Combination of membrane technologies for the co-production of a solid lithium product and low salinity water from natural brines

Natural lithium-rich brines are currently processed through solar evaporation, a slow and water-intensive methodology associated with significant environmental concerns, in addition to technical inefficiencies due to 1 year residence time for the brines in solar evaporation ponds. In this work, two integrated membrane-based process configurations were evaluated for the co-production of a pure lithium solid, lithium phosphate, and low-salinity water from a natural lithium brine. The proposed flowsheets combined membrane electrolysis (ME), membrane distillation-crystallization (MDCr), and lithium phosphate precipitation, differing only in the sequence of the ME and MDCr stages. Specifically, MDCr enabled rapid brine concentration while simultaneously recovering low-salinity water, whereas ME effectively removed divalent cations that interfere in the final lithium salt purification. In both configurations, MDCr achieved stable permeate fluxes of approximately 2.7–2.8 kg m −2 h −1 and recovered over 80% of the original brine water content in less than 5 h of operation. The overall flowsheet from raw brine to the final dry Li 3 PO 4 product can be completed in 8 days. Lithium concentration increased by a factor of 4.3, while NaCl was selectively crystallized during MDCr with purity levels close to 99%. Subsequent precipitation with sodium phosphate enabled the recovery of Li 3 PO 4 as the final solid product with low impurity levels after minimal washing. Processing the concentrated brine by ME after MDCr resulted in lower energy consumption, more efficient Ca 2+ removal, and improved permeate quality compared to pre-treating the raw brine prior to concentration. The results demonstrate the feasibility of combining membrane technologies for accelerated lithium brine processing with simultaneous freshwater recovery, representing a promising alternative to the conventional evaporatic method.