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Miscible carbon dioxide (CO2) flooding is a well-established and promising enhanced oil recovery (EOR) technique whereby residual oil is recovered by mixing with injected CO2 gas. However, CO2, being very light and less viscous than reservoir crude oil, results in inefficient sweep efficiency. Extensive research is ongoing to improve CO2 mobility control such as the development and generation of CO2/water foams. The long-term stability of foam during the period of flooding is a known issue and must be considered during the design stage of any CO2 foam flooding project. The foam stability can be improved by adding surfactants as stabilizers, but surfactants generated foams have generally a shorter life because of an unstable interface. Furthermore, surfactants are prone to higher retention and chemical degradation in the porous media, particularly under harsh reservoir conditions. Research has shown that nanoparticles (NPs) can act as an excellent stabilizing agent for CO2/water foams owing to their surface chemistry and high adsorption energy. The foams generated using NPs are more stable and provide better mobility control compared to surfactant-stabilized foams. One limitation of using NPs as foam stabilizers is their colloidal stability which limits the use of low-cost NPs. Combining surfactants and NPs for CO2 foam stabilization is a novel approach and has gained interest among researchers in recent years. Surfactants improve the dispersion of NPs in the aqueous phase and minimize particle aggregation. NPs on the other hand create a stable barrier at the CO2/water interface with the help of surfactants, thus generating highly stable and viscous foams. This paper presents a comprehensive review of the basic principles and applications of stabilized CO2 foams. A brief overview of CO2 foam flooding is discussed first, followed by a review of standalone surfactant-stabilized and NPs-stabilized CO2/water foams. The application of hybrid surfactant-NPs stabilized CO2 foams is then presented and areas requiring further investigation are highlighted. This review provides an insight into a novel approach to stabilize CO2/water foams and the effectiveness of the method as proved by various studies.

In the work, the kinetics of the release of vitamin E and polyphyte oil from capsules was studied using synthetic and natural systems. The release of active ingredients was monitored on a Cary 50 Cons UV spectrophotometer equipped with CaryWinUV software. The kinetics of the release of vitamin E from capsules stabilized with sodium caseinate and then coated with chitosan shows a sustained prolonged release of 20% of vitamin E within 1 h, within 5 h about 45% is released, within 48 h about 80%. It was found that the efficiency of capsulation of vitamin E is higher than that of polyphyte oil, the release of vitamin E is more delayed and prolonged in comparison with polyphyte oil. The release of vitamin E from capsules stabilized with a synthetic system polymer-surfactant / vitamin E) chitosan) polystyrene sulfonate PSS was also investigated. It was determined that the release of vitamin E from capsules stabilized by a synthetic system (polymer-surfactant and coated with two layers of oppositely charged polyelectrolyte by the Layer-by-Layer method) is prolonged, within 1 h – 23% of vitamin E is released, 70% – within 12 h and 100% – within 80 h.

Viscoelastic surfactant (VES) fracturing fluids, with the advantages of low residues, complete gel breaking, and low formation damage, have received considerable attention in hydraulic fracturing t...

In polymer flooding process, the poor solubility of polymer and the wrap of incompletely dissolved polymer particles with heavy oil lead to the generation of complicated blockage, which seriously affects the normal production of wells. Therefore, how to fabricate an effective blockage removal agent is particularly important. Based on the blockage from Bohai Offshore Oilfield in China, a blockage removal agent composed of (0.5 wt% potassium persulfate + kerosene (the ratio of kerosene: blockage is 3:5)+0.3 wt% OP-10, the oil-water ratio is 1:9) was developed. The removal effect and mechanism were characterized by weight loss method and core test. Moreover, the emulsification property of the removal agent was also evaluated by microscopic appearance. The results showed that the blockage removal agent can be formulated as an O/W emulsion and had good stability for more than 72 h. Core test showed that the permeability had a significant improvement after injection of removal agent. The emulsion-type removal agent can demulsify after contact with the blockage, then the oil-soluble detergent as internal phase in emulsion can be released which contributes to the wash off of heavy oil. Accompanied with the polymer degradation by the oxidant, this agent realized the effective dissolution and removal of blockage.

The aim of this work was to investigate a possibility of preparing composite zein/natural resin (shellac and rosin) nanoparticles by antisolvent co–precipitation from their aqueous ethanol solutions. Influence of zein/resin mass ratio (1/0, 0.8/0.2, 0.5/0.5, 0.4/0.6 and 0/1) and pH (2–12) on particle size, d, and zeta potential, , of the prepared particles was studied. The functional properties of zein/rosin composite nanoparticles were evaluated by studying carvacrol encapsulation. It was shown that the antisolvent precipitation can be successfully used to prepare the shellac and rosin nanoparticles, as well as the composite zein/shellac and the zein/rosin nanoparticles. Colloidal properties, d and , of the obtained nanoparticles are influenced by the zein/ /resin mass ratio and the pH of nanoparticles’ dispersions. The isoelectric point of composite nanoparticles can be modulated by varying the zein/resin mass ratio. It was found that the zein/rosin nanoparticles are suitable for carvacrol encapsulation, where carvacrol release is enhanced by increasing the rosin share in the composite zein/rosin nanoparticles. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III 46010/3]

Responsive wormlike micelles (WLMs) consisted of cationic surfactants and organic-acids are fascinating due to their reversible molecular recognition properties. However, it is unknown how the structure of organic-acids alters the stimuli-responsiveness of WLMs systems. Herein, the peculiar nature of temperature-responsive behaviors in three WLMs systems were systematically investigated. These were manufactured by combining N-erucamidopropyl-N,N-dimethylamine (UC22AMPM) with isomers of organic-acids: o-phthalic acid (o-PA), m-phthalic acid (m-PA) and p-phthalic acid (p-PA) at molar ratio of 2:1 (named as o-EAPA, m-EAPA and p-EAPA respectively). The phase behaviors, macro- and micro-rheology, as well as the mechanism of temperature-responsiveness were explored by visual inspection, rheological and optical methods. The results showed that the three systems exhibited different responsiveness with increase of temperature. Among them, the viscosity and viscoelasticity of o-EAPA were gradually decreased with temperature increase from 30 °C to 90 °C. On the other hand, those of p-EAPA were firstly increased and subsequently decreased, exhibiting the highest viscosity during the heating process. This peculiar phenomenon was attributed to the hydrophilic difference of organic-acids isomers, leading to variations of micelle transitions upon temperature increase. This study is the first report of aromatic-acids isomers inducing different on temperature-responsiveness, and finding beneficial for the development of responsive WLMs for different applications.

Zein, a corn protein, is often used for preparing edible films and coatings. Since zein is insoluble in water, zein films and coatings are usually prepared by spraying or casting its aqueous ethanol solutions to a contact surface (Zsol films). However, the use of organic solvents in many food applications is unwanted. In this work, aqueous dispersions of zein nanoparticles were prepared by antisolvent precipitation from 90% v/v aqueous ethanol zein solutions. Zein films were then prepared by casting the dispersions in silicone molds and air–drying at 50 °C (Zdis films). The obtained films were characterized for morphology, FTIR analysis, mechanical, water barrier and optical properties, and were benchmarked against Zsol films. It was found that continuous zein films can be prepared out of aqueous dispersions of zein nanoparticles. Zdis films proved to have grainy morphology and higher surface roughness when compared to Zsol. Surface roughness of Zdis films was decreased when plasticizer was added. Water barrier properties of Zdis films were found to be comparable to Zsol films. No differences in mechanical properties were found between Zsol and Zdis film. Size of zein particles influenced morphology and optical properties of zein dispersion films.

For the past decades, long-term water flooding processes have led to water channeling in mature reservoirs, which is a severe problem in oilfields. The development of better plugging ability and cost-effective polymer gel is a key aspect for the control of excess water production. Research on polymer gel applicable in a heterogeneous reservoir to plug high permeable channels has been growing significantly as revealed by numerous published scientific papers. This review intends to discuss the polymer gel techniques from innovations to applications. The related difficulties and future prospects of polymer gels are also covered. Developments of polymer gels to resist temperature, early gel formation, synergistic mechanisms and influence of pH, high salinity are systematically emphasized. The review provides a basis to develop polymer gels for future applications in oilfields to meet harsh reservoir conditions. It will assist the researchers to further develop polymer gels to improve the oil recovery from mature reservoirs under economic conditions to meet the requirements of future oilfields.

Nowadays, the search for and development of new forms of materials with biocides is an actual problem of the modern science of nanosized materials due to the problem of microbiological contamination, which can be solved by using nanocontainers carrying biocides. Depending on the morphology of the nanocontainers and the filled active agents, it is possible to create coatings with specially designed self-healing functionality or multifunctional properties. The purpose of this work was to produce submicro-containers (SMCs) with a shell of SiO2 nanoparticles and a core of polymerized 3- (trimethoxysilyl) propyl methacrylate filled with 5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) in an oil in water (O/W) emulsion. The chemical nature of the individual components of the system and nano-capsules were investigated using NMR spectroscopy. The size and zeta potential of the SMCs were measured by a dynamic light scattering method (d = 170&ndash, 180 nm, polydispersity index PDI = 0.125 and zeta-potential = 55 mV), the morphology of their outer surface was determined using SEM. The results of NMR analysis showed that during the addition of the biocide into the SMCs, its chemical structure is retained, as is its activity. Minor changes in the chemical shifts of the 1H NMR spectra of the SMCs with DCOIT, as well as of the biocide itself, confirm the inclusion of DCOIT inside the SMCs.

The “graft onto” method is used to obtain the “stimuli-responsive water-soluble polymer” with low concentration, where 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and n-hydroxysulfosuccinimide sodium salt as catalyst and sodium polyacrylate as backbone chain. The molecular structure of the polymer is characterized by Nuclear Magnetic Resonance (1H NMR). The influence of temperature on polymer rheological properties and aggregation is studied by rheometer and fluorescence probe respectively. The results show that when the polymer concentration is higher than 1500 mg/L, the thickening properties can be controlled by diacetoneacrylamide, thermal-responsive monomer, NaCl and polymer concentration, where the apparent viscositymax/ viscositymin (ηmax/ηmin) changes from 18.3 to 39.4, from 2.6 to 45.5, from 9.3 to 36, from 7.8 to 36.9 respectively and the lower critical solution temperature (LCST) changes from 60 °C to 40 °C. The reason for the polymer with controllable thickening properties is that the thermal-responsive monomers change from hydrophilicity to hydrophobicity, thus forming aggregations. At this time, the polymer chains form network structures. Because of controllable thickening properties at low concentration, it has potential application prospects.

Microemulsion, because of its excellent interfacial tension reduction and solubilization properties, has wide range of applications in the petroleum industry, especially in improved oil recovery (IOR). Herein, the concept, types and formation mechanism of microemulsion were primarily introduced. Then, the preparation and characterization methods were illustrated. Additionally, several effect factors were elaborated specifically based on the composition of microemulsion. Finally, the application of microemulsion in IOR was addressed, including IOR mechanism analysis based on sweep efficiency and displacement efficiency, injection method (microemulsion flooding, in-situ microemulsion formation) and field tests. Furthermore, the current challenges and prospects of microemulsion on IOR were analyzed.

Chemical demulsifiers were widely applied for demulsification of crude oil emulsions which were generally formed with natural stabilizers during the extraction. Based on our previous study of the light crude oil emulsions stability, the demulsification performance of four classes of nonionic poly(ethylene oxide) poly(propylene oxide) copolymer demulsifiers and sodium dodecyl sulfate (SDS) as well as their dynamic demulsification process on the W/O light crude oil emulsion were analyzed by the multiple light scattering method. The demulsification mechanism of these demulsifiers were illuminated by the measurement of dynamic interfacial tension (IFT), dynamic interfacial viscoelasticity, rupture rate and microscopic changes of oil film by single droplet method. The results have shown that demulsification performance doesn’t depend on IFT, though effective demulsifiers could have a lower IFT around 1 mN/m. Multiple light scattering data and dynamic IFT clarified the demulsification process of efficient demulsifiers, quick diffusion and adsorption of demulsifiers, palpable change in interfacial property, droplet coalescence and sedimentation. The capacities of demulsifiers to penetrate into the interface and to decrease the interfacial viscoelasticity were the dominating demulsification mechanisms. The quantitative interpretation of multiple light scattering data associated with the dynamic IFT and interfacial viscoelasticity illuminated the demulsification mechanism of different demulsifiers. The rupture rate and dynamic rupture process of the oil film between the aqueous phases also vividly showed the differences in demulsification process. The nonionic demulsifiers AR902 and PR929 with aromatic groups has the highest speed and best performance due to the similar aromatic groups with those in asphaltenes, which produced the least stable oil film. This study provides a valuable guideline for the selection of demulsifier for light crude oil emulsions and enhanced demulsification mechanism studies.

This paper is devoted to the investigation of N-isopropylacrylamide-based microgels as potential drug delivery systems and other pharmaceutical applications. Surfactant free emulsion polymerization (SFEP) and emulsion polymerization techniques were employed to copolymerize PNIPAM with acrylic acid (AA), with 3-acrylamidophenylboronic acid (3-APB) and (3-acrylamidopropyl)trimethylammonium bromide (ATMA), and with 1-vinylimidazole (VI). The resultant microgel particles exhibited multi-responsive behaviour being sensitive to changes in temperature, pH. The PNIPAM-co-3-APB-ATMA microgels were sensitive to concentration of glucose, whilst the PNIPAM-co-VI microgels were sensitive to certain metals, copper in particular. The microgel containing AA exhibited characteristic temperature-sensitive behaviour with volume a phase transition temperature (VPTT) in the range of 35°–40 °C and showed pH-sensitive features as the particles collapsed at low and swelled at high pH values. The microgels containing various concentration of VI were also examined on sensitivity to temperature and pH changes. The investigation of such microgels with increasing temperature showed similar behaviour to those containing AA as the microgel particles shrunk continuously and the LCST has been shifted to higher temperatures (in the range of 35°–45 °C). The particle size of these microgels was also investigated as a function of pH; the microgel particles swelled at low and collapsed at high pHs. The particle size of the PNIPAM-co-3-APB-ATMA microgels was investigated both as a function of temperature and glucose concentration. The microgels showed typical behaviour of PNIPAM microgels copolymerized with functional monomer (3-APB and ATMA) by continuous shrinking with increasing temperature and shifted LCST towards higher temperatures. Additionally, these microgels showed swelling behaviour with the increase of glucose concentration at physiological conditions, i.e. particles swelled in the range of glucose concentration between 0.1 and 10 mmol/L at 35 °C and pH 7.5. The behaviour of these microgels was also investigated at 35 °C and pH 8.5 as a function of glucose concentration. Although the swelling of the particles was slightly larger at pH 8.5, considerable swelling was also observed at pH 7.5 making them the first microgel system to be glucose sensitive at physiological pH and temperature. Swelling of the particles at the pH level of human blood (in range of 7.35–7.45) as well as having lower critical solution temperature in the range of temperature of the human body gives an opportunity to develop these microgel particles further as potential drug-delivery agents.

Polymer flooding is one of the most effective processes to enhance oil recovery (EOR), but the poor thermo-stability and salt tolerance of the currently used water-soluble polymers challenge their usage in presence of high temperatures and salinity within the oil reservoirs. Thermo-viscosifying polymers (TVP’s) are a novel class of materials developed for EOR applications in high-temperature and high-salinity oil reservoirs. In this study, the interactions of novel TVP with different salts and its temperature and rheological properties were evaluated. The thermal and rheological properties of this polymer were studied as a function of polymer concentration, and salinity at different temperatures. It was observed that by increasing temperature, the aqueous solution viscosities first smoothly decreased, but then increased at above the critical association temperature (T cass ). T cass was also found to be a function of the TVP’s concentration and temperature. Although, the shear effect demonstrated shear-thinning, with the increase of temperature, the shear viscosities showed shear thickening at all concentrations of polymer. Furthermore, the novel TVP with low concentration showed good viscoelastic properties compared with high concentration of HPAM. The introduced novel TVP’s thermo-thickening tendency is enhanced by increasing temperature and salinity which makes it more promising for EOR applications.

Adsorption of model systems of triclosan by mineral sorbent diatomite is studied. The triclosan equilibrium concentration was measured spectrophotometrically, the morphology of the diatomite characterized using scanning electron microscopy and the amount of the adsorbed triclosan on the diatomite quantified by a mass balance. Adsorption isotherms were analyzed according to the linear/nonlinear form of Langmuir, Freundlich, Sips and Toth isotherm models isotherms, using AMPL software. It is shown that nonlinear Langmuir and Sips isotherm model provided suitable fitting results and no pronounced difference in adsorption efficiency between isotherms measured after 1, 2 and 3 days adsorption was observed. Determined maximum adsorption capacity of diatomite towards triclosan qs is 140 mg/g. Averaged calculated values of ΔG are −9.9 and −9.6 kJ/mol for Langmuir and Sips models respectively. The negative sign of such values indicates spontaneous, physical in nature adsorption.

The produced fluid from reservoirs are generally in the form of emulsion with oil and water, in which indigenous components such as asphaltene, resin and wax can act as natural emulsifiers. In this study, water-in-oil emulsions were prepared with five light crude oils from CQ Oilfield respectively, and investigated to identify the indigenous stabilization mechanism based on a novel visualized method by in situ solvent-dissolution (ISV). The emulsion stability was studied by dehydration rate and droplet size via bottle test and microscope. Saturate-Aromatic-Resin-Asphaltene (SARA) separation, wax appearance temperature (WAT) measurement, and gas chromatography were applied to characterize the indigenous components in the crude oil. Colloid instability index was introduced to analyze the solubility of asphaltene. Furthermore, the stabilization mechanism of the oil emulsion was investigated by ISV method in both macroscopic and microscopic scales via dilution by n-heptane and toluene. The viscosity of oil, interfacial viscosity, interfacial storage and loss modulus were measured by rheometer to evaluate the contribution of the stabilizer quantitatively. The results showed that emulsion stability increased with the concentration of asphaltene, especially over a critical concentration. This ISV method provides a convincing approach to understand the indigenous stabilization mechanism of original crude emulsion vividly rather than that in the model emulsion. The interfacial viscosity, viscoelasticity or oil viscosity increased with asphaltene concentration in the crude oil. The strong elastic interface film formed with asphaltene restricted the droplet coalescence and controlled the stability of emulsions, which was found to be the crucial stabilization mechanism. Asphaltene and its concentration are the dominating factors of stability of these light crude oil emulsions. This work not only clearly clarifies the significant role of asphaltene in the stability of light crude oil emulsions, but also proposes a convenient in situ method to study the emulsion stabilization mechanism.

Nowadays, photovoltaic technology has been recognized as a popular energy source in most parts of the world. The temperature rise in photovoltaic cells is one of the major weak points of this technology which impacts on its electricity generation. Using nanofluid circulation as the coolant of photovoltaic modules, is one of the methods concerned by scholars. In this paper, using carbon black nano particles in water was investigated experimentally, and the concentration range of 0–0.4 wt% were tested. Results showed an unexpected cooling behavior of carbon black/water nanofluid. So that, the concentration of 0.21 wt% was found to be the best case. This concentration led to produce 7% more output power in comparison with pure water as coolant and 54% more output power in compare with the conventional photovoltaic module. In order to precisely calculate the electrical energy efficiency, the consumed pumping power was considered, too. The exergy assessment is another investigated matter in this paper and a modified method for exergy efficiency calculation is presented. Accordingly, the overall exergy efficiency rises 15.2% and the entropy generation depresses 1.4% compared with the conventional module, for the best case.

The present work is devoted to design of capsules with hydrophilic drugs such as insulin to preserve its stability and biological activity using the double emulsion technique and its subsequent entrapment into biodegradable microcapsules with shells made of Chitosan and Xanthan Gum complexes. Formulation parameters (type of biopolymer, type of oil and stabilizer and its concentration, volume fraction and content of internal aqueous phase, time and regime of mixing) were investigated. The effect of the complexes on the process of emulsion formation and on the stability and characteristics of the resulting emulsions was investigated by measurements of size distribution (DLS) and interfacial charge (Zeta-potential). The resulting capsules were characterized by microscopy, size distribution and Zeta-potential measurements. The release kinetics of insulin was monitored using UV–vis spectroscopy and showed the progressive enhancement of sustainability.

In this paper the preparation of nano-structured silver oxide thin films with different oxidation states with promise as electrode materials for supercapacitors by reactive magnetron sputtering is investigated. The chemical, structural, surface morphological dependence of the films on oxygen gas flow rate and deposition power were examined by scanning electron microscope (SEM), X-ray diffraction (XRD) and energy dispersive X-ray (EDX). The average thickness of the films was controlled in the range of ≈50–330 nm. The XRD spectra of the films indicated the formation of bi-phase films comprised of silver and silver oxides with different oxidation states. The wettability of the films in contact with different probing liquids was investigated by measuring the contact angles using a goniometer. It was shown that the silver oxide films are relatively hydrophilic and increasing oxygen flow rate increases the wettability of the films toward water as a result of an increase in the oxidation state of the films and consequently clustering of electrons in polar molecules of water around the oxides at higher oxidation states. This is further confirmed by the analysis of the surface energy measurements.

The influence of salt and temperature on the viscosity of a hydrophobically modified polyacrylamide-based (PAM-based) novel functional polymer (RH-4) was investigated. To study the viscosifying mechanism in brine solution, scanning electron microscope (SEM) was applied to observe the network microstructures of polymer solution. The solution apparent viscosity behaviors of the RH-4 polymer are studied as functions of concentrations, pH value, salt types and amount, microscopic morphology. The viscoelasticity of aqueous solutions of RH-4 polymer changed with shear rate under high salinity condition. Additionally, the influence of temperature on the apparent viscosity of RH-4 polymer was investigated. The results showed that the viscosity decreased at lower salt concentrations and increased at higher salt concentrations. The SEM results show that the network structures of RH-4 polymer become much more condense at high salinity, which lead to the increasing its apparent viscosity. When the salinity reaches 80,000 mg/L, thickening ability of the system is the strongest. With the rise in temperature, the viscosity of polymer solutions with various concentrations decreases slightly except for the two concentrations of 1000 mg/L and 1100 mg/L, their viscosity increases with the increasing of temperature. The thickening tendency is enhanced by high salinity and high temperature, which makes it more promising for EOR.

Microbiological contamination of surfaces is a general and everyday phenomenon, which, however, is often underestimated or not taken into account at all. The formation of a microorganism film is the first stage of such an unpleasant phenomenon as biofouling, from which shipping, as well as sea and port infrastructure, suffer particularly. This paper is devoted to the synthesis of micro- and nanocapsules with a polyurea shell, containing a 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) biocide core by using surface polycondensation. The obtained capsules were characterised by the scanning electron microscopy, laser correlation spectroscopy, energy dispersive X-ray spectroscopy of the EDXS, and by thermogravimetric analysis. The studies revealed the monodispersity and positive charge of the containers, which have folded morphology. The biocide content in the finished containers was 30÷32%.

The possibility and conditions for the formation of nano- or submicrocapsules loaded with hydrophobic active ingredients (alkoxysilanes) into the matrix of coatings with self-lubricating effect are considered. The optimal composition of the alkoxysilane submicrocapsules, and their physicochemical properties were determined. The longer the radical chain length is, the lower is the rate of hydrolysis, and, accordingly, the more stable is the formed emulsion. The methods of laser correlation spectroscopy in measuring the size and zeta potentials of the submicrocapsules with different loads of the active agent allowed to determine the optimal ratios of the active ingredients. The optimal concentration of the active agent is between 4 and 9%. Based on contact angle studies, octadecyltrimethoxysilane was selected as optimum compound. The introduction of 4 wt% of octadecyltrimethoxysilane reduces the friction coefficient of coatings by 20–30% under vibrating motion and by 15–20% under continuous motion. The data obtained can also be useful for the encapsulation of other hydrophobic active agents and for various other purposes, for example, for the introduction of biocidal agents.

3-(trimethoxysilyl)propyl methacrylate (TPM) hydrolyzes via the alkoxy groups attached to silicon when it comes into contact with an aqueous phase and forms surface active 3-(trihydroxysilyl)propyl methacylate (THPM) molecules. Their formation and adsorption at the water/air interface, i.e. decrease in the surface tension, can be used as a sensor to follow the hydrolysis process and can help to explain the role of these molecules in the emulsion formation and stabilization process. The target of this contribution is to demonstrate the experimental details of a surface tension sensor using a bubble profile analysis tensiometer for monitoring the chemical reaction of TPM with water and to explain the peculiarities observed in the measured signal, i.e. irregularities in the dynamic surface tension. Auto-oscillations of the surface tension were observed during the measurements, which are connected to a complex of different types of flows in the volume of the aqueous phase. The kinetics of the reaction and hence of the surface tension can be controlled by changing the pH of the aqueous phase. It is also possible to prevent auto-oscillations by means of a continuous gentle stirring of the aqueous phase, which then allows a quantitative monitoring of the rate of the TPM/water reaction.

The adsorption of triclosan as model system was studied to qualify activated carbon sorbents recycled from gas masks (civilian gas mask GP5). The triclosan equilibrium concentration was measured spectrophotometrically, the morphology of the activated carbon characterized by scanning electron microscopy, and the amount of the adsorbed triclosan on the activated carbon quantified by a mass balance method. Experimental isotherms were fitted by Langmuir, Freundlich and Sips adsorption models. It was obtained that the contact time is a crucial sorption parameter that provides information on the optimum adsorption efficiency. It was shown that the maximum efficiency of GP5 (88%) is obtained after 10 days of adsorption at a maximal concentration of triclosan and carbon loading 1 mg/l. No significant adsorption efficiency differences were measured after 5 and 10 days of adsorption. The non-linear Sips isotherm, a combined Freundlich–Langmuir model, provides suitable fitting results. The observed remarkable adsorption capacity of activated carbon (GP5) towards triclosan adsorption (∼85 mg/g) makes it a viable solution for wastewater treatment.

Emulsions stabilized by the supramolecular systems with sodium polyacrylic acid and amphiphilic polymers with different hydrophobic monomer contents were investigated. Multiple-light scattering was used to characterize the stability of emulsions. Optical microscopy and particle size analyzer were utilized to determine the droplet size distributions. The glass-etching micro model and microscopy were used to observe the emulsion stability in the porous media. To explore the stability mechanisms of emulsions, the rheology of the external phase and the oil/water interface were determined with the Physica MCR301 Rheometer. Emulsions formed by the supramolecular systems exhibit a better stability than the individual amphiphilic polymer systems. Moreover, the stability of emulsions formed by the supramolecular systems increases with the hydrophobic monomer content of amphiphilic polymers. The results can be attributed to the large viscous effect of the external phase and the high strength of the oil/water interfacial film in the emulsions. The results provide a theoretical foundation for future studies of the oil displacement efficiency by amphiphilic polymer supramolecular systems in tertiary oil recovery.

In recent years, with the further development of old oilfields, in order to further improve the oil recovery, they must be conformance controlled. Among various types of conformance control methods, polymer gels composed of polymers and crosslinkers have attracted widespread attention because of their efficiency and low costs. Among them, organic chromium gels with their good formation adaptability and high stability have been fully developed in recent decades. This review introduces the different types of polymers and crosslinkers used in the preparation of organic chromium gels, and the mechanisms of affecting their performance are analyzed. On this basis, the organic chromium gels for different formation conditions are introduced, including nanoparticle-reinforced and compound organic chromium gels. At the same time, evaluation methods of organic chromium gels are introduced, while the focus is on the in-situ measurement method (mirco-rheology) of gel formation time developed in recent decades. Based on the currently developed organic chromium gel and the analysis of the development status in oilfields, future directions like the use of supramolecular organic chromium gel and shear organic chromium gel are suggested.

Emulsion formation is inevitable during polymer flooding. In order to study the mechanism of the emulsion stability formed by inclusion complex and crude oil, the optimal inclusion ratio of inclusion complex was determined, and then, the properties of the emulsion such as particle size, stability, and interface film strength were tested by microscope, laser particle size analyzer, rheometer, and stability analyzer. Test results show that the addition of cyclodextrin polymer in inclusion complex have a positive effect on the stability of the emulsion. There are two main mechanisms which cyclodextrin polymers enhance the stability of emulsions. Firstly, with the addition of the cyclodextrin polymer, the viscosity of the external phase is increased, making it difficult for emulsion to coalesce and demulsify. Secondly, the cyclodextrin polymer and the hydrophobic chain of the amphiphilic polymer are adsorbed at the oil-water interface together, which enhances the interface film strength. The stability mechanism of the emulsion formed by the inclusion complex and crude oil has laid a foundation for its application in oil displacement.

The subject of the imbibition enhancing oil recovery (IEOR) mechanism by the use of ultra-low interfacial tension (IFT) and emulsifying surfactants remains controversial. In this study, an ultra-low IFT surfactant (SOL) and an easy-emulsifying surfactant (SDBS) were selected on the basis of their interfacial tension and emulsion stability to elucidate the IEOR mechanism. The cell test method was used to measure the imbibition oil recovery. The micro-IEOR mechanisms were analyzed by using a new device making use of a visual micromodel. The results show that the imbibition oil recovery was 8% with SDBS and 17% with SOL, with the two surfactants having a similar variation of imbibition speed, while the ultra-low IFT made the water front more uniform. The emulsion with low coalescence stability formed by SDBS improves the displacement efficiency and diverts flow, improving the sweep efficiency as well. This work proposes a new method for analyzing the micro-IEOR mechanism and provides new fundamental information to the selection of an efficient IEOR surfactant.

In the present work, the properties of dodecyl dimethyl phosphine oxide (C12DMPO) at the water/decane interface are studied and compared with those obtained earlier at the interface to hexane. To simulate the interfacial behavior, a two-component thermodynamic model is proposed, which combines the equation of state and Frumkin isotherm for decane with the reorientation model involving the intrinsic compressibility for the surfactant. In this approach, the surface activity of decane is governed by its interaction with C12DMPO. The theory predicts the influence of decane on the decrease of the surface tension at a very low surfactant concentration for realistic values of the ratio of the adsorbed amounts of decane and surfactant. The surfactant&rsquo, s distribution coefficient between the aqueous and decane phases is determined. Two types of adsorption systems were used: a decane drop immersed into the C12DMPO aqueous solution, and a water drop immersed into the C12DMPO solution in decane. To determine the distribution coefficient, a method based on the analysis of the transfer of C12DMPO between water and decane is also employed.

In the past ten years, preformed particle gel (PPG) has been widely applied in oil fields as an effective conformance control agent for reducing water cut in oilfield. However, there is little research on the injection rate of subsequent water flooding after PPG injection on recovery. In this paper, the swelling, scanning electron microscope, rheological and viscoelasticity tests were performed to investigate into the characteristics of PPG and explore the mechanism of enhancing oil recovery by stepwise increasing subsequent water injection rate. In the homogeneous and heterogeneous cores, the plugging effect of PPG was judged according to different pressures, and the subsequent water injection rate is 0.5–0.75, 1, 1.25, and 1.5 mL/min after the water cut of each injection rate reaches 100% stage. The distribution of residual oil in different displacement stages was studied by nuclear magnetic resonance (NMR). The experimental results show that the PPG has high viscoelasticity and can be fully swelled within 42 h in 70 °C. The subsequent increase in flow rate can promote the previous phase of the PPG particles remaining in the pore throat to move, and then have a better effect to drive the oil droplets attached to the rock surface. Stepwise increasing the subsequent water flooding injection rate in the homogeneous formation can improve the oil washing efficiency and reduce the residual oil saturation. In the heterogeneous formation, the recovery factor is improved by stepwise increasing the sweep coefficient.

Drop profile analysis tensiometry is applied to determine the distribution coefficient of a nonionic surfactant for a water/hexane system. The basic idea is to measure the interfacial tension isotherm in two configurations: a hexane drop immersed in the surfactant aqueous solutions at different bulk concentrations, and a water drop immersed into a hexane solution of the same surfactant. Both types of experiments lead to an isotherm for the equilibrium interfacial tensions with the same slope but with a concentration shift between them. This shift refers exactly to the value of the distribution coefficient.

The synthesis and properties of submicrocontainers with a shell of nanoparticles of silicon dioxide and a core of polymerized 3-(Trimethoxysilyl) propyl methacrylate loaded with 5Dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) are considered. The resulting containers were characterized by scanning electron microscopy SEM, laser correlation spectroscopy and thermogravimetric analysis. The obtained submicrocontainers show low polydispersity with a small increase in size in comparison with the initial droplet size of the Pickering emulsion. The Zeta potential of the final containers was sufficiently negative at pH7 to be stable. The maximum release of encapsulated biocide was observed over approximately 24–27 h with a lease of about 78% of the encapsulated biocide during 3.5 h. The effectiveness of the encapsulated biocide by the Pickering emulsion technique was studied by tests on the growth rate of a microfungi colony (Aspergillus niger, Aspergillus awamori) and the growth rate of the bacteria Bacillus cereus. The test shows that the submicrocontainers of DCOIT facilitate a growth inhibition of 70% against 52% for the free biocide after 5 days, this is due to the fact that free biocide loses its activity promptly, while the encapsulated biocide is released gradually, and thus retains its effectivity for a longer time.

Polymer/surfactant mixtures have a wide range of industrial and technological applications, one of them being the use in microencapsulation and emulsion stabilization processes. These mixtures are able to form adsorption layers at the surface of oil droplets and so affect the emulsion stability, which depends on the polyelectrolyte/surfactant nature, concentrations ratio, method of the emulsification, etc. Polyelectrolytes alone show low surface activity in contrast to surfactants, which adsorb at the water/oil interface, making the droplets charged, but they are insufficient to stabilize emulsions. When an oppositely-charged polymer is added to the surfactant solution, a steric barrier is formed, which prevents coalescence and enhances the stability. The present review is devoted to the recent studies of the use of polymer/surfactant mixtures for the encapsulation of active ingredients and stabilization of single and double emulsions. Active ingredients are added to the oil phase prior to emulsification so that any subsequent dissolution of the core, like in other encapsulation protocols, can be omitted. By measuring the interfacial tension and dilational rheology it is possible to find optimum conditions for the emulsion formation and hence for encapsulation. Therefore, such systems have become a prominent approach for the encapsulation of active ingredients.

Effect of anionic polyelectrolyte sodium carboxymethylcellulose on surface tension of alkyl sulphate derivatives of sulphoacid solutions, sodium dodecyl sulphate and ammonium dodecyl sulphate, has been investigated. It has been established that the compositions of surfactants–sodium carboxymethylcellulose show an appreciable synergetic effect of surface tension decrease. The values of surface activity and kinetic adsorption constants of the associates of surfactants with NaCMC at the interface liquid-gas were determined.

The surface tension of compositions consisting of nonionic polyethylene glycol and surface active substances of different nature and influence of temperatures on properties of their adsorption layers were studied. To be taken into account the basics of classical chemical thermodynamics and colloidal chemistry, the thermodynamic parameters were determined for the adsorption of glycol, cetyl pyridinium bromide, Tween- 80 and sodium dodecyl sulfate. Adsorption speed was valuated By Kinetic curves of a liquid /gas interfaces. As a surfactants were taken the anionic surfactant – sodium dodecylsulphate, cationic surfactant cetylpyridinium bromide and nonionic Tween-80. The reason of using nonionic polyethyleneglycol as polymer is that the polymer is not toxic, biodegradable and it has no harm to the human body. That is why they are largely used in food industry, pharmaceutics, cosmetics and household chemical products.

The protein obtained in the alkali hydrolysis consist of amino acid residues that are natural macromolecular surfactants and they can may be used as effective foam stabilizers. The features of dynamic surface tension and stability of foams on based of aqueous solutions of keratin hydrolyzate in a concentration range of 1-10% were studied. The relaxation time – of the adsorption layers of keratin hydrolyzate is equaled to 10-12 min. The parameters of adsorption at the liquid – gas interface were defined. The maximum surface activity, foaming and foam stability corresponds to a neutral pH close to isoelectric state of the protein. Increase the foam stability at pH ~ 7 proceeds due to the conformational changes of macro-molecules of the protein at the interface liquid – gas, forming particles of colloidal size, clogging channels Plateau-Gibbs and preventing expiration of the liquid film between.

The adsorption from mixed aqueous solutions of polyallyl amine hydrochloride (PAH)/sodium dodecyl sulphate (SDS), both in absence and presence of the inorganic electrolyte NaCl, at the solution/tetradecane interface is studied experimentally by drop profile analysis tensiometry. The results are discussed in terms of a competitive adsorption of PAH + SDS complexes and unbound SDS molecules. A thermodynamic model, developed originally for the adsorption of protein/surfactant mixtures, is modified such that it takes into account the formation of PAH + SDS complexes and the influence of the SDS concentration on their surface activity. It is shown that at low SDS concentrations the properties of the adsorbed monolayer are determined mostly by the adsorption of complexes, while at high SDS concentrations the properties are determined mostly by the SDS adsorption and the effect of the PAH + SDS complexes is negligibly small. The proposed modified model demonstrates good agreement with the experimental data.

In drop profile analysis tensiometry, the ratio of drop surfaces area S to volume V is large, i.e., S/V >> 1. In such a case, the concentration of a surfactant within the drop bulk decreases due to adsorption at the drop surface. In contrast, in bubble profile analysis tensiometry, we have S/V << 1 so that depletion due to adsorption is negligible. A protocol is presented to determine the correct adsorption parameters of surfactants from surface tension data measured by bubble and drop profile analysis tensiometry. The procedure is applied to experimental data measured for selected surfactants of different adsorption activities: C10OH, CTAB, Tween 20, and the equimolar mixture SDS + DoTAB. The results show that for surfactants with higher surface activity, the differences between the surface tensions measured with the drops and bubbles profile analysis tensiometry, respectively, are larger, while for less surface-active surfactants, such as SDS, the results obtained from drop and bubble profile experiments are very close. The correction procedure is based on the same set of adsorption parameters used to fit both the experimental data obtained from drop-based measurements (which involve the depletion effects) and those data measured in a way that depletion effects are negligible.

Mixed polymer-surfactant systems have broad applications, ranging from detergents, paints, pharmaceutical, and cosmetic to biotechnological. A review of the underlying polymer-surfactant association in bulk is given. While ionic surfactants bind broadly to polymers, nonionics only do so if the polymer has a lower polarity and can interact by hydrophobic interactions. Water-soluble polymers, which have hydrophobic groups, form physical cross-links, hence they may be used as thickeners. The rheological behaviour is strongly influenced by various cosolutes; especially strong effects are due to surfactants and both a decrease and an increase in viscosity can occur. When the polymer-surfactant interactions are particularly strong, an associative phase separation can occur, like in the case where there is electrostatic attraction as well as hydrophobic; this and other types of phase separation phenomena are described. Except for linear ionic and nonionic polymers, the interactions between surfactants and cross-linked polymers, microgel particles and covalent macroscopic gels are analyzed, as well as the possibility of forming gel particles of interest for encapsulation purposes. Furthermore, the behavior of these mixed systems on surfaces is discussed. In particular, we consider the adsorption of mixtures of ionic polymers and oppositely charged surfactants on polar and nonpolar surfaces. Depending on concentration, an ionic surfactant can either induce additional polyion adsorption or induce desorption. Kinetic control of adsorption and, in particular, desorption is typical. Important consequences of this include an increased adsorption on rinsing and path dependent adsorbed layers. Recently, considerable attention has been given to the interaction between DNA and cationic surfactant, both as a means to understand the behaviour of DNA in biological systems and to develop novel formulations, for example for gene therapy. Here we review aspects such as DNA compaction, DNA covalent gels and DNA soft nanoparticles.

Stabilization of emulsions by mixed polyelectrolyte/surfactant systems is a prominent example for the application in modern technologies. The formation of complexes between the polymers and the surfactants depends on the type of surfactant (ionic, non-ionic) and the mixing ratio. The surface activity (hydrophilic-lipophilic balance) of the resulting complexes is an important quantity for its efficiency in stabilizing emulsions. The interfacial adsorption properties observed at liquid/oil interfaces are more or less equivalent to those observed at the aqueous solution/air interface, however, the corresponding interfacial dilational and shear rheology parameters differ quite significantly. The interfacial properties are directly linked to bulk properties, which support the picture for the complex formation of polyelectrolyte/surfactant mixtures, which is the result of electrostatic and hydrophobic interactions. For long alkyl chain surfactants the interfacial behavior is strongly influenced by hydrophobic interactions while the complex formation with short chain surfactants is mainly governed by electrostatic interactions.