Chemical conversion of recovered carbon black (rCB) from end-of-life tires (ELTs) pyrolysis to reduced graphene oxide (rGO): from waste to advanced materials

Abstract

This study introduces a circular and economic strategy to produce reduced graphene oxide (rGO) from recovered carbon black (rCB). Using a modified Hummers' method followed by chemical reduction of graphene oxide (GO), this approach addresses environmental concerns while offering a cost-effective alternative to conventional rGO precursors. Furthermore, the effects of stirring duration (24 and 48 hours) on the rCB-to-rGO conversion process were examined to optimize production. The rCB-based rGO materials were characterized by N₂ adsorption/desorption, SEM, FT-IR, Raman spectroscopy, TGA, XRD, and XPS. Results showed a notable increase in BET surface area (149 m² g⁻¹) and pore volume (0.350 cm³ g⁻¹) with enhanced thermal stability. SEM analysis confirmed the successful reduction of GO, revealing folded graphene sheets and morphological changes in rCB during the conversion process. FT-IR spectra provided supporting evidence, showing that O–H and C–O vibration modes either disappeared or diminished in intensity after reduction of GO, which was further validated by XPS. Raman spectroscopy results, reflected by increased I_D/I_G ratios (0.982 and 1.017) in rGO samples, indicated the restoration of sp² carbon structures and a reduction in the average sp² domain sizes. XRD analysis clarified the formation mechanisms of various phases during oxidation (MnPO₄·H₂O, MnPO₄·1.5H₂O, Mn, and MnO) and reduction (Mn₃(PO₄)₂·2H₂O, K₃H₃(PO₄)₂, K₂HPO₄, and Mn₂O₃). This research introduces novel insights into the transformative potential of converting rCB into rGO through chemical processes, offering innovative pathways for advancing sustainable material production.