A universal photothermal recycling platform for converting diverse plastics into monomers using porous carbon aerogels

Background

The field of plastic recycling has become increasingly important due to the growing environmental concerns associated with plastic waste accumulation and the limitations of landfill and incineration as disposal methods. Mechanical recycling, the most widely used approach, involves physically reprocessing plastics into new products. However, this method is hampered by the presence of mixed or contaminated polymers, which often results in recycled materials of inferior quality and limited applicability. As a result, there is a pressing need for more advanced recycling technologies that can efficiently convert diverse plastic waste streams into valuable raw materials, thereby supporting a circular economy and reducing the environmental impact of plastic pollution.

Current chemical recycling methods, which aim to break plastics down into their constituent monomers, face several significant challenges. Many of these processes are highly specific, requiring tailored conditions or catalysts for each type of polymer, and often necessitate extensive preprocessing such as sorting, cleaning, or premixing with chemical agents. Pyrolysis, a commonly used chemical recycling technique, typically operates at high temperatures and produces a complex mixture of products, including unwanted byproducts, due to non-selective thermal degradation. These limitations hinder the scalability, efficiency, and economic viability of chemical recycling, especially for post-consumer plastics that are heterogeneous and contaminated. As a result, there is a critical need for a universal, selective, and scalable solution that can process a broad range of plastics with minimal preprocessing and high yield of valuable monomers.

Technology

This technology is a universal chemical recycling solution that employs a hierarchically porous carbon aerogel (HPC) as a photothermal agent to depolymerize a wide range of plastics into their original monomers. The process is conducted in a vacuum-sealed reaction chamber where plastic waste is placed directly atop the HPC and irradiated with LED light. The HPC efficiently converts the light into localized heat, causing the plastic to melt and wick into its interconnected pores. Within these pores, the plastic undergoes depolymerization, producing gaseous monomers that are subsequently captured in a collection flask. The system is notable for not requiring any premixing of the photothermal agent with the plastic, and it is effective for various polymers—including polystyrene, polyolefins, and polyesters—while maintaining high selectivity and enabling the reuse of the aerogel material for multiple cycles.

What differentiates this technology is its broad applicability, operational simplicity, and sustainability. Unlike traditional recycling methods that often require extensive preprocessing or are limited to specific polymer types, this approach can handle mixed and post-consumer plastics in diverse forms without prior treatment. The use of HPC, derived from renewable egg white proteins, not only provides a sustainable material source but also offers tunable porosity for optimal performance. The photothermal process allows for precise control over depolymerization conditions, reducing unwanted byproducts and achieving high monomer yields. Additionally, the reusability of the HPC and the scalability of the system—achieved by adjusting the irradiation area and aerogel volume—make it a promising candidate for industrial-scale, closed-loop plastic recycling, addressing both environmental and economic challenges in the plastics lifecycle.

Benefits

• Enables chemical recycling of a wide range of plastics into high-purity monomers with high selectivity and yields.
• Requires no premixing or preprocessing of plastic waste, simplifying the recycling process.
• Uses sustainable, reusable hierarchically porous carbon aerogel (HPC) derived from renewable resources.
• Operates under vacuum with LED light irradiation, allowing localized photothermal depolymerization and reducing side reactions.
• Applicable to various polymer types and post-consumer plastic forms, enhancing versatility.
• Scalable by adjusting irradiation area and HPC volume to meet industrial needs.
• HPC material can be reused multiple times without significant loss of efficiency, improving cost-effectiveness.
• Offers a sustainable, closed-loop recycling platform that overcomes contamination and quality issues of traditional mechanical recycling.

Applications

• Industrial plastic waste recycling
• Post-consumer plastics depolymerization
• Monomer recovery for polymer manufacturing
• Closed-loop recycling facilities
• Selective recycling of mixed plastics

Additional info

This chemical recycling method utilizes hierarchically porous carbon aerogel as a photothermal agent. Under vacuum, LED irradiation induces localized heating, causing plastic to melt and wick into the aerogel’s interconnected pores. There, polymers undergo selective depolymerization into gaseous monomers. This approach works across diverse plastics, including polyolefins and polyesters, without requiring premixing or preprocessing. The sustainable, egg-white-derived material is reusable, facilitating efficient, scalable recovery of high-purity monomers.