Oil-water Interface Research Articles

Adsorption behavior and application properties of natural alcohol polyoxyethylene polyoxypropylene ether sulfate

In recent years, the Polyoxypropylene (PO) group has been introduced between the hydrophobic group and the polyoxyethylene (EO) group of traditional surfactants to enhance interfacial properties. However, literature on surfactants introducing PO chains between EO and hydrophilic groups remains scarce. In this study, three variants of natural alcohol polyoxyethylene polyoxypropylene ether sulfate (C1214E3PnS), each with different PO addition numbers, were synthesized from natural alcohol ether through sulfation and neutralization reactions. The adsorption behavior of C1214E3PnS with different PO addition numbers was investigated and compared to AES by measuring surface tension, dynamic surface tension, and contact angle. The results indicate that as the number of PO increases, both the critical micelle concentration and maximum adsorption capacity decrease. Additionally, pC20 and the number of PO groups introduced in the surfactant show a linear negative correlation, indicating a decline in surfactant efficiency. Due to an adsorption barrier, C1214E3PnS is governed by a mixed diffusion-kinetics adsorption mechanism. According to the application performance of C1214E3PnS, as the number of PO increases, wettability and foam stability have decline, while emulsifying performance is significantly enhanced. In conclusion, surfactants such as C1214E3PnS do not favor adsorption at the solid–liquid interface, but enhance the properties at the oil–water interface.

Viscosity Reduction Behavior of Carbon Nanotube Viscosity Reducers with Different Molecular Structures at the Oil–Water Interface: Experimental Study and Molecular Dynamics Simulation

Effectively enhancing oil recovery can be achieved by reducing the viscosity of crude oil. Therefore, this paper investigated the viscosity reduction behavior of carbon nanotube viscosity reducers with different molecular structures at the oil–water interface, aiming to guide the synthesis of efficient viscosity reducers based on molecular structure. This study selected carbon nanotubes with different functional groups (NH2-CNT, OH-CNT, and COOH-CNT) for research, and carbon nanotubes with varying carbon chain lengths were synthesized. These were then combined with Tween 80 to form a nanofluid. Scanning electron microscopy analysis revealed an increased dispersibility of carbon nanotubes after introducing carbon chains. Contact angle experiments demonstrated that -COOH exhibited the best hydrophilic effect. The experiments of zeta potential, conductivity, viscosity reduction, and interfacial tension showed that, under the same carbon chain length, the conductivity and viscosity reduction rate sequence for different functional groups was -NH2 < -OH < -COOH. The dispersing and stabilizing ability and interfacial tension reduction sequence for different functional groups was -COOH < -OH < -NH2. With increasing carbon chain length, conductivity and interfacial tension decreased, and the viscosity reduction rate and the dispersing and stabilizing ability increased. Molecular dynamics simulations revealed that, under the same carbon chain length, the diffusion coefficient sequence for different functional groups was -NH2 < -OH < -COOH. The diffusion coefficient gradually decreased as the carbon chain length increased, resulting in better adsorption at the oil–water interface. This study holds significant importance in guiding viscosity reduction in heavy oil to enhance oil recovery.

The Roles of Oil-Water Interfaces in Forming Ultrasmall CaSO4 Nanoparticles.

In natural and engineered environmental systems, calcium sulfate (CaSO4) nucleation commonly occurs at dynamic liquid-liquid interfaces. Although CaSO4 is one of the most common minerals in oil spills and oil-water separation, the mechanisms driving its nucleation at these liquid-liquid interfaces remain poorly understood. In this study, using in situ small-angle X-ray scattering (SAXS), we examined CaSO4 nucleation at oil-water interfaces and found that within 60 minutes of reaction, short rod-shaped nanoparticles (with a radius of gyration (Rg) of 17.2 ± 2.7 nm and a length of 38.2 ± 5.8 nm) had formed preferentially at the interfaces. Wide-angle X-ray scattering (WAXS) analysis identified these nanoparticles as gypsum (CaSO4·2H2O). In addition, spherial nanoparticles measuring 4.1 nm in diameter were observed at oil-water interfaces, where surface-enhanced Raman spectroscopy (SERS) revealed an elevated pH compared to the bulk solution. The negatively charged oil-water interfaces preferentially adsorb calcium ions, collectively promoting CaSO4 formation there. CaSO4 particle formation at the oil-water interface follows a nonclassical nucleation (N-CNT) pathway by forming ultrasmall amorphous spherical particles which then aggregate to form intermediate nanoparticles, subsequently growing into nanorod-shaped gypsum. These findings of this study provide insights into mineral scaling during membrane separation and can inform more efficient oil transport in energy recovery systems.

Laboratory study on the transformation of oil-water interface properties under direct current electric field

Interface tension is one of the important mechanisms that affect crude oil recovery and plays an important role in the development of tight oil reservoirs. Electrical-enhanced oil recovery can be used as a technology to reduce interfacial tension and improve crude oil recovery. In the previous research process of Electrical-enhanced oil recovery, the focus was more on the influence of electric field on wettability, and the understanding of the changes in interfacial tension under electric field action is not yet comprehensive. This article designs an orthogonal experiment to study the effect of electric field on oil-water properties. The degree of influence of three factors, namely sodium chloride solution concentration (C), direct current voltage (V), and voltage action time (t), on interfacial tension is studied. Gas chromatography, four component analysis, and Fourier transform infrared spectroscopy are combined to discuss the mechanism of the influence of changes in solution pH, crude oil components, and oil phase functional groups on interfacial tension. The results show that an external electric field can effectively reduce the interfacial tension between oil and water, and the maximum change in interfacial tension after the experiment can be reduced from 23.21 mN/m to 0.37 mN/m; Through range analysis, it can be concluded that the concentration of sodium chloride solution has the greatest impact on interfacial tension, followed by DC voltage and voltage action time. The optimal experimental conditions are 0.5 mol/L sodium chloride solution, 10 V DC voltage, and a voltage action time of 18 h, and the change in interfacial tension is related to the increase in pH value. The change in crude oil composition is also an important reason for the decrease in interfacial tension under external electric fields. Finally, Fourier transform infrared spectroscopy was used to determine that under the action of an electric field, the increase in pH of the sodium chloride solution resulted in the formation of carboxylate salts through chemical reactions between alkaline substances of solution and acidic substances of the oil, which were the key factors in reducing interfacial tension. This study helps to understand and explore the principles and mechanisms of Electrical-enhanced oil recovery in improving oil recovery, with the aim of contributing to the development and promotion of Electrical-enhanced oil recovery technology.

Long carbon chain-modified carbon nanoparticles for oil displacement in harsh-condition reservoirs

Carbon nanoparticles, as an emerging type of enhanced oil recovery agent, promising broad prospects in unconventional oil and gas development. However, limitations such as low interfacial activity due to the strong hydrophilicity of carbon nanoparticles and tendency to aggregate under high-temperature and high-salinity conditions restrict their further application. In this study, activity carbon dots (S-CDs) were prepared via a simple two-step hydrothermal reaction. A range of physicochemical techniques characterized S-CDs, revealing their small particle size (1.4 ± 0.01 nm) and narrow distribution, maintaining strong dispersion stability in mineralized water at 130 °C with a concentration of 16 × 104 mg/L. The AFM scanning results indicated that S-CDs possessed strong interfacial wetting control capability, the adhesion force between oil and rock cores (after S-CDs treatment) decreased by 25 times. Particle Image Velocimetry (PIV) confirmed that S-CD adsorbed at the oil-water interface could formed a solid film, which could rupture into smaller oil droplets for convenient backward migration. The results demonstrated that S-CDs improved the interfacial activity while maintaining the hydrophilicity of CDs. In core displacement experiments, 0.05 wt% S-CDs nanofluid reduced injection pressure by 32.4 % and increased recovery rates by 34.9 %. This work provides new insights for the development of high-temperature, high-salinity displacement agents in harsh-condition reservoirs.

Comparison of Methods Used to Investigate Coalescence in Emulsions.

We present a study of moderately stable dilute emulsions. These emulsions are models for water contaminated by traces of oil encountered in many water treatment situations. The purification of water and the elimination of oil rely on the emulsion stability. Despite actively being studied, the topic of emulsion stability is still far from being fully understood. In particular, it is still unclear whether experimental methods accessing different length scales lead to the same conclusions. In the study presented in this paper, we have used different methods to characterize the emulsions, such as centrifugation and simple bottle tests, as well as investigations of the collision of single macroscopic oil drops at an oil-water interface. We studied different emulsions containing added polymer or surfactant. In the case of added polymer, centrifugation and single drop experiments led to opposite trends in stability when the polymer concentration is varied. In the case of added surfactant, both centrifugation and single drop experiments show a maximum stability when the surfactant concentration is increased, whereas bottle tests show a monotonous increase in stability. We propose tentative interpretations of these unexpected observations. The apparent contradictions are due to the fact that different methods require different drop sizes or different drop concentrations. The puzzling decrease in emulsion stability at a higher surfactant concentration observed with some methods, however, remains unclear. This coalescence study illustrates the fact that different results can be obtained when different experimental methods are used. It is therefore advisable not to rely on a single method, especially in the case of emulsions of limited stability for reasons explained in the paper.

Why Bubbles Coalesce Faster than Droplets: The Effects of Interface Mobility and Surface Charge.

Air bubbles in pure water appear to coalesce much faster compared to oil emulsion droplets at the same water solution conditions. The main factors explaining this difference in coalescence times could be interface mobility and/or pH-dependent surface charge at the water interface. To quantify the relative importance of these effects, we use high-speed imaging to monitor the coalescence of free-rising air bubbles with the water-air interface as well as free-falling fluorocarbon-oil emulsion droplets with a water-oil interface. We measure the coalescence times of such bubbles and droplets over a range of different water pH values (3.0, 5.6, 11.0). In the case of bubbles, a very fast coalescence (milliseconds) is observed for the entire pH range in pure water, consistent with the hydrodynamics of fully mobile interfaces. However, when the water-air interface is immobilized by the deposition of a monolayer of arachidic acid, the coalescence is significantly delayed. Furthermore, the coalescence times increase with increasing pH. In the case of fluorocarbon-oil droplets, the coalescence is always much slower (seconds) and consistent with immobile interface coalescence. The fluorocarbon droplet's coalescence time is also pH-dependent, with a complete stabilization (no coalescence) observed at pH 11. In the high electrolyte concentration, a 0.6 M NaCl water solution, bubbles, and droplets have similar coalescence times, which could be related to the bubble interface immobilization at the late stage of the coalescence process. Numerical simulations are used to evaluate the time scale of mobile and immobile interface film drainage.

High internal phase emulsions stabilized by physically modified mung bean protein isolates under different pHs

This research explored the impact of modified mung bean protein isolates (MBPIs) on the physicochemical, rheological, and structural properties of 70% oil-containing high internal phase emulsions (HIPEs). MBPIs (4% protein concentration) were subjected to heating (90 °C for 2 h) or sequential heating/ultrasonication (20 kHz, 120 W for 10 min) at different pHs (2, 7, and 10). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of modified MBPIs confirmed heat treatment at pH 2 hydrolyzed MBPI, unlike MBPIs heated at pH 7 and 10. Sequential heating/ultrasonication significantly reduced particle size, improved solubility and surface hydrophobicity of MBPIs, resulting in smaller droplet size and enhanced gel-like properties of HIPEs. Transmission electron microscopy revealed that sequentially heated/ultrasonicated MBPIs in the oil–water interface existed in a fibrillar or randomly aggregated structure at pH 2, a randomly aggregated structure at pH 7, and a particulate aggregated structure at pH 10. Overall, these structural modifications at varied pH conditions influenced MBPI adsorption at the HIPE droplet interface, impacting rheological features and promoting the potential use of protein-stabilized HIPEs across diverse applications.

From Antagonism to Enhancement: Triton X-100 Surfactant Affects Phenanthrene Interfacial Biodegradation by Mycobacteria through a Shift in Uptake Mechanisms.

Polycyclic aromatic hydrocarbons (PAHs), as persistent environmental pollutants, often reside in nonaqueous-phase liquids (NAPLs). Mycobacterium sp. WY10, boasting highly hydrophobic surfaces, can adsorb to the oil-water interface, stabilizing the Pickering emulsion and directly accessing PAHs for biodegradation. We investigated the impact of Triton X-100 (TX100) on this interfacial uptake of phenanthrene (PHE) by Mycobacteria, using n-tetradecane (TET) and bis-(2-ethylhexyl) phthalate (DEHP) as NAPLs. Interfacial tension, phase behavior, and emulsion stability studies, alongside confocal laser scanning microscopy and electron microscope observations, unveiled the intricate interplay. In surfactant-free systems, Mycobacteria formed stable W/O Pickering emulsions, directly degrading PHE within the NAPLs because of their intimate contact. Introducing low-dose TX100 disrupted this relationship. Preferentially binding to the cells, the surfactant drastically increased the cell hydrophobicity, triggering desorption from the interface and phase separation. Consequently, PAH degradation plummeted due to hindered NAPL access. Higher TX100 concentrations flipped the script, creating surfactant-stabilized O/W emulsions devoid of interfacial cells. Surprisingly, PAH degradation remained efficient. This paradox can be attributed to NAPL emulsification, driven by the surfactant, which enhanced mass transfer and brought the substrate closer to the cells, despite their absence at the interface. This study sheds light on the complex effect of surfactants on Mycobacteria and PAH uptake, revealing an antagonistic effect at low concentrations that ultimately leads to enhanced degradation through emulsification at higher doses. These findings offer valuable insights into optimizing bioremediation strategies in PAH-contaminated environments.

Interfacial rheological properties of pepsin-hydrolyzed lentil protein isolate at oil-water interfaces

Lentil protein isolate (LPI) was investigated for its potential as a plant protein-based emulsifier. LPI consists mainly of globulins with high molecular weights which are relatively slow to adsorb and stabilize oil-water interfaces. Smaller proteins, such as whey protein, can stabilize the interface much faster, quickly forming a viscoelastic film that slows down the rate of droplet recoalescence, leading to smaller droplets. To increase the rate of adsorption, LPI was enzymatically hydrolyzed by pepsin at 1.5% and 4.5% degree of hydrolysis (DH), to obtain small peptides. The behavior of these peptides was studied at the oil-water interface in comparison to whey protein isolate (WPI) and native lentil protein isolate (LPI). Interfacial properties were investigated using dilatational and interfacial shear rheology in the linear viscoelastic regime (LVE) and nonlinear viscoelastic regime (NLVE) and these were related to protein characteristics and emulsion formation. The 1.5% and 4.5%DH LPI showed high surface hydrophobicity, and consisted mainly of low molecular weight peptides, which contributed to faster adsorption kinetics and consequently covered the interface faster than LPI. In dilatation, the native and hydrolyzed LPI-stabilized interfaces had comparable stiffness and were clearly weaker than WPI-stabilized interfaces, which contrasts with the results in shear deformations, where the former both had higher stiffness than WPI. Both hydrolyzed LPI and WPI formed more brittle and less stretchable interfaces compared to native LPI in both dilatational and shear rheology. In emulsification tests, native LPI produces the largest droplets, and the 4.5% DH LPI and WPI have the smallest droplet size. But, bridging flocculation was observed when emulsions were prepared with both hydrolyzed LPI, which may be attributed to inter-droplet hydrophobic interactions between small polypeptides. This can be linked to an increase in the surface hydrophobicity of hydrolyzed LPI. Thus, the use of native LPI as a stabilizer in emulsion preparation is preferable over the hydrolyzed samples, despite its larger droplet size.

Adsorption and inhibition of lipid oxidation of curcumin embeded egg ovalbumin/ sodium carboxymethylcellulose nanoparticles at the oil-in water interface

In this study, the adsorption and inhibition of lipid oxidation propertises of curcumin embeded ovalbumin (OVA)/sodium carboxymethylcellulose (CMC) were investigated. The results demonstrated that the adsorption of curcumin and OVA/CMC particles at the oil-water interface might form a dual protection. The larger emulsion droplets were formed at an OVA/CMC ratio of 1:2 (pH 4.4) due to bridging flocculation. In the other two ratios (1:1, 2:1), the emulsions showed good stability after 32 days of storage. At the ratios of 1:2, 1:1, and 2:1, the oxidation rate of the oil in the emulsion stabilized by OVA/CMC and OVA/CMC-Cur particles reduced by 16.2% and 37.9%, 4.9% and 38.9%, and 8.8% and 35.8%, respectively, than the pure oil. At the ratios of 1:1 and 2:1, the emulsion stabilized by the OVA/CMC-Cur particles demonstrated excellent antioxidant resistance and storage stability, particularly at the ratio of 1:1.

Aromatic poly (amino acids) as an effective low-temperature demulsifier for treating crude oil-in-water emulsions

Amphiphilic aromatic poly (amino acids) polymers were designed as biodegradability demulsifiers with higher aromaticity, stronger polarity, and side chain-like combs. The effects of demulsifier dosage, structural characteristics and emulsion properties such as pH, salinity, and oil content on the demulsification efficiency were investigated. The results show that the poly (L-glutamic-benzyl ester)-block-poly (L-phenylalanine) (PBLG15-b-PPA15) as the demulsifier can remove more than 99.97% of the oil in a 5.0 wt% oil-in-water (O/W) emulsion at room temperature within 2 min. The poly (L-tyrosine)-block-poly (L-phenylalanine) (PTyr15-b-PPA15) with environmental durability demonstrates high effectiveness, universality, and demulsification speed. It achieves a remarkable demulsification efficiency of up to 99.99% for a 20.0 wt% O/W emulsion at room temperature. The demulsification mechanism indicates that demulsifiers have sufficient interfacial activity can quickly migrate to the oil-water interface after being added to the emulsions. Additionally, when demulsifiers are present in a continuous phase in the molecular form, their "teeth" side chains are beneficial for increasing coalescence and flocculation capacities. Furthermore, according to the Density Functional Theory (DFT) calculations, enhancing the intermolecular interactions between demulsifiers and the primary native surfactants that form an oil-water interfacial film is a more efficient approach to reducing demulsification temperature and improving demulsification efficiency and rate.

Topological isomerism design of Demulsifiers: A fusion of molecular dynamics simulation and experiment

Demulsifiers are crucial for enhancing crude oil extraction and transportation efficiency by facilitating the separation of oil–water emulsions. However, research conducted on the design and synthesis of demulsifiers based on the results of molecular dynamics simulation remains scarce. Herein, we designed eight block polyethers, and explored their interfacial behaviors at the oil–water interface via molecular dynamics simulation. Correspondingly, eight block polyether demulsifiers were synthesized, and their interface properties were tested. The simulation results were consistent with the experimental results, indicating that the energy of simulation systems could be efficiently reduced by designed molecules, and that the prepared demulsifiers with the same structure could achieve effective demulsification correspondingly. Based on the simulation and experimental results, a “hand-shaped” demulsification mechanism model was proposed. The demulsifiers with hydrophobic “palm” and hydrophilic “fingers” demonstrated a more efficient performance in demulsification. The hydrophobic “palm” was stable in the continuous oil phase, and the hydrophilic “fingers” could attract dispersed water droplets to aggregate, facilitating demulsification. The study also finds that longer hydrophilic “fingers” exert stronger molecular force. Combining molecular dynamics simulation and experiment significantly accelerates the development of new demulsifiers, highlighting the utility of this approach in the research on demulsifiers.

Simulation and experimental study on amphiphilic modified graphene oxide for EOR

The application of nanosheet in enhanced oil recovery (EOR) offers a practical approach to resolving some surface-related problems. In this study, theoretical calculation and experiment were combined to study the interfacial behavior and mechanism of amphiphilic modified graphene oxide. Octadecyl amine and aspartic acid were successfully grafted onto graphene oxide nanosheets by starch template method. The stability of the modified structure was verified by IR, XRD and SEM. The change of microstructure in molecular simulation can enhance the understanding of the structure of amphiphilic modified nanosheets under SEM. The contact angle experiment directly shows its amphiphilicity, which shows that the contact angle of hydrophilic surface is 34.6° and that of hydrophobic surface is 103.5°. The interfacial elasticity experiment shows that the interfacial film formed by synthetic GOTA has certain elasticity. When the concentration increases, the interfacial film formed in the adsorption process can effectively separate the oil and water phases. Based on the interfacial tension value, the ability of graphene oxide and modified graphene oxide with different concentrations to reduce the interfacial tension between distilled water and diesel oil was investigated successively. The mechanism of GOTA action was explained from the aspects of molecular structure and energy by molecular simulation. The results show that the interfacial tension fluctuates around 16 mN/m when the GOTA concentration is 0.005%, and the average interfacial tension is 17.48 mN/m when the GOTA concentration (molecular number percentage) is 0.004% in the simulation process, which is highly consistent. Further studies have shown that the interface formation energy of the system is significantly reduced after the addition of zwitterionic surfactants, and the interfacial tension can be reduced to 11.95 mN/m. With the help of molecular simulation, the adsorption mechanism of GOTA on the interface is explained from the aspects of microstructure change, interaction energy, cohesion energy, interface density and conformation. The adjustment of these interactions will directly affect the oil-water interface morphology and interfacial tension.

Investigating the impact of ultrasound on the structural, physicochemical, and emulsifying characteristics of Dioscorin: Insights from experimental data and molecular dynamics simulation

This study investigated the impact of ultrasound treatment on dioscorin, the primary storage protein found in yam tubers. Three key factors, namely ultrasound power, duration, and frequency, were focused on. The research revealed that ultrasound-induced cavitation effects disrupted non-covalent bonds, resulting in a reduction in α-helix and β-sheet contents, decreased thermal stability, and a decrease in the apparent hydrodynamic diameter (Dh) of dioscorin. Additionally, previously hidden amino acid groups within the molecule became exposed on its surface, resulting in increased surface hydrophobicity (Ho) and zeta-potential. Under specific ultrasound conditions (200 W, 25 kHz, 30 min), Dh decreased while Ho increased, facilitating the adsorption of dioscorin molecules onto the oil-water interface. Molecular dynamics (MD) simulations showed that at lower frequencies and pressures, the structural flexibility of dioscorin's main chain atoms increased, leading to more significant fluctuations between amino acid residues. This transformation improved dioscorin's emulsifying properties and its oil-water interface affinity.

Fabrication of chitosan-based smart film by the O/W emulsion containing curcumin for monitoring pork freshness

In this research, curcumin (Cur) was encapsulated in succinylated soy protein isolate (SSPI) emulsion and combined with chitosan (CS) to prepare a smart film. The good adsorption ability of SSPI at the oil-water interface provides good physical stability for preparing Cur-loaded emulsion. These CS smart films containing SSPI emulsions with different curcumin content were evaluated on the structure, mechanical, barrier, antioxidant, antibacterial properties, and controlled release behavior. SEM and FT-IR results showed that the Cur-loaded emulsion was compatible with the CS matrix. By adding the emulsion, the film blocked 97.11% of ultraviolet radiation, reduced the water vapor transmission rate by 42%, and improved the swelling degree (32.26%), water solubility (12%), thermal stability and elongation at break (70.79 %) (p < 0.05). In addition, the film has a high antibacterial effect on Staphylococcus aureus and Escherichia coli (Bacterial inhibition zone diameter: 19.59 mm and 18.66 mm) and the release rate of curcumin in the film reaches 82.60%, mainly following the Fickian diffusion. The film gradually turns red under alkaline conditions, a property that makes the films successful in monitoring the deterioration of pork during storage. Adding SSPI emulsions and curcumin to films has great potential for food freshness monitoring and packaging.

“On-Water” accelerated dearomative cycloaddition via aquaphotocatalysis

Sulfur(VI) fluoride exchange (SuFEx) has emerged as an innovative click chemistry to harness the pivotal connectivity of sulfonyl fluorides. Synthesizing such alkylated S(VI) molecules through a straightforward process is of paramount importance, and their water-compatibility opens the door to a plethora of applications in biorelevant and materials chemistry. Prior aquatic endeavors have primarily focused on delivering catalysts involving ionic mechanisms, studies regarding visible-light photocatalytic transformation are unprecedented. Herein we report an on-water accelerated dearomative aquaphotocatalysis for heterocyclic alkyl SuFEx hubs. Notably, water exerts a pronounced accelerating effect on the [2 + 2] cycloaddition between (hetero)arylated ethenesulfonyl fluorides and inert heteroaromatics. This phenomenon is likely due to the high-pressure-like reactivity amplification at the water-oil interface. Conventional solvents proved totally ineffective, leading to the isomerization of the starting material.

Investigating aggregation of heavy oil droplets: Effect of asphaltene anionic carboxylic

Understanding the impact of asphaltene molecules on heavy oil droplet aggregation is vital for oil field development. Here, the impact of terminal carboxyl groups in asphaltene molecules on heavy oil droplet aggregation was investigated. Results suggest that the anionic asphaltenes were more readily adsorbed onto the water–oil interface than normal asphaltenes. Stacking structures between asphaltene and resin involve predominant face-to-face and edge-to-face aggregation. The anionic asphaltene system boosts grid strength (Asp-Asp interaction) and interaction with water (Asp-water interaction) among oil droplet molecules. We hope these insights that can offer strategies for improving the efficiency and sustainability of heavy oil extraction.

Demulsification of W/O emulsions induced by terahertz pulse electric fields-driven hydrogen bond disruption of water molecules

Demulsifying highly stable W/O emulsions, composed of heavy oil and water, is crucial for simplifying crude oil processing, reducing production costs, and mitigating environmental pollution. In these emulsions, aromatic components in the oil phase stack via π-π interactions, while hydrogen bonds stabilize the water phase. This leads to the creation of a strong oil-water interface through electrostatic attraction, ultimately hindering water droplet coalescence and oil-water separation. In this study, a 1.0 THz pulse electric field is introduced to effectively disrupt the hydrogen bond network among water molecules by inducing hydrogen bond resonance. This disruption contributes to increased water mobility in the oil phase, weakened stability of the oil-water interface film, and facilitates efficient water droplet coalescence in the oil phase. The results show that throughout the demulsification process, the average number of hydrogen bonds per water molecule rapidly decreases from 1.41 to 1.08 within 100 ps. The upper and lower limits of hydrogen bond lifetimes decrease by 8.12 ps and 3.24 ps, respectively. This indicates a significant disruption in the stability of hydrogen bonds between water molecules. Concurrently, the terahertz pulse electric field disrupts the initially stable oil-water interface film of the emulsion system, leading to a noteworthy reduction in the oil-water interface tension from 54.3 to 39.2 mN·m−1. The self-diffusion coefficient of water molecules increases from 1.33 to 2.62 Å2·ps−1, signifying that water molecules are more inclined to penetrate the interfacial region between the two phases. Additionally, the terahertz pulse electric field induces alterations in the arrangement of water molecules, resulting in the rearrangement of electrons in the water phase and disrupting the originally stable electrical double layer structure of the oil-water interface. This study provides novel insights into the development of efficient and environmentally friendly electric demulsification technologies, holding significant potential for widespread industrial applications.

Mechanism of highly efficient oil removal from spent hydrodesulfurization catalysts by ultrasound-assisted surfactant cleaning methods

The removal of crude oil from spent hydrodesulfurization catalysts constitutes the preliminary stage in the recovery process of valuable metals. However, the traditional roasting method for the removal exhibits massive limitations. In view of this, the present study used an ultrasound-assisted surfactant cleaning method to remove crude oil from spent hydrodesulfurization catalysts, which demonstrated effectiveness. Furthermore, the study investigated the mechanism governing the process with calculation and experiments, so as to provide a comprehensive understanding of the cleaning method’s efficacy. The surfactant selection was predicated on the performance in the IFT test, with SDBS and TX-100 finally being chosen. Subsequent calculations and analysis were then conducted to elucidate their frontier molecular orbitals, electrostatic potential, and polarity. It has been found that both SDBS and TX-100 possess the smallest LUMO-HOMO energy gap (ΔE), registering at 4.91 eV and 4.80 eV, respectively, and presenting the highest interfacial reactivity. The hydrophilic structure in the surfactant regulates the wettability of the oil-water interface, and the long-chain alkanes have excellent non-polar properties that promote the dissolution of crude oil. The ultrasonic-assisted process further improves the interface properties and enhances the oil removal effect. Surprisingly, the crude oil residue was reduced to 0.25% under optimal conditions. The final phase entailed the techno-economic evaluation of the entire process, revealing that, in comparison to the roasting method, this process saves $0.38 per kilogram of spent HDS catalyst, with the advantages of operational simplicity and emission-free. Generally, this study shed new light on the realization of efficient oil removal, with the salience of green, sustainable, and economical.