An Integrated Precipitation–Electrodeposition–Electrodialysis Strategy for Efficient Close-Loop Recovery of Multiple Anions from Phosphogypsum Leachate

Abstract

The high concentration anions, including fluoride (F^–), phosphorus (PO₄^3–), and sulfate (SO₄^2–), in phosphogypsum (PG) leachates from various landfill sites raise significant environmental concerns. Herein, we propose a combined strategy with chemical precipitation, electrodeposition, and electrodialysis for efficient close-loop recovery of these anions. This approach enabled a recovery rate of 95% for F^–, 99% for PO₄^3–, and 99% for SO₄^2– with the resulting obtained products of AlF₃/Ca₅(PO₄)₃F/AlPO₄, Co₃(PO₄)₂, and Na₃FSO₄/Na₂SO₄/CaSO₄. Via this process, the concentrations of F^–, PO₄^3–, and SO₄^2– anions in the effluent were lowered down to 0.14, 0.37, and 0.51 mg·L^–1, respectively, meeting the water discharge standards set by the phosphate fertilizer industry in China (F^– < 15 mg·L^–1, TP < 10 mg·L^–1). Economic analysis indicated that processing 1 ton of PG leachate can yield a net profit of $4.62. Our proposed innovative closed-loop process not only provides a green and sustainable approach to treating the huge amount of PG leachates and properly addressing the global PG pollution problem but also offers valuable insights on the sequence recovery of multiple anions in PG leachates.