Debye screening, overscreening and specific adsorption in solutions of organic ions

Bresme, Fernando; Robotham, Oliver; Chio, Weng‐I Katherine; Gonzalez, Miguel A.; Kornyshev, Alexei A.

doi:10.1039/c8cp04924f

Cited by 9 publications

(11 citation statements)

References 39 publications

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“…The electrostatic interactions that occur between the adsorbent (hematite) and the adsorbate (As) can be reduced due to the accumulation of ions at the hematite interfaces, the charge screening effect . If this is the case, at pH > pH PZC , the reduced electrostatic repulsion between As species (H 2 AsO 3 – , HAsO 4 2– , AsO 4 3– ) and hematite would lead to an expected increased adsorption.…”

Section: Resultsmentioning

confidence: 99%

Microporous Hematite-Loaded Composite Membrane for Arsenic(III) and Arsenic(V) Removal

Boussouga

Tantish

Schäfer

2023

ACS Appl. Eng. Mater.

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In this work, adsorption and membrane separation were combined to remove adsorbable contaminants from water at lower energy requirements. Such an approach was investigated for arsenic (As) removal with hematite nanoparticles (70 ± 20 nm) immobilized in a microporous (0.2 μm pore size) poly(vinylidene fluoride) (PVDF) membrane. Hematite loading and hydraulic residence time with the role of speciation were investigated for As(III) and As(V) removal using hematite-loaded composite membrane (HLCM). During the flow-through filtration, it was observed 50% removal for As(III), while only 15% As(V) was removed at pH 8 with 2.6 mg/cm2 hematite loading, equivalent to uptakes of 5.5 ± 0.8 μgAs(III)/cm2 and 3.9 ± 0.6 μgAs(V)/cm2. Varying the pH from 2 to 12 and, ultimately, As(III, V) speciation showed a significant impact on the uptake, especially for As(V). In this case, increasing the NaCl concentration from 0.58 to 20 g/L hindered the charge attraction. Arsenic uptake increased with increasing the hematite loading from 0.7 to 3.9 mg/cm2, while the impact of the hydraulic residence time (flux) was observed. Arsenic uptake by this composite membrane requires further improvement in terms of adsorption capacity. Increasing the loading of hematite in the membrane or chemical modifications of hematite to achieve enhanced affinity for As(III, V) will be part of further material modification. From the water treatment perspective, the composite membrane potentially provides effective removal with a lower specific energy consumption compared to nanofiltration.

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Section: Resultsmentioning

confidence: 99%

Microporous Hematite-Loaded Composite Membrane for Arsenic(III) and Arsenic(V) Removal

Boussouga

Tantish

Schäfer

2023

ACS Appl. Eng. Mater.

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“…The concept of integrated charge has been used in many studies to quantify the effects of the ionic structure on the charged surface 42,68,69,71,73,74,82 . Instead of Equation 3, S is often defined by normalizing the integral (second term on the right hand side of the equation) by σ s such that S decays to 1 instead of 0 68,73 .…”

Section: A Ionic Structure Measurementsmentioning

confidence: 99%

“…These experiments have inspired many recent theoretical investigations of highly-concentrated electrolyte systems. Efforts have been made to describe the properties of electrolytes and the non-monotonic behavior of the associated decay length using both analytical approaches 33,34,[65][66][67][68][69] and computer simulations 68,[70][71][72] . Most studies have focused on understanding the nonmonotonic behavior of the decay length by computing pair correlation functions in bulk electrolyte systems 66,70 .…”

Section: Introductionmentioning

confidence: 99%

Ionic Structure and Decay Length in Highly-Concentrated Confined Electrolytes

Anousheh¹,

Solis²,

Jadhao³

2020

Preprint

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We use molecular dynamics simulations of the primitive model of electrolytes to study the ionic structure in aqueous monovalent electrolyte solutions confined by charged planar interfaces over a wide range of electrolyte concentration, interfacial separation, surface charge density, and ion size. The investigations are inspired by recent experiments that have directly measured the increase in the decay length for highlyconcentrated electrolytes with increase in concentration. The behavior of ions in the nanoconfinement created by the interfaces is probed by evaluating the ionic density profiles, net charge densities, screening factors, and decay length associated with the screening of the charged interface. Results show the presence of two distinct regimes of screening behavior as the concentration is changed from 0.1 M to 2.5 M for a wide range of electrolyte systems generated by tuning the interfacial separation, surface charge density, and ionic size. For low concentrations, the screening factor exhibits a monotonic decay to 0 with a decay length that decreases sharply with increasing concentration. For high concentrations ( 1 M), the screening factor has a nonmonotonic behavior signaling charge inversion and formation of structured layers of ions near the interfaces. The decay length under these conditions rises with increasing concentration, exhibiting a power-law behavior. To complement the simulation results, a variational approach is developed that produces charge densities with characteristics consistent with those observed in simulations. The results demonstrate the relation between the rise in the strength of steric correlations and the changes in the screening behavior.

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“…In molecular biology, the ions can be broadly grouped into two categories: mobile ions in the water phase and ions bound to the corresponding macromolecule. The mobile ions in the solvent freely move in response to electrostatic environment and their major role is to provide screening of electrostatic interactions [4,5]. On the other hand, the ions bound to macromolecules are involved in specific interactions with macromolecular moiety and play roles in catalysis, electron/proton transfer reactions and structural stability [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

BION-2: Predicting Positions of Non-Specifically Bound ions on Protein Surface by a Gaussian-based Treatment of Electrostatic Environment

Shashikala

Chakravorty

Pandey

et al. 2020

Preprint

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Abstract Background: Ions play significant roles in biological processes - they may specifically bind to a protein site or bind non-specifically on its surface. Though, the role of specifically bound ions range from actively providing structural compactness via coordination of charge-charge interactions to numerous enzymatic activities, non-specifically surface-bound ions are also crucial to maintaining a protein’s stability, responding to pH and ion concentration changes and contributing to other biological processes. However, experimental determination of positions of non-specifically bound ions is not trivial since they may have low residential time and experience significant thermal fluctuation of their positions. Results: Here we report a new release of a computational method, the BION-2 method, that predicts positions of non-specifically surface-bound ions. The BION-2 utilizes the Gaussian-based treatment of ions within the framework of the modified Poisson-Boltzmann equation, that does not require a sharp boundary between the protein and water phase. Thus, the predictions are done by the balance of the energy of interaction between the protein charges and the corresponding ions, and the de-solvation penalty of the ions as they approach the protein. Conclusions: The BION-2 is tested against experimentally determined ion’s positions, with both X-ray and NMR determined positions, and it is demonstrated that it outperforms the old BION and molecular dynamics tools. The BION-2 is available as a web server as well.

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Debye screening, overscreening and specific adsorption in solutions of organic ions

Abstract: We resolve using atomistic simulations the ions correlations, clustering and charge screening effects or organic electrolytes in dichloroethane.

Cited by 9 publications

References 39 publications

Microporous Hematite-Loaded Composite Membrane for Arsenic(III) and Arsenic(V) Removal

Microporous Hematite-Loaded Composite Membrane for Arsenic(III) and Arsenic(V) Removal

Ionic Structure and Decay Length in Highly-Concentrated Confined Electrolytes

BION-2: Predicting Positions of Non-Specifically Bound ions on Protein Surface by a Gaussian-based Treatment of Electrostatic Environment

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