Extraction of Lithium from High-Sodium Wastewater Based on DBM/TBP Technology

A method for selectively extracting lithium from lithium sulfate solution is proposed by using a synergistic DBM/TBP extraction system and employing linear analysis and DFT calculations to explore the synergistic extraction mechanism of lithium. The experimental results showed that, for a simulated solution containing 2.0 g/L lithium and 50 g/L sodium, and 0.5 mol/L DBM + 1 mol/L TBP + sulfonated kerosene as the organic phase, at an O/A phase ratio of 1:1, an equilibrium pH of 13, a temperature of 25°C, and a reaction time of 3 min, the single-stage extraction rate of lithium reached 94.5%, with a βLi/Na ratio of 210. Through three-stage simulated countercurrent extraction under an O/A phase ratio of 1:3 and an equilibrium pH of 13, more than 99% of the lithium was extracted. Washing with 0.5 mol/L H₂SO₄ at a phase ratio of 2:1 removed nearly 98% of the sodium. After washing, the loaded organic phase was subjected to three-stage countercurrent re-extraction using 1.5 mol/L H₂SO₄ under an O/A phase ratio of 3:1, achieving a lithium re-extraction rate greater than 99%. The DBM/TBP synergistic extraction system can effectively selectively recover lithium from lithium sulfate solution, achieve deep separation of lithium and sodium, and achieve high-concentration recovery of lithium.