Article pubs.acs.org/Langmuir
Understanding about How Different Foaming Gases Effect the Interfacial Array Behaviors of Surfactants and the Foam Properties Yange Sun, Xiaoqing Qi, Haoyang Sun, Hui Zhao, and Ying Li* Key Laboratory of Colloid and Interface Chemistry of State Education Ministry, Shandong University, 27 South Road of ShanDa, Jinan, Shandong 250100, P. R. China S Supporting Information *
ABSTRACT: In this paper, the detailed behaviors of all the molecules, especially the interfacial array behaviors of surfactants and diffusion behaviors of gas molecules, in foam systems with different gases (N2, O2, and CO2) being used as foaming agents were investigated by combining molecular dynamics simulation and experimental approaches for the purpose of interpreting how the molecular behaviors effect the properties of the foam and find out the key factors which fundamentally determine the foam stability. Sodium dodecyl sulfate SDS was used as the foam stabilizer. The foam decay and the drainage process were determined by Foamscan. A texture analyzer (TA) was utilized to measure the stiffness and viscoelasticity of the foam films. The experimental results agreed very well with the simulation results by which how the different gas components affect the interfacial behaviors of surfactant molecules and thereby bring influence on foam properties was described.
■
INTRODUCTION Aqueous foam is considered as a colloidal system consisting of dispersed gas phase and a continuous liquid phase, stabilized in most cases by surfactant molecules adsorbed on the gas− liquid,1−3 which has wide applications not only in our daily life, for example, cosmetics and detergents, but also in many industrial regions such as mineral floatation, electromagnetic interference shielding, and enhanced oil recovery (EOR), etc.4−9 In most of the practical occasions, good foam stability is required.10 Numerous studies on the factors affecting the foam stability have been done, among them, the types and concentration of the surfactants and the additives and the temperature were all recognized to be the core ones that could play an important role on changing foam stability through diverse mechanisms.11−21 In the previous references, nitrogen was commonly used as foaming gas. Studies about the impact of the foaming gases on foam properties are very rare, while different kinds of gases have been applied as foaming agents, especially in many new technologies. For instance, foam flooding is one of the most important novel EOR techniques with high potential.22 In recent years, the increasing emission of greenhouse gases (CO2 and flue gas) is widely considered as an urgent social challenge. If carbon dioxide captured from flue gas could be used in EOR flooding, it would open a new view for combining the technical innovation and the social economic interests together.23,24 It is also quite meaningful using flue gas or decarburization flue gas as foaming agent, not only in view of oil production but also for environmental protection. Flue gas and decarburization flue gas are both gas mixtures, the primary gas components of which © XXXX American Chemical Society
were N2, O2, and CO2, so it is necessary to study the impact of different gases on foam properties, both from the theoretical and application aspects. Foam is a kind of thermodynamically unstable system, and it begins to evolve as soon as it is created.3 The liquid drainage, the coalescence of bubbles, and the rupture of the foam films are the main processes influencing the foam stability,25−28 which are actually determined by the characteristics of the foam films, so knowing the detailed information about the molecular behaviors in the foam systems is important for better understanding the apparent foam properties, which was still unclear due to the limit of methods researching the molecules at the molecular level, especially at the interfaces. In this study, the molecular behaviors of all the molecules in foam systems, containing surfactants, water and gas molecules, were investigated by molecular dynamics (MD) simulation. Surfactant sodium dodecyl sulfate (SDS) was used as foam stabilizer. N2, O2, and CO2 were used as the gas phase, respectively. Foamscan was used to measure some of the foam properties, such as liquid drainage, the coalescence, and the rupture of foam bubbles, by which the evolution of the foam column and foam films could be described definitely. Bulk phase rheometer with a cylindrical rotor was used to determine the dynamic stability under disturbing and the viscosity of the foam column,10 and a texture analyzer (TA) was used to measure the compressing and dragging force of the heaped Received: June 18, 2016 Revised: July 15, 2016
A
DOI: 10.1021/acs.langmuir.6b02269 Langmuir XXXX, XXX, XXX−XXX
Article
Langmuir Table 1. Details of the Simulated Systems system SDS with N2 with O2 with CO2
a = b (Å)
Lx (Å)
Ly (Å)
Lz (Å)
nwater
nN2
7.5
25.98
30.00
64 64 64
600
200
nO2
nCO2
180 135
Figure 1. (a) Variation of the foam volume formed from different foaming gases (N2 (black open squares), O2 (red open circles), and CO2 (blue open triangles)) with 0.1 wt % SDS as a function of time. (b) Variation of dynamic apparent viscosity of the foam columns formed from 0.1 wt % SDS under rotator stirring as a function of time. T = 323 K. (TMS-PRO, FTC).29 Initially, an liquid solution of volume Vs = 50 mL was foamed by sparking N2, O2, CO2, or air, respectively, through a porous disk (pore sizes = 40−100 μm) at a constant gas flow rate 100 mL/min.32,33 The diameter of cylindrical cell was 150 mm and the height was 50 mm. The total 50 mL liquid was foamed to reach the top edge of cell. Then the probe disk first went down through the preset distance, afterward it went backward to the departure place. Over the whole process, pressure on the bottom and sides of the disk was recorded with the time or distance varying, and the total process lasted about 10 min. The peak compressing force and the viscoelastic force apparently indicated the compressing and dragging peak pressure in the falling and pulling procedure, which qualitatively corresponded to the stiffness and the viscoelasticity of the foam films.29 Molecular Dynamics Simulation. The details of the molecular model and the simulation method used in this paper were described in refs 34 and 35. A sandwich-like double-layer film model was used for simulating the foam films.36 The charges and potentials of all the atoms in the surfactant molecules were assigned based on the calculation using the Compass force field.37,38 Sixteen surfactant molecules were disposed with space suitable for hexagonal close packing to form a surfactant monolayer in a simulation box imposed to periodic boundary conditions in all three spatial directions at first, and the size of the simulation box refers to the maximum adsorption area data of surfactants used in previous simulation and experimental results.34,35 The surface adsorption area per molecule for SDS, DTAB, CBE, and LAA is presumed to be 48.71 Å2. A 25 Å thick slab of the water phase (the number of water molecules is 600) using the flexible SPC/E model with the same cell parameters as surfactants cell was set.39 Two surfactant monolayers were placed on opposite sides of the water phase with hydrophilic headgroups of surfactants inserted to the water phase. On the basis of the molecular model, two gas monolayers were placed on opposite sides of the hydrophobic chain of surfactants to simulate the experimental conditions and detect the impact of different gases on the films of foam. The final length of the simulation boxes keeps the same to ensure the consistent pressure. Details of the simulating box are listed in Table 1. The total energy of the foam film system was given as the combination of valence terms and nonbond interactions, and the summation of energies is listed in the equation:
foam bubbles, which reflects the stiffness and viscoelasticity of the foam films.29 By combining the experimental and simulation results, how the different foaming gases effect the interfacial array behaviors of surfactants and thereby the foam stability were revealed, which would provide some useful guidance for not only the design of the foam flooding system, but also some other practical applications involving CO2, O2 or air other than N2 being used as foaming gases.
■
EXPERIMENTAL SECTION
Materials. Anion surfactant sodium dodecyl sulfate (SDS, purity >99%) was purchased from Sigma-Aldrich. Freshly distilled water (twice distilled) was used in all solution preparations. N2, O2, CO2, and air (purity >99.999%) were purchased from Deyang Special Gas Co., Ltd. The Measurement of Static Foam Stability. The Foamscan device (TECLIS, France) was utilized to monitor the foam properties (foam stability, gas percolation, and drainage).30,31 In our experiments, an initial liquid volume of Vs = 60 mL was foamed by sparking N2, O2, CO2, or air, respectively, through a porous disk (pore sizes = 40−100 μm) at a constant gas flow rate 100 mL/min. After the total foam volume reached to 200 mL, the changing of the liquid fraction in the foam column was measured by three electrodes, which were named as the first, the second, and the third electrode from the bottom to the top of the foam column, respectively. Pictures of the foams were recorded using the CSA camera. Dynamic Stability of Foam. The dynamic foam stability was determined using rotor-disturbing method.10 The foam column was formed and contained in a transparent glass bucket with interlayer, which is connected with a water bath, and the temperature was kept at 50 ± 0.1 °C. The apparent viscosity of the foam was measured after the foam being formed by Brookfield R/S plus rheometer with a V 340-20 cylinder rotor. The shear rate of the rotor was kept at 10 s−1, and the shearing stress was fixed in the determination. The apparent foam viscosity under disturbing was constantly recorded until the foam column collapsed. The measurement was repeated for several times to make sure the results were reproducible, and one of the determined results was shown. Texture Analyzer (TA). The microhardness and the viscoelastic feature of the foam films were determined with a texture analyzer
E = E bonds + Eangles + Edihedrals + Ecross + E VDW + Eelec B
DOI: 10.1021/acs.langmuir.6b02269 Langmuir XXXX, XXX, XXX−XXX
Article
Langmuir
Figure 2. Images of foams formed from different foaming gases: N2 foam (a−c), O2 foam (d−f), CO2 foam (g−i). Images were taken at 1 min (a, d, g), 3 min (b, e, h), and 6 min (c, f, i) after the foam was generated. After the full explicit atom model was constructed, molecular dynamics simulation was conducted to explore the interfacial behaviors of the surfactants on foam films, in which the NVT ensemble was carried out with a time step of 0.001 ps. The temperature was controlled using a Hoover−Nose thermostat40,41 with a relaxation time of 0.2 ps. The simulations were performed at T = 323 K, being the same as experimental conditions. For the long-range electrostatic potential statistics, the Ewald summation method was used.42 After the dynamics simulation ran 4 ns to get equilibrium period, another 500 ps run was conducted for confirmation and analyzation.
results of 0.3 wt % SDS solution also gave out the same discipline (Supporting Information, Figure S2). So the stability of aqueous foam formed from surfactant solution using O2 as gas agent was lower than that formed using N2, while that using CO2 was much lower than those using N2 and O2. The variation of the apparent viscosity of the foam column as a function of time is shown in Figure 2b. The viscosity of the foam column increased in the generation process and further increased as the drainage proceeding, the following slight decrease of the apparent viscosity of the fresh wet foams was induced by the coalescence of the foam bubble. The eventually abrupt decrease was caused by the collapse of the foam column. The end of the curves indicated the time when the foam column has mostly collapsed, which reflects the dynamic foam stability under disturbance. Obviously, the dynamic foam stability of CO2 foam is also much more lower than N2 and O2 foam and that of O2 foam is a little worse than N2 foam. The Foam Drainage and Coalescence of Bubbles Detected by Foamscan. The images of the foam which was generated using N2, O2 and CO2 as gas agents were captured at different times after being generated\ to give out the information about the variation of the size distribution of foam bubbles and foam film thickness along with the decay process, as shown in Figure 2. At the beginning, the size of N2 and O2 bubbles was almost the same, then the size of O2 bubbles became a little larger than the N2 bubbles, which means the coalescence of bubbles in O2 foam was a little faster than N2 foam. For CO2 foam, the size of bubbles was much bigger than those in N2 and O2 foam at the start and increased very quickly
■
RESULTS AND DISCUSSION The Foam Stability of SDS Foam Using N2, O2, and CO2 as Foaming Gases. The foam ability and foam stability of SDS when N2, O2, and CO2 were used as foaming gases, respectively, were determined using gas flow method by Foamscan at 323 K. The concentration of SDS was 0.1 wt %. The time needed to get equal volume of foam was recorded to represent the foam ability.10 The evolution of the foam column was monitored as a function of time and the half-life time thalf was chosen to reflect the foam stability. As shown in Figure 1a, at the gas flow rate of 100 mL/min, the foaming time was similar (about 48 s) when N2 and O2 were used as foaming gases. However, it was 78 s when CO2 was used as foaming gas. According to the foam decay curves, the thalf of the N2 foam was 72 min, which was almost two times longer than the O2 foam (38 min), while the thalf of CO2 was only 6 min. Under different gas flow rates (40, 60, and 80 mL/ min), the measurement results have the same trend, as shown in Supporting Information, Figure S1. The determination C
DOI: 10.1021/acs.langmuir.6b02269 Langmuir XXXX, XXX, XXX−XXX
Article
Langmuir
Figure 3. Variation of liquid fraction of the foams as a function of time: formed from N2 (black open squares), O2 (red open circles), CO2 (blue open triangles). (a) First electrode. (b) Third electrode.
along with the foam decay process, which illustrated that the coalescence and disruption of the foam bubbles were very serious. The liquid fraction of the foam column was recorded along with the generation and decay process too. The data detected by the first electrode located at the bottom of foam column and the third electrode located at the top of foam column are shown in Figure 3. The first rising section of the curve represents the creation process of the foam, and the later downward part corresponds to the drainage and foam decay process. The peak values of the curves represent the maximum liquid fraction of the fresh wet foam, which could represent the liquid carry capacity of the formed foam. It took longer time for the detector to perceive the generation of the CO2 foam, and it also took longer time to get the peak value of the liquid fraction, which corresponded to the poor foam ability when CO2 was used as foaming gas. It was found that the maximum liquid fraction of CO2 foam was higher than N2 and O2 foam initially, but along with the drainage process, the liquid fraction of the CO2 foam decreased more quickly than N2 and O2 foam. According to the images at 6 min in Figure 2, the thickness of CO2 foam films was actually similar to N2 and O2 foam films, so the easily occurred coalescence and disruption of the foam bubbles in CO2 foam should be the main reason which reduced the total area of foam films and resulted in the rapid reduction of liquid fraction of foam. To understand better about what happened in foam films when CO2 and O2 were used as foaming gases, molecular dynamics simulation method was used to investigate the behaviors of the molecules in foam systems. Behaviors of the Molecules in the Foam System Described by Molecular Dynamics Simulation. The snapshots of the configurations of the three simulated foam systems at the end of the simulation run are shown in Figure 4, with N2, O2, and CO2 were used as gas agents, respectively. It could be found that, in CO2 system the SDS molecules in the foam film clustered obviously and there was an opening channel being formed in the interfacial layer, some CO2 molecules penetrated through the channel getting into the aqueous phase. While for N2 and O2 systems, there were no opening channels in the interface layer and the SDS molecules did not aggregate notably, fewer O2 and fewer N2 molecules penetrated into the aqueous phase comparing with CO2 foam system. The distribution of the tilt angle θ of the hydrophobic tail chain of the surfactant molecules in the foam film was
Figure 4. Equilibrated configuration snapshots at the end of simulations. For clarity, the surfactants and the gases (N2, O2, CO2) are drawn as van der Waals spheres, shown as small colored spheres and water molecules drawn in line style. The atom coloring scheme is: C, gray; H, white; O, red; N, blue; S, yellow; Na, violet.
analyzed, as shown in Figure 5. The distribution of the orientation of the hydrophobic tails of the SDS molecules in N2
Figure 5. Tilt angle orientation distributions with respect to the Z direction of the surfactant hydrophobic tail for (a) N2, (b) O2, and (c) CO2. D
DOI: 10.1021/acs.langmuir.6b02269 Langmuir XXXX, XXX, XXX−XXX
Article
Langmuir
Figure 6. (a) Mean square displacement (MSD) of the head groups (−SO4−) of SDS with the atmosphere of different gases. (b) Mean square displacement (MSD) of different foaming gases. Molecules: N2 (black open squares), O2 (red open circles), and CO2 (blue open triangles).
Figure 7. (a). Radical distribution of water around the sulfate group with different gases coexisting. (b) Radical distribution of different gases around the sulfate group of SDS. (c) Radical distribution of water around the different foaming gases. (d). Detailed interaction between CO2 and water and surfactant headgroups.
Diffusion behaviors of gas molecules at the different gases/ water interface are shown in Figure 6b. The MSD value of O2 molecules is larger than N2 and CO2 within the same time, illustrating that the moving speed of O2 molecules in the foam film was the fastest. The RDF43 of water molecules to the headgroups (−SO4−) of SDS and the gas molecules was calculated, as shown in Figure 7a. The water density around the −SO4− decreased in the atmosphere of CO2 molecules compared with O2 and N2 molecules (Figure 7a), which should result from the strong interaction between CO2 molecules and the headgroups (−SO4−) of SDS as shown in Figure 7b. The distribution of
and O2 systems was much wider than that of CO2 system. The most probable tilt angle of SDS tails was only 22° in the CO2 system, which indicated that the SDS tails tended to be very vertical to the surface, which was unfavorable to the foam stability.43 Mean square displacement (MSD)43 of the head groups of SDS was calculated as shown in Figure 6a. The velocity of the diffusion movement of the SDS head groups was obviously the fastest in CO2 system, followed by that in O2 system, and was slowest in N2 system, which illustrated that the “anchoring” effect of the hydrophilic groups of SDS got weakened in the CO2 system, which was also unfavorable to the foam stability. E
DOI: 10.1021/acs.langmuir.6b02269 Langmuir XXXX, XXX, XXX−XXX
Article
Langmuir
Verification of the Effect of Foaming Gases on the Foam Stability by Other Surfactants. The molecular dynamics simulation of the foam systems using cationic surfactant dodecyltrimethylammonium bromide (DTAB), nonionic laurel alkanolamide (LAA), and amphoteric surfactant lauramidopropyl betaine (CBE) as foam stabilizer, respectively, with N2, O2, and CO2 being used as gas agents separately proceeded. The snapshots of the configurations of the simulated systems at the end of the simulation run were shown in Figure 8a, and Supporting Information, Figures S3−S5. The opening channel in the interfacial surfactant layer was found in all the three systems when CO2 was used as gas agent, so the serious coalescence of the gas bubble would be inescapable. And the molecules of the above three kinds of surfactants arranged more disorderly than SDS in the foam film, the “covering” effect of surfactant molecules would be worse than SDS, too. Actually, according to our previous experimental results reported in ref 44, the stability of the foams generated by LAA, DTAB, and CBE solutions using CO2 is certainly very poor and is worse than SDS foam. MSD of the gas molecules were calculated and are shown in Figure 8b and Supporting Information, Figures S6 and S7. The self-diffusion speed of O2 molecules in all the three foam films were also the fastest comparing with N2 and CO2, which proved that the quick motion of O2 molecules in the foam system is surely the reason for the slight decrease of the stability of O2 foam comparing with N2 foam. The Stability of SDS Foam Using Air As Foaming Gas. According to the above results, the stability of aqueous foam formed using CO2 was much lower than N2 foam, while stability of the O2 foam is not too bad, which provided powerful support on using air as foaming agent. The foam decay curve of SDS foam formed using air as the gas agent was measured using Foamscan, as shown in Figure 9a,b. When concentration of surfactant is 0.1 wt %, the decay curve of air foam is very similar to the N2 foam initially, but the bursting rate of the air foam was accelerated after the drainage proceeded for about 30 min so that the thalf of the air foam was close to that of O2 foam. When concentration of surfactant is 0.3 wt % and the air foam is as stable as N2 foam, barely no difference was found on the foam characteristics in the decay process of the two foams. The MD simulation of the foam systems using simulated air (N2:O2 = 4:1 molar ratio) as the gas agent was done, the MSD of the gas components was calculated and is shown in Figure 9c, and the equilibrium snapshot of the simulated system is shown in Figure 9d. It could be found that the array behaviors of the surfactant molecules in foam system using air as a gas agent (Figure 9d) was similar to that in N2 system, while the diffusion rate of O2 molecules is still a little faster than N2 molecules in the system (Figure 9c). So the quickly diffusion of O2 molecules across the foam film could induce a certain degree of negative effect on the foam stability when air was used as gas agent, but the challenge is not hard and could be overcome by increasing the surfactant concentration a little.
the water molecules around the gas molecules was calculated using MD, which is shown in Figure 7c. According to Figure 7c, there was definitely interaction between CO2 molecules and water molecules and the detailed behaviors of the headgroups of SDS and CO2 molecules is shown in Figure 7d; it could be clearly found that there existed hydrogen bonds between CO2 and headgroups of surfactant and water molecules by which it was not difficult to understand why CO2 molecules distributed around the SDS, not only among the tail chains but also beside the headgroups, which on one hand decreased the hydrophilicity of surfactant molecules, resulted in the aggregation of SDS molecules, and on the other hand coursed the emerge of the opening channels in the end. TA could be used to evaluate the strength of the foam films as reported in ref 29. The compress and viscoelastic force of the foam were measured, and the peak values of the measured compress and viscoelastic force are listed in Table 2, which Table 2. TA Results of Foam Films Formed by Different Foaming Gases foaming gases
N2
O2
CO2
compress force (N) viscoelastic force (N)
0.104 0.097
0.104 0.097
0.052 0.052
corresponded to the stiffness and viscoelasticity of the foam films, respectively. The peak compressing force and peak viscoelastic force of O2 foam tend be similar to N2 foam, which is very reasonable because O2 molecular has little effect on the behaviors of surfactants in the foam film according to the previous simulation results, while for CO2 foam, the stiffness and viscoelasticity of foam film were both low, which indicated that the strength of SDS foam film was surely decreased. Combining the simulation results and the experimental results, the mechanism of how the different gases affect the characteristic of the foam films and foam stability could be concluded. The high motion speed of O2 molecules in the system might result in the acceleration of the Ostwald ripening and thereby the decreased stability of O2 foam. While for CO2 foam, because of the affinity interaction between CO 2 molecules with both the hydrophobic tail and the hydrophilic group, not only the interfacial behaviors of SDS were changed, the “covering” effect of the surfactant molecules became worse but also lead to the emergence of the opening channel in the interface layer. The strength of the foam films was decreased, and the permeation of the CO2 molecules across the foam films was accelerated, so the coalescence and disruption of the foam bubble was highly strengthened. The interfacial formation energy (IFE) of the three systems was calculated, and the results are summarized in Table 3. The Table 3. IFE of the Systems with N2, O2, and CO2 as Foaming Gases gas
N2
O2
CO2
IFE/kcal·mol−1
−67.469
−63.619
−60.809
■
CONCLUSION The relationship of the molecular behaviors and monolayer configuration of surfactant molecules in foam film to the apparent foam properties has been elucidated by combining the detailed molecular simulation method and diverse experimental approaches. The molecular behaviors of surfactants, gas molecules, and water molecules in the foam systems using
N2 system has the lowest IFE and the CO2 system has the highest IFE, so the interfacial activity of SDS is the highest at N2/water interface, while the lowest is at CO2/water interface, which corresponded well with the foam ability of SDS mentioned above. F
DOI: 10.1021/acs.langmuir.6b02269 Langmuir XXXX, XXX, XXX−XXX
Article
Langmuir
Figure 8. (a). Equilibrated configuration snapshots with CO2 molecules coexistence for DTAB/CBE/LAA systems at the end of simulations. Upper part of the picture: detailed interaction between CO2 and water and surfactant headgroups. (b) MSD of different foaming gas molecules for LAA system.
Figure 9. (a) Variation of the foam volume formed from different foaming gas (N2 (black open squares), O2 (red open circles), air (blue open triangles)) with 0.1 wt % SDS as a function of time. (b) Variation of the foam volume formed from different foaming gas (N2 (black open squares), O2 (red open circles), air (blue open triangles)) with 0.3 wt % SDS as a function of time. (c) MSD of different gas molecules: N2 (black open squares), O2 (red open circles) with air as foaming agent. (d) Equilibrated configuration snapshots with N2/O2 (4:1 molar ratio) molecules coexistence at the end of simulations.
through the foam films. The experimental results showed that the CO2 bubbles do coalescence very quickly comparedg with N2 and O2. For the O2 system, the array behaviors of SDS were not affected obviously compared with the N2 system, but the quick motion speed of O2 molecules in the foam system led to the slight decrease of the stability of O2 foam. The above mechanism was verified in other foam systems stabilized by cationic surfactant DTAB, nonionic surfactant LAA, and amphoteric surfactants CAB, respectively. The above results helped us to understand better about how the various foaming
N2, O2, and CO2 as gas agents, respectively, were analyzed, which provided thorough microscopic information about the molecular behaviors to explain the difference of the foam properties caused by various foaming gases. The simulation results showed that the CO2 molecules were not only compatible with hydrophobic tails of surfactants but also have interaction with the hydrophilic headgroup of SDS, so they could permeate through the surfactant layer easily, thereby inducing the emergence of opening channels in the interfacial layer which enhanced the chance for CO2 molecules diffusing G
DOI: 10.1021/acs.langmuir.6b02269 Langmuir XXXX, XXX, XXX−XXX
Article
Langmuir
(13) Ramanathan, M.; Müller, H. J.; Möhwald, H.; Krastev, R. Foam Films as Thin Liquid Gas Separation Membranes. ACS Appl. Mater. Interfaces 2011, 3, 633−637. (14) Deng, Q.; Li, H.; Li, C.; Lv, W.; Li, Y. Enhancement of foamability and foam stability induced by interactions between a hyperbranched exopolysaccharide and a zwitterionic surfactant dodecyl sulfobetaine. RSC Adv. 2015, 5, 61868−61875. (15) Á guila-Hernández, J.; Trejo, A.; García-Flores, B. E. Surface tension and foam behaviour of aqueous solutions of blends of three alkanolamines, as a function of temperature. Colloids Surf., A 2007, 308, 33−46. (16) Schelero, N.; Hedicke, G.; Linse, P.; Klitzing, R. v. Effects of counterions and co-ions on foam films stabilized by anionic dodecyl sulfate. J. Phys. Chem. B 2010, 114, 15523−15529. (17) Alargova, R. G.; Warhadpande, D. S.; Paunov, V. N.; Velev, O. D. Foam superstabilization by polymer microrods. Langmuir 2004, 20, 10371−10374. (18) Sun, Q.; Li, Z.; Li, S.; Jiang, L.; Wang, J.; Wang, P. Utilization of surfactant-stabilized foam for enhanced oil recovery by adding nanoparticles. Energy Fuels 2014, 28, 2384−2394. (19) Li, X.; Karakashev, S. I.; Evans, G. M.; Stevenson, P. Effect of environmental humidity on static foam stability. Langmuir 2012, 28, 4060−4068. (20) Wang, L.; Yoon, R.-H. Effect of pH and NaCl concentration on the stability of surfactant-free foam films. Langmuir 2009, 25, 294− 297. (21) Petkova, R.; Tcholakova, S.; Denkov, N. Foaming and foam stability for mixed polymer−surfactant solutions: effects of surfactant type and polymer charge. Langmuir 2012, 28, 4996−5009. (22) Farajzadeh, R.; Andrianov, A.; Krastev, R.; Hirasaki, G.; Rossen, W. R. Foam−oil interaction in porous media: Implications for foam assisted enhanced oil recovery. Adv. Colloid Interface Sci. 2012, 183184, 1−13. (23) Aaron, D.; Tsouris, C. Separation of CO2 from flue gas: a review. Sep. Sci. Technol. 2005, 40, 321−348. (24) Gupta, H.; Fan, L.-S. Carbonation-calcination cycle using high reactivity calcium oxide for carbon dioxide separation from flue gas. Ind. Eng. Chem. Res. 2002, 41, 4035−4042. (25) Jun, S.; Pelot, D.; Yarin, A. Foam consolidation and drainage. Langmuir 2012, 28, 5323−5330. (26) Hansen, L. D.; McCarlie, V. W. From foam rubber to volcanoes: The physical chemistry of foam formation. J. Chem. Educ. 2004, 81, 1581. (27) Attia, J. A.; Kholi, S.; Pilon, L. Scaling laws in steady-state aqueous foams including Ostwald ripening. Colloids Surf., A 2013, 436, 1000−1006. (28) Samanta, S.; Ghosh, P. Coalescence of bubbles and stability of foams in aqueous solutions of Tween surfactants. Chem. Eng. Res. Des. 2011, 89, 2344−2355. (29) Hu, X.; Li, Y.; He, X.; Li, C.; Li, Z.; Cao, X.; Xin, X.; Somasundaran, P. Structure−Behavior−Property Relationship Study of Surfactants as Foam Stabilizers Explored by Experimental and Molecular Simulation Approaches. J. Phys. Chem. B 2012, 116, 160− 167. (30) Carey, E.; Stubenrauch, C. Properties of aqueous foams stabilized by dodecyltrimethylammonium bromide. J. Colloid Interface Sci. 2009, 333, 619−627. (31) Carey, E.; Stubenrauch, C. A disjoining pressure study of foam films stabilized by mixtures of a nonionic (C 12 DMPO) and an ionic surfactant (C 12 TAB). J. Colloid Interface Sci. 2010, 343, 314−323. (32) Bhattacharyya, A.; Monroy, F.; Langevin, D.; Argillier, J.-F. Surface rheology and foam stability of mixed surfactant-polyelectrolyte solutions. Langmuir 2000, 16, 8727−8732. (33) Koehler, S. A.; Hilgenfeldt, S.; Stone, H. A. A generalized view of foam drainage: experiment and theory. Langmuir 2000, 16, 6327− 6341. (34) Jang, S. S.; Goddard, W. A. Structures and properties of newton black films characterized using molecular dynamics simulations. J. Phys. Chem. B 2006, 110, 7992−8001.
gases affect the foam properties and provide new insights into the contribution of impact factors for foam properties.
■
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.langmuir.6b02269. Variation of the foam volume formed from different gas agents, equilibrated configuration snapshots at the end of simulations for 6501 and DTAB systems, MSD of different foaming gases molecules for DTAB and CBE systems (PDF)
■
AUTHOR INFORMATION
Corresponding Author
*Phone: +86-531-88362078. Fax: +86-531-88364464. Email:
[email protected]. Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS The funding from National Science Fund of China (no. 21473103, 61575109) and National Municipal Science and Technology Project (no. 2008ZX05011-002) is gratefully acknowledged.
■
REFERENCES
(1) Salonen, A.; In, M.; Emile, J.; Saint-Jalmes, A. Solutions of surfactant oligomers: a model system for tuning foam stability by the surfactant structure. Soft Matter 2010, 6, 2271−2281. (2) Sonoda, J.; Sakai, T.; Inomata, Y. Liquid Oil That Flows in Spaces of Aqueous Foam without Defoaming. J. Phys. Chem. B 2014, 118, 9438−9444. (3) Herzhaft, B. Correlation between transient shear experiments and structure evolution of aqueous foams. J. Colloid Interface Sci. 2002, 247, 412−423. (4) Yang, W.; Yang, X. Molecular dynamics study of the influence of calcium ions on foam stability. J. Phys. Chem. B 2010, 114, 10066− 10074. (5) Du, D.-X.; Beni, A. N.; Farajzadeh, R.; Zitha, P. L. Effect of water solubility on carbon dioxide foam flow in porous media: an X-ray computed tomography study. Ind. Eng. Chem. Res. 2008, 47, 6298− 6306. (6) Paulson, O.; Pugh, R. Flotation of inherently hydrophobic particles in aqueous solutions of inorganic electrolytes. Langmuir 1996, 12, 4808−4813. (7) Binks, B. P. Particles as surfactantssimilarities and differences. Curr. Opin. Colloid Interface Sci. 2002, 7, 21−41. (8) Farajzadeh, R.; Andrianov, A.; Zitha, P. L. J. Investigation of immiscible and miscible foam for enhancing oil recovery. Ind. Eng. Chem. Res. 2010, 49, 1910−1919. (9) Yang, Y.; Gupta, M. C.; Dudley, K. L.; Lawrence, R. W. Novel carbon nanotube-polystyrene foam composites for electromagnetic interference shielding. Nano Lett. 2005, 5, 2131−2134. (10) Lv, W.; Li, Y.; Li, Y.; Zhang, S.; Deng, Q.; Yang, Y.; Cao, X.; Wang, Q. Ultra-stable aqueous foam stabilized by water-soluble alkyl acrylate crosspolymer. Colloids Surf., A 2014, 457, 189−195. (11) Sett, S.; Sahu, R.; Pelot, D.; Yarin, A. Enhanced foamability of sodium dodecyl sulfate surfactant mixed with superspreader trisiloxane-(poly) ethoxylate. Langmuir 2014, 30, 14765−14775. (12) Alargova, R. G.; Warhadpande, D. S.; Paunov, V. N.; Velev, O. D. Foam superstabilization by polymer microrods. Langmuir 2004, 20, 10371−10374. H
DOI: 10.1021/acs.langmuir.6b02269 Langmuir XXXX, XXX, XXX−XXX
Article
Langmuir (35) Bandyopadhyay, S.; Chanda, J. Monolayer of monododecyl diethylene glycol surfactants adsorbed at the air/water interface: a molecular dynamics study. Langmuir 2003, 19, 10443−10448. (36) Sun, H.; Ren, P.; Fried, J. The COMPASS force field: parameterization and validation for phosphazenes. Comput. Theor. Polym. Sci. 1998, 8, 229−246. (37) Sun, H. COMPASS: an ab initio force-field optimized for condensed-phase applications overview with details on alkane and benzene compounds. J. Phys. Chem. B 1998, 102, 7338−7364. (38) Berendsen, H.; Grigera, J.; Straatsma, T. The missing term in effective pair potentials. J. Phys. Chem. 1987, 91, 6269−6271. (39) Landau, A. A new method of molecular dynamic computer simulation at constant temperature and pressure. J. Chem. Phys. 2002, 117, 8607−8612. (40) Nosé, S. A unified formulation of the constant temperature molecular dynamics methods. J. Chem. Phys. 1984, 81, 511−519. (41) Liew, C. C.; Inomata, H.; Saito, S. Molecular dynamics study on solvent clustering in supercritical fluid solutions based on particle radial kinetic energy. Fluid Phase Equilib. 1995, 104, 317−329. (42) Taulbee, A. R.; Heuser, J. A.; Spendel, W. U.; Pacey, G. E. Qualitative analysis of collective mode frequency shifts in L-alanine using terahertz spectroscopy. Anal. Chem. 2009, 81, 2664−2667. (43) Li, C.; Li, Y.; Yuan, R.; Lv, W. Study of the microcharacter of ultrastable aqueous foam stabilized by a kind of flexible connecting bipolar-headed surfactant with existence of magnesium ion. Langmuir 2013, 29, 5418−5427. (44) Li, X.; Sun, Y.; Li, Y. Study of the stability of the CO2 aqueous foam. J. Shandong Univ. 2015, 50, 32−39.
I
DOI: 10.1021/acs.langmuir.6b02269 Langmuir XXXX, XXX, XXX−XXX
