Using H-titanate nanofiber catalysts for water disinfection: Understanding and modelling of the inactivation kinetics and mechanisms

The H-titanate nanofiber catalyst (TNC), which has a favourable morphological structure for mass transfer and energy access, was proven as a promising alternate titanium dioxide (TiO2) carrier for photo-inactivation of a sewage isolated E. coli strain (ATCC 11775). This study revealed that the TNC loading is a key process parameter that radically influenced the photo-inactivation of bacteria in an annular slurry photoreactor (ASP) system. Variation in the TNC loadings was found to have a considerable impact on the dissolved oxygen (DO) concentration profiles and subsequently, on the photo-inactivation rates of bacteria in the ASP system. The photo-inactivation reaction in the ASP system was found to exhibit three different bacterial inactivation regimes of shoulder, log-linear and tailing. Resultant photo-inactivation kinetics data was evaluated using both empirical and mechanistic bacterial inactivation models. The modified Hom model was found to be the best empirical model that can represent the sigmoid-type bacterial inactivation pattern. An interesting correlation between the TNC loadings and DO concentration profiles was also established. From the correlation, it was found necessary to integrate a DO limiting reactant term in the newly proposed mechanistic Langmuir–Hinshelwood model to describe the bacterial inactivation mechanisms under two different TNC loading conditions of sub-optimal and optimal, respectively.

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► Novel H-titanate nanofiber provided a new material and engineering paradigm to resolve the mass transfer resistance.
► The impacts of nanofiber concentrations on DO profiles revealed that it is a non-limiting reactant at its optimum loading.
► The sigmoid bacterial inactivation profile was found to be best-fitted using the modified Hom model.
► Integration of nanofiber–DO relationship into the L–H mechanistic model provides a new representative kinetic model.