Solar-Driven Photocatalytic Ceramic Membrane Reactors for Paracetamol Degradation: Process Optimization, Transport Dynamics, and Preliminary Cyclic Reusability

The use of membrane separation and heterogeneous photocatalysis together appears to be an innovative way to remove long-lasting pollutants such as paracetamol (PCT) from water. To overcome the limited process by understanding hindering the practical deployment of solar-driven photocatalytic membrane reactors (PMRs), this study proposes a process-engineering-centered framework for a low-cost, integrated ceramic PMR. A laboratory-scale system was developed using inexpensive red clay ceramic membranes modified by immobilizing TiO2 (P25) for paracetamol degradation under natural sunlight and ultraviolet irradiation. Unlike previous studies mainly focused on material development, this work evaluates the coupled effects of TiO2 loading, membrane inclination, irradiation source, and transport phenomena on reactor performance. Systematic investigations of TiO2 loading (0–1 g/L), membrane inclination (0°–60°), and irradiation conditions revealed maximum paracetamol degradation efficiencies of 74.9% (UV) and 55.5% (sunlight) after 5.5 h on the retentate side. However, concentration polarization, fouling, and permeate flux decline limited overall removal efficiency. Reactor performance strongly depended on hydrodynamic orientation, with horizontal orientation (0° inclination) improving photon exposure and mass transfer. Reusability tests showed activity losses of 52% under UV and 33% under sunlight after five cycles, indicating the need for regeneration strategies. Kinetic analysis confirmed that degradation was controlled by photon flux, catalyst accessibility, and boundary-layer effects. Despite repeated operation, the ceramic support maintained its integrity. This study provides practical design principles for the development of potentially scalable, energy-efficient and cost-effective solar-driven photocatalytic ceramic membrane reactors for decentralized wastewater treatment.