Upcycling of Battery Separator Waste into High-Value Carbon Materials for Efficient Industrial Pollutant Adsorption

Battery separators are primarily composed of polyethylene (PE) and polypropylene (PP). Due to their high thermal stability and strong carbon–carbon bonds, they are challenging to carbonize, often decomposing completely into volatile hydrocarbon molecules during direct pyrolysis. To address this, a urea-assisted pyrolysis strategy was employed to upgrade waste battery separators into nitrogen (N) and oxygen (O)-doped high-value carbon materials. The study revealed that the N,O-doped pyrolytic carbon is rich in C═O/C═N and C–O/C–N bonds, enabling an exceptional adsorption capacity of methylene blue (MB) of up to 330.77 mg/g. The adsorption process conformed to the quasi-second-order kinetic model, and the isothermal adsorption data fitted the Langmuir model, indicating a monolayer adsorption behavior. The primary mechanisms for MB adsorption by the pyrolytic carbon include pore filling, electrostatic neutralization, surface charge redistribution, functional group interactions, electrostatic attraction, π–π interactions, and hydrogen bond formation. Overall, the pyrolytic carbon prepared in this study exhibits significant advantages: the raw material is waste separators, and the synthesis process is simple, low-cost, and environmentally friendly. As an economical and efficient adsorbent, the pyrolytic carbon demonstrates promising application potential and prospects.