Multitarget Evaluation of the Photocatalytic Activity of P25-SiO2 Prepared by Atomic Layer Deposition

Abstract

This work presents the evaluation of the photocatalytic activity of P25 TiO2 particles, coated with SiO2, using atomic layer deposition (ALD) for the photocatalytic removal of methylene blue, oxidation of methanol and inactivation of Escherichia coli bacteria in water and its comparative evaluation with bare P25 TiO2. Two different reactor configurations were used, a slurry reactor with the catalyst in suspension, and a structured reactor with the catalyst immobilized in macroporous foams, that enables the long-term operation of the process in continuous mode, without the necessity of separation of the particles. The results show that the incorporation of SiO2 decreases the efficiency of the photocatalytic oxidation of methanol, whereas a significant improvement in the removal of methylene blue is achieved, and no significant changes are observed in the photocatalytic inactivation of bacteria. Adsorption tests showed that the improvements, observed in the removal of methylene blue by the incorporation of SiO2, was mainly due to an increase in its adsorption. The improvement in the adsorption step as part of the global photocatalytic process led to a significant increase in its removal efficiency. Similar conclusions were reached for bacterial inactivation where the loss of photocatalytic efficiency, suggested by the methanol oxidation tests, was counteracted with a better adherence of bacteria to the catalyst that improved its elimination. With respect to the use of macroporous foams as support, a reduction in the photocatalytic efficiency is observed, as expected from the decrease in the available surface area. Nevertheless, this lower efficiency can be counteracted by the operational improvement derived from the easy catalyst reuse.

Characterization and evaluation of the photocatalytic activity of oxides based on TiO2 synthesized by hydrolysis controlled by the use of water/acetone mixtures

“…5, and by applying the direct method, it was possible to estimate the band gap energies (Eg) of the photocatalysts (Liu & Li, 2012). The estimated Eg were as follows: 3.23 eV for W1, 3.24 eV for W1-25, 3.22 eV for W1-50, and 3.23 eV for W1-75, indicating that the estimated band gap energies have not undergone major changes, which agree with the data reported in the literature for pure TiO 2 (Martin-Somer et al, 2020;Neto et al, 2017;Resende et al, 2017). Most likely, this stems from the synthesis conditions adopted in this work, where none dopant material was added.…”

Sub-nanoscale Surface Engineering of TiO2 Nanoparticles by Molecular Layer Deposition of Poly(ethylene terephthalate) for Suppressing Photoactivity and Enhancing Dispersibility

“…From the UV–vis absorption curves, kinetic constants for the TiO 2 photocatalyzed AB9 degradation were obtained by assuming a first-order reaction (eq ): where C AB9,0 and C AB9 are the initial concentration and the concentration at the time t of AB9, respectively, and k app,AB9 is the apparent first-order kinetic constant that represents the reaction rate. Methanol oxidation to formaldehyde can instead be treated as a zero-order reaction (eq ): where C CH 2 O is the concentration of CH 2 O at the time t and k app,CH 2 O is the apparent zero-order kinetic constant.…”

In Water High Yield and Selectivity of CH₄ and H₂ Production Using UVC Light and a SiO₂-surface-modified TiO₂ Photocatalysts

“…Efficient MB removal and E. coli bacteria inactivation have been reported using P25-SiO2. In both cases, an effective negative (P25-SiO2)-positive (MB and protein) interaction is claimed as the leading cause for the improvement in photooxidation rate [55]. The adsorption process is then crucial in these photocatalytic reactions.…”