A majority of inorganic (e.g. halides, SO42-) and organic species (dissolved humic substances) abundant in the natural waters typically exhibit weak interactions at the particle-water interfaces, and with counter ions in aqueous solutions. The coordination environments of these species have been highly debated, as the weak interactions cause minor changes in the characteristic electronic and vibrational spectral signatures. These weakly interacting species are also ignored in many interfacial reactions because of the strength of the interactions. We examined the interactions of SO42- and dissolved natural organic molecules with Fe-oxides, and studied the nature of bonding using X-ray and infrared spectroscopy techniques. Our studies suggest that these ions primarily exhibit H-bonded complexes, and the strength of interactions of these molecules and their coordination environments on particle surfaces are dictated by water and proton activity in the sample. High abundance of these ions in natural waters and their weak interactions play an important role on the interfacial reactions, nucleation and stability of mineral phases, and retention of organic carbon in soils and sediments. A review of behavior of weakly complexing ions at interfaces, and the results of our studies will be presented.

Dominating role of weakly complexing ions at the mineral-water interfaces

253rd National Meeting (2017)

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