Photocatalytic Hydrolysis─A Sustainable Option for the Chemical Upcycling of Polylactic Acid

Garratt, Antonia; Nguyen, Klaudia; Brooke, Alexander; Taylor, Martin J.; Francesconi, Maria Grazia

Abstract

Plastic waste is a critical global issue, yet current strategies to avoid committing plastic waste to landfills include incineration, gasification, or pyrolysis high carbon emitting and energy consuming approaches. However, plastic waste can become a resource instead of a problem if high value products, such as fine chemicals and liquid fuel molecules, can be liberated from controlled its decomposition. This letter presents proof of concept on a low-cost, low energy approach to controlled decomposition of plastic, photocatalytic hydrolysis. This approach integrates photolysis and hydrolysis, both slow natural decomposition processes, with a photocatalytic process. The photocatalyst, α-Fe2O3, is embedded into a polylactic acid (PLA) plastic matrix. The photocatalyst/plastic composite is then immersed in water and subjected to low-energy (25 W) UV light for 90 h. The monomer lactide is produced as the major product. α-Fe2O3 (6.9 wt %) was found to accelerate the PLA degradation pathway, achieving 32% solid transformation into liquid phase products, in comparison to PLA on its own, which was found to not decompose, using the same conditions. This highlights a low energy route toward plastic waste upgrade and valorization that is less carbon intensive than pyrolysis and faster than natural degradation. By directly comparing a 25 W (0.025 kWh) UV bulb with a 13 kWh furnace, the photocatalytic reaction would directly consume 520× less energy than a conventional thermochemical pathway. Furthermore, this technology can be extended and applied to other plastics, and other photocatalysts can be used.

Citation

Garratt, A., Nguyen, K., Brooke, A., Taylor, M. J., & Francesconi, M. G. (2023). Photocatalytic Hydrolysis─A Sustainable Option for the Chemical Upcycling of Polylactic Acid. ACS Environmental Au, 3(6), 342–347. https://doi.org/10.1021/acsenvironau.3c00040

• Journal Article Type: Article
• Acceptance Date: Sep 26, 2023
• Online Publication Date: Oct 2, 2023
• Publication Date: Nov 15, 2023
• Deposit Date: Oct 3, 2023
• Publicly Available Date: Oct 3, 2023
• Journal: ACS Environmental Au
• Print ISSN: 2694-2518
• Electronic ISSN: 2694-2518
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 3
• Issue: 6
• Pages: 342–347
• DOI: https://doi.org/10.1021/acsenvironau.3c00040
• Keywords: Polylactic acid; Plastic upcycling; Photocatalysis; Sustainability; Low energy; Processes; Depolymerization
• Public URL: https://hull-repository.worktribe.com/output/4406451