Additive Manufacturing of Photocatalytic Reactors for Water Remediation: Architectures, Validation Standards, Reusability, and Scale-Up

Photocatalysis is a powerful advanced oxidation process for water remediation, yet benchmarking has disproportionately relied on model organic dye pollutants under idealized conditions—overstating practical performance and obscuring mechanistic complexity. Three-dimensional (3D) printing now offers an unprecedented opportunity to engineer photocatalytic reactors with precisely controlled architectures, optimized mass transfer, tunable porosity, and defined light-penetration channels—capabilities unattainable with conventional slurry or thin-film configurations. This systematic and critical review examines the state of the art in additive manufacturing of photocatalytic reactors for water treatment, focusing on three under-developed dimensions: (i) performance validation against environmentally relevant contaminants—pharmaceuticals, endocrine-disrupting compounds (EDCs), PFAS, microplastics, and waterborne pathogens; (ii) mechanistic rigor, including reactive oxygen species (ROS) identification, quantum yield determination, and mineralization metrics; and (iii) genuine reusability under realistic cycling conditions. The dominant printing modalities—FDM/FFF, SLA, DLP, DIW, and binder jetting—are critically evaluated for photocatalyst loading, geometric resolution, and scalability. A persistent gap is identified between proof-of-concept studies and systems capable of rigorous quantitative benchmarking. To address this, a minimum reporting standard is proposed, and the materials, engineering, and regulatory challenges that must be resolved before 3D-printed photocatalytic reactors can transition from academic novelties to deployable treatment units are outlined. A total of nine peer-reviewed studies, identified through a systematic search of Scopus and Web of Science (2016–2026), form the evidence base for the quantitative assessments reported herein. Screening and data extraction were performed by a single reviewer (G.K.) without independent verification, which represents a limitation of the review.