Environmentally Friendly Production of Graphene Oxide via Ball Milling: Characterization and Life Cycle Assessment

This study evaluates the environmental impact and structural evolution of graphene oxide (GO) produced via a sodium sulfate-assisted ball milling method, focusing on the effect of milling duration. Graphite was milled for 6, 12, 18, and 24 h, and the resulting GO samples were characterized using Raman spectroscopy, X-ray diffraction, and scanning electron microscopy to assess defect density, crystallite size, and flake morphology. The 12 h milling duration produced GO with optimal characteristics, including an I_D/I_G ratio of 1.00, an in-plane crystallite size (L_a) of 19.18 nm, and an average flake size of 1.22 ± 0.84 μm. Prolonged milling to 24 h increased the I_D/I_G ratio to 1.22, decreased L_a to 15.71 nm, and reduced the average flake size to 0.53 ± 0.23 μm, indicating higher defect density and material degradation. A cradle-to-gate life cycle assessment (LCA) was conducted to quantify the environmental footprint associated with each milling duration. The 12 h process demonstrated the lowest global warming potential (GWP) at 8.55 kg CO₂-equivalent per kilogram of GO, with electricity consumption and sodium sulfate usage identified as the primary environmental impact contributors. Longer milling durations led to greater environmental burdens without corresponding material improvements. These results suggest that the 12 h milling condition strikes an optimal balance between product quality and environmental performance. This work supports sodium sulfate-assisted ball milling as a scalable and more sustainable alternative to traditional chemical oxidation methods for GO production.