Application of a Zirconium-Titanium Phosphate-Phosphonate Composite Sorbent for Purification of Lithium-Rich Eluate Obtained by Direct Lithium Extraction Technology.

Direct lithium extraction (DLE) represents an emerging technology with considerable potential for lithium recovery from low-grade brines. Nonetheless, DLE still faces several unresolved challenges, particularly concerning the purity of the resulting lithium eluates. The DLE eluate obtained in this study contained approximately 3600 mg/L Li, 2350 mg/L Ca and 1200 mg/L Na. Sorbent-based purification is regarded as one of the most efficient methods for eluate treatment. Among sorbents, titanium phosphates, zirconium phosphates, and zirconium aminotris (methylenephosphonates) are known for their high sorption capacities toward various metal ions. Therefore, this study aimed to develop a zirconium-titanium phosphate-phosphonate sorbent capable of removing impurities from DLE eluates. As a result, a novel powdered ZrTiPO4-ATMP sorbent was synthesized under mild conditions. Subsequently, a granular composite sorbent, ZrTiPO4-ATMP@PVDF, was prepared using PVDF as a binder. The obtained materials were characterized using XRD, FTIR, SEM-EDS, CHN analysis, and BET analysis. The sorption performance of the composite material was evaluated during the purification of eluates obtained from real oilfield brine. Under optimal conditions, calcium and magnesium removal efficiencies exceeded 95%, while sodium removal reached 60%. At the same time, lithium losses remained below 20%. These losses can be further minimized by returning the regeneration solution to the sorption step.