Charge Neutralization Mechanism Research Articles

Cation valency in water-in-salt electrolytes alters the short- and long-range structure of the electrical double layer

Highly concentrated aqueous electrolytes (termed water-in-salt electrolytes, WiSEs) at solid-liquid interfaces are ubiquitous in myriad applications including biological signaling, electrosynthesis, and energy storage. This interface, known as the electrical double layer (EDL), has a different structure in WiSEs than in dilute electrolytes. Here, we investigate how divalent salts [zinc bis(trifluoromethylsulfonyl)imide, Zn(TFSI)2], as well as mixtures of mono- and divalent salts [lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) mixed with Zn(TFSI)2], affect the short- and long-range structure of the EDL under confinement using a multimodal combination of scattering, spectroscopy, and surface forces measurements. Raman spectroscopy of bulk electrolytes suggests that the cation is closely associated with the anion regardless of valency. Wide-angle X-ray scattering reveals that all bulk electrolytes form ion clusters; however, the clusters are suppressed with increasing concentration of the divalent ion. To probe the EDL under confinement, we use a Surface Forces Apparatus and demonstrate that the thickness of the adsorbed layer of ions at the interface grows with increasing divalent ion concentration. Multiple interfacial layers form following this adlayer; their thicknesses appear dependent on anion size, rather than cation. Importantly, all electrolytes exhibit very long electrostatic decay lengths that are insensitive to valency. It is likely that in the WiSE regime, electrostatic screening is mediated by the formation of ion clusters rather than individual well-solvated ions. This work contributes to understanding the structure and charge-neutralization mechanism in this class of electrolytes and the interfacial behavior of mixed-electrolyte systems encountered in electrochemistry and biology.

Enhanced Coagulation for Algae Removal Using Composite Al-Based Coagulants: Collaborative Optimization Mechanism of Aluminum Morphology

The main purpose of this paper was to reveal the effect of aluminum (Al)-based coagulants on enhanced coagulation for the removal of algae and the synergistic optimization mechanism among different Al species. The formation, breakage, and regrowth processes of algal coagulation flocs formed by a series of monomeric Al-based coagulants (Al2(SO4)3, Al13, and Al30), Al13/Al30 composite coagulant and poly(diallyldimethylammonium chloride)/Al13 (PDADMAC/Al13) composite coagulant were studied. Results indicated that Al13 mainly employed a charge neutralization mechanism, which was conducive to the destabilization of algae and the regeneration of flocs, while Al30 mainly employed a sweep flocculation mechanism, which was conducive to the formation of algae and the strength of flocs. Meanwhile, the charge neutralization was the main mechanism during the algae coagulation process because it could effectively remove the soluble microbial products (SMP) component in the extracellular organic matter (EOM). Therefore, Al13 could achieve a higher coagulation performance than other monomeric Al-based coagulants. The Al13/Al30 composite coagulant could make up for the deficiency of the sweep flocculation mechanism in Al13 and charge neutralization mechanism in Al30, and achieve the best synergistic optimization performance at Al13:Al30-7:3. Additionally, PDADMAC, as a polymer, could further enhance the charge neutralization ability of Al13 at low dosages and the sweep flocculation ability of Al13 at high dosages, respectively. However, an excessive dosage would lead to charge reversal and thus reduce the coagulation effect. Therefore, controlling the dosage was key when using Al-composite coagulants. The findings of our research could offer a certain theoretical foundation for the development of inorganic polymer flocculants.

Enhanced Coagulation for Algae Removal Using Composite Al-Based Coagulants: Collaborative Optimization Mechanism of Aluminum Morphology

The main purpose of this paper was to reveal the effect of aluminum (Al)-based coagulants on enhanced coagulation for the removal of algae and the synergistic optimization mechanism among different Al species. The formation, breakage, and regrowth processes of algal coagulation flocs formed by a series of monomeric Al-based coagulants (Al2(SO4)3, Al13, and Al30), Al13/Al30 composite coagulant and poly(diallyldimethylammonium chloride)/Al13 (PDADMAC/Al13) composite coagulant were studied. Results indicated that Al13 mainly employed a charge neutralization mechanism, which was conducive to the destabilization of algae and the regeneration of flocs, while Al30 mainly employed a sweep flocculation mechanism, which was conducive to the formation of algae and the strength of flocs. Meanwhile, the charge neutralization was the main mechanism during the algae coagulation process because it could effectively remove the soluble microbial products (SMP) component in the extracellular organic matter (EOM). Therefore, Al13 could achieve a higher coagulation performance than other monomeric Al-based coagulants. The Al13/Al30 composite coagulant could make up for the deficiency of the sweep flocculation mechanism in Al13 and charge neutralization mechanism in Al30, and achieve the best synergistic optimization performance at Al13:Al30-7:3. Additionally, PDADMAC, as a polymer, could further enhance the charge neutralization ability of Al13 at low dosages and the sweep flocculation ability of Al13 at high dosages, respectively. However, an excessive dosage would lead to charge reversal and thus reduce the coagulation effect. Therefore, controlling the dosage was key when using Al-composite coagulants. The findings of our research could offer a certain theoretical foundation for the development of inorganic polymer flocculants.

Exploration of Waste Rice Husk-Based Nano-Silica to Fortify Algal Biomass Harvesting with Charge Neutralization Mechanism

Exploration of Waste Rice Husk-Based Nano-Silica to Fortify Algal Biomass Harvesting with Charge Neutralization Mechanism

Charge neutralization and β-elimination cleavage mechanism of family 42 L-rhamnose-α-1,4-D-glucuronate lyase revealed using neutron crystallography

Gum arabic (GA) is widely used as an emulsion stabilizer and edible coating and consists of a complex carbohydrate moiety with a rhamnosyl-glucuronate group capping the non-reducing ends. Enzymes that can specifically cleave the glycosidic chains of GA and modify their properties are valuable for structural analysis and industrial application. Cryogenic X-ray crystal structure of GA-specific L-rhamnose-α-1,4-D-glucuronate lyase from Fusarium oxysporum (FoRham1), belonging to the polysaccharide lyase (PL) family 42, has been previously reported. To determine the specific reaction mechanism based on its hydrogen-containing enzyme structure, we performed joint X-ray/neutron crystallography of FoRham1. Large crystals were grown in the presence of L-rhamnose (a reaction product), and neutron and X-ray diffraction datasets were collected at room temperature at 1.80 and 1.25 Å resolutions, respectively. The active site contained L-rhamnose and acetate, the latter being a partial analog of glucuronate. Incomplete H/D exchange between Arg166 and acetate suggested that a strong salt-bridge interaction was maintained. Doubly deuterated His105 and deuterated Tyr150 supported the interaction between Arg166 and the acetate. The unique hydrogen-rich environment functions as a charge neutralizer for glucuronate and stabilizes the oxyanion intermediate. The NE2 atom of His85 was deprotonated and formed a hydrogen bond with the deuterated O1 hydroxy of L-rhamnose, indicating the function of His85 as the base/acid catalyst for bond cleavage via β-elimination. Asp83 functions as a pivot between the two catalytic histidine residues by bridging them. This His–His–Asp structural motif is conserved in the PL 24, 25, and 42 families.

Preparation, characterization and application of a composite bioflocculant.

Composite flocculant PAFS-PDM was prepared from Polymeric aluminium ferric sulphate (PAFS) and Poly (diallyl dimethyl ammonium chloride) (PDM) in this study. A bacterium was selected from the soil near the shale gas exploitation platform as a bioflocculant-producing bacterium, and polysaccharide was extracted and combined with PAFS-PDM to obtain composite bioflocculant (CBF) to treat shale gas fracturing flowback fluid. The prepared CBF was characterized and the results showed that the prepared PAFS-PDM contained aluminium-iron hydroxyl polymer, which was a cationic flocculant. By measuring the turbidity removal rate and chemical oxygen demand (COD) removal efficiency, the function mechanism of CBF on the shale gas fracturing flowback fluid was discussed. The results showed that CBF had a stable treatment effect on fracturing flowback fluid when the pH value was about 7.0. With the increase of dosage, the coagulation efficiency increased first and then decreased. When the dosage of the CBF was 2500 mg·L-1, the treatment effect of shale gas fracturing flowback fluid was the best, and COD removal rate reached 89.43%. Through Zeta potential analysis, it was concluded that one of the coagulation mechanisms was electrical neutralization. According to the characterization results, it could be concluded that both adsorption bridging and charge neutralization mechanisms played important roles in the treatment of shale gas fracturing flowback fluids.

Investigating the efficiency of oak powder as a new natural coagulant for eliminating polystyrene microplastics from aqueous solutions

Polystyrene (PS) is a commonly used plastic material in disposable containers. However, it readily breaks down into microplastic particles when exposed to water environments. In this research, oak powder was used as a natural, inexpensive, and eco-friendly coagulant. The present study aims to determine the effectiveness of oak powder in removing PS from aquatic environments. The Box-Behnken model (BBD) was used to determine the optimal conditions for removal. The removal efficiency was evaluated for various parameters including PS concentration (100–900 mg/L), pH (4–10), contact time (10–40 min), and oak dosage (100–400 mg/L). The maximum removal of PS microplastics (89.1%) was achieved by using an oak dose of 250 mg/L, a PS concentration of 900 mg/L, a contact time of 40 min, and a pH of 7. These results suggest that oak powder can effectively remove PS microplastics through surface adsorption and charge neutralization mechanisms, likely due to the presence of tannin compounds. Based on the results obtained, it has been found that the natural coagulant derived from oak has the potential to effectively compete with harmful chemical coagulants in removing microplastics from aqueous solutions.

The assessment of coagulation and flocculation performance and interpretation of mechanistic behavior of suspended particles aggregation by alum assisted by tapioca peel starch

The current study describes the synergistic action of a green starch flocculant extracted from agricultural waste coupled with aluminium sulphate to enhance coagulation and flocculation for surface water treatment. The coagulants and the flocs characteristics were analyzed to better understand the physicochemical properties and the underlying mechanisms of the treatment process. Several elements, including Cl and Ca were observed on the surface of the starch, and the presence of essential functional groups such as hydroxyl and carboxyl that help to promote flocculation function was detected. Superior performance was observed in the treatment using alum+TPS compared to the treatment using alum as a sole coagulant. Maximum turbidity and TSS removals of 90.32% and 88.89%, respectively, were attained within 10 min of settling time using the recommended alum-TPS dosage of 7.5–50 mg/L at pH 7. The flocs generated by the alum+TPS treatment exhibited distinguishable characteristics with bigger and highly compacted flocs matrix in which colloidal particles enmeshed within the flocs clusters. The combination use of alum+TPS showed the microflocs were initially formed by alum through the charge neutralization mechanism. The later addition of the starch into the suspension revealed that the bridging and sweep flocculation mechanism governs the flocculation process reflected through the shifting of FTIR bands that marked the formation of hydrogen bonding between the starch, alum and the suspended particles. Adding starch into the suspension undoubtedly provided effective entrapment and adsorption by larger-sized polymer, which promotes inter-colloidal particle bridging and subsequently improves the water clarity.

Use of PDMAEMA as a non-toxic synthetic flocculant for harvesting microalgae and evaluation of the influence of polymer size on flocculation behaviour

We synthesised a library of linear 2-(dimethylaminoethyl) methacrylate polymers (PDMAEMA) as an alternative to polyacrylamide flocculants and used them for flocculation of freshwater microalgae Chlorella vulgaris. The dose required to induce flocculation (17.2–23.5 mg L−1) was found to be independent of the molecular weight (MW) of the polymer. ζ-potential measurements indicated that flocculation occurred primarily through a charge neutralisation mechanism. Surface charge reversal of the microalgal-PDMAEMA particles and resulting dispersion restabilization was observed for high MW PDMAEMA, but not for low MW PDMAEMA. We hypothesized that charge reversal was a result of partial absorbance of long polymers to the cell surface, resulting in charged loops and tails that emerge from the cell surface. This was confirmed and visualized using AFM, which revealed an increase in surface roughness of cells when high MW PDMAEMA was added in high dose, but not when low MW PDMAEMA was used. Dispersion restabilization could be partially prevented by stepwise addition of the high MW PDMAEMA.

Surface properties of membrane materials and their role in cell adhesion and biofilm formation of microalgae

In this study, the effects of surface properties of membrane materials on microalgae cell adhesion and biofilm formation were investigated using Chlorella vulgaris and five different types of membrane materials under hydrodynamic conditions. The results suggest that the contact angle (hydrophobicity), surface free energy, and free energy of cohesion of membrane materials alone could not sufficiently elucidate the selectivity of microalgae cell adhesion and biofilm formation on membrane materials surfaces, and membrane surface roughness played a dominant role in controlling biofilm formation rate, under tested hydrodynamic conditions. A lower level of biofilm EPS production was generally associated with a larger amount of biofilm formation. The zeta potential of membrane materials could enhance initial microalgae cell adhesion and biofilm formation through salt bridging or charge neutralization mechanisms.

A quaternary ammonium salt grafted tannin-based flocculant boosts the conjugative transfer of plasmid-born antibiotic resistance genes: The nonnegligible side of their flocculation-sterilization properties

This study developed dual-function tannin-based flocculants, namely tannin-graft-acrylamide-diallyl dimethyl ammonium chloride (TGCC-A/TGCC-C), endowed with enhanced flocculation-sterilization properties. The impacts of these flocculants on proliferation and transformation of antibiotic resistance genes (ARGs) among bacteria during the flocculation-deposition process were examined. TGCC-A/TGCC-C exhibited remarkable flocculation capacities towards both Escherichia coli and Staphylococcus aureus, encompassing a logarithmic range of initial cell density (108–109 CFU/mL) and a broad pH spectrum (pH 2–11). The grafted quaternary ammonium salt groups played pivotal parts in flocculation through charge neutralization and bridging mechanisms, concurrently contributing to sterilization by disrupting cellular membranes. The correlation between flocculation and sterilization entails a sequential progression, where an excess of TGCC, initially employed for flocculation, is subsequently consumed for sterilization purposes. The frequencies of ARGs conjugative transfer were enhanced in bacterial flocs across all TGCC treatments, stemming from augmented bacterial aggregation and cell membrane permeability, elicited stress response, and up-regulated genes encoding plasmid transfer. These findings underscore the indispensable role of flocculation-sterilization effects in mediating the propagation of ARGs, consequently providing substantial support for the scientific evaluation of the environmental risks associated with flocculants in the context of ARGs dissemination during the treatment of raw water featuring high bacterial density.

The Utilization of Pectin as Natural Coagulant-Aid in Congo Red Dye Removal

Coagulation using inorganic compounds such as aluminum sulfate is commonly used in water-wastewater treatment. However, there are some drawbacks to its utilization, such as a significant decrease in the treated water’s pH, non-biodegradable sludge, and a potential negative impact on human mental health (dementia and Alzheimer's). The use of inorganic coagulants can be minimized with the addition of natural-based coagulant-aid such as pectin. In this study, Congo red solution, a model dye substance, was coagulated by varying the pH (3–7) using alum coagulant to determine the best pH for coagulation. At the best pH, pectin was introduced at various doses (0–30 mg/L), and subsequently various dye concentrations (50–100 mg/L). The effect of pectin as coagulant-aid was compared with aluminum sulfate and pectin only; with a response of %removal and sludge volume. It was found that the Congo red dye coagulation had the best %removal at pH 6 indicating a charge neutralization mechanism. The addition of 15 mg/L pectin at an aluminum sulfate dose of 30 mg/L resulted in 97.7% dye removal with a sludge volume of 14 mL/L at a Congo red concentration of 50 mg/L. This value is higher compared to those of aluminum sulfate and pectin only which gave 75.6 and 3.19% removals, respectively. Furthermore, the addition of pectin as a natural coagulant-aid could halve the sludge volume due to the formation of denser flocs. The results show a promising potential of pectin as a natural coagulant-aid in water-wastewater treatment.

Application of xanthan gum as coagulant-aid for decolorization of synthetic Congo red wastewater

In recent years, utilization of polysaccharides as natural coagulant and coagulant-aid has become a topic of interest, due to the nature of biopolymers that are renewable, biodegradable, and non-toxic. In this study, Congo red, as a model dye substance, was treated using polyaluminium chloride (PAC) as the main coagulant and xanthan gum as the coagulant aid. For this purpose, the effect of pH (3–9), xanthan gum dose (0.5–4 mg/L), and the initial concentration of Congo red dye (50–100 mg/L) to the dye removal and sludge volume were investigated. The outcome of this investigation indicates that the best pH for Congo red coagulation occurred at pH 3, due to the charge neutralization mechanism. The addition of coagulant-aid dose increases the %-removal and sludge volume until reaching the best coagulant-aid dose of 2 mg/L that results in a %-removal value of 93.81% and a sludge volume of 23.5 mL/L. Further addition of xanthan gum reduced the %-removal and sludge volume due to the inter-polymer force causing more difficult floc formation. The best initial concentration of dye occurred at a Congo red concentration of 50 mg/L, with a %-removal value of 93.81% with PAC (15 mg/L) and xanthan gum (2 mg/L) coagulants. This value is considerably higher than PAC and xanthan gum only which amounts to 81.16 and 7.18%, respectively. Based on these results, it is apparent that xanthan gum can positively contribute to dye coagulation while reducing the use of harmful inorganic coagulant.

A sustainable approach for industrial wastewater treatment using pomegranate seeds in flocculation-coagulation process: Optimization of COD and turbidity removal by response surface methodology (RSM)

In this study, we presented a sustainable approach for industrial wastewater treatment through flocculation-coagulation process by using pomegranate seed powder as a novel natural alternative to the conventional chemical flocculants and coagulants. Pomegranate seeds are non-toxic, safe, locally available and free of charge as food-waste. The performance of Pomegranate seeds in treatment of paper recycling wastewater (PRWW) was optimized using response surface methodology (RSM) in terms of pH, dosage and settling time. The ZP, FTIR, EDX, XRD, BET and SEM analyses were performed for characterization of the flocs and flocculation-coagulation mechanism. The maximum removals of 87 % and 98 % were achieved for chemical oxygen demand (COD) and turbidity, respectively, under the optimum condition of Pomegranate seed dosage of 2391.91 mg/L, pH of 10.37 and settling time of 25 min (R2 = 0.988). According to the ZP analysis, adding pomegranate seeds increases the ZP of the PRWW from −11.7 mV to an isoelectric point (ZP ~ 0 mV) which results in particles coagulation through charge neutralization mechanism. The characterization analyses revealed that pomegranate seeds contain polysaccharides, proteins and fatty acids compounds that enable particles flocculation via inter-particle bridging mechanism. The findings of this study proved that pomegranate seed powder can be considered a promising, environmentally friendly and effective coagulant-flocculant agent for industrial wastewater treatment.

Electrochemically and Ultrasonically-Enhanced Coagulation for Algae Removal

At the global level, the augmenting presence of harmful algae blooms constitutes important dares to water treatment plants (WTPs). In WTPs, coagulation remains the primary process of the applied procedure to treat algae-contaminated water. Such a chemical process influences the following techniques; thus, regulating coagulation parameters to eliminate algae at the maximum degree without provoking cell deterioration is more than crucial. This work aims to review coagulation-founded methods for algae elimination. First, investigations concentrating on algae elimination using the chemical process are discussed. The introduction presents the widespread algae encountered in the water treatment field. Then, habitually utilized experimental techniques and emerging methods in coagulation investigations are summarized with typical findings. Next, the newest expansions in improved algae elimination, launched by electrochemically and ultrasonically-enhanced coagulation, are discussed. Workable thoughts for applying coagulation to eliminate algae in WTPs are also debated. The paper finishes by defining restrictions and dares related to the present literature and suggesting trends for subsequent studies. The charge neutralization mechanism efficiently removes solubilized microcystins (MCs), and enhanced coagulation configuration is also found to be more efficient for their removal. However, considerations should be taken to avert that the acid introduction has no unwanted effect in killing algae treatment to avoid the solubilized MCs level elevation. If such techniques are well-optimized and controlled, both algae and solubilized MCs could be efficaciously removed by ultrasound-enhanced coagulation and electrocoagulation/electrooxidation.

Surface Chemical Groups of Flocs Are Key Factors for the Growth of Flocs in Sweep Coagulation: A Case Study of Surface Occupation by Humic Acid

Coagulation is one of the most common processes in water treatment. Charge neutralization and sweep flocculation are recognized as the primary coagulation mechanisms. However, in-depth understanding on floc growth, breakage, and regrowth is still unclear. In this study, the formation, breakage, and regrowth of alum flocs with humic acid (HA) added either before coagulant addition or during the floc breakage stage were investigated. The floc size continuously decreased with the increase in floc breakage events, and eventually, to a stable value. The floc growth was not affected by the addition of HA before coagulant addition. However, it was prevented as HA was added during the breakage stage, and the prevention extent increased with HA dose. Similar results were also found for natural organic matter (NOM) from real surface water. These results suggested that HA/NOM can cover the active site on the floc surface, and the coverage differed for fresh flocs (newly precipitated) and old flocs (after breakage), which, respectively, represent the case in conventional coagulation and sludge recirculation. Based on these findings, the illustration of floc growth, breakage, and regrowth processes was put forward. We concluded that the charge neutralization and sweep flocculation mechanisms only explained the possibility of flocs approaching each other; whether flocs can connect to each other depends on the activated functional groups on the floc surface. The results in this study revealed the underlying mechanism of “collision effectiveness” in coagulation, complementing the existing understanding of the coagulation process.

Structures of VWF tubules before and after concatemerization reveal a mechanism of disulfide bond exchange

Abstractvon Willebrand factor (VWF) is an adhesive glycoprotein that circulates in the blood as disulfide-linked concatemers and functions in primary hemostasis. The loss of long VWF concatemers is associated with the excessive bleeding of type 2A von Willebrand disease (VWD). Formation of the disulfide bonds that concatemerize VWF requires VWF to self-associate into helical tubules, yet how the helical tubules template intermolecular disulfide bonds is not known. Here, we report electron cryomicroscopy (cryo-EM) structures of VWF tubules before and after intermolecular disulfide bond formation. The structures provide evidence that VWF tubulates through a charge–neutralization mechanism and that the A1 domain enhances tubule length by crosslinking successive helical turns. In addition, the structures reveal disulfide states before and after disulfide bond-mediated concatemerization. The structures and proposed assembly mechanism provide a foundation to rationalize VWD-causing mutations.

Synthesis and characterization of a cationic dextran-based flocculant and its application in bacterial sedimentation

As a promising material in the field of wastewater treatment, polysaccharide-modified flocculants have received increasing attention due to their environmental friendliness. In this study, an efficient and environmentally friendly flocculant was synthesized using a graft copolymerization reaction of dextran and [2-(methacryloyloxy) ethyl] trimethylammonium chloride (METAC). The reaction conditions were optimized at 3 mol/mol METAC/dextran, 60 g/L dextran concentration, 3 h reaction time, 60 ℃ and pH 7. The results of elemental analysis, Fourier transform infrared (FTIR) spectroscopy, NMR hydrogen spectroscopy (1H NMR), X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA) and viscosity measurement confirmed that the graft copolymerization reaction was successful. When flocculating a kaolin suspension used as synthetic wastewater, the flocculant showed effective flocculation performance at a low dosage. The results indicate that this cationic polysaccharide flocculant removed 98.2% of the kaolin solid suspended particles. Investigation of the flocculation mechanism showed that the flocculation process consisted of charge neutralization, charge patching and adsorption bridging mechanisms. When flocculating an E. coli culture medium, this flocculant showed high efficiency under acidic, neutral and alkaline conditions. In addition, this flocculant can be easily biodegraded by the enzymatic method. As a biomaterial, this cationic dextran derivative can contribute to future treatment of industrial wastewater and harvesting of microbial cells.

Liquid-Liquid Extraction of the Eu(III) Cation by BTP Ligands into Ionic Liquids: Interfacial Features and Extraction Mechanisms Investigated by MD Simulations.

What happens at the ionic-liquid (IL)/water interface when the Eu3+ cation is complexed and extracted by bis(dimethyltriazinyl) pyridine "BTP" ligands has been investigated by molecular dynamics and potential of mean force simulations on the interface crossing by key species: neutral BTP, its protonated BTPH+ form, Eu3+, and the Eu(BTP)33+ complex. At both the [BMI][Tf2N]/water and [OMI][Tf2N]/water interfaces, neither BTP nor Eu(BTP)33+ are found to adsorb. The distribution of Eu(BTP)23+ and Eu(BTP)3+ precursors of Eu(BTP)33+, and of their nitrate adducts, implies the occurrence of a stepwise complexation process in the interfacial domain, however. The analysis of the ionic content of the bulk phases and of their interface before and after extraction highlights the role of charge buffering by interfacial IL cations and anions, by different amounts depending on the IL. Comparison of ILs with octanol as the oil phase reveals striking differences regarding the extraction efficiency, the affinity of Eu(BTP)33+ for the interface, the effects of added nitric acid and of counterions (NO3- vs Tf2N-), charge neutralization mechanisms, and the extent of "oil" heterogeneity. Extraction into octanol is suggested to proceed via adsorption at the surface of water pools, nanoemulsions, or droplets, with marked counterion effects.

An Experimental Study on Efficient Demulsification for Produced Emulsion in Alkaline/Surfactant/Polymer Flooding

Abstract Tertiary oil recovery technologies, for example, alkaline/surfactant/polymer (ASP) flooding, can enhance oil recovery as an important oil displacement technology noteworthy in the present oilfields. However, it is the fact that the produced emulsion droplets have strong electronegativity, which will lead to the destabilization of electric field and affect the dehydration effect in the process of electric dehydration. This article innovatively proposed an efficient demulsification scheme, which uses polyaluminum chloride (PAC) as a chemical regulator to control electric field destabilization through the charge neutralization mechanism and then introduces demulsifier to promote oil–water separation. Furthermore, the dehydration temperature, power supply mode, and electric field parameters are optimized so as to achieve superior dehydration effect of ASP flooding produced liquid. The results indicate that PAC as a chemical regulator by exerting charge neutralization and electrostatic adsorption mechanism could reduce the electronegativity of the emulsified system, decrease the peak current of dehydration, shorten the duration of peak current of dehydration, improve the response performance of the electric field, and increase dehydration rate in the ASP flooding dehydration process. When the demulsifier dosage is 100–120 mg/l, using the composite separation process with the dehydration temperature of 45–50 °C for the thermochemical separation stage and 60 °C in the electrochemical dehydration stage and AC–DC composite electric field or pulse electric field can achieve better dehydration effect. The investigations in this study will provide support and basis for the efficient treatment of ASP flooding produced emulsion.