Hydroxide and hydronium ion adsorption — A survey

Zimmermann, Ralf; Freudenberg, Uwe; Schweiss, Ruediger; Küttner, David; Werner, Carsten

doi:10.1016/j.cocis.2010.01.002

Cited by 220 publications

(195 citation statements)

References 64 publications

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“…Hydrophobic surfaces immersed in neutral pH water solutions of low salt concentrations typically acquire negative surface charge densities of about 10 -2 C m -2 (see Table II), as determined by streaming current experiments. 73,74 022119 Thus, dissociation of only a small fraction of the adsorbed water molecules would be sufficient to explain the observed maximal net charges densities, and it may also be sufficient for the roughly ten times higher charge densities observed here. Furthermore, it must be considered that water adsorption is increased at the swab contact site during rubbing due to capillary condensation, especially for hydrophilic polymer combinations, and will be even further enhanced, in a positive feed-back, due to electric field-adsorption of water once the swab apex has been charged, for both hydrophilic and hydrophobic polymers.…”

Section: B Water As a Source Of Triboelectric Chargementioning

confidence: 79%

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Squeezing out hydrated protons: low-frictional-energy triboelectric insulator charging on a microscopic scale

Knorr¹

2011

AIP Advances

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Though triboelectric charging of insulators is common, neither its mechanism nor the nature of the charge is well known. Most research has focused on the integral amount of charge transferred between two materials upon contact, establishing, e.g., a triboelectric series. Here, the charge distribution of tracks on insulating polymer films rubbed by polymer-covered pointed swabs is investigated in high resolution by Kelvin probe force microscopy. Pronounced bipolar charging was observed for all nine rubbing combinations of three different polymers, with absolute surface potentials of up to several volts distributed in streaks along the rubbing direction and varying in polarity on μm-length scales perpendicular to the rubbing direction. Charge densities increased considerably for rubbing in higher relative humidity, for higher rubbing loads, and for more hydrophilic polymers. The ends of rubbed tracks had positively charged rims. Surface potential decay with time was strongly accelerated in increased humidity, particularly for polymers with high water permeability. Based on these observations, a mechanism is proposed of triboelectrification by extrusions of prevalently hydrated protons, stemming from adsorbed and dissociated water, along pressure gradients on the surface by the mechanical action of the swab. The validity of this mechanism is supported by explanations given recently in the literature for positive streaming currents of water at polymer surfaces and by reports of negative charging of insulators tapped by accelerated water droplets and of potential built up between the front and the back of a rubbing piece, observations already made in the 19th century. For more brittle polymers, strongly negatively charged microscopic abrasive particles were frequently observed on the rubbed tracks. The negative charge of those particles is presumably due in part to triboemission of electrons by polymer chain scission, forming radicals and negatively charged ions

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Section: B Water As a Source Of Triboelectric Chargementioning

confidence: 79%

“…This charge-separation process has been explained by a stronger adsorption of hydroxide ions than positive water ions to the channel walls. 74,90 The water ions stay in close proximity to each other in still water, but are separated in strong currents.…”

Section: E Analogies To the Proposed Triboelectric And Electrokinetimentioning

confidence: 99%

Squeezing out hydrated protons: low-frictional-energy triboelectric insulator charging on a microscopic scale

Knorr¹

2011

AIP Advances

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“…The uncharged species possess an IEP of around 3 and are slightly negatively charged (´32 mV at pH 7). This is due to the fact that even inert and uncharged surfaces have a small zeta potential resulting from adsorption of hydroxide ions from the self-ionization of water [50,51].…”

Section: Characteristics Of Ps Beads With Different Surface Chargementioning

confidence: 99%

“…The pristine PVDF membrane shows a trend that is typical for uncharged polymeric materials without further modifications. Due to the adsorption of hydroxide ions originating from the self-ionization of water the membrane surface appears to be negatively charged reaching its isoelectric point at a pH of 3.0 [50,51] and has a zeta potential of´40 mV at pH 7.…”

Section: Characteristics Of Modified Pvdf Membranesmentioning

confidence: 99%

Tailoring Membrane Surface Charges: A Novel Study on Electrostatic Interactions during Membrane Fouling

et al. 2015

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Abstract:In this work we aim to show that the overall surface potential is a key factor to understand and predict anti-fouling characteristics of a polymer membrane. Therefore, polyvinylidene fluoride membranes were modified by electron beam-induced grafting reactions forming neutral, acidic, alkaline or zwitterionic structures on the membrane surface. The differently charged membranes were investigated regarding their surface properties using diverse analytical methods: zeta potential, static and dynamic water contact angle, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Porosimetry measurements proved that there is no pore blocking due to the modifications. Monodisperse suspensions of differently charged polystyrene beads were synthesized by a radical emulsion polymerization reaction and were used as a model fouling reagent, preventing comparability problems known from current literature. To simulate membrane fouling, different bead suspensions were filtered through the membranes. The fouling characteristics were investigated regarding permeation flux decline and concentration of model fouling reagent in filtrate as well as by SEM. By considering electrostatic interactions equal to hydrophobic interactions we developed a novel fouling test system, which enables the prediction of a membrane's fouling tendency. Electrostatic forces are dominating, especially when charged fouling reagents are present, and can help to explain fouling characteristics that cannot be explained considering the surface wettability.

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“…In particular, the binding strength of the ion hydration shell has direct consequences for their interfacial behavior; small hard ions that form a strong hydration shell, such as alkali cations or fluoride, are depleted from the interface, whereas large polarizable ions, for example heavier halides and hydronium, may show propensity for the interface. 2,5,[18][19][20][21] The possibility to characterize the liquid-liquid interface on a microstructural level and the detailed dynamics information readily available have raised significant interest on molecular dynamics simulations of ions and their interactions at immiscible water -organic solvent interfaces since 1990s, 4,[22][23][24][25][26][27][28][29][30][31][32][33] but only recently molecular simulations have reached the system sizes and timescales sufficient to describe interfacial coarsening and transport through the interface in atomistic detail. 32,34 The approaches taken are dominantly classical, point-like partial charge models although the need for polarizable, or quantum mechanical models, has been argued.…”

Section: Introductionmentioning

confidence: 99%

Ion Transport through a Water–Organic Solvent Liquid–Liquid Interface: A Simulation Study

2014

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Ion interactions and partitioning at the water-organic solvent interface and the solvation characteristics have been characterized by molecular dynamics simulations.More precisely, we study sodium cation transport through water-cyclohexane, water-1, 2-dichloroethane, and water-pentanol interfaces providing a systematic characterization of the ion interfacial behavior including barriers against entering the apolar phase, as well as, characterization of the interfaces in the presence of the ions. We find a sodium depletion zone at the apolar interface and persistent hydration of the cation when entering the apolar phase. The barrier against the cation entering the apolar phase and ion hydration depend strongly on specific characteristics of the organic solvent. The strength of both barrier and hydration shell binding (persistence of the cation hydration) go with the apolarity and the surface tension at the interface, that is, both decrease in order cyclohexane-water > 1, 2-dichloroethane-water > pentanol-water. However, the size of the hydration shell measured in water molecules bound by the cation entering the less polar phase behaves oppositely with the cation carrying most water to the pentanol phase, and a much smaller in size, but very tightly bound water shell to cyclohexane. We discuss the implications of the observations for ion transport through the interface of immiscible, or poorly miscible liquids, and for materials of confined ion transport such as ion conduction membranes or biological ion channel activity.

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Hydroxide and hydronium ion adsorption — A survey

Cited by 220 publications

References 64 publications

Squeezing out hydrated protons: low-frictional-energy triboelectric insulator charging on a microscopic scale

Squeezing out hydrated protons: low-frictional-energy triboelectric insulator charging on a microscopic scale

Tailoring Membrane Surface Charges: A Novel Study on Electrostatic Interactions during Membrane Fouling

Ion Transport through a Water–Organic Solvent Liquid–Liquid Interface: A Simulation Study

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