Technical and Life Cycle Assessment of Carbon Nanomaterial Production From Waste Toner Using Valorized Toner Ash and Magnetite Tailing Supports

Industrial waste streams, such as magnetite tailings (MTs) from ore processing facilities and toner ash (TA) from electronic waste, are increasingly posing a significant threat to the environment due to inadequate disposal methods. This study presents a sustainable valorization strategy, transforming these wastes into catalyst supports for the synthesis of carbon nanomaterials (CNMs). Nickel-based catalysts supported on TA and MTs were synthesized and assessed for CNM production. High-resolution transmission electron microscopy (HRTEM) analysis showed that optimal TA loading facilitated the growth of multi-walled carbon nanotubes (MWCNTs) with uniform diameters of 40–50 nm, whereas higher TA concentrations resulted in mixed CNM morphologies. Similarly, MT-supported catalysts produced MWCNTs with unusual morphologies, alongside carbon nanofibers (CNFs) and carbon nano-onions (CNOs). This study used selected area electron diffraction (SAED) to interpret the formation mechanisms of CNMs, identifying that Fe3C facilitated the formation of diverse CNMs through the reshaping of molten catalysts, whereas metal disilicides inhibited the growth of CNMs. Life cycle assessment (LCA) has shown significant benefits from upcycling waste toner, notably reducing human toxicity potentials compared to traditional incineration. The most significant environmental benefits are associated with the production of MWCNTs using TA or MTs as a partial catalyst, with renewable energy serving as an the electricity source. This approach converts hazardous waste into valuable CNMs, promoting circular economy principles by minimizing landfill waste and facilitating cost-efficient production of nanomaterials.