Determination of the photocatalytic deposition velocity

Photoactive roadways: Determination of CO, NO and VOC uptake coefficients and photolabile side product yields on TiO2 treated asphalt and concrete

“…It was apparent, however, that for dry conditions NO 2 uptake was about a factor of 10 less than that of NO. This factor of 10 difference has been reported on uptake to Aeroxide P25 briquettes [31] and from inferred deposition velocities of NO and NO 2 to a photoactive commercial bitumen membrane product in an outdoor experiment [41]. In contrast uptake of NO and NO 2 to a commercial photoactive cementious product showed similar uptakes of NO and NO 2 , with a reported γ of ~3.3 x 10 -5 [10], similar to what we measured for NO at 46%RH to the concrete and AC4 sample sets.…”

“…Currently, there is a lack of information on surface resistances or uptake coefficients and by-product yields for such materials, which are needed to 4 parameterize dry deposition rates and impacts on ozone photochemistry for air quality modeling. Engel et al focused on determining photocatalytic deposition velocities based on the ISO 22179-1 method which requires the use of a plug flow reactor restricting size and shape of photoactive samples [31]. The authors suggests that the use of a continuously stirred tank reactor (CSTR) would allow overcoming such limitations.…”

Grafted iron(iii) ions significantly enhance NO2 oxidation rate and selectivity of TiO2 for photocatalytic NOx abatement

“…It is worth mentioning here that the highest NO 2 oxidation rates observed here with a kinetic constant of 1.39 s À1 , which correspond to a deposition velocity of 0.70 cm s À1 and reactive uptake coefficient of 7.57 Â 10 À5 , are not only dramatically higher than for the pristine sample (by a factor of 9) but also signicantly higher than anything reported in the literature under comparable conditions so far. 32 However, even with the rate constants of NO and NO 2 oxidation being almost the same, under the observed conditions of about 50% conversion, NO 2 should still be present in signicant amounts as an intermediate. Since this is not the case, at least in the rst hours on stream, there might also be another mechanism in place which suppresses NO 2 release.…”

“…† This case was analyzed using Langmuir-Hinshelwood (L-H) kinetics and all other materials were analyzed according to the simplied rstorder kinetics (which in the cases yields the same rst-order rate constants as when using L-H kinetics) to calculate the respective rate constants using eqn (13). 22,31,32 As summarized in Table 1, the rst-order rate constants for NO oxidation are virtually unaffected by both the washing procedure and the iron graing and range from 1.6 to 1.8 s À1 . Only at the highest studied iron loadings of $0.1 at%, the rate constant notably decreases.…”

Photoactivity of Titanium Dioxide Foams

“…Engel et al [30] published an experimental method for the determination of the photocatalytic deposition velocity. To gain more information about our samples and their differences, we used this method.…”