1
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Uysal A. Aqueous Interfaces in Chemical Separations. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023. [PMID: 37917551 DOI: 10.1021/acs.langmuir.3c02170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/04/2023]
Abstract
Chemical separations play a vital role in refinery and reprocessing of critical materials, such as platinum group metals, rare earths, and actinides. The choice of separation system─whether it is liquid-liquid extraction (LLE), sorbents, or membranes─depends on specific needs and applications. In almost all separation processes, the desired metal ions adsorb or transfer across an aqueous interface, such as the solid/liquid interface in sorbents or oil/water interfaces in LLE. Despite these separation technologies being extensively used for decades, our understanding of the molecular-scale mechanisms governing ion adsorption and transport at interfaces remains limited. This knowledge gap presents a significant challenge in meeting the increasing demands for these critical materials due to their growing use in advanced technologies. Fortunately, recent advancements in surface-specific experimental and computational techniques offer promising avenues to bridge this gap and facilitate the development of next-generation separation systems. Interestingly, unanswered questions regarding interfacial phenomena in chemical separations hold great relevance to various fields, including energy storage, geochemistry, and atmospheric chemistry. Therefore, the model interfacial systems developed for studying chemical separations, such as amphiphilic molecules assembled at a solid/water, air/water, or oil/water interface, may have far-reaching implications, extending beyond separations and opening doors to addressing a wide range of scientific inquiries. This perspective discusses recent interfacial studies elucidating amphiphile-ion interactions in chemical separations of metal ions. These studies provide direct, molecular-scale information about solute and solvent behavior at aqueous interfaces, including multivalent and complex ions in highly concentrated solutions, which play key roles in LLE of critical materials.
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Affiliation(s)
- Ahmet Uysal
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
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2
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El-Sheekh MM, El-Nagar AA, ElKelawy M, Bastawissi HAE. Solubility and stability enhancement of ethanol in diesel fuel by using tri-n-butyl phosphate as a new surfactant for CI engine. Sci Rep 2023; 13:17954. [PMID: 37863955 PMCID: PMC10589253 DOI: 10.1038/s41598-023-45252-7] [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: 09/07/2023] [Accepted: 10/17/2023] [Indexed: 10/22/2023] Open
Abstract
Nowadays, researchers are very interested in improving the stability and solubility of blending diesel fuel with a high percentage of ethanol. As a result, the goal of this paper was to find a way to use the surfactant of Tri-n-butyl phosphate (TBP) substance to blend ethanol with diesel fuel to a level of 40%. Diesel fuel is mixed with ethanol in volumetric proportions of 10%, 20%, 30%, and 40%, as well as a tiny amount of TBP from 1 to 4%. The prepared blends were the subject of an experiment evaluation by fueling a direct injection diesel engine. This engine is a water-cooled, commercial diesel engine, single cylinder, and four-stroke with 12 kW maximum power. The four blends were evaluated as clean fuel mixtures of 10% ethanol/90% diesel/1% TBP, 20% ethanol/80% diesel/2% TBP, 30% ethanol/70% diesel/3% TBP, and 40% ethanol/60% diesel/4% TBP. As the starting fuel, we used 100% diesel to compare the results. The engine's output and emissions have been measured at various engine loads and constant speeds of 1500 rpm. According to the data gathered, even when the percentage of ethanol was increased to 40%, neither the base fuel nor the engine BTE changed significantly. The engine exhaust gas temperature was found to decrease slightly when the proportion of ethanol was increased. When bioethanol is increased to 40% of the base volume, it causes an increase in the combustion of unburned hydrocarbons and CO emissions. However, when the percentage of ethanol was increased from 100% diesel to the base fuel to 40%, CO2 emissions decreased, and O2 emissions slightly increased.
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Affiliation(s)
- Mostafa M El-Sheekh
- Botany Department, Faculty of Science, Tanta University, Tanta, 31527, Egypt.
| | - Aya A El-Nagar
- Microbial Biotechnology Department, Genetic Engineering and Biotechnology Research Institute, University of Sadat City, Sadat City, Egypt
| | - Medhat ElKelawy
- Mechanical Power Engineering Departments, Faculty of Engineering, Tanta University, Tanta, Egypt
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3
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Nayak S, Kumal RR, Lee SE, Uysal A. Elucidating Trivalent Ion Adsorption at Floating Carboxylic Acid Monolayers: Charge Reversal or Water Reorganization? J Phys Chem Lett 2023; 14:3685-3690. [PMID: 37036360 DOI: 10.1021/acs.jpclett.3c00225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
We study the adsorption of trivalent neodymium on floating arachidic acid films at the air-water interface by two complementary surface specific probes, sum frequency generation spectroscopy and X-ray fluorescence near total reflection. In the absence of background ions, neodymium ions compensate for the surface charge of the arachidic acid film at a bulk concentration of 50 μM without any charge reversal. Increasing the bulk concentration to 1 mM does not change the neodymium surface coverage but affects the interfacial water structure significantly. In the presence of a high concentration of NaCl, there is overcharging at 1 mM Nd3+, i.e., 30% more Nd3+ than needed to compensate for the surface charge. These results show that the total coverage of neodymium ions is not enough to describe the complete picture at the interface, and interfacial water and ion coverage needs to be considered together to understand more complex ion adsorption and transport processes.
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Affiliation(s)
- Srikanth Nayak
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Raju R Kumal
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Seung Eun Lee
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Ahmet Uysal
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
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4
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Preferential recovery and separation of rhodium in the concentrated hydrochloric acid using thin-layer oil membrane extraction based on laminar flow. Chem Eng Res Des 2023. [DOI: 10.1016/j.cherd.2023.02.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
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5
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Zarayeneh N, Kumar N, Kalyanaraman A, Clark AE. Dynamic Community Detection Decouples Multiple Time Scale Behavior of Complex Chemical Systems. J Chem Theory Comput 2022; 18:7043-7051. [PMID: 36374620 DOI: 10.1021/acs.jctc.2c00454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Although community or cluster identification is becoming a standard tool within the simulation community, traditional algorithms are challenging to adapt to time-dependent data. Here, we introduce temporal community identification using the Δ-screening algorithm, which has the flexibility to account for varying community compositions, merging and splitting behaviors within dynamically evolving chemical networks. When applied to a complex chemical system whose varying chemical environments cause multiple time scale behavior, Δ-screening is able to resolve the multiple time scales of temporal communities. This computationally efficient algorithm is easily adapted to a wide range of dynamic chemical systems; flexibility in implementation allows the user to increase or decrease the resolution of temporal features by controlling parameters associated with community composition and fluctuations therein.
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Affiliation(s)
- Neda Zarayeneh
- School of Electrical Engineering and Computer Science, Washington State University, Pullman, Washington99164, United States
| | - Nitesh Kumar
- Department of Chemistry, Washington State University, Pullman, Washington99164, United States
| | - Ananth Kalyanaraman
- School of Electrical Engineering and Computer Science, Washington State University, Pullman, Washington99164, United States
| | - Aurora E Clark
- Department of Chemistry, Washington State University, Pullman, Washington99164, United States.,Pacific Northwest National Laboratory, Richland, Washington99354, United States
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6
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Sadhu B, Clark AE. Modulating Aggregation in Microemulsions: The Dispersion by Competitive Intermolecular Interaction Model. J Phys Chem Lett 2022; 13:10981-10987. [PMID: 36404619 DOI: 10.1021/acs.jpclett.2c02658] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
A phenomenological model has been developed for the mechanism of action of phase modifiers as additives that control aggregation phenomena within water-in-oil emulsions. The "Dispersion by Competitive Intermolecular Interaction" model (DCI) explicitly considers the strength and prevalence of different intermolecular interactions that influence the molecular association of amphiphiles, the resulting distribution of aggregate size, and interaggregate interactions that influence phase phenomena. The existing "cosolvent" and "cosurfactant" association models, which describe the distribution of these amphiphiles within the solution, are re-examined in the context of intermolecular interactions. The different contributions of intermolecular interactions to the potential energy landscape of molecular association create distinct regimes within the DCI model that explain prior observations of cosolvent and cosurfactant behavior. The specific system under consideration, the N,N,N',N'-tetraoctyl diglycolamide amphiphile extractant with tributyl phosphate or dihexyl octanamide phase modifier additives, represents a new regime-labeled the polar disruption regime-where strong hydrogen bonding of the phase modifier with the polar-solutes disrupts the internal hydrogen bonding network of the polar micellar core, thereby decreasing aggregate size and narrowing the polydispersity in solution.
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Affiliation(s)
- Biswajit Sadhu
- Health Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai, Maharashtra400085, India
| | - Aurora E Clark
- Department of Chemistry, Washington State University, Pullman, Washington99164, United States
- Department of Chemistry, University of Utah, Salt Lake City, Utah84112, United States
- Pacific Northwest National Laboratory, Richland, Washington99354, United States
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7
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On the mechanisms of ion adsorption to aqueous interfaces: air-water vs. oil-water. Proc Natl Acad Sci U S A 2022; 119:e2210857119. [PMID: 36215494 PMCID: PMC9586313 DOI: 10.1073/pnas.2210857119] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The adsorption of ions to water-hydrophobe interfaces influences a wide range of phenomena, including chemical reaction rates, ion transport across biological membranes, and electrochemical and many catalytic processes; hence, developing a detailed understanding of the behavior of ions at water-hydrophobe interfaces is of central interest. Here, we characterize the adsorption of the chaotropic thiocyanate anion (SCN-) to two prototypical liquid hydrophobic surfaces, water-toluene and water-decane, by surface-sensitive nonlinear spectroscopy and compare the results against our previous studies of SCN- adsorption to the air-water interface. For these systems, we observe no spectral shift in the charge transfer to solvent spectrum of SCN-, and the Gibb's free energies of adsorption for these three different interfaces all agree within error. We employed molecular dynamics simulations to develop a molecular-level understanding of the adsorption mechanism and found that the adsorption for SCN- to both water-toluene and water-decane interfaces is driven by an increase in entropy, with very little enthalpic contribution. This is a qualitatively different mechanism than reported for SCN- adsorption to the air-water and graphene-water interfaces, wherein a favorable enthalpy change was the main driving force, against an unfavorable entropy change.
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8
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Bui T, Frampton H, Huang S, Collins IR, Striolo A, Michaelides A. Water/oil interfacial tension reduction - an interfacial entropy driven process. Phys Chem Chem Phys 2021; 23:25075-25085. [PMID: 34738605 DOI: 10.1039/d1cp03971g] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The interfacial tension (IFT) of a fluid-fluid interface plays an important role in a wide range of applications and processes. When low IFT is desired, surface active compounds (e.g. surfactants) can be added to the system. Numerous attempts have been made to relate changes in IFT arising from such compounds to the specific nature of the interface. However, the IFT is controlled by an interplay of factors such as temperature and molecular structure of surface-active compounds, which make it difficult to predict IFT as those conditions change. In this study, we present the results from molecular dynamics simulations revealing the specific role surfactants play in IFT. We find that, in addition to reducing direct contact between the two fluids, surfactants serve to increase the disorder at the interface (related to interfacial entropy) and consequently reduce the water/oil IFT, especially when surfactants are present at high surface density. Our results suggest that surfactants that yield more disordered interfacial films (e.g. with flexible and/or unsaturated tails) reduce the water/oil IFT more effectively than surfactants which yield highly ordered interfacial films. Our results shed light on some of the factors that control IFT and could have important practical implications in industrial applications such as the design of cosmetics, food products, and detergents.
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Affiliation(s)
- Tai Bui
- Thomas Young Centre and London Centre for Nanotechnology, and Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK. .,BP Exploration Operating Co. Ltd, Chertsey Road, Sunbury-on-Thames TW16 7LN, UK.,Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
| | - Harry Frampton
- BP Exploration Operating Co. Ltd, Chertsey Road, Sunbury-on-Thames TW16 7LN, UK
| | - Shanshan Huang
- BP Exploration Operating Co. Ltd, Chertsey Road, Sunbury-on-Thames TW16 7LN, UK
| | - Ian R Collins
- BP Exploration Operating Co. Ltd, Chertsey Road, Sunbury-on-Thames TW16 7LN, UK
| | - Alberto Striolo
- Department of Chemical Engineering, University College London, Gower Street, London WC1E 6BT, UK.,School of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, OK 73019, USA
| | - Angelos Michaelides
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
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9
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Kumar N, Clark AE. Unexpected inverse correlations and cooperativity in ion-pair phase transfer. Chem Sci 2021; 12:13930-13939. [PMID: 34760180 PMCID: PMC8549775 DOI: 10.1039/d1sc04004a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 09/16/2021] [Indexed: 11/21/2022] Open
Abstract
Liquid/liquid extraction is one of the most widely used separation and purification methods, where a forefront of research is the study of transport mechanisms for solute partitioning and the relationships that these have to solution structure at the phase boundary. To date, organized surface features that include protrusions, water-fingers, and molecular hinges have been reported. Many of these equilibrium studies have focused upon small-molecule transport – yet the extent to which the complexity of the solute, and the competition between different solutes, influence transport mechanisms have not been explored. Here we report molecular dynamics simulations that demonstrate that a metal salt (LiNO3) can be transported via a protrusion mechanism that is remarkably similar to that reported for H2O by tri-butyl phosphate (TBP), a process that involves dimeric assemblies. Yet the LiNO3 out-competes H2O for a bridging position between the extracting TBP dimer, which in-turn changes the preferred transport pathway of H2O. Examining the electrolyte concentration dependence on ion-pair transport unexpectedly reveals an inverse correlation with the extracting surfactant concentration. As [LiNO3] increases, surface adsorbed TBP becomes a limiting reactant in correlation with an increased negative surface charge induced by excess interfacial NO3−, however the rate of transport is enhanced. Within the highly dynamic interfacial environment, we hypothesize that this unique cooperative effect may be due to perturbed surface organization that either decreases the energy of formation of transporting protrusion motifs or makes it easier for these self-assembled species to disengage from the surface. A forefront of research in separations science (specifically liquid–liquid extraction) is the study of transport mechanisms for solute partitioning, and the relationships that these have to solution structure at the phase boundary.![]()
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Affiliation(s)
- Nitesh Kumar
- Department of Chemistry, Washington State University Pullman Washington 99164 USA
| | - Aurora E Clark
- Department of Chemistry, Washington State University Pullman Washington 99164 USA.,Pacific Northwest National Laboratory Richland Washington 99354 USA
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10
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Ta AT, Golzwarden JVA, Jensen MP, Vyas S. Behaviors of ALSEP Organic Extractants: an Atomic Perspective Derived from Molecular Dynamics Simulation. SOLVENT EXTRACTION AND ION EXCHANGE 2021. [DOI: 10.1080/07366299.2021.1956104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- An T. Ta
- Department of Chemistry, Colorado School of Mines, Golden, Colorado, United States
| | | | - Mark P. Jensen
- Department of Chemistry, Colorado School of Mines, Golden, Colorado, United States
- Nuclear Science and Engineering Program, Colorado School of Mines, Golden, Colorado, United States
| | - Shubham Vyas
- Department of Chemistry, Colorado School of Mines, Golden, Colorado, United States
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11
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Kumar N, Servis MJ, Clark AE. Uranyl Speciation in the Presence of Specific Ion Gradients at the Electrolyte/Organic Interface. SOLVENT EXTRACTION AND ION EXCHANGE 2021. [DOI: 10.1080/07366299.2021.1954323] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- Nitesh Kumar
- Department of Chemistry, Washington State University, Pullman, Washington, USA
| | - Michael J. Servis
- Department of Chemistry, Washington State University, Pullman, Washington, USA
| | - Aurora E. Clark
- Department of Chemistry, Washington State University, Pullman, Washington, USA
- Pacific Northwest National Laboratory, Richland, Washington, USA
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12
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Nayak S, Kumal RR, Liu Z, Qiao B, Clark AE, Uysal A. Origins of Clustering of Metalate-Extractant Complexes in Liquid-Liquid Extraction. ACS APPLIED MATERIALS & INTERFACES 2021; 13:24194-24206. [PMID: 33849269 DOI: 10.1021/acsami.0c23158] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Effective and energy-efficient separation of precious and rare metals is very important for a variety of advanced technologies. Liquid-liquid extraction (LLE) is a relatively less energy intensive separation technique, widely used in separation of lanthanides, actinides, and platinum group metals (PGMs). In LLE, the distribution of an ion between an aqueous phase and an organic phase is determined by enthalpic (coordination interactions) and entropic (fluid reorganization) contributions. The molecular scale details of these contributions are not well understood. Preferential extraction of an ion from the aqueous phase is usually correlated with the resulting fluid organization in the organic phase, as the longer-range organization increases with metal loading. However, it is difficult to determine the extent to which organic phase fluid organization causes, or is caused by, metal loading. In this study, we demonstrate that two systems with the same metal loading may impart very different organic phase organizations and investigate the underlying molecular scale mechanism. Small-angle X-ray scattering shows that the structure of a quaternary ammonium extractant solution in toluene is affected differently by the extraction of two metalates (octahedral PtCl62- and square-planar PdCl42-), although both are completely transferred into the organic phase. The aggregates formed by the metalate-extractant complexes (approximated as reverse micelles) exhibit a more long-range order (clustering) with PtCl62- compared to that with PdCl42-. Vibrational sum frequency generation spectroscopy and complementary atomistic molecular dynamics simulations on model Langmuir monolayers indicate that the two metalates affect the interfacial hydration structures differently. Furthermore, the interfacial hydration is correlated with water extraction into the organic phase. These results support a strong relationship between the organic phase organizational structure and the different local hydration present within the aggregates of metalate-extractant complexes, which is independent of metalate concentration.
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Affiliation(s)
- Srikanth Nayak
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Raju R Kumal
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Zhu Liu
- Department of Chemistry, Washington State University, Pullman, Washington 99164, United States
| | - Baofu Qiao
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Aurora E Clark
- Department of Chemistry, Washington State University, Pullman, Washington 99164, United States
| | - Ahmet Uysal
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
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13
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Servis AG, Parsons-Davis T, Moody KJ, Gharibyan N. Transport Modeling of Kinetically Limited Microscale Extraction Systems: Droplet and Supported Liquid Membrane Separations. Ind Eng Chem Res 2021. [DOI: 10.1021/acs.iecr.1c00740] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Anna G. Servis
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, United States
| | - Tashi Parsons-Davis
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, United States
| | - Kenton J. Moody
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, United States
| | - Narek Gharibyan
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, United States
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14
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Servis MJ, Clark AE. Cluster Identification Using Modularity Optimization to Uncover Chemical Heterogeneity in Complex Solutions. J Phys Chem A 2021; 125:3986-3993. [PMID: 33929191 DOI: 10.1021/acs.jpca.0c11320] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Structural heterogeneity is commonly manifested in solutions and liquids that feature competition of different interparticle forces. Identifying and characterizing heterogeneity across different length scales requires multimodal experimental measurement and/or the application of new techniques for the interrogation of atomistic simulation data. Within the latter, the parsing of networks of interparticle interactions (chemical networks) has been demonstrated to be a valuable tool for identifying subensembles of chemical environments. However, chemical networks can adopt a wide variety of topologies that challenge generalizable methods for identifying heterogeneous behavior, and few network analysis algorithms have been proposed for multiscale resolution. In this study, we apply a method of partitioning using the graph theoretic concept of clusters and communities. Using a modularity optimization algorithm, the cluster partition creates subgraphs based on their relative internal and external connectivities. The methodology is tested on two soft matter systems that have significantly different network topologies so as to probe its ability to identify multiple scale features and its generalizability. A binary Lennard-Jones fluid is first examined, where one component causes subgraphs that have high internal network connectivity yet are still connected to the rest of the interparticle network of interactions. The impact of connectivity and edge weighting on the cluster partition is investigated. In the second system, hierarchically organized molecular structures comprised of hydrogen bonded water molecules are identified at a liquid/liquid interface. These structures have a much more sparse network with significantly varied internal connectivity that is a challenge to differentiate from the background hydrogen bonding network of water molecules at the instantaneous interface. The organized macrostructures are effectively isolated from the background network using the cluster partition, and a time-dependent implementation allows us to reveal their reactivity. These studies indicate that cluster partitioning based upon intermolecular network connectivity patterns is broadly generalizable, depending only on user-defined intermolecular connectivity, is operable across different length scales, and is extensible to the study of dynamic phenomena.
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Affiliation(s)
- Michael J Servis
- Department of Chemistry, Washington State University, Pullman, Washington 99164, United States
| | - Aurora E Clark
- Department of Chemistry, Washington State University, Pullman, Washington 99164, United States.,Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99164, United States.,Pacific Northwest National Laboratory, Richland, Washington 99354, United States
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15
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Kelly N, Doert T, Hennersdorf F, Gloe K. Synergistic lanthanide extraction triggered by self-assembly of heterodinuclear Zn(II)/Ln(III) Schiff base/carboxylic acid complexes. SOLVENT EXTRACTION AND ION EXCHANGE 2021. [DOI: 10.1080/07366299.2021.1876383] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- Norman Kelly
- Department of Process Metallurgy, Helmholtz-Zentrum Dresden-Rossendorf, Helmholtz Institute Freiberg for Resource Technology, Freiberg, Germany
- TU Dresden, School of Sciences, Faculty of Chemistry and Food Chemistry, Dresden, Germany
| | - Thomas Doert
- TU Dresden, School of Sciences, Faculty of Chemistry and Food Chemistry, Dresden, Germany
| | - Felix Hennersdorf
- TU Dresden, School of Sciences, Faculty of Chemistry and Food Chemistry, Dresden, Germany
| | - Karsten Gloe
- TU Dresden, School of Sciences, Faculty of Chemistry and Food Chemistry, Dresden, Germany
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16
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Abstract
Despite their prevalent use as a surrogate for partitioning of pharmacologically active solutes across lipid membranes, the mechanism of transport across water/octanol phase boundaries has remained unexplored. Using molecular dynamics, graph theoretical, cluster analysis, and Langevin dynamics, we reveal an elegant mechanism for the simplest solute, water. Self-assembled octanol at the interface reversibly binds water and swings like the hinge of a door to bring water into a semi-organized second interfacial layer (a “bilayer island”). This mechanism is distinct from well-known lipid flipping and water transport processes in protein-free membranes, highlighting important limitations in the water/octanol proxy. Interestingly, the collective and reversible behavior is well-described by a double well potential energy function, with the two stable states being the water bound to the hinge on either side of the interface. The function of the hinge for transport, coupled with the underlying double well energy landscape, is akin to a molecular switch or shuttle that functions under equilibrium and is driven by the differential free energies of solvation of H2O across the interface. This example successfully operates within the dynamic motion of instantaneous surface fluctuations, a feature that expands upon traditional approaches toward controlled solute transport that act to avoid or circumvent the dynamic nature of the interface. Despite their pharmacological relevance, the mechanism of transport across water/octanol phase boundaries has remained unexplored. Octanol molecular assemblies are demonstrated to reversibly bind water and swing like the hinge of a door.![]()
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Affiliation(s)
- Zhu Liu
- Department of Chemistry, Washington State University Pullman Washington 99164 USA
| | - Aurora E Clark
- Department of Chemistry, Washington State University Pullman Washington 99164 USA .,Voiland School of Chemical Engineering and Bioengineering, Washington State University Pullman WA 99164 USA.,Pacific Northwest National Laboratory Richland Washington 99352 USA
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17
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Chowdhury AU, Lin L, Doughty B. Hydrogen-Bond-Driven Chemical Separations: Elucidating the Interfacial Steps of Self-Assembly in Solvent Extraction. ACS APPLIED MATERIALS & INTERFACES 2020; 12:32119-32130. [PMID: 32551500 DOI: 10.1021/acsami.0c06176] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Chemical separations, particularly liquid extractions, are pervasive in academic and industrial laboratories, yet a mechanistic understanding of the events governing their function are obscured by interfacial phenomena that are notoriously difficult to measure. In this work, we investigate the fundamental steps of ligand self-assembly as driven by changes in the interfacial H-bonding network using vibrational sum frequency generation. Our results show how the bulk pH modulates the interfacial structure of extractants at the buried oil/aqueous interface via the formation of unique H-bonding networks that order and bridge ligands to produce self-assembled aggregates. These extended H-bonded structures are key to the subsequent extraction of Co2+ from the aqueous phase in promoting micelle formation and subsequent ejection of the said micelle into the oil phase. The combination of static and time-resolved measurements reveals the events underlying complexities of liquid extractions at high [Co2+]:[ligand] ratios by showing an evolution of interfacially assembled structures that are readily tuned on a chemical basis by altering the compositions of the aqueous phase. The results of this work point to new principles to design-applied separations through the manipulation of surface charge, electrostatic screening, and the associated H-bonding networks that arise at the interface to facilitate organization and subsequent extraction.
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Affiliation(s)
- Azhad U Chowdhury
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Lu Lin
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Benjamin Doughty
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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18
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Nayak S, Lovering K, Bu W, Uysal A. Anions Enhance Rare Earth Adsorption at Negatively Charged Surfaces. J Phys Chem Lett 2020; 11:4436-4442. [PMID: 32406689 DOI: 10.1021/acs.jpclett.0c01091] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Anions are expected to be repelled from negatively charged surfaces. At aqueous interfaces, however, ion-specific effects can dominate over direct electrostatic interactions. Using multiple in situ surface sensitive experimental techniques, we show that surface affinities of SCN- anions are so strong that they can adsorb at a negatively charged floating monolayer at the air-aqueous interface. This extreme example of ion-specific effects may be very important for understanding complex processes at aqueous interfaces, such as chemical separations of rare earth metals. Adsorbed SCN- ions at the floating monolayer increase the overall negative charge density, leading to enhanced trivalent rare earth adsorption. Surface sensitive X-ray fluorescence measurements show that the surface coverage of Lu3+ ions can be triple the apparent surface charge of the floating monolayer in the presence of SCN-. Comparison to NO3- samples shows that the effects are strongly dependent on the character of the anion, providing further evidence of ion-specific effects dominating over electrostatics.
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Affiliation(s)
- Srikanth Nayak
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Kaitlin Lovering
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Wei Bu
- NSF's ChemMatCARS, The University of Chicago, Chicago, Illinois 60637, United States
| | - Ahmet Uysal
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
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Alvarado E, Liu Z, Servis MJ, Krishnamoorthy B, Clark AE. A Geometric Measure Theory Approach to Identify Complex Structural Features on Soft Matter Surfaces. J Chem Theory Comput 2020; 16:4579-4587. [DOI: 10.1021/acs.jctc.0c00260] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Enrique Alvarado
- Department of Mathematics and Statistics, Washington State University, Pullman, Washington 99164, United States
| | - Zhu Liu
- Department of Chemistry, Washington State University, Pullman, Washington 99164, United States
| | - Michael J. Servis
- Department of Chemistry, Washington State University, Pullman, Washington 99164, United States
| | - Bala Krishnamoorthy
- Department of Mathematics and Statistics, Washington State University, Vancouver, Washington 98686, United States
| | - Aurora E. Clark
- Department of Chemistry, Washington State University, Pullman, Washington 99164, United States
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Servis MJ, Martinez-Baez E, Clark AE. Hierarchical phenomena in multicomponent liquids: simulation methods, analysis, chemistry. Phys Chem Chem Phys 2020; 22:9850-9874. [PMID: 32154813 DOI: 10.1039/d0cp00164c] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Complex, multicomponent, solutions have often been studied solely through the lens of specific applications of interest. Yet advances to both simulation methodologies (enhanced sampling, etc.) and analysis techniques (network analysis algorithms and others), are creating a trove of data that reveal transcending characteristics across vast compositional phase space. This perspective discusses technical considerations of the reliable and accurate simulations of complex solutions, followed by the advances to analysis algorithms that elucidate coupling of different length and timescale behavior (hierarchical phenomena). The different manifestations of hierarchical phenomena are presented across an array of solution environments, emphasizing fundamental and ongoing science questions. With a more advanced molecular understanding in hand, a quintessential application (solvent extraction) is discussed, where significant opportunities exist to re-imagine the technical scope of an established technology.
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Affiliation(s)
- Michael J Servis
- Department of Chemistry, Washington State University, Pullman, WA 99164, USA.
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Dwadasi BS, Goverapet Srinivasan S, Rai B. Interfacial structure in the liquid-liquid extraction of rare earth elements by phosphoric acid ligands: a molecular dynamics study. Phys Chem Chem Phys 2020; 22:4177-4192. [PMID: 32040116 DOI: 10.1039/c9cp05719f] [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
Solvent extraction (SX), wherein two immiscible liquids, one containing the extractant molecules and the other containing the solute to be extracted are brought in contact to effect the phase transfer of the solute, underpins metal extraction and recovery processes. The interfacial region is of utmost importance in the SX process, since besides thermodynamics, the physical and chemical heterogeneity at the interface governs the kinetics of the process. Yet, a fundamental understanding of this heterogeneity and its implications for the extraction mechanism are currently lacking. We use molecular dynamics (MD) simulations to study the liquid-liquid interface under conditions relevant to the SX of Rare Earth Elements (REEs) by a phosphoric acid ligand. Simulations revealed that the extractant molecules and varying amounts of acid and metal ions partitioned to the interface. The presence of these species had a significant effect on the interfacial thickness, hydrogen bond life times and orientations of the water molecules at the interface. Deprotonation of the ligands was essential for the adsorption of the metal ions at the interface, with these ions forming a number of different complexes at the interface involving one to three extractant molecules and four to eight water molecules. Although the interface itself was rough, no obvious 'finger-like' water protrusions penetrating the organic phase were seen in our simulations. While the results of our work help us gain fundamental insights into the sequence of events leading to the formation of a variety of interfacial complexes, they also emphasize the need to carry out a more detailed atomic level study to understand the full mechanism of extraction of REEs from the aqueous to organic phases by phosphoric acid ligands.
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Affiliation(s)
- Balarama Sridhar Dwadasi
- TCS Research, Tata Research Development and Design Center, 54-B Hadapsar Industrial Estate, Hadapsar, Pune - 411013, Maharashtra, India.
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Clark AE. Amphiphile-Based Complex Fluids: The Self-Assembly Ensemble as Protagonist. ACS CENTRAL SCIENCE 2019; 5:10-12. [PMID: 30693321 PMCID: PMC6346385 DOI: 10.1021/acscentsci.8b00927] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
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