Comparative Study of Extensional Viscoelasticity Properties of Liquid Films and Stability of Bulk Foams

The extensional viscoelasticity modulus and conductivity of liquid films and stability of bulk foams were investigated respectively. The effects of sinusoidal exciting frequency, polymer type, and polymer concentration on liquid film viscoelasticity modulus were systematically discussed. Higher film viscoelasticity modulus could be assigned for FS01/MPAM film systems than for FS01/HPAM ones. The film conductivity result showed that FS01/HPAM or FS01/MPAM liquid film systems could delay the liquid drainage speed under dynamic conditions compared with FS01 ones. Bulk foam test based on Waring Blender method indicated that FS01/HPAM foam was more stable than FS01/MPAM. Compared with static bulk foam test, the extensional viscoelasticity and conductivity method could reflect the dynamic behavior of liquid films.     

Influence of Foam Apparent Viscosity and Viscoelasticity of Liquid Films on Foam Stability

The objective of this research work was to study the relationship among the apparent viscosity of bulk foam, the viscoelasticity of liquid films, and foam stability. Bulk foam tests showed that the drainage half-life of AOS foam was higher than that of sodium dodecyl sulfate (SDS) and hexadecyltrimethyl ammonium bromide (CTAB) foams. The results of foam apparent viscosity revealed that the foam apparent viscosity was related to foam quality rather than foam stability. Higher film viscoelasticity modulus could be assigned for α -olefin sulfonate (AOS) films than those for SDS and CTAB ones. The film conductivity tests indicated that AOS liquid films, compared with SDS and CTAB liquid films, could delay the liquid drainage speed under dynamic conditions. Compared with foam apparent viscosity, the viscoelasticity of liquid films appeared to be a key factor in foam stability.     

Influence of polymers on dust-related foam properties of sodium dodecyl benzene sulfonate with Foamscan

Foamability, liquid holdup, and foam appearance are key factors that determine dust control efficiencies. As the foam production method of the FoamScan instrument is similar to foaming device used for dust control, and its measurement means can satisfy the requirements of precise measuring, the FoamScan technology is adopted to explore the influence of xanthan gum (XG) and partial hydrolytic polyacrylamide (HPAM) on dust-related foam properties of sodium dodecyl benzene sulfonate (SDBS). It was found that with the increase of the polymer mass fraction, the liquid volume in the foam gradually increased. Additionally, the foaming time t₂₀₀ of the foaming agent decreased at first, then remained almost constant for both polymers, which indicated that the foamability and liquid holdup were enhanced by the addition of polymers into SDBS. In addition, the efficiencies of XG are higher than that of HPAM. The image analysis using the CSA software revealed that the mean radius formed by XG was smaller than that by HPAM and the number of bubbles was larger with XG than with HPAM. Thus, the XG foam has more area to contact with dust and could control dust better. The highly branched molecular structure and hydrogen bonds formed by XG played important roles in dust-related foam properties.     

改性二氧化硅纳米颗粒提高二氧化碳泡沫稳定性的研究

通过纳米二氧化硅的硅烷化改性, 使其在高矿化度盐水中可以稳定存在的前提下, 研究了改性纳米颗粒与阳离子表面活性剂十二烷基三甲基氯化铵混合体系的溶液稳定性及协同稳定CO₂泡沫的效果. 研究结果表明, 无机盐离子对改性纳米颗粒与阳离子表面活性剂间的静电吸引力具有屏蔽作用, 且矿化度越高, 屏蔽效果越明显, 从而混合溶液更易于在高盐水中稳定; 纳米颗粒表面的活性剂吸附层受二者浓度的影响, 进而影响了颗粒的亲/疏水性; 当混合体系中的表面活性剂浓度低于临界胶束浓度(CMC)时, 混合溶液与CO₂的界面张力高于单独活性剂溶液, 而当活性剂浓度高于CMC时, 对CO₂-溶液界面张力几乎无影响, 最低界面张力可降至6 mN/m左右; 改性纳米颗粒的加入可以进一步提高CO₂体相泡沫半衰期一倍以上, 但受二者浓度比例的影响; 纳米颗粒的加入有效提高了多孔介质中泡沫的表观黏度, 最大增幅由20 mPa·s增至55 mPa·s左右, 泡沫黏度增加接近3倍, 增强了CO₂泡沫驱的封堵作用.     

Change of Surface Structure upon Foam Film Formation

The charge distribution and coverage with surfactant molecules at foam film surfaces plays an important role in determining foam film structure and stability. This work uses the concentration depth profiling technique neutral impact collision ion scattering spectroscopy to experimentally observe the charge distribution in a foam film for the first time. The charge distribution at the surface of a foam film and the surface of the corresponding bulk liquid were measured for a cationic surfactant solution and the surface excess as well as the electric potential were determined. Describing the internal pressure of foam films by using the electrochemical potential is introduced as a new concept. The foam film can be seen to have a more negative surface charge compared to the bulk liquid surface due to re‐arranging of the surfactant molecules. It is discussed how the change in surface excess and electric potential change the electrochemical potential and the stability of the foam film.     

Dilational Rheology at Air/Water Interface and Molecular Dynamics Simulation Research of Hydroxyl Sulfobetaine Surfactant

Hydroxyl sulfobetaines with hexadecyl-, octadecyl-hydrophobic chain and an industrial product hydroxyl sulfobetaine were synthesized from analytical-grade and industrial-grade tertiary amine, respectively. The dilational properties and surface tension of the three surfactants at the water-air interface were investigated by drop shape analysis and ring method. The influences of oscillating frequency and bulk concentration on dilational properties were explored. The experimental results show that the dilational module of octadecyl-hydroxyl sulfobetaine was higher than hexadecyl hydroxyl sulfobetaine and the dilational elastic component of the three surfactants were higher than dilational viscous component. Furthermore, the dilational elastic component of mixed surfactant system shows two maxima in a lower concentration than that of single surfactant system. As a result, the surface tension of mixed surfactant system reaches to minimum value in a lower concentration compared with single surfactant system. The simulation results show that the hydrophobic chains in the mixed betaine solution were more curled than in single-component betaine solution ascribed to stronger interaction among different hydrophobic chains, resulting to a more compact interfacial film.     

Effect of alkyl chain length on the surface dilational rheological and foam properties of N-acyltaurate amphiphiles

The dynamic dilational properties of sodium 2-(2-(alkylaryloxy)-alkylamido)ethanesulfonates (12+nB-Ts) at the air–water interfaces were investigated by drop shape analysis, and their foam properties were also measured. The influences of time and bulk concentration on surface dilational properties were expounded. The results show that the molecular interaction controls the nature of adsorption film during lower concentration range, and the film behaves elastic in nature. During higher concentration range, the diffusion exchange process controls the dynamic dilational properties and the surface film shows remarkable viscoelasticity. An increase in hydrophobic chain length enhances the molecular interaction at low concentration and speeds up the diffusion exchange process at high concentration, which results in the different variations of modulus at different concentration regions. For 12+nB-Ts, too short a chain probably produces bad film elasticity, whereas too great a length produces too fast liquid drainage. Therefore the optimal length in the branched chain leads to the best foam stability.     

Drainage of aqueous film-forming foam stabilized by different foam stabilizers

The present study focuses on the drainage property of aqueous film-forming foam stabilized by different types and concentrations of foam stabilizers. Aqueous film-forming foam (AFFF) formulation concentrates are prepared based on the main components of fluorocarbon surfactant, hydrocarbon surfactant, and organic solvents. Carboxymethylcellulose sodium (CS), xanthan gum (XG), and lauryl alcohol (LA) are selected as foam stabilizers of the AFFF. Surface tension, viscosity, and foamability tests of the AFFF solutions are conducted to evaluate the effect of foam stabilizers on the properties of AFFF solutions. Particularly, an apparatus is established based on the law of connected vessel in order to obtain the instantaneous mass of liquids drained from foams. The drainage features of the AFFFs containing different foam stabilizers are analyzed and compared with each other. The results indicate that AFFF drainage is significantly affected by the type and the concentration of foam stabilizers. The addition of CS and XG to AFFF results in a deceleration of foam drainage, while foam drainage is accelerated by the addition of LA. The variations of surface tension, viscosity, and liquid fraction of foams are the main reasons for the varying foam drainage rate. This study provides a direct connection between chemical components and fundamental properties of AFFF.     

Investigation on properties of aqueous foams stabilized by aliphatic alcohols and polypropylene glycol

Foams stabilized by nonionic surfactants are usually moderately stable due to high drainage rate and intense bubble coalescence and coarsening. This study aimed to investigate comparatively the foam properties of aliphatic alcohols (methyl isobutyl carbinol (MIBC) and 2-octanol) and polypropylene glycol (PPG400). Experiments were conducted using the FoamScan method at various surfactant concentrations and gas flow rates where the foam volume, liquid content of foam and foam half-life were determined. The results showed that both foamability and foam stability of surfactant solution increased with increasing gas flow rate and surfactant concentration for all tested surfactants. PPG400 was an unusually strong surfactant having the largest surface activity compared with MIBC and 2-octanol, which exhibited the maximum foaming performance and foam stability at all tested gas flow rates and concentrations. The present study suggested that foam properties depended primarily on the type of surfactant and its concentration and secondarily on the gas flow rate. In addition, properties of interface are closely related to that of foam, which is a significant point if one wants to produce foams for specific applications.     

Removal of Mercury by Emulsion Liquid Membranes: Studies on Emulsion Stability and Scale Up

Emulsion liquid membranes (ELM) have received significant attention in the separation of various metal ions from industrial wastewater. Still efforts are needed to get the desired level of stability to overcome the hindrance in the application of ELM at industrial scale. In this paper, the effects of various parameters such as emulsification speed, concentration of cosurfactant, surfactant, carrier and impeller speed during extraction on the stability of an emulsion liquid membrane are studied. Dispersion destabilization of w/o emulsion is checked by Turbiscan. Drop size distribution and photomicrographs of the emulsions are also analyzed to evaluate stability of the emulsion. Instability of emulsion liquid membrane during extraction process is measured in terms of membrane breakage. A stable emulsion is used for the extraction of mercury from aqueous solution in small scale as well as in large scale.     

Rheological Properties of Zwitterionic Wormlike Micelle in Presence of Solvents and Cosurfactant at High Temperature

Rheological properties of wormlike micelle solutions of zwitterionic surfactant were studied as a function of cosurfactant, organic salt, and solvents at high temperature. Addition of cosurfactant and organic salt increases the viscoelasticity at high temperature. Addition of isopropanol as solvent shifts the maximum viscosity of wormlike micelle to lower temperature. Addition of propylene glycol as solvent has less effect on the viscoelasticity of the wormlike micelle solution. An analysis based on the polarity of the solvent and phase behavior in concentrate region explains the effect of solvents on worm-like micelle.     

Equilibrium and Dynamic Surface Tension of Carboxymethylchitosan and Alkyl Trimethylammonium Bromide Mixtures

A water-soluble derivative of chitosan, carboxymethylchitosan (CMCH), was mixed with alkyltrimethylammoniumbromides (C_mTAB) and was studied on the adsorption at air/water interface using equilibrium and dynamic surface tension method. The effects of surfactant and polymer concentrations, surfactant chain length, as well as pH of solution were investigated. Addition of the surfactants remarkably promotes the polymer adsorption. Increasing any one of surfactant concentration, surfactant chain length, and pH will facilitate the adsorption of the mixture whereas little effects of polymer concentration were observed. The results are explained in terms of the interaction between CMCH and C_mTAB under different conditions.     

Foaming,foam films,antifoaming and defoaming

A general introduction to foams, the initial stages in the production of foams in aqueous solution, foam structures and the classification of bulk foams according to their lifetimes and stability are presented. Fundamental studies on horizontal and vertical isolated foam lamellae with emphasis on drainage and stability are reviewed. For freshly prepared foams containing fairly thick lamellae, the mechanical-dynamical properties of the surface adsorbed layers (surface tension gradients) are decisive for retaining stability. Important parameters to be taken into consideration are the surface elasticity, viscosity (bulk and surface), gravity drainage and capillary suction. Also the film should exhibit low permeability to gases. Providing the stability of a foam film (containing dilute surfactant) is retained during the initial dynamic drainage process, then eventually a static (equilibrium) situation will be reached at film thicknesses < 100 nm. In this region, interfacial interactions dominate and the stability of the film must be discussed in terms of the intermolecular forces (electrostatic double layer repulsion, dispersion force attraction and steric forces). This may lead to the formation of common black and Newton black films and these structures have been shown to be resilient to rupture and have low gas transfer characteristics. At high surfactant concentrations (>c.m.c.) stabilization of films and foams can occur by a micellar laying mechanism (stratification). Antifoaming and defoaming theories are presented, together with the mechanisms of heterogeneous antifoaming agents (non-polar oil, hydrophobic solid particles or mixtures of both) including recent theories describing the role of the emulsion and pseudo-emulsion film in the stability of foams containing oil droplets. Finally, defoaming by ultrasonic waves is briefly reviewed.     

Enhanced heavy oil recovery by organic alkali combinational flooding solutions

Although alkaline/surfactant/polymer (ASP) flooding is successfully applied in oil fields, some disadvantages such as scales, corrosion effects, and viscosity reductions of polymer solutions appear. Usage of organic alkalis can avoid or decrease these disadvantages. In this paper, the physicochemical properties, including interfacial tension (IFT), and viscosity, of organic alkali combinational flooding solutions and their effectiveness as enhanced oil recovery agents are investigated. Monoethanolamine (MEA) is the optimal one for decreasing the IFT among the three organic alkalis studied in this paper. Although MEA cannot decrease the IFT as low as NaOH does, it has good compatibility with both surfactant and the polymer hydrolyzed polyacrylamide (HPAM). MEA not only helps a surfactant solution or HPAM/surfactant mixture attain ultralow IFT values, but can also promote better viscosity stability for HPAM or HPAM/surfactant solutions compared to NaOH. Moreover, core flood experiments show that adding MEA can obtain additional tertiary oil recovery of 6%–10% original oil in place (OOIP) on the top of HPAM or HPAM/surfactant flooding, although MEA has a lower enhanced oil recovery than NaOH. The experimental results show that MEA is a good choice to replace NaOH in enhancing heavy oil recovery.     

Surfactant mixtures for control of bubble surface mobility in foam studies

A new class of surfactant mixtures is described, which is particularly suitable for studies related to foam dynamics, such as studies of foam rheology, liquid drainage from foams and foam films, and bubble coarsening and rearrangement. These mixtures contain an anionic surfactant, a zwitterionic surfactant, and fatty acids (e.g., myristic or lauric) of low concentration. Solutions of these surfactant mixtures exhibit Newtonian behavior, and their viscosity could be varied by using glycerol. Most importantly, the dynamic surface properties of these solutions, such as their surface dilatational modulus, strongly depend on the presence and on the chain-length of fatty acid(s). Illustrative results are shown to demonstrate the dependence of solution properties on the composition of the surfactant mixture, and the resulting effects on foam rheological properties, foam film drainage, and bubble Ostwald ripening. The observed high surface modulus in the presence of fatty acids is explained with the formation of a surface condensed phase of fatty acid molecules in the surfactant adsorption layer.     

泡沫的稳定性及液晶对它的影响

泡沫体系的表面张力、粘度,表面粘度以及液晶相的存在对泡沫的稳定性皆有影响。消泡剂可改变上述性质。本文报导聚氧乙烯辛基酚(TritonX-100),十二烷基硫酸钠(SDS),油酸三乙醇胺(TEAOL)和卵磷脂等起泡剂在均相溶液及有液晶存在时产生泡沫的稳定性,观察硅油的消泡作用。     

Effect of Surfactant Chain Length on the Rheological Properties of Cationic Surfactants and a Hydrophobic Counterion

The rheological behavior of alkyimethylammonium 2-hydroxy-1-carboxy-naphthoate, C_xTA-2.1-HCN (x = 16, 14, 12, 10, and 8) is presented. With increasing 2.1 HNC/C_xTAOH (x = 16, 14, 12) ratio, the viscoelasticity of the solutions changes due to a transition in the micellar shape from small micelles to rodlike micelles and finally to multilamellar vesicles (MLV). On the other hand, a transition from small micelles to multilamellar vesicles (MLV) was observed for solution with C_xTA-2.1-HCN (x = 10 and 8). The MLV phases behave like a weak gel and have a yield stress value. Rheological measurements were performed for these viscoelastic systems in order to find out the dependency of the viscoelastic behavior on the surfactant chain length and hydrophobic counterion concentration. Some theoretical models as reptation mechanism was also applied in order to get some structural details and to illustrate the rheological behavior of these viscoelastic systems. Some models that correlate MLV-modulus on the surfactant morphology are also presented and discussed.     

Effects of a Novel Organic Alkali on the Interfacial Tension and Emulsification Behaviors Between Crude Oil and Water

Experiments have been carried out to investigate the interfacial tension (IFT) and emulsification behaviors between Shengli crude oil and a novel organic alkali (OA). The dynamic IFT and minimum IFT are adopted to characterize the IFT behaviors; the microscopic method, Turbiscan stability index, separated water rate, and laser particle size analysis method are used to show the emulsification behaviors. The dynamic and minimum IFT both decrease continuously with the increase of OA concentration whether surfactant is added or not; because of the synergy of OA and surfactant, the minimum IFT will be reduced to the ultralow value. The synergy is also crucial for the crude oil emulsification. When OA and surfactant are used together, owing to the mosaic and cross-multiple adsorption of OA, surfactant and in situ soap at the interfacial film, the oil can be emulsified more easily, the quantity of emulsified droplets is higher, and the emulsion is more stable with OA concentration increases. The relationship of the minimum IFT and emulsification is investigated; it indicates that the emulsion stability improves, the degree of dispersed homogeneity of oil droplets increases, and the median diameter of emulsified oil droplets decreases with the decline of the minimum IFT.     

Disruption of viscoelastic beta-lactoglobulin surface layers at the air-water interface by nonionic polymeric surfactants

Nonequilibrium interfacial layers formed by competitive adsorption of beta-lactoglobulin and the nonionic triblock copolymer PEO99-PPO65-PEO99 (F127) to the air-water interface were investigated in order to explain the influence of polymeric surfactants on protein film surface rheology and foam stability. Surface dilatational and shear rheological methods, surface tension measurements, dynamic thin-film measurements, diffusion measurements (from fluorescence recovery after photo bleaching), and determinations of foam stability were used as methods. The high surface viscoelasticity, both the shear and dilatational, of the protein films was significantly reduced by coadsorption of polymeric surfactant. The drainage rate of single thin films, in the presence of beta-lactoglobulin, increased with the amount of added F127, but equilibrium F127 films were found to be thicker than beta-lactoglobulin films, even at low concentration of the polymeric surfactant. It is concluded that the effect of the nonionic triblock copolymer on the interfacial rheology of beta-lactoglobulin layers is similar to that of low molecular weight surfactants. They differ however in that F127 increases the thickness of thin liquid films. In addition, the significant destabilizing effect of low molecular weight surfactants on protein foams is not found in the investigated system. This is explained as due to long-range steric forces starting to stabilize the foam films at low concentrations of F127.     

起泡剂/稳泡剂/SiO2复合泡沫缓速酸液体系协同增效性能

为了有效控制液相中H⁺向岩石表面的扩散,降低酸-岩反应速率,进而达到深度酸化刻蚀的目的,通过对纳米颗粒、稳泡剂与表面活性剂协同增效作用的研究,制备了一种泡沫稳定、耐温性能及缓速性能优异的泡沫缓速酸。室内通过对比不同纳米材料在酸液中的分散性能及纳米颗粒粒径对泡沫缓速酸性能的影响,优选出d=25 nm的亲水型Si O₂纳米材料。采用自制的两性表面活性剂(MAC)作为起泡剂,并加入自制的酸液稠化剂(SY-1)作为稳泡剂以达到稳泡作用。当w(Si O₂)=1.5%、w(MAC)=1.0%、w(SY-1)=0.08%时,所形成的泡沫也更加致密,液膜厚度增强,泡沫稳定性提高,半衰期延长,从7 min增长到69 min;并且SY-1的加入提高了泡沫的耐高温性能,使体系在90℃时半衰期仍然能达到29 min。通过测定不同条件下酸岩反应速率并进行比较,结果表明,20%HCl基液的平均酸岩反应速率为1.148×10^-3 mg/(cm²·s),而实验室自制泡沫缓速酸液体系的平均酸-岩反应速率降至7....