Determination of diffusion coefficients of biocides on their passage through organic resin-based renders Katarzyna Styszko a, * , Krzysztof Kupiec b a AGH University of Science and Technology, Department of Coal Chemistry and Environmental Sciences, 30-059 Krakow, Al. Mickiewicza 30, Poland b Cracow University of Technology, Faculty of Chemical Engineering and Technology, ul. Warszawska 24, 31-155 Krakow, Poland highlights  The diffusion of biocides through organic resin-based renders is described.  The rate of the leaching is generally determined by the rate of transport of biocide in the water-filled pores.  The organic modifier in the render influences the diffusion driven transport of biocides. article info Article history: Received 3 January 2016 Received in revised form 15 June 2016 Accepted 20 June 2016 Available online 6 July 2016 Handling Editor: Klaus Kümmerer Keywords: Biocides Render Diffusion coefficient Leaching abstract In this study the diffusion coefficients of isoproturon, diuron and cybutryn in acrylate and silicone resin- based renders were determined. The diffusion coefficients were determined using measuring concen- trations of biocides in the liquid phase after being in contact with renders for specific time intervals. The mathematical solution of the transient diffusion equation for an infinite plate contacted on one side with a limited volume of water was used to calculate the diffusion coefficient. The diffusion coefficients through the acrylate render were 8.10$10 9 m 2 s 1 for isoproturon, 1.96$10 9 m 2 s 1 for diuron and 1.53$10 9 m 2 s 1 for cybutryn. The results for the silicone render were lower by one order of magnitude. The compounds with a high diffusion coefficient for one polymer had likewise high values for the other polymer. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Currently, the attention of researchers and the Regulation of the European Parliament and of the Council (Regulation (EU). No 528, 2012) has been focused on the release of biocides from façade coatings. Biocides are used to protect façade coatings like organic modified renders and paints from deterioration by algae, fungi and bacteria (Reichel et al., 2004; Paulus, 2005). Natural weather con- ditions cause their release from applications such as coatings. Some compounds used as biocides are toxic to aquatic organisms and long-term adverse effects in the aquatic environment cannot be excluded already for low concentrations (Mohr et al., 2008). Burkhardt et al. (2007) showed that release from building materials is a major source of biocide pollution concerning urban waters. Storm water is often directly discharged into surface water excluding wastewater treatment plant. The purpose of the biocide product regulation is to improve the free movement of biocidal products within the European Union while ensuring a high level of protection of both human and animal health and the environment (Regulation (EU). No 528, 2012). The laboratory leaching test procedure includes the evaluation of risk assessment for the authorization of active substances and biocidal products, on one side and optimized leaching processes may ensure long-term efficacy of materials coupled with minimized emissions on the other side (Schoknecht et al., 2013). Coated external surfaces are only exposed to water during dew formation and driving rain events and dryness in between rain periods. The critical input pa- rameters required for estimating emissions are leaching rates. Release of biocidal compounds from different materials was demonstrated in laboratory and/or field studies (Konstantinou and Albanis, 2004; Schoknecht et al., 2009; Wittmer et al., 2011; Burkhardt et al., 2012; Wangler et al., 2012; Schoknecht et al., * Corresponding author. E-mail address: styszko@agh.edu.pl (K. Styszko). Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere http://dx.doi.org/10.1016/j.chemosphere.2016.06.077 0045-6535/© 2016 Elsevier Ltd. All rights reserved. Chemosphere 160 (2016) 273e279