High Surfactant Research Articles

Laser induced fluorescence studies on the distribution of surfactants during drop/interface coalescence

The spatiotemporal distribution of fluorescent surfactants on the merging interfaces during the coalescence of an aqueous drop with an organic/aqueous flat interface was studied experimentally with high-speed laser induced fluorescence. The aqueous phase was a 46% glycerol solution, while the organic phase was a 5 cSt silicone oil. A fluorescently tagged surfactant was used at a concentration of 0.001 mol/m3 in the aqueous phase. To vary the concentration of surfactants on the interfaces, the drop and the flat interface were left to stand for different times before the coalescence experiments (different interface ages). It was found that when a drop rested on the interface, the surfactants adsorbed on the interfaces were swept outwards by the draining liquid film between the drop and the flat interface and reached a peak value at 0.75Rh away from the centre of the film, where Rh is the horizontal drop radius. After the film rupture, the concentration of the surfactants at the tip of the meniscus increased. Once the film had retracted, the concentration of the surfactants peaked at the meniscus at the bottom of the drop. As the liquid in the drop started to merge with its homophase, the drop formed a cylinder from the upward capillary waves on the drop surface. The surfactant concentration was found to be low at the top of the liquid cylinder as the interface was stretched by the convergence of the capillary waves. Subsequently, the cylinder began to shrink and the top part of the drop acquired a high surfactant concentration.

Efficiency of ultrasound for degradation of an anionic surfactant from water: Surfactant determination using methylene blue active substances method

The removal of a surfactant from wastewater is usually difficult due to its toxicity and low biodegradability. The aim of this study was to apply sonoreactor for degradation of an anionic surfactant from aqueous solution. An ultrasonic bath with frequency of 130 kHz was used to investigate the effects of different operational parameters such as sonication time, initial concentration and power. In this study, experiments of linear alkylbenzene sulfonates solution were performed using methylene blue active substances method. Experiments were performed at initial concentrations of 0.2 , 0.5 , 0.8 and 1 mg/L, frequency of 130 kHz, acoustic powers value of 400 and 500 W, temperature of 18–20 °C and pH value of 6.8–7. This study showed that linear alkylbenzene sulfonates degradation rate was found to increase with increasing sonication time and power. In addition, as the concentration increased, the linear alkylbenzene sulfonates degradation rate decreased in the ultrasonic reactor.•Surfactants are one of the largest groups of pollutants which exist in almost all urban and many industrial wastewaters.•Ultrasonic reactors alone may not be useful for reducing completely complex wastewaters of high surfactant load.•Application of ultrasonic reactors in combination with other treatment processes including Ozone, UV irradiation, chlorination, Fenton, nanoparticles and H2O2 could be used as a pre-treatment unit in a sequential chemical and biological treatment process.

Development and application of polymetric surfactant emulsification and viscosity reduction system

Abstract Compounding polymer AP-P4 with high viscosity-reducing Gemini Surfactant HD, which is used as an emulsifier viscosity reduce, to improve the stability of the O/W emulsion while the viscosity reduction rate is kept. A polymeric surfactant emulsification and viscosity reduction system capable of forming a relatively stable O/W emulsion of heavy oil (0.5% HD+0.1% AP-P4) is then compounded. The system has been characterized as a high viscosity reduction rate and high stability. Meanwhile, the production liquid does not need to be added with a demulsifier and only needs to be heated to 70 °C to achieve effective demulsification. The influencing factors of the performance of the polymetric surfactant emulsification and viscosity reduction system were studied. When the oil-water ratio was 70:30 and 60:40, the viscosity reduction rate was 97.47% and 99.09%, respectively; after 15 h at 30 °C, the dehydration rates were 95.8% and 99.2%, respectively. The dehydration rate after 15 h at 70 °C was 98.1% and 99.4%, respectively; at 30 ∼ 50 °C, the water phase temperature has a greater impact on the viscosity; at 60 °C, 70 °C, the water phase temperature has little effect on the viscosity; as the temperature of the aqueous phase increased, the stability of the emulsion deteriorated. When the aqueous phase temperature was 30 °C, 50 °C and 70 °C, the dehydration rates of the emulsion after 15 h were 95.8%, 96.7% and 98.1%, respectively; As the degree of mineralization increases, the viscosity reduction rate decreases, and the stability of the emulsion deteriorates. The system has been used in field test for 2 injection wells, and the production rate of the two wells increased with a peak value of 25 m3/d and 20 t/d, respectively.

The Effect of Particles on Surface Tension and Flotation Froth Stability

It is widely accepted that particles stabilise flotation froths and that stable froths result in improved flotation performance. Predicting the effect of particle addition on froth stability is, however, challenging. Dynamic surface tension measurement using maximum bubble pressure presents an attractive technique to investigate the effect of surfactant and particles at the air-water interface. The range of bubble lifetimes that can be studied (typically 0.1 to 60 s) is analogous to variations in air rate in flotation cells, and the corresponding changes in surface tension give an indication to the diffusion and adsorption rates of particles at the interface. In this paper, we use dynamic surface tension measurements to investigate the effect of particles on bubble surfaces at the microscale and link this to bulk froth stability measurements carried out using a froth column. Using the maximum bubble pressure method, the results show that the addition of particles results in lower surface tension, both at the dynamic (i.e. short) bubble lifetimes and towards equilibrium (i.e. 60 s bubble lifetime). This corresponds with the bulk froth stability measurements, where the three-phase system yielded more stable froths than the surfactant only system. Furthermore, increased particle loading at the air-water interface, whether through higher surfactant concentrations or lower air rates (longer bubble lifetimes), gave lower surface tension and higher froth stability. This demonstrates the link between bubble loading and froth stability. It is proposed that the maximum bubble pressure technique can be used to predict froth stability for two- and three-phase systems, enabling the effect of particle loading to be accounted for and quantified. Moreover, the technique has the potential to allow rapid determination of particle and surfactant diffusion at the air-water interface and prediction of the corresponding effect on bulk froth behaviour.

Dynamic interfacial properties and foamability of polyelectrolyte-surfactant mixtures

Polymer/surfactant interaction and complexes can strongly influence foam formation and stability, however, a clear mechanism is still unknown and under investigation. Critical Aggregation Concentration (CAC) is introduced as an important parameter in recent investigations, however, CAC is mostly characterized as an equilibrium parameter, while foam formation and consequently the stability mechanism, is significantly influenced by the dynamics of adsorption. In this research the dynamic surface tension and viscoelasticity mixtures of Polystyrene Sulfonate (PSS) as an anionic polyelectrolyte and Cetyl Trimethyl Ammonium Bromide (CTAB) as a cationic surfactant, at the air-water interface are investigated by using Profile Analysis Tensiometry (PAT). The measured dynamic surface tension values illustrate three different regions of the surfactant/polymer ratio. It is demonstrated that a minimum number of surfactants per polymer molecule is needed in order that the polymer-surfactant complexes become sufficiently surface active and adsorb significantly at the water-air surface. For high surfactant concentrations, the large amounts of excess CTAB compete with polymer-surfactant complexes at the interfaces and remove the complexes into the bulk. The measured elasticity values confirm this observation. At intermediate surfactant concentration, when the complexes have their maximum surface activity, a fast dynamics of adsorption is observed and the measured elasticity values go through a maximum. The results of foam formation and stability also show a meaningful correlation with these results using Ross-Mill test and gas sparging method.

Adjuvants for Prohexadione‐Calcium Applied to Alfalfa Interseeded into Corn

Core Ideas Optimal adjuvant selection for ensuring effectiveness of prohexadione‐Ca applied to interseeded alfalfa is unknown. All adjuvants tested provided equivalent effectiveness for prohexadione‐Ca applied to interseeded alfalfa. Supplemental ammonium sulfate did not further enhance the effectiveness of prohexadione‐Ca. Application of the growth retardant prohexadione‐calcium (calcium 3‐oxido‐5‐oxo‐4‐propionylcyclohex‐3‐enecarboxylate; PHD) on interseeded alfalfa (Medicago sativa L.) improves its establishment under silage corn (Zea mays L.). This study evaluated the relative effectiveness of crop oil concentrate (COC), high surfactant oil concentrate (HSOC), methylated seed oil (MSO), and nonionic surfactant (NIS) as adjuvants for commercially formulated PHD (Apogee) when applied with and without supplemental ammonium sulfate (AMS). Acidified solutions of PHD (0.25 kg a.i. ha−1) plus adjuvants were sprayed on 23 to 27 cm tall glyphosate‐resistant alfalfa seedlings that were interseeded immediately after corn planting at two sites in Wisconsin. All PHD–adjuvant–AMS combinations were equally effective, reducing alfalfa height by an average of 16% within 4 wk after treatment and increasing alfalfa stand counts after corn harvest by 30% compared with the non‐PHD treated control. The results suggested a variety of adjuvants may be used when applying PHD to interseeded alfalfa.

A Proposed Role of Surfactant in Platelet Function and Treatment of Pulmonary Hemorrhage in Preterm and Term Infants

Background: We evaluated the effect of surfactant on platelet function as a potential contributing mechanism to the pathogenesis of pulmonary hemorrhage (PHEM) in term and preterm infants. Methods: Cord blood samples were collected from neonates following delivery. Complete blood count and platelet function were measured using a cone and platelet analyzer (CPA). Increasing surfactant concentrations were added to platelets in vitro, and the adhesion molecule P-selectin and the monoclonal antibody PAC-1 were evaluated following platelet activation by flow cytometry. Results: Forty-one infants (11 preterm and 30 term) were studied. CPA revealed a significant decrease in the average size of the aggregates and in platelet adhesion when surfactant was added. In term infants, the addition of surfactant to native platelets yielded an increased binding capacity of PAC-1 but did not affect P-selectin expression. In preterm infants, platelet activation with adenosine diphosphate in the presence of a high surfactant concentration (0.5 mg/mL) resulted in increased PAC-1 binding and no change in P-selectin expression. Conclusions: The platelets of preterm infants are less active (hyporesponsive) than those of term infants, both in their native state as well as after stimulation with various agonists. Surfactant may play an important role in treating PHEM in preterm infants.

Aqueous foams stabilized with silica nanoparticle and alpha olefin sulfonates surfactant

Carbon dioxide (CO2) foams have been introduced to improve mobility of CO2 in CO2 flooding. However, using surfactant alone to stabilize CO2 foam has potential weaknesses such as high surfactant retention in porous media and the foam is thermodynamically unstable for a long-term. Nanoparticle has been an alternative in stabilizing CO2 foam longer. This study aims to analyze CO2 foam stability at varying concentrations of surfactant, silica nanoparticle (SNP) and brine. The additions of SNP in anionic surfactant of alpha olefin sulfonates (AOS)-water and in AOS-brine towards foam stability were demonstrated in this study. CO2 foam stability was measured through the foam height observation and bubble size analysis. The performance of SNP and AOS suspensions in stabilizing foam were observed at different concentrations of AOS (0.1, 0.3 and 0.5 wt%), SNP (0.1, 0.3 and 0.5 wt%) and brine (0.1, 1 and 5 wt%). The results revealed that the CO2foams were most stable at 0.3 wt% SNP suspension in 0.5 wt% AOS-water. It was found that the most stable foams formed at concentration of 1 wt% of brine. Smaller and uniform bubble size has been produced at 0.3 wt% SNP in 0.5 wt% AOS solution. Thus, concentrations of surfactant, SNP and brine have significant effects on CO2 foam stability.

Purification and Characterization of Plantaricin LPL-1, a Novel Class IIa Bacteriocin Produced by Lactobacillus plantarum LPL-1 Isolated From Fermented Fish.

Bacteriocins are ribosomally synthesized peptides or proteins possessing antibacterial activity against foodborne pathogens and spoilage bacteria. A novel bacteriocin, plantaricin LPL-1 was determined as a class IIa bacteriocin according to the YGNGV motif, and producer strain Lactobacillus plantarum LPL-1 was identified based on physio-biochemical characteristics and 16S rDNA sequence. The novel bacteriocin, plantaricin LPL-1 was purified by salt precipitation, cation exchange, gel filtration, and reverse phase high-performance liquid chromatography (RP-HPLC). The molecular mass of plantaricin LPL-1 was 4347.8467 Da by Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis and entire amino acid sequence of plantaricin LPL-1 was VIADKYYGNGVSCGKHTCTVDWGEAFSCSVSHLANFGHGKC. Plantaricin LPL-1 possessed the merits of easy degradation by proteases, wide pH stability (2–10), high thermal stability (121°C, 20 min), surfactants stability and bactericidal activity against foodborne spoilage and pathogens bacteria. The mode action and membrane permeabilization of plantaricin was identified. The information of plantaricin LPL-1 indicated that it is not only a novel class IIa bacteriocin, but also a promising natural and safe biologic preservative for the food preservation industry.

Linear stability of a contaminated fluid flow down a slippery inclined plane

The linear stability analysis of a fluid flow down a slippery inclined plane is carried out when the free surface of the fluid is contaminated by a monolayer of insoluble surfactant. The aim is to extend the earlier study [Samanta et al., J. Fluid Mech. 684, 353 (2011)] for low to high values of the Reynolds number in the presence of an insoluble surfactant. The Orr-Sommerfeld equation (OSE) is derived for infinitesimal disturbances of arbitrary wave numbers. At low Reynolds number, the OSE is solved analytically by using the long-wave analysis, which shows that the critical Reynolds number decreases in the presence of a slippery plane but increases in the presence of an insoluble surfactant. This fact ensures a destabilizing effect of wall slip and a stabilizing effect of insoluble surfactant on the long-wave surface mode. Further, the Chebyshev spectral collocation method is implemented to tackle the OSE equation numerically for an arbitrary value of the Reynolds number, or equivalently, for an arbitrary value of the wave number. At moderate Reynolds number, wall slip exhibits a stabilizing effect on the surface mode as opposed to the result in the long-wave regime, while the insoluble surfactant exhibits a stabilizing effect on the surface mode as in the result of the long-wave regime. On the other hand, at high Reynolds number, both wall slip and insoluble surfactant exhibit a stabilizing effect on the shear mode. Further, it is shown that both surface and shear modes compete with each other to dominate the primary instability once the inclination angle is sufficiently small. In addition, new phase boundaries are identified to differentiate the regimes of surface and shear modes.

Enhanced electromagnetic interference shielding and mechanical properties of foamed epoxy nanocomposites containing carbon nanofiber treated with silicone surfactant

ABSTRACTThermosetting epoxy (EP)‐based composites containing various carbon nanofiber (CNF) contents (0–5 wt %) were fabricated using high speed mechanical stirring and surfactant assisting method. Then EP/CNF composites were foamed through a supercritical CO2 (scCO2) foaming method. The cellular morphology of the foamed EP/CNF nanocomposites has been analyzed by scanning electron microscopy (SEM), and the results demonstrated that the CNFs could be served as heterogeneous nucleating agent to increase nucleation sites in nanocomposites, leading to higher cell density and larger cell size. The influences of foaming on conductivity and electromagnetic interference (EMI) shielding effectiveness (SE) were investigated. Due to the introduction of microcellular structure, the conductivity was improved from 9.53 × 10−8 S/cm to 6.75 × 10−6 S/cm and the EMI SE was enhanced from 12.7 to 16.5 dB at the CNF content of 5 wt %. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46833.

Interactions between kaolinite clay and AOT

Interactions between kaolinite (KGa-2) and a typical anionic surfactant bis(2-ethylhexyl) sulfosuccinate sodium (AOT) have been study to obtain a better knowledge of this system. Firstly, adsorption isotherms of AOT on kaolinite are realized as a function of pH. Stability experiments have been performed between the surfactant and the clay mineral and the bed sediments structure have been studied with Small Angle X-ray Scattering (SAXS).In acidic media, the shape of the adsorption isotherm leads to the following suggestions: firstly, for surfactant concentration below the CMC a surfactant monolayer is adsorbed on the positively charged edge surfaces, and then, for surfactant concentrations above the CMC, a bilayer is adsorbed on the edge surfaces. Consequently, in the first case, the surface becomes hydrophobic and in the second case, the surface becomes hydrophilic and this assumption is verified with hydrophobicity tests. Under alkaline conditions no surfactant is adsorbed on surfaces confirming the adsorption on the edge surfaces in acidic conditions. Significant stabilization of kaolinite suspensions can be observed in the presence of high surfactant concentration, in both pH conditions. Finally, structural studies by SAXS provide data about the organization of particles in the bed sedimentation.

Purification, characterization and potential applications of a novel halotolerant metalloprotease from marine bacterium Vibrio sp. LA‐05

AbstractBACKGROUNDMany reported proteases showed low activity and stability under harsh operating conditions, e.g. high pH, salinity and surfactants, which hinders expansion of their applications in industry. Here, a novel halotolerant metalloprotease from marine bacterium Vibrio sp. LA‐05 endowed with superior properties was purified and characterized, and its industrial application also evaluated.RESULTSThe protease was active and stable at 25–40°C and pH 6.0–10.0. Moreover, it was remarkably stable in high salt solution, tolerant to denaturing agents, organic solvents, surfactants and bleaching agents, and quite compatible and stable with many commercial detergents. Its residual activities were above 22% even after co‐incubation with 20% NaCl for 480 h. Except Ariel and Tide, the residual activities were all above 55% after co‐incubation with five other liquid detergents for 240 h. The corresponding theoretical analyses show that it is a metalloprotease containing 1 mol of zinc ion per mole of protease, the mature active protease predominantly in α‐helix form consists of 321 amino acids, and the central zinc ion along with 11 other conserved and crucial amino acid residues forms the catalytic domain.CONCLUSIONThese excellent properties indicated that the protease has considerable potential as a bio‐additive in the application of detergent formulations. © 2018 Society of Chemical Industry

Influence of Monomer Composition in the Electron Beam Graft Polymerization Condition onto PET Fabrics

In recent years, PET (polyethylene terephthalate) fabrics has been widely used in many fields, such as industrial field and clothes, based on the excellent mechanical characteristics and chemical resistance. On the other hand, to introduce the new functions, the modification of these fibers and textiles by radiation induced graft polymerization has been studied. However, it is not easy to graft functional polymer chains onto PET fibers, because PET fibers possess high chemical resistance and thermal stability, as well as the relatively high resistance to radiation. We have adapted the new method of electron beam grafting using the film bag which can be vacuumed and sealed by heating the film bag to avoid exposure. This method can read to high degree of grafting by preventing the decrease of generated radicals in polymer. Emulsion grafting was tried by this film bag method. When the molecular weight ratio between the GMA (glycidyl methacrylate) conc. and the activator conc. was 180 or more, the degree of grafting was greatly improved. This phenomenon is considered as follows. At high surfactant concentrations in aqueous solution, GMA is sufficiently emulsified, and is the droplet of the stable hydrophilic surface. However, at low surfactant concentrations in aqueous solution, droplets of GMA canʼt be completely emulsified, it becomes unstable hydrophobic surface, and increase the GMA dissolved in the aqueous solution. Accordingly, it was considered that the degree of grafting was increased by the high sorption of GMA to the hydrophobic PET fibers. Also, PET film could get the high degree of grafting compared with polyethylene (PE) for the material of the film bag used as a reaction container. Because the film-bag made of polyethylene is easily generated the polymer radicals by irradiation, and therefore, the degree of grafting on fiber decrease by the monomer consumption on the films. As a result, 27％ of grafting degree was obtained at the 20 wt％ GMA emulsion with 0.3 wt％ Span 20 under the low 100 kGy dose by the vacuum sealed method using the PET film-bag.

Active or Passive On-Demand Droplet Merging in a Microfluidic Valve-Based Trap.

A microfluidic valve-based trap enabling controlled capture, release, and temporary immobilization of droplets together with on-demand merging of selected droplets is presented in this paper. The microfluidic trap technology can merge droplets passively or in active manner via a pneumatically actuated membrane. A microchip is developed with two functional units of droplet generator and merging mechanism to implement the passive or active merging performance of the microfluidic valve-based trap using a low and high surfactant concentrated continuous oil-phase.

Morphological transformations during drying of surfactant-nanofluid droplets

The effect of surfactants with different chain length on the drying dynamics of nanosized dispersion droplets and on the final morphology of the grains formed after water evaporation is investigated experimentally. An acoustic levitator was used to examine the drying dynamics of single droplets and SEM imaging was used to characterise the morphology of the final dried grains. Results show that the drying of drops with high molecular weight surfactants leads to more irregular grains and that the grain morphology is related to surface tension driven instability of the evaporating droplets which may lead to formation of hollow dried grains.

Effects of carrier on the transport and DDT removal performance of nano-zerovalent iron in packed sands

The delivery of nano-zerovalent iron (nZVI) as a remediation agent to targeted areas in soil was studied using different carriers. Among water, surfactant solution, and surfactant foam, the nZVI transport and carrying abilities followed the order of surfactant foam > surfactant solution > water. The nZVI migration was also facilitated by increased soil particle size and high surfactant concentration. Batch experiments probed the remediation of dichlorodiphenyltrichloroethane (DDT)-contaminated sand under different conditions. Compared to surfactant solution, the use of foam as a carrier achieved much higher DDT removal efficiencies for both coarse (foam/solution: 99/69%) and fine (foam/solution: 60/26%) sands. Additionally, the DDT removal efficiency was strongly influenced by surfactant concentration: foams generated using 1 and 5 g L−1 sodium lauryl ether sulfate (SLES) solutions reached the respective efficiencies of 44% and 75% under identical experimental conditions. However, the nature of the surfactant did not significantly affect the total removal efficiency of DDT. Solubilization, increased sweep efficiency, and reduction by nZVI were identified as factors affecting the DDT removal efficiency, and all three of them were involved when foam-nZVI was used as the flushing fluid.

Enhancement mechanism of high alcohol surfactant on spray cooling: Experimental study

The addition of surfactant is considered as an important method for heat transfer enhancement in spray cooling based on numerous advantages such as less demand, significant effect and stable performance. Recent studies have found that high alcohol surfactant has a significant effect on the heat transfer in spray cooling. In this study, the effect of four kinds of high alcohol surfactants, 1-heptanol, 1-octanol, isooctanol and n-decanol, on spray cooling heat transfer using water as the working medium was studied experimentally. It was found that there exists an optimal concentration for each surfactant to achieve the best heat transfer performance. Under the experimental conditions, the optimal value of 1-heptanol was 0.3‰, heat dissipation flux reached 180.9 W/cm2, and the heat transfer increased by 20.9%; the best value of 1-octanol was 0.3‰, heat dissipation flux reached 200.8 W/cm2, and the heat transfer increased by 34.2%; the best value of isooctanol was 0.5‰, heat dissipation flux reached 185 W/cm2, and the heat transfer increased by 23.7%; the best value of n-decanol was 0.1‰, heat dissipation flux reached 180.7 W/cm2, and the heat transfer increased by 20.8%. To further analyze the enhancement mechanism, this paper also studied the influence of surfactant concentration on physical properties of working fluid and the spray characteristics. The experimental results showed that the effect of surfactant on saturated vapor pressure was small, and the change became obvious at higher temperature. The tension changed obviously with the surfactant concentration, and the surface tension decreased rapidly at lower concentration. The dynamic viscosity did not vary much with the type and concentration of the surfactant. The relationship between physical properties and concentration was also obtained in experiments. After adding surfactant, droplet number was lower than that of water, the distribution of droplets at different heights was more even. Droplet diameter reduced in certain area, however it increased in the edge of the area due to local impact and fusion. The change of droplet velocity was not obvious. This paper also put forward relations between the physical properties of different working fluids and their concentration and correlations which can predict diameter and velocity of spray droplet.

Adoption of phase behavior tests and negative salinity gradient concept to optimize Daqing oilfield alkaline-surfactant-polymer flooding

A high performance surfactant formulation was developed using more universally accepted Winsor type phase behavior tests rather than relying primarily on interfacial tension (IFT) measurement for the first time for Daqing oilfield. A surfactant mixture of alkylbenzene sulfonate and fatty alcohol propoxylated ether sulfate was identified which was able to form middle-phase microemulsion with Daqing less reactive crude oil (acid number below 0.1 mg KOH/g crude), lower oil water IFT to ultralow level, and hold desired aqueous stability. Winsor type phase behavior tests at various water oil ratios (WORs) showed the optimum salinity changed slightly from 1.95% to 2% when WOR was increased from 5:5 to 9:1 due to the low reactivity of the Daqing crude oil. To investigate the significance of salinity on Daqing alkaline-surfactant-polymer (ASP) flooding, 4 salinity profiles were designed during coreflooding that corresponded to different types of microemulsions including III–III–I, I–III–I, II–III–I, and III–III–III. For each coreflooding, 0.3 pore volume (PV) of ASP slug with 0.3% total surfactant concentration and 0.2 PV polymer drive was injected. The results demonstrated when negative salinity gradient (3.0%–2.0%–0.5% Na2CO3 in waterflood, ASP, and polymer slugs) was applied, the highest incremental oil recovery of 45.9% original oil in place (OOIP) was achieved. If no Na2CO3 was added in water preflush prior to the injection of ASP slug, the lowest incremental recovery of 32.8% OOIP was observed. For a constant salinity profile at optimum salinity, an intermediate oil recovery (37.4%) was encountered. The measurement of surfactant and Na2CO3 concentrations in the effluents indicated that when negative salinity gradient (II–III–I) was applied, the surfactant loss in the porous media and the oil phase was moderate compared to the two corefloods with III–III–III (highest surfactant loss) emulsion and I–III–I emulsion (lowest surfactant loss). This implied that at optimized salinity profile, the surfactants were more close to hydrophobic-hydrophilic balance during the propagation in the reservoir, which showed the highest potential of increasing oil recovery for the Daqing Oilfield without significantly increasing chemical consumption.

MoSe2 Dispersed in Stabilizing Surfactant Media: Effect of the Surfactant Type and Concentration on Electron Transfer and Catalytic Properties.

Layered transition metal dichalcogenides (TMDs) have gained attention from the scientific community because of their extended range of applications. Molybdenum diselenide (MoSe2) has been proven to be an efficient catalyst for the hydrogen evolution reaction (HER), having implications in the research of new catalysts for clean energy production. One way to produce large quantities of these materials involves the use of surfactants for liquid exfoliation. Herein, we investigate the effects of cationic, anionic, and nonionic surfactants within a concentration range on the heterogeneous electron transfer rates, electrocatalytic efficiency toward the HER of MoSe2, and on the stability of the dispersions. We found that surfactants can have a detrimental effect on the electrocatalytic properties of the material when used above a concentration threshold. In some cases, high surfactant levels also had a negative effect on the stability of the material. This report serves to gain an understanding on how the way TMDs are prepared, processed, and stabilized can have dramatic effects on their efficiency toward HER, one of their most popular applications, and how choosing the appropriate surfactant type and concentration is crucial to gain in stability without compromising the intrinsic properties of the material.