Recovery of “pure” CuS nanoparticles using biogenic H₂S from a bioleach liquor

Here we describe the bioleaching of a sulfide ore using a consortium with moderately thermophilic acidophiles in stirred reactors between 37 and 45 °C. The most effective extraction for copper was achieved at 42 °C, with ∼51 % within 30 days at pH 1.8. Microbial diversity showed that the consortium was dominated by the genera Sulfobacillus, Leptospirillum, Acidibrevibacterium, Acidithiobacillus. Pregnant leach solution (PLS) obtained at 42 °C was filtered and transferred into a second vessel to increase the pH to 3.5 with NaOH to promote the precipitation of ferric iron. The iron-free PLS was contacted with biogenic H₂S produced by a low pH sulfidogenic bioreactor. Scanning electron microscopy images of the particles showed spherical-like shapes with a ∼60 nm of diameter and energy-dispersive X-ray analysis demonstrated that the composition was mainly Cu and S. X-ray photoemission spectroscopy analysis showed that the main contribution was associated to CuS bonds, confirming the recovery of “pure” and valorous CuS nanoparticles by using a combination of two bioprocesses at low pH.