In situ evaluation of the NOx removal efficiency of photocatalytic pavements: statistical analysis of the relevance of exposure time and environmental variables

Abstract

In the recent past, the NOx removal efficiency of photocatalytic materials has been subject of many studies with promising results. However, many of these studies involve laboratory tests carried out under standardized climatic exposure conditions, often not representative of the real world environment. With the aim to bridge this gap, selected photocatalytic materials have been applied to different substrates in outdoor demonstrator platforms at pilot scale as part of the project LIFE-PHOTOSCALING. The paper presents the results of in situ measurements of NOx removal efficiency of the materials, performed during 17 months. Statistical models accounting for the influence of exposure time and relevant environmental variables are derived. They suggest that photocatalytic emulsions on the tested asphalt experience a significant loss of activity over time irrespective of climatic conditions. The efficiency of photocatalytic slurries on asphalt and of concrete tiles, with the photocatalyst applied on surface or in bulk, mainly depends on substrate humidity.

New Holistic Conceptual Framework for the Assessment of the Performance of Photocatalytic Pavement

“…Given the enormous volume of experimental data, only the findings relevant to establishing a holistic conceptual approach for the assessment of the photocatalytic pavement performance and corresponding quantitative conformity criteria are summarized in this paper. Additional data can be found in the literature (Jiménez-Relinque et al, 2019Cordero et al, 2020;Hingorani et al, 2020;Nevshupa et al, 2020b) or on the project website (www. lifephotoscaling.eu).…”

“…The results of several laboratory studies proved that photocatalysis effectively deactivates and mineralizes most of the harmful contaminants such as NO x (Cassar, 2004;Chen and Poon, 2009a,b;Bengtsson and Castellote, 2010;Folli et al, 2010;Lucas et al, 2013;Bloh et al, 2014;Mendoza et al, 2015;Mills and Elouali, 2015;Hernández Rodríguez et al, 2016;Mothes et al, 2016;Jimenez-Relinque and Castellote, 2019b;Chen et al, 2020). Furthermore, this technology has already been tested on the pilot and real scales in several projects; the results indicate photocatalytic effectiveness (Beeldens et al, 2007;Maggos et al, 2007Maggos et al, , 2008Chen and Chu, 2011;Boonen and Beeldens, 2013;Suarez et al, 2014;Folli et al, 2015;Gallus et al, 2015;George et al, 2016;Jiménez-Relinque et al, 2019;Cordero et al, 2020). However, the information obtained in these studies is not conclusive for evaluating the overall performances of photocatalytic pavements because other material characteristics relevant to their functionality, such as the durability, or potential undesirable secondary effects were not assessed.…”

Photocatalytic BiOX Mortars under Visible Light Irradiation: Compatibility, NOx Efficiency and Nitrate Selectivity

“…Photocatalytic building materials show diverse properties, such as the decomposition of air contaminants, as well as self-cleaning, antifogging, and self-disinfection [1][2][3][4][5][6]. Among them, the removal of nitrogen oxides (NO x ) for air purification is the most extensively studied application due to urgent demand for technologies to reduce urban pollution from vehicle gaseous exhaust emissions [7,8].…”

“…These results make its use a safer and environmentally sustainable option. Finally, the NO 3 − selectivity (i.e., the ratio of NO converted to nitrates) was derived according to Equation (7).…”

From analysis to decision: Revision of a multifactorial model for the in situ assessment of NOx abatement effectiveness of photocatalytic pavements

“…To tackle this problem a new experimental setup called "PhotonSite" intended to measure the photocatalytic activity of a pavement in situ and under real conditions was developed and patented (PCT/ES2016/070808 [6]. The data obtained by "PhotonSite" were validated through the comparison with the results of a standard laboratory test according to ISO 22197:1-2007 [19]. This development paved the way towards the systematic investigation into the influence of environmental variables, seasonal variations, ageing, wearing, weathering and so on upon the photocatalytic activity of various classes of pavements.…”