Nitric Acid−Water Interaction Probed via Isolation in Carbon Tetrachloride

Kuo, Margaret; David, A.; Kamelamela, Noelani; White, Mike; Shultz, Mary Jane

doi:10.1021/jp067131s

Cited by 29 publications

(32 citation statements)

References 44 publications

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“…[38][39][40][41][42] However, there are relatively few studies of the interactions of HNO 3 with such surface-bound organics. Shultz and coworkers 43 showed that HNO 3 in CCl 4 was undissociated, while Donaldson and coworkers 4 have shown that HNO 3 adsorbed into an organic film could photodissociate to generate gas phase NO 2 and/or HONO. In this case, the organic acted as a photosensitizer.…”

Section: Introductionmentioning

confidence: 99%

Experimental and theoretical studies of the interaction of gas phase nitric acid and water with a self-assembled monolayer

Moussa

Stern

Raff

et al. 2013

Phys. Chem. Chem. Phys.

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Experimental and theoretical studies of the interaction of gas phase nitric acid and water with a self-assembled monolayer surface of a germanium infrared-transmitting attenuated total reflectance (ATR) crystal that was coated with a thin layer of silicon oxide (SiO x ). The SAM was exposed at 298 AE 2 K to dry HNO 3 in a flow of N 2 , followed by HNO 3 in humid N 2 at a controlled relative humidity (RH) between 20-90%. For comparison, similar studies were carried out using a similar crystal without the SAM coating. Changes in the surface were followed using Fourier transform infared spectroscopy (FTIR). In the case of the SAMcoated crystal, molecular HNO 3 and smaller amounts of NO 3 À ions were observed on the surface upon exposure to dry HNO 3 . Addition of water vapor led to less molecular HNO 3 and more H 3 O + and NO 3 À complexed to water, but surprisingly, molecular HNO 3 was still evident in the spectra up to 70% RH.This suggests that part of the HNO 3 observed was initially trapped in pockets within the SAM and shielded from water vapor. After increasing the RH to 90% and then exposing the film to a flow of dry N 2 , molecular nitric acid was regenerated, as expected from recombination of protons and nitrate ions as water evaporated. The nitric acid ultimately evaporated from the film. On the other hand, exposure of the SAM to HNO 3 and H 2 O simultaneously gave only hydronium and nitrate ions. Molecular dynamics simulations of defective SAMs in the presence of HNO 3 and water predict that nitric acid intercalates in defects as a complex with a single water molecule that is protected by alkyl chains from interacting with additional water molecules. These studies are consistent with the recently proposed hydrophobic nature of HNO 3 . Under atmospheric conditions, if HNO 3 is formed in organic layers on surfaces in the boundary layer, e.g. through NO 3 or N 2 O 5 reactions, it may exist to a significant extent in its molecular form rather than fully dissociated to nitrate ions. IntroductionNitric acid is considered to be the end-product of oxidation of oxides of nitrogen in the atmosphere. 1 This acid reacts with ammonia and amines to form solid or aqueous phase nitrate particles, and can also be taken up into other types of atmospheric particles. Removal of gaseous HNO 3 and particulate nitrates takes place primarily through wet and dry deposition, in what were once considered to be terminal removal processes. However, there are now a number of laboratory and field studies that suggest that nitric acid can be converted back into gaseous oxides of nitrogen such as NO, NO 2 and HONO. 2-8Nitric acid is a strong acid, but it requires a cluster of at least four water molecules to dissociate in the gas phase. [9][10][11] In bulk aqueous solutions and on ice, nitric acid can form hydrates with 1, 2 or 3 water molecules, depending on the concentration. 12-24 Such hydrates, as well as the HNO 3 dimer, have also been seen on solid surfaces during the hydrolysis of NO 2 at

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Section: Introductionmentioning

confidence: 99%

Experimental and theoretical studies of the interaction of gas phase nitric acid and water with a self-assembled monolayer

Moussa

Stern

Raff

et al. 2013

Phys. Chem. Chem. Phys.

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“…The dodecane/water interfacial tension, using the TIP3P water model [36] is also reproduced for the sake of benchmarking (with a value of 51.2 mNm −1 being obtained relative to the experimental value of 50.74 ± 0.08 mNm −1 [37]). In the single-phase system that is the focus of this work, the TIP3P water model [36] was used along with the HNO 3 parameters of [38] which uses the molecular (undissociated) form that is congruent with experimental IR [39] and ab-initio theoretical predictions. [40,18] Additional details regarding the force field parameters are provided in the Supporting Information (see Figure S1, Table S3-S4).…”

Section: Simulation Protocolmentioning

confidence: 99%

Molecular Dynamics and Network Analysis Reveal the Contrasting Roles of Polar Solutes Within Organic Phase Amphiphile Aggregation

Sadhu

Clark

2022

Preprint

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Amphiphile self-assembly in non-polar media is often enhanced by polar co-solutes. This is observed within many biphasic separations processes, where amphiphiles mediate transport of water and acid into organic solution. A myriad of competitive intermolecular interactions have thus far prevented a fundamental understanding of the individual and dual role of these polar solutes upon amphiphile self-assembly in non-polar media. Toward this end, the current work employs classical molecular dynamics and intermolecular network analyses to deconstruct the individual affects of water and nitric acid upon the self-assembly of N,N,N\textsuperscript{$'$},N{$'$}-tetraoctyl-3-oxapentanediamide (TODGA), a prevalent amphiphile extractant used in metal ion separations. In the absence of acid, and at low water concentration, H$_2$O is found to promote local dimer and trimer formation of TODGA, however as [H$_2$O]$_{org}$ increases, preferential self-solvation leads to large (H$_2$O)$_n$ clusters that cause TODGA clusters to sorb to the (H$_2$O)$_n$ periphery and supports extended aggregation. Addition of HNO$_3$ to the humid solutions disrupts the water hydrogen bond network and inhibits the formation of large water clusters - thus preventing extended aggregation behavior and encouraging local aggregation. Prior experimental observations of enhanced TODGA self-assembly under these conditions are attributed primarily to the role of water rather than co-extracted HNO$_3$, thus providing valuable new insight into the means by which extractant aggregation can be tuned within separations processes. The different roles of polar co-solutes, that derive from their individual hydrogen bonding capabilities and competitive interactions in the context of preferred solvation environments, is of fundamental importance amphiphile behavior in non-polar media.

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“…As part of the benchmarking process we note that the employed parameters reproduce the correct density of 0.1 M TODGA in dodecane as (predicted to be 0.788 gL −1 relative to the experimental value of 0.759 gL −1 33 ), and measured diffusion coefficient 34 (see Results section and Supporting Information). The TIP3P water model 35 was used along with the HNO 3 parameters of Servis et al 21 which uses the molecular (undissociated) form that is congruent with experimental IR 36 and ab initio theoretical predictions. 16,37 Additional details regarding the force field parameters are provided in the Supporting Information (cf.…”

Section: Simulation Protocolmentioning

confidence: 99%

The Contrasting Role of Water and Acid Within Organic Phase Amphiphile Aggregation

Sadhu

Clark

2021

Preprint

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The self-assembly of amphiphiles is often modified by the presence of co-solutes and significant study has examined this behavior in aqueous systems. Much less is known about the role of polar co-solutes upon amphiphile aggregation within non-polar media, however such conditions are relevant to a variety of industrial processes - not the least of which are separations systems like those found in liquid-liquid extraction (LLE). Therein, surface active amphiphiles extract water, acid, and other solutes of interest. Intriguing increases to amphiphile aggregates have been experimentally observed upon water and acid extraction, however a myriad of competitive intermolecular interactions have thus far prevented a fundamental understanding of the individual and dual role of these solutes upon amphiphile self-assembly. Toward this end, this work employs classical molecular dynamics and graph theory analyses to deconstruct the individual affects of water and nitric acid upon the self-assembly of N,N,N',N'-tetraoctyl-3-oxapentanediamide (TODGA), a prevalent amphiphile extractant used in metal ion separations. In the absence of acid, and at low water concentration, H2O is found to promote local dimer and trimer formation of TODGA, however as [H2O]org increases, the preferential solvation of water with itself causes the formation of large water clusters that serve to link large TODGA clusters on the periphery (causing extended aggregation). Addition of HNO3 to the humid solutions disrupts the water hydrogen bond network and inhibits the formation of large water clusters - thus preventing extended aggregation behavior. We rationalize the prior experimental observations as being attributed primarily to the role of water in the self-assembly of TODGA rather than co-extracted HNO3, thus providing valuable new insight into the means by which extractant aggregation can be tuned within LLE processes. In addition, this work differentiates the role of polar solutes upon amphiphile self-assembly via their individual hydrogen bonding capabilities and competitive interactions that disrupt preferred solvation environments.

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Nitric Acid−Water Interaction Probed via Isolation in Carbon Tetrachloride

Cited by 29 publications

References 44 publications

Experimental and theoretical studies of the interaction of gas phase nitric acid and water with a self-assembled monolayer

Experimental and theoretical studies of the interaction of gas phase nitric acid and water with a self-assembled monolayer

Molecular Dynamics and Network Analysis Reveal the Contrasting Roles of Polar Solutes Within Organic Phase Amphiphile Aggregation

The Contrasting Role of Water and Acid Within Organic Phase Amphiphile Aggregation

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