Subgram-Scale Precipitation of Lithium Peroxide from Tuzla Geothermal Brine Using Commercial λ-MnO2 Adsorbent In Situ

Abstract The rapid increase in global demand for lithium emphasizes the importance of developing alternative sources beyond traditional mining. Geothermal brines represent a promising resource for critical raw materials, particularly lithium, owing to their substantial reinjection volumes despite relatively low elemental concentrations. The primary challenge is the development of extraction technologies that are both technically feasible and economically viable. To address this aim, the commercially available spinel-type λ-MnO2 sorbent was applied for lithium recovery. In batch adsorption experiments, λ-MnO2 exhibited a sorption capacity of 22 mg/g. Field adsorption tests were subsequently conducted at the Tuzla geothermal power plant. Lithium was subsequently desorbed using an acidic eluent, and the enrichment process was repeated over five to eight successive cycles. Following selective precipitation with carbonate sources (NaHCO3, Na2CO3, and (NH4)2CO3) for the removal of coexisting ions, lithium peroxide (Li2O2) was successfully obtained in subgram quantities via rotary evaporation, corresponding to an estimated purity of ∼93 wt %. These results demonstrate a practical approach to concentrating lithium from geothermal brine into a lithium precursor ready for further processing, providing a viable pathway for scalable lithium recovery.