A dual-cycle regeneration to recover high-value and high-purity FePO from real wastewater for Li-battery application.

The recovery of high-purity and high-value FePO raw materials from wastewater has great prospects in LiFePO battery industry due to the huge demand for new energy vehicle. However, the conventional in-situ FePO precipitation, as well as ex-situ PO adsorption-alkali regeneration, was incapable of efficiently obtaining high-purity products. To solve these problems, a dual-cycle regeneration method of Fe-NH-polyacrylonitrile (PAN) adsorbent and HSO desorbing solution was proposed to ex-situ FePO recovery from wastewater for Li-battery application. Benefitted from coordination interaction and electrostatic attraction, the maximum PO adsorption capacity of Fe-NH-PAN reached 73.1 ± 0.4 mg/g. The average PO removal rate of continuous flow devices were 88.5% and 91.3% when treating low-P-concentration (0.22 mg/L) municipal wastewater (MW) and high-P-concentration (48.9 mg/L) slaughterhouse wastewater (SW) respectively. Furthermore, high-purity FePO analyzed by XRD spectra was achieved from the desorption solution at pH ∼1.6, resulting in the ultrahigh P recovery efficiencies of 91.4 ± 3.2%-96.3 ± 2.5% for SW and 82.7 ± 3.5% for MW. Besides, the LiFePO/C electrodes made of recycled FePO exhibited a better discharge capacity (37.3 - 55.8 mAh/g) than that of commercial FePO agent (32.2 - 35.1 mAh/g) from 80 to 132 cycles, which showed the promising feasibility of recovering FePO from wastewater for Li-battery application.