Properties of aqueous nitrate and nitrite from x-ray absorption spectroscopy

Abstract

Nitrate and nitrite ions are of considerable interest, both for their widespread use in commercial and research contexts and because of their central role in the global nitrogen cycle. The chemistry of atmospheric aerosols, wherein nitrate is abundant, has been found to depend on the interfacial behavior of ionic species. The interfacial behavior of ions is determined largely by their hydration properties; consequently, the study of the hydration and interfacial behavior of nitrate and nitrite comprises a significant field of study. In this work, we describe the study of aqueous solutions of sodium nitrate and nitrite via X-ray absorption spectroscopy (XAS), interpreted in light of first-principles density functional theory electronic structure calculations. Experimental and calculated spectra of the nitrogen K-edge XA spectra of bulk solutions exhibit a large 3.7 eV shift between the XA spectra of nitrate and nitrite resulting from greater stabilization of the nitrogen 1s energy level in nitrate. A similar shift is not observed in the oxygen K-edge XA spectra of NO3 (-) and NO2 (-). The hydration properties of nitrate and nitrite are found to be similar, with both anions exhibiting a similar propensity towards ion pairing.

Insights into the sonochemical synthesis and properties of salt-free intrinsic plutonium colloids

“…The main edge shape itself is split in two peaks, one at 538 eV and the other at 543 eV, that can be attributed to the strong influence of hydrated and/or hydrolysed forms of Pu(IV) on the total oxygen state3132. In addition, the contribution from nitrate ions to the experimental O K-edge NEXAFS spectra of hydrolytic Pu colloid also cannot be completely excluded33. It can be concluded that the difference between the two studied colloids is the stronger influence of hydrolysed Pu(IV) moieties at the surface shell of the smaller colloidal nanoparticles (hydrolytic).…”

Nature of hydration shells of a polyoxy‐anion with a large cationic centre: The case of iodate ion in water

“…The polyoxy‐anions form a major class of ions which have great relevance to various atmospheric and biological systems. These ions have multiple charge centers and their effects on the structure and dynamics of water have been the topic of many earlier studies in the literature …”

Electronic structure of aqueous solutions: Bridging the gap between theory and experiments

“…Unoccupied electronic states can be accessed using other techniques, such as near-edge x-ray absorption fine structure spectroscopy (NEXAFS), which probes the excitation of atomic core electrons to unoccupied molecular orbitals. Because these orbitals are sensitive to the local chemical environment, NEXAFS is more sensitive to the structure and bonding of solutions than x-ray PE spectroscopy, and it has been used to determine the solvation environments of several of the molecules studied here, such as CO 3 2− , HCO 3 − , and NO 3 − ( 28 , 29 ). …”