Photodegradation of Air and Water Contaminants Using 3D-Printed TiO₂ Nanoparticle Scaffolds

A significant challenge in the photocatalysis field is getting self-supporting three-dimensional (3D)-printable photocatalysts that preserve their photocatalytic activity. Herein, we disclose reusable 3D-printable photocatalysts based on binder-free TiO2 nanoparticles (3DM-TiO2) under an eco-friendly, affordable, and reliable methodology for the first time. Strong and mechanically stable 3DM-TiO2 structures (compression strength = 16 MPa) were obtained under soft sintered conditions (∼400 °C), exhibiting an anatase/rutile ratio of 85/15% by the Rietveld refinement, a mesoporous structure with a surface area (SBET) of 45.2 m2/g, and outstanding photocatalytic activity. 3DM-TiO2 successfully demonstrated high recyclability and adaptability in the dust-free photodegradation experiments of emerging contaminants in the liquid phase (triclosan, TCS) and gas phase (liquefied petroleum gas, LPG). A TCS mineralization of ∼95% was obtained at 6 h of photodegradation. The reusability from the 3DM-TiO2 was assessed during 12 cycles of TCS degradation, recovering its photocatalytic activity by 100% after reactivation at 400 °C. In the gas phase, the maximum conversion of LPG to CO2 was 95.3% for n-butane, 93.7% for isobutane, and 52.9% for propane after 15 h of photodegradation. All photodegradation experiments were fitted to the Langmuir–Hinshelwood kinetic model. We believe that the technology proposed here could trigger applications of nanomaterial-based photocatalysts, replacing the powdered materials to achieve new reactor designs and process configurations on a large scale.