Recycling spent LiFePO4 battery for fabricating visible-light photocatalyst with adsorption-photocatalytic synergistic performance and simultaneous recovery of lithium and phosphorus

Converting spent LiFePO4 (LFP) battery into photocatalysts is an attractive approach for efficiently enhancing the economic profit of recycling low value-added battery. In the current research, a facile and novel strategy for recycling spent LFP battery to fabricate visible-light photocatalyst (NaFeS2) with adsorption-photocatalytic synergistic ability was developed, and more than 99.9 % Li and P were simultaneously recovered. The synthesized NaFeS2 showed superior adsorption-photocatalytic synergistic capability, which could quickly photodegrade 98 % methylene blue (MB) without pre-adsorption in 20 min (C0 = 20 mg/L, V = 100 mL), and the degradation rate constant of MB by NaFeS2 was 67 times higher than that of TiO2. Mechanisms study demonstrated the enhanced absorption of visible light and efficient charge separation endowed NaFeS2 with outstanding photocatalytic ability. The excellent adsorption capacity of NaFeS2 for MB (129.3 mg/g) was ascribed to the electrostatic interaction between negative S2-/S22- and positively charged MB molecules and coordination interaction between MB molecules and Fe (II)/Fe (III). The synergy of adsorption and photocatalysis shortened the time required for MB to contact with ·O2–, ·OH and h+, increasing the degradation rate of MB. In addition, cycle experiments demonstrated NaFeS2 possessed excellent reusability and stable photocatalytic ability. The current research provides a profitable strategy for recycling low value-added spent LFP battery, and the synthesized NaFeS2 has potential for industrial application in site remediation with serious pollution of organic dyes.