Pyrolytic upcycling of plastic waste into graphene and carbon nanostructures

The escalating accumulation of plastic waste poses a significant environmental challenge, while the high cost of graphene production limits its widespread application. Addressing both issues, this study presents a sustainable and efficient approach to upcycle plastic waste into graphene-like carbon nanostructures with tailored morphology. A two-stage catalytic pyrolysis process was employed to convert common plastic wastes— high-density polyethylene, low-density polyethylene, polypropylene, polystyrene, and polyethylene terephthalate—into graphitic nanomaterials and hydrogen-rich gases. To enhance efficiency, bimetallic catalysts (Fe–Ni, Co–Fe, Co–Ni) supported on MgO were synthesized using impregnation and coprecipitation methods. Among these, Fe–Ni–Mg prepared via coprecipitation exhibited the highest catalytic activity, yielding carbon nanomaterials and hydrogen. Polystyrene waste produced the highest yield of graphene-like multiwalled carbon nanotubes, while polyethylene terephthalate was less effective due to its oxygen-rich composition. Structural and morphological analyses confirmed the formation of layered and tubular graphene-like carbon with high surface area. The resulting materials demonstrated excellent adsorption capacities for heavy metal ions, highlighting their potential in wastewater treatment. This study offers a scalable, low-cost solution for plastic waste valorization and graphene synthesis, contributing to environmental remediation and the development of affordable graphene alternatives for industrial applications.