Development of a sustainable photocatalytic process for air purification.

Nowadays, air pollution has become a global menace being responsible of a significant increase on the morbidity and mortality of human beings. In view of this, sustainable and efficient technologies for air purification are being sought. Air purification by photocatalytic treatment has received a lot of attention due to the unspecific and high oxidation capacity of the catalyst; however still some variables must be optimized to assure practical applications. In this work, visible light active TiO₂–Cu²⁺@perlite and Ag@TiO₂–Cu²⁺/perlite supported materials were fabricated. TiO₂–Cu²⁺ (2 at. %) were synthesized using a sol-gel procedure followed of the impregnation of the support by immersion. For Ag@TiO₂–Cu²⁺, silver deposition was conducted by chemical reduction using sodium citrate and sodium borohydride. The materials (powders and supported materials) were characterized by Scanning Electron Microscopy (SEM) to demonstrate their small size and adherence to the substrate. A prototype of a photocatalytic air purifier was built. The efficacy of the prototype was evaluated for the disinfection of indoor air (dentistry clinics). The photo-catalyst was activated using visible and UVA low-cost high-energy LEDs. The antibacterial activity of the air filter was evaluated. Ag@TiO₂–Cu²⁺ exerts better air disinfection activity at lower doses in comparison to TiO₂–Cu²⁺. Bacterial growth inhibitions up to 99% were achieved for both, Gram-negative and Gram-positive bacteria. The incorporation of Ag and Cu to TiO₂ improves the antibacterial activity of the materials due to enhanced photocatalytic activity and the synergic activity of TiO₂ and dopant elements (Ag, Cu) to inhibit microorganism's growth.