A Green Chemistry and Energy- and Cost-Effective Approach in Innovative Advanced Oxidation Processes Through Photoactive Microgels for Sustainable Applications

Current sustainability challenges for the chemical industry include developing advanced wastewater treatment technologies and transitioning to renewable biomass for more sustainable processes. This study aims to design and develop photoactive colloidal microgels for environmental applications, focusing on the removal of pollutants and the green synthesis of sustainable materials. PNIPAM-based microgels with covalently integrated Rose Bengal as a photosensitizer was synthesized and characterized. The stimuli-responsive colloidal structure of the microgels enhances substrate adsorption and reaction kinetics, surpassing free Rose Bengal due to the local concentration effect provided by the polymeric matrix at the reaction temperature and pH. These materials, designed according to green chemistry principles, enable the sustainable synthesis of 5-hydroxy-2(5H)-furanone, a C4 building block intermediate, achieving over 99% conversion in aqueous media, which is a novel aspect compared to the literature. The removal of Diclofenac from wastewater has been highly efficient, reaching degradation rates of over 99% in 160 min. The photoactive microgels act as efficient photocatalysts, validated under direct solar irradiation, capable of generating singlet oxygen (O₂(¹Δg)) with full recoverability and reusability over multiple cycles. This approach provides a cost-effective eco-friendly solution to economic and environmental challenges in water treatment, as shown by scale-up economic simulations.