Efficient reuse of anode scrap from lithium-ion batteries as cathode for pollutant degradation in electro-Fenton process: Role of different recovery processes

Abstract

Effective recycling of spent graphite from lithium-ion batteries (LIBs) has a strong application potential. In this research, anode scrap of spent LIBs is efficiently recovered and reused as high-performance cathode in electro-Fenton system. Role of different recovery processes in the reuse of anode scrap powder in electro-Fenton system is focused, including Anode raw powder (RP), acid leaching (AL), acid and alkali leaching (AAL) residual powder. The results indicate functional groups of anode powder are changed by different leaching processes, which can significantly affect the subsequent reuse in electro-Fenton system. According to evaluation by electrochemical characterization, the AAL has a higher hydrogen peroxide (H2O2) selectivity and yield than RP and AL due to highly active two-electron reduction of oxygen (O2). Interestingly, when anode powder is reused in electro-Fenton system, the AL electrode achieves 100% bisphenol A (BPA) removal in 70 min and 87.4% COD removal in 240 min, showing the best degradation efficiency. The reason can be attributed to higher carboxylic group content (35.83%) of AL powder than that of AAL (7%). Thus, part of iron ion in solution can be adsorbed on the surface of AL cathode, forming a partial heterogeneous iron oxidation-reduction. Furthermore, the reusability of AL electrode is evaluated. Compared with other carbon cathode, the AL cathode with a low current density still maintains 100% BPA removal after 10 reuse cycles. Since it is inherent with high reusability and environmental friendliness comparing with traditional cathode materials, this research demonstrates a potentially new approach to cooperatively treat pollutants from solid waste and waste water.