Nonpolar Oil Research Articles

Interface Mechanism of Promoting Low-Rank Coal Flotation by Characteristic Groups in Hydrophilic Moieties of Cationic-Anionic Surfactants.

Flotation is an interfacial process involving gas, liquid, and solid phases, where polar ionic promoters significantly influence both gas-liquid and solid-liquid interfaces during low-rank coal (LRC) flotation. This study examines how the structures of hydrophilic groups in cation-anion mixed promoters affect the interfacial flotation performance of LRC pulp using flotation tests, surface tension tests, wetting heat tests, and molecular dynamics simulations. Results indicate that cation-anion mixed promoters enhance the LRC floatability to varying degrees. When the cationic hydrophilic head contains a benzyl group and the anionic head contains an ethoxy group, both the floatability and selectivity improve. These mixed promoters exhibit superior surface activity compared to single ionic solutions, particularly with ethoxy-containing anions, which demonstrate an increased density and viscoelasticity at the gas-liquid interface. The combination of a benzyl cation and an ethoxy anion results in dense adsorption at the solid-liquid interface, maximizing wettability differences between organic matter and mineral surfaces. This is attributed to hydrogen bonds and π-π interactions between the promoter and the coal surface, enhancing adsorption selectivity. Hydrophobic chains shield polar sites on the LRC surface, promoting water molecule diffusion and providing sites for nonpolar oil molecule adsorption, thereby improving LRC flotation performance.

Enhancing Supercapacitor Performance with Microemulsion-Based Electrolytes

Supercapacitors (SCs) are energy storage devices between conventional capacitors and batteries, providing essential technology for rapid energy storage and discharge. Used in applications like laptops, automotive braking systems, and hybrid vehicles, SCs offer high power densities and long cycle lives, though their energy densities are typically moderate. Enhancing SC energy density requires using non-aqueous electrolytes to extend the voltage window and increasing the active surface area of the electrodes to boost capacitance. However, non-aqueous electrolytes often struggle with ion solubility, which is crucial for forming the electric double layer that enables rapid charging and discharging. Our studies into microemulsions as novel electrolytes show potential in decoupling conductivity from soluble oil, addressing ion solubility issues, and potentially unlocking further performance enhancements.Microemulsions are promising electrolytes for energy storage, forming thermodynamically stable, homogeneous solutions of polar and non-polar molecules. These solutions stabilize oil and water mixtures, allowing non-polar oil to adsorb to hydrophobic carbon electrodes while maintaining high conductivity from an aqueous salt solution. Importantly, microemulsion components are environmentally and biologically safe.This presentation explores the impact of surfactants and microemulsions on electric double-layer supercapacitor performance. We employ scanning electron microscopy to monitor the porous carbon layer on the grafoil substrate. Techniques like electrochemical impedance spectroscopy, cyclic voltammetry, and constant current charge and discharge provide comprehensive insights into SC performance. Our findings indicate that choosing surfactant, cosurfactant, and oil is crucial for maximizing SC performance.

Tailoring Dynamic Chains of Cross‐Linked PDMS to Hinder Oil Penetration

AbstractPolydimethylsiloxane (PDMS) is the most studied organosilicon polymer, finding broad applications in soft lithography of microfluidic devices, wearable electronics insulation, medical tubing, shielding coatings, and sealant elements. However, their cross‐linked forms swell severely in nonpolar oils due to the comparable solubility parameters. Here, an oil‐stable cross‐linked PDMS discovered by grafting flexible PDMS chains onto its polymeric networks is reported, which enables surface‐exposed chains with high dynamics. It is found that the synergetic effect of mobile nanopore filling and quasi‐liquid lubrication of PDMS brushes endows the cross‐linked matrix with a reduced oil absorption ratio of up to 91.7% without altering its surface composition. Moreover, stretching polymeric networks can be re‐arranged with an adequate grafting of PDMS chains, further enhancing the antipenetration performance. This discovery of the oil‐stable surface configuration of cross‐linked PDMS breaks the constraint of siloxane elastomers not being applicable in nonpolar soluble liquid, opening a new era of research in organosilicon chemistry.

Composition and polymerisation products influence on the viscosity of coal tar wash oil

Wash oil is a fraction obtained by the distillation of coal tar and is primarily used for the absorption of light oil from coke oven gas. During operation, the oil undergoes polymerization and loses some components, necessitating the removal of the used oil and its replacement with fresh wash oil. The rheological properties of the studied oils were determined using a Brookfield DV2T rotational controlled-shear rate rheometer. Gas chromatographic analysis, gas chromatography/mass spectrometry, and IR spectroscopy were employed to evaluate the oil’s characteristics. By adding individual components to the wash oil, it was found that these components could be categorized into three groups: viscosity enhancers, viscosity reducers, and non-polar oil substances with medium molecular weight that have no significant effect on viscosity. The addition of relatively polar components with greater molecular weight and a planar, rigid structure leads to an increase in viscosity. Conversely, the incorporation of naphthalene and its methyl homologues, which have lower molecular weights, reduces viscosity by disrupting intermolecular interactions; their lower heats of crystallization also inhibit the formation of structured order in the liquid, further contributing to the reduction in viscosity. The most substantial increase in oil viscosity was observed with the addition of indene-coumarone resins, attributed to their high molecular weight and polymer structure.

Solid/liquid hybrid lubrication behaviors of amorphous carbon film coupling with nonpolar and polar base oils

The amorphous carbon film (a-C) has aroused intensive interest in solid-oil hybrid lubrication design due to its low friction, high wear resistance, and good chemical inertness. However, the solid/liquid hybrid lubrication behaviors and mechanisms of a-C films when coupled with nonpolar and polar oils of similar viscosity are still insufficiently understood and ambiguous to date. In this study, we compared the lubrication properties of nonpolar paraffin oil and polar polyether oils with different molecular structures when combined with a-C film. The results demonstrated that the lubrication performance of polyether oils coupled with a-C film surpassed that of paraffin oil across various lubrication regimes. Notably, the stable superlubricity (friction coefficient<0.01) was achieved under mixed lubrication regime on the a-C film when coupled with polyethylene glycol (PEG) oil after a prolonged sliding duration. The tribo-induced formation of carbon quantum dots (CQDs) at the steel/a-C friction interface lubricated by PEG oils was firstly observed. The hydroxylation of the counter ball surface and the fabrication of CQDs might jointly contribute to the achievement of the robust superlubricity of the PEG oil/a-C film hybrid lubrication system.

Amphiphilic Nanogels as Versatile Stabilizers for Pickering Emulsions.

Pickering emulsions (PEs) are stabilized by particles at the water/oil interface and exhibit superior long-term stability compared to emulsions with molecular surfactants. Among colloidal stabilizers, nano/microgels facilitate emulsification and can introduce stimuli responsiveness. While increasing their hydrophobicity is connected to phase inversion from oil-in-water (O/W) to water-in-oil (W/O) emulsions, a predictive model to relate this phase inversion to the molecular structure of the nano/microgel network remains missing. Addressing this challenge, we developed a library of amphiphilic nanogels (ANGs) that enable adjusting their hydrophobicity while maintaining similar colloidal structures. This enabled us to systematically investigate the influence of network hydrophobicity on emulsion stabilization. We found that W/O emulsions are preferred with increasing ANG hydrophobicity, oil polarity, and oil/water ratio. For nonpolar oils, increasing emulsification temperature enabled the formation of W/O PEs that are metastable at room temperature. We connected this behavior to interfacial ANG adsorption kinetics and quantified ANG deformation and swelling in both phases via atomic force microscopy. Importantly, we developed a quantitative method to predict phase inversion by the difference in Flory-Huggins parameters between ANGs with water and oil (χwater - χoil). Overall, this study provides crucial structure-property relations to assist the design of nano/microgels for advanced PEs.

The influence mechanism of water-liquid CO2 treatment on the hydrophobicity of vitrinite and inertinite

Liquid CO2 has similar properties to non-polar hydrocarbon oils and can be used to achieve hydrophobic aggregation separation of coal macerals. To reveal the influence of the water-liquid CO2 treatment on the interfacial properties of vitrinite and inertinite, the effects of the water-liquid CO2 system on the interfacial properties of vitrinite and inertinite were investigated by SEM, BET, FTIR, and XPS. The results showed that the content of oxygen-containing functional groups on the coal macerals were reduced more significant than the hydrocarbons due to the physical adsorption and chemical extraction of liquid CO2, which led to an increase in the hydrophobicity of vitrinite and inertinite. The higher porosity and specific surface area of inertinite causing the decrease in the content of oxygen-containing functional groups in inertinite was greater than that in vitrinite. This study provides theoretical support for the separation of coal macerals using liquid CO2 hydrophobic agglomerates.

Preparation and Tribological Behavior of Silica Nano-Additives with Good Applicability for Both Polar and Non-Polar Base Oils

Preparation and Tribological Behavior of Silica Nano-Additives with Good Applicability for Both Polar and Non-Polar Base Oils

A case study of enhanced flotation of coal gasification fine slag by multiple compound collectors

ABSTRACT The flotation mechanism of multiple compound collectors called ZKC-I for coal gasification fine slag (CGFS) was revealed from the flotation kinetics, adsorption properties, bubble–particle interaction, and froth properties. The results were compared to dodecane, which represents the conventional nonpolar hydrocarbon oil collector. The flotation concentrates yield and rate constant of CGFS treated by ZKC-I were 2–3 times than those of CGFS treated by dodecane. Fourier transform infrared spectroscopy and wrap angle results showed that ZKC-I improved the hydrophobicity of residual carbon because of the synergistic adsorption of fatty acids, esters, and aromatic hydrocarbons in the ZKC-I on the heterogeneous surface of residual carbon particles, which enhanced the adhesion between residual carbon particles and bubble. Due to the strong carrying capacity of the bubble to residual carbon particles, the number of residual carbon particles in the froth treated by ZKC-I was more than that of the CGFS froth treated by dodecane. The high content of carbon particles in the froth resulted in great stability of the flotation froth, and the maximum height and half-life of the froth were higher than that of CGFS treated by dodecane. This study has practical and theoretical significance for the separation of coal-based solid waste.

Constructing multi-layer Ti3C2Tx/rGO heterojunctions: Synergistic effect and unique lubrication mechanism

Two-dimensional materials, such as Ti3C2Tx and graphene oxide (GO), are considered candidates for a new generation of lubricating materials due to their unique physical and chemical properties. However, the dispersion stability of Ti3C2Tx and GO in non-polar oils is insufficient, hindering their potential as lubricating additives. Herein, 1,12-Dodecanediamine (DDM) was used as a bridge to connect Ti3C2Tx and GO, and to reduce graphene oxide (rGO) for forming the stacked two-dimensional multilayer Ti3C2Tx/rGO heterostructures. The multilayer Ti3C2Tx/rGO heterostructure exhibits excellent dispersion stability in PAO 20, ensuring its continuous integration into the tribo-interfaces throughout the friction process. The addition of 0.06 wt% multilayer Ti3C2Tx/rGO to the base oil reduced the average friction coefficient and wear volume by 35.3% and 41.6%. The enhanced lubrication performance is mainly due to the unique multilayer heterostructure of Ti3C2Tx/rGO. During friction, the disintegration of Ti3C2Tx into small fragments effectively safeguards the structural integrity of rGO, thereby facilitating the formation of a robust and smooth multilayer lubrication film. Additionally, Ti3C2Tx is adhered to the wear surface in smaller sizes or evolved into the form of Ti oxides. The emergence of this new composite material is not only expected to solve the problem of insufficient performance of traditional lubricating materials under extreme conditions, but also laid the foundation for expanding the application of two-dimensional materials in the field of lubrication.

Nanostructured lubricant additives for titanium alloy: Lubrication by the solid-liquid interface with Coulomb repulsion

In this work, the advantage of Coulomb repulsion in the intermolecular forces experienced by molecules on the solid-liquid nanosized contact interface is taken, and the superior friction-reducing property of Cu3(PO4)2·3H2O (CuP) oil-based additives has been confirmed for titanium alloy. Three-dimensional (3D) CuP nanoflowers (CuP-Fs) with a strong capillary absorption effect are prepared to achieve the homogeneous mixing of solid CuP and lubricating oil. Lubrication by CuP-Fs additives for titanium alloy, friction coefficient (COF) can be reduced by 73.68%, and wear rate (WR) reduced by 99.69%. It is demonstrated that the extraordinary friction-reducing property is due to the repulsive solid-liquid interface with low viscous shear force originating from Coulomb repulsion between polar water molecules in CuP and non-polar oil molecules. However, any steric hindrance or connection between this repulsive solid-liquid interface will trigger the adhesion and increase the viscous shear force, for example, dispersant, hydrogen bondings, and shaky adsorbed water molecules. Besides, the lamellar thickness of CuP and the molecular size of lubricant both have a great influence on tribological properties. Here the lubrication mechanism based on interface Coulomb repulsion is proposed that may help broaden the scope of the exploration in low-friction nanomaterial design and new lubricant systems.

Robust macroscale superlubricity of multiple base oils achieved on soft epoxy resin coatings

Reducing the friction of base oils to a superlubricity state is highly expected at engineering scale. However, it still is a great challenge for the most of viscous base oils to achieve superlubricity on the conventional tribopairs up to now. Here we report the strategy of solid-oil composited lubrication constructed with an ultra-smooth epoxy resin (EP) coating and base oils for achieving superlubricity. Especially, the frictional results showed that the proposed strategy in this study could be suitable for multiple base oils, including nonpolar and polar base oils as lubricants. The friction coefficient of steel/EP tribopair lubricated by the base oils containing hydroxyl group can be as low as 0.001. Meanwhile, the composited lubrication system did not undergo an obvious running-in stage to achieve the superlubricity state regardless of the type of base oils. The surface hydroxylation of the steel counter ball sliding against EP coating was observed by time-of-flight secondary ion mass spectrometer, even when lubricated by nonpolar base oils without hydroxyl group. This could be a critical factor for the base oils to achieve superlubricity. This finding provides a new and facile approach to realize robust superlubrication for different base oils at engineering scale.

Salinity and pH effects on water-oil-calcite interfaces by using molecular dynamics.

Smart water injection is a technology that allows changing the wettability of the oil rock by injecting water at different salinities, in a cheap and environmentally friendly way compared to other traditional methods. In this study, the individual effect of some typical salts on the wettability of the (104) surface of calcite toward non-polar and polar crude oil models was explored by molecular dynamics as a function of the salinity and pH. The results obtained show that the electrical double layer plays a principal role in the detachment of crude oil models. The divalent ion salts, i.e., CaCl2, CaSO4, MgCl2, and MgSO4, do not form the electrical double layer on calcite, but salts of NaCl and Na2SO4 form it. Moreover, the surface affinity of calcite to the non-polar crude oil is not affected by the salinity. However, the affinity of the calcite surface toward polar crude is affected by salinity and pH conditions. This research provides new insights into the action mechanisms that could help optimize its uses in enhanced oil recovery.

Transforming water-soluble carbon dots with high particle size regularity as the high-performance oil-based lubricant additives by one-step surface modification

Developing high-performance carbon dot (CD)-based lubricant additives towards non-polar base oils is always challenging because it is an arduous task to gain hydrophobic CDs with high quality. In this work, with the aid of the chemical reaction between hydroxyl groups and lauroyl chloride molecules, the water-soluble CDs-OH derived from the solvothermal method with particularly high particle size regularity were transformed as the oil-soluble CDs-LA by the one-step surface modification process. As expected, the CDs-LA capped by abundant long alkyl chain groups exhibited excellent long-term dispersion stability in non-polar base oil of polyalphaolefin (PAO4) and hence could be served as the additives of PAO4 directly. Under the same test conditions, the tribological performance of CDs-LA was obviously superior to the hydrophobic CDs obtained by the pyrolysis method, implying that the high particle size regularity was beneficial for making full use of the lubrication functions of CDs. Loading 1.7 wt% of CDs-LA made the friction and wear of PAO4 reduced by 32.2 % and 76.4 %, respectively. When the duration prolonged from 20 min to 200 min, the friction reduction of base oil triggered by CDs-LA further enlarged to 46.9 %. The friction-reducing and anti-wear performance of CDs-LA under high loads was also satisfactory. The worn surface analysis results demonstrated that the robust and homogenous boundary lubrication films composed of FexOy and CDs have generated on the rubbing surfaces lubricated by CDs-LA/PAO4 dispersion, well accounting for the outstanding friction reduction and wear resistance functions of CDs-LA.

Oil-soluble deep eutectic solvent functionalized graphene oxide towards synergistic lubrication in non-polar PAO 20 lubricant

Although deep eutectic solvents (DESs) have shown excellent surface modification and lubrication properties, there have been seldom reports concerning the effect of those characters on the tribological behavior of nanoparticles as non-polar oil additives. Here, we grafted tetrabutylammonium chloride and octanol-based oil-soluble DES onto the base plane or interlayer of GO through a long aliphatic chain, chloride ion and C-N covalent functionalization, forming functionalized GO (DES/GO). The DES/GO could well disperse in a nonpolar polyalphaolefin base oil (PAO 20) to construct DES/GO hybrid PAO 20. Moreover, the friction and wear of DES/GO hybrid PAO 20 oil decreased by 35% and 41% compared with those of pure PAO 20 oil. The splendid interfacial lubrication depends on the formation of uniform, dense, and strong graphene-like tribofilm to shield the tribo-interfaces against wear. And the grafted DES on GO further participates in the tribochemical reaction to form the FexOy, FeCl2 or FeCl3 and tetraalkylammonium salt tribochemical film. The self-lubricating performance of GO and tribochemical reaction of DES together achieve a synergistic lubrication effect.

Reducing the negative impact of accidents associated with the release of dangerous substances to environment.

The article is concerned with an evaluation of the current state of emergency readiness of industrial companies in the event of dangerous substance leakage and with a presentation of textile sorbents used for the purposes of capturing an escaped substance. A part of the article is concerned with the experimental designation of sorption capacity of hydrophobic, chemical, and universal sorption mats for chosen polar (water and alcohol) and non-polar (oil and gasoline) liquids. Experiments were realized according to Standard Test Method for Sorbent Performance of Adsorbents for use on Crude Oil and Related Spills, American Society for Testing and Materials (ASTM F726-17), type I. and Test methods for non-woven fabrics, European Union International Organization for Standardization (EN ISO 9073-6:2004). The aim of the article is an experimental designation of sorption capacity of textile sorption mats using two different methods, a comparison of the acquired results and a comparison of the acquired data with the data given by the manufacturer. Textile sorbents, which can, owing to their sorption ability, allow the elimination or mitigation of a negative impact of a possible accident in the company connected with an escape of a liquid dangerous substance were tested and compared with the established values. Based on the obtained results it is possible to state that sorption capacities of the chemical and universal mat for the substrate water are equal and consistent with the data given by the manufacturer. Textile sorption mats also have a comparable sorption capacity. The sorption capacity on the substrate gasoline is the same in all textile sorbents. The adsorption capacity per unit mass all type's sorbents was similar for non-polar liquids (gasoline was values from 6.41 to 6.57 and oil was values from 9.54 to 10.24). The acquired results confirmed the universality of textile sorption mats for gasoline. Sorption capacities of the chemical and universal mat for the substrate water are equal and match the data given by the manufacturer. Textile sorption mats have a maximum sorption output up to 60 s, afterwards the sorption capacity values remain unchanged.

Study on the microscopic mechanism of adsorption and diffusion of hydrocarbon oil drops on coal surface using molecular dynamics simulations

AbstractFlotation of fine coal particles usually uses oil collectors, but the micromechanisms need to be more defined due to the complex structure and abundant functional groups on the surface of coal bodies [Correction added after first online publication on 16 October 2023: “refined” was changed to “defined” in the first sentence of the article abstract.]. The adsorption spreading behavior and interfacial properties of nonpolar oil drops on flat low‐order coal (LOC) and high‐order coal (HOC) surfaces were investigated in depth using molecular dynamics (MD) simulations, while the effects of different functional groups on LOC surfaces were also considered. The results showed that the contact angle, contact area and interaction energy of oil drops adsorbed on the LOC and HOC surfaces at simulated equilibrium in aqueous environment were 77.68°, 621.49 Å2, −140.94 kcal/mol; 53.98°, 962.14 Å2, and −195.13 kcal/mol, respectively. The smaller the equilibrium contact angle between the oil drops and the surface, the larger the contact area and the larger the absolute value of the interaction energy, the better the spreading effect of the oil drops and the easier the surface is to flotation. Compared with the HOC surface, the oil drops could not displace the water molecules on the LOC surface better and spread poorly on its surface, and the migration rate was higher. This was caused by the abundant functional groups on the surface of LOC. The type of functional group significantly affects the interaction of nonpolar oil drops with hydrophilic surfaces, with the order of adsorption strength being CH3 &gt; COCH3 &gt; OH &gt; COOH. The formation of a dense hydrated film of oil drops on the COOH surface was an important reason for the difficulty of flotation on the LOC surface. MD elucidated the mechanism of action of nonpolar oil collectors on LOC and HOC surfaces, which is a guide for efficient flotation on LOC surfaces.

Presence of bicontinuous microemulsion-type domains and dielectrically inert interfacial water layers in lamellar gel-stabilized oil-in-water emulsions

HypothesisLamellar gels are widely formulated in household and cosmetic products because of their eminent ability to improve long-term stability of thermodynamically unstable oil-in-water emulsions. However, despite long study, how and why membrane internal structure and membrane-membrane interactions are modified by the presence of polar and nonpolar oils remains elusive. ExperimentsUsing small- and wide-angle X-ray scattering, dielectric spectroscopy, and field-emission transmission electron microscope, we investigate intermembrane interactions and water-mediated microscopic interfacial properties in lamellar gels and lamellar gel-stabilized oil-in-water emulsions based on cetyltrimethylammonium chloride and 1-hexadecanol. FindingsReducing membrane surface charge density enhances undulation fluctuation disorder, resulting in a crossover of dominant interactions from electrostatic double-layer repulsion to Helfrich interaction. Oil-emulsification induces similar structural impacts to the reduced 1-hexadecanol ratio, confirming preferential dissolution of higher-alcohol in oil phases. An emerging Teubner-Stray scattering component upon emulsification of nonpolar oil evidences that oil droplets and lamellar gels are indirectly connected via bicontinuous microemulsion-type domains. Dielectric spectra reveal strikingly small water permittivity in the lamellar gel and emulsion samples, which is quantitatively explained by a cumulative effect of a dielectrically inert interfacial thin water layer (<1nm) and a highly polarizable bulk-like water layer. This phenomenon appears to be intrinsic to diverse lamellar stack architectures.

Superhydrophobic TiO2 nanotube arrays with switchable adhesion in both air and oil

Superhydrophobic surfaces with smart adhesion has aroused increased interest. However, all reported surfaces can only display switchable adhesion in air. Herein, we report a fluoroalkylsilane-modified TiO2 nanotube surface that has switchable adhesion in both air and oil as it is alternately Ultraviolet-irradiated and heated. The transition is not synchronous; a longer Ultraviolet-irradiation time is needed to obtain high adhesion in oil than in air, and the transition is more difficult in polar oil than in non-polar oil. The reversible transition attributes to the combined effect between the nanostructure and surface chemical variation, the out-of-step transition is attributed to different roles of the exposed naked TiO2, which offers water-adhesive force in air and oil-adhesive/water-repellent force in oil. This works reveals the effect of environmental media on surface-wetting/adhesion transition, which is helpful for design of novel adhesive surfaces to meet practical requirements.

Composition and technology effect on the structure and properties of frost-resistant elastomeric materials based on blends of polar and nonpolar rubbers

Elastomeric materials for sealing devices operated in the Far North, including the Republic of Sakha (Yakutia), must be resistant to working environments and have frost and wear resistance with acceptable physical and mechanical properties. Some of the listed properties are mutually exclusive and are not always achievable in materials based on individual rubber. Thus, one promising method for sealing elastomeric materials is the use of rubber mixtures. In this study, model blends based on nitrile-butadiene (BNKS-18), butadiene (SKD), and isoprene (SKI-3) rubbers were studied. Nitrile butadiene rubber was chosen as the component of the mixture responsible for resistance to working environments, and diene rubbers (SKD and SKI-3) were chosen as the components responsible for frost resistance. The addition of SKI-3 also suppressed the crystallization of SKD butadiene rubber. An increase in the BNKS-18 content enhanced the physical and mechanical properties and resistance to wear and non-polar oils. A decrease in lowtemperature properties and resistance to polar oils was also observed. Additionally, studies of the structure of the obtained materials by atomic force microscopy were carried out, which proved the uniformity of the distribution of particles of the dispersed phase, the size of which did not exceed 1-5 μm. The optimal ratio of butadiene-nitrile to diene rubbers was 70:30 phr. At this ratio, the obtained elastomeric materials meet the requirements of sealing materials for operation in cold climates.