Bioleaching of Enargite/Pyrite-rich “Dirty” Concentrate and Arsenic Immobilization

Naoko Okibe, Kaito Hayashi, Keishi Oyama, Kazuhiko Shimada, Yuji Aoki, Takahiro Suwa, Tsuyoshi Hirajima

Research output: Contribution to journalArticlepeer-review

Abstract

Bioleaching of arsenic (As)-rich, so-called “dirty” concentrates can produce additional Cu value from the flotation waste while simultaneously releasing toxic As. This study bioleached three such concentrates of varying pyrite/enargite ratios ([Py]/[Ena] = 0.7, 1.3 and 2.4) at a pulp density of 20%. The dissolution behavior of Cu and As in relation to the solution redox potential (Eh) was studied with and without activated carbon (AC) as a potential Eh-controlling catalyst. At this high pulp density, Eh was naturally suppressed, without a need for AC dosing, to <700 mV (a rapid pyrite dissolution is prevented in this Eh range). The effect of AC dosing on Eh varied depending on the type of concentrate; Eh was further reduced only in the case of the most enargiterich concentrate, DC-I. Among the three concentrates, the highest Cu dissolution (35%) was seen in DC-I (without AC dosing), which simultaneously achieved the lowest As solubilization. Arsenic was immobilized as amorphous precipitates, likely in a mixture of ferric arsenate, cupric arsenate, basic ferric sulfate and sulfur. Arsenic immobilization became increasingly ineffective as the pyrite content increased in the concentrate. Based on these results, setting a lower [Py]/[Ena] ratio prior to the dirty concentrate bioleaching could be a useful approach to promote Cu dissolution and As immobilization simultaneously.

Original languageEnglish
Article number449
JournalMinerals
Volume12
Issue number4
DOIs
Publication statusPublished - Apr 2022

All Science Journal Classification (ASJC) codes

  • Geotechnical Engineering and Engineering Geology
  • Geology

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