Insights into interactions of chlorine-based cleaning products with indoor relevant surfaces

Abstract

Environmental context The chemistry that occurs in indoor environments and the role that indoor surfaces play have recently received increased attention in the scientific community. Here we have investigated the chemistry of chlorine-based cleaning products and their interactions with indoor relevant surfaces and find that these surfaces react with these cleaning products to yield surface adsorbed chlorine oxides and other surface-bound species. Rationale Indoor chemistry has recently received increased attention in the scientific community due to the fact that there is relatively little known given its unique environment including point combustion sources (candles, gas stoves, etc.) resulting in high aerosol concentrations, high surface to volume ratios and the impact of humans on indoor air quality. Recently, surface-initiated reactions during chlorine cleaning events have been proposed.  Methodology In this study, we probe the interaction of bleach headspace gas with high surface area silica as a proxy for window glass – an ‘inert’ and impervious surface – using attenuated total reflectance Fourier Transform infrared (ATR-FTIR) spectroscopy, atomic force microscopy photothermal infrared (AFM-PTIR) spectroscopy and transmission electron microscopy (TEM) to observe surface chemical and physical changes. Results The results suggest chemical transformations occur at the silica surface forming surface adsorbed chlorine oxides (ClOx). Conductivity and ion chromatography methods support the presence of adsorbed chloride after surfaces have been exposed to bleach and HOCl. Discussion Interactions between HOCl and indoor surfaces have not been previously studied with molecular based techniques. The possibility of surface-mediated reactions has been relatively unexplored on indoor surfaces and this study shows the chemistry of chlorine-containing cleaning products on indoor relevant surfaces.