Mesoporous TiO₂ Monoliths Impregnated with CdS and CuO Nanoparticles for Airborne Bacteria Inactivation Under Visible...

In this work, macroscopic TiO₂ monoliths are proposed to serve simultaneously as support and co-catalyst in a continuous flow photoreactor. The impregnation via one-pot of mesoporous TiO₂ with CdS (m-TiO₂/CdS) and CuO (m-TiO₂/CuO) nanoparticles enabled the formation of photocatalytic heterojunctions retaining high specific surface area (~ 100 m²/g). The impregnated monoliths of 2-3 mm in size were employed as photocatalysts to inactivate airborne bacteria under blue light, reducing the emission of living airborne bacteria up to 0.1% and 37.7% when using m-TiO₂/CdS and m-TiO₂/CuO, respectively. Bacteria were characterized and quantified by flow cytometry and cell lysis was confirmed by SEM, detecting collapsed bacteria. Along 96 h of continuous photocatalysis at a flow rate of 2.2 L/min, the cell concentration presented maxima and minima due to the adsorption-desorption stages of bioaerosols over the catalysts, in concordance with thermal gravimetric analysis. The reactivation of catalysts was achieved by calcination at 400 °C, however, after a third re-cycle, the photocatalytic activity for all monoliths was practically negligible because the physicochemical surface changes hinder the adequate bioaerosol adsorption. These porous systems could emerge as promising gas-phase catalysts since the mass transport is facilitated by porosity and the release of catalyst nanoparticles is avoided by the active support, providing a safe and viable model for bioaerosols inactivation to improve indoor air quality with the use of interior lighting.

The online version contains supplementary material available at 10.1007/s10562-021-03659-9.