Dielectric analysis of multi-layer structure of nanofiltration membrane in electrolyte solutions: Ion penetrability, selectivity, and influence of pH

2012 ◽  
Vol 386 (1) ◽  
pp. 16-27 ◽  
Author(s):  
Kongshuang Zhao ◽  
Jingjin Jia
Keyword(s):  
Layer Structure ◽  
Electrolyte Solutions ◽  
Nanofiltration Membrane ◽  
Dielectric Analysis ◽  
Influence Of Ph

The effects of electrolyte concentration, ion species and pH on the zeta potential and electrokinetic charge density of montmorillonite

Clay Minerals ◽  
2006 ◽  
Vol 41 (4) ◽  
pp. 853-861 ◽  
Author(s):  
E. E. Saka ◽  
C. Güler
Keyword(s):  
Zeta Potential ◽  
Charge Density ◽  
Negative Charge ◽  
Electrolyte Concentration ◽  
Great Influence ◽  
Electrolyte Solutions ◽  
Ionic Species ◽  
Positive Sign ◽  
Ion Species ◽  
Influence Of Ph

AbstractIn this study, the influence of pH, electrolyte concentration and type of ionic species (such as LiCl, NaCl, KCl, RbCl, CsCl, CaCl2, AlCl3) on the electrokinetic properties (zeta potential and electrokinetic charge density) of montmorillonite has been quantified. The zeta potential of montmorillonite particles did not change significantly with change in pH. The valencies of the ions have proven to have a great influence on the electrokinetic behaviour of the suspension. There is a gradual decrease in the zeta potential (from —24 mV to —12 mV) with increase in monovalent electrolyte concentration (from 10-4 M to 10-1 M). At any monovalent electrolyte concentration, the magnitude of the zeta potential increased with the electrolytes in the order Li+ > Na+ > K+ > Rb+ > Cs+. The zeta potential of the montmorillonite minerals in CaCl2 solutions illustrated the same behaviour as the monovalent cations. Less negative values were obtained for the CaCl2 electrolyte (∼–10 mV) due to the greater valence of the ions. A sign reversal was observed at an AlCl3 concentration of 5 x 10-4 M, and, at greater concentrations, zeta potential values had a positive sign (∼20 mV).The electrokinetic charge density of montmorillonite showed similar trends of variation in mono and divalent electrolyte solutions. Up to concentrations of ∼10-3 M, it remained practically constant at ∼0.5 x 10-3Cm-2, while for greater electrolyte concentrations the negative charge produced more negative values (–16 x 10-3Cm-2). The electrokinetic charge density of montmorillonite particles was constant at low AlCl3 concentrations, but at certain concentrations it increased rapidly and changed sign to positive.

scholarly journals Ion-specific Adsorption on Bare Gold (Au) Nanoparticles in aqueous Solution: Double-Layer Structure and Surface Potentials

2020 ◽  
Author(s):  
Zhujie Li ◽  
Victor G. Ruiz ◽  
Matej Kanduč ◽  
Joachim Dzubiella
Keyword(s):  
Au Nanoparticles ◽  
Layer Structure ◽  
Electrolyte Solutions ◽  
Electrostatic Potentials ◽  
Surface Charges ◽  
Effective Surface ◽  
Surface Potentials ◽  
Adsorption Structure ◽  
Highly Oscillatory ◽  
Bare Gold

We study the solvation and electrostatic properties of bare gold (Au) nanoparticles (NPs) of 1-2 nm in size in aqueous electrolyte solutions of sodium salts of various anions with large physicochemical diversity (Cl<sup>-</sup>, BF<sub>4</sub><sup>-</sup>, PF<sub>6</sub><sup>-</sup>, Nip<sup>-</sup>(nitrophenolate), 3- and 4-valent hexacyanoferrate (HCF)) using nonpolarizable, classical molecular dynamics computer simulations. We find a substantial facet selectivity in the adsorption structure and spatial distribution of the ions at the Au-NPs: while sodium and some of the anions (e.g., Cl<sup>-</sup>, HCF<sup>3-</sup>) adsorb more at the `edgy' (100) and (110) facets of the NPs, where the water hydration structure is more disordered, other ions (e.g., BF<sub>4</sub><sup>-</sup>, PF<sub>6</sub><sup>-</sup>, Nip<sup>-</sup>) prefer to adsorb strongly on the extended and rather flat (111) facets. In particular, Nip<sup>-</sup>, which features an aromatic ring in its chemical structure, adsorbs strongly and perturbs the first water monolayer structure on the NP (111) facets substantially. Moreover, we calculate adsorptions, radially-resolved electrostatic potentials, as well as the far-field <i>effective</i> electrostatic surface charges and potentials by mapping the long-range decay of the calculated electrostatic potential distribution onto the standard Debye-Hückel form. We show how the extrapolation of these values to other ionic strengths can be performed by an analytical Adsorption-Grahame relation between effective surface charge and potential. We find for all salts negative effective surface potentials in the range from -10 mV for NaCl down to about -80 mV for NaNip, consistent with typical experimental ranges for the zeta-potential. We discuss how these values depend on the surface definition and compare them to the explicitly calculated electrostatic potentials near the NP surface, which are highly oscillatory in the ± 0.5 V range. <br>

scholarly journals Ion-specific Adsorption on Bare Gold (Au) Nanoparticles in aqueous Solution: Double-Layer Structure and Surface Potentials

2020 ◽  
Author(s):  
Zhujie Li ◽  
Victor G. Ruiz ◽  
Matej Kanduč ◽  
Joachim Dzubiella
Keyword(s):  
Au Nanoparticles ◽  
Layer Structure ◽  
Electrolyte Solutions ◽  
Electrostatic Potentials ◽  
Surface Charges ◽  
Effective Surface ◽  
Surface Potentials ◽  
Adsorption Structure ◽  
Highly Oscillatory ◽  
Bare Gold

We study the solvation and electrostatic properties of bare gold (Au) nanoparticles (NPs) of 1-2 nm in size in aqueous electrolyte solutions of sodium salts of various anions with large physicochemical diversity (Cl<sup>-</sup>, BF<sub>4</sub><sup>-</sup>, PF<sub>6</sub><sup>-</sup>, Nip<sup>-</sup>(nitrophenolate), 3- and 4-valent hexacyanoferrate (HCF)) using nonpolarizable, classical molecular dynamics computer simulations. We find a substantial facet selectivity in the adsorption structure and spatial distribution of the ions at the Au-NPs: while sodium and some of the anions (e.g., Cl<sup>-</sup>, HCF<sup>3-</sup>) adsorb more at the `edgy' (100) and (110) facets of the NPs, where the water hydration structure is more disordered, other ions (e.g., BF<sub>4</sub><sup>-</sup>, PF<sub>6</sub><sup>-</sup>, Nip<sup>-</sup>) prefer to adsorb strongly on the extended and rather flat (111) facets. In particular, Nip<sup>-</sup>, which features an aromatic ring in its chemical structure, adsorbs strongly and perturbs the first water monolayer structure on the NP (111) facets substantially. Moreover, we calculate adsorptions, radially-resolved electrostatic potentials, as well as the far-field <i>effective</i> electrostatic surface charges and potentials by mapping the long-range decay of the calculated electrostatic potential distribution onto the standard Debye-Hückel form. We show how the extrapolation of these values to other ionic strengths can be performed by an analytical Adsorption-Grahame relation between effective surface charge and potential. We find for all salts negative effective surface potentials in the range from -10 mV for NaCl down to about -80 mV for NaNip, consistent with typical experimental ranges for the zeta-potential. We discuss how these values depend on the surface definition and compare them to the explicitly calculated electrostatic potentials near the NP surface, which are highly oscillatory in the ± 0.5 V range. <br>

A cellulose-based nanofiltration membrane with a stable three-layer structure for the treatment of drinking water

Cellulose ◽  
2020 ◽  
Vol 27 (14) ◽  
pp. 8237-8253 ◽  
Author(s):  
Dong Wang ◽  
Hongmei Yuan ◽  
Yutong Chen ◽  
Yonghao Ni ◽  
Liulian Huang ◽  
...  
Keyword(s):  
Drinking Water ◽  
Layer Structure ◽  
Nanofiltration Membrane

scholarly journals A novel positively charged composite nanofiltration membrane based on polyethyleneimine with a tunable active layer structure developed via interfacial polymerization

RSC Advances ◽  
2019 ◽  
Vol 9 (19) ◽  
pp. 10796-10806 ◽  
Author(s):  
Zhibin Jiang ◽  
Jing Miao ◽  
Yuantao He ◽  
Kai Tu ◽  
Shunquan Chen ◽  
...  
Keyword(s):  
Aqueous Phase ◽  
Active Layer ◽  
Organic Phase ◽  
Interfacial Polymerization ◽  
Layer Structure ◽  
Nanofiltration Membrane ◽  
Positively Charged

The tunable active layer structure was developed via interfacial polymerization, using polyethyleneimine as the monomer of the aqueous phase, and a mixture of isophthaloyl dichloride and tri-mesoyl chloride as the monomer of the organic phase.

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