Fluoride toxicity in a chalcocite bioleach heap process

Assessing metal recovery from low-grade copper ores containing fluoride

“…In the experimental conditions of the present work and for the aluminium/fluoride ratio that enabled bacterial growth (Al/F = 1.4), AlF 2+ represented 45.5% whereas AlF 2 + species account for 12.0% and AlSO 4 + , for 27.6% of the fluoride-containing species in the system. The predominance of AlF 2+ is consistent with the findings of Brierley and Kuhn (2010). Nevertheless, HF is the species that affects bacterial growth.…”

“…While S. thermosulfidooxidans can tolerate up to 3 g/L Cl − (Gahan et al, 2009), fluoride is specially of concern as it predominates as HF at the given pulp pH, which can cross cell membranes and lower internal cell pH (Suzuki et al, 1999). Actually, the presence of fluoride containing-minerals accounted for the failure of an industrial bioleaching operations (Brierley and Kuhn, 2010). In the present work, chemical analysis showed that chloride concentrations in solution were lower than 60 mg/L, which is not detrimental to S. thermosulfidooxidans growth; however, fluoride concentrations reached 270 mg/L and 153 mg/L, for both the highcopper and the low-copper ore, respectively.…”

“…Fluoride ions toxicity on bacterial growth can be overcome by the presence of soluble aluminium in the leaching systems (Brierley and Kuhn, 2010;Dopson et al, 2008;Sundkvist et al, 2005). This is because a series of strong complexes with the general formula [AlF n ] 3-n , is formed by the two species, thereby reducing both the free fluoride and HF concentrations.…”

Microbiological Advances in Biohydrometallurgy

“…Concentrations of fluoride higher than 0.5 g¨L´1 are detrimental to microbial growth [69], potentially making fluoride in heap process water a greater challenge than chloride. A case in point was a chalcocite heap for which the failure to reach design recoveries was partly attributed to the failure to test the solubility of fluoride-containing minerals in the ore [77]. In that study, concentrations of iron-oxidizing microorganisms were lower than is typical for sulfide heap leaching, diminishing from the critical concentration of 10 5 cells¨mL´1 [78] to 10 3 cells¨mL´1 within a year.…”

Biolixiviação de cobre a partir de rejeito de processo de flotação de calcopirita empregando consórcio de microrganismos.

“…sulfetos minerais. Foi demonstrado que entre os efeitos da dissolução de minerais silicatados para a biolixiviação estão o aumento do pH, a liberação de elementos traços tóxicos em solução (como o fluoreto), o espessamento do licor de lixiviação por altas concentrações de sílica e a passivação de minerais de sulfetos pela formação de precipitados de ferro (RAZZELL;TRUSSELL, 1963;ANDERSEN;LUNDGREN, 1969;PIETROBON et al, 1997;LÖVGREN;BOSTRÖM, 2008;WU et al, 2009;BRIERLEY;KUHN, 2010) Dong et al (2011). realizaram experimentos de biolixiviação de cobre a partir de rejeitos e observaram aumento do pH e consequente diminuição da extração de cobre, devido ao consumo rápido de ácido por minerais de ganga como carbonatos (calcita, dolomita e augita) e silicatos (quartzo).…”