Mechanistic study on demulsification of water-in-diluted bitumen emulsions by ethylcellulose

Dissipative Particle Dynamics-Based Simulation of the Effect of Asphaltene Structure on Oil-Water Interface Properties

Asphaltenes are the main substances that stabilize emulsions during the production, processing, and transport of crude oil. The purpose of this research is to investigate the process of asphaltenes forming interfacial films at the oil-water interface by means of dissipative particle dynamics (DPD) and the effect of asphaltenes of different structures on the oil-water interface during the formation of interfacial film. It is demonstrated that the thickness of the interfacial film formed at the oil-water interface gradually increases as the asphaltene concentration rises and the amount of asphaltene adsorbed at the oil-water interface gradually multiplies. Both the number and type of heteroatoms in asphaltenes affect the interfacial behavior of asphaltenes. The interface activity of asphaltenes can be enhanced by increasing the number of heteroatoms in the asphaltene, and the type of heteroatom affects as well the interfacial activity of the asphaltene as it affects the aggregation behavior of the asphaltene in the system. As the number of asphaltene aromatic rings increases, the oil-water interfacial tension (IFT) trends down gradually, while the effect of alkyl side chains on the reduction of IFT of asphaltenes is different, and asphaltenes with medium length alkyl side chains can reduce IFT more efficiently.

Valorization strategies for hazardous proteinaceous waste from rendering production - Recent advances in specified risk materials (SRMs) conversion

Strict bans on specific risk materials (SRMs) are in place to prevent the spread of bovine spongiform encephalopathy (BSE). SRMs are characterized as tissues in cattle where misfolded proteins, the potential source of BSE infection, are concentrated. As a result of these bans, SRMs must be strictly isolated and disposed of, resulting in great costs for rendering companies. The increasing yield and the landfill of SRMs also exacerbated the burden on the environment. To cope with the emergence of SRMs, novel disposal methods and feasible value-added conversion routes are needed. The focus of this review is on the valorization progress achieved in the conversion of peptides derived from SRMs via an alternative disposal method, thermal hydrolysis. Promising value-added conversion of SRM-derived peptides into tackifiers, wood adhesives, flocculants, and bioplastics, is introduced. The potential conjugation strategies that can be adapted to SRM-derived peptides for desired properties are also critically reviewed. The purpose of this review is to discover a technical platform through which other hazardous proteinaceous waste, SRMs, can be treated as a high-demand feedstock for the production of renewable materials.

Demulsification of Crude Oil Emulsions Using Versatile and Eco-Friendly Demulsifiers Based on Cellulose Decorated with Imidazolium-Bearing Triazole Moiety

Water in the crude oil forms emulsions that must be broken before refining processes. Here, the novel and versatile derivatives of imidazolium ionic liquids (ILs) containing triazole moiety [SIm-TazCn][Br] were synthesized via click chemistry and then grafted onto the cellulose (CEL) to prepare eco-friendly demulsifiers for breaking water-in-oil (W/O) emulsions. The prepared compounds with two kinds of alkyl chains named CEL[SIm-TazC6][Br] and CEL[SIm-TazC10][Br] were characterized and employed for demulsifying W/O (30:70 and 50:50 vol %) emulsions. Also, the effect of the type and concentration of each demulsifier on the phase separation and dehydration efficiency (DE) were investigated through the bottle test. According to the bottle test results, the CEL[SIm-TazC6][Br] derivative at 4000 ppm showed a good DE of 79% after 5 min, which increased to 82% after 24 h. The interfacial tension (IFT) of derivatives at different concentrations was measured. The minimum IFT value of 16.3 mN/m was obtained for CEL[SIm-TazC6][Br] with a shorter alkyl chain at 4000 ppm after 24 h. The green and efficient CEL-based surfactants significantly demulsified the W/O emulsions because of the collaboration between imidazolium and triazole moieties.

CO2-Repurification Microemulsion Detergent for Oil-Based Slurry Cleaning

In order to solve problems such as environmental pollution and pipeline blockage caused by oily wastewater after washing, N,N-dimethylcyclohexylamine (DMCHA) with CO₂ response was selected as the oil phase, and an O/W microemulsion wellbore cleaning fluid with CO₂ switching characteristics was successfully prepared with erucamide propyl betaine (EAB-40), sodium dodecyl benzene sulfonate (SDBS), n-butanol, silicone defoamer, and water. The water content of the microemulsion was 89.99%, and it had good stability at 40 and -5 °C. The emulsion was rapidly demulsified after being injected with CO₂ in the CO₂-repurification microemulsion detergent, and CO₂ was removed with a N₂ detergent. The emulsion was restored to its original state, which demonstrated the CO₂/N₂ switching properties of the emulsion. It is proven that the switching microemulsion has a good wetting transformation ability by cleaning the steel sheet and quartz sheet contaminated by oil-based slurry. The switching microemulsion system can clean the simulated wellbore contaminated by oil-based slurry, and the cleaning efficiency is above 99%. CO₂ can be used at room temperature to separate oil and water from oily wastewater after cleaning.

Enhanced freeze-thawing stability of water-in-oil pickering emulsions stabilized by ethylcellulose nanoparticles and oleogels

This study developed water-in-oil (W/O) Pickering emulsions stabilized by ethylcellulose (EC) nanoparticles and EC oleogels, which presented significantly improved freeze-thawing (F/T) stability. Microstructural observation suggested EC nanoparticles were distributed at the interface and within the water droplets, and the EC oleogel trapped oil in the continuous phase. Freezing and melting temperatures of water in the emulsions with more EC nanoparticles were lowered and the corresponding enthalpy values were reduced. F/T led to lower water binding capacity but higher oil binding capacity of the emulsions, compared to the initial emulsions. Low field-nuclear magnetic resonance confirmed the increased mobility of water but decreased mobility of oil in the emulsions after F/T. Both linear and nonlinear rheological properties proved that emulsions exhibited higher strength and higher viscosity after F/T. The widened area of the elastic and viscous Lissajous plots with more nanoparticles suggested the viscosity and elasticity of emulsions were increased.

Application of imidazolium based ionic liquids grafted on microcrystalline cellulose as demulsifiers for water in crude oil (W/O) emulsions

Separation of water and oil from water-in-oil (W/O) emulsion before transportation and refining is very important and critical. Ionic liquids (ILs) and their derivatives have recently attracted much attention as efficient chemical agents for breaking emulsions. So, here, a series of microcrystalline cellulose (MCC) grafted with imidazolium-based ionic liquids (IM-ILs) were synthesized, named as MCC@IM-ILs, and evaluated as eco-friendly surface-active agents for the separation of water from the crude oil. Structure of the synthesized compounds was confirmed by different characterization techniques. Dehydration efficiency percent (DE%) of the synthesized demulsifiers was measured and compared with each other. Synthesized MCC@IM-ILs showed an acceptable DE% to demulsify three kinds of W/O emulsions with different water content after 5 min. Concentration, alkyl chain length, and counter-anion of the synthesized MCC@IM-ILs play a key role in separating water from crude oil. Demulsifier with C10 alkyl chain length showed better DE% than the corresponding demulsifier with C6 alkyl chain length in the W/O (30:70 v/v) emulsion. Also, demulsifier with Br counter anion showed lower DE% than the corresponding BF₄ ion-exchanged compound with higher hydrophilicity. Synthesized demulsifiers immobilized on ILs have significant advantages compared to unsupported ILs due to the use of green and economical cellulosic substrate.

Effect of Oil-Displacing Agent Composition on Oil/Water Interface Stability of the Asphaltene-Rich ASP Flooding-Produced Water

In this work, the effect of oil-displacing agent composition on oil/water interface stability of the asphaltene-rich alkali-surfactant-polymer (ASP) flooding-produced water was systematically investigated, especially from the perspective of the interaction between oil displacement agents and asphaltene at the oil/water interface. Primarily, adsorption behavior of the artificial and natural interfacial substances (oil displacement surfactant and asphaltenes) on the oil/water interface was investigated by molecular dynamics simulation. The oil displacement surfactant and asphaltenes formed a cross-linked and compact interfacial film structure, which significantly enhanced the interface stability; the more the oil displacement surfactants adsorbed on the interface, the more stable is the cross-linked structure formed between them and asphaltenes. Then, the interfacial property variations that are originating from the interactions differences between oil displacement agents and asphaltenes were monitored via interfacial tension, zeta potential, and interfacial film rheology tests. Moreover, the effect of oil displacement agent concentrations on the interfacial film thinning and rupture kinetic behavior was further investigated. Finally, cream experiments were conducted to verify the effect of oil displacement agent composition on the oil/water separation efficiencies of asphaltene-rich ASP flooding-produced water. When 5% asphaltenes was added, the creaming oil removal rate reduced from 90.0 to 85.3% at 19 h. The interactions between asphaltenes and oil displacement agents immensely enhance the oil/water interfacial film strength and impede the oil/water separation process.

A critical review of the development and demulsification processes applied for oil recovery from oil in water emulsions

The formation of stable emulsions is a fundamental problem in oil industry that can result in a sequence of environmental and operational problems. Chemical demulsification is extensively applied for the recovery of oil from water as well as water from oil. This review introduces different chemical demulsifiers applied for the demulsification and recovery of oil from oil in water (O/W) emulsions. Main types of surfactants (anionic, cationic, nonionics and amphoteric) involved in the formation of emulsions and enhances their stability were discussed. Promising demulsifiers such as nanoparticle (NP), hyperbranched polymers, and ionic liquids (IL), which achieved high oil recovery rate, parameters influencing demulsification efficiency and demulsification mechanisms were explored. Lastly, improvements, challenges, and new changes being made to chemical demulsifiers were underlined. Functionalized magnetic nanoparticles and hyperbranched polymers were very effective in recovering oil from O/W emulsions with an efficiency >95%. Polymers with highly hydrophilic content and high molecular weight can achieve excellent oil recovery rates due to higher interfacial activity, higher dispersion, and presence of specific functional groups. Although ionic liquids could achieve oil recovery up to 90%, high cost limits their applications. NPs showed excellent oil recovery behavior at low concentrations and ambient temperature. Demulsification efficiency of NPs can be enhanced by functionalize with other components (e.g., polymers and surfactants), while service life can be extend by silica coating. Future challenges include scaling up the use of NPs in oil recovery process and highlighting contrasts between lab-scale and field-scale applications.

Demulsification of water-in-crude oil emulsion driven by a carbonaceous demulsifier from natural rice husks

Removing emulsified water from a water-in-crude oil (W/O) emulsion is critically required prior to downstream processing in the petroleum industry. In this work, environmentally friendly and amphipathic rice husk carbon (RHC) demulsifier was prepared by a simple carbonization process in a muffle furnace using rice husks as starting materials. RHC was characterized by field-emission scanning electron microscope, energy dispersive spectrometer, Fourier transform infrared spectrometer, ultraviolet-visible spectrometer, powder X-ray diffraction, zeta potential and synchronal thermal analyzer. The factors such as dosage, temperature, settling time, pH value and salinity were systematically investigated. The results indicated that the dehydration efficiency (DE) reached as high as 96.99% with 600 mg/L of RHC for 80 min at 70 °C. RHC exhibited an optimal DE under neutral condition, but it was also effective under acidic and alkaline conditions. Also, it had an excellent salt tolerance. The possible demulsification mechanism was explored by interfacial properties, different treatment methods for RHC and microexamination. The demulsification of RHC is attributed to its high interfacial activity, oxygen-containing groups and content of silica. It indicates that RHC is an effective demulsifier for the treatment of the W/O emulsion.

Synthesis and Study of a New Type of Fluorinated Polyether Demulsifier for Heavy Oil Emulsion Demulsification

To solve the problem of heavy oil demulsification difficulties in Liaohe Oilfield, phenolamine resin initiator was synthesized from p-trifluoromethyl phenol, and then FB series fluorinated polyether demulsifiers were synthesized by block polymerization using ethylene oxide (EO) and propylene oxide (PO) as raw materials. The demulsifiers were characterized by infrared spectroscopy, cloud point, hydrophilic-lipophilic balance (HLB) value, and surface tension. The demulsifying and dehydrating properties were tested by demulsifying and dehydrating experiments, the demulsification mechanism was analyzed by the microscopic demulsification process test, and the influence of demulsifier addition and demulsifying temperature on demulsifying performance was also studied. The results showed that under the condition of the optimum demulsification temperature of 60 °C and the optimum demulsifier dosage of 100 mg/L, the water removal (%) of fluorinated polyether demulsifier of FB 4 was the highest, and the overall water removal (%) of 50 mL crude oil emulsion in Liaohe Oilfield reached 90.33% within 2 h, which was better than the current demulsifier used in Liaohe crude oil.

Methods to monitor water-in-oil film thinning and stability: An application to bitumen demulsification

Understanding what governs the water-in-oil emulsion film stability and demulsification is important for science and technology. The demulsification of the tar sands' water-in-bitumen emulsion and proposing methods for demulsification with an efficient demulsifier (emulsion breaker) are important but challenging tasks. Despite the long period of time researchers have been examining the factors governing bitumen emulsion stability and demulsification, these concepts are still not well understood and require more study. Due to the lack of suitable robust methods to reveal what governs bitumen emulsion thinning and stability, additional study is needed. The goal of this research is to provide an understanding of the role of the asphaltene-resin nanoparticles on the bitumen film and emulsion stability and to propose a possible solution to the challenges presented. The techniques were developed and applied to monitor the curved and flat bitumen emulsion films' thinning in transmitted and reflected light. The observed plane bitumen emulsion film stepwise thinning in reflected light interferometry reveals the role of the layered-lattice film structural stabilization. The role of the asphaltene-resin structure formation on film stability is discussed and a model is proposed. The data obtained by the techniques help to propose a methodology to optimize the performance of the demulsifier.

Synthesis and Study of a New Type of Nonanionic Demulsifier for Chemical Flooding Emulsion Demulsification

The application of chemical flooding improves the stability of the produced emulsion, which reduces the demulsification efficiency of conventional demulsifiers. To improve the demulsification effect, in this paper, a new multibranched nonanionic polyether demulsifier, FYJP, was prepared by grafting carboxylate based on a nonionic demulsifier. The FYJP demulsifier could generate an initiator through p-tert-butylphenol, triethylenetetramine, and methanol, which was polymerized with ethylene oxide (EO) and propylene oxide (PO) to produce a nonionic polyether demulsifier. Sodium chloroacetate was used to modify the polyether demulsifier to obtain a new type of nonanionic polyether demulsifier. The FYJP polyether demulsifier was characterized by the hydrophilic-lipophilic balance (HLB) value, relative solubility (RSN), and surface activity of the demulsifier, and the demulsification mechanism was analyzed by a microscopic demulsification process test, and the effect of demulsifier dosage on the demulsification effect was discussed. Meanwhile, a dehydration test was carried out. The experimental results showed that the highest dehydration rate of the demulsifier was 94.7% at 85 °C, 100 ppm demulsifier dosage, 50 mL of a W/O emulsion, and 120 min demulsification time. The abovementioned studies show that FYJP is an effective demulsifier for chemical flooding emulsions, and this work promises to provide a reference for future demulsifier research.

Influence of Surfactant and Weak-Alkali Concentrations on the Stability of O/W Emulsion in an Alkali-Surfactant-Polymer Compound System

Emulsions have emerged as advanced materials for wide industrial applications because of their unique properties. In the actual application in oilfields, emulsions can significantly enhance oil recovery. In the present study, the stability test shows that the concentrations of a surfactant and alkali and salinity have a great influence on the stability of the emulsion, but the addition of excessive chemical agents may adversely affect the emulsion stability. The addition of excessive alkali causes the phase inversion behavior of the emulsion to be discovered, which is also the main reason for the destabilization of the oil-in-water emulsion. Rheological experiments reveal that the emulsion produced by the chemical-flooding fluid is a pseudoplastic fluid, and the apparent viscosity decreases with the increase of the shear rate. Core-flooding experiments were conducted to study the effect of the emulsion stability on enhanced oil recovery, and the results indicate that the system with a better emulsion stability has higher oil recovery and displacement pressure.

Emulsification of Surfactant on Oil Droplets by Molecular Dynamics Simulation

Heavy oil in crude oil flooding is extremely difficult to extract due to its high viscosity and poor fluidity. In this paper, molecular dynamics simulation was used to study the emulsification behavior of sodium dodecyl sulfonate (SDSn) micelles on heavy oil droplets composed of asphaltenes (ASP) at the molecular level. Some analyzed techniques were used including root mean square displacement, hydrophile-hydrophobic area of an oil droplet, potential of mean force, and the number of hydrogen bonds between oil droplet and water phase. The simulated results showed that the asphaltene with carboxylate groups significantly enhances the hydration layer on the surface of oil droplets, and SDSn molecules can change the strength of the hydration layer around the surface of the oil droplets. The water bridge structure between both polar heads of the surfactant was commonly formed around the hydration layer of the emulsified oil droplet. During the emulsification of heavy oil, the ratio of hydrophilic hydrophobic surface area around an oil droplet is essential. Molecular dynamics method can be considered as a helpful tool for experimental techniques at the molecular level.

CO2/N2-responsive oil-in-water emulsions using a novel switchable surfactant

HYPOTHESIS

Recently, switchable or stimuli-responsive emulsions have attracted much research interest in many industrial fields. In this work, a novel CO₂/N₂-responsive surfactant was designed and developed to facilitate the formation of switchable oil-in-water (O/W) emulsions with fast switching characteristics between a stable emulsion and separate phases upon alternatively bubbling CO₂ and N₂.

EXPERIMENTS

The novel CO₂/N₂-responsive surfactant was facilely prepared by mixing an anionic fatty acid (oleic acid) and a cationic amine (1,3-Bis (aminopropyl) tetramethyldisiloxane) at a 1:1 molecular ratio, which was assembled based on electrostatic interactions. The structure and properties of the novel CO₂/N₂-responsive switchable surfactant were investigated by Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (¹H NMR) spectroscopy, and interfacial tensions.

FINDINGS

The developed surfactant shows an excellent interfacial activity at the oil/water interface, which can significantly reduce the dosage of the switchable surfactant compared with previous CO₂/N₂-responsive surfactants. The dynamic interfacial tension of n-decane and aqueous phase decreased from 45 mN m^-1 to 5 mN m^-1 within 100 s with the addition of 0.2 mM surfactant. In this work, a low concentration of the novel switchable surfactant (e.g., 20.0 mM) can realize reversible emulsification and demulsification in an emulsion system as compared with the high dosage (e.g., ~150 mM) in previous reports, which will bring huge economic benefits in industrial applications in the future. Moreover, this work expands the family of ion-pair surfactants to small amino-functionalized molecules beyond Jeffamine D-230, which promotes the development of simple and switchable ion-pair surfactant. It is found that the O/W emulsions stabilized by the switchable surfactant show excellent stability, which can be stored for over 60 days at room temperature without any obvious change. Interestingly, the stable O/W emulsion is completely demulsified upon bubbling CO₂ for 30 s and can be easily re-emulsified to the initial state after purging N₂ at 60 °C within 10 min, which demonstrates a rapid and highly efficient switching behavior. The reversible emulsification and demulsification process is ascribed to the reversible assembly and disassembly of the switchable surfactant, which is induced by the removal and purge of CO₂.

Application of biosurfactant surfactin as a pH-switchable biodemulsifier for efficient oil recovery from waste crude oil

Efficient oil separation is the most desirable, but still challenging solution for the waste crude oil problem. This study developed biosurfactant surfactin as a novel pH-switchable biodemulsifier for efficient oil separation. As found, surfactin demulsification achieved a quite well oil separation ratio of over 95% on model emulsions after 20 min at 50 °C. The validity of this demulsification process should be mainly based on the readily lost stabilization ability of surfactin in emulsions triggered by acid addition. Then, surfactin (0.2 g/L) treatment with the aid of ethanol (2%) to improve its distribution could recover over 95% of oil from waste crude oil. After treated by surfactin, the separated oil phase contains tiny water (less than 0.5%) and thus can be reused for resource recycling to reach a compromised balance between satisfying the strict environmental regulations and decreasing the high treatment costs. Hence, in consideration of high demulsification efficiency, environmental-friendly properties and cost-efficiency, surfactin has a great potential for industrial applications for oil recovery from waste crude oil which is a severe problem presents in most of the petroleum-related factories.

Practical Modification of Tannic Acid Polyether Demulsifier and Its Highly Efficient Demulsification for Water-in-Aging Crude Oil Emulsions

In order to break the aging crude oil (WACO) emulsion of the offshore platform more effectively, a highly active isocyanate, polyaryl polymethylene isocyanate (PAPI), was selected to modify the pilot-scale tannic acid demulsifier. In the addition of PAPI, its molecular weight and viscosity dramatically increased, while its relative solubility, hydroxyl number, and cloud point exhibited an opposite direction, showing an increase in hydrophobicity. After adding the above modified demulsifier, a remarkably improved water removal of WACO emulsion accompanied by a notable reduction of the water content in the oil phase monitored by the Karl Fischer method was observed. Demulsification on the offshore platform demonstrated that the best water removal was achieved when the proportion of PAPI is 1.5 wt %. Its demulsification efficiency reached 95.7%, which was 25.6% higher than the 76.2% of unmodified demulsifier. In addition, a positive correlation between viscoelasticity of emulsion and demulsification performance was found by only adjusting the parameters of the rheometer. This method may be utilized to characterize the demulsification performance by any rotary rheometer. The pilot-scale demulsification experiment demonstrated that the water removal can reach 98.14 vol % and residual water content was only 0.55 vol %. These results further confirmed the excellent demulsification performance of the modified demulsifier toward the WACO emulsion in production.

Gelation on demand using switchable double emulsions: A potential strategy for the in situ immobilization of organic contaminants

Switchable double emulsions (water in oil in water, W/O/W) are proposed for the in situ immobilization of subsurface organic contaminants such as toluene, hexane or benzene. Primary W/O emulsions were prepared by emulsifying 250 mL of 0.36 M CaCl₂ aqueous solutions in 1 L of canola oil (with 12.5 g/L of ethylcellulose, EC, and 2.5 g/L of calcium stearate). In the primary W/O emulsion the water droplets in oil were ≈8 μm, as observed using an optical and a confocal microscope. EC and calcium stearate adsorbed at the oil water interface (as demonstrated by interfacial tension measurements), forming films which stabilized the W/O emulsions (as verified with bottle tests). Experiments conducted using a Langmuir trough suggest that EC and calcium stearate films did not desorb from the oil-water interface upon compression. Crumpling tests and optical microscopy observations indicate that EC and calcium stearate films were skin-like, and buckled when deformed. To obtain double W/O/W emulsions the primary emulsions were emulsified in a 0.75 wt% solution of sodium alginate, with 2 mL/L of Tween 20 and 10 g/L of NaCl. The formation of W/O/W emulsions was verified through optical microscopy and confocal microscopy observations. In the absence of the contaminants the double emulsions were stable, as observed by resting them on the bench over three days and agitating them with a multi-action wrist shaker for 30 min. Also, they had low shear elastic (G' = 2.67 ± 0.58 Pa) and viscous (G″ = 1.69 ± 0.24 Pa) moduli, which should facilitate their transport through geological media (e.g. soil) to polluted areas. Upon mixing with toluene, hexane or benzene at concentrations ranging from 5% to 17%, the double emulsions were destabilized. Emulsion destabilization caused the release of CaCl₂, which crosslinked sodium alginate and formed gels in which the contaminants were incorporated. The gelation rate and the magnitude of the viscoelastic moduli depended on the contaminant type and concentration, and on the mixing time. Gelation occurred fastest with the highest toluene concentrations tested (9% to 17%), but the highest elastic moduli were measured with 9% toluene concentrations for the longest mixing times tested (90 s). Gelation occurred slowest with hexane, likely due to the poor solubility of EC in hexane. Because of their ability to gel exclusively in contaminant proximity, the double emulsions studied offer a potential strategy to control the migration of plumes of contaminants such as toluene, hexane or benzene.

Effect of Ethylcellulose on the Rheology and Mechanical Heterogeneity of Asphaltene Films at the Oil-Water Interface

Asphaltenes are surface-active molecules that exist naturally in crude oil. They adsorb at the water-oil interface and form viscoelastic interfacial films that stabilize emulsion droplets, making water-oil separation extremely challenging. There is, thus, a need for chemical demulsifiers to disrupt the interfacial asphaltene films, and, thereby, facilitate water-oil separation. Here, we examine ethylcellulose (EC) as a model demulsifier and measure its impact on the interfacial properties of asphaltene films using interfacial shear microrheology. When EC is mixed with an oil and asphaltene solution, it retards the interfacial stiffening that occurs between the oil phase in contact with a water phase. Moreover, EC introduces relatively weak regions within the film. When EC is introduced to a pre-existing asphaltene film, the stiffness of the films decreases abruptly and significantly. Direct visualization of interfacial dynamics further reveals that EC acts inhomogeneously, and that relatively soft regions in the initial film are seen to expand. This mechanism likely impacts emulsion destabilization and provides new insight to the process of demulsification.

Application of α-amylase as a novel biodemulsifier for destabilizing amphiphilic polymer-flooding produced liquid treatment

The performance and de-emulsification mechanism of α-amylase, a novel environmental friendly biodemulsifier in petroleum industry, was investigated at room temperature. The effects of α-amylase on the viscosity of amphiphilic polymer solution and de-emulsification rate were studied by changing the concentration of α-amylase, temperature and salinity. Polymer molecular weight, Zeta potential, interfacial film strength and interfacial tension were measured to investigate the de-emulsification mechanism of α-amylase. The results show that α-amylase is an efficient biodemulsifier to increase the de-emulsification rate of amphiphilic polymer emulsions. Hydrolysis of α-amylase to amphiphilic polymers destroys the structure of the amphiphilic polymer, thereby reduces the viscosity and the interfacial film strength of the system. Once de-emulsification is completed, the lower layer, i.e. the emulsified layer, will be clear. Thus, α-amylase can be applied as an effective de-emulsifier for amphiphilic polymer-stabilized O/W emulsion.

Solvent-terminated dispersive liquid-liquid microextraction: a tutorial

Solvent-terminated dispersive liquid-liquid microextraction (ST-DLLME) is a special mode of DLLME in which a demulsifying solvent is injected into the cloudy mixture of sample/extractant to break the emulsion and induce phase separation. The demulsification process starts by flocculation of the dispersed microdroplets by Ostwald ripening or coalescence to form larger droplets. Then, the extractant either floats or sinks depending on its density as compared with that for the aqueous sample. The demulsifier should have high surface activity and low surface tension in order to be capable of inducing phase separation. The extraction efficiency in ST-DLLME is controlled by the same experimental variables of normal DLLME (n-DLLME) such as the type and volume of the extractant as well as the disperser. Other parameters such as pH and the temperature of the sample, the stirring rate, the time of extraction and the addition of salt are also important to consider. Along with these factors, the demulsifier type and volume and the demulsification time have to be optimized. By using solvents to terminate the dispersion step in DLLME, the centrifugation process is not necessary. This in turn improves precision, increases throughput, decreases the risk of contamination through human intervention and minimizes the overall analysis time. ST-DLLME has been successfully applied for determination of both inorganic and organic analytes including pesticides and pharmaceuticals in water and biological fluids. Demulsification via solvent injection rather than centrifugation saves energy and makes ST-DLLME easier to automate. These characteristics in addition to the low solvent consumption, the reduced organic waste and the possibility of using water in demulsification bestow green features on ST-DLLME. This tutorial discusses the principle, the practical aspects and the different applications of ST-DLLME.

Yeasts and bacterial biosurfactants as demulsifiers for petroleum derivative in seawater emulsions

Oil sludge or waste generated in transport, storage or refining forms highly stable mixtures due to the presence and additives with surfactant properties and water forming complex emulsions. Thus, demulsification is necessary to separate this residual oil from the aqueous phase for oil processing and water treatment/disposal. Most used chemical demulsifiers, although effective, are environmental contaminants and do not meet the desired levels of biodegradation. We investigated the application of microbial biosurfactants as potential natural demulsifiers of petroleum derivatives in water emulsions. Biosurfactants crude extracts, produced by yeasts (Candida guilliermondii, Candida lipolytica and Candida sphaerica) and bacteria (Pseudomonas aeruginosa, Pseudomonas cepacia and Bacillus sp.) grown in industrial residues, were tested for demulsification capacity in their crude and pure forms. The best results obtained were for bacterial biosurfactants, which were able to recover about 65% of the seawater emulsified with motor oil compared to 35–40% only for yeasts products. Biosurfactants were also tested with oil-in-water (O/W) and water-in-oil (W/O) kerosene model emulsions. No relationship between interfacial tension, cell hydrophobicity and demulsification ratios was observed with all the biosurfactants tested. Microscopic illustrations of the emulsions in the presence of the biosurfactants showed the aspects of the emulsion and demulsification process. The results obtained demonstrate the potential of these agents as demulsifiers in marine environments.

Biosurfactant surfactin with pH-regulated emulsification activity for efficient oil separation when used as emulsifier

In the present study, the pH-regulated emulsification activity of surfactin was studied and its potential application in oil separation towards enhanced oil recovery (EOR) was investigated. As demonstrated, surfactin can stabilize emulsions quite well beyond pH 7.4. An oil emulsification ratio of about 98% was obtained at pH 11.0; while this emulsification activity was rapidly and completely lost when pH decreased to below 3.0, having an oil separation ratio of over 98%. This pH-sensitive property is probably due to surfactin dissolution-precipitation induced by the ionization-protonation of a carboxyl group in its structure under alkaline or acidic conditions. This property allows oil emulsification or oil separation to be readily achieved via simple pH adjustments when surfactin is used as an emulsifier. Furthermore, surfactin sustained its activity after demulsification and can be readily reused many times. The above obtained results indicated surfactin-based EOR processes have great application feasibility.

pH Switchable Emulsions Based on Dynamic Covalent Surfactants

Dynamic covalent surfactants were designed to prepare pH switchable emulsions. A dynamic covalent bond between nonamphiphilic building blocks (polyethylenimine (PEI) and benzaldehyde (B)) was introduced to form the dynamic covalent surfactant PEI-B. The dynamic nature of covalent bond in PEI-B was confirmed by ¹H NMR and fluorescence probe analysis. Stable emulsions were successfully prepared with interfacial active PEI-B at pH 7.8 with various water/paraffin oil ratios under sonication. When lowering the pH to 3.5, a complete phase separation was observed as a result of breaking dynamic covalent bond in the interfacial active PEI-B. After tuning the pH back to 7.8, stable emulsion was obtained again due to the reformation of the dynamic covalent bond and hence interfacial active PEI-B. The emulsification and demulsification were dependent on the formation and breaking of dynamic covalent bond in PEI-B. Such pH-triggered emulsification and demulsification can be switched at least three times. Application of dynamic covalent surfactants will open up a novel route for preparing responsive emulsions.

Probing Molecular Interactions of Asphaltenes in Heptol Using a Surface Forces Apparatus: Implications on Stability of Water-in-Oil Emulsions

The behaviors and molecular interactions of asphaltenes are related to many challenging issues in oil production. In this study, the molecular interaction mechanism of asphaltenes in Heptol solvents of varying toluene/n-heptane ratio were directly measured using a surface forces apparatus (SFA). The results showed that the interactions between asphaltene surfaces gradually changed from pure repulsion to weak adhesion as the weight ratio of toluene (ω) in Heptol decreased from ω = 1 to 0. The measured repulsion was mainly due to the steric interactions between swelling asphaltene molecules and/aggregates. The micropipet technique was applied to test the stability of two water-in-oil emulsion droplets attached to glass pipettes. A computer-controlled 4-roll mill fluidic device was also built in-house to investigate the interaction of free-suspending water-in-oil emulsions under dynamic flow conditions. Both micropipet and 4-roll mill fluidic tests demonstrate that asphaltenes adsorbed at oil/water interfaces play a critical role in stabilizing the emulsion drops, in agreement with the repulsion measured between asphaltene surfaces in toluene using SFA, and that interfacial sliding or shearing is generally required to destabilize the protective interfacial apshaltene layers which facilitates the coalescence of emulsion drops. Our results provide insights into the fundamental understanding of molecular interaction mechanisms of asphaltenes in organic solvents and stabilization/destabilization behaviors of water-in-oil emulsions with asphaltenes.

Synthesis of Surface-Responsive Composite Particles by Dehydration of Water-in-Oil Emulsions

Organic composite particles were prepared by first emulsifying an aqueous sodium carboxymethyl cellulose (CMC) solution in a nonaqueous ethylcellulose (EC) solution, followed by dehydrating emulsified water droplets. CMC and EC are both biodegradable nontoxic materials, but have contrasting properties. CMC is a charged water-soluble polymer, while EC is an uncharged interfacially active water-insoluble polymer. The simple preparative method does not consume unnecessary chemical reagents and produces no waste material. The composite particles prepared by dehydrating emulsion droplets are readily dispersed in organic media due to its biwettable surface terminated with interfacially active EC molecules, which allows composite particles to preferentially adsorb at the oil-water droplet interface. The surface of composite particles, furthermore, is water-permeable, which allows water to be absorbed from emulsified droplets. The size, composition, and structure of the synthesized composite particles are ideally suited for absorption of stabilized water droplets from oil-continuous emulsions. The use of the composite absorbent particles, described herein, presents another viable strategy for dewatering water-in-oil emulsions.

Interfacial sciences in unconventional petroleum production: from fundamentals to applications

With the ever increasing demand for energy to meet the needs of growth in population and improvement in the living standards, in particular in developing countries, the abundant unconventional oil reserves (about 70% of total world oil), such as heavy oil, oil/tar sands and shale oil, are playing an increasingly important role in securing global energy supply.

Investigation of demulsification efficiency in water-in-crude oil emulsions using dissipative particle dynamics

Demulsification efficiency with alternating hydrophobic blocks of the polyether is investigated by dissipative particle dynamics.