Foaming of nonionic surfactant solutions: Effect of surfactant concentration and temperature

Foaming of solutions of the nonionic surfactant, octoxynol 9, was investigated in the concentration range of 0.010 to 5.00% and in the temperature range of 7–37 C, well below the cloud point of 65 C, by measuring the height and stability of foams generated by pouring thin streams of surfactant solutions into a glass column. All foams were fast-thinning. Their height increased monotonically with surfactant concentration. The rate of change of foam height with log surfactant concentration underwent no change at the CMC of 0.018%, but was four times lower above 0.146% than below 0.146%. Foams at lower temperatures generally thinned somewhat more slowly and were stronger or more cohesive and more stable than foams generated at higher temperatures by surfactant solutions of comparable concentrations. Oxidative degradation reduced foam height somewhat. Octoxynol 9 and sodium lauryl sulfate, rated as a good foamer, produced foams of comparable volume and stability.     

Experimental Investigation of the Mechanism of Foaming Agent Concentration Affecting Foam Stability

With the aim of determining the effect of foaming agent concentration (FAC) on foam stability, the half‐life of a selection of typical foaming agents was investigated at different concentrations using the FoamScan^® instrument. The surface tension of the bulk solution after foaming was tested using a surface tension meter. The FAC had a significant effect on foam stability at concentrations <1%, and a weak relationship at concentrations >1%. A significant turning point in the plot of foam stability versus FAC indicated maximum foam stability. The concentration at this point was defined as the optimal stability concentration, which is a guide in foam application. The micelles were thermodynamically unstable at low concentrations and degraded into surfactant solution, but were extremely stable at high surfactant concentrations that did not affect the stability of the foam. A turning point was also observed in the plot of surface tension versus FAC, beyond which the surface tension remained constant; the concentration at this point was defined as the no spherical micelle concentration. The influence of FAC on foam stability is explained in terms of mean bubble diameter (d_mb) and bubble size distribution.     

辛硫磷微乳剂浊点的影响因素分析

配制了10％辛硫磷微乳剂,研究了体系中复配表面活性剂、助表面活性剂及电解质对微乳剂浊点的影响.结果表明:可用浊点法筛选出HLB值较高的表面活性剂,再结合微乳剂性能指标确定出适合体系的复配表面活性剂.微乳剂的浊点随复配表面活性剂中非离子表面活性剂含量的增多而升高,但制剂冷贮稳定性能下降.助表面活性剂的种类和含量对微乳剂浊...     

Relationship between foaming properties and solution properties of protein/nonionic surfactant mixtures

The foaming properties of bovine serum albumin (BSA), in the absence and presence of Triton X-100 (TX-100), have been investigated using shaking tests. The results showed that increases in the TX-100 bulk concentration rapidly reduced both foam height and foam stability at TX-100 concentrations below about 0.25 mM, but increased foam height and foam stability at TX-100 concentration above 0.3 mM. The interaction between BSA and TX-100 has been studied using fluorescence spectroscopy. The surfactant appeared to bind to BSA with a low molar ratio (about one surfactant molecule per protein molecule) at concentrations below the critical micelle concentration (CMC); the binding became weaker at concentrations above the CMC. It was confirmed that protein-protein or protein-surfactant interactions had significant influence upon foaming properties of mixed protein/surfactant system.     

Mechanism of antifoam behavior of solutions of nonionic surfactants above the cloud point

Aqueous solutions of nonionic surfactants exhibit low foaming above their cloud point, a temperature above which the homogeneous solutions separates into two phases: a dilute phase containing a low surfactant concentration and coacervate phase containing a very high surfactant concentration (e.g., 20 wt% surfactant). In this work, foam formation was measured for the dilute phase, the coacervate, and the mixed solution using the Ross-Miles method for nonylphenol polyethoxylates with 8, 9, or 10 ethylene oxide moieties per molecule. The dilute phase showed no antifoam effect above the cloud point if the coacervate phase was not present, and the coacervate phase foamed little in the absence of the dilute phase. The coacervate phase acts as an oil droplet antifoam to the dilute phase. From surface and interfacial tension data, entering, spreading, and bridging coefficients for this system make it appear probable that the coacervate phase is forming bridges across the film lamellae of the dilute-phase foam and acting to suppress foam formation through the bridging mechanism.     

Phase behavior and detergency study of lauryl alcohol ethoxylates with high ethylene oxide content

Nonionic surfactants such as fatty alcohol ethoxylates have been extensively used in many detergent applications, because of their high calcium ion tolerance, low critical micelle concentrations, and mildness. Although ethoxylates containing high ethylene oxide (EO) content (EO>10 moles) score higher than their low-FO counterparts on many of these desired properties, they have not been studied adequately in the context of detergency, primarily because their cloud points (CP) are higher than normal wash temperatures, typically >100°C, and thus cannot be measured. However, once the CP are manipulated appropriately using salting-out electrolytes, these surfactants can offer certain distinct advantages in terms of their molecular and phase structure. We have studied the phase structure and clouding behavior of tetradecyl ethylene-oxide mono dodecyl alcohol (C₁₂EO₁₄), a broad-range ethoxylate, as a function of the concentrations of various electrolytes. We found that, beyond a certain critical concentration, the CP decreases monotonically with increasing salt concentration. For sodium salts of various anions, the CP depression is inversely proportional to the lyotropic number of the anion. Similarly, for chloride salts of various cations, CP depression is inversely proporitional to the lyotropic number of the cation However, the effect of changing anion is stronger than that of changing cation. A micrograph of a water penetration scan at room temperature indicates the presence of isotropic L₁; hexagonal, isotropic L₂; and solid phases with increasing surfactant concentration. As is the case with low-FO nonionics, a maximum in detergency of model oily soils was found to correlate well with the minimum in oil/water interfacial tension when plotted vs. temperature. Ross Miles foam height increases with increasing concentration of salt.     

添加剂的浓度对非离子表面活性剂AEO9浊点的影响

各类添加剂都能对非离子表面活性剂的浊点产生影响.今研究了离子型表面活性剂、增溶物和电解质类添加剂在不同浓度下对非离子表面活性剂AEO9浊点的影响.其中离子型表面活性剂和增溶物类添加剂可在极低的浓度上改变AEO9的浊点,且随着添加剂加入浓度的增加,AEO9的浊点也逐渐增加,当添加剂浓度达到离子型表面活性剂或增溶物的临界胶束浓度时,AEO9的浊点将出现急剧上升.而电解质类添加剂对AEO9浊点的影响表现出具有临界浓度现象,只有当添加剂的浓度达到相应的临界浓度之后,具有盐析效应的电解质将使AEO9浊点线性下降,而具有盐溶效应的电解质则使AEO9浊点线性升高,且不同电解质相应的临界浓度随着其阴离子的感胶离子数的增大而线性增加,同时其对AEO9浊点的改变程度则随着阴离子的感胶离子数的增大而线性下降.     

Influence of Hydrocarbon Chain Branching on Foam Properties of Olefin Sulfonate with FoamScan

The influence of surfactant structure on foam properties of internal olefin sulfonate (IOS) and alpha olefin sulfonate (AOS) in aqueous solutions was estimated from measurements of the foamability, foam stability, and foam morphology, as obtained from conductivity and image analyses techniques. It was found that the foamability and foam stability of C_16–18 AOS are higher compared to that of C_16–18 IOS, indicating that hydrocarbon chain branching decreases the foamability and foam stability. The foamability and foam stability are enhanced with increasing surfactant concentration, which increases the adsorbed quantity of surfactant molecules at the air–water interface. The influence of hydrocarbon chain branching on foam morphology was also investigated. It was found that foam cells produced by branched chain C_16–18 IOS are larger than the foam cells generated by straight chain C_16–18 AOS.     

Effect of formation of calcium carbonate on foam stability in Neodol 25-3S anionic surfactant systems

The effect of oils and hardness on stability of foams made from solutions containing 0.01 wt% of three EO alcohol ethoxysulfate sodium salt of commercial anionic surfactant Neodol 25-3S was investigated. When dissolved calcium was present under alkaline conditions using Na₂CO₃ instead of NaOH as a pH regulator, solid CaCO₃ precipitated. It was found in the absence of oil that CaCO₃ particles did not destabilize foam, in contrast to those of the more hydrophobic calcium oleate. The rate of collapse of a foam column was also measured for foams generated from alkaline solutions of an anionic surfactant Neodol 25-3S containing dispersed drops of n-hexadecane, triolein, or mixtures of these oils with small amounts of oleic acid. Oils were added in increments up to oil to surfactant ratio of 1 on a weight basis and the hardness and pH of the aqueous solutions were fixed at 300 ppm and 9 respectively. It was found that triolein has almost no defoaming effect, but the defoaming effect of hexadecane was evident. The same trend was found with mixtures of n-hexadecane/triolein with addition of small amounts of oleic acid. The results of foam stability measurement in the presence of oil could be understood in terms of entry, spreading and bridging coefficients, i.e., ESB analysis. Moreover, as the initial concentration of carbonate ions increased, foam stability was greatly improved for both hexadecane/oleic acid and triolein/oleic acid oils. Evidently, CaCO₃ precipitated preferentially, reducing the number of calcium ions available to form calcium oleate.     

Stabilization of natural gas foams using different surfactants at high pressure and high temperature conditions

Natural gas foam can be used for mobility control and channel blocking during natural gas injection for enhanced oil recovery, in which stable foams need to be used at high reservoir temperature, high pressure and high water salinity conditions in field applications. In this study, the performance of methane (CH₄) foams stabilized by different types of surfactants was tested using a high pressure and high temperature foam meter for surfactant screening and selection, including anionic surfactant (sodium dodecyl sulfate), non-anionic surfactant (alkyl polyglycoside), zwitterionic surfactant (dodecyl dimethyl betaine) and cationic surfactant (dodecyl trimethyl ammonium chloride), and the results show that CH₄-SDS foam has much better performance than that of the other three surfactants. The influences of gas types (CH₄, N₂, and CO₂), surfactant concentration, temperature (up to 110°C), pressure (up to 12.0 MPa), and the presence of polymers as foam stabilizer on foam performance was also evaluated using SDS surfactant. The experimental results show that the stability of CH₄ foam is better than that of CO₂ foam, while N₂ foam is the most stable, and CO₂ foam has the largest foam volume, which can be attributed to the strong interactions between CO₂ molecules with H₂O. The foaming ability and foam stability increase with the increase of the SDS concentration up to 1.0 wt% (0.035 mol/L), but a further increase of the surfactant concentration has a negative effect. The high temperature can greatly reduce the stability of CH₄-SDS foam, while the foaming ability and foam stability can be significantly enhanced at high pressure. The addition of a small amount of polyacrylamide as a foam stabilizer can significantly increase the viscosity of the bulk solution and improve the foam stability, and the higher the molecular weight of the polymer, the higher viscosity of the foam liquid film, the better foam performance.     

烷基糖苷的泡沫扫描研究

采用泡沫扫描方法全面研究了APG质量浓度、N2流量和NaC l质量浓度对APG泡沫性能的影响。结果表明,在1000 s内所有样品泡沫高度不变,稳泡性很好,除ρ(APG)=0.25 CMC泡沫时间为149 s外,其余质量浓度下发泡时间都在(144±2)s,随表面活性剂质量浓度增加,泡沫相对电导、泡沫最大密度和泡沫稳定指数值都增加。N2流量对体系发泡性能影响较大,最佳N2流量为40 mL/min。随盐含量增加发泡时间微减少,而泡沫稳定指数增加。在稳泡阶段,随时间延长和N2流量增加,泡沫数量越来越少,泡沫单个面积越来越大。盐含量高时泡沫数量较多。随表面活性剂质量浓度增加,泡沫数量增加,但泡沫总面积和平均面积减小。     

Effects of Inorganic Salts and Polymers on the Foam Performance of 1-Tetradecyl-3-methylimidazolium Bromide Aqueous Solution

The foaming performance of 1-tetradecyl-3-methylimidazolium bromide (C₁₄mimBr) aqueous solution, in the presence of polymers (PEG or PVA) or inorganic salts (NaBr, MgCl₂, NaNO₃, Na₂SO₄ or Na₃PO₄), was investigated at 25.0?°C by using the self-made apparatus and the conductivity method. The experimental results show that the foaming ability and foam stability of the ternary aqueous systems of C₁₄mimBr coexisting with PEG or PVA are stronger than those of the C₁₄mimBr solutions in the absence of a polymer, and both the efficiency of foaming ability and foam stability of the surfactant solutions are evidently enhanced with an increase in polymer concentration. However, the addition of inorganic salts can decrease the foaming ability and foam stability of C₁₄mimBr solution. Especially, the inorganic salts, with high valence state of the anion (SO₄ ^2? and PO₄ ^3?), are good antifoam agents which can remove and inhibit foam quickly. For the aqueous solution of the surfactant, the effect of temperature on foaming properties was also examined. The results show that both the foaming ability and stability of the foams of the surfactant solutions decrease with an increase in the temperature within the range from 25.0 to 45.0?°C.     

Synthesis and surface measurements of surfactants derived from dehydroabietic acid

Dehydroabietates with poly(ethylene oxide) chains of average m=12, 17, and 45 units [DeHab(E) _m ] were synthesized. The adsorption at the liquid-vapor interface was measured, and the adsorbed amount and critical micelle concentrations (CMC) were determined. The foamability, the foam stability, wetting properties, and cloud points, with and without salt content, were studied. The results were compared with common linear alkyl ethoxylates, nonylphenol ethoxylates, and cholesterol ethoxylates. The dehydroabietic acid as hydrophobe was found to result in the same CMC as a linear dodecyl chain. DeHab(E)₄₅ was found to be insoluble above 400 mg/L, but the surface tensions at lower concentrations were similar to those of the C_11–13E_38–40 surfactants, which exhibit CMC in aqueous media. The foaming behavior of the DeHab(E)₁₂ and DeHab(E)₁₇ surfactants was about the same as for common linear C _n E _m surfactants. The foamability as well as the foam stability increased with ethylene oxide (EO) chain length. The cloud point was depressed by increased salt concentration and increased with the number of EO units in the head group. The cloud point was significantly lower than for the corresponding surfactant with a dodecyl chain with similar EO chain length. The wetting results, obtained by measuring the contact angle at similar surface tensions, indicate that surfactants of the DeHab(E) _m type are more efficient wetting agents than both disaccharide sugar surfactants and C _n E _m type surfactants.     

Wetting properties of nonionic surfactants of homogeneous structure C12H25(OC2H4)xOH1

The wetting of cotton skeins by aqueous solutions of individual surfactants of structure C₁₂H₂₅(OC₂H₄ )_XOH, where x = 4-8, with homogeneous head groups, and of a Poisson distribution mixture containing an average of 5.5 oxyethylene groups, has been measured at various temperatures using the Draves technique. An individual compound with a homogeneous polyoxyethylene head group is a more effective wetting agent than a Poisson distribution mixture with the same average number of oxyethylene units. Loglog plots of wetting time vs surfactant concentration are linear in the concentration range of 0.25 to 1 g/L. The best wetting agents at any temperature have slopes in the -1.5 to -1.6 range and Y-intercepts from +0.6 to +0.7. Wetting in these systems appears to be diffusion-controlled. The wetting time at 1 g/L concentration is a measure of the wetting effectiveness of the surfactant, because it is roughly inversely proportional to the diffusion constant of the surfactant at that concentration. For materials 30 C or more below their cloud point, temperature increase causes an increase in wetting effectiveness. As the cloud point of the surfactant solution is approached, however, both the slope and the Y-intercept of the log-log plot of wetting time vs surfactant concentration change sharply. The absolute value of the negative slope decreases and the positive value of the Y-intercept increases, resulting in greatly reduced wetting effectiveness.     

Influence of anionic concentration and water hardness on foaming properties of a linear alkylbenzene sulfonate

Foam height and foam stability of solutions of a linear alkylbenzene sulfonate (LAS) were measured according to the Ross-Miles test to establish their relationship with ionic concentrations in the solution. The anionic concentration and water hardness were varied alternatively. The results obtained show different behavior for both parameters depending on the concentration of LAS and calcium. However, the results are in line with the proposed theoretical model based on the LAS-calcium precipitation boundary diagram. These tests were aimed at providing a scientific explanation to the complex foaming phenomena. Also, these tests emphasize how essential it is to know the position of the points tested within the LAS-calcium solubility diagram when evaluating the foam properties of an anionic surfactant.     

Coalescence of bubbles and stability of foams in aqueous solutions of Tween surfactants

Coalescence of air bubbles and stability of foams in aqueous solutions of Tween 20, 40, 60 and 80 are reported in this work. Adsorption of the surfactants at air–water interface was studied by measuring the surface tension of the surfactant solutions. The surface tension profiles were fitted using a surface equation of state derived from the Gibbs and Langmuir adsorption equations. The critical micelle concentration and surface tension at this concentration were determined. The effect of surfactant concentration on coalescence of air bubbles at flat air–water interface was studied. The role of steric force on coalescence time was investigated. The coalescence time distributions were fitted by the stochastic model. The mean values of the distributions were compared with the predictions of seven film-drainage models. Stability of foams was analyzed by the Ross–Miles test. The initial and residual foam heights were measured at different surfactant concentrations. The stability of foams was compared with the coalescence time of the bubbles.     

Comparative Investigation of Dynamic Foam Behavior of Air–Water and CO2–Water Systems

The purpose of this study was to understand and compare the dynamic foam behavior of the surfactant Tween‐20 in air–water and CO₂–water systems. The foam height in the CO₂–water system was less than that in the air–water system, but the foam stability was better in the CO₂–water system. The effect of temperature on axial dye displacement and foam bubble size was studied, where the foam generation ability of the surfactant was directly proportional to the temperature, while the foaminess was inversely proportional. The observed highest foam volume for the air–water system was 3922 ± 181 cm³ and for the CO₂–water system 3195 ± 181 cm³ at 5.0 g L^–1 of surfactant at air flow rate of 1 liter per minute (LPM) at 52 °C. The half‐life for the air–water and the CO₂–water system was 110 and 40 s, respectively, at 5.0 g L^–1 of surfactant at the air flow rate of 1 LPM and 28 °C. In wet foam, the liquid holdup range for the air–water system was 0.38–0.52% and for the CO₂–water system 0.51–0.72% in the concentration range 1.0–5.0 g L^–1 at 1 LPM gas flow rate.     

Experimental Study on Foam Properties of Mixed Systems of Silicone and Hydrocarbon Surfactants

Silicone surfactants are inevitably involved in industrial applications in combination with hydrocarbon surfactants, but properties of the mixtures of silicone and hydrocarbon surfactants have received little attention, especially foam properties of the mixtures. In this study, aqueous solutions of respective binary mixtures of a nonionic silicone surfactant with anionic, cationic, and nonionic hydrocarbon surfactants were prepared for evaluation of their foam properties. Surface tension of aqueous solutions of the mixtures were measured with the maximum bubble pressure method. Foaming ability and foam stability of the mixtures were then evaluated with the standard Ross–Miles method. The findings show that the addition of the silicone surfactant results in a decrease in surface tension for aqueous solutions of the hydrocarbon surfactants. The critical micelle concentration (CMC) of the hydrocarbon surfactants is also changed by the additive silicone surfactant. Additionally, clear foam synergistic effects were observed in the mixtures of silicone and hydrocarbon surfactants, regardless of the ionic types of the hydrocarbon surfactant. The foam stability of the hydrocarbon surfactant was shown to generally improve with the increasing concentration of the silicone surfactant. Even so, aqueous solutions of different ionic hydrocarbon surfactants in the presence of the silicone surfactant will give different foam stabilities. The results of the present study are meant to provide guidance for the practical application of foams generated by the mixtures of the silicone and hydrocarbon surfactants.     

Surfactant Recovery from Water Using Foam Fractionation

Abstract

The purpose of this study was to investigate the use of foam fractionation to recover surfactant from water. A simple continuous mode foam fractionation was used and three surfactants were studied (two anionic and one cationic). The effects of air flow rate, foam height, liquid height, liquid feed surfactant concentration, and sparger porosity were studied. This technique was shown to be effective in either surfactant recovery or the reduction of surfactant concentration in water to acceptable levels. As an example of the effectiveness of this technique, the cetylpyridinium chloride concentration in water can be reduced by 90% in one stage with a liquid residence time of 375 minutes. The surfactant concentration in the collapsed foam is 21.5 times the feed concentration. This cationic surfactant was easier to remove from water by foam fractionation than the anionic surfactants studied.     

Investigation on the Properties of Aqueous Foams Stabilized by Cetyltrimethylammonium Bromide in Terms of Free Drainage and Bubble Size

Although foams stabilized by surfactants have been the subject of massive investigations and great achievements were made over the past few years, many questions concerning their properties are still not well understood. The aim of this study is to examine the effect of the cetyltrimethylammonium bromide (CTAB) concentration on the foam properties and illustrate the interaction between liquid drainage and bubble size evolution. Experiments were carried out at varying CTAB concentrations ranging from 0.1 to 5.0 times the critical micelle concentration (CMC), where the variation of the liquid content of foam and bubble size was simultaneously determined using a commercially available FoamScan device. The results showed that the foam properties (both foamability and foam stability) of CTAB were largely dependent on the surfactant concentration when concentrations c < CMC but this effect did not scale linearly with concentration. When c ≥ CMC, both foamablity and foam stability were nearly concentration independent, while the latter showed a small decrease due to the formation of micelles. In addition, the correlation between free drainage and bubble size evolution indicated that the increase of bubble size could indeed enhance the foam drainage.