Biooxidation-gold Extraction Technical Study Of High-arsenic Refractory Gold Ore With Different Types

The refractory gold ore is valuable resource and occupies for one third proved reserves. In recent years, many refractory ore are utilized widely and their recovery are improved remarkably because of better pretreatment, especially biooxidation pretreatment. However, the biooxidation problems are still great such as long term, low pulp concentration and slashing demands for the raw materials. The problems are especially evident when the refractory gold ore with arsenic in high content. The gold recovery is low and the resource is wasted badly. Under such a background, two kinds of refractory gold ores and biooxidation mechanisms have been studied in the present work. The influence of As(â…¢) and As(â…¤) in the different arsenic bearing gold ore on bacterial oxidation and gold extraction was investigated. The conclusions are as below.1. First, the biooxidation were compared for the typical associated sulfide ore of refractory gold ore. The results show that bacteria has very different influence on the sulfide ores. The order is pyrrhotite> arsenopyrite> chalcopyrite>pyrite> orpiment> realgar.2. Second, the biooxidation dynamic corrosion was studied for the polished pill of gold-arsenopyrite, polished pill of gold-pyrite and polished pill of arsenopyrite-pyrite. The results show that the leaching bacteria were adsorbed on the surface of pyrite selectively to increase the electrostatic potential difference between pyrite and arsenopyrite. The galvanic cell was formed by arsenopyrite and pyrite in acidity oxidation medium, and the arsenopyrite dissolved rapidly as anode.3. Third, the bacterial oxidation of high arsenic refractory gold mine with different arsenic types shows that arsenic bearing mine is difficult to oxygenolysis when arsenic exists as realgar, while the refractory gold mine is easy to oxygenolysis when arsenic exists as arsenopyrite. HQ-0211leaching bacteria are used to pretreat the high arsenic refractory gold mine of arsenopyrite type and realgar type. The oxidative periods are3d and6d when the pulp concentration is2%, and5d and10d for5%. The period is lOd for the arsenopyrite type high arsenic refractory gold mine when the pulp concentration is10%. HQ-0211leaching bacteria for the realgar are in the lag phase after oxidation for12d which shows bacterial activity is inhibited.4. Fourth, the conditions As3+transforming into As5+were studied in the bacterial leaching process. The results show that the leaching bacteria don’t oxidize As3+to As5+in the culture medium with high concentration Fe3+and high potential. The oxidization occurs only in the coexistence system of sulfide minerals with pyrite and chalcopyrite. The concentration changes of As3+increases and then decrease, and a trend of stable rises for As5+. The change for arsenic phase is AsS2-â†'As3+â†'As5+. The bacterial activity is improved along with concentration decrease of As3+in the leaching process. A small amount of H2O2and2were added to improve the transfer from As3+to As5+in the initial stage of bacterial oxidation when the concentration of As3+is high. The bacterial activity and dearsenic efficiency were also improved.5. Fifth, it is analyzed the influence of As3+and As5+in the different arsenic bearing ore on the cyanidation extraction and thiourea extraction. In the cyanidation extracting process, realgar is decomposed easily, the leaching efficiency is improved and depletion of CN-is improved. But the arsenopyrite is very stable in the cyanidation extracting process. The oxidation of gold-arsenopyrite is improved to liberate or exposure gold grain in the pretreatment process. The realgar and arsenopyrite are oxidized easily in the thiourea extracting process. But the increase of thiourea amount has lesser effect on the efficiency of thiourea leaching. As+and As+had no influence on the gold leaching because they don’t cooperate with cyanogen and thiourea. The gold extracting efficiency of normal cyanidation extraction and thiourea extraction are34.57%and35.42%for DS arsenopyrite type of high arsenic refractory gold ore. The gold recovery is95.17%and90.07%after cultured bacterial oxidation pretreatment by HQ-0211bacteria. The gold extracting efficiency of normal cyanidation extraction and thiourea extraction are41.28%and46.85%for XH arsenopyrite type of high arsenic refractory gold ore. The gold recovery is93.22%and87.90%after cultured bacterial oxidation pretreatment by HQ-0211bacteria.6. Finally, it is studied for the wastewater cycle in the bacterial oxidation-cyanidation leaching process. The results show that small amount of SCN-still exists in the wastewater affects the cycle after the water is purified. The leaching bacteria are very sensitive for SCN" in the cyanidation wastewater.0.06g-L-1SCN-extends the lag phase and0.1g-L-1restricts the growth. H2O2owns perfect results and40mL·L-1(30%) removes SCN-in the wastewater.