Experimental measurement and modelling of reactive species generation in TiO2 nanoparticle photocatalysis

Abstract

The generation of reactive species in titanium dioxide (TiO2) nanoparticle photocatalysis was assessed in a laboratory scale setup, in which P25 Aeroxide TiO2 suspensions were photoactivated by means of UV-A radiation. Photogenerated holes and hydroxyl radicals were monitored over time by observing their selective reaction with probe compounds, iodide and terephthalic acid, respectively. TiO2 aggregate size and structure were characterized over the reaction time. Reactive species quenching was then described by a model, accounting for radiative phenomena, TiO2 nanoparticle aggregation and kinetic reactions. The interaction between iodide and photogenerated holes was influenced by iodide adsorption on TiO2 surface, described by a Langmuir-Hinshelwood mechanism, whose parameters were studied as a function of TiO2 concentration and irradiation time. Iodide oxidation was effectively simulated by modelling the reaction volume as a completely stirred two-dimensional domain, in which irradiation phenomena were described by a two-flux model and the steady state for reactive species was assumed. The kinetic parameters for iodide adsorption and oxidation were estimated and successfully validated in a different experimental setup. The same model was adapted to describe the oxidation of terephthalic acid by hydroxyl radicals. The kinetic parameters for terephthalic acid oxidation were estimated and validated, while the issues in investigating the interaction mechanisms among the involved species have been discussed. The sensitivity of operating parameters on model response was assessed and the most relevant parameters were highlighted.

Influence of Aqueous Inorganic Anions on the Reactivity of Nanoparticles in TiO2 Photocatalysis

“…These values are comparable with those obtained previously for iodide oxidation in nonsonicated suspensions of TiO 2 at 40 mg L −1 . 36…”

Adsorption and photocatalysis of 2-ethyl-1-hexanol over graphene oxide–TiO2 hybrids post-treated under various thermal conditions

“…Meanwhile, the photocatalytic efficiency of GO-TiO 2 -400 increased as the photocatalyst mass increased from 0.05 to 0.2 mg cm −2 (Fig. 12), probably because of the greater numbers of adsorption and photocatalytic reaction sites and larger amount of photon absorbance at high photocatalyst masses [30,31].…”

Settleable engineered titanium dioxide nanomaterials for the removal of natural organic matter from drinking water

“…Although it cannot be assumed that there was a one to one relationship . between •using TiO 2 suspensions in batch reactors such as Turolla et al[29].As shown in Table3, the rate of HTPA formation was an excellent fit (R 2 = 0.97 to 0.99) to a zero order reaction model. The rate of HTPA formation ranged from 0.104 ± 0.009 M/min for NB 240/550 to 0.739 ± 0.058 M/min for NB 240/700.…”