Seyra Toprak joined the CRM-geothermal project during her Master’s studies, where she focused on the recovery of critical raw materials, specifically lithium, from high-salinity geothermal brines using selective adsorption technologies.
Seyra is currently a PhD student at the İzmir Institute of Technology (İYTE) in the Department of Materials Science and Engineering. Her research contributes to the development of sustainable extraction methods for lithium (Li) from geothermal resources in Turkey, specifically at the Tuzla Geothermal Power Plant (TGPP). The main objectives are to evaluate the efficiency of commercially available sorbents, specifically two varieties of Manganese dioxide (γ-MnO₂ and λ-MnO₂), in real-world conditions and to demonstrate a practical pathway for concentrating lithium into a solid precursor (Figure 1).
The approach adopted in her research combines laboratory-scale batch experiments, on-site field tests at the power plant’s reinjection line, and precipitation and purification steps.
Figure 1: Graphical summary of the suggested adsorption technique with Manganese dioxide, which is tested during Seyra Toprak’s work at the Tuzla Geothermal Power Plant.
The field adsorption tests were conducted at the Tuzla Geothermal Power Plant, where the acid-treated sorbent was exposed to a continuous geothermal brine flow at a rate of approximately 30 m³/h. The brine at the site contains a lithium concentration of about 20-25 ppm. Figure 2 illustrates the cumulative enrichment process, where lithium was successfully desorbed and concentrated over multiple successive cycles.
Following the enrichment stage, carbonate-based agents—specifically sodium bicarbonate, sodium carbonate, and ammonium carbonate— were used to selectively remove coexisting ions like Manganese and Calcium without significantly affecting lithium retention. The purification process ensured that the final solution was sufficiently concentrated for the recovery of a solid lithium product.
A key outcome of this work, recently published in ACS Sustainable Resource Management, is the first experimental demonstration of direct lithium peroxide (Li₂O₂) precipitation from geothermal brine. By applying rotary evaporation, a lithium-rich solid with an estimated purity of ~93 wt% was obtained. (Figure 3)
The outcomes of Seyra’s study suggest that geothermal brines in the Tuzla region are a viable and strategic source for lithium recovery, providing a versatile precursor that can be converted into battery-grade materials like lithium hydroxide and lithium carbonate. These results highlight the potential of geothermal brines as a source of lithium.
Seyra Toprak conducted this research under the supervision of Prof. Dr. Mustafa M. Demir (İzmir Institute of Technology).
Figure 2: (a) Enrichment of lithium concentration with repetitive desorption (8 cycles), the inset of the figure shows a representative photograph of a desorption solution. Yellowish color may due to the formation of Mn
Figure 3: Image of the recovered lithium-rich solid obtained after evaporation of the enriched desorption solution (a), XRD pattern of the precipitated powder showing crystalline phase identification (b).
