Professor, Department of Soil and Environmental Sciences, National Chung Hsing University

Speech Title: Kinetic modelling of Nitrogen doped TiO₂ and Nitrogen tourmaline TiO₂ inactivation of gram-positive and gram-negative bacteria

Abstract: The photocatalytic degradation kinetic of inactivation of Gram-negative Escherichia coli (E. coli) and Gram-positive bacteria Staphylococcus aureus (S. aureus) by Nitrogen-doped Ti₂ (NT) and Nitrogen tourmaline TiO₂ (NTT) nanoparticles in aqueous suspension were studied. The effect of photocatalytic microorganism inactivation by visible-light-responsive nitrogen-doped titanium dioxide was still unclarified. Different light intensity, photocatalysts types, loadings, and initial bacteria concentration in the range from 0.81 to 7.25 mW cm^-2, 0.2 to 1.00 g L^-1, and 10^-4 to 10^-7 CFU mL^-1 were evaluated, respectively. The highest efficiency was observed in the present of NTT = 1.0 g L^-1 and the light intensity = 7.25 mW cm^-1. The photocatalytic inactivation toward the bacteria by NTT showed similar trends with higher effectiveness toward S. aureus under the same experimental conditions. Although modified Hom model did not provide the physical meaning of the bacteria photo-inactivation kinetics, the modified Hom model can fit well with all the experiment parameters carried out in this study. The empirical constants of NTT for E. coli and S. aureus were k₁=17.50, k₂=0.002, k₃=2.00 and k₁=13.7, k₂=0.0039, k₃=2.10, respectively. The k₁ value shows relevance to lengthen the reaction time. According to this, the modified Hom model shows the benefit for comparison with different photoinactivation system. The antimicrobial activity of NT and NTT against Gram-negative bacteria could vary with bacterial species. These results further demonstrate that in an aqueous system, NTT nanoparticles can effectively inhibit Gram-negative and Gram-positive bacteria under visible light.