Pentlandite mineral

Culture-associated nickel mobilization from enriched pentlandite at controlled pH

Experimental Context & Analytical Limits:
Sun et al. used Jinchuan material enriched by flotation and magnetic separation, reagent-cleaned, dried and ground below 0.074 mm. The feed contained 27.43 wt% Ni, 35.13 wt% Fe and 30.79 wt% S, with reported Cu, Mg, Co and Si impurities; it is not assumed to be pure pentlandite. A mixed culture from the National Engineering Laboratory of Biohydrometallurgy, Beijing, was reported initially dominated by Acidithiobacillus ferrooxidans, Ferrimicrobium acidiphilum and Leptospirillum ferrooxidans. No strain identifiers or member-specific activity tests were provided, so no taxon identifiers are assigned to the mixture. Cells grown in ferrous 9K medium were centrifuged in logarithmic growth to limit ionic carryover. The pH-stat assays used 8 g feed in 400 mL sterilized water in 500 mL vessels, 1.5 x 10^6 cells/mL, 33 degrees C and 250 rpm. Sulfuric acid and potassium bicarbonate maintained pH 2.00 or 3.00 within +/-0.05. The paper calls bioleaching tests duplicate but specifies one 8-day and one 16-day run, leaving independent 16-day replication and plotted error-bar meaning unresolved. Samples were taken every two days, filtered at 0.22 micrometre and analyzed by ICP-OES for Ni and total Fe, with Fe(II) titration, XRD, SEM and XPS of residues. Separately, ferric-ion experiments used 3 g feed per 100 mL, initial pH 1, 150 rpm and added kanamycin; those arms are not identical pH-stat microbial controls.

Curated Evidence Points: