A Scalable Singlet Oxygen Reactor for Photodegradation of Active Pharmaceutical Compounds and Disinfection

Current water treatment approaches effectively inactivate pathogens; however, they are not designed to remove trace pharmaceuticals and other emerging contaminants. Singlet oxygen (¹O₂) offers a promising approach to water treatment due to its high oxidation potential while also being safe for humans and aquatic life due to its short lifetime (<4 μs in water) and rapid decay to molecular oxygen. However, this short lifetime makes implementation challenging. Moreover, obstacles to delivering light to the photosensitizer (PS) in turbid water must be overcome. Here, we present a novel reactor for generating ¹O₂ for water treatment. A water-insoluble PS is coated on the surfaces of roughened PMMA lightguides that are closely packed into a photoreactor and illuminated by a high-power LED. This approach is insensitive to water turbidity as the incident light is coupled to the PS coating. The effects of fluence, surface roughness, and PS loading on ¹O₂ trapping rates were quantified using uric acid. Destruction of five pharmaceutical compounds was measured by HPLC, and the rate constants demonstrate the influence of substrate structure on reactivity. Disinfection efficacy was demonstrated using 10⁵ CFU/mL Escherichia coli suspensions. Approaches to scaling this system for continuous water treatment are presented.