Decomposition of carbon fiber-reinforced plastic resins using persulfate for carbon fiber recycling

Carbon fibers are valued for their high strength, low weight, and chemical stability, making them essential in the aerospace, automotive, and energy sectors. However, current recycling methods often degrade fiber quality or limit reuse, particularly for continuous fibers. To address this, we developed the “electrolytic sulfuric acid method,” which uses oxidative active species—peroxomonosulfate and peroxodisulfate—generated by sulfuric acid electrolysis to selectively decompose resin in waste CFRP into CO₂ and water, thereby enabling the recovery of continuous carbon fibers. This study investigates changes in the concentrations of oxidative species during epoxy resin decomposition and analyzes the reaction using Arrhenius plots. The activation energy was determined to be 52.9 kJ/mol for electrolytic sulfuric acid, 40.9 kJ/mol for a 4:1 mixture of 60 wt% electrolytic sulfuric acid and 30 wt% hydrogen peroxide, and 63.1 kJ/mol for a similar mixture prepared with non-electrolyzed sulfuric acid. All these values were significantly lower than those for combustion-based decomposition. These findings demonstrate that the electrolytic sulfuric acid method enables efficient, low-energy decomposition of CFRP resin. Furthermore, the highly oxidative liquid produced by sulfuric acid electrolysis is already widely used in industrial applications. Continued research on resin decomposition using these oxidative active species is expected to advance sustainable carbon fiber recycling technologies and facilitate their implementation in key industries. This method offers a promising solution to the growing demand for environmentally responsible recycling of high-performance composite materials.