New insights into the extraction of invisible gold in a low-grade high-sulfur Carlin-type gold concentrate by bio-pretreatment

• Published in: 矿物冶金与材料学报：英文版 Vol. 24; no. 10; pp. 1104 - 1111
• Main Author: Xiao-bin Qiu;Jian-kang Wen;Song-tao Huang;Hong-ying Yang;Mei-lin Liu;Biao Wu
• Format: Journal Article
• Language: English
• Published: 2017
• Subjects: analysis; bio-pretreatment; carbonaceous; gold; invisible; liberation; matter; mineralogy; ore; product; secondary
• ISSN: 1674-4799

To extract gold from a low-grade (13.43 g/t) and high-sulfur (39.94wt% sulfide sulfur) Carlin-type gold concentrate from the Nibao deposit, Guizhou, a bio-pretreatment followed by carbon-in-pulp (CIP) cyanide leaching process was used. Various methods were used to detect the low-grade gold in the concentrate; however, only time-of-flight secondary-ion mass spectrometry (TOF-SIMS) was successful. With bio-pretreatment, the gold recovery rate increased by approximately 70.16% compared with that obtained by direct cyanide leaching of the concentrate. Various attempts were made to increase the final gold recovery rate. However, approximately 20wt% of the gold was non-extractable. To determine the nature of this non-extractable gold, mineralogy liberation analysis (MLA), formation of secondary product during the bio-pretreatment, and the preg-robbing capacity of the carbonaceous matter in the ore were investigated. The results indicated that at least four factors affected the gold recovery rate: gold occurrence, tight junctions of gold-bearing pyrite with gangue minerals, jarosite coating of the ore, and the carbonaceous matter content.