Photocatalytic thin films for the removal of contaminants of emerging concern from water and wastewater: Engineering readiness and process feasibility

Photocatalytic thin films are emerging as promising catalysts form for degrading contaminants of emerging concern (CECs) in water and wastewater. To evaluate their engineering readiness and potential for practical implementation, this systematic review screened 96 publications (2013–2025) and selected 40 representative studies using the ProKnow-C method. The analysis critically covered materials, deposition techniques, target contaminants, operational conditions, reactor configurations, and photocatalytic performance focused on water and wastewater treatment. Sixty-two different CECs, including pharmaceutical drugs and endocrine-disrupting compounds, were identified as target pollutants. Most were tested at initial concentrations in the mg L -1 range, which are several orders of magnitude higher than environmentally relevant ng L -1 levels, indicating experimental conditions that do not adequately reflect real-world scenarios. Bibliometric analysis indicates that TiO₂ remains the dominant photocatalyst, while dopants such as Ag, Cu, Mn and heterostructures like TiO₂/ZnO and TiO₂/graphene extended visible-light activity and improved charge separation. However, only one continuous-flow study and two pilot-scale investigations were identified, yielding pharmaceutical removals of 40–78% with residence times of hours. When combined with homogeneous oxidants or photosensitizers, thin films achieved higher CECs degradation efficiency. Hence, photocatalytic thin films remain at technology readiness level (TRL) between 2 (formulation of concept) and 5 (validation in pilot-scale). Future research should focus on reactor design, continuous operation, and coupling with other catalytic processes rather than solely developing new materials, aligned with the environmentally applied catalysis. • TiO 2 accounts for 94% of photocatalytic thin-film studies on CEC removal. • Only 2 of 40 studies reached pilot scale and continuous-flow operation. • Most studies use mg L -1 CEC levels, far above environmentally relevant concentrations. • Coupling thin films with oxidants or photosensitizers enhances degradation efficiency. • Reactor design and scalability remain key bottlenecks for real-world implementation.