Biohydrometallurgical Gold Extraction from Carbonaceous Pyrite-arsenopyrite Concentrate by the Microorganisms Including Moderate Thermophilic

摘要

Biohydrometallurgical studies were performed on the sulfide gold-arsenic concentrate obtained in treatment of refractory ore from a deposit located in northern Russia. Gold is disseminated in sulfides-arsenopyrite, pyrite and antimonite (their content is 10.0%, 30.4% and 0.7%, respectively).Gold extraction is only 11.8% by cyanidation. Results are given for test bacterial oxidation of the concentrate in continuous mode at temp. = 28～32°C using mesophilic bacteria and at temp. =32～38°C using the association including moderate thermophilic bacteria. The paper shows that the use of moderate thermophilic bacteria allows to speed up sulfide biooxidation and reduce its time to 96 hours compared to leaching at temp. = 28～32°C for 110～120 hours. The optimal range of pH =1.5～2.0 of biooxidation process was determined where bacterial solutions are produced with the molar ratio Fe:As＞3 necessary for precipitation of hard-to-solve, environmentally safe arsenical precipitates. Electron microscopy showed that sulfide biooxidation results in liberation of disseminated gold with nanoparticle-level sizes. High sorptive activity of carbonaceous matter and other compounds of bacterial residues cause low gold extraction into cyanide solution 28.7%. 10% resin load makes it possible to extract 88.1% Au. Aeration of pulp in calcareous medium enhances extraction to 95.7% and decreases cyanide consumption from 17kg/t to 8 kg/t.The developed environment-friendly biohydrometallurgical technology of refractory concentrate treatment have used in design of an industrial plant.