Carbon dots derived from polyurethane waste for photocatalytic dye removal

Abstract

Carbon dots (CDs) were synthesized from polyurethane (PU) waste through a simple and sustainable hydrothermal route. The synthesis promotes carbonization and nitrogen incorporation from the polymer backbone, resulting in stable, quasi-spherical nanoparticles with graphitic domains and green photoluminescence. The CDs exhibited excellent colloidal stability, strong absorption at 284 nm (π → π*), and stable emission over 6 months. Their photocatalytic activity was evaluated in the degradation of methylene blue (MB) and other dyes under UV-C irradiation in the presence of H₂O₂. The optimized material (200CD14) achieved 98.3% MB removal and 92% reduction in total organic carbon, confirming efficient mineralization. Radical scavenging assays indicated the participation of both O₂˙⁻ and ˙OH species in the process. The CDs maintained over 80% activity after five reuse cycles, demonstrating their robustness and potential for wastewater treatment. This work demonstrates the successful conversion of PU waste into functional nanomaterials, offering a practical approach within green chemistry and the circular economy for valorizing polymeric residues.