Constructing magnetically separable manganese-based spinel ferrite from spent ternary lithium-ion batteries for efficient degradation of bisphenol A via peroxymonosulfate activation

A magnetically separable manganese-based spinel ferrite (MFO-LIBs) is synthesized using spent ternary lithiumion batteries (LIBs) for the first time. The ferrite is used to activate peroxymonosulfate (PMS) for the degradation of bisphenol A (BPA), thus meeting the strategy of "treating waste with waste." Surprisingly, its degradation activity was 2.8 times that of pure MnFe2O4 (MFO). The characterization of the structure and morphology confirmed that the metals (e.g., Ni and Co) in spent ternary LIBs are doped into MFO, leading to MFO-LIBs with a larger specific surface area (1.3 times that of MFO) and a higher ratio of Mn(II)/Mn(III) (1.4 times that of MFO) and Fe(II)/Fe(III) (1.3 times that of MFO). Electron paramagnetic resonance and quenching experiments confirmed that surface-bound SO4 center dot-, surface-bound center dot OH, O-2(-center dot) and (1) O-2 are the main reactive oxygen species (ROS) in BPA degradation. Simultaneously, the improved degradation activity of the MFO-LIBs/PMS system can be ascribed to the increase in the number of ROS rather than the change in ROS types. Its outstanding performance can be maintained despite the high-salinity conditions (e.g., Cl, HCO3 and H2PO4), high content of humic acid and alkaline conditions. MFO-LIBs can be easily separated in the presence of an external magnetic field and has excellent universality (toward bisphenol F, 2,4-dichlorophenol and 2,4,6-trichlorophenol) and regeneration ability. More importantly, the cost of BPA degradation in the MFO-LIBs/PMS system is much lower than that of the related spinel ferrite activator/PMS systems (e.g., CoFe2O4/PMS and MnF(e)2O(4)/PMS systems).