1
|
Fan J, Arrazolo LK, Du J, Xu H, Fang S, Liu Y, Wu Z, Kim JH, Wu X. Effects of Ionic Interferents on Electrocatalytic Nitrate Reduction: Mechanistic Insight. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:12823-12845. [PMID: 38954631 DOI: 10.1021/acs.est.4c03949] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2024]
Abstract
Nitrate, a prevalent water pollutant, poses substantial public health concerns and environmental risks. Electrochemical reduction of nitrate (eNO3RR) has emerged as an effective alternative to conventional biological treatments. While extensive lab work has focused on designing efficient electrocatalysts, implementation of eNO3RR in practical wastewater settings requires careful consideration of the effects of various constituents in real wastewater. In this critical review, we examine the interference of ionic species commonly encountered in electrocatalytic systems and universally present in wastewater, such as halogen ions, alkali metal cations, and other divalent/trivalent ions (Ca2+, Mg2+, HCO3-/CO32-, SO42-, and PO43-). Notably, we categorize and discuss the interfering mechanisms into four groups: (1) loss of active catalytic sites caused by competitive adsorption and precipitation, (2) electrostatic interactions in the electric double layer (EDL), including ion pairs and the shielding effect, (3) effects on the selectivity of N intermediates and final products (N2 or NH3), and (4) complications by the hydrogen evolution reaction (HER) and localized pH on the cathode surface. Finally, we summarize the competition among different mechanisms and propose future directions for a deeper mechanistic understanding of ionic impacts on eNO3RR.
Collapse
Affiliation(s)
- Jinling Fan
- Department of Environmental Engineering, Zhejiang University, Hangzhou, Zhejiang 310058, People's Republic of China
- Zhejiang Provincial Engineering Research Center of Industrial Boiler & Furnace Flue Gas Pollution Control, Hangzhou, Zhejiang 310058, People's Republic of China
| | - Leslie K Arrazolo
- Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06511, United States
| | - Jiaxin Du
- Department of Environmental Engineering, Zhejiang University, Hangzhou, Zhejiang 310058, People's Republic of China
- Zhejiang Provincial Engineering Research Center of Industrial Boiler & Furnace Flue Gas Pollution Control, Hangzhou, Zhejiang 310058, People's Republic of China
| | - Huimin Xu
- Department of Environmental Engineering, Zhejiang University, Hangzhou, Zhejiang 310058, People's Republic of China
- Zhejiang Provincial Engineering Research Center of Industrial Boiler & Furnace Flue Gas Pollution Control, Hangzhou, Zhejiang 310058, People's Republic of China
| | - Siyu Fang
- Department of Environmental Engineering, Zhejiang University, Hangzhou, Zhejiang 310058, People's Republic of China
- Zhejiang Provincial Engineering Research Center of Industrial Boiler & Furnace Flue Gas Pollution Control, Hangzhou, Zhejiang 310058, People's Republic of China
| | - Yue Liu
- Department of Environmental Engineering, Zhejiang University, Hangzhou, Zhejiang 310058, People's Republic of China
- Zhejiang Provincial Engineering Research Center of Industrial Boiler & Furnace Flue Gas Pollution Control, Hangzhou, Zhejiang 310058, People's Republic of China
| | - Zhongbiao Wu
- Department of Environmental Engineering, Zhejiang University, Hangzhou, Zhejiang 310058, People's Republic of China
- Zhejiang Provincial Engineering Research Center of Industrial Boiler & Furnace Flue Gas Pollution Control, Hangzhou, Zhejiang 310058, People's Republic of China
| | - Jae-Hong Kim
- Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06511, United States
| | - Xuanhao Wu
- Department of Environmental Engineering, Zhejiang University, Hangzhou, Zhejiang 310058, People's Republic of China
- Zhejiang Provincial Engineering Research Center of Industrial Boiler & Furnace Flue Gas Pollution Control, Hangzhou, Zhejiang 310058, People's Republic of China
| |
Collapse
|
2
|
Gómez-González B, Basílio N, Vaz B, Pérez-Lorenzo M, García-Río L. Delving into the Variability of Supramolecular Affinity: Self-Ion Pairing as a Central Player in Aqueous Host-Guest Chemistry. Angew Chem Int Ed Engl 2024; 63:e202317553. [PMID: 38100517 DOI: 10.1002/anie.202317553] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 12/14/2023] [Accepted: 12/15/2023] [Indexed: 12/17/2023]
Abstract
The determination of binding constants is a key matter in evaluating the strength of host-guest interactions. However, the profound impact of self-ion pairing on this parameter is often underrated in aqueous solution, leading in some cases to a misinterpretation of the true potential of supramolecular assemblies. In the present study, we aim to shed further light on this critical factor by exploring the concentration-dependent behavior of a multicharged pillararene in water. Our observations reveal an extraordinary 1-million-fold variability in the affinity of this macrocycle toward a given anion, showcasing the highly dynamic character of electrostatic interactions. We argue that these findings bring to the forefront the inherent determinism that underlies the estimation of affinity constants, a factor profoundly shaped by both the sensitivity of the instrumental technique in use and the intricacies of the experimental design itself. In terms of applications, these results may provide the opportunity to optimize the operational concentrations of multicharged hosts in different scenarios, aiming to achieve their maximum efficiency based on the intended application. Unlocking the potential of this hidden variability may pave the way for the creation of novel molecular materials with advanced functionalities.
Collapse
Affiliation(s)
- Borja Gómez-González
- Department of Physical Chemistry, Universidade de Santiago de Compostela, 15782, Santiago de Compostela, Spain
| | - Nuno Basílio
- Laboratório Associado para a Química Verde (LAQV), Rede de Química e Tecnologia (REQUIMTE), Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, 2829-516, Caparica, Portugal
| | - Belén Vaz
- CINBIO, Universidade de Vigo, 36310, Vigo, Spain
- Galicia Sur Health Research Institute, 36310, Vigo, Spain
| | - Moisés Pérez-Lorenzo
- CINBIO, Universidade de Vigo, 36310, Vigo, Spain
- Galicia Sur Health Research Institute, 36310, Vigo, Spain
| | - Luis García-Río
- Department of Physical Chemistry, Universidade de Santiago de Compostela, 15782, Santiago de Compostela, Spain
| |
Collapse
|
3
|
Chowdhury S, Ghorai PK, Maity NC, Kumbhakar K, Biswas R. Identical Diffusion Distributions and Co-Cluster Formation Dictate Azeotrope Formation: Microscopic Evidences and Experimental Signatures. J Phys Chem B 2023; 127:8417-8431. [PMID: 37735851 DOI: 10.1021/acs.jpcb.3c02486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/23/2023]
Abstract
What selects azeotropic pairs and governs the azeotropic conditions (composition and temperature) is an open and intriguing question. A combined simulation and experimental work presented here investigates this by considering ethanol-water mixtures. We find identical distributions of center-of-mass diffusion coefficients for ethanol and water molecules under the azeotropic condition (95.5 wt % ethanol +4.5 wt % water, Tazeo = 351.1K). Moreover, the particle displacements show strong interspecies correlations at Tazeo. Interestingly, simulated reorientation time distributions become identical at Tazeo but at a composition different from that at which the translational diffusion distributions overlapped. Cluster analyses indicate that solutions at Tazeo with xwater ≤ 15 wt % are more microheterogeneous than those with higher water content, although no anomaly in the composition-dependent solution structural properties was detected. Ethanol-water and ethanol-ethanol interaction energies show pronounced nonideal composition dependence, but the size of the relative fluctuations in them remained small (∼0.5kBT). Rare water-water H-bonding, predominant water-ethanol H-bonding, and a sizable population of "free" water molecules characterize the azeotropic solutions. The red edge excitation spectroscopic (REES) measurements with a dissolved anionic fluorescent dye, coumarin343 (C343), support the predicted solution microheterogeneity by showing a nonmonotonic composition dependence of the excitation energy-induced changes in the fluorescence emission spectral frequencies and bandwidths, the largest changes being under the azeotropic condition. Subsequent dynamic anisotropy measurements reveal a nonmonotonic composition dependence of C343 rotation times with a peak under the azeotropic condition. In summary, equalization of the component translational diffusion coefficients and solution microheterogeneity with regular composition dependence of the solution structure appear to characterize the ethanol-water azeotrope.
Collapse
Affiliation(s)
- Shrestha Chowdhury
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur 741246, India
| | - Pradip Kr Ghorai
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur 741246, India
| | - Narayan Chandra Maity
- Department of Chemical and Biological Sciences, S.N. Bose National Centre for Basic Sciences, Kolkata 700106, India
| | - Kajal Kumbhakar
- Department of Chemical and Biological Sciences, S.N. Bose National Centre for Basic Sciences, Kolkata 700106, India
| | - Ranjit Biswas
- Department of Chemical and Biological Sciences, S.N. Bose National Centre for Basic Sciences, Kolkata 700106, India
| |
Collapse
|
4
|
Pandey PK, Chandra A. Mechanism, Kinetics, and Potential of Mean Force of Evaporation of Water from Aqueous Sodium Chloride Solutions of Varying Concentrations. J Phys Chem B 2023; 127:4602-4612. [PMID: 37163726 DOI: 10.1021/acs.jpcb.2c09004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The mechanism, kinetics, and potential of mean force of evaporation of water from aqueous NaCl solutions are investigated through both unbiased molecular dynamics simulations and also biased simulations using the umbrella sampling method. The results are obtained for aqueous solutions of three different NaCl concentrations ranging from 0.6 to 6.0 m and also for pure water. The rate of evaporation is found to decrease in the presence of ions. It is found that the process of evaporation of a surface water molecule from ionic solutions can be triggered through its collision with another water or chloride ion. Such collisions provide the additional kinetic energy that is required for evaporation. However, when the collision takes place with a Cl- ion, the evaporation of the escaping water also involves a collision with water in the vicinity of the ion at the same time along with the ion-water collision. These two collisions together provide the required kinetic energy for escape of the evaporating water molecule. Thus, the mechanism of evaporation process of ionic solutions can be more complex than that of pure water. The potential of mean force (PMF) of evaporation is found to be positive and it increases with increasing ion concentration. Also, no barrier in the PMF is found to be present for the condensation of water from vapor phase to the surfaces of the solutions. A detailed analysis of the unsuccessful evaporation attempts by surface water molecules is also made in the current study.
Collapse
Affiliation(s)
- Prashant Kumar Pandey
- Department of Chemistry, Indian Institute of Technology Kanpur, Uttar Pradesh, India 208016
| | - Amalendu Chandra
- Department of Chemistry, Indian Institute of Technology Kanpur, Uttar Pradesh, India 208016
| |
Collapse
|
5
|
Impact and Structure of Water in Aqueous Octanol Mixtures: Hz-GHz Dielectric Relaxation Measurements and Computer Simulations. J Photochem Photobiol A Chem 2023. [DOI: 10.1016/j.jphotochem.2023.114600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
|
6
|
Smirnov PR, Grechin OV. X-RAY DIFFRACTION DETERMINATION OF THE STRUCTURE OF THE ION NEAREST ENVIRONMENT IN AQUEOUS SOLUTIONS OF MAGNESIUM CHLORIDE AND NITRATE. J STRUCT CHEM+ 2022. [DOI: 10.1134/s0022476622060087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
|
7
|
Das B, Chandra A. Ab Initio Molecular Dynamics Study of Aqueous Solutions of Magnesium and Calcium Nitrates: Hydration Shell Structure, Dynamics and Vibrational Echo Spectroscopy. J Phys Chem B 2022; 126:528-544. [PMID: 35001626 DOI: 10.1021/acs.jpcb.1c08545] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ab initio molecular dynamics simulations are performed to study the hydration shell structure, dynamics, and vibrational echo spectroscopy of aqueous Mg(NO3)2 and Ca(NO3)2 solutions. The hydration shell structure is probed through calculations of various ion-ion and ion-water radial and spatial distribution functions. On the dynamical side, calculations have been made for the hydrogen bond dynamics of hydration shells and also residence dynamics and lifetimes of water in different solvation environments. Subsequently, we looked at the dynamics of frequency fluctuations of OD modes of heavy water in different hydration environments. Specifically, the temporal decay of spectral observables of two-dimensional infrared (2DIR) spectroscopy, three pulse echo peak shift (3PEPS) measurements and also of time correlations of frequency fluctuations are calculated to investigate the dynamics of vibrational spectral diffusion of water in different hydration environments in these solutions. The OD stretch frequencies of water molecules in the vicinity of both divalent cations are found to be red-shifted and also fluctuating at a slower rate than other water molecules present in the solutions. The Mg2+ ions are found to be strongly hydrated which can be linked to their lower tendency to form contact ion-pairs and essentially no water exchange between the cationic hydration shells and bulk during the time scale of the current simulations. The stronger hydration of Mg2+ ions make their hydration shells structurally and dynamically more rigid and make the dynamics of hydrogen bonds and vibrational spectral diffusion, as revealed through spectral observables of 2DIR and 3PEPS slower than that for the Ca2+ ions. The structural and spectral dynamics of water molecules outside the cationic solvation shells in the Mg(NO3)2 solution are also found to be relatively slower than that of the Ca(NO3)2 solution and pure water which show the effects of stronger electric fields of Mg2+ ions extending beyond their first hydration shells. Also, water molecules in the hydration shells of the NO3- ions are found to relax at a slower rate in the Mg(NO3)2 solution which manifests the effect countercations have on anionic hydration shells for divalent metal nitrate solutions.
Collapse
Affiliation(s)
- Banshi Das
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh 208016, India
| | - Amalendu Chandra
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh 208016, India
| |
Collapse
|
8
|
Das S, Singha PK, Singh AK, Datta A. The Role of Hydrogen Bonding in the Preferential Solvation of 5-Aminoquinoline in Binary Solvent Mixtures. J Phys Chem B 2021; 125:12763-12773. [PMID: 34709811 DOI: 10.1021/acs.jpcb.1c06208] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
5-Aminoquinoline (5AQ) has been used as a fluorescent probe of preferential solvation (PS) in binary solvent mixtures in which the nonpolar component is diethyl ether and the polar component is protic (methanol) or aprotic (acetonitrile). Hence, the roles of solvent polarity and solute-solvent hydrogen bonding have been delineated. Positive deviations of spectral shifts from a linear dependence on the concentration of the polar component, signifying PS, are markedly more pronounced in case of the protic solvent. Solvation dynamics on a nanosecond time scale mark the formation of the solvation shell around the fluorescent probe. Time-resolved area-normalized emission spectra indicate the occurrence of the continuous solvation of the excited state when the polar component is acetonitrile. In contrast, two distinct states were observed when the polar component was methanol, the second state being the hydrogen bonded one. Translational diffusion is the rate-determining step for formation of the solvation shell. The time constant associated with it has been estimated from rise times observed in fluorescence transients monitored at the red end of the fluorescence spectra and also from the time evolution of the spectral width of time-resolved emission spectra.
Collapse
Affiliation(s)
- Sharmistha Das
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Prajit Kumar Singha
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Avinash Kumar Singh
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Anindya Datta
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India
| |
Collapse
|
9
|
Smirnov PR. Structural Parameters of the Nearest Surrounding of Group II
Metal Ions in Oxygen-Containing Solvents. RUSS J GEN CHEM+ 2021. [DOI: 10.1134/s1070363221030129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
|
10
|
Mosallanejad S, Oluwoye I, Altarawneh M, Gore J, Dlugogorski BZ. Interfacial and bulk properties of concentrated solutions of ammonium nitrate. Phys Chem Chem Phys 2020; 22:27698-27712. [PMID: 33242055 DOI: 10.1039/d0cp04874g] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We conducted molecular dynamics (MD) simulations to calculate the density and surface tension of concentrated ammonium nitrate (AN) solutions up to the solubility limit of ammonium nitrate in water, by combining the SPC/E, SPCE/F and TIP4P/2005 water models with OPLS model for ammonium and nitrate ions. This is the first time that the properties of concentrated solutions of nitrates, especially AN, have been studied by molecular dynamics. We effectively account for the polarisation effects by the electronic continuum correction (ECC), practically realised via rescaling of the ionic charges. We found that, the full-charge force field MD simulations overestimate the experimental results, as the ions experience repulsion from the interface and prefer to remain in the subsurface layer and the bulk solution. In contrast, reducing the ionic charges results in the behaviour that fits well with the experimental data. The nitrate anions display a greater propensity for the interface than the ammonium cations. We accurately predict both the density and the rise in the surface tension of concentrated solutions of AN, recommending TIP4P/2005 for water and the scaled-charge OPLS model (OPLS/ECC) for the ions in the solutions. We observe that, the adsorption of anions to the interface accompanies their depletion in the subsurface layer, which is preferentially occupied by cations, resulting in the formation of the electric double layer. We demonstrate the ion deficiency for up to 3 Å below the surface and establish the requirement to include the polarisability effects in the OPLS model for AN. While these results confirmed the findings of the previous studies for dilute solutions, they are new in the solubility limit. Concentrated solutions exhibit a strong effect of the abundance of solute on the coordination numbers of ions and on the degree of ion pairing. Surprisingly, ion pairing decreases significantly at the interface compared with the bulk. The present study identifies OPLS/ECC, along with TIP4P/2005, to yield accurate predictions of physical properties of concentrated AN, with precision required for industrial applications, such as a formulation of emulsion and fuel-oil explosives that now predominate the civilian use of AN. An application of this model will allow one to predict the surface properties of supersaturated solutions of AN which fall outside the capability of the present laboratory experiments but are important industrially.
Collapse
Affiliation(s)
- Sara Mosallanejad
- Discipline of Chemistry and Physics, College of Science, Health, Engineering and Education, Murdoch University, 90 South Street, Murdoch, WA 6150, Australia
| | | | | | | | | |
Collapse
|
11
|
Banerjee P, Bagchi B. Role of local order in anomalous ion diffusion: Interrogation through tetrahedral entropy of aqueous solvation shells. J Chem Phys 2020; 153:154505. [PMID: 33092370 DOI: 10.1063/5.0022580] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Small rigid ions perturb the water structure around them significantly. At constant viscosity, alkali cations (Li+, Na+, and so on) exhibit an anomalous non-monotonic dependence of diffusivity on ion-size, in stark violation of the Stokes-Einstein expression. Although this is a well-known problem, we find that an entropic view of the problem can be developed, which provides valuable insight. The local entropy experienced by the solute ion is relevant here, which leads to the connection with local viscosity, discussed earlier by many. Due to the strong interactions with ions, the translational and rotational entropy of solvation water decreases sharply; however, an opposite effect comes from the disruption of the tetrahedral network structure of water near the charges. We compute the tetrahedral order of water molecules (qtet) around the ion and suitably defined tetrahedral entropy [S(qtet)] that is a contribution to the excess entropy of the system. Our results reveal that although the structural properties of the second shell become nearly identical to the bulk, S(qtet) of the second shell is found to play an important role in giving rise to the non-monotonic ion-size dependence. The detailed study of the static and dynamic fluctuations in qtet and the number of hydration water molecules provides interesting insights into correlation between the structure and dynamics; the smallest static fluctuation of qtet for the first hydration shell water molecules of Li+ is indicative of the iceberg picture. The study of fluctuation properties of qtet and the coordination number also reveals the role of the second hydration layer and could explain the anomalous behavior of the Rb+ ion.
Collapse
Affiliation(s)
- Puja Banerjee
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India
| | - Biman Bagchi
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India
| |
Collapse
|
12
|
Roy S, Patra A, Saha S, Palit DK, Mondal JA. Restructuring of Hydration Shell Water due to Solvent-Shared Ion Pairing (SSIP): A Case Study of Aqueous MgCl 2 and LaCl 3 Solutions. J Phys Chem B 2020; 124:8141-8148. [PMID: 32816482 DOI: 10.1021/acs.jpcb.0c05681] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Hydration of ions plays a crucial role in interionic interactions and associated processes in aqueous media, but selective probing of the hydration shell water is nontrivial. Here, we introduce Raman difference with simultaneous curve fitting (RD-SCF) analysis to extract the OH-stretch spectrum of hydration shell water, not only for the fully hydrated ions (Mg2+, La3+, and Cl-) but also for the ion pairs. RD-SCF analyses of diluted MgCl2 (0.18 M) and LaCl3 (0.12 M) solutions relative to aqueous NaCl of equivalent Cl- concentrations provide the OH-stretch spectra of water in the hydration shells of fully hydrated Mg2+ and La3+ cations relative to that of Na+. Integrated intensities of the hydration shell spectra of Mg2+ and La3+ ions increase linearly with the salt concentration (up to 2.0 M MgCl2 and 1.3 M LaCl3), which suggests no contact ion pair (CIP) formation in the MgCl2 and LaCl3 solutions. Nevertheless, the band shapes of the cation hydration shell spectra show a growing signature of Cl--associated water with the rising salt concentration, which is a manifestation of the formation of a solvent-shared ion pair (SSIP). The OH-stretch spectrum of the shared/intervening water in the SSIP, retrieved by second-round RD-SCF analysis (2RD-SCF), shows that the average H-bonding of the shared water is weaker than that of the hydration water of the fully hydrated cation (Mg2+ or La3+) but stronger than that of the anion (Cl-). The shared water displays an overall second-order dependence on the concentration of the interacting ions, unveiling 1:1 stoichiometry of the SSIP formed between Mg2+ and Cl- as well as La3+ and Cl-.
Collapse
Affiliation(s)
- Subhadip Roy
- Radiation & Photochemistry Division, Bhabha Atomic Research Centre, Homi Bhabha National Institute, Mumbai 400085, India
| | - Animesh Patra
- School of Chemistry, Centre for Excellence in Basic Sciences, Mumbai 400098, India
| | - Subhamoy Saha
- Radiation & Photochemistry Division, Bhabha Atomic Research Centre, Homi Bhabha National Institute, Mumbai 400085, India
| | - Dipak K Palit
- School of Chemistry, Centre for Excellence in Basic Sciences, Mumbai 400098, India
| | - Jahur Alam Mondal
- Radiation & Photochemistry Division, Bhabha Atomic Research Centre, Homi Bhabha National Institute, Mumbai 400085, India
| |
Collapse
|
13
|
|
14
|
Das B, Mondal S, Chandra A. Two-Dimensional Infrared Spectroscopy of Aqueous Solutions of Metal Nitrates: Slowdown of Spectral Diffusion in the Presence of Divalent Cations. J Phys Chem B 2020; 124:7391-7404. [PMID: 32790404 DOI: 10.1021/acs.jpcb.0c03471] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The hydrogen-bonded network of water can be affected both structurally and dynamically by the presence of ions. In the present study, we have considered three aqueous solutions of metal nitrates to investigate the effects of divalent cations (Mg2+ and Ca2+), compared to that of monovalent Na+ ions, on hydrogen-bond fluctuations and vibrational spectral diffusion through calculations of linear and two-dimensional infrared spectra of these solutions at room temperature. We have employed the methods of molecular dynamics simulations using effective polarizable models of ions combined with quantum mechanical calculations of transition variables and statistical mechanical calculations of spectral response functions of vibrational spectroscopy. Divalent cations are found to have much stronger and longer-ranged effects on the structure and dynamics of the hydrogen-bonded network than that induced by the monovalent sodium ions. The blue shifts in the calculated linear spectra are found to follow the Hofmeister trend for the cations. The 2D-IR spectral lineshape and intensity corresponding to three-pulse echo peak shift (3PEPS) experiments are calculated. The timescales of these nonlinear spectral responses and also frequency-time correlations show significant slowing down of spectral diffusion for solutions containing divalent Mg2+ and Ca2+ ions compared to the corresponding dynamics of the solution containing Na+ ions. Unlike NaNO3 solution, the relaxation of frequency and dipole orientational fluctuations of anion-bound water in Mg(NO3)2 and Ca(NO3)2 solutions are found to be somewhat slower than bulk water, which can be attributed to the presence of divalent cations whose effects go beyond their first solvation shells. This is also seen in the dynamics of bulk water in these solutions which is found to be notably slower for the solutions containing divalent cations than that in the NaNO3 solution. Unlike Mg2+ and Ca2+ ions, no specific cationic effect is observed for the Na+ ions.
Collapse
Affiliation(s)
- Banshi Das
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Subhadip Mondal
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Amalendu Chandra
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
| |
Collapse
|
15
|
Kolafa J. Pressure in Molecular Simulations with Scaled Charges. 1. Ionic Systems. J Phys Chem B 2020; 124:7379-7390. [PMID: 32790401 DOI: 10.1021/acs.jpcb.0c02641] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Charge scaling, rationalized as MDEC (molecular dynamics in electronic continuum) or ECC (electronic continuum correction), has become a widely used simple approach to how to avoid self-consistent induced dipoles yet approximately take into account the effects of electronic polarizability. It has been assumed that the continuum permittivity does not depend on density; in turn, pressure is calculated by standard formulas. In this work, we elaborate a complementary approximation of density-independent molecular polarizability and derive formulas for pressure corrections within the MDEC framework; real behavior lies between these two extremes. The pressure corrections for test ionic systems are huge and negative, leading to sizable densities in constant-pressure MDEC simulations. A comparison of MDEC results with equivalent polarizable systems gives a good pressure match for a crystal but very low MDEC pressures for ionic liquids. These results witness about the importance of a correct density dependence not only of continuum permittivity in MDEC simulations but also of polarizability in polarizable simulations.
Collapse
Affiliation(s)
- Jiří Kolafa
- Department of Physical Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28 Praha 6, Czech Republic
| |
Collapse
|
16
|
Yadav S, Chandra A. Solvation Shell of the Nitrite Ion in Water: An Ab Initio Molecular Dynamics Study. J Phys Chem B 2020; 124:7194-7204. [PMID: 32706258 DOI: 10.1021/acs.jpcb.0c02221] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We performed ab initio molecular dynamics simulation of a nitrite ion in water to investigate the structural and dynamical properties of its hydration shell. The nitrite ion is found to exhibit strong asymmetry toward hydrogen bonding due to its two different types of hydrogen bond acceptor sites. This difference is better captured through further partitioning of the hydration shell into its proximal and distal regions. The frequency shifts of the stretch modes of hydration shell water reveal that the nitrogen site forms a stronger hydrogen bond than its oxygen sites with the latter forming hydrogen bonds, which are similar in strength to that between a pair of water molecules. The escape dynamics of water from the hydration shell is found to be rather slow, which seems to classify the nitrite ion as a structure-maker. However, the dynamics of orientational and hydrogen bond relaxation reveal a faster mobility of water molecules in the hydration shell than bulk water in spite of strong ion-water interactions. It is found that the nitrite ion can hold water molecules in its solvation shell and still make them rotate fast in its vicinity through switching of their hydrogen bonds between its nitrogen and oxygen acceptor sites. The dipole moment of the solute in water is also calculated in the present study.
Collapse
Affiliation(s)
- Sushma Yadav
- Department of Chemistry, Indian Institute of Technology Kanpur, 208016 Kanpur, India
| | - Amalendu Chandra
- Department of Chemistry, Indian Institute of Technology Kanpur, 208016 Kanpur, India
| |
Collapse
|
17
|
Pedersen PD, Mikkelsen KV, Johnson MS. The unexpected effect of aqueous ion pairs on the forbidden n →π* transition in nitrate. Phys Chem Chem Phys 2020; 22:11678-11685. [PMID: 32406445 DOI: 10.1039/d0cp00958j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Aqueous nitrate is ubiquitous in the environment, found for example in stratospheric clouds, tropospheric particulate matter, rain and snow, fertilized fields, rivers and the ocean. Its photolysis is initiated by absorption into the strongly forbidden n →π* transition. Photolysis reactivates deposited nitrate, releasing nitrogen oxides, and UV light is commonly used to break down nitrate pollution. The transition is doubly forbidden unless its symmetry is broken, giving a powerful means of probing the interactions of nitrate with its environment and of using experiment to validate the results of theory. In this study we demonstrate the remarkably different effects of the addition of a series of mono- and di-valent metal chlorides on the nitrate UV transition. While they all shift the transition to shorter wavelengths, the shift changes significantly from one to another. For the monovalent series Li+, Na+, K+, the blue shift decreases down the column being strongest for Li+ and weakest for K+. For the divalent series Mg2+, Ca2+, Ba2+, the opposite effect is observed with the energy shift of Ba2+ being an order of magnitude larger than for Mg2+. The absorption intensity also changes; the addition of Na+ and K+ decrease intensity whereas Li+ increases intensity. For the divalent cations an increase is seen for all three members of the series Mg2+, Ca2+ and Ba2+. Paradoxically, the effect of addition of CaCl2 to the solution is to decrease the environmental photolysis rate of nitrate; despite the increase in intensity, Ca2+ blue shifts the peak position above the tropospheric photolysis threshold around 300 nm. Using computational chemistry we conclude that the effects are due to the microscopic interactions of the nitrate anion and not continuum effects. Two microscopic mechanisms are investigated in detail, the formation of a nitrate monohydrate cluster and a contact ion pair. The contact ion pair shows the potential for significant impact on the energy and intensity of the transition.
Collapse
Affiliation(s)
- Pernille D Pedersen
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark.
| | | | | |
Collapse
|
18
|
Bley M, Duvail M, Guilbaud P, Dufrêche JF. Activity Coefficients of Aqueous Sodium, Calcium, and Europium Nitrate Solutions from Osmotic Equilibrium MD Simulations. J Phys Chem B 2018; 122:7726-7736. [DOI: 10.1021/acs.jpcb.8b04950] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Michael Bley
- ICSM, CEA, CNRS, ENSCM, Univ Montpellier, BP
17171, F-30207 Bagnols-sur-Cèze, France
| | - Magali Duvail
- ICSM, CEA, CNRS, ENSCM, Univ Montpellier, BP
17171, F-30207 Bagnols-sur-Cèze, France
| | - Philippe Guilbaud
- Nuclear Energy Division, Research Department on Mining and Fuel Recycling Processes (SPDS/LILA), CEA, BP 17171, F-30207 Bagnols sur Cèze, France
| | | |
Collapse
|