Inactivation of Aspergillus niger conidia applying antifungal photocatalytic paints: a kinetic study

Airborne fungal contamination in indoor environments is a growing concern, highlighting the need for innovative microbial control strategies. Developing novel photocatalytic materials for fungal control requires understanding the mechanisms and kinetics of photocatalytic inactivation. This study investigates the inactivation kinetics of Aspergillus niger conidia using a batch reactor and three TiO₂-based paints: rutile (non-photocatalytic), anatase (UV-active), and carbon-doped anatase (UV/Vis-active). Experiments were conducted at two relative humidity (RH) levels (50% and 70–80%) and three radiation fluxes (100%, 56%, and 18%). An empirical kinetic model was developed to describe the dependence of inactivation on radiation flux (power function) and RH (logistic model). Results showed a photocatalytic effect under UV light for photocatalytic paints, while photochemical effects dominated with non-photocatalytic paint. At 50% RH, logarithmic reductions per treatment day were 0.77 and 0.54 for anatase and rutile paints, respectively. At 70–80% RH, photocatalytic inactivation increased significantly, whereas rutile paint remained unchanged. The proposed kinetic model effectively captured the influence of radiation flux and RH, showing strong correlation with experimental data.