The environmental fate of arsenic compounds depends on their surface interactions with nanoscale materials that include minerals and natural organic matter (NOM). In general, molecular-level understanding of surface processes at solid/liquid interfaces demands using simple model systems and integrating spectroscopic, calorimetric, computational chemistry and mathematical modeling tools. In this talk, I will show results on the surface chemistry of arsenate and methylated arsenicals, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) with hematite nanoparticles. Spectroscopic data were collected using attenuated total internal reflection Fourier transform infrared spectroscopy (ATR-FTIR) and experimental results were complemented with DFT calculations. Flow calorimetric measurements were also completed to gain insight into surface charge and heats of adsorption. Thermodynamic binding constants were extracted from applying the triple layer surface complexation model to adsorption isotherm and pH-envelope data. The kinetics of arsenicals interaction with hematite nanoparticles pre-exposed to three types of low molecular weight organics will also be discussed. The significance of these results will be discussed in relation to improving modeling tools and designing arsenic-removal technologies.

Representative References:

(1) Md Abdus Sabur, Sabine Goldberg, Adrian Gale, Nadine Kabengi, and Hind A. Al-Abadleh*. Temperature-dependent ATR-FTIR and Calorimetric Studies on Arsenicals Adsorption from Solution to Hematite Nanoparticles, Langmuir, 2015, 31, 2749-2760.

(2) Arthur Situm, Mohammad A. Rahman, Sabine Goldberg, and Hind A. Al-Abadleh*. Spectral Characterization and Surface Complexation Modeling of Organics on Hematite Nanoparticles: Role of Electrolytes in the Binding Mechanism, Environmental Science: Nano, 2016, 3, 910-926.

(3) Adrian Adamescu, Ian P. Hamilton and Hind A. Al-Abadleh*. Dispersion Effects on the Thermodynamics and Transition States of Dimethylarsinic acid Adsorption on Hydrated Iron-(oxyhydr)oxide Clusters from Density Functional Theory Calculations. Journal of Physical Chemistry A, 2016, 120 (46), pp 9270–9280.