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<p>This study proposes a method utilizing high-pressure acid leaching (HPAL) residue, which contains over 40 wt.% iron, for synthesizing battery-grade iron phosphate (FePO<sub>4</sub>)—a precursor material for lithium iron phosphate (LFP) cathodes. The process involves sequential steps: acid leaching to dissolve iron, hydroxide precipitation to remove impurities, FePO<sub>4</sub> precipitation, and acid pickling to eliminate residual impurities. Optimized hydroxide precipitation conditions of pH 3.0, 85 °C, 5% w/v (weight to volume, g/mL) NaOH solution, 60-min reaction time, and 5 mL/min NaOH flow rate achieved precipitation yields of 95.02% for Fe, 20.56% for Al, and 77.6% for Cr. The resulting Fe(OH)<sub>3</sub> precipitate was dissolved and reacted with H<sub>3</sub>PO<sub>4</sub> (Fe/P molar ratio 1:1.1) to precipitate FePO<sub>4</sub>. Under conditions of pH 1.8, 40 °C, 2% v/v NH<sub>3</sub> solution, 10 g/L Fe solution concentration, 10-min H<sub>3</sub>PO<sub>4</sub> addition time, and 1-h precipitation duration, the precipitated FePO<sub>4</sub> initially contained impurities (Al: 0.06 wt.%, Cr: 0.024 wt.%), exceeding standard impurity limits. Subsequent acid pickling with a 0.75 M H<sub>3</sub>PO<sub>4</sub>–0.25 M HCl solution (90 °C, liquid-to-solid ratio of 20 mL/g) effectively purified the FePO<sub>4</sub>, reducing impurity levels to Al: 0.03 wt.% and Cr: 0.001 wt.%, thereby meeting the required standards.</p> Graphical Abstract <p></p>

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Resource Utilization of the Residue from the High-Pressure Acid Leaching of Nickel Laterite for the Production of FePO4

  • 期刊论文

  • 发表日期：

    2025年7月2日

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  • Athhar Izkinal,
  • Wei Liu,
  • Pengyun Xu,
  • Dawei Yu,
  • Xueyi Guo,
  • Qinghua Tian

摘要

This study proposes a method utilizing high-pressure acid leaching (HPAL) residue, which contains over 40 wt.% iron, for synthesizing battery-grade iron phosphate (FePO4)—a precursor material for lithium iron phosphate (LFP) cathodes. The process involves sequential steps: acid leaching to dissolve iron, hydroxide precipitation to remove impurities, FePO4 precipitation, and acid pickling to eliminate residual impurities. Optimized hydroxide precipitation conditions of pH 3.0, 85 °C, 5% w/v (weight to volume, g/mL) NaOH solution, 60-min reaction time, and 5 mL/min NaOH flow rate achieved precipitation yields of 95.02% for Fe, 20.56% for Al, and 77.6% for Cr. The resulting Fe(OH)3 precipitate was dissolved and reacted with H3PO4 (Fe/P molar ratio 1:1.1) to precipitate FePO4. Under conditions of pH 1.8, 40 °C, 2% v/v NH3 solution, 10 g/L Fe solution concentration, 10-min H3PO4 addition time, and 1-h precipitation duration, the precipitated FePO4 initially contained impurities (Al: 0.06 wt.%, Cr: 0.024 wt.%), exceeding standard impurity limits. Subsequent acid pickling with a 0.75 M H3PO4–0.25 M HCl solution (90 °C, liquid-to-solid ratio of 20 mL/g) effectively purified the FePO4, reducing impurity levels to Al: 0.03 wt.% and Cr: 0.001 wt.%, thereby meeting the required standards.

Graphical Abstract