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A set of TiO 2 samples with different anatase/rutile ratios was prepared by calcinations at different temperatures from commercial photocatalyst Degussa P25. The effects of the two crystalline phases of titanium (IV) oxide on the photocatalytic activity in gaseous phase through oxidation of light hydrocarbons were studied. Crystalline phase transformation from anatase to rutile occurred at 700 • C for P25. Results indicate that samples with higher anatase/rutile ratios presented higher intrinsic activities for the photodegradation of a propane/isobutane/butane (40/35/25 %V) mixture. However, the activity did not totally disappear after complete crystalline transformation from anatase to rutile, indicating that the pure rutile phase also presents photoactivity. During the photocatalytic reaction of TiO 2 samples, a linear dependence was found between the inverse of the intrinsic reaction rate constant (k intrinsic) and the water adsorption capacity in the surface (WAPS) of the synthesized TiO 2 catalyst. The thermal treatment used to induce the formation of rutile by calcination would presumably reduce water adsorption capacity and surface area, leading to a decrease in photocatalytic activity.

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A significant challenge in the photocatalysis field is getting selfsupporting three-dimensional (3D)-printable photocatalysts that preserve their photocatalytic activity. Herein, we disclose reusable 3D-printable photocatalysts based on binder-free TiO 2 nanoparticles (3DM-TiO 2 ) under an eco-friendly, affordable, and reliable methodology for the first time. Strong and mechanically stable 3DM-TiO 2 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 (S BET ) of 45.2 m 2 /g, and outstanding photocatalytic activity. 3DM-TiO 2 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-TiO 2 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 CO 2 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.