Recycling of lithium and fluoride from LiF wastewater from LiF synthesis industry by solvent extraction

The LiF synthesis industry produces a large amount of wastewater that contains ∼0.36 g/L lithium and ∼1.10 g/L fluorine. The traditional treatment solidified fluoride by excessive CaO, resulting in waste of lithium resources and generation of CaF2-CaO solid waste. To recover the Li and F from the LiF wastewater, a two-section solvent extraction process using acidic solvent and mixed solvent as organic solvent was designed and the extraction mechanism were systematically investigated. The result showed that Li extraction was extracted by a cation exchange mechanism with D2EHPA (di-2-ethyl hexyl phosphoric acid), 99.72% Li recovery and battery-grade LiCl solution (3.40 g/L) were achieved by mixed the LiF aqueous with the saponified D2EHPA at 25 ℃ for 6 mins with 4.60 equilibrium pH. After then, F was recovered by mixed neutral solvent system, which coordination binding with HF molecule. The ultimately residue contains ∼1 mg/L Li and < 6 mg/L F. Besides, high-purity LiF products (LiF>99.95%) was generated by stripping with LiOH, F recovery is 99.45%. 2-stage extraction process realizes lithium and fluoride recovery with short process, no pollution and great prospect of industrialization.