Journal of Molecular Liquids最新文献

This study explores the potential of hexagonal boron nitride (h-BN) nanoparticles suspended in Deep Eutectic Solvent (DES) as a thermal medium or coolant. The eutectic point of the DES, which comprises dibenzyl ether and diphenyl ether as HBA and HBD, respectively, is predicted using the COnductor-like Screening MOdel-Segment Activity Coefficient (COSMO-SAC) thermodynamic model. The Nuclear Magnetic Resonance (NMR) spectroscopy technique is used to evaluate the hydrogen interaction of the DES. The nanofluids are synthesized at five different concentrations of h-BN nanoparticles: 0.01–0.12 wt%. The uniform dispersion of the nanoparticles in the bulk media is investigated by zeta potential stability analysis. The basic physical–chemical properties, namely thermal stability and freezing point, of the DES are further measured. The experimental evaluation of nanofluids comprises studying the effective thermophysical characteristics. The results demonstrate that the average thermal conductivity increase for Nanoparticles-Enhanced DES (NEDES2) is 7.4%. The specific heat capacity (average) of NEDES5 nanofluid increased by 33%. For a small quantity of nanoparticle dispersion, the viscosity of nanofluids increases somewhat relative to the base fluid and is temperature-dependent. While the density decreases with the addition of nanoparticles. Precise predictions of thermophysical properties are essential for addressing and improving a wide range of heat and mass transfer problems, especially in the field of engineering and associated domains. This is especially important for complex fluids, including nanofluids, which have a crucial impact on advancing new technologies. The importance of thermal performance parameters in heat transfer research is apparent. However, there is a noticeable lack of dependable thermophysical properties for nanofluids that can be consistently used in various issues and sophisticated industrial systems. A machine learning technique is used to forecast the thermophysical characteristics of nanofluids. For several models, the deviation between nanofluid’s predicted and experimental thermophysical characteristics is less than 6%. Apart from thermal conductivity, all other nanofluid parameters vary linearly with temperature, with R² values above 0.99 and RMSE less than 0.0332.

The existence state and effective removal of organics from Bayer liquor have troubled the alumina industry for six decades. This study delved into the aggregation behavior and micellization of organics in Bayer liquor. Tricalcium aluminate hexahydrate (3CaO·Al₂O₃·6H₂O, TCA) was then employed as a cost-effective adsorbent to remove organics by regulating the aggregation behavior of organics. Sodium dodecylsulfate (SDS), acting as a research object of organics, aggregated into inhomogeneous and large micelles (>3080.00 nm) with an extremely low critical micelle concentration (CMC) of 0.14 mmol·L⁻¹ in the sodium aluminate solution (C_Na2O = 2.42 mol·L⁻¹, α_K = 3.0, I ≥ 4.84 mol·L⁻¹) at 298 K. Decreasing temperature facilitated the formation of these large micelles and the micellar size reached 2.20 μm in length. The solvated Ca²⁺ (Ca(OH)⁺) of TCA, acting as counterions with a content exceeding 11.97 wt%, initially induced the formation of micelles and then enlarged their size. Furthermore, these large micelles exhibited a preferential aggregation at the active concave of TCA. As a result, the interaction among inhomogeneous micelles, solvated Ca²⁺ (Ca(OH)⁺), and special active concave collectively contributed to the maximum organic carbon adsorption capacity of 32.46 mg·g⁻¹ (equivalent to 64.92 mg·g⁻¹ of SDS) at 298 K. These results open up new perspectives for understanding the existence state of the anionic organics in sodium aluminate solutions, as well as a cost-effective and eco-friendly approach to removing organics from Bayer liquor.

To explore methods for enhancing the wetting performance of coal dust to mitigate its hazards, this study selected four different structures of non-ionic fluorocarbon solutions: perfluorinated propyl acrylate (PFPA), perfluorooctyl acrylate (PFTA), perfluorooctyl sulfonyl phenyloxy ethyl methylacrylate (PPM), and perfluoro propanoic acid (PFA). The dynamic wetting performance and mechanisms of these solutions on coal dust were measured and analyzed through kinetic calculations. The results indicate that all four fluorocarbon solutions achieve optimal wetting performance at a concentration of 0.3 %. Comprehensive analysis shows that their wetting ability follows the order PFPA > PFTA > PPM > PFA. Further analysis reveals that coal dust treated with PFPA shows an increase in structures such as COOH and CO. The relative concentration distribution indicates partial overlap between the fluorocarbon solution and water, with an overlap range of 8.2 Å. Additionally, the maximum diffusion coefficient is 0.577 Å/ps, and the system’s adsorption energy is the highest at −5757.25 kcal/mol.

High-rank coal dust with high degree of coalification has poor wettability, which in turn affects the dust suppression effect of wetting dust suppressants. This article presents the enhancement of the wettability of bituminous coal and anthracite by surface active ionic liquid [C₁₂MIm]Br and the synergistic wetting effect of [C₁₂MIm]Br with the conventional surfactants, DTAB, SDBS and AEO₉. The mixed solution of [C₁₂MIm]Br and AEO₉ had the best wetting and sinking effect on high-rank coal dust by surface tension test and sink test. The wettability change of high-rank coal dust modified by monomer and mixed solution indicated that the best wetting effect occurs when the coal dust modified by [C₁₂MIm]Br-SDBS in the mixed solution of [C₁₂MIm]Br-AEO_9(15CMC). The adsorption capacity of wetting agents on coal dust surface and the microstructures changes of modified coal dust were studied by UV–visible spectrophotometry and infrared spectroscopy. The results showed that the ether bond functional groups changed obviously and the aliphatic hydrocarbon functional groups increased relatively, revealing the microstructural difference for the enhanced wettability of high-rank coal dust caused by the synergistic wetting effect of [C₁₂MIm]Br and surfactant.

Active colloid particles have been used in many fields due to their good performance in enhancing mass transport or modifying interfacial energy. Previous studies have shown that both nanoparticles adsorbed at oil–water interface and those dispersed in bulk fluid could enhance oil recovery during the oil production process. It is challenge to directly compare these results and clarify the effect of nanoparticle’s location on oil detachment from rock surface because different kinds of nanofluids were used in those work. Herein, the oil mobilization performance by nanoparticles adsorbed at oil–water interface and dispersed in the bulk phase were investigated from the pore-scale to core-scale by using one material. Two fluorescent quantum nanodots with different affinities for oil and water phases were synthesized using the same materials but with different compositions and solvents. Their locations were observed under the laser confocal microscopy. The nanoparticles adsorbed at the oil–water interface not only presented a lower interface tension, but also demonstrated a notable capability to change the wettability from oil-wet to water-wet due to its strong tendency to rock surface. The particles-laden interface can also increase the stability and shear viscosity of formed emulsions. Furthermore, it featured a larger swept area of 6.6 % in microfluidic flooding and a higher displacement efficiency of 1.7 % in the core flooding experiments. All these findings indicate that the particle-adsorbed at the oil–water interface is more favorable for enhanced oil recovery.

The realization of industrial applications of plant-based lubricants depends on well-dispersed lubricant additives. Herein, microwave-assisted ball milling directly grafted L-phenylalanine (LP) onto graphene oxide. The reaction does not require a pretreatment step and avoids high temperatures and catalyst involvement. The prepared LP-functionalized graphene oxide (LP-GO) exhibited hydrophobicity with a water contact angle of up to 133° and could maintain stable dispersion in castor oil for more than 80 days. 0.2 wt% of LP-GO improved the thermal conductivity of castor oil by 11.1 % and contributed to the enhancement of tribological performance under three different conditions. In particular, wear and friction decreased by 7.31 % and 11.54 % under the medium speed medium load condition, respectively. The friction decreased by 25.27 % in the low-speed high-load condition, and the wear decreased by 18.65 % under the high-speed low-load condition. The characterization of the tribological interface revealed that the lubrication mechanism of LP-GO was attributed to its protective and repairing effects at the friction interface. The surface functionalization approach in this paper is rapid and green. It can be extended to other functionalizing agents and nanomaterials, facilitating further applications of vegetable oils in tribology.

Acidification modification has proven to be a successful approach for enhancing the permeability of low-permeability coal seams and increasing coalbed methane extraction. To explore the influence of acetic acid on the organic structure of coal, a combined approach of experimental research and quantum chemical calculation is employed to examine the reaction mechanism of coal organic structure in response to acetic acid. Fourier transform infrared spectroscopy reveals a reduction in the content of hydroxyl and C–O bonds in the treated samples, along with the appearance of an absorption peak of C=C bonds. This demonstrates that the main site of acetic acid acidification modification on coal molecules is the hydroxyl functional group. Therefore, glycerol can be used as a simplified model of coal molecules for further investigation. In addition, three typical functional groups (phenyl, hydroxyl, amino) are selected as the research objects. The electronic density topological properties, molecular surface electrostatic potential, Mayer bond orders and CM5 charge of coal molecules were calculated based on quantum chemical theory. This reveals the intrinsic strength of each chemical bond between single atoms in a molecule, thereby predicting potential reaction pathways between acetic acid and coal molecules. The micro-mechanism of acetic acid catalyzing/esterifying the organic structure of coal is studied using transition state methods. The computational results show that there are two main modes of reaction between acetic acid and coal molecules: (1) acetic acid catalyzes the dehydration reaction of coal molecules; (2) acetic acid reacts with coal molecules to form ester intermediates, followed by decomposition through various reactions. Among the 14 reaction pathways, acetic acid provides protons or groups to trigger the dehydration of coal molecules. Interestingly, it is found that the overall hydroxyl group participates in the reaction is easier than the individual hydrogen atom on the hydroxyl group, and the overall carboxyl group participates in the reaction is easier than the individual hydroxyl group. This indicates that the higher the overall atomic reactivity of acetic acid, the lower the reaction barrier. Compared with catalytic reactions, acetic acid tends to undergo esterification reactions with hydroxyl groups, with the phenyl ring functional group significantly affecting the reaction barrier. The introduction of various oxygen-containing functional groups like ketone, aldehyde, and ester in the reaction products will hinder the adsorption of non-polar methane, reduce the adsorption capacity of coal seams for gas, and play an essential role in promoting gas desorption. The research findings can provide theoretical guidance for the organic acidification modification of low-permeability coal seams to enhance gas permeability and coalbed methane extraction.

Glutamic acid is a non-essential amino acid, meaning that the body can synthesize it on its own, and it doesn’t necessarily need to be obtained from the diet. Using an ultrasonic interferometer, the ultrasonic velocity at 293.15 K and 298.15 K and at experimental pressure P = 101 kPa were determined in order to evaluate and comprehend the synergy between non-essential amino acid and saccharides (L-arabinose/D-xylose) in an aqueous system. There is a direct correlation between the weak and strong molecular interactions that occur between the solution’s constituents and the propagation of ultrasonic sound waves through the experimental solutions. Using the ultrasonic velocity data, isentropic compressibility $(K_s$) apparent molar isentropic compressibility ($K_{s,\varphi })$ and isothermal compressibility $(K_T$) were calculated. In addition to these characteristics, acoustic impedance (Z), internal pressure $({\pi }_i$), relative association $(R_A$), molar free volume $(V_f$), molar free length $(L_f$) and surface tension ($\gamma )$ were deduced and analysed to advocates potent ion- solvent interactions. In order to gain understanding of Glu-Glu and Glu- L-arabinose/D-xylose interactions in aqueous medium, these parameters were interpreted. Ion-solvent interactions are stronger than ion-ion interactions due to the greater and positive values of $K_s^0$. Strong contacts occur between the polar segments of L-arabinose/D-xylose and the zwitterionic groups of Glu, and these interactions become stronger as the concentration of L-arabinose/D-xylose increases, as indicated by positive values of $K_{s,\varphi ,tr}^0$. The water structure is reformed during the solvation and ion association processes of Glu. Furthermore, the spectroscopic investigation has been conducted using the FTIR technique in order to verify the results obtained from acoustic studies. Predominant ion-hydrophilic/hydrophobic interactions prevail in the studied system is validated by FTIR study. Absorption band widening indicates that intermolecular hydrogen bonding predominates over intramolecular hydrogen bonding.

This research paper presents experimental and theoretical findings concerning the blending of mineral oil and vegetable oils, both with and without antioxidants. The study analyses a variety of parameters for different blends of mineral and vegetable oils, including breakdown voltage, ageing resistance, dielectric constant, viscosity, dissipation factor, surface tension, flash point, and fire point. The study was further extended to investigate the effects of varying the amount of antioxidants added to mineral oil blends with different vegetable oils. The best transformer insulating solution is found by extensive analyses that include measurements of breakdown voltage, flash point, fire point, and surface tension. This blends’ properties with antioxidant are either better than pure mineral oil or comparable to mineral oil. Density functional theory (DFT) analyses the molecular structure and dipole moment of an antioxidant. Molecular dynamics simulation method (MD) analysis of the average water residual time – periods of an antioxidant will show the stability of H-bond interactions. The primary objective of this experiment is to unveil a novel liquid-insulating material that not only excels in dielectric performance but also aligns with environmentally friendly practices.

Chalcopyrite and molybdenite are the primary minerals from which copper and molybdenum are extracted. However, the separation of chalcopyrite and molybdenite is restricted because of their inherent floatability. This study explores the separation effects of the addition of a green depressant, pyrogallic acid (PA), on chalcopyrite and molybdenite. The feasibility of flotation separation was verified by flotations tests with chalcopyrite and molybdenite under weak acid conditions at pH 6. The zeta potential and total organic carbon (TOC) illustrated that PA could have strong chemical adsorption on the surface of chalcopyrite and weak adsorption on the surface of molybdenite. Fourier-transform infrared (FTIR) spectroscopy illustrated that PA had a strong redox reaction at the surface of chalcopyrite. X-ray photoelectron spectroscopy (XPS) results illustrated that the reaction occurred through the generation of Cu/Fe-OH complexes covered on the chalcopyrite surface to reduce the active adsorption sites, which led to a decrease in the collection capacity for chalcopyrite. Moreover, time-of-flight secondary ion mass spectrometry (ToF-SIMS) results showed that the Cu and Fe sites on the surface of chalcopyrite were oxidized by PA. The intensities of FeOH⁻ and CuOH⁻ were found to be enhanced in the fragmentation peaks. Accordingly, a new selective adsorption model of PA on chalcopyrite and molybdenite was proposed.