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

Abstract

This work reports uptake coefficients and by-product yields of ozone precursors onto two photocatalytic paving materials (asphalt and concrete) treated with a commercial TiO 2 surface application product. The experimental approach used a continuously stirred tank reactor (CSTR) and allowed for testing large samples with the same surface morphology encountered with real urban surfaces. The measured uptake coefficient (γ geo) and surface resistances are useful for parametrizing dry deposition velocities in air quality model evaluation of the impact of photoactive surfaces on urban air chemistry. At 46% relative humidity, the surface resistance to NO uptake was ~ 1 s cm-1 for concrete and ~ 2 s cm-1 for a freshly coated older roadway asphalt sample. HONO and NO 2 were detected as side products from NO uptake to asphalt, with NO 2 molar yields on the order of 20% and HONO molar yields ranging between 14-33%. For concrete samples, the NO 2 molar yields increased with the increase of water vapor, ranging from 1% to 35% and HONO was not detected as a byproduct. Uptake of monoaromatic VOCs to the asphalt sample set displayed a dependence on the compound vapor pressure, and was influenced by competitive adsorption from less volatile VOCs. Formaldehyde and acetaldehyde were detected as byproducts, with molar yields ranging from 5-32%.

Experimental Study on Photocatalytic Effect of Nano TiO2 Epoxy Emulsified Asphalt Mixture

“…To make the index more than 50% or 25%, the average illumination of road surface needs to be not less than 60 lx or 40 lx, respectively. The data show that the NO degradation rate of this method is higher than that described in other literature, under the basic similar and convertible conditions [7][8][9].…”

“…HC, NO and CO compounds can be transformed into salt and water by nano-TiO 2 under photocatalysis that is an irradiation by a light source with a wavelength less than 387.5 nm [7,8]. Therefore, we needed to select a scheme to make titanium dioxide more in contact with air and ultraviolet light in the design.…”

“…In order to solve the vehicle exhaust accumulation problem in the stage of operation, in recent years, researchers in road work have considered vehicle carrier-road pavement materials and developed many new degradable automobile exhaust pavement materials [6][7][8]. These photocatalysts are dissolved in a solution and sprayed on the surface of the road to be exposed to automobile exhaust and sunlight.…”

Investigation on Parameters Affecting the Effectiveness of Photocatalytic Functional Coatings to Degrade NO: TiO2 Amount on Surface, Illumination, and Substrate Roughness

“…This analyser displayed NO x , NO, and NO 2 concentrations; NO 2 concentrations are being calculated from the difference between NO x and NO concentrations. However, it has recently been observed that this kind of analyser could overestimate the NO 2 concentration as it seemed to measure all NO y entering in the NO x channel [24,52].…”

Self-cleaning building materials: The multifaceted effects of titanium dioxide

“…The applications of TiO2 containing building materials have been widening in the last years, going from the obtaining of self-cleaning façades [10][11][12][13][14] or roads [15][16][17][18][19] with added antipollution effects [20][21][22][23] to the development of preservation treatments for architectural heritage, especially in stone [24][25][26][27][28]. While the mechanisms of photocatalytic and self-cleaning activity have been long studied, together with the development of materials with improved photoactivated performance, their durability and the appraisal of the photoactivated effects over time, in real working conditions, remain only marginally treated.…”