Investigations of Water Uptake on Sodium Acetate Trihydrate and Nonhydrate as Model Aerosol Surfaces using the DRIFTS and ATR-FTIR Techniques

Gregory Matthew Pitch, John S Andre, Arion J Davie

Abstract


Research primarily pertains to the investigation of fundamental, atmospherically relevant processes. Thin water films provide an environment, which has the ability to host atmospherically important aqueous chemical reactions. Aqueous reactions in thin water films are facilitated through properties of bulk water adsorption. Therefore, a model compound was used to investigate the properties of hydration, on the molecular and bulk scale. The selected model compound, sodium acetate trihydrate, exhibits both hydrophobic and hydrophilic character, along with three molecularly bound water molecules. The aforementioned moieties of sodium acetate trihydrate allowed the compound to be used as a model for both organics as well as salts. The trihydrate moeity provides an infrared spectroscopic signal distinguishable from that characteristic of bulk water absorption. The nonhydrate form of sodium acetate was synthesized in our research laboratory. Both the trihydrate and the nonhydrate forms of sodium acetate were investigated via Fourier transform infrared spectroscopy (FT-IR). The experimental system includes an arid environmental box surrounding the spectrometer to remove interference from atmospheric gases. The flow of gases in the system is regulated by four mass flow controllers that allow for mixing of different gases and dilution of reagents prior to introduction to the reaction cell. After exposure to humid nitrogen gas, sodium acetate trihydrate was formed from sodium acetate nonhydrate via the DRIFTS technique, which is atmospherically and chemically interesting.

Keywords


Aerosols; Water Uptake; DRIFTS

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