A new model for cation exchange equilibrium considering the electrostatic field of charged particles

Liu, Xin Min; Li, Hang; Tian, Rui; Hou, Jie

doi:10.1007/s11368-012-0517-x

Cited by 24 publications

(17 citation statements)

References 36 publications

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“…In the dos Santo and Yan Levin study 1 , the surface charge density was merely 0.04–0.06 C/m 2 . Moreover, only under relatively high electrolyte concentrations would the ionic size (including hydration diameter) effect become significant 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 . Therefore, the difference between K E and K C should have decreased with electrolyte concentration, in contrast to Figure 1 .…”

Section: Resultsmentioning

confidence: 99%

Strong non-classical induction forces in ion-surface interactions: General origin of Hofmeister effects

Liu

et al. 2014

Sci Rep

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Hofmeister effects continue to defy all-encompassing theories, and their origin is still a matter of debate. We observed strong Hofmeister effects in Ca 21 /Na 1 exchange on a permanently charged surface over a wide range of ionic strengths. They could not be attributed to dispersion forces, classical induction forces, ionic size, or hydration effects. We demonstrated that another stronger force was active in the ion-surface interactions, and which would create Hofmeister effects in general. The strength of this force was up to 10 4 times that of the classical induction force, and could be comparable to the Coulomb force. Coulomb, dispersion and hydration effects appeared to be interwined to affect the force. The presence of the observed strong non-classical induction force implied that energies of non-valence electrons of ions/atoms at the interface might be heavily underestimated in current theories, and possibly just those underestimated energies of non-valence electrons determined Hofmeister effects. Hofmeister effects, also known as specific ion effects, were observed over 120 years ago. Even though they are ubiquitous in the physical, chemical and biological literature, their origin is still contested 1-7 and has been recently brought to the forefront of research [8][9][10][11][12][13][14][15][16][17][18][19] . New work in this area may break down barriers between physics and biology 9 . Ionic sizes, hydration, quantum fluctuations (or dispersion forces) 3,4,8 , and surface charges 1,2 are crucial in Hofmeister effects. Nano-scale surfaces and colloidal particles (e.g., DNA, proteins, cells, bacteria, metal oxides, and clay) are usually strongly charged in aqueous solution, and the sign of the charge or the charge number for biological macromolecules will be dependent on pH and ionic strength 20 . In classical theory, the surface charges can set up a strong electric field extending from the surface to several nanometers in solution. Typical surface charge densities and their corresponding electric field strengths include: (1) . For proteins, surface charge density measurements are primarily based on zeta potentials; therefore, they would be equal to the charge density at the shear plane, which is possibly much lower than the charge density at the surface [27][28][29] , especially when considering the strong surface hydration force [30][31][32] . At the shear plane, the charge density could reach 0.02-0.35 C/m 2 [33][34][35] , with an electric field of 10 7 -10 8 V/m. Therefore, it is reasonable to expect electric field strengths .10 8 V/m at protein surfaces in aqueous solutions. However, in those calculations, adsorbed counter-ions near the surface are treated as point charges. If their ionic size were taken into account, then the electric field near the surface would be much greater than 10 8 V/ m. This is because the finite size of counter ions could weaken their screening effect, as compared with point charges.Noah-Vanhoucke and Geissler found that, the persistence of electric field in the space near ...

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Section: Resultsmentioning

confidence: 99%

Strong non-classical induction forces in ion-surface interactions: General origin of Hofmeister effects

Liu

et al. 2014

Sci Rep

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“…At a low pH of 1.0, our preliminary experiments showed that before and after H + treatment, no significant change in the montmorillonite structure was observed. 43 Approximately 1 g of the H-saturated sample was weighed in a 150 ml triangular bottle, to which 0.03 mol L −1 KOH or 25 ml NaOH solution was added. The suspension sample was allowed to equilibrate for 48 hours with continuous shaking at 298 K in an incubator shaker, and then a standard 1 mol L −1 HCl solution was used to adjust the pH of the suspension (several drops).…”

Section: Methodsmentioning

confidence: 99%

A how-to approach for estimation of surface/Stern potentials considering ionic size and polarization

Liu

Ding

et al. 2015

Analyst

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Electrostatic potential in the electric double layer is an important parameter that significantly affects a large number of physical, chemical and biological properties and processes. In the present study, a new approach for the estimation of surface potential and Stern potential considering ionic volume and polarization was developed. Ionic strong polarization in the diffuse layer increases its effective charge and determines the Stern potential, while ionic volume in the Stern layer strongly decreases its effective charge and determines the surface potential. For example, the effective charge of K(+) is increased by 0.699 (from 1 to 1.699) resulting from polarization, while it is decreased by 1.359 (from 1.699 to 0.240) due to finite size. The determined surface potential is about 7 times as high as the Stern potential. The effects of volume and polarization on the surface/Stern potentials were quantified respectively, and the former was stronger than the latter. A new theory was verified by the experiments for aggregates stability. The present work also showed that only introduction of the strong polarization into the DLVO theory can describe the interactions of colloidal particles.

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“…Correspondingly, for a Z:Z‐type electrolyte, the Debye length changes to:

\frac{1}{κ} = \sqrt{\frac{ϵ R T}{8 π F^{2} γ Z^{2} a_{0}}},

where a 0 is the activity of ions in the bulk solution, taking into account the ionic interaction energy (Li et al , ; Liu et al , ), ϵ (C 2 J −1 m −1 ) is the permittivity, R (J mol −1 K −1 ) is the universal gas constant and T (K) is the absolute temperature.…”

Section: Theory For Calculating Surface Potential Of Soil Particles Tmentioning

confidence: 99%

“…where a 0 is the activity of ions in the bulk solution, taking into account the ionic interaction energy (Li et al, 2011;Liu et al, 2012), (C 2 J −1 m −1 ) is the permittivity, R (J mol −1 K −1 ) is the universal gas constant and T (K) is the absolute temperature. Equation (5) indicates that cationic NCP can strongly decrease the surface potential of soil particles, which strongly decreases the electrostatic repulsive force among soil particles.…”

Section: Theory For Calculating Surface Potential Of Soil Particles Tmentioning

confidence: 99%

Role of cationic polarization in humus‐increased soil aggregate stability

Huang

et al. 2016

European J Soil Science

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It is well known that humus markedly increases soil aggregate stability, but at the same time strongly decreases the flocculation of clay particles in suspension. These seemingly inconsistent observations suggest the need for a deeper understanding of the physical mechanisms that govern clay–humus interactions. In this research, soil samples from an Entisol were used to explore the role of cationic polarization in humus‐increased soil aggregate stability and sodium (Na+) and potassium (K+) ions were used to characterize weak and strong polarization, respectively. The results showed that strong cationic polarization has a critical role in increased soil aggregate stability in the presence of humus. We concluded that, without cationic polarization, the effects of humus alone on soil aggregate stability were weak in the presence of monovalent metal cations. When we compared the individual contributions of humus and strong cationic polarization, the latter proved much more important than humus in increasing soil aggregate stability. The strongest increase in soil aggregate stability occurred when strong cationic polarization was coupled with humus. The combined analysis of activation energy of soil flocculation in suspension and soil aggregate stability in the presence of humus indicated that humus increased the long‐range electrostatic repulsive force of soil particles, and increased the short‐range attractive force of soil particles. Consequently, humus decreased the flocculation of soil particles in suspension but increased soil aggregate stability; all effects were adjusted by the strength of cationic polarization. Highlights Elucidation of physical mechanisms of cation–surface interactions that determine clay–humus interactions. Cations at the particle surface of the clay–humus complex are strongly polarized. Cationic polarization has a critical role in humus‐increased soil aggregate stability. Without cationic polarization, the effect of humus alone on soil aggregate stability was weak.

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A new model for cation exchange equilibrium considering the electrostatic field of charged particles

Cited by 24 publications

References 36 publications

Strong non-classical induction forces in ion-surface interactions: General origin of Hofmeister effects

Strong non-classical induction forces in ion-surface interactions: General origin of Hofmeister effects

A how-to approach for estimation of surface/Stern potentials considering ionic size and polarization

Role of cationic polarization in humus‐increased soil aggregate stability

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