Effect Of Counterion Type Research Articles

Stability of dodecyl sulfate emulsified asphalt: The overlook effect of dissociated counterions

As an environmentally friendly technology, emulsified asphalt can conserve resources and reduce hazardous fuming during paving, which is pivotal for promoting sustainable road engineering. However, asphalt emulsions with poor stability resulted in performance degradation especially after long-term storage or long-distance transport. The dissociation of anionic asphalt emulsions generates counterions that can potentially induce the emulsifier agglomeration at the asphalt-water interface, subsequently resulting in emulsion destabilization. In this study, two dodecyl sulfate emulsifiers (i.e., sodium lauryl sulphate (SDS) with Na+ counterion, and potassium lauryl sulfate (PDS) with K+ counterion) were employed in the production of asphalt emulsions. The effect of counterion type and concentration on the stability of dodecyl sulfate emulsified asphalt were investigated using storage stability, particle size distribution, and differential scanning calorimetry (DSC) tests. Molecular simulation was used to elucidate the mechanism of how the counterions affected the stability of dodecyl sulfate emulsified asphalt. Due to the fact that K+ counterion has a smaller electrostatic potential energy and a weaker electrostatic interaction with the O atoms in water molecules, PDS emulsified asphalt displayed superior homogeneity, storage stability, and heat stability. The emulsifier molecules adsorbed at the asphalt-water interface diffused into the water phase due to electrostatic attraction when the counterion doping exceeded the crucial value (SDS: 5 wt%, PDS: 4 wt%). Subsequently, the stable monolayer film at the interface dissolved, lowering the stability of the emulsified asphalt. It was challenging for SDS to compress the bilayer created by the headgroup since a limited number of Na+ counterions were accumulated near the headgroup. This hindered SDS from forming a monolayer at the asphalt-water interface, potentially explaining its inferior interfacial stability. Overall, our findings highlight the critical role of counterions in determining the stability of dodecyl sulfate emulsified asphalt, with K+ counterion in PDS emulsified asphalt showing superior stability.

Effects of counterion type on selective arsenic removal process combining standard anion exchange resin with electrocoagulation for polluted groundwater

This study achieved the highly selective removal of trace arsenic (As) from groundwater (110 μg L−1 As) by the standard anion exchange resin (AER) column process during long-term exhaustion–regeneration cyclic operation by optimizing the sulfate equivalent fraction (0.97 or 0.875) in sulfate-chloride or sulfate-bicarbonate binary brine (chloride or bicarbonate as counterion). No significant (<5%) or low (maximum: 25%) sulfate removal from the feedwater were stably observed during the 20 or 21 exhaustion–regeneration cycles without brine treatment or replacement, when <10 μg L−1 As was consistently observed in the product water. Furthermore, this study demonstrated the selective As removal from As-rich sulfate-chloride or sulfate-bicarbonate spent brine by aluminum (Al)- or iron (Fe)-based chemical coagulation or electrocoagulation process. Fe-based electrocoagulation (9-cm interelectrode distance, 0.50 mA cm−2, 15 min) and sulfate-chloride binary brine are finally recommended after metal dosage, sludge production and residual metal concentration among them were compared. No electrocoagulation took place in the sulfate-bicarbonate spent brine even at a current density of 3 mA cm−2 because of high bicarbonate concentration that formed passivation film on the anode surface. Finally, a combined process including a standard AER column and spent brine electrocoagulation was developed to achieve the stability and high As-selectivity of 114 exhaustion–regeneration cycles.

Effects of Counterion Type on Standard Anion Exchange Resin-Based Selective Arsenic Removal Process for Polluted Groundwater

Effects of Counterion Type on Standard Anion Exchange Resin-Based Selective Arsenic Removal Process for Polluted Groundwater

Mesophase characteristics of cellulose nanocrystal films prepared from electrolyte suspensions

Cellulose nanocrystals (CNCs) exhibit a cholesteric mesophase above a critical concentration in aqueous suspensions. Above this concentration, CNCs self-organize into left-handed helicoidal structures that can be preserved in dried, stratified films. In this systematic study, we have prepared optically-active CNC films cast from different electrolyte suspensions and investigated, via circular dichroism and other techniques, the effects of counterion type (six mono/divalent salts, including those responsible for promoting “salting-out” and “salting-in” in the Hofmeister series) and ionic strength on mesomorphic behavior and cholesteric arrangement. The presence of electrolytes influences CNC colloidal stability by compressing the electric double layer and altering interactions among neighboring CNCs and water, thereby affecting the extent to which the CNCs form a mesophase. Interestingly, mesomorphic behavior and CNC alignment appear to be sensitive to cationic radius and charge valence, in which case the optical properties of CNC films can be adjusted for targeted sustainable applications. Such heuristic rules can be valuable for predicting the stability and characteristics of CNC microstructure in designer coatings and thin films prepared by introducing suitable cations prior to film formation.

Blends of a Perfluorosulfonate Ionomer with Poly(vinylidene fluoride): Effect of Counterion Type on Phase Separation and Crystal Morphology

The type of counterion present in the Nafion component of a blend with poly(vinylidene fluoride) (PVDF) is shown to affect phase separation and the crystalline polymorphism of the PVDF component. Nafion neutralized with an alkali metal counterion, Na+, results in blends displaying large-scale phase separation upon heating to temperatures above the melting point of PVDF. In contrast, when the Nafion counterion is changed to a larger tetrabutylammonium counterion (TBA+), the melt is homogeneous, and with the exception of the PVDF crystallites, large-scale phase separation is not observed after the blend is cooled to room temperature. For the blends containing Na+-form Nafion, the crystalline morphology of the PVDF component develops in predominately the α crystal form, similar to pure PVDF crystallized from the melt. However, for blends containing TBA+-form Nafion, the PVDF component crystallizes with a higher content of the β- and/or γ-crystal forms. This effect of counterion type on the phase separation b...

Dynamic mechanical properties of lightly sulfonated polystryrene ionomers

AbstractThe effects of counterion type and addition of plasticizers on the dynamic mechanical properties of sulfonated atactic polystyrene (SaPS) containing 2.1 mole percent ionic groups have been investigated. For SaPS neutralized with alkali metal counterions at temperatures below 180°C, the matrix Tg and elastic modulus were not significantly affected by counterion type. However, above 180°C, the breadth of the rubbery plateau significantly decreased with increasing counterion size. Neutralization of SaPS with alkyl ammonium counterions decreased both the matrix Tg and the breadth of the rubbery plateau with increasing counterion size. By incorporating an ionic plasticizer in Na+ neutralized SaPS, dynamic mechanical properties were observed to be intermediate of systems neutralized with the alkali metal and alkyl ammonium counterions.

Effect of counterion type on charge transport at redox polymer-modified electrodes

The effect of counterion type on the ac impedance and linear sweep voltammetry response of a film consisting of Os(bpy) 2 (bpy indicates 2,2'-bipyridal) coordinatively bound in PVP (poly(4-vinylpyridine)) was investigated. Four acids were used at 0.1 M in the aqueous bathing electrolytes: hydrochloric, perchloric, trifluoroacetic, and toluenesulfonic. Analysis of the mobile ion concentrations in the film showed that protons were rejected from the film via Donnan exclusion, mating anions and hopping electrons the only two charge carriers. Ac impedance spectra revealed that, even with the largest counterion studied, ion transport was much faster than electron hopping

Dependence of the maximum speed of wetting maximum speed of wetting on the interactions in the three-phase contact zone

The contact-line motion upon creation of Y—Langmuir—Blodgett multilayers was studied under conditions of liquid-film entrainment. Arachidic acid and octadecylamine were used to model respectively negatively and positively charged liquid/gas and liquid/solid interfaces. The existence of a maximum speed of the three-phase contact line in these systems was proved (as earlier for glycerol—water mixtures and hydrophobic substrates). The effects of counter-ion type and concentration and pH on V max were also studied. The results are discussed on the basis of the electrical characteristics and hydration of the interfaces interacting in the three-phase contact zone.

Practical Aspects off Reverse Phase Ion Pair Chromatography

Practical aspects of reverse phase ion pair chromatography are discussed and illustrated with various examples. The effects of counterion type, size, and concentration are illustrated on diverse solutes such as linear alkylbenzene sulfonates, catecholamines, and dyestuffs. A recommended approach to performing an RP-IPC separation is given.