STEP 2 OF 4

Bioleaching

Acid-producing microbes such as Acidithiobacillus ferrooxidans and Gluconobacter oxydans generate organic and inorganic acids that dissolve REEs from pretreated ash. Bioleaching runs under mild conditions and cuts the need for hazardous mineral acids.

• 🧫 Direct leaching: Microbes attach to particle surfaces and release protons and ligands that attack REE oxides.
• 🧪 Indirect leaching: Metabolites such as gluconic and citric acid leach REEs without the cells touching the surface.
• 📈 Efficiency: Around 70% REE recovery within 48–72 h at pH 2.5–4.0 and 30 °C in bench-scale trials.