Recycling of waste rubber: Method summary and prospect outlook

Waste rubber accumulation has triggered a worldwide “black pollution” issue. Waste tires, featured by huge yield and stable cross-linked networks, are particularly crucial for resource recycling and sustainable development. The three-dimensional cross-linked structure endows vulcanized rubber with excellent service performance, yet seriously restricts its desulfurization and reprocessing capability. Herein, six mainstream desulfurization technologies are systematically reviewed, including twin-screw extrusion thermomechanical desulfurization, desulfurizer-assisted desulfurization, microwave desulfurization, supercritical fluid desulfurization, dynamic network reconstruction, and microbial desulfurization. Among them, twin-screw extrusion desulfurization is the most industrialized route owing to its superior continuity and scalability. By contrast, supercritical fluid technology, biological treatment, and dynamic network construction provide innovative directions for high-value utilization of waste rubber. Nevertheless, critical challenges still remain in current practices, such as rough classification of waste rubber, insufficient comparative evaluation of different technologies, and restriction in high-end applications. Future research should focus on establishing a refined classification system, breaking through the bottlenecks of efficient desulfurization and performance recovery, and expanding high-value application scenarios, so as to strongly support the green recycling and circular economy development of waste rubber.