A wide variety of medication is prescribed and used worldwide to treat diseases. Pharmaceuticals are designed and selected to act rapidly within the human body. Therefore, many drugs have lipophilic properties to ensure efficient diffusion through cell membranes. As a result, many excreted drugs enter wastewater largely unmetabolized as active ingredients and can cause potentially toxic effects in non-target organisms and accumulate in food chains. As many drugs are present in wastewater at low concentrations, ranging from ng L-1 to μg L-1, current conventional treatment solutions are ineffective in removing often complex drug mixtures from wastewater. In this study a novel photocatalytic UV-LED-driven flow-through treatment concept was developed and evaluated for its ability to effectively destroy and inactivate a mixture of hospital-relevant test drugs: amoxicillin, paracetamol, tamoxifen, methotrexate and simvastatin. Photocatalytic drug oxidation was based on the generation of reactive oxygen species (ROS) on the surface of metal oxide nanomaterials, which can rapidly break down organic molecules such as drugs. A central aspect of this study was to characterise the underlying chemistry needed to facilitate effective interaction between photocatalytic ROS and the test drugs and then determine the critical parameters required to optimise photocatalytic drug oxidation in a novel flow-through reactor design. Hydroxyl radicals (•OH) were identified as the key ROS responsible for effective test drug oxidation under optimal treatment conditions (using a stirred aqueous ZnO suspension). The effectiveness of •OH-driven drug oxidation by ZnO was shown given a decrease in test drug concentrations following a pseudo first order reaction rate. Diffusion-controlled •OH-driven drug oxidation (in excess of •OH relative to the test drug concentration) was attributed to optimal •OH attack on the aqueous drugs due to a large ZnO surface area (when using ZnO nanoparticles in suspension). With this knowledge, an effective photocatalytic flow-through reactor was developed and tested as a flat-bed recirculating system. The reactor was equipped with durable planar ZnO-functionalised substrates, enabling the generation of a thin aqueous film and close proximity between the aqueous drugs and •OH. This allowed for drug oxidation rates near the limit of diffusion. In the flat-bed setting, the effective removal of a range of hospital-relevant drugs at concentrations representative of authentic wastewaters was ultimately demonstrated. The findings from this proof-of-principle study pave the way for future research which could effectively reduce drug concentrations early within fast-flowing wastewater streams in conjunction with existing treatment solutions.
Nanomaterials and photonic solutions. Novel ‘at source’ approaches to stop hospital-derived priority substances reaching the sewer network.
Valdivia, M. (Author). 20 1月 2026
学生论文: Doctor of Philosophy (awarded by UHI)