Determination of chiral prothioconazole and its chiral metabolite in water, juice, tea, and vinegar using emulsive liquid-liquid microextraction combined with ultra-high performance liquid chromatography

Emulsive liquid-liquid microextraction (ELLME), a simple, rapid, and environmentally friendly technique, was established to identify chiral prothioconazole and its chiral metabolite in water, juice, tea, and vinegar using ultra-high-performance liquid chromatography (UPLC). Environmentally friendly extractant was mixed with pure water to prepare a high-concentration emulsion, which was added to samples to complete the emulsification and extraction in 1 s. Afterward, an electrolyte solution was added to complete the demulsification without centrifugation. ELLME did not use dispersants compared to the familiar dispersive liquid-liquid microextraction (DLLME), thus reducing the use of toxic solvents and avoiding the effect of dispersants on the partition coefficient. The linear range was from 0.01 to 1 mg/L. The limit of detection was 0.003 mg/L. The extraction recoveries ranged from 82.4 % to 101.6 %, with relative standard deviations of 0.7-5.2 %. The ELLME method developed has the potential to serve as an alternative to DLLME.

Mechanism study of aging oil demulsification and dehydration under ultrasonic irradiation

With the tertiary oil recovery in the oilfield, the content of aging oil emulsion with high water content and complex components has become more prevalent, so it is crucial for aging oil to break the emulsification. In this paper, the experimental laws of water content are explored under the conditions of different transducer input powers through the ultrasonic reforming of aging oil, and the microscopic topography, particle size, components, etc. of oil samples before and after the irradiation of ultrasound are characterized through the microscopic analysis, particle size analysis and component analysis and other ways. The results show that the oil samples achieve the effect of demulsification and dehydration in the presence of ultrasonic cavitation effect, with a maximum dehydration rate of 98.24 %, and that the dehydration rate follows an "M-type" trend with the increase of power. The results of microscopic and particle size analyses demonstrate that ultrasonic irradiation destabilizes the oil-water interfacial membrane, and causes droplets of different sizes to collide, agglomerate, and settle. It was also observed that the droplets of the emulsion system are more evenly distributed and the intervals are increased. Furthermore, we hypothesize that ultrasound may be less irreversible in demulsification and dehydration of aging oil.

Pretreatment of alkali/surfactant/polymer (ASP)-flooding produced wastewater by electron beam radiation to improve oil-water separation

The management of wastewater produced from alkali/surfactant/polymer (ASP) flooding, known for its considerable volume and high emulsion stability, poses a challenge in oilfields globally. This study has demonstrated that ionizing irradiation is a promising pretreatment method for ASP wastewater to improve oil-water separation. After a settling time of 1 h, approximately 69.5% of oil remained in the raw ASP wastewater, while only 20-29% of the oil persisted in the liquid phase following radiation at absorbed doses ranging from 0.1 to 5.0 kGy. A noticeable increase in the size of oil droplets and reduction in turbidity was observed after irradiation. Further analysis revealed that the combination of surfactant, sodium dodecyl sulfate (SDS) and alkali exhibits a synergistic impact, leading to a substantial reduction in interface tension of ASP wastewater. Notably, ionizing irradiation induces several key changes that are crucial for efficient demulsification. The transformation of the wastewater's rheological behavior from pseudoplastics to a Newtonian fluid accompanied by a reduction in viscosity, the increased interfacial tension at both liquid-air and liquid-oil interfaces, along with the degradation of organic components such as partly hydrolyzed polyacrylamide (HPAM) and SDS, all contribute to the coalescence and floatation of oil droplets.

Nanomagnetic Cyclodextrin decorated with ionic liquid as green and reversible Demulsifier for breaking of crude oil emulsions

Application of the chemical demulsifiers is the best choice for breaking the water in crude oil (W/O) emulsions in the petroleum industry. Here, novel, environmentally friendly, efficient, and easily reusable Fe3O4 nanomagnetic compounds based on imidazolium-decorated cyclodextrin were successfully synthesized and applied to demulsify the water in crude oil (W/O) emulsions. At first, Fe3O4 nanoparticles were decorated with β-cyclodextrin (β-CD) to prepare Fe3O4@β-CD@IL magnetic nanoparticles. Then, imidazole (Im) was separately reacted with 1-bromohexane and 1-bromodecane to prepare [Im-C6][Br] and [Im-C10][Br] ionic liquids, respectively. The prepared imidazolium-based ionic liquids were reacted with N-propyltriethoxysilane to synthesize [ImSi-C6][Br] and [ImSi-C10][Br]. Finally, [ImSi-Cn][Br] was immobilized on Fe3O4@β-CD to obtain nanomagnetic demulsifiers. Structure of the synthesized compounds was confirmed using different methods such as FT-IR, NMR, and elemental analysis. TGA, VSM, and FESEM methods were used to investigate the thermal stability, magnetic properties, and the morphology, respectively. Fe3O4@βCD and Fe3O4@βCD@[ImSi-C10][Br] nanoparticles respectively showed the particle size in the range of 40-70 nm and 50-80 nm. After grafting the imidazolium-based ionic liquid on the surface of support, the magnetization number reduced from 25.6 emu/g for Fe3O4@β-CD to 24.9 emu/g for Fe3O4@β-CD@[ImSi-C10][Br]. Synthesized material employed to break the (10:90 and 30:70 Vol%) W/O emulsions at the concentration range of 1000-5000 ppm. The maximum demulsification efficiency (DE%) of 92 % was obtained using a Fe3O4@β-CD@[ImSi-C10][Br] at 5000 ppm for (30:70 Vol%) W/O emulsion within 24 h. Interfacial tension (IFT) values decreased with increasing the DE%. The Fe3O4@βCD@[ImSi-C10][Br] demulsifier was reused five times with acceptable yields. The cooperation of imidazolium and β-CD in the green nanomagnetic demulsifiers led to the efficient demulsification of the W/O emulsions. The preparation of different ionic liquids or changing the counter anions are our potential future directions for this research. Demulsification at high demulsifier concentration can be considered a limitation of the nanomagnetic cyclodextrin decorated with ionic liquid. But due to the low amount of ionic liquid immobilized in the synthesized demulsifier, the cost of the final demulsifier is lower that other demulsifiers with full ionic liquid backbones, which increases its potential for industrial applications.

Advances in ultrasonic treatment of oily sludge: mechanisms, industrial applications, and integration with combined treatment technologies

In the petroleum sector, the generation of oily sludge is an unavoidable byproduct, necessitating the development of efficient treatment strategies for both economic gain and the mitigation of negative environmental impacts. The intricate composition of oily sludge poses a formidable challenge, as existing treatment methodologies frequently fall short of achieving baseline disposal criteria. The processes of demulsification and dehydration are integral to diminishing the oil content and reclaiming valuable crude oil, thereby playing a critical role in the management of oily sludge. Among the myriad of treatment solutions, ultrasonic technology has emerged as a particularly effective physical method, celebrated for its diverse applications and lack of resultant secondary pollution. This comprehensive review delves into the underlying mechanisms and recent progress in the ultrasonic treatment of oily sludge, with a specific focus on its industrial implementations within China. Both isolated ultrasonic treatment and its combination with other technological approaches have proven successful in addressing oily sludge challenges. The adoption of industrial-scale systems that amalgamate ultrasound with multi-technological processes has shown marked enhancements in treatment efficacy. The fusion of ultrasonic technology with other cutting-edge methods holds considerable potential across a spectrum of applications. To fulfill the goals of resource recovery, reduction, and neutralization in oily sludge management, the industrial adoption and adept application of a variety of treatment technologies are imperative.

Synthesis and application of recyclable magnetic cellulose nanocrystals for effective demulsification of water in crude oil emulsions

The development of eco-friendly, efficient, and economical demulsifiers for the demulsification of water in crude oil emulsion is one of the important issues in the petroleum industry. Demulsifiers with suitable performance in several demulsification methods are good choices for effective and economical demulsification. In this study, recyclable magnetic cellulose nanocrystals have been synthesized from cotton by a simple method and used in the demulsification of water in crude oil emulsions. Chemical and magnetic demulsification by magnetic cellulose nanocrystals has been investigated. In addition, the effects of time, temperature, and demulsifier concentration on the demulsification efficiency have been evaluated. According to the results, this demulsifier can be used as an effective demulsifier for both chemical and magnetic demulsification and displayed a demulsification efficiency of 100 % at 50 °C without a magnet and 90 % at 20 °C with a magnet. The chemical demulsification efficiency of Fe3O4 nanoparticles was investigated and it showed lower DE compared to magnetic cellulose nanocrystals. The recyclability tests of the demulsifier indicated that magnetic cellulose nanocrystals can be used up to 4 times. Finally, the demulsification mechanism and interfacial tension measurements revealed that this demulsifier reduced the interfacial tension between water and crude oil and increased the water droplet sizes.

Synthesis and demulsification mechanism of an ionic liquid with four hydrophobic branches and four ionic centers

Stable emulsions can have numerous negative impacts on both the oil industry and the environment. This study focuses on the synthesis of two ionic liquids (via. PPBD and PPBH) with four hydrophobic branches and four ionic centers that can effectively treat oil-water emulsions at a low temperature of 40 °C. Their chemical structure was explored using Fourier-transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance hydrogen spectra (1H NMR). The effect of temperature, PPBD and PPBH concentration, oil-water ratio, salinity and pH value on the demulsification efficiency (DE) of W/O emulsion was studied detailly and several commercial demulsifiers were also used for comparison. Results revealed that by adding 250 mg/L of PPBH in an E30 emulsion and leaving it for 120 min at 40 °C, the DE could reach 96.34%. Meanwhile, in an E30 emulsion (oil-water mass ratio of 3:7) with 250 mg/L of PPBD, the DE of 95.23% could be obtained at 40 °C for 360 min. Especially, the DE of PPBH could reach 100% in an E70 emulsion (oil-water mass ratio of 7:3) at the same conditions. Additionally, the demulsifier (PPBH) exhibited excellent salt resistance and outperformed some commonly used commercial demulsifiers. Several methods were utilized to investigate the potential demulsification mechanism, including measuring interfacial tension (IFT), three-phase contact angle (CA), droplet contact time, zeta potential, and observing samples under optical microscopy.

A perspective of microemulsions in critical metal separation and recovery: Implications for potential application of CO2-responsive microemulsions

Since the discovery of microemulsions, they have attracted great attention due to its unique properties, such as ultra-low interfacial tension and nanoscale droplets. During the past several decades, microemulsions have shown unparalleled advantages in critical metal separation and recovery, e.g., high separation rate, high recovery efficiency, and good selectivity. Therefore, fundamental understandings of such metal recovery behavior are of great significance for the continuous development of microemulsion-based separation technology in this field. Herein, we first systematically reviewed the application of regular microemulsion in the separation and recovery process of critical metals focusing on their separation mechanisms. Then, we summarized the recent progress of CO2-responsive microemulsions and highlighted their potential application in critical metal separation and recovery, aiming to provide some insights into alleviating the difficulties in demulsification during the stripping stage using regular microemulsions. In this section, the latest development of CO2-responsive microemulsions is introduced, and the relationship between their composition, microstructure and macroscopic properties is discussed. Discussion and future perspectives are provided highlighting the design of new microemulsions and potential application of CO2-responsive microemulsions for metal separation and recovery in the future.

In-depth potential mechanism of combined demulsification pretreatments (isopropanol ultrasonic pretreatments and Ca2+ flow additions) during aqueous enzymatic extractions of Camellia oils

Emulsification is the practical limitation of aqueous enzymatic extractions of Camellia oils. This study aimed to investigate the influence and demulsification mechanisms of isopropanol ultrasonic pretreatments and Ca²⁺ additions on aqueous enzymatic extractions of Camellia oils. Combining isopropanol ultrasonic pretreatments with Ca²⁺ flow additions obtained the highest free oil recovery (78.03 %) and lowest emulsion content (1.5 %). Results indicated that the superior demulsification performance originated from the decrease in emulsion stabilities and formations. First, demulsification pretreatments reduced the oil (14.69 %) and solid (13.21 %) fractions in emulsions to decrease the stability of as-formed emulsions. Meanwhile, isopropanol ultrasonic pretreatments extracted tea saponins (0.38 mg/mL) and polysaccharides (0.23 mg/mL), while Ca²⁺ combined with protein isolates (5.82 mg/mL), tea saponins (7.48 mg/mL) and polysaccharides (0.78 mg/mL) to form precipitates and reduce emulsion formation. This work could promote the practical application of aqueous enzymatic extractions of Camellia oils and enlighten the rise of advanced demulsification pretreatments.

Novel polymer nanoparticles with core-shell structure for breaking asphaltenes-stabilized W/O and O/W emulsions

HYPOTHESIS

The removal of stable water-in-oil (W/O) or oil-in-water (O/W) emulsions has been a challenging issue in chemical and oil industry for decades. Traditional demulsifiers were generally designed specifically for treating either W/O or O/W emulsions. A demulsifier that is effective for treating both types of emulsions will be highly desired.

EXPERIMENTS

Novel polymer nanoparticles (PBM@PDM) was synthesized as a demulsifier for treating both W/O and O/W emulsions prepared by toluene, water, and asphaltenes. The morphology and chemical composition of synthesized PBM@PDM were characterized. Demulsification performance and interaction mechanisms including interfacial tension, interfacial pressure, surface charge properties and surface forces were systematically studied.

FINDINGS

PBM@PDM could immediately prompt the coalescence of water droplets upon addition and effectively release the water in asphaltenes-stabilized W/O emulsion. In addition, PBM@PDM successfully destabilized asphaltenes-stabilized O/W emulsion. Not only could PBM@PDM substitute the asphaltenes adsorbed at the water-toluene interface, but they could also dominate the water-toluene interfacial pressure in competition with asphaltenes. The steric repulsion between interfacial asphaltene films could be suppressed in the presence of PBM@PDM. Surface charges significantly influenced the stability of asphaltenes-stabilized O/W emulsion. This work provides useful insights into the interaction mechanisms of asphaltene-stabilized W/O and O/W emulsions.

Application of combined granular media with opposite wettability for demulsification of oily wastewater by microchannel filter

Oil-water separation with high efficiency and low energy consumption is a tremendous challenge in the green treatment of oily wastewater. In this paper, a novel filtration method with combined granular media for collaborative removal emulsified oil and suspended solids (SS) was proposed, followed by the exploration of demulsification feasibility and oil removal mechanism. The effect of the operation and structural parameters of the filter bed on oil separation performance was thoroughly investigated, and its feasibility for raw oily wastewater treatment was also explored. A remarkable demulsification performance was observed with the combined granular media filter, and a balance of separation efficiency and pressure drop in the emulsified oily wastewater filtration was also achieved subsequently. Effective oil droplet capture and coalescence were observed with a high speed camera system, and pore clogging could be avoided in combined media. The optimal parameters of the combined media filter (CMF) were concluded to be a combined media ratio of 1:1, a superficial velocity of 0.20 m min^-1, and a bed porosity of 58.1%. The average oil and suspended solids concentrations in raw oily wastewater was decreased to 8.4 mg/L and 23.3 mg/L during the pilot-scale operation, which indicated that the novel filter composed of combined media had better performance in collaboratively removing oil and SS, even in the period of fluctuating influent parameters. It is believed that a novel and efficient oil removal method, especially including of emulsified oil removal was provided, which also shows great potential and value for the green treatment of industrial oily wastewater.

Preparation of a demulsifier for oily wastewater using thorn fir bark as raw materials via a hydrothermal and solvent-free amination route

In current work, a TB-EDA demulsifier for disposing oily wastewater was prepared using thorn fir bark (TB) as starting materials via a hydrothermal and solvent-free amination route. Field emission scanning electron microscope (FE-SEM), energy dispersive X-ray spectrometer (EDS), and Fourier transform infrared spectroscope (FT-IR) were employed to characterize the TB-EDA demulsifier. Three-phase contact angle (CA), interfacial activity, formation of interfacial film (FIF), coalescence time of droplets (CTD), dynamic interfacial tension (IFT), and Zeta potential were carried out to study the possible demulsification mechanism. Bottle test was performed to investigate the effect of the TB-EDA dosage, salinity, and pH value on the demulsification performance at room temperature. Light transmittance (D_L) and oil removal rate (D_R) of separated water were 94.7% and 97.2%, respectively, with 100 mg/L of TB-EDA demulsifier in oily wastewater at room temperature. In addition, the TB-EDA demulsifier has an excellent salt tolerance even at the salinity of 50,000 mg/L. The corresponding D_L and D_R could reach 99.8% and 99.9%, respectively.

Nano-modification of carboxylated polyether for enhanced room temperature demulsification of oil-water emulsions: Synthesis, performance and mechanisms

Oil-water emulsions separation is frequently required considering the production and environmental issues. Herein, a nano-modification strategy has been proposed for carboxylated poly(propylene oxide)-poly(ethylene oxide) block polyether (mANP) using epoxy-functionalized magnetic nanoparticles (Fe₃O₄@SiO₂-GPTMS), achieving the construction of a highly efficient demulsifier (M-mANP). Bottle tests showed that M-mANP could separate over 98.5% of water from the asphaltene-stabilized water-in-oil (W/O) emulsion at mANP concentration of 150 ppm within 2 min at room temperature. The demulsification efficiency for crude oil-in-water emulsion was nearly 100%. According to interfacial tension and wettability tests, the nano-modification endows M-mANP with good amphiphilicity and high interfacial activity, which enables M-mANP to rapidly adsorb at the oil-water interface. Molecular dynamics simulation shows that abundant oxygen-containing groups (hydroxyl, ether bond, ester and carboxyl groups, Fe-O and Si-O bond) in M-mANP could strengthen the interaction with water, facilitating the replacement of asphaltene molecules at interfacial film. Observation of demulsification process by microscope reveals that the nano-size promotes M-mANP to bridge small dispersed droplets, enhancing the flocculation and coalescence of droplets. The nano-modified carboxylated polyether with outstanding demulsification ability shows a promising application for the treatment of different oil-water emulsions.

Development of advanced oil/water separation technologies to enhance the effectiveness of mechanical oil recovery operations at sea: Potential and challenges

Mechanical oil recovery (i.e., booming and skimming) is the most common tool for oil spill response. The recovered fluid generated from skimming processes may contain a considerable proportion of water (10 % ~ 70 %). As a result of regulatory prohibition on the discharge of contaminated waters at sea, vessels and/or storage barges must make frequent trips to shore for oil-water waste disposal. This practice can be time- consuming thus reduces the overall efficiency and capacity of oil recovery. One potential solution is on-site oil-water separation and disposal of water fraction at sea. However, currently available decanting processes may have limited oil/water separation capabilities, especially in the presence of oil-water emulsion, which is inevitable in mechanical oil recovery. The decanted water may not meet the discharge standards and cause severe ecotoxicological impacts. This paper therefore comprehensively reviews the principles and progress in oil/water separation, demulsification, and on-site treatment technologies, investigates their applicability on decanting at sea, and discusses the ecotoxicity of decanted water in the marine environment. The outputs provide the fundamental and practical knowledge on decanting and help enhance response effectiveness and consequently reducing the environmental impacts of oil spills.

Diethylenetriamine modified biological waste for disposing oily wastewater

Oily wastewater produced in the process of oil extraction has a potential threat to the environment. In this paper, diethylenetriamine was used to modify rice straw powder (RSP) by a solvent-free strategy, and the obtained product (AM-RSP) was utilized to dispose oily wastewater. AM-RSP was characterized by Field emission scanning electron microscope (FE-SEM), energy dispersive spectrometer (EDS), Fourier transform infrared spectroscope (FT-IR) and BET. The factors affecting the demulsification performance (DP) such as dosage, salinity and pH value were detailly investigated. The results indicated that light transmittance (E_T) and oil removal rate (E_R) of separated water could reach 93.5% and 96.5%, respectively, within 40 min with 150 mg/L of AM-RSP at room temperature. Also, AM-RSP had a good salt resistance. In addition, three-phase contact angle (TCA), formation of interfacial film, interfacial activity, dynamic interfacial tension (IFT), coalescence time of droplets and zeta potential were adopted to probe the demulsification mechanism.

Molecular dynamics simulation on water/oil interface with model asphaltene subjected to electric field

HYPOTHESIS

The droplet-medium interfaces of petroleum emulsions are often stabilized by the indigenous surface-active compounds (e.g., asphaltenes), causing undesired issues. While demulsification by electric field is a promising technique, fundamental study on the droplet-medium interface influenced by electric field is limited. Molecular dynamics (MD) simulations are expected to provide microscopic insights into the nano-scaled water/oil interface.

METHODS

MD simulations are conducted to study the adsorption of model asphaltene molecules (represented by N-(1-hexylheptyl)-N'-(5-carboxylicpentyl) perylene-3,4,9,10-tetracarboxylic bisimide (C5Pe)) on a water-toluene interface under various strengths of electric field. The adsorption amount and structural feature of C5Pe molecules at water-toluene interface are investigated, and the effects of electric field and salt are discussed.

FINDINGS

C5Pe molecules tend to adsorb on the water-oil interface. As the electric field strength increases, the adsorption amount first slightly increases (or remains constant) and then decreases. The electric field disrupts the compact π-π stacking between C5Pe molecules and increases their mobility, causing a dispersed distribution of the molecules with a wide range of orientations relative to the interface. Within the studied range, the addition of salt ions appears to stabilize the interface at high electric field. These results provide useful insights into the mechanism and feasibility of demulsification under electric field.

Rapid and efficient oil removal from O/W emulsions by hydrophobic porous polystyrene microspheres embedded with hydrophilic surface micro-regions

Inspired by Namib Desert beetle's back which is patterned with different wetting properties, hydrophobic porous polystyrene microspheres embedded with hydrophilic surface micro-regions (HPHs) were designed and fabricated by the radical copolymerization in the W₁/O/W₂ double Pickering emulsions with high internal water phase. The synergistic effect of the hydrophobic surface and the hydrophilic surface micro-regions results in HPHs exhibiting superior performances for separating both surfactant-free and surfactant-stabilized O/W emulsions. After 60 s hand-shaking, the oil was absorbed and stored within HPHs which could be separated from the water using a 600-mesh sieve, and the TOC values of purified water could be reduced to 2.06 ± 0.06-67.38 ± 2.02 ppm when the initial oil content was 1 vol%. Meanwhile, HPHs could be recovered and reused through a simple treatment. The excellent oil removal efficiency was kept even after 50 cycles. High oil removal efficiency, general applicability, easy operation and excellent recyclability endow HPHs with great potential for practical applications. And this work provides a facile and general way to prepare porous polymer microspheres with wettability contrast surfaces.

Piezoelectricity induced by pulsed hydraulic pressure enables in situ membrane demulsification and oil/water separation

Recovering oil from oily wastewater is not only for economic gains but also for mitigating environmental pollution. However, demulsification of oil droplets stabilized with surfactants is challenging because of their low surface energy. Although the widely used oil/water separation membrane technologies based on size screening have attracted considerable attention in the past few decades, they are incapable of demulsification of stabilized oil emulsions and the membrane concentrates often require post-processing. Herein, the piezoelectric ceramic membrane (PCM), which can respond to the inherent transmembrane pressure in the pressure-driven membrane processes, was employed to transform hydraulic pressure pulses into electroactive responses to in situ demulsification. The pulsed transmembrane pressure on the PCM results in the generation of considerable rapid voltage oscillations over 3.2 V and a locally high electric field intensity of 7.2 × 10⁷ V/m, which is capable of electrocoalescence with no additional stimuli or high voltage devices. Negative dielectrophoresis (DEP) force occurred in this membrane process and repelled the large size of oil after demulsification away from the PCM surface, ensuring continuous membrane demulsification and oil/water separation. Overall, PCM provides a further opportunity to develop an environmentally friendly and energy-saving electroresponsive membrane technology for practical applications in wastewater treatment.

A superwetting stainless steel mesh with Janus surface charges for efficient emulsion separation

Design of charged materials for demulsification of ionic surfactant-stabilized oil-in-water emulsions is emerging in recent years. Herein, a superwetting stainless steel mesh with Janus surface charges (Janus SSM) was prepared by respectively brush-coating polyethyleneimine/aminated carbon nanotubes (PEI/CNTs-NH₂) coating and polyacrylic acid (PAA) coating on its two sides. Two demulsification mechanisms, i.e., electrostatic attraction-repulsion and electrostatic repulsion-attraction based on the synergism of two oppositely charged sides were proposed. Combined with the superwettability and optimized pore size, the Janus SSM can successfully be used to demulsify, coalesce and separate emulsions. In detail, the Janus SSM exhibited separation efficiencies of up to 99.29%, 97.12% for SDS- and DTAC-stabilized oil-in-water emulsions respectively under the electrostatic attraction-repulsion mechanism, and up to 97.10%, 98.57% under the electrostatic repulsion-attraction mechanism. The results indicated that the electrostatic attraction-repulsion mechanism proposed in this study is conductive to achieving higher efficiency in emulsion separation. Furthermore, excellent durability extend the operation life of Janus SSM. This Janus SSM, which combines opposite charges on its two sides, may advance the development of charged materials for emulsion separation.

Demulsification of oily wastewater using a nano carbon black modified with polyethyleneimine

In this work, nano carbon black was modified with polyethyleneimine (CB-PEI) under an ultrasonic field. The obtained product was used as a demulsifier to break oily wastewater. Morphology, structure, and chemical composition of CB-PEI were systematically analyzed. Bottle test was carried out to evaluate the influence of dosage, pH value and salinity on the demulsification efficiency of the emulsion. The results showed that the light transmittance of water phase (TSW) after the demulsification was 79.1% and corresponding oil removal rate (ORR) could reach up to 99.4% with 60 mg/L of CB-PEI at ambient temperature for 30 min. In addition, the possible demulsification mechanism was explored by dynamic interface tension (IFT), elasticity modulus, wettability, self-assemble of interfacial membrane, zeta potential and micrograph analysis. It indicated that CB-PEI had an appropriate amphiphilicity and good interfacial activity, which could improve it quickly transfer to the oil-water interface and result in the oil-water separation. The current work provides a simple method to prepare a demulsifier with excellent performance, so it has a good application prospect for the treatment of oil-water emulsions.

High positively charged Fe3O4 nanocomposites for efficient and recyclable demulsification of hexadecane-water micro-emulsion

Oily wastewater not only causes major environmental issues, but also threatens human health. Magnetic nanoparticles (MNPs) are an attractively alternative commercial demulsifiers for their recyclability and high surface area. The wettability and surface charge of magnetic materials are significant factors in oily wastewater treatment. However, the specific influence of surface charge on the demulsification performance has not been rigorously investigated. Herein, a series of MNPs coated by dimethyl-diallyl-ammonium chloride (PDDA) and fulvic acid (FA) (Fe₃O₄/FA/PDDA) with different surface positive charges were synthesized by adjusting the PDDA concentrations and applied in demulsification of hexadecane-water micro-emulsion. The oil-water separation efficiency (Es) was enhanced gradually with increasing the surface positive charge of demulsifiers. Derjaguin-Landau-Verwey-Overbeek (DLVO) theory confirmed that with increasing surface positive potential, the electrostatic attraction between demulsifiers and oil droplets increased, and thus, Es increased. In addition, the superior Es of Fe₃O₄/FA MNPs for hexadecyl trimethyl ammonium bromide (CTAB)-stabilized micro-emulsions and Fe₃O₄/FA/PDDA MNPs for sodium dodecyl sulfate (SDS)-stabilized micro-emulsions further confirmed that electrostatic force was critical in demulsification. The high positively charged Fe₃O₄/FA/PDDA MNPs can be used as an efficient and recyclable demulsifier for hexadecane-water micro-emulsion. This study provides a theoretical basis for designing demulsifiers.

Recyclable amine-functionalized carbon nanotubes for the separation of oily wastewater

In this work, a CNTs-NH₂ demulsifier was prepared by grafting ethylenediamine on the surface of carbon nanotubes to break oily wastewater. The physicochemical and interfacial properties of CNTs-NH₂ were characterized and analyzed. It showed that CNTs-NH₂ had an eminent amphipathicity and high interfacial activity, which allows it to sharply migrates to the interface and effectively interacts with interfacial film by the combined action of π-π interaction and electrostatic attraction. The demulsification tests exhibited that CNTs-NH₂ could effectively remove emulsified oil from the oily wastewater. It could be used at acidic and neutral conditions, and high salinity. Moreover, it could be recycled and still maintained its interfacial activity, thusly vastly enhancing the application scope. The light transmittance was up to 88.1% and the corresponding oil removal rate was 99.2% with 100 mg/L of CNTs-NH₂ for 30 min. The oil removal rate of CNTs-NH₂ remained above 97.8% after 6 cycles. This work provides a deep understanding on the design of demulsifier and its demulsification mechanism.

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.

Recent developments, challenges, and prospects of ultrasound-assisted oil technologies

There has been consistent drive towards research and innovation in oil production technologies in order to achieve improved effectiveness and efficiency in their operation. This drive has resulted in breakthrough in technologies such as the application of ultrasound (US) in demulsification and enhanced oil recovery (EOR), and usage of high-volume hydraulic fracturing and special horizontal well for shale oil and gas extraction. These can be observed in the increment in the number of commercial oil technologies such as EOR projects that rose from 237 in 1996 to 375 in 2017. This sustained expansion in EOR resulted in their total oil production rising from 1.5 million barrels per day in 2005 to 2.3 million barrels per day in 2020. And this is predicted to increase to about 4.7 million barrels per day in 2040, which represent about 4% of total production. Consequently, in this review, the developments in the utilization of US either as standalone or integrated with other technologies in EOR and dehydration of water in oil emulsions were analyzed. The studies include the optimization of fluid and US properties in EOR and demulsification. Reports on the treatment of formation damage resulting from inorganic salts, organic scales, drilling fluid plugs, condensate, paraffin wax and colloidal particle with US-assisted EOR were also highlighted. Moreover, the mechanisms were examined in order to gain insightful understanding and to aid research investigations in these areas. Technologies such as US assisted green demulsification, high intensity focused ultrasound, and potential pathways in field studies were assessed for their feasibilities. It is essential to evaluate these technologies due to the significant accrued benefits in them. The usage of green demulsifiers such as deep eutectic solvents, ionic liquids and bio-demulsifiers has promising future outlook and US could enhance their technical advancement. HiFU has been applied successfully in clinical research and developments in this area can potentiality improve demulsification and interfacial studies (fluid-fluid and solid-fluid interactions). As regards field studies, there is need to increase actual well investigations because present reports have few on-site measurements with most studies being in laboratory scale. Furthermore, there is need for more detailed modeling of these technologies as it would assist in conserving resources, saving research time and fast-tracking oil production. Additional evaluative studies of conditions such as the usage of Raschig rings, crude oil salinity and high temperature which have improved demulsification of crude oil emulsions should be pursued.

Treatment of oil-based drilling cuttings using the demulsification separation-Fenton oxidation method

In this study, demulsification separation-Fenton oxidation technology was employed as a combined technology to treat total petroleum hydrocarbons (TPH) in oil-based drill cuttings (OBDC). Batch experiments were carried out to optimize the technology parameter. Under the optimal condition, 70% and 51% TPH removal rate was obtained for demulsification technology and Fenton oxidation technology, respectively. Eighty-five percent of TPH removal rate was obtained using combination technology of demulsification separation and Fenton oxidation. Multiple characterizations were used to analyze the physical and chemical properties of treated OBDC. The result of XRD pattern indicated the combination technology had no obvious effect for structure phase of OBDC. The results of FTIR, GC-MS, TG-DTG and SEM were used to characterize the treated OBDC. This paper provides an efficient and feasible combined technology for OBDC treatment, which expands a new strategy for the removal of TPH from solid waste.

Enhanced oil droplet aggregation and demulsification by increasing electric field in electrocoagulation

Electrocoagulation (EC) is an efficient technology for removing oil-in-water (O/W) emulsions. However, the role of the electric field in EC for demulsification remains unclear and an obstacle for improving reactor design and operation. Herein, demulsification and oil removal performance by EC under different electric field conditions were investigated. Increasing the EC electric field intensity was beneficial for oil removal, and tandem EC had a higher electric field intensity than parallel EC under the same current density. When the current density was 0.67 mA cm^-2, the chemical oxygen demand (COD) removal rates of tandem EC and parallel EC were 1 136.47 and 745.99 g COD kWh^-1, respectively. Oil droplets were polarized by the electric field, and then aligned and aggregated parallel to the direction of the electric field. Increasing electric field intensity accelerated the aggregation of oil droplets, as verified by physical fluid simulation. Furthermore, results showed a higher Al³⁺ dosage and larger electric field intensity in EC with increasing current density, which was conducive to oil droplet demulsification. These findings provide insight into and a theoretical basis for improving oil removal by EC processes.

Nanoscale silica-coated graphene oxide and its demulsifying performance in water-in-oil and oil-in-water emulsions

In current work, GO@SiO₂ nanocomposite was prepared by coating nanoscale silica onto graphene oxide (GO). GO@SiO₂ was characterized with scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (IF-IR). Additionally, the demulsifying performance of GO@SiO₂ was investigated by bottle test. The results showed that GO@SiO₂ had a good demulsifying performance in both oil-in-water (O/W) and water-in-oil (W/O) emulsions. When the concentration of GO@SiO₂ was 200 ppm in the O/W emulsion, the optimal light transmittance of aqueous phase (LTA) and corresponding oil removal rate (ORR) at room temperature could reach 86.9% and 99.48%, respectively. Also, GO@SiO₂ had an excellent salt tolerance under acidic condition. Furthermore, GO@SiO₂ also could demulsify the W/O emulsion, and the efficiency at 70 °C could reach 80.5% when the concentration was 400 ppm.

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.

Effective remediation of petrochemical originated pollutants using engineered materials with multifunctional entities

The highly robust, effective, and sustainable remediation of hydrocarbon-contaminated wastewater matrices, which is mainly generated from petroleum and related petrochemical industries, is of supreme interest. Owing to the notable presence of suspended solids, oil, and grease, organic matter, highly toxic elements, high salts, and recalcitrant chemicals, crude oil emulsions, and hydrocarbon-contaminated wastewater are considered a potential threat to the environments, animals, plants, and humans. To effectively tackle this challenging issue, magnetic hybrid materials assembled at nano- and micro-scale with unique structural, chemical, and functional entities are considered robust candidates for demulsification purposes. The current research era on magnetic materials has superwettability, leading to an effective system of superwettability, which is vibrant and promising. The wettability of magnetic and magnetic hybrid materials explaining the theme of superhydrophobicity and superhydrophilicity under the liquid. Herein, we reviewed the applications of magnetic nanoparticles (MNPs) as effective demulsifiers. The demulsifier wettability, dose, pH, salinity, and surface morphology of compelling, magnetic nanoparticles are the main hidden factors in effective demulsifiers. There is a comprehensive discussion on the reuse and recyclability of MNPs after oil, water separation. Furthermore, the main challenges, coupled with the magnetic nanoparticles in the effective separation of emulsions, are intensified in detail. This review will compare the current literature and the utilization of MNPs for the demulsification of oil and water emulsions. This is envisioned that the MNPs would be critical in the petroleum and petrochemical industry to effectively eliminate water from a crude oil emulsion.

A review of the interfacial stability mechanism of aging oily sludge: Heavy components, inorganic particles, and their synergism

Oily sludge is widely produced in the processes of petroleum exploitation, storage, transportation, and refining, and becomes more stable during aging. The interfacial stability of aging oily sludge hinders the recovery and disposal of oil resources. This review summarizes the interfacial film stability of aging oily sludge, which occurs through the formation of viscoelastic and rigid bilayer interfacial films between heavy components (asphaltenes and resins) and inorganic particles. The bilayer interfacial films enhance interfacial film strength and hinder the aggregation of droplets, contributing to the formation of a stable and high-viscosity oil-water-solid three-phase mixture. Recent demulsification technologies for reducing the stability of interfacial films have been classified as follows: removing heavy components, changing asphaltene aggregate structure, and reducing inorganic particle content. More efficient demulsification technologies are expected to be developed by deeply analyzing the microstructure and interfacial properties of asphaltenes and resins, as well as comprehensively studying the complex interactions among various components. This review constructs a bridge between the stability mechanism and the corresponding destabilization methods, which would promote future studies in aging oily sludge treatment.

Emulsions in external electric fields

Water is co-produced with crude oils, generally in the form of water-in-crude oil emulsions. The oil and water phases need to be separated before export. Separation is performed in gravity separators with the addition of chemical demulsifiers and, sometimes, with the application of an electric field by using an electrocoalescer. The present article reviews several aspects of electrocoalescence by considering the effect of the electric field from the molecular to a macroscopic scale: the oil-water interface, single drop effects, two drop interactions, and finally emulsions at laboratory scales. Experimental results together with Dissipative Particle Dynamics (DPD) simulation results are presented. The review begins with water-oil interface under an electric field and followed by single drop electrohydrodynamics. The electric field is shown to influence the adsorption of crude oil indigenous surface-active components (asphaltenes) due to the electrohydrodynamic (EHD) flows. The interactions between two droplets in the presence of electric field and the factors governing the drop-drop coalescence are discussed in detail. DPD simulations help to elucidate thin film breakup during (electro)-coalescence of two water droplets, where the oil film has drained out to nanometer thickness. The film is comprised of surfactant and demulsifier molecules, and the simulations capture the pores formation in the film when a DC field is applied. The results demonstrate influence of the molecular structure of the surfactant and demulsifier, and their interactions. The subsequent section describes experimental techniques to assess the resolution of crude oil emulsions at the laboratory scale. The focus is on low-field Nuclear Magnetic Resonance (LF-NMR) which allows a determination of various emulsion features such as the droplet size distribution (DSD) and the brine profile (variation of the concentration of water with the height of the emulsion sample) and their evolution with time. Application of the technique in emulsion treatment involving chemical demulsifiers and electric field is presented. The review concludes with description of commercial industrial electrocoalecers such as the Vessel Internal Electrostatic Coalescer (VIEC) and the Compact Electrostatic Coalescer (CEC).

Application of coagulation/flocculation in oily wastewater treatment: A review

Volumes of oily wastewater are inevitably generated by every walk of life. The removal of oil particles from oil-contaminated wastewater which is characterized as huge amounts, intricate composition, and great threats to human health and the ecological environment is a research hotspot in water treatment fields. Due to high treatment costs and undesirable treatment efficiencies, oily wastewater treatment remains a topical and urgent issue. At present, coagulation/flocculation as an indispensable oily wastewater treatment technology receives much attention because it is very well established, economical, practical and relatively efficient. The influencing factors of oil wastewater treatment by coagulation/flocculation have also been summarized in-depth, like dosage, pH, etc. In consideration of its complex composition and treatment difficulty, this paper will also compare the treatment effects of different coagulants/flocculants used alone and combined effects in oily wastewater treatment: inorganic coagulants, organic synthetic polymeric flocculants, natural flocculants and modified polymeric flocculants. Additionally, in this review, the mechanisms of removing oily substance by coagulation/flocculation are emphasized. Given strict emission standards and the refractory nature of oily wastewater, the combination process with coagulation/flocculation, such as electrocoagulation, coagulation-membrane filtration hybrid process, and coagulation/flocculation-flotation can present better application potential and are discussed in this review. To provide a proper choice in practical application, the operating cost of coagulation and several conventional technologies are also compared. Finally, the existing challenges in the treatment of oily wastewater by coagulation are analyzed, and the feasible research direction is proposed.

Photocatalytic demulsification of oil/water emulsions containing nonionic surfactant

Separation of oil-water (OW) emulsions is investigated using a photocatalytic demulsification approach. Experiments were conducted using two types of photocatalysts, namely, ZnO and TiO₂. The emulsion samples were prepared with oil to water ratios of 1:3, 1:1, and 3:1 and using nonionic surfactant Tween 20 as an emulsifier. The demulsification efficiency was determined using a direct time varying phase separation measurement, while dynamic light scattering (DLS) and microscope imaging (MI) were used to determine the change in emulsion droplets size. The investigation results showed that all the emulsions were destabilized and separated within 30-90 min with demulsification efficiency that ranged from 38 to 90%. On the other hand, untreated control samples remained stable with no phase separation for more than 24 h. For most of the studied experimental conditions, TiO₂ nanoparticles gave better demulsification results than ZnO. Modeling of the batch demulsification kinetics for both systems agreed satisfactorily with the experimental measurements. This could allow its further extension towards design of continuous processes for potential implementation in treatment of industrial oily wastewaters.

A durable superwetting clusters-inlayed mesh with high efficiency and flux for emulsion separation

How to rapidly and efficiently separate surfactant-stabilized emulsions has been a great challenge for oil/water separation materials. In this work, a durable superwetting copper mesh with high efficiency and flux for gravity-driven emulsion separation was fabricated by subtly inlaying polydopamine/polyethyleneimine@aminated carbon nanotubes (PDA/PEI@CNTs-NH₂) clusters in the mesh pores. The porous clusters with abundant cationic groups render the mesh with superwettability, submicron permeation channels and positive charges, so as to achieve strong demulsification ability. Based on the superwettability and the strong demulsification ability, the PDA/PEI@CNTs-NH₂ clusters-inlayed copper mesh (PPC-CM) exhibited high separation efficiency of over 99.5% for various anionic surfactant-stabilized oil-in-water emulsions. Meanwhile, the permeation flux of PPC-CM solely driven by gravity is as high as 3946.3 L m^-2 h^-1. The strong demulsification ability and high permeation flux of the superwetting mesh are due to the synergistic action of charge-screening effect of -NH³⁺ and size-sieving effect of optimized pore size. Furthermore, the resultant mesh exhibited excellent durability that it could resist serious physical abrasion and chemical corrosion. Especially the mesh after repeated separation can recover its positive charge by a simple acid treatment. These excellent performances highlight the superwetting mesh a promising potential for sustainable separation of highly stabilized oil/water emulsions.

Applying ultrasonic fields to separate water contained in medium-gravity crude oil emulsions and determining crude oil adhesion coefficients

Separating produced water is a key part of production processing for most crude oils. It is required for quality reasons, and to avoid unnecessary transportation costs and prevent pipework corrosion rates caused by soluble salts present in the water. A complicating factor is that water is often present in crude oil in the form of emulsions. Experiments were performed to evaluate the performance of ultrasonic fields in demulsifying crude oil emulsions using novel pipe-form equipment. A horn-type piezoelectric ultrasonic transducer with a frequency of 20 kHz and power ranging from 80 W to 1000 W was used for experimental purposes. The influences of the intensity of ultrasonic fields, ultrasonic irradiation time, and the initial water content of crude oils were evaluated to establish the rate of water segregation from oil. The experiments applied ultrasonic-field intensities of 0.25 W/cm³, 0.5 W/cm³, 0.75 W/cm³ and 1 W/cm³ to synthetic emulsions with 10%, 15%, 20%, and 25% of the water in crude oil. Crude oil demulsification occurred for each ultrasonic field intensity tested for all the samples tested. Function β involving adhesion coefficients was expressed in terms of wave-field intensity and initial concentration of water in each of the three crude oil samples tested. The experiments demonstrated that despite the absence of any chemical demulsifier involved, water separation caused by applying ultrasonic fields was effective and occurred rapidly. As the intensity of the ultrasonic field applied increased, the amount of water segregated from crude oil also increased. Subjected to constant field intensity, higher initial water cuts (up to 15% or so) in the crude oil samples and higher ultrasonic irradiation times, resulted in greater segregation of water from crude oil in percentage terms. However, in samples with initial water cuts of 20+% long irradiation times (~5 min), resulted in a decline in water separation compared to 2-min tests. Ultrasonic field treatments offer commercially-viable and environmentally-friendly alternatives to treatments using chemical demulsifiers as they reduce desalination requirements of wastewater.

Recent advances in applications of power ultrasound for petroleum industry

Power ultrasound, as an emerging green technology has received increasing attention of the petroleum industry. The physical and chemical effects of the periodic oscillation and implosion of acoustic cavitation bubbles can be employed to perform a variety of functions. Herein, the mechanisms and effects of acoustic cavitation are presented. In addition, the applications of power ultrasound in the petroleum industry are discussed in detail, including enhanced oil recovery, oil sand extraction, demulsification, viscosity reduction, oily wastewater treatment and oily sludge treatment. From the perspective of industrial background, key issue and resolution mechanism, current applications and future development of power ultrasound are discussed. In addition, the effects of acoustic parameters on treatment efficiency, such as frequency, acoustic intensity and treatment time are analyzed. Finally, the challenges and outlook for industrial application of power ultrasound are discussed.

Fate of phospholipids during aqueous extraction processing of peanut and effect of demulsification treatments on oil-phosphorus-content

PC (phosphatidylcholine), PE (phosphatidylethanolamine), PI (phosphatidylinositol), and PA (phosphatidic acid) in 9 peanut matrices obtained during the AEP (aqueous extraction processing) of peanut were quantified employing HPLC-ELSD analysis in this study. Phosphorus contents of crude oils obtained from different demulsification treatments were also investigated. Decantation had a larger effect than grinding in terms of phospholipids loss due to alkaline-hydrolysis, indicating this processing step was vital for the manipulation of phospholipids levels remained in oil. Over 80% of initial phospholipids were lost during AEP and only 19.8% of initial phospholipids ended up in cream, skim and sediment phase. 52.55% of the remained phospholipids trapped in cream phase. Just 22.16-32.61 mg/kg phosphorus content could be detected in crude oils, which indicated the separation of phospholipids from the cream phase into aqueous medium. Degumming was not essential in AEP of peanut and the waste generated after demulsification could be a source of phospholipids.

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.

Electro-demulsification of water-in-oil suspensions enhanced with implementing various additives

A huge amount of various oily suspensions that frequently display properties of stable emulsions are produced per day in upstream and downstream petroleum industries. As this waste is considered potentially harmful to the environment, their management and disposal require particular attention. While current treatment processes, such as partial water removal via the separation of phases by centrifuging result in decreased waste volumes for disposal, a significant volume of water and oil remains trapped in the form of water-in-oil emulsion. Therefore, the electrokinetic method for oil-water separation came into consideration for the improvement of the quality and volume of separated products. This paper discusses the impacts of additives, namely, ferric chloride, alum, cationic polymer, clay, and a mixture of clay and cationic polymer on the electrokinetic treatment of suspensions. The tests were conducted at a lab scale using an array of steel electrodes and low voltage. The objective of this study was to observe the impact of voltage gradients on electro-demulsification, in conjunction with employing additives into the separation and recovery of water, light, and heavy oil. An optimal recovery of light oil by 28%-52% in addition to heavy oil and water in the presence of ferric chloride under a constant voltage gradient of 1 V/cm, was achieved. Furthermore, the same system revealed an excellent clarity of extracted water. The results from this study can be implemented at a larger scale in upstream and downstream petroleum industries.

Research on ultrasound-assisted demulsification/dehydration for crude oil

Crude oil demulsification and dehydration are important links in the process of crude oil exploitation, transportation, and refining. In recent years, with the development of crude oil exploitation, the content of colloid and asphaltene in crude oil has been increasing, and the properties of crude oil emulsion have become more stable. In addition, the development and application of oil recovery technology and the use of a large number of oilfield chemicals have made the composition of crude oil more complicated. The water content and salt content of oil produced fluid increase year by year, which aggravates the task of crude oil dehydration and desalination. Therefore, it is particularly important to study the demulsification and dehydration of crude oil. In this paper. Research on ultrasound-assisted demulsification/dehydration for crude oil in investigated. Results indicate that the demulsification effect varies with the increase of ultrasonic radiation time, but the difference is not significant; with the increase of temperature, the effect of ultrasonic on the demulsification of crude oil emulsion is decreased, or the advantages of ultrasonic can be fully displayed only at low temperature; ultrasonic power has a critical value, when it is lower than this critical value, ultrasonic wave acts as demulsifying agent, and with the increase of power, dehydration rate of the crude oil emulsion increases; when higher than the critical value, the separated oil and water can be re-emulsified; ultrasonic demulsification can both shorten settling time and reduce the amount of demulsifier; ultrasound is suitable for demulsification and dehydration of crude oil emulsions with high water content. Results also prove that chemical demulsifier has a better effect for crude oil demulsification /dehydration than that of ultrasonic treatment alone. In addition, recent progress on ultrasonic demulsification equipment is introduced. The purpose of this paper is to offer equipment and technical support for crude oil demulsification/ dehydration.

CO2-responsive surfactants with tunable switching pH

HYPOTHESIS

One of the major challenges in applying CO₂-responsive surfactants concerns their tunable switchability and robustness under operating conditions. We hypothesize that combining monoethanolamine (MEA) with long-chain fatty acids (LCFAs) of variable chain lengths through electrostatic attraction could develop a series of CO₂-responsive surfactants with tunable switching pH.

EXPERIMENTS

The tunability of switching pH for this group of surfactants was demonstrated by in situ probing of the CO₂-responsive characteristics at the oil/water interface using dynamic interfacial tension (IFT) measurements. Two protocols were applied to distinguish interfacial response and solution response. The key importance of interfacial response was demonstrated by two essential applications of CO₂-responsive surfactants: demulsification of stable emulsions, and alternation of the interfacial properties of ultra-heavy crude oil-water interfaces.

FINDINGS

The switching pH of the CO₂-responsive surfactants was controlled by the hydrocarbon chain length of LCFAs. More importantly, their switching behaviour was found to be different at the interface and in the bulk solution, which is attributed to the enhanced molecular interactions at the interface. Since most applications require surfactants to be switched at the interface, it is thereby most appropriate to determine the switching pH through their interfacial responses.

Medium-chain triglyceride/water Pickering emulsion stabilized by phosphatidylcholine-kaolinite for encapsulation and controlled release of curcumin

Pickering emulsions have received widespread attention for encapsulating lipophilic guests in the biomedical and food fields. However, control of the stabilities and demulsification of Pickering emulsions to allow the release of encapsulated species remains a challenge in gastrointestinal conditions. In this work, phosphatidylcholine-kaolinite was prepared by modification of natural kaolinite with phosphatidylcholine and was used as an emulsifier to stabilize medium-chain triglyceride (MCT)/water Pickering emulsions for encapsulating curcumin, a natural antioxidant drug. Simulated gastric and intestinal digestion and a cell uptake assay were implemented for the curcumin-loaded MCT/water Pickering emulsion to study its demulsification and the bioavailability of curcumin. The results revealed that the wettability of phosphatidylcholine-kaolinite could be tailored by controlling the modification temperature so that it could control the emulsion stability. The prepared phosphatidylcholine-kaolinite, with a three-phase contact angle of 123°, was an optimal emulsifier for the enhanced stabilization of the MCT/water Pickering emulsion, especially in the presence of gastric acid. The phosphatidylcholine-kaolinite distributed at the water-oil interface and formed a dense shell structure on the surfaces of the emulsion droplets, controlling the demulsification efficiency to release the encapsulated curcumin. Only 18.9% of the curcumin was released in the simulated gastric conditions after 120 min of digestion due to the demulsification of the MCT/water Pickering emulsion, while it was completely released after 150 min of digestion in simulated intestinal conditions, as expected. This Pickering emulsion stabilized by phosphatidylcholine-kaolinite is a promising delivery system for lipophilic foods or drugs to enhance their bioavailability.

Comparative transcriptomic analysis revealed the key pathways responsible for organic sulfur removal by thermophilic bacterium Geobacillus thermoglucosidasius W-2

Biodesulfurization is a promising method to desulfurize sulfur-containing compounds in oil with its unique advantages, such as environment-friendly treatments and moderate reaction conditions. In this study, a thermophilic bacterium Geobacillus thermoglucosidasius W-2 was reported to show nearly 40% and 55% desulfurization rates on heavy oil with 2.81% and 0.46% initial total sulfur content, respectively. Subsequently, comparative transcriptome analysis indicated that several possible key desulfurization-related genes of this strain were found to be differentially up-regulated induced by benzothiophene and dibenzothiophene, respectively. These desulfurization-related genes were considered to conduct key step to convert organic sulfur to inorganic sulfur. Moreover, the characterization of thermophilic alkanesulfonate monooxygenase systems SsuD₁/SsuE₁ and SsuD₂/SsuE₂ revealed that the enzymes exhibit considerable thermal and pH stability and wide substrates applicability. These enzymes probably endowed the strain W-2 with the ability to desulfurize oil and eliminate the sulfur-containing surfactants. Thus, this study provides novel alkanesulfonate monooxygenase systems that have the application potential for heavy oil biodesulfurization, oil demulsification and other biocatalytic processes.

Enhanced demulsification from aqueous media by using magnetic chitosan-based flocculant

A series of quaternized chitosan (QC)-grafted magnetic nanoparticles (MNPs) were successfully synthesized for demulsification from aqueous environments. Fe₃O₄ MNPs were synthesized by using a coprecipitation method, followed by surface coating with silica and aminopropyl to form a surface for further grafting of QC molecular chains. The synthetic magnetic flocculants were characterized by various technologies and their demulsification performances were evaluated in detail as a function of dosage, QC grafting ratio (G_q), pH and magnetic field. Results showed that pH did not significantly affect oil-water separation performance and MNPs with high G_q exhibited enhanced separation efficiency. The separation capacity was estimated to be >105 mg of diesel oil/mg of magnetic flocculant. Recycling experiment indicated the magnetic flocculant could be recycled up to at least 7 cycles at various pH levels. The grafted QC layer endowed the hybrid MNPs with permanent positive surface charges, thus allowing them to flocculate negatively charged oil droplets via electrostatic patching. The magnetic field could not only accelerate the separation of resulting flocs, but also remove the MNPs-coated dispersed oil droplets. In conclusion, QC-grafted MNPs provide a potentially new technique for developing environmentally friendly and highly efficient magnetic flocculant for practical demulsification applications.

Research on the static experiment of super heavy crude oil demulsification and dehydration using ultrasonic wave and audible sound wave at high temperatures

In this paper, the static experiment of super heavy crude oil demulsification and dehydration using ultrasonic irradiation at high temperatures is carried out. How the all factors, such as ultrasonic frequency, sound intensity, ultrasonic power, ultrasonic treatment time, sedimentation time, temperature and water ratio, affect ultrasonic crude oil demulsification and dehydration are summarized though this experiment. In addition, recent progress on ultrasonic demulsification equipment in China are reviewed. The purpose of this paper is to provide equipment and technical support for the extensive application of the technique of ultrasonic demulsification and dehydration.

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.

Experimental study on evaluation and optimization of tilt angle of parallel-plate electrodes using electrocoagulation device for oily water demulsification

Tilt angle of parallel-plate electrodes (APE) is very important as it improves the economy of diffusion controlled Electrocoagulation (EC) processes. This study aimed to evaluate and optimize APE of a self-made EC device including integrally rotary electrodes, at a fixed current density of 120 Am^-2. The APEs investigated in this study were selected at 0°, 30°, 45°, 60°, 90°, and a special value (α_(d)) which was defined as a special orientation of electrode when the upper end of anode and the lower end of cathode is in a line vertical to the bottom of reactor. Experiments were conducted to determine the optimum APE for demulsification process using four evaluation indexes, as: oil removal efficiency in the center between electrodes; energy consumption and Al consumption, and besides, a novel universal evaluation index named as evenness index of oil removal efficiency employed to fully reflect distribution characteristics of demulsification efficiency. At a given plate spacing of 4 cm, the optimal APE was found to be α_(d) because of its potential of enhancing the mass transfer process within whole EC reactor without addition, external mechanical stirring energy, and finally the four evaluation indexed are 97.07%, 0.11 g Al g^-1 oil, 2.99 kwhkg^-1 oil, 99.97% and 99.97%, respectively.

Effect of ultrasonic frequency on separation of water from heavy crude oil emulsion using ultrasonic baths

In this work, a comprehensive study was performed for the evaluation of ultrasound (US) frequency for demulsification of crude oil emulsions. Experiments were performed using ultrasonic baths operating at the following frequencies: 25, 35, 45, 130, 582, 862 and 1146kHz. Synthetic water-in-oil emulsions with 12%, 35% and 50% of water and medians of droplet size distribution (DSD, D(0.5)) of 5, 10 and 25μm were prepared using a heavy crude oil (API density of 19). Crude oil demulsification was achieved at frequencies in the range of 25-45kHz for all tested emulsions. When frequencies higher than 45kHz were applied, no changes in the characteristics of the crude oil emulsions were observed. Demulsification efficiencies of about 65% were achieved at a frequency of 45kHz after 15min of US application (emulsions with original water content of 50% and D(0.5)=10μm). An important aspect is that no addition of chemical demulsifiers was performed, and the demulsification efficiency was considered high, taking into account that the results were obtained using a non-conventional crude oil. Contrary to the normal application of low-frequency US that has been used for emulsification, the proposed approach seems to be a promising technology for water removal from crude oil emulsions.

Dewatering of floated oily sludge by treatment with rhamnolipid

Oily sludge dewatering is practically needed prior to sludge treatments. However, the conventional use of physical treatments with or without chemical conditionings presented poor feasibility in industrial applications due to either poor cost-efficiency or lacking environmental friendliness. In this paper, biosurfactant rhamnolipid was for the first time applied for dewatering of oily sludge. Rhamnolipid treatments under the concentration of 300-1000 mg/L, pH of 5-7 and temperature of 10-60 °C could directly separate 50-80% of water from the stable oily sludge. And both mono-rhamnolipid and di-rhamnolipid were identified to be of equivalent dewatering ability, which is closely related to their equivalent performance in breaking the emulsified oil droplets. Demulsification was found to be involved in settling water from oily sludge. Furthermore, the effectiveness of rhamnolipid was further demonstrated at pilot scale (1000 L) treatment of oily sludge. After pilot treatment, the settled water with residual oil of 10 mg/L and soluble COD of about 800 mg/L could be directly effluxed into the biotreatment system while the concentrated oil sludge with a reduced volume by 60-80% can be pumped into coking tower, achieving completely harmless treatment. It seems that rhamnolipid as dewatering agent was of great prospects in the industrial dewatering of oily sludge.