Special Issue "Ion Specific Effects in Colloid and Surface Science – Where Biology, Chemistry and Physics Meet"

A special issue of Colloids and Interfaces (ISSN 2504-5377).

Deadline for manuscript submissions: closed (31 August 2020).

Special Issue Editor

Dr. István Szilágyi
E-Mail Website
Guest Editor
Department of Physical Chemistry and Materials Science, Faculty of Science and Informatics, University of Szeged, 1 Rerrich Béla tér, 6720 Szeged, Hungary
Interests: nanoparticle; polyelectrolyte; biocatalysis; ionic liquid; colloidal stability
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Special Issue Information

Dear Colleagues,

Ion specificity in colloidal and macromolecular systems has attracted widespread attention in the scientific community since the effect of different salts on the stability of protein solutions was discovered by Franz Hofmeister more than a century ago. Since then, the colloid behavior of biological, environmental, and industry-related systems has been comprehensively studied to understand the behavior of ions of different chemical compositions and valences at various interfaces. Due to the widespread contemporary interest in this topic in the scientific and technological communities, major efforts are being made to investigate the fundamental properties of colloids and surfaces, which can be tuned by different ionic environments.

The goal of this Special Issue is to discuss the most recent results concerning the ion-specific effects on the physico-chemical properties of interfaces. Topics of interest include, but are not limited to, the following:

  • Specific adsorption of ions at solid/liquid, liquid/liquid, and liquid/air interfaces;
  • Surface forces across electrolyte solutions of different compositions;
  • Particle aggregation processes in salt solutions;
  • Interaction of ions with macromolecules;
  • Interfacial behavior of ionic liquid constituents;
  • Ion specificity in biological systems;
  • Role of electrolytes in environmental processes;
  • Influence of salt ions on the efficiency of separation techniques;
  • Theoretical approaches to investigate ion-specific effects.

Fundamental properties of colloidal systems in the presence of multivalent ions.

Dr. István Szilágyi
Guest Editor

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Ion-specific effect
  • Hofmeister series
  • Schulze–Hardy rule
  • aggregation, surface force
  • hydration of ions
  • adsorption
  • colloidal stability
  • ionic liquid
  • protein denaturation

Published Papers (7 papers)

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Research

Article
Surface Forces between Nanomagnetite and Silica in Aqueous Ca2+ Solutions Studied with AFM Colloidal Probe Method
Colloids Interfaces 2020, 4(3), 41; https://doi.org/10.3390/colloids4030041 - 10 Sep 2020
Viewed by 815
Abstract
Dispersion and aggregation of nanomagnetite (Fe3O4) and silica (SiO2) particles are of high importance in various applications, such as biomedicine, nanoelectronics, drug delivery, flotation, and pelletization of iron ore. In directly probing nanomagnetite–silica interaction, atomic force microscopy [...] Read more.
Dispersion and aggregation of nanomagnetite (Fe3O4) and silica (SiO2) particles are of high importance in various applications, such as biomedicine, nanoelectronics, drug delivery, flotation, and pelletization of iron ore. In directly probing nanomagnetite–silica interaction, atomic force microscopy (AFM) using the colloidal probe technique has proven to be a suitable tool. In this work, the interaction between nanomagnetite and silica particles was measured with AFM in aqueous Ca2+ solution at different pH levels. This study showed that the qualitative changes of the interaction forces with pH and Ca2+ concentrations were consistent with the results from zeta-potential measurements. The repulsion between nanomagnetite and silica was observed at alkaline pH and 1 mM Ca2+ concentration, but no repulsive forces were observed at 3 mM Ca2+ concentration. The interaction forces on approach were due to van der Waals and electrical double-layer forces. The good fitting of experimental data to the DLVO model and simulations supported this conclusion. However, contributions from non-DLVO forces should also be considered. It was shown that an increase of Ca2+ concentration from 1 to 3.3 mM led to a less pronounced decrease of adhesion force with increasing pH. A comparison of measured and calculated adhesion forces with a few contact mechanics models demonstrated an important impact of nanomagnetite layer nanoroughness. Full article
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Article
Micelle Encapsulation of Ferromagnetic Nanoparticles of Iron [email protected] Oxide in Chitosan as Possible Nanomedicine Agent
Colloids Interfaces 2020, 4(2), 22; https://doi.org/10.3390/colloids4020022 - 22 May 2020
Viewed by 1181
Abstract
In this work, the synthesis and characterization of core/shell nanoparticles of iron [email protected] oxide (Fe3C/γ-Fe2O3) encapsulated into micelles of sodium dodecylsulfate and oleic acid and stabilized with chitosan was developed. The materials were sonosynthesized at low intensities [...] Read more.
In this work, the synthesis and characterization of core/shell nanoparticles of iron [email protected] oxide (Fe3C/γ-Fe2O3) encapsulated into micelles of sodium dodecylsulfate and oleic acid and stabilized with chitosan was developed. The materials were sonosynthesized at low intensities using standard ultrasonic baths with iron pentacarbonyl (Fe(CO)5) and oleic acid as iron source and hydrophobic stabilizer, respectively; obtaining nanoparticles with a hydrodynamic diameter of 19.71 nm and polydispersive index (PDI) of 0.13. The iron [email protected] oxide nanoparticles (ICIONPs) in oleic acid were used as the organic phase during the self-assemble of nanoemulsion with sodium dodecylsulfate in water to obtain the metastable micelles. The final step involved the stabilization of the micelles using low molecular weight chitosan solution at 2% in acetic acid by ultrasonication bath. The nanosystem showed a hydrodynamic diameter of 185.30 nm, a PDI of 0.15 with a superficial charge ζ of 36.70 mV. Due to the magnetic, physical and chemical properties previously measured of the ICIONPs, it is believed that this type of nanoparticles can be used as a possible nanomedicine agent. Full article
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Article
A Simple Method to Determine Critical Coagulation Concentration from Electrophoretic Mobility
Colloids Interfaces 2020, 4(2), 20; https://doi.org/10.3390/colloids4020020 - 01 May 2020
Cited by 6 | Viewed by 1379
Abstract
Critical coagulation concentration (CCC) is a key parameter of particle dispersions, since it provides the threshold limit of electrolyte concentrations, above which the dispersions are destabilized due to rapid particle aggregation. A computational method is proposed to predict CCC values using solely electrophoretic [...] Read more.
Critical coagulation concentration (CCC) is a key parameter of particle dispersions, since it provides the threshold limit of electrolyte concentrations, above which the dispersions are destabilized due to rapid particle aggregation. A computational method is proposed to predict CCC values using solely electrophoretic mobility data without the need to measure aggregation rates of the particles. The model relies on the DLVO theory; contributions from repulsive double-layer forces and attractive van der Waals forces are included. Comparison between the calculated and previously reported experimental CCC data for the same particles shows that the method performs well in the presence of mono and multivalent electrolytes provided DLVO interparticle forces are dominant. The method is validated for particles of various compositions, shapes, and sizes. Full article
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Article
Role of the Counterions in the Surface Tension of Aqueous Surfactant Solutions. A Computer Simulation Study of Alkali Dodecyl Sulfate Systems
Colloids Interfaces 2020, 4(2), 15; https://doi.org/10.3390/colloids4020015 - 21 Apr 2020
Cited by 3 | Viewed by 819
Abstract
We have investigated the surface tension contributions of the counterions, surfactant headgroups and tails, and water molecules in aqueous alkali dodecyl sulfate (DS) solutions close to the saturated surface concentration by analyzing the lateral pressure profile contribution of these components using molecular dynamics [...] Read more.
We have investigated the surface tension contributions of the counterions, surfactant headgroups and tails, and water molecules in aqueous alkali dodecyl sulfate (DS) solutions close to the saturated surface concentration by analyzing the lateral pressure profile contribution of these components using molecular dynamics simulations. For this purpose, we have used the combination of two popular force fields, namely KBFF for the counterions and GROMOS96 for the surfactant, which are both parameterized for the SPC/E water model. Except for the system containing Na+ counterions, the surface tension of the surfactant solutions has turned out to be larger rather than smaller than that of neat water, showing a severe shortcoming of the combination of the two force fields. We have traced back this failure of the potential model combination to the unphysically strong attraction of the KBFF counterions, except for Na+, to the anionic head of the surfactants. Despite this failure of the model, we have observed a clear relation between the soft/hard character (in the sense of the Hofmeister series) and the surface tension contribution of the counterions, which, given the above limitations of the model, can only be regarded as an indicative result. We emphasize that the obtained results, although in a twisted way, clearly stress the crucial role the counterions of ionic surfactants play in determining the surface tension of the aqueous surfactant solutions. Full article
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Article
Salt Effects on Formation and Stability of Colloidal Gas Aphrons Produced by Anionic and Zwitterionic Surfactants in Xanthan Gum Solution
Colloids Interfaces 2020, 4(1), 9; https://doi.org/10.3390/colloids4010009 - 13 Feb 2020
Cited by 3 | Viewed by 978
Abstract
This work is devoted to the influence of NaCl salt concentration on the formation and stability of colloidal gas aphrons (CGA) produced by the anionic surfactant sodium dodecyl sulfate (SDS) and zwitterionic surfactant coco amido propyl betaine (CAPB) in the presence of xanthan [...] Read more.
This work is devoted to the influence of NaCl salt concentration on the formation and stability of colloidal gas aphrons (CGA) produced by the anionic surfactant sodium dodecyl sulfate (SDS) and zwitterionic surfactant coco amido propyl betaine (CAPB) in the presence of xanthan gum (XG) as a stabilizer. Dynamic surface tension measurements as well as volume and half-life time of the produced foams are considered for stability analysis. A sharp decrease of the half-life time and volume of the CGAs at NaCl concentrations larger than 20,000 ppm was observed, which was attributed to the precipitation of SDS in the solution. The mentioned SDS precipitation altered the dynamic surface tension behavior, dilational surface elasticity, and turbidity of the solution. The main reason for the precipitation of SDS is the increased Krafft point caused by the addition of salt. However, for the zwitterionic surfactant CAPB, the effects of added NaCl on the interfacial properties required for CGAs production was negligible due to the simultaneous effects on the cationic and anionic head groups in the CAPB leading to negligible changes in the net repulsion forces. Yet, an overall reduction in the half-life time of CGAs with increasing salt concentration, even when we have no precipitation, was observed for both surfactants, which could be explained by the reduction in the ability of XG to increase the viscosity with increasing salt concentration. Full article
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Article
Mechanisms of Surface Charge Modification of Carbonates in Aqueous Electrolyte Solutions
Colloids Interfaces 2019, 3(4), 62; https://doi.org/10.3390/colloids3040062 - 31 Oct 2019
Cited by 13 | Viewed by 1836
Abstract
The influence of different types of salts (NaCl, CaCl 2 , MgCl 2 , NaHCO 3 , and Na 2 SO 4 ) on the surface characteristics of unconditioned calcite and dolomite particles, and conditioned with stearic acid, was investigated. This study used zeta potential measurements to gain fundamental understanding of physico-chemical mechanisms involved in surface charge modification of carbonate minerals in the presence of diluted salt solutions. By increasing the salt concentration of divalent cationic salt solution (CaCl 2 and MgCl 2 ), the zeta potential of calcite particles was altered, resulting in charge reversal from negative to positive, while dolomite particles maintained positive zeta potential. This is due to the adsorption of potential-determining cations (Ca 2 + and Mg 2 + ), and consequent changes in the structure of the diffuse layer, predominantly driven by coulombic interactions. On the other hand, chemical adsorption of potential-determining anions (HCO 3 and SO 4 2 ) maintained the negative zeta potential of carbonate surfaces and increased its magnitude up to 10 mM, before decreasing at higher salt concentrations. Physisorption of stearic acid molecules on the calcite and dolomite surfaces changed the zeta potential to more negative values in all solutions. It is argued that divalent cations (Ca 2 + and Mg 2 + ) would result in positive and neutral complexes with stearic acid molecules, which may result in strongly bound stearic acid films, whereas ions resulting in negative mineral surface charges (SO 4 2 and HCO 3 ) will cause stearic acid films to be loosely bound to the carbonate mineral surfaces. The suggested mechanism for surface charge modification of carbonates, in the presence of different ions, is changes in both distribution of ions in the diffuse layer and its structure as a result of ion adsorption to the crystal lattice by having a positive contribution to the disjoining pressures when changing electrolyte concentration. This work extends the current knowledge base for dynamic water injection design by determining the effect of salt concentration on surface electrostatics. Full article
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Article
Fabrication of Mesoporous NaZrP Cation-Exchanger for U(VI) Ions Separation from Uranyl Leach Liquors
Colloids Interfaces 2019, 3(4), 61; https://doi.org/10.3390/colloids3040061 - 08 Oct 2019
Cited by 3 | Viewed by 967
Abstract
As the demand for uranium production-based energy worldwide has been increasing in the last decades to maintain nuclear growth for electricity production, there are great efforts towards developing an easy and inexpensive method for uranium extraction and separation from its ores. For this [...] Read more.
As the demand for uranium production-based energy worldwide has been increasing in the last decades to maintain nuclear growth for electricity production, there are great efforts towards developing an easy and inexpensive method for uranium extraction and separation from its ores. For this purpose, mesoporous inorganic cation exchangers provide an efficient separation technology that can help streamline production and lower overall cost. This study describes the development of nano-structured mesoporous sodium zirconium phosphate (NaZrP-CEX) for separation and extraction of uranyl ions from real samples. The fabricated NaZrP-CEX was well characterized by various techniques such as X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), Scanning Electron Microscope (SEM), N2 adsorption/desorption, Dynamic light scattering (DLS) and zeta potential). The kinetics/thermodynamic behaviors of uranyl ion adsorption into NaZrP-CEX from an aqueous solution were minutely studied. The kinetic studies showed that the pseudo-second order model gave a better description for the uptake process. The negative value of ΔG indicate high feasibility and spontaneity of adsorption. Finally, mesoporous NaZrP-CEX can be regenerated using both of HNO3 (0.05 M) or HCl (1 M) up to seven cycles of operation. Full article
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