Mullite membrane coatings: antibacterial activities of nanosized TiO2 and Cu-grafted TiO2 in the presence of visible light illumination

Porous mullites used as ceramic membranes were fabricated and coated with TiO2 and 0.1 wt% Cu(II)-grafted TiO2 powders. A spinning coating technique was applied for the coating process. Antibacterial activities of the coated mullites were tested against pathogenic bacteria Escherichia coli (E. coli) by following the experimental methods of ISO 17094:2014 standardized for testing photocatalyst materials under visible light of a florescent lamp as an indoor-tested condition. Mullites without coatings were used as control samples. After 4 h of light exposure, the number of the initially viable bacteria increased significantly for the uncoated mullites and decreased for all of the coated mullites. Coating layers of TiO2 and Cu-grafted TiO2 could inactivate E. coli under light illumination. In dark condition, 0.1 wt% Cu(II)-grafted TiO2 coating on the mullites could inactivate the bacteria, while TiO2 coating on the mullites could not inactivate the bacteria. The experimental results provide a possibility of using the coated mullites for disinfection applications. Bacterial inactivation mechanisms of TiO2 and Cu-grafted TiO2 in coating layers were investigated and discussed in terms of microstructural observation on the coating layers.