation due to encapsulation or passivation of the gold, thereby increasing reagent consumption. In the case of double refractory ores, gold recovery is further limited due to the presence of carbonaceous materials as well as sulphides. Carbonaceous material can encapsulate and/or adsorb gold from cyanide solution, thus competing with activated carbon added (the so-called pregrobbing effect).A number of approaches have been developed for the treatment of refractory/double refractory gold ores. In order to overcome refractoriness associated with sulphides the partial or complete destruction of sulphides (and sometimes carbon) via chemical or biological processes, pressure oxidation, or roasting is typically considered. In the case of refractoriness associated with carbonaceous material, resin-in-pulp (RIP) technology, sometimes with the addition of blinding reagents, is used or alternative lixiviants to cyanide are applied.Ozone can potentially be utilized for preoxidation of refractory ores, thus improving gold recovery and lowering subsequent cyanide consumption. The unique chemical properties of ozone can also potentially be utilized at other stages of gold processing. Ozone can be used for the destruction of free and weak acid dissociable (WAD) cyanide, thiocyanate (SCN), and (partially) strong acid dissociable (SAD) cyanide. Ozone has also been found to show potential for cyanide regeneration from thiocyanate formed during cyanidation of sulphur-containing materials (Botz, 2001).The current paper presents results from a study conducted to evaluate ozonation Evaluation of ozonation technology for gold recovery and cyanide management during processing of a double refractory gold ore by V. Bazhko* and V. Yahorava* The depletion of conventional gold resources around the world has resulted in mining companies and research institutions exploring the recovery of gold from refractory and double refractory ores. However, conventional gold processing routes are not feasible for such deposits due to the low gold recoveries and higher reagent consumptions. A number of technologies have been developed to overcome refractoriness, one of which is ozonation. The unique chemical properties of ozone have been tested successfully on a laboratory scale for the pre-oxidation of refractory ores as well as for the detoxification of cyanide effluent streams. However, ozonation has never been implemented on a commercial scale due to the high capital and operating costs associated with ozone generation. Recent developments in ozone generation and contactor systems have revived interest in ozonation a...