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Influence of pigments on phototransformation rates of biocides in paints

  • Biocides are commonly applied to building materials such as renders and paints in order to protect them from microbial spoilage. Since the building materials are commonly exposed to weathering conditions, biocides incorporated within the material matrices tend to leach out during the rain events. Moreover, photodegradation processes play an important role in the fate of biocides, due to the exposure to natural sunlight. Leaching of biocides and their moderate persistence, indicate that photodegradation products of biocides can also be found as environmental contaminants in runoff waters. In this study we investigated the photodegradation of four commonly used biocides (carbendazim, diuron, octylisothiazolinone and terbutryn) in four different paint formulations with selected pigments (red, white, black and one artificial, not commercial pigment-free formulation for comparison). As pigments interact with the spectrum of the incoming light, the effect of pigments on photodegradationBiocides are commonly applied to building materials such as renders and paints in order to protect them from microbial spoilage. Since the building materials are commonly exposed to weathering conditions, biocides incorporated within the material matrices tend to leach out during the rain events. Moreover, photodegradation processes play an important role in the fate of biocides, due to the exposure to natural sunlight. Leaching of biocides and their moderate persistence, indicate that photodegradation products of biocides can also be found as environmental contaminants in runoff waters. In this study we investigated the photodegradation of four commonly used biocides (carbendazim, diuron, octylisothiazolinone and terbutryn) in four different paint formulations with selected pigments (red, white, black and one artificial, not commercial pigment-free formulation for comparison). As pigments interact with the spectrum of the incoming light, the effect of pigments on photodegradation rates was assumed to be relevant. Samples were prepared by painting 2 layers of selected paints on glass plates. The dry paint samples were exposed to UV light for designated time periods ranging from 0 h to 1056 h of total exposure time in a commercial UV-Test® Fluorescent / UV Instrument (Atlas Material Testing Technology, Illinois, USA). The applied energy was 1.2 W/m2. The black panel temperature was established at 40 ºC. The radiant energy from the UV fluorescent lamps was concentrated in the wavelength region at 351 nm and below. All samples were prepared in triplicates. After irradiation, paint samples were removed from glass carriers and extracted with methanol. The remaining biocide concentrations as well as the amounts of photodegradation products were analysed with the use of liquid chromatography coupled to mass spectrometry. The transparent, pigment-free formulation was the most vulnerable to light exposure, a visible colour change from white to yellow was observed after 1056 h of irradiation. Diuron, octylisothiazolinone and terbutryn degraded from pigment-free formulation following first-order degradation kinetics. A decrease of carbendazim was also observed. The remaining formulations showed similar degradation patterns for all analysed biocides. All paints showed degradation for octylisothiazolinone with 3-octyl-2(3H)-thiazolone being the main product for red, white and black pigment paint. N-octylacetamide and N-octyloxamic acid were dominant in the pigment-free formulation. Terbutryn sulfoxide was the main degradation product of terbutryn in case of the white paint, while other pigments showed higher concentrations of desbuthyl-2-hydroxy-terbutryn and desethyl-2-hydroxy-terbutryn. A determination of photodegradation in terms of pigment type, measured light spectra and intensity as outlined in this study, could provide a basis for establishing a quantitative description of the fate of biocides in paints, which has significance not only in terms of environmental science, but also could provide a guideline for developing new and effective products.zeige mehrzeige weniger

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Metadaten
Autoren/innen:M. Urbanczyk
Koautoren/innen:U.E. Bollmann, N. Borho, Ute Schoknecht, K. Bester
Dokumenttyp:Posterpräsentation
Veröffentlichungsform:Präsentation
Sprache:Englisch
Jahr der Erstveröffentlichung:2017
Organisationseinheit der BAM:4 Material und Umwelt
4 Material und Umwelt / 4.1 Biologische Materialschädigung und Referenzorganismen
DDC-Klassifikation:Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Sanitär- und Kommunaltechnik; Umwelttechnik
Freie Schlagwörter:Biocide; Photodegradation; Pigment
Themenfelder/Aktivitätsfelder der BAM:Umwelt
Umwelt / Umweltschadstoffe
Veranstaltung:16th International conference on chemistry and the environment
Veranstaltungsort:Oslo, Norway
Beginndatum der Veranstaltung:18.06.2017
Enddatum der Veranstaltung:22.06.2017
Verfügbarkeit des Volltexts:Volltext-PDF im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:27.06.2017
Referierte Publikation:Nein