Diatom-based treatment of geothermal brines to selectively remove silicon, retain lithium for downstream recovery, and produce omega-3 fatty acids

Abstract

Summary Silica (SiO2) scaling in geothermal brines processing can hinder energy production and downstream lithium (Li) recovery. Here, we investigate diatom-based selective silicon (Si) removal from brines to support downstream recovery of lithium (Li) and generating biomass for valorization. Screening of six diatom strains identified Halamphora sp. as the most effective for Si removal. When cultivated in geothermal brine supplemented with urea, Halamphora sp. removed 34 mg L−1 of Si (97.14%) within 48 h, while retaining over 99% of Li (75 mg L−1) in solution. Urea supplementation also enhanced biomass production, reaching 0.45 g L−1. The resulting biomass contained the omega-3 fatty acids eicosapentaenoic acid (EPA; 47 mg g−1) and docosahexaenoic acid (DHA; 24 mg g−1). These results demonstrate the potential for coupling biological Si removal and Li retention with production of value-added biomass during geothermal brine processing.