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Rice protein isolate (RPI) has been receiving increasing attention from the food industry due to its performance as an emulsifier. However, it is possible to enlarge its field of applications through enzymatic hydrolysis. Therefore, this work aimed to investigate the effects of the controlled enzymatic hydrolysis (degree of hydrolysis DH as 2, 6, and 10%) using Flavourzyme on the physicochemical properties of rice protein and to identify the minimum concentration of these hydrolysates (0.5, 1.0, and 1.5%) to form and stabilize oil/water emulsion. The physicochemical, interfacial tension (IT), and surface characteristics of RPI and their hydrolysates (RPH) were determined. Even at a lower protein concentration (1.0%), protein hydrolysate presented lower IT when compared with RPI at a higher protein concentration (1.5%). The interfacial tension decreased from 17.6 mN/m to 9.9 mN/m when RPI was hydrolyzed. Moreover, enzymatic hydrolysis (DH 6 and 10%) enhanced the protein solubility by almost 20% over a pH range of 3-11. The improved amphiphilic property of RPH, supported by the results of IT and solubility, was confirmed by the higher emulsion stability indicated by the Turbiscan and emulsion stability indexes. Emulsions stabilized by RPH (DH 6% and 10%) at lower protein concentrations (1%) exhibited better physical stability than RPI at higher protein concentrations (1.5%). In this work, we verified the minimum concentration of rice protein hydrolysate required to form and stabilize oil-in-water (O/W) emulsions.

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The oil extracted from baru (Dipteryx alata Vog.) seeds is in bioactive compounds and it presents potential to be used in food and cosmetic industries. Therefore, this study aims to provide insights into the stability of baru oil-in-water (O/W) nanoemulsions. For this purpose, the effects of the ionic strength (0, 100 and 200 mM), pH (6, 7 and 8), and storage time (28 days) on the kinetic stability of these colloidal dispersions were evaluated. The nanoemulsions were characterized in terms of interfacial properties, rheology, zeta potential (ζ), average droplet diameter, polydispersity index (PDI), microstructure, and creaming index. In general, for samples, the equilibrium interfacial tension ranged from 1.21 to 3.4 mN.m-1, and the interfacial layer presented an elastic behavior with low dilatational viscoelasticity. Results show that the nanoemulsions present a Newtonian flow behavior, with a viscosity ranging from 1.99 to 2.39 mPa.s. The nanoemulsions presented an average diameter of 237-315 nm with a low polydispersity index (<0.39), and a ζ-potential ranging from 39.4 to 50.3 mV after 28 days of storage at 25 °C. The results obtained for the ζ-potential suggest strong electrostatic repulsions between the droplets, which is an indicative of relative kinetic stability. In fact, macroscopically, all the nanoemulsions were relatively stable after 28 days of storage, except the nanoemulsions added with NaCl. Nanoemulsions produced with baru oil present a great potential to be used in the food, cosmetic, and pharmaceutical industries.

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The objective of this study is to evaluate the role of nanoparticles with different chemical structures in completion fluids (CF) in providing a positive dual effect for well stimulation and clay swelling damage inhibition. Six types of commercial (C) or synthesized (S) nanoparticles have been incorporated into a commercial completion fluid. Doses varied between 100 and 500 mg·L-1. CF-nanoparticles were evaluated by fluid-fluid, fluid-nanoparticle, and fluid-rock interactions. The adsorption isotherms show different degrees of affinity, which impacts on the reduction of the interfacial tension between the CF and the reservoir fluids. Fluid-fluid interactions based on interfacial tension (IFT) measurements suggest that positively charged nanoparticles exhibit high IFT reductions. Based on contact angle measurements, fluid-rock interactions suggest that ZnO-S, SiO2-C, SiO2-S, and ZrO2 can adequately promote water-wet rock surfaces compared with other nanomaterials. According to the capillary number, ZnO-S and MgO-S have a higher capacity to reduce both interfacial and surface restrictions for crude oil production, suggesting that completion fluid with nanoparticles (NanoCF) can function as a stimulation agent. The clay swelling inhibition test in the presence of ZnO-S-CTAB and MgO-S-CTAB nanoparticles showed a 28.6% decrease in plastic viscosity (PV), indicating a reduction in clay swelling. The results indicate that a high-clay environment can meet the completion fluid's requirements. They also indicate that the degree of clay swelling inhibition of the nanoparticles depends on their chemical nature and dosage. Finally, displacement tests revealed that CF with nanoparticles increased the oil linear displacement efficiency.

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Research reports reveal the importance of applying various substances to enhance extra-heavy crude oil pipeline transportation. During the crude oil conduction process, shearing occurs in the equipment and pipe accessories, producing a water-in-crude emulsion associated with forming a rigid film by adsorbing natural surfactant molecules in the droplets water, leading to increased Viscosity. This study presents the effect of a flow enhancer (FE) on the behavior of the Viscosity of an extra heavy crude oil (EHCO) and in emulsions formed with 5% and 10% water (W). The results revealed the effectiveness of the 1%, 3%, and 5% flow enhancer in lowering the Viscosity and presenting a Newtonian flow behavior which will help reduce the cost of heat treatment during the transportation of crude oil through the pipeline.

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Soap applications for cleaning and personal care have been used for more than 4000 years, dating back to the pharaonic period, and have widely proliferated with the appearance of synthetic surfactants a century ago. Synthetic surfactants used to make macro-micro-nano-emulsions and foams are used in laundry and detergency, cosmetics and pharmaceuticals, food conditioning, emulsified paints, explosives, enhanced oil recovery, wastewater treatment, etc. The introduction of a multivariable approach such as the normalized hydrophilic-lipophilic deviation (HLD N) and of specific structures, tailored with an intramolecular extension to increase solubilization (the so-called extended surfactants), makes it possible to improve the results and performance in surfactant-oil-water systems and their applications. This article aims to present an up-to-date overview of extended surfactants. We first present an introduction regarding physicochemical formulation and its relationship with performance. The second part deals with the importance of HLD N to make a straightforward classification according to the type of surfactants and how formulation parameters can be used to understand the need for an extension of the molecule reach into the oil and water phases. Then, extended surfactant characteristics and strategies to increase performance are outlined. Finally, two specific applications, i.e., drilling fluids and crude oil dewatering, are described.

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This article presents a study of the interfacial properties of oil-in-water emulsions containing sugar esters and polysaccharides. Sucrose fatty acid esters were synthesized using immobilized Candida antarctica lipase B. A yield of 53.4% was obtained using 2-methyl-2-butanol and 1:3 M ratio of sucrose:stearic acid. Equilibrium surface tension was 45 mN/m and low critical micellar concentration (CMC) value was obtained (ca. 10 mg/mL), characteristic of non-ionic surfactant. The interfacial properties of mixtures of sucrose esters and polysaccharides, at the oil-water interface were determined using a pendant drop tensiometer. Addition of polysaccharides increased the interfacial tension. Studies of interfacial viscoelasticity showed that the films were predominantly elastic. The presence of polysaccharides in emulsions resulted in flocculated droplets. All the emulsions presented great stability along 28 days with no creaming formation.

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The primary objective of this study is to develop a novel experimental nanofluid based on surfactant-nanoparticle-brine tuning, subsequently evaluate its performance in the laboratory under reservoir conditions, then upscale the design for a field trial of the nanotechnology-enhanced surfactant injection process. Two different mixtures of commercial anionic surfactants (SA and SB) were characterized by their critical micelle concentration (CMC), density, and Fourier transform infrared (FTIR) spectra. Two types of commercial nanoparticles (CNA and CNB) were utilized, and they were characterized by SBET, FTIR spectra, hydrodynamic mean sizes (dp50), isoelectric points (pHIEP), and functional groups. The evaluation of both surfactant-nanoparticle systems demonstrated that the best performance was obtained with a total dissolved solid (TDS) of 0.75% with the SA surfactant and the CNA nanoparticles. A nanofluid formulation with 100 mg·L-1 of CNA provided suitable interfacial tension (IFT) values between 0.18 and 0.15 mN·m-1 for a surfactant dosage range of 750-1000 mg·L-1. Results obtained from adsorption tests indicated that the surfactant adsorption on the rock would be reduced by at least 40% under static and dynamic conditions due to nanoparticle addition. Moreover, during core flooding tests, it was observed that the recovery factor was increased by 22% for the nanofluid usage in contrast with a 17% increase with only the use of the surfactant. These results are related to the estimated capillary number of 3 × 10-5, 3 × 10-4, and 5 × 10-4 for the brine, the surfactant, and the nanofluid, respectively, as well as to the reduction in the surfactant adsorption on the rock which enhances the efficiency of the process. The field trial application was performed with the same nanofluid formulation in the two different injection patterns of a Colombian oil field and represented the first application worldwide of nanoparticles/nanofluids in enhanced oil recovery (EOR) processes. The cumulative incremental oil production was nearly 30,035 Bbls for both injection patterns by May 19, 2020. The decline rate was estimated through an exponential model to be -0.104 month-1 before the intervention, to -0.016 month-1 after the nanofluid injection. The pilot was designed based on a production increment of 3.5%, which was successfully surpassed with this field test with an increment of 27.3%. This application is the first, worldwide, to demonstrate surfactant flooding assisted by nanotechnology in a chemical enhanced oil recovery (CEOR) process in a low interfacial tension region.

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The aim of this study is the evaluation of partially sulfonated polystyrene nanoparticles (SPSNP) efficiency as nanocarriers for a non-ionic surfactant, oleic acid diethanolamide (OADA), in the reduction of the surfactant losses and the increase of oil recovery. The synthesized oleic acid diethanolamide was characterized by FTIR, 1H NMR, 13C NMR, surface tension (γ = 36.6 mN·m-1, CMC = 3.13 × 10-4 M) and interfacial tension of mineral oil/OADA aqueous solutions (IFTeq = 0.07 mN·m-1). The nanoparticles (SPSNP) were obtained by emulsion polymerization of styrene, DVB and sodium 4-styrenesulfonate (St-S) in the presence of OADA aqueous solution and were characterized by FTIR and PCS. The results show that the presence of ionic groups in the polymer structure promoted a better nanoparticles suspensions' stability, smaller particles production and more pronounced IFT reduction. The SPSNP obtained with an OADA concentration twenty times its CMC and 0.012 mol % of St-S presented a particle size around 66 nm and can act as efficient nanocarriers decreasing the water/oil interfacial tension to low values (0.07 mN·m-1) along the time, when in contact with the oil. Transport and oil recovery tests of the nanocarriers systems in an unconsolidated sand porous medium test show that the SPSNP do inhibit surfactant adsorption onto sand particles surface and induced an increase of oil recovery of up to about 13% relative to the water flooding oil recovery, probably due to a synergistic effect between the nanoparticles and surfactant action at the water/oil interface.

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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.

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The interfacial tension between immiscible liquids is studied as a function of a model linear surfactant length and concentration using coarse-grained, dissipative particle dynamics numerical simulations. The adsorption isotherms obtained from the simulations are found to be in agreement with Langmuir's model. The reduction of the interfacial tension with increasing surfactant concentration is found to display some common characteristics for all the values of chain length modeled, with our predictions being in agreement with Szyszkowski's equation. Lastly, the critical micelle concentration is predicted for all surfactant lengths, finding exponentially decaying behavior, in agreement with Kleven's model. It is argued that these findings can be helpful guiding tools in the interpretation of available experiments and in the design of new ones with new surfactants and polymers.