Effect of different concentrations of surfactant on the wettability of coal by molecular dynamics simulation

Anionic surfactant sodium dodecyl benzene sulfonate(SDBS) at varying concentrations was selected to investigate the influence on the wettability of Zhaozhuang Coal by molecular dynamics simulation. Six groups of water/surfactant/coal systems with different concentrations were constructed. The influence of surfactant with different concentrations on the wettability of coal was concluded by analyzing various properties from the energetic behaviors to the dynamic characteristics. The results show that the interfacial tension decreases sharply and then rises slowly with the increase of SDBS surfactant concentration,obtaining that surfactants can obviously reduce the interfacial tension. The surfactant molecules could be detected at the water/coal interface through analyzing the system's relative concentration distribution. In addition, the difference in the wettability of surfactants on coal surfaces is caused by the spatial distribution differences of alkyl chains and the benzene ring of the surfactant molecules. And the negative interaction energy between SDBS and the coal surface indicates that adsorption process is spontaneous.Furthermore, it is of great practical significance for improving the dust reduction effect and reducing the disaster of coal dust by exploring the effects of surfactant molecules on the wettability of coal.     

Effects of [Bmim][Cl] ionic liquid with different concentrations on the functional groups and wettability of coal

In view of high dust concentration in coal mining and difficulty of traditional water injection in coal wetting, the effects of [Bmim][Cl] (1-butyl-3-methylimidazole chloride) ionic liquid with different concentrations on wetting performance and functional groups of coals have been studied. Optical droplet morphology analysis system and FTIR (Fourier transform infrared spectrometer) were used. The results showed that coal samples treated with [Bmim][Cl] ionic liquid had a significant change in the content of aliphatic groups. In the coal samples treated with 0% concentration [Bmim][Cl], the content of CH₂ groups was 77.86%, CH₃ groups was 14.07%. When [Bmim][Cl] concentration was 4%, the content of CH₂ groups decreased to 24.55%, CH₃ groups increased to 61.25%. Besides, the contact angle is the minimal of a 41.1° at 4% ionic liquid concentration. The relationship between contact angles and contents of functional groups were analyzed. Results showed that the content of CH₃ groups and CH₂ groups had the greatest effect on the contact angle and 4% [Bmim][Cl] ionic liquid treatment can effectively reduce the contact angle and improve the coal wettability. It is of great significance to increase coal wettability and reduce dust generation by changing the contents of functional groups.     

Study of contact angle, wettability and water vapor permeability in carboxymethylcellulose (CMC) based film with murta leaves (Ugni molinae Turcz) extract

Edible films have been extensively studied with the aim to find an adequate formulation that allows improving food quality and safety. Both wettability and water-barrier properties are two important parameters that must be considered for an adequate design of edible coatings. The aim of this work was to measure the contact-angle of film solution based on carboxymethylcellulose (CMC) with murta leaf (Ugni molinae Turcz) extract to estimate the wettability on apple and quince skins and measure the water vapor permeability (WVP) of films. The results show that murta leaves extract did not affect the contact angle and wettability measured on the fruits surface. However, differences were obtained between apple and quince skin which can be explained because the dispersive component of surface tension of quince skin was lower than apple skin. The WVP was not affected by murta leaves extract incorporation. This allows concluding that the film properties assayed were not modified by the incorporation of murta leaves extract ecotype 14-4.     

Wettability of carbon surfaces by pure molten alkali chlorides and their penetration into a porous graphite substrate

The wettability of graphite and glassy carbon surfaces by pure molten alkali chlorides (NaCl, KCl, RbCl, CsCl) was measured by the sessile drop method. The contact angle was found to decrease with increase of the cation radius of the chloride. Using our measured and available literature data, a new, semi-empirical model is established to estimate the adhesion energy between the 20 alkali halide molten salts and graphite (or glassy carbon). The adhesion energy is found to increase with square of the radius of the cation, and the inverse of the radius of the anion of the salt. The minimum possible value for the surface energy of graphite (and glassy carbon) was found as 150 ± 30 mJ/m². The critical contact angle of spontaneous penetration (infiltration) of the molten chlorides into a porous graphite substrate was found experimentally below 90°, in the interval between 31° and 58°. This is explained by the inner structure of the porous graphite.     

Wettability improving of 2024 aluminium alloy by oxygen cold plasma treatment

The need to contrast the severe use conditions developing in the aeronautical field requires surface protection of 2024 aluminium alloy structures by a paint coating. Therefore the aluminium alloy, to be suitable for painting, has to be subjected to complex and critical processes involving a cleaning by acid solvent, a chromate plating, a primer and a protective paint application. Oxygen cold plasma treatment represents an efficient, not-polluting and economic alternative to clean and activate aluminium alloy surfaces. It allows simplification of the anticorrosive protection process of aluminium alloy surfaces and, therefore, reduction of their manufacturing costs. The aim of this work has been to improve the wettability and its ageing time of an aluminium alloy surface treated with oxygen cold plasma. A set of process variables has been identified and used to carry out some experimental tests on the basis of design of experiment techniques.     

Studies of surface functional modification of nanosized α-alumina

Surface functional modification of nanosized α-alumina is an effective way to improve its dispersion in polymer and to enhance interfacial agglutinate force between particles and polymer. In this paper, diphenylmathane-4,4'-diisocyanate(MDI) was used as a surface grafting agent to react with the hydroxyl group on the surface of nanosized α-alumina. The surface properties of the grafted α-alumina were studied by FT-IR spectra X-ray photoelectron spectroscopy(XPS), surface tensiometer and transmission electron microscope (TEM). It was found that the reaction between the isocyanate group and the hydroxyl group on the surface of α-alumina nanoparticles was attribute to additional reaction of the double bond between C and N in the isocyanate group. The surface of MDI grafted α-alumina nanoparticles showed an extremely hydrophobic property and good dispersibility in ethanol. The most important influence was that there was a quantity of isocyanate groups with an active chemical property on the surface of the grafted particles, which could readily react with compounds containing -OH, -NH₂ or -COOH groups.     

Surface wettability and spectroscopic studies on miscibility and ion adsorption of binary biomimetic self-assembled monolayers on gold surfaces

Binary self-assembled monolayers (SAMs) have been much studied due to their high applicable potential as a model of biomimetic surfaces. However, the research about miscibility of binary SAMs has not much been investigated yet. In this work, we focused on analyzing the binary SAMs composed of mercaptohexadecanoic acid (MHA)-hexadecanthiol (HDT) on gold surfaces with Cassie equation, Israelachvili equation, and FTIR spectroscopy to confirm that the binary SAMs are well mixed. As a result, MHA-HDT binary SAMs are considered miscible because the result obtained from FTIR spectra is in good agreement with that calculated by Israelachvili equation for the case that two different molecules are well mixed on the surface. Also, the adsorption of cadmium ions on binary SAMs was confirmed by the appearance of carboxylate stretching bands. This article is dedicated to Professor Chang Kyun Choi for celebrating his retirement from the School of Chemical and Biological Engineering, Seoul National University.     

Kinetic characterization of p-tert-butylcalix[4,8,12]arene functionalized gold electrode by electrochemical impedance spectroscopy

Kinetic characterizations of impedimetric sensors having as transducers gold electrodes and as recognizing elements p-tert-butylcalix[4,8,12]arene were accomplished. Calixarene membranes were first studied using contact angle measurements. These revealed that all membranes exhibited hydrophobic and rough behaviours. Besides, based on the Van Oss model, surface energy components were determined and the main difference for the basic energy component was related to the calixarene conformation where hydroxyl groups were pointing towards gold surface.Electrochemical impedance spectroscopy results were modeled by appropriate equivalent circuits for the aim of elucidating electrical properties of calixarene functionalized gold electrodes. As results, a fast ionic transfer took place for p-tert-butylcalix[4] based impedimetric sensor, and a slow ionic transfer occurred for both p-tert-butylcalix[8,12] based impedimetric sensors. These behaviours were well accommodated with potentiometric outcomes that were previously encountered.     

Changes in the wettability of polymer electrolyte fuel cells components during cationic contamination and mitigation

Foreign cations are shown to cause mass transport losses, in particular due to wettability changes in the micro-porous layers (MPL) and the carbon paper substrate, and have a major impact on the durability and the performance of polymer electrolyte fuel cells. We studied the effects of cationic impurities on fuel cell system performance, especially on the water management by employing in-situ and ex-situ contamination methods. Changes in the wettability of the carbon paper surface following the in-situ contamination injection were quantified using the Wilhelmy plate method. The CaSO₄ precipitation on the macro-pores of the carbon paper substrate after the contamination injection causes a higher wettability leading to increased flooding of the carbon paper substrate and consequent mass transport losses. An ex-situ cleaning with an acid solution is shown to be very effective in removing the salt deposits of the carbon paper substrate. During the mitigation, the highly hydrophobic MPL acts as a barrier to the transport of the recovery solution into the membrane-electrode assembly (MEA), therefore isopropanol (IPA) was added to both the contaminant solution and the recovery solution to increase the wettability of the MPL. Wetting force measurements confirm that the added IPA can alter the wettability of the MPL and can render it fully hydrophilic, enabling the transport of the recovery solution into the MEA.     

Effect of roughness on wettability and floatability: Based on wetting film drainage between bubbles and solid surfacesOA

Wetting film thinning measurement was introduced to clarify the wettability and floatability of solid surfaces with varying roughness. The wettability was quantified using the contact angle measurement combined with the dynamic force microbalance test between solid surfaces and water droplets, while the floatability was investigated by the bubble-solid surface dynamic attachment observation and the induction time measurement. The results show that the water contact angles reduce(14.53°, 12.74°, ...