Fluoride species conversion-enhanced selective extraction: A green and safe strategy for fluorine recovery in wet-process phosphoric acid production

Fluorine (F) is a valuable by-product in wet-process phosphoric acid (WPA) production, yet its recovery ratio remains below 60 % due to challenges in purification and utilization. Traditional stripping methods release toxic and corrosive fluorine vapors, endangering production safety. Herein, a novel strategy of Fluoride Species Conversion-Enhanced Selective Extraction (FSC-SE) was put forward for the efficient and environmentally friendly recovery of fluorine from wet process phosphoric acid (WPA). By converting HF and H 2 SiF 6 into HBF 4 through the addition of boric acid, the extraction efficiency of fluorine is significantly enhanced, reaching up to 99.8 % using trioctylamine (TOA) as the extractant. Theoretical calculations were carried out to provide a predictive framework for the extraction selectivity of TOA for different acidic species. Key operation parameters, including B:F molar ratio, TOA concentration, extraction time, and temperature, etc, are, optimized to further enhance the process performance. Subsequent water washing and back-extraction steps enabled effective P-F separation and extractant regeneration. Applied to industrial WPA, the single-stage fluorine extraction efficiency can reach 82.4 %, and the total fluorine recovery ratio can reach 80.4 %. FSC-SE provides a safe, efficient, and environmentally friendly method with strong industrial application potential, highlighting the value of the green separation process combining chemical conversion and solvent extraction in the phosphoric acid industry.