G.P. Katz, M.R. Pavia, J. Clarke
Katz Water Technologies, Inc.,
Keywords: direct lithium extraction (DLE), geothermal brines, microbial biosorption
Summary:Katz Water Technologies (KWT) is developing its microbial biosorption process to enable the recovery of lithium and other critical minerals and materials from geothermal brines. Lithium, the lightest metal, is in rising demand for its role in electrification, but the existing direct lithium extraction (DLE) technologies required for stable domestic supply are far from break-even. Microorganisms are widely reported in the literature to adsorb metals from wastewater, and in-house lab testing at KWT has shown that culturing the organisms is simple and low-cost1,3,6. See Table 1 for list of specific microorganisms. KWT intends to test these microbes' adsorption capacity, selectivity, recyclability, and operating life for viability in DLE processes. Though currently at the laboratory scale, successful integration of biosorption into KWT’s X-VAP thermal desalination process would facilitate low-cost ion exchange and dewatering, surmounting a pair of hurdles for DLE processes. See figures 1(a) and 1(b). More specifically, oil and gas produced water and geothermal brines have conventionally been treated via evaporation, disposal, or some combination. DLE has leveraged expensive cutting-edge adsorbents, membranes, electrolyzers, and ion-exchange (IX) resins. Thus far, KWT has pioneered in the field of oil and gas produced water treatment2 with the X-VAP, which can recover over 50% of water from high salinity oil and gas produced water brines, with minimal specific energy use4. Following the success of the X-VAP, KWT aims to similarly disrupt CMM production by developing biosorbents into a low-cost alternative to other pre-treatment methods such as IX. This same technology can be applied to geothermal brines See figures 2(a) and 2(b). Cell surface sorption functions as an ion exchange mechanism at the molecular scale. Carbonyl, hydroxyl, phosphate, and other functional groups on microbial cell walls exchange hydrogen ions for metal ions, which can be controlled using pH. As shown in figure 1(a), acid-regenerative biosorption using bacteria, yeasts, or algae can replace expensive pre-treatment IX processes. Though the literature reports direct lithium biosorption, as biosorbent affinity correlates with hydrated radius, we predict high metal-lithium selectivity ratios. Thus, the biosorbent will adsorb larger heavy metals and divalent cations, leaving sodium-lithium chloride. The product is then dewatered using the X-VAP to form a concentrate, which can be further processed to produce LiCO3. See figure 3. Biosorption is well-demonstrated to equilibrate quickly, but the degree to which this exchange occurs, and the selectivity of different biomaterials for lithium, are currently being studied in free cells and validated in our lab6. As microbial sorption is a biologically diverse process, it is necessary to test a variety of species to discover optimal characteristics. KWT intends to (1) acquire and (2) grow favorable microorganisms to (3) validate their affinity for CMM, then (4) evaluate selectivity, recyclability, desorption, and run experiments to optimize process parameters. All work, including brine concentration, adsorption experiments, immobilization, techno-economic analysis, and plant design, will be completed by KWT and academic partners. The final deliverable of this project is a pilot plant design suitable for field validation prior to commercialization.