Unexpectedly High Levels of Organic Compounds Released by Indoor

Sep 6, 2018 - State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510 640 , ...
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Remediation and Control Technologies

Unexpectedly high levels of organic compounds released by indoor photocatalytic paints Adrien Gandolfo, Sylvain R. A. Marque, Brice Temime-Roussel, Rachel Gemayel, Henri Wortham, Delphine Truffier-Boutry, Vincent Bartolomei, and Sasho Gligorovski Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.8b03865 • Publication Date (Web): 06 Sep 2018 Downloaded from http://pubs.acs.org on September 9, 2018

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Environmental Science & Technology

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Unexpectedly high levels of organic compounds

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released by indoor photocatalytic paints

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Adrien Gandolfo*1, Sylvain Marque2, Brice Temime-Roussel1, Rachel Gemayel1§, Henri

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Wortham1, Delphine Truffier-Boutry3, Vincent Bartolomei3, Sasho Gligorovski*1,4

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Aix Marseille Univ, CNRS, LCE, UMR 7376, 13331, Marseille, France

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Aix Marseille Univ, CNRS, ICR, UMR 7273, 13297, Marseille, France

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Grenoble Alpes Univ, CEA, L2N, 38054 Grenoble, France

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State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510 640, China

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Present adress : Univ. Lyon, Université Claude Bernard Lyon 1, CNRS, UMR 5256, IRCELYON, Villeurbanne, France

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Corresponding authors*:

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Sasho Gligorovski

[email protected]

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Adrien Gandolfo

[email protected] 1 ACS Paragon Plus Environment

Environmental Science & Technology

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ABSTRACT

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Photocatalytic paints based on titanium dioxide (TiO2) nanoparticles represent a promising

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treatment technology for cleaning the air at our dwellings. A few studies have shown that

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instead of elimination of harmful indoor air pollutants the production of carbonyl compounds

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occurs from the photocatalytic paints.

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Herein, we report unexpectedly high concentrations of volatile organic compounds (VOCs)

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released upon irradiation of photocatalytic paints which are meant to clean the air at our

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dwellings. The concentrations of the VOCs were measured continuously and on-line by PTR-

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ToF-MS (Proton Transfer Reaction – Time of Flight - Mass Spectrometry) connected to a

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well-established flow tube photoreactor. The PTR-ToF-MS analysis revealed the presence of

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52 ions in the mass range between 20 and 490 amu, among which 43 have been identified. In

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particular very high emission rates were estimated of two relevant indoor air pollutants,

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formaldehyde and acetaldehyde as 355 µg h-1 and 257 µg h-1 for 1 m2, respectively. We

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suggest a detailed reaction mechanism responsible for the production of these harmful indoor

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air pollutants (formaldehyde and acetaldehyde, among the others). The hydroxyl radicals

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(OH) formed upon activation of TiO2, react with the organic constituent (butyl acrylate and

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vinyl acetate) of the paint binder lead to generation of an important number of organic

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compounds. We demonstrate that the TiO2 quantity and the organic content of the binder is of

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paramount importance with respect to the formation of VOCs, which should be considered for

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future optimization of this air remediation technology based on TiO2 nanoparticles.

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Environmental Science & Technology

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TOC GRAPHICS

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KEYWORDS Volatile organic compounds, formaldehyde, indoor air, photocatalysis, PTR-

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ToF-MS

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Introduction

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Considering that in the developed world people spend most of their time indoors, the risks to

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health may be greater due to exposure to air pollution indoors than outdoors 1. The air

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exchange rate is the main removal pathway of airborne pollutants in the indoor environments

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considerably the air exchange rates in order to save the energy consumption, which in turn

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implies higher levels of air pollutants

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paints based on titanium dioxide nanoparticles anatase crystalline form (TiO2), have been

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suggested as an alternative air treatment technology. The global photocatalyst market size was

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estimated at 1.65 billion USD in 2016 and it is expected to reach 4.58 billion of USD by

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2025, according to a new report by Grand View Research, Inc5. The market of indoor

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photocatalytic paints makes an important contribution to it. For example, the leaders on EU

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market, EVONIC and KEIM, recently launched new commercial indoor photocatalytic

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paints5.

. However, the modern low energy buildings are airtight with a tendency to decrease

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. To improve the indoor air quality, photocatalytic

3 ACS Paragon Plus Environment

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When TiO2, is irradiated with photons carrying energy equal or in excess of its band gap (λ