Bioleaching of lithium from jadarite, spodumene, and lepidolite using Acidiothiobacillus ferrooxidans

Abstract

Lithium (Li) is becoming increasingly important due to its use in clean technologies that are required for the transition to net zero. Although acidophilic bioleaching has been used to recover metals from a wide range of deposits, its potential to recover Li has not yet been fully explored. In this study, we used a model Fe(II)- and S-oxidising bacterium, Acidiothiobacillus ferrooxidans (At. Ferrooxidans), to extract Li from three different minerals and kinetic modelling to predict the dominant reaction pathways for Li release. Bioleaching of Li from the aluminosilicate minerals lepidolite (K(Li,Al)₃(Al,Si,Rb)₄O₁₀(F,OH)₂) and spodumene (LiAl(Si₂O₆)) was slow, with only up to 14% (approximately 12 mg/L) of Li released over 30 days. By contrast, At. ferrooxidans accelerated Li leaching from a Li-bearing borosilicate clay (jadarite, LiNaB₃SiO₇OH) by over 50% (over 120 mg/L) in 21 days of leaching, and consistently enhanced Li release throughout the experiment compared to the uninoculated control. Biofilm formation and flocculation of sediment occurred exclusively in the experiments with At. ferrooxidans and jadarite. Fe(II) present in the jadarite-bearing clay acted as an electron donor. Chemical leaching of Li from jadarite using H2SO4 was most effective, releasing approximately 75% (180 mg/L) of Li, but required more acid than bioleaching for pH control. Kinetic modelling was unable to replicate the data for jadarite bioleaching after primary abiotic leaching stages, suggesting additional processes beyond chemical leaching were responsible for the release of Li. A new crystalline phase, tentatively identified as boric acid, was observed to form after acid leaching of jadarite. Overall, the results demonstrate the potential for acidophilic bioleaching to recover Li from jadarite, with relevance for other Li-bearing deposits.

Keywords: bioleaching; critical minerals; iron bio-oxidation; lithium; metal recovery.

Figure 1

Lithium (A), boron (B), calcium (C), and iron (D) concentration during jadarite bioleaching (black circles), negative control (red squares), and acid leaching (green triangles). The results shown were obtained after subtracting the initial concentrations present in the basal medium. The error bars show standard error. Negative controls were not inoculated with At. ferrooxidans, and sulphuric acid leaching contained only 2,500 μL H₂SO₄.

Figure 2

(A) Untreated ground jadarite sediment before exposure to the acidic basal medium and bacteria. (B) Jadarite sediment after bioleaching with flocculation, intact bacterial cells, and biofilm are indicated by the red arrow and label.

Figure 3

Powder XRD on a normalised intensity graph between 2θ = 0 ° and 2θ = 70 °. (A) Jadarite before leaching. (B) Jadarite post bioleaching. (C) Uninoculated cell control. Points labelled ‘jad’ indicate jadarite-related peaks, ‘dol’ indicates dolomite, ‘prob’ indicates probertite, and the new mineral phase was labelled.

Figure 4

Spodumene bioleaching (black circles), negative control (red squares), and acid leaching (green triangles) results (A): lithium. (B): iron. The error bars show standard error. Negative (acidic) controls were not inoculated with At. ferrooxidans. Negative controls were not inoculated with At. ferrooxidans, and the sulphuric acid leaching contained only 2,500 μL H₂SO₄.

Figure 5

Lepidolite bioleaching (black circles), negative control (red squares), and acid leaching (green triangles) results (A): lithium. (B): iron. Error bars showing standard error. Negative controls were not inoculated with At. ferrooxidans and sulphuric acid leaching contained 2,500 μL H₂SO₄ only.

Figure 6

Lithium extraction yields (%) during bioleaching of jadarite (orange circles), spodumene (blue circles), and lepidolite (purple circles) from averages of triplicate experiments. The experiments were kept static at 23°C for over 30 days. The error bars represent averages across triplicate experiments.

Figure 7

Linear regression of the chemical shrinking core model for the leaching of Li from lepidolite via (A) bioleaching R² = 0.74, (B) uninoculated control R² = 0.72 and (C) sulphuric acid leaching R² = 0.93. Linear regression of the chemical shrinking core model for the leaching of Li from spodumene via (D) bioleaching R² = 0.74, (E) uninoculated control R² = 0.23, and (F) sulphuric acid leaching R² = 0.90. Linear regression of the chemical shrinking core model for the leaching of Li from jadarite via (G) bioleaching R² = 0.93, (H) uninoculated control R² = 0.95, R² = 0.98 and (I) sulphuric acid leaching R² = 0.98, R² = 0.21. The black circles represent bioleaching reactions, the red squares represent uninoculated controls, and the green triangles represent acid leaching.