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Ultra-stable aqueous foam stabilized by water-soluble alkyl acrylate crosspolymer
Accepted Manuscript Title: Ultra-stable aqueous foam stabilized by water-soluble alkyl acrylate crosspolymer Author: Weiqin Lv Ying Li Yaping Li Sen Zhang Quanhua Deng Yong Yang Xulong Cao Qiwei Wang PII: DOI: Reference:
S0927-7757(14)00530-5 http://dx.doi.org/doi:10.1016/j.colsurfa.2014.05.070 COLSUA 19271
To appear in:
Colloids and Surfaces A: Physicochem. Eng. Aspects
Received date: Revised date: Accepted date:
4-3-2014 22-5-2014 27-5-2014
Please cite this article as: W. Lv, Y. Li, Y. Li, S. Zhang, Q. Deng, Y. Yang, X. Cao, Q. Wang, Ultra-stable aqueous foam stabilized by water-soluble alkyl acrylate crosspolymer, Colloids and Surfaces A: Physicochemical and Engineering Aspects (2014), http://dx.doi.org/10.1016/j.colsurfa.2014.05.070 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Ultra-stable aqueous foam stabilized by water-soluble alkyl acrylate
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crosspolymer
Key Laboratory of Colloid and Interface Chemistry of State Education Ministry, Shandong University, 27
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South Shanda road, Jinan, Shandong, 250100, P. R. China
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Weiqin Lva, Ying Lia*, Yaping Lia, Sen Zhanga, Quanhua Denga, Yong Yangb, Xulong Caob, and Qiwei Wangb
Geological Scientific Research Institute, Shengli Oilfield, 3 Liaocheng road, Dongying, Shandong, 257100, P.
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R. China
∗
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te
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[email protected]
Prof. Dr. Ying Li
School of Chemistry and Chemical Engineering
Shandong University
27 Shanda Nanlu, Jinan, Shandong, P. R. China 250100 Tele: +86-531-88362078 Fax: +86-531-88364464 Email: [email protected]
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Abstract
Aqueous foam solely stabilized by a kind of hydrophobic modified water-soluble polymer, alkyl acrylate
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crosspolymer (HMPAA), was found to be extraordinary stable, no matter in static state or under disturbance,
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even if CO2 was used as gas agent. The high water-holding capacity of HMPAA foam film demonstrated by
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FoamScan and FT-IR measurement was in accordance with the low gas transmission through the foam film, which was detected by FT-IR, too. Fluorescence Microscope, TEM and Molecular Dynamic (MD) simulation
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were used to get information about the adsorption and array behavior of HMPAA on the gas/water interface
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and in foam film, it was found that the comb polymer molecules adsorbed on the interface clustered to form plat network, which covered the interface very well like a “shell”. By combining all these results, the
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foam aqueous foam was proposed.
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mechanism of ultra high foam stability of HMPAA was revealed, and a novel approach to achieve long-term
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Keywords: Ultra-stable foam; Water-soluble polymer; Fluorescence microscopy; FT-IR; CO2 foam
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1. Introduction
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Aqueous foam is a system that gas dispersed in liquid which has been widely used in daily life and
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industrial applications, such as extinguishing fires, mineral floatation, enhanced oil recovery, food industry,
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personal care products, etc. [1-3]. In many applications, the foam is required to have long-term stability. This is an ongoing technical challenge because foam is a multiphase dispersed system with highly developed
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interface. This makes the foam system is thermodynamically and kinetically unstable. After the foam is generated, the thinning of foam film caused by liquid drainage, coalescence of the foam bubbles would be
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aggravated by continuous diffusion of gas through the foam film, the rupture of foam films occur constantly, and both would be strengthened under disturbance
[4-11]
. How to dramatically increase the stability of the
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aqueous foam is always a huge challenge for not only theoretical research but also application technology.
In typical industrial applications of aqueous foam, for example, foam flooding in EOR
[12]
, Nitrogen, air
and CO2 are usually used as the gas agents. In recent years, the underground injection of greenhouse gas for storage or displacement attracted much more attention
[13]
, and CO2 foam flooding in oil recovery which uses
captured CO2 from flue gas is one of the most impressive techniques [14-17]. However, aqueous foam using CO2 as foaming gas is much more difficult to be stabilized as compared with that of N2 and air. Therefore, developing technologies that can be used to improve the stability of CO2 foam is of technical and application value.
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Surfactant is one of the most typical type of the aqueous foam stabilizers
[5, 11, 18]
. However, the stability
of foam formed from surfactant solution is not always satisfied, especially under harsh conditions, such as high
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temperature, high salt concentration, or CO2 being used as gas agent. Recently, ultra-stable aqueous foam stabilized by polymer rods or solid particle with or without surfactant has been reported [23]
. For example,
produced extraordinary stable foams using hydrophobic polymer microrods,
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Alargova and coworkers
[19-28]
[27]
reported foams and emulsions with extraordinary stability by using
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bubbles to keep bubbles stable. Wege
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which interacted with each other like dense thick “hairy” forming rigid intertwined protective shells around the
hydrophobic cellulose microparticles formed in situ with a liquid-liquid dispersion technique. However, the
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use of unsoluble polymer rods or particles could be limited in the production applications.
[29-31]
was used as aqueous foam stabilizer. It was
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In this paper, alkyl acrylate crosspolymer HMPAA
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found out that the foam formed from HMPAA solution has extremely high static and dynamic stability, not
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only for foams using N2 and air as gas agent, but also for that using CO2. The drainage of foam and the change of foam film following drainage process were measured by FoamScan and FT-IR. The transmission of gas through foam film was also determined by FT-IR. The behavior of polymer molecules in bulk phase and foam film was investigated by fluorescence microscopy, TEM and molecular simulation. Through all the results, the mechanism of ultra stability of foam was revealed, which represented a novel approach to achieve long-term foam stability.
2. Materials and Methods 2.1. Materials
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The alkyl acrylate crosspolymer HMPAA used in the paper was introduced in detail in our previous study [30]
, of which the ingredient ratio of hydrophobic modified segments is 10%, the average molecular weight is
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about 100, 000. The aqueous solutions of HMPAA were prepared by following procedure: a certain amount of polymer was added in water, the solution was kept stirred using magnetic stirrer at 30 •±0.1• for 24 h before
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used in further measurement.
Anionic surfactant Sodium dodecyl sulfate (SDS, purity >99%), was bought from Sigma Aldrich. The
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fluorescent indicator Rhodamine B (purity >99%) was purchased from Aladdin. Freshly distilled water (twice
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distilled) was used in all solution preparations.
2.2. Methods
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2.2.1. The Measurement of Static Foam Stability
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The FoamScan device (TECLIS, France) was utilized to monitor foam properties (foamability, foam stability and drainage)
[32, 33]
. The bubble sizes can be analyzed with the cell size analysis (CSA) function
(TECLIS, France) which allows for a visualization of the bubbles coalescing process. In our experiments, an initial liquid volume of Vs = 60 ml was foamed by sparking N2 through a porous disk (pore sizes = 40-100 μm) at a constant gas flow rate 100 ml/min. The total foam volume reached to 150 ml, the changing of the volume of solution and the liquid fraction in the foam column were measured by three electrodes. The electrodes were named as the first, the second and the third electrode from the bottom, middle and top of the foam column respectively. Pictures of the foams were recorded using the cell size analysis (CSA) camera. The CSA
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software from TECLIS was used to analyze the bubble size. The mean diameter and mean area of the bubbles
2.2.2. Dynamic Stability of Foam
[5]
. The foam column was
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The dynamic foam stability was determined using rotor-disturbing method
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the size distribution and other parameters could be obtained from the analysis.
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formed and contained in a transparent glass bucket with interlayer, which is connected with water bath, the temperature was kept at 30±0.1•. The apparent viscosity of the foam was measured right after being formed,
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with a Digital Viscometer NDJ-8S with #2 cylinder rotor. The rotation speed of the rotor was kept at 6 rpm
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and the shearing stress was fixed in the determination. The apparent foam viscosity under disturbing was
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observed.
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constantly recorded until the foam column collapsed. The data were recorded when reproducible values were
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2.2.3. Fluorescence Microscope Observation
Rhodamine B (0.0002 wt%) was used as the fluorescence label of the polymer chain. For bulk phase observing, the HMPAA solution was dropped in a silica square cell. For foam film observing, appropriate volume of HMPAA solution was deposited on a wire mesh with the grid radius of 0.1mm to form thin film. One drop of Rhodamine B solution (0.0002 wt%) was dropped on the mesh. Then the fluorescence microscope image was taken with Olympus BX53 Microscope (Olympus, Japan). Green filter was utilized for imaging.
2.2.4. Transmission Electron Microscope (TEM)
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Appropriate volume of HMPAA solution was deposited on a 5mm×5mm copper grid to form thin foam film. One drop of phosphotungstic acid solution was dropped, and quickly dried under IR light. The JEM-
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100CX • (100kV) was used.
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2.2.5. Molecular Dynamics Simulation
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A reasonable double-layer film model was prepared for the simulation of the wet foam films. A 65×20×105 grid containing 10 polymer molecules which contain 25 repeating units, 6000 water molecules
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were used. The details were introduced in our early study [5, 11].
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The layer was first minimized by smart minimize algorithm with 50000 steps to avoid the possible
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molecule overlap and make the configurations more reasonable. After a 2 ns MD equilibration period, at least a
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1 ns MD production was run to obtain the dynamic information, the result of which was used for analysis.
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2.2.6. Detection of Foam Film Characteristics by Fourier Transforms Infrared Spectroscopy (FT-IR)
Nicolet IS5 (Thermo Fisher Scientific) was used to measure the FT-IR spectroscopy in the frequency range of 4000−400 cm−1, at a resolution of 1 cm−1 with a total of 16 scans. A quartz tube (90mm long, 8mm diameter) was placed in the test chamber. A vertical foam film was formed inside the tube by blowing HMPAA solution through a capillary and was scanned constantly as a function of time.
(Figure 1)
A setup as shown in figure 1 was used in measurement of the gas permeability of the foam film. A sealed gas cell with pistons full of nitrogen was put into the test chamber and scanned as background. A quartz tube
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(Ф8mm, 90mm long), inside of which a vertical foam film was formed in advance, was connected with the glass column through silicone tube on one side, and connected with a glass container which was full of CO2 on
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the other side. Turned on the piston 2 on the class cell first, and then open the piston 3, the spectroscope was
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scanned constantly as a function of time. 3. Results and Discussion
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3.1. The Static Foam Stability
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The foamability and foam stability of HMPAA was determined using gas flow method by FoamScan. The time needed to get equal volume of foam was recorded to represent the foamability. There is no significant
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difference between the time needed to get 150ml foam from 60 ml 0.1 wt% HMPAA and 0.3 wt% SDS, as
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shown in Table 1. The foam evolution was monitored as a function of time to reflect the foam stability, the half
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life time thalf was also listed in table 1. According to the results, the thalf of the N2 foam stabilized by HMPAA
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could be about 90 h, which is ten times longer than that stabilized by SDS. For CO2 foam, the thalf of the foam formed from HAPAA solution was about 8 times as that of SDS. And the life time of foam lamellar film formed from 0.1 wt% HMPAA solutions in air were much longer than that from 0.3 wt% SDS which was 110 and 50 min respectively [11]. It was obvious that the aqueous foam stabilized by HMPAA is much more stable than that stabilized by SDS.
(Table 1) (Figure 2) The critical associative concentration (CAC) of HMPAA in aqueous solution is determined to be about 0.08 wt%, which was shown in figure 2. It can be seen that even the CO2 foam formed from much diluted
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HMPAA solution demonstrated very good stability, the thalf could be hours. The bulk phase viscosity of HMPAA solutions showed a linear increase with the increase of concentration above CAC. The half life time
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of the CO2 foam increased with the increase of HMPAA concentration above CAC, too. But the thalf curve became flatten when the HMPAA concentration is higher than 0.12 wt.%, which did not coincide with the
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constant increase tendency of the bulk phase viscosity as a function of concentration, especially when the
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viscosity is higher than 0.2 Pa·s. The high stability of the foam formed from HMPAA solution is not solely
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linked to the increase of the bulk phase viscosity. 3.2. The Dynamic Foam Stability.
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(Figure 3)
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The measurement of apparent viscosity of the foam column as a function of time is shown in Figure 3.
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The end of the curve indicated the collapse of the foam column, which reflects the dynamic foam stability
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under disturbing. In SDS foam, the apparent viscosity slightly increased at the initial period, which was induced by the adhension effect aroused from the thinning of foam film following gravitational drainage, and then decreased because of the collapse of the foam. The apparent viscosity of the foam formed from HMPAA solution was much higher than that from SDS solution. There was a increase of the foam viscosity coursed by drainage initially, too. But the apparent viscosity of HMPAA foam still maintain high even under shear for hours, the life time of HMPAA foam is almost 20 times longer that of SDS foam under the same disturbing condition, which showed solidly that the HMPAA foam is outstandingly dynamically stable.
3.3. Determination about the Foam Drainage and Coalescence of Bubbles.
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The time evolution of the liquid fraction of the foam column was monitored directly after the foam was generated to give out information about drainage. The measurement data of the third electrode was shown in
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figure 4. The peak value of the curve represents the initial liquid fraction of the fresh foam, which are 13.5% and 7.5% for HMPAA and SDS foam respectively. This indicates that the HMPAA foam has greater water-
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carrying capability. During the drainage process the liquid fraction decreased until it reaches a constant level,
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The finial liquid fraction reflect the water-holding capacity, which is 5% for HMPAA foam and almost 0 for
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SDS foam. Therefore there is very little amount of water remained in the SDS foam film after complete drainage. It is very clear that both the water-carrying capability and the water-holding capacity of the HMPAA
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foam is high. These phenomena provide important clue for why the HMPAA foam has high static and dynamic
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stability.
(Figure 4)
(Figure 5)
In the above experiment, the difference of foams bubble sizes for the two foam systems attracted our attention. According to images in figure 5, the initial bubbles size of the HMPAA foam is bigger than that of SDS. After 20 min, the bubble size of SDS foam increases about 10 times than initial, while the bubbles size of HMPAA foam just changed slightly. This suggests that the coalescence of bubbles in HMPAA foam is efficiently retarded. It is necessary to point out that the bubble size of the foam formed from HMPAA solution
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at very low concentration also increases distinctly, which shows that the coalescence of bubbles correlated with the adsorption amount of polymer molecules at gas/water interface.
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3.4. The adsorption and array behavior of HMPAA on Gas/water interface and in Foam Film.
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Figure 6 (a) is the fluorescence microscopy image of bulk phase, it was found that the polymer molecules
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was distributed uniformly in the bulk phase solution. Figure 6 (b) is the fluorescence microscopy image of the same solution except for bubbles being put into the solution. It was clear that HMPAA molecules had the
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tendency to be adsorbed at the air/water interface. The thickness of the air/water interfacial layer was smaller
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than the size of the polymer aggregations in bulk phase. This can be due to that polymer opens its structure when it is adsorbed at the interface driven by the hydrophobic side chains. The bubbles in HMPAA solution
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were covered very well by HMPAA molecules at the air-water interface which led to the decrease of the light transmittance in the foam, as shown in Figure 6 (c). However, in SDS system there is no light transmittance
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reduction across the bubbles.
(Figure 6)
Figure 7 showed the microscope, fluorescence microscope and TEM images of foam films formed from 0.05 wt% HMPAA solution and 0.1 wt% HMPAA solution. According to Figure 6, the polymer chains curled up and present as an aggregation state at low concentration (CAC), the polymer chains got stretching and connect with each other forming a network structure. The interfacial coverage degree became high. The air-water interfacial dilational modulus of 0.1 wt% HMPAA solutions was
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determined to be 28.64 mN/m, which is surely higher than normal surfactants. The results agreed very well with that in figure 2 and 5.i.e. full coverage of interface in foam film by the polymer molecules was important
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to maintain high foam stability.
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(Figure 7)
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In order to get detailed information about the HMPAA molecular behaviour at the gas/water interface, molecular dynamics (MD) was used to simulate the foam film, and one of the snapshots was shown in Figure
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8. It was shown that, in the foam film, the hydrophobic side of HMPAA stretched out into the gas phase, the
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main chain docked beneath the gas/water interface and draw close to each other clustering, thus explained how the protective “shell” structure around the bubbles in figure 6 (b, c) could be formed. This simulation result
(Figure 8)
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agrees very well with the experimental observation, and more systematic works are under going.
3.5. Characteristics of the Foam Film Detected by FT-IR.
The FT-IR spectroscopes of foam film formed from SDS and HMPAA solution were shown in figure 9. The absorption band around 1640 cm-1 and the region from 3200 to 3600 cm-1 all correspond to vibration modes of OH. The peak around 2350 cm-1 corresponds to the characteristic absorption of C-O. As shown in figure 9 a and b, all the absorption peak belong to water molecules got weakened quickly for SDS foam film, which means that the amount of water in the foam film decreases quickly along the drainage process. While all the absorption peaks belonging to water molecules do not change so much for the HMPAA foam film, and the
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light transmittance was very low. These indicated that the water content of HMPAA foam film was very high. This is consistent with previous observation that water-holding capacity was notably good. Therefore plenty of
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water molecules was entrapped in the foam film and could not be drained out.
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(Figure 9)
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(Figure 10)
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The gas permeability of foam film was detected by FT-IR, the results was shown in figure 10 a) and b). The CO2 transmitted across the foam film decreased because of the light adsorption of CO2 molecules. It can
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be seen that the gas permeability of HMPAA foam film was much lower than that of SDS. This agrees very
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well with that shown in figure 7 and 8 and further confirms that the gas/water interface was well covered by
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interacted polymer chains. In this case the thickness of interfacial layer is too high to allow the gas
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transmission efficiently. The interfacial layer of surfactant does not have such effect, so the gas could easily transmit through the foam film, and the coalescence of foam bubbles was easily to happen. The FT-IR results correspond perfectly with the experimental results mentioned above. 4. Conclusion
Ultra-stable aqueous foam was obtained using comb water-soluble polymer HMPAA as foam stabilizer. The influences of the polymer behavior and foam film properties on the foam stability have been discussed. It was found that the HAPAA molecules can be adsorbed onto air-water interface and interact with each other to form network structure through the hydrophobic and hydrogen bond interaction. The gas-water interface is therefore covered with the structured network. As a result, the thickness of the foam film of HMPAA was
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observed to be high and huge amount of water molecules were also trapped and hard to be drained out. Therefore the gas permeability of HMPAA foam film became low which makes and the coalescence of
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bubbles in the foam was postponed. According to above, the aqueous foam stabilized by HMPAA becomes extremely stable, even under disturbing or using carbon dioxide as gas agent. We believe that our mechanisms
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on how HMPAA helps to stabilize foam can help to design a system with supper stable foam.
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Acknowledgment
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The funding from National Science Fund of China (No. 21173134) and National Municipal Science and
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Technology Project (No.2008ZX05011-002) is gratefully acknowledged. Thanks Dr. M. Tang (P﹠G) for the
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Tables Table 1
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The foamability and half life time (thalf) of the foams formed from surfactant or polymer solution using N2 or CO2 as gas agent. T=30±0.1 Time for forming 150ml Foam/s
thalf of N2 foam/h
thalf of CO2 foam/h
Life time of lamellar foam film in air/min
0.3 wt% SDS 0.1 wt% HMPAA
42 49
10 90
0.5 4
50 110
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Concentration of foam stabilizer
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Figure Captions Fig. 1. The schematic of the film permeability measurement equipment. a is gas cell, b is glass container, c is
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quartz tube, e and f are silicone tube, p1 – p4 are pistons. During the experiment the gas cell is always in the
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test chamber.
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Fig. 2. Variation of the thalf (•) of CO2 foam formed from HMPAA solution and HMPAA solution viscosity (•) as a function of concentration of polymer.
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Fig. 3. Variation of dynamic apparent viscosity of foams formed from SDS 0.3 wt% (●) and HMPAA 0.1 wt%
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(▲) under rotation as a function of time. The inset shows the curve of the SDS foam in detail.
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HMPAA 0.1 wt%(▲).
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Fig. 4. The variation of liquid fraction of the foams as a function of time: formed from SDS 0.3 wt%(●) and
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Fig. 5. The images of foams formed from different solutions: 0.3 wt% SDS (a, d), 0.05 wt% HMPAA (b, e), 0.1 wt% HMPAA (c, f). (a, b, c) images were taken immediately after the foam was formed. (d ,e, f) images were taken after 20 min, and the histogram of the bubble size was shown in the right of the images.
Fig. 6. (a), the fluorescence microscopy image of bulk phase solution of HMPAA. (b), the fluorescence microscopy image of bubbles in HMPAA solution. (c), the optical microscope image of bubbles in HMPAA solution. (d), the optical microscope image of bubbles in SDS solution.
Fig. 7. The images of foam films: microscope (a, b), fluorescence microscope (c, d), and TEM (e, f). (a, c, e) is of film formed from 0.05 wt% HMPAA solution; (b, d, f) is of film formed from 0.1 wt% HMPAA solution.
20 Page 20 of 33
Fig. 8. Snapshots of the equilibrium configuration of HMPAA foam film in MD simulation. The atoms drawn
Fig. 9. FT-IR spectra of foam film formed from (a) SDS and (b) HMPAA solutions.
Ac ce p
te
d
M
an
us
cr
Fig. 10. CO2 absorption peaks in (a) SDS and (b) HMPAA condition.
ip t
as van der Waals spheres are shown as small colored sphere: C, gray; H, white; O, red.
21 Page 21 of 33
ip t cr us an M Ac ce p
te
d
Figure 1
22 Page 22 of 33
ip t 0.20
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4.75
0.15
4.50 4.25 4.00
0.10 0.05 0.00
M
3.75 3.50
Viscosity (Pa•s)
0.25
half life viscosity
an
Half life time (h)
5.00
cr
5.25
0.040.060.080.100.120.140.160.180.20
d
Concentration (wt%)
Ac ce p
te
Figure 2
23 Page 23 of 33
ip t cr
SDS HMPAA
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3.5 3.0 1.05 1.00
2.0
1.0
0.85 0.80 0.75 0.70 0.65 0.60
10
20 30 Time (min)
400 600 Time (min)
800
d
0
200
Ac ce p
te
0.5
0.90
M
1.5
0.95
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2.5
Foam Viscosity (mPa/s)
Foam Viscosity (mP/s)
4.0
0
40
50
1000
Figure 3
24 Page 24 of 33
12
cr
10
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SDS HMPAA
8
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6 4 2 0 400
800
1200 1600 2000
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0
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Liquid Fraction (%)
14
Time (s)
Ac ce p
te
d
Figure 4
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ip t cr us
Ac ce p
te
d
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Figure 5
26 Page 26 of 33
ip t cr us
Ac ce p
te
d
M
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Figure 6
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Ac ce p
te
d
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Figure 7
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Ac ce p
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d
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Figure 8
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85 80 75 70
cr
a
60 400 800 1200 1600 2000 2400 2800 3200 3600 4000
-1
Wavenumber (cm )
-1
Wavenumber (cm )
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d
M
an
Figure 9
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65
Ac ce p
Transmittance (%)
90
100 0 min 90 b 0.5 min 80 1 min 1.5 min 70 2 min 60 2.5 min 50 3 min 40 4 min 5.5min 30 20 10 0 400 800 1200 1600 2000 2400 2800 3200 3600 4000
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0 min 0.5 min 1 min 1.5 min 2 min 2.5 min 3 min 4 min 5 min
95
Transmittance (%)
100
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60
40
95
20
90 85 80 75
2250
2300
2350
2400
2450
70 2200
2500
2300
2400
2500
Wavenumber (cm-1)
Wavenumber (cm -1)
cr
0 2200
0 min 2 min 5 min 10 min 20 min 30 min 40 min 50 min 60 min
b
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d
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an
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Figure 10
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Transmittance (%)
80
100
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0 min 2 min 5 min 10 min 20 min 30 min 40 min 50 min 60 min
a
Transmittance (%)
100
31 Page 31 of 33
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Graphical Abstract
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Ultra-stable aqueous foam stabilized by water-soluble alkyl acrylate crosspolymer (HMPAA) was
M
introduced. The HMPAA molecules adsorbed at the gas/water interface could interact with each other to form network structure through the hydrophobic force, and the interface could be covered very well.
d
Besides, huge amount of water molecules was found to be strapped in the foam film and would not be
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drained out. Therefore the gas permeability of HMPAA foam film was low, and the coalescence of
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bubbles in the foam was postponed.
32 Page 32 of 33
Highlights The foam formed from HMPAA solution was ultra-stable. The foam films characteristics were measured by FT-IR.
Ac ce p
te
d
M
an
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cr
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The mechanism of the foam stability was revealed by diverse techniques.
33 Page 33 of 33
S0927-7757(14)00530-5 http://dx.doi.org/doi:10.1016/j.colsurfa.2014.05.070 COLSUA 19271
To appear in:
Colloids and Surfaces A: Physicochem. Eng. Aspects
Received date: Revised date: Accepted date:
4-3-2014 22-5-2014 27-5-2014
Please cite this article as: W. Lv, Y. Li, Y. Li, S. Zhang, Q. Deng, Y. Yang, X. Cao, Q. Wang, Ultra-stable aqueous foam stabilized by water-soluble alkyl acrylate crosspolymer, Colloids and Surfaces A: Physicochemical and Engineering Aspects (2014), http://dx.doi.org/10.1016/j.colsurfa.2014.05.070 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Ultra-stable aqueous foam stabilized by water-soluble alkyl acrylate
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crosspolymer
Key Laboratory of Colloid and Interface Chemistry of State Education Ministry, Shandong University, 27
b
an
South Shanda road, Jinan, Shandong, 250100, P. R. China
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a
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Weiqin Lva, Ying Lia*, Yaping Lia, Sen Zhanga, Quanhua Denga, Yong Yangb, Xulong Caob, and Qiwei Wangb
Geological Scientific Research Institute, Shengli Oilfield, 3 Liaocheng road, Dongying, Shandong, 257100, P.
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R. China
∗
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te
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[email protected]
Prof. Dr. Ying Li
School of Chemistry and Chemical Engineering
Shandong University
27 Shanda Nanlu, Jinan, Shandong, P. R. China 250100 Tele: +86-531-88362078 Fax: +86-531-88364464 Email: [email protected]
1 Page 1 of 33
Abstract
Aqueous foam solely stabilized by a kind of hydrophobic modified water-soluble polymer, alkyl acrylate
ip t
crosspolymer (HMPAA), was found to be extraordinary stable, no matter in static state or under disturbance,
cr
even if CO2 was used as gas agent. The high water-holding capacity of HMPAA foam film demonstrated by
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FoamScan and FT-IR measurement was in accordance with the low gas transmission through the foam film, which was detected by FT-IR, too. Fluorescence Microscope, TEM and Molecular Dynamic (MD) simulation
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were used to get information about the adsorption and array behavior of HMPAA on the gas/water interface
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and in foam film, it was found that the comb polymer molecules adsorbed on the interface clustered to form plat network, which covered the interface very well like a “shell”. By combining all these results, the
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foam aqueous foam was proposed.
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mechanism of ultra high foam stability of HMPAA was revealed, and a novel approach to achieve long-term
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Keywords: Ultra-stable foam; Water-soluble polymer; Fluorescence microscopy; FT-IR; CO2 foam
2 Page 2 of 33
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1. Introduction
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Aqueous foam is a system that gas dispersed in liquid which has been widely used in daily life and
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industrial applications, such as extinguishing fires, mineral floatation, enhanced oil recovery, food industry,
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personal care products, etc. [1-3]. In many applications, the foam is required to have long-term stability. This is an ongoing technical challenge because foam is a multiphase dispersed system with highly developed
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interface. This makes the foam system is thermodynamically and kinetically unstable. After the foam is generated, the thinning of foam film caused by liquid drainage, coalescence of the foam bubbles would be
te
d
aggravated by continuous diffusion of gas through the foam film, the rupture of foam films occur constantly, and both would be strengthened under disturbance
[4-11]
. How to dramatically increase the stability of the
Ac ce p
aqueous foam is always a huge challenge for not only theoretical research but also application technology.
In typical industrial applications of aqueous foam, for example, foam flooding in EOR
[12]
, Nitrogen, air
and CO2 are usually used as the gas agents. In recent years, the underground injection of greenhouse gas for storage or displacement attracted much more attention
[13]
, and CO2 foam flooding in oil recovery which uses
captured CO2 from flue gas is one of the most impressive techniques [14-17]. However, aqueous foam using CO2 as foaming gas is much more difficult to be stabilized as compared with that of N2 and air. Therefore, developing technologies that can be used to improve the stability of CO2 foam is of technical and application value.
3 Page 3 of 33
Surfactant is one of the most typical type of the aqueous foam stabilizers
[5, 11, 18]
. However, the stability
of foam formed from surfactant solution is not always satisfied, especially under harsh conditions, such as high
ip t
temperature, high salt concentration, or CO2 being used as gas agent. Recently, ultra-stable aqueous foam stabilized by polymer rods or solid particle with or without surfactant has been reported [23]
. For example,
produced extraordinary stable foams using hydrophobic polymer microrods,
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Alargova and coworkers
[19-28]
[27]
reported foams and emulsions with extraordinary stability by using
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bubbles to keep bubbles stable. Wege
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which interacted with each other like dense thick “hairy” forming rigid intertwined protective shells around the
hydrophobic cellulose microparticles formed in situ with a liquid-liquid dispersion technique. However, the
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use of unsoluble polymer rods or particles could be limited in the production applications.
[29-31]
was used as aqueous foam stabilizer. It was
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In this paper, alkyl acrylate crosspolymer HMPAA
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found out that the foam formed from HMPAA solution has extremely high static and dynamic stability, not
Ac ce p
only for foams using N2 and air as gas agent, but also for that using CO2. The drainage of foam and the change of foam film following drainage process were measured by FoamScan and FT-IR. The transmission of gas through foam film was also determined by FT-IR. The behavior of polymer molecules in bulk phase and foam film was investigated by fluorescence microscopy, TEM and molecular simulation. Through all the results, the mechanism of ultra stability of foam was revealed, which represented a novel approach to achieve long-term foam stability.
2. Materials and Methods 2.1. Materials
4 Page 4 of 33
The alkyl acrylate crosspolymer HMPAA used in the paper was introduced in detail in our previous study [30]
, of which the ingredient ratio of hydrophobic modified segments is 10%, the average molecular weight is
ip t
about 100, 000. The aqueous solutions of HMPAA were prepared by following procedure: a certain amount of polymer was added in water, the solution was kept stirred using magnetic stirrer at 30 •±0.1• for 24 h before
us
cr
used in further measurement.
Anionic surfactant Sodium dodecyl sulfate (SDS, purity >99%), was bought from Sigma Aldrich. The
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fluorescent indicator Rhodamine B (purity >99%) was purchased from Aladdin. Freshly distilled water (twice
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distilled) was used in all solution preparations.
2.2. Methods
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2.2.1. The Measurement of Static Foam Stability
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The FoamScan device (TECLIS, France) was utilized to monitor foam properties (foamability, foam stability and drainage)
[32, 33]
. The bubble sizes can be analyzed with the cell size analysis (CSA) function
(TECLIS, France) which allows for a visualization of the bubbles coalescing process. In our experiments, an initial liquid volume of Vs = 60 ml was foamed by sparking N2 through a porous disk (pore sizes = 40-100 μm) at a constant gas flow rate 100 ml/min. The total foam volume reached to 150 ml, the changing of the volume of solution and the liquid fraction in the foam column were measured by three electrodes. The electrodes were named as the first, the second and the third electrode from the bottom, middle and top of the foam column respectively. Pictures of the foams were recorded using the cell size analysis (CSA) camera. The CSA
5 Page 5 of 33
software from TECLIS was used to analyze the bubble size. The mean diameter and mean area of the bubbles
2.2.2. Dynamic Stability of Foam
[5]
. The foam column was
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The dynamic foam stability was determined using rotor-disturbing method
ip t
the size distribution and other parameters could be obtained from the analysis.
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formed and contained in a transparent glass bucket with interlayer, which is connected with water bath, the temperature was kept at 30±0.1•. The apparent viscosity of the foam was measured right after being formed,
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with a Digital Viscometer NDJ-8S with #2 cylinder rotor. The rotation speed of the rotor was kept at 6 rpm
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and the shearing stress was fixed in the determination. The apparent foam viscosity under disturbing was
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observed.
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constantly recorded until the foam column collapsed. The data were recorded when reproducible values were
Ac ce p
2.2.3. Fluorescence Microscope Observation
Rhodamine B (0.0002 wt%) was used as the fluorescence label of the polymer chain. For bulk phase observing, the HMPAA solution was dropped in a silica square cell. For foam film observing, appropriate volume of HMPAA solution was deposited on a wire mesh with the grid radius of 0.1mm to form thin film. One drop of Rhodamine B solution (0.0002 wt%) was dropped on the mesh. Then the fluorescence microscope image was taken with Olympus BX53 Microscope (Olympus, Japan). Green filter was utilized for imaging.
2.2.4. Transmission Electron Microscope (TEM)
6 Page 6 of 33
Appropriate volume of HMPAA solution was deposited on a 5mm×5mm copper grid to form thin foam film. One drop of phosphotungstic acid solution was dropped, and quickly dried under IR light. The JEM-
ip t
100CX • (100kV) was used.
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2.2.5. Molecular Dynamics Simulation
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A reasonable double-layer film model was prepared for the simulation of the wet foam films. A 65×20×105 grid containing 10 polymer molecules which contain 25 repeating units, 6000 water molecules
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were used. The details were introduced in our early study [5, 11].
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The layer was first minimized by smart minimize algorithm with 50000 steps to avoid the possible
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molecule overlap and make the configurations more reasonable. After a 2 ns MD equilibration period, at least a
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1 ns MD production was run to obtain the dynamic information, the result of which was used for analysis.
Ac ce p
2.2.6. Detection of Foam Film Characteristics by Fourier Transforms Infrared Spectroscopy (FT-IR)
Nicolet IS5 (Thermo Fisher Scientific) was used to measure the FT-IR spectroscopy in the frequency range of 4000−400 cm−1, at a resolution of 1 cm−1 with a total of 16 scans. A quartz tube (90mm long, 8mm diameter) was placed in the test chamber. A vertical foam film was formed inside the tube by blowing HMPAA solution through a capillary and was scanned constantly as a function of time.
(Figure 1)
A setup as shown in figure 1 was used in measurement of the gas permeability of the foam film. A sealed gas cell with pistons full of nitrogen was put into the test chamber and scanned as background. A quartz tube
7 Page 7 of 33
(Ф8mm, 90mm long), inside of which a vertical foam film was formed in advance, was connected with the glass column through silicone tube on one side, and connected with a glass container which was full of CO2 on
ip t
the other side. Turned on the piston 2 on the class cell first, and then open the piston 3, the spectroscope was
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scanned constantly as a function of time. 3. Results and Discussion
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3.1. The Static Foam Stability
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The foamability and foam stability of HMPAA was determined using gas flow method by FoamScan. The time needed to get equal volume of foam was recorded to represent the foamability. There is no significant
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difference between the time needed to get 150ml foam from 60 ml 0.1 wt% HMPAA and 0.3 wt% SDS, as
d
shown in Table 1. The foam evolution was monitored as a function of time to reflect the foam stability, the half
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life time thalf was also listed in table 1. According to the results, the thalf of the N2 foam stabilized by HMPAA
Ac ce p
could be about 90 h, which is ten times longer than that stabilized by SDS. For CO2 foam, the thalf of the foam formed from HAPAA solution was about 8 times as that of SDS. And the life time of foam lamellar film formed from 0.1 wt% HMPAA solutions in air were much longer than that from 0.3 wt% SDS which was 110 and 50 min respectively [11]. It was obvious that the aqueous foam stabilized by HMPAA is much more stable than that stabilized by SDS.
(Table 1) (Figure 2) The critical associative concentration (CAC) of HMPAA in aqueous solution is determined to be about 0.08 wt%, which was shown in figure 2. It can be seen that even the CO2 foam formed from much diluted
8 Page 8 of 33
HMPAA solution demonstrated very good stability, the thalf could be hours. The bulk phase viscosity of HMPAA solutions showed a linear increase with the increase of concentration above CAC. The half life time
ip t
of the CO2 foam increased with the increase of HMPAA concentration above CAC, too. But the thalf curve became flatten when the HMPAA concentration is higher than 0.12 wt.%, which did not coincide with the
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constant increase tendency of the bulk phase viscosity as a function of concentration, especially when the
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viscosity is higher than 0.2 Pa·s. The high stability of the foam formed from HMPAA solution is not solely
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linked to the increase of the bulk phase viscosity. 3.2. The Dynamic Foam Stability.
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(Figure 3)
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The measurement of apparent viscosity of the foam column as a function of time is shown in Figure 3.
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The end of the curve indicated the collapse of the foam column, which reflects the dynamic foam stability
Ac ce p
under disturbing. In SDS foam, the apparent viscosity slightly increased at the initial period, which was induced by the adhension effect aroused from the thinning of foam film following gravitational drainage, and then decreased because of the collapse of the foam. The apparent viscosity of the foam formed from HMPAA solution was much higher than that from SDS solution. There was a increase of the foam viscosity coursed by drainage initially, too. But the apparent viscosity of HMPAA foam still maintain high even under shear for hours, the life time of HMPAA foam is almost 20 times longer that of SDS foam under the same disturbing condition, which showed solidly that the HMPAA foam is outstandingly dynamically stable.
3.3. Determination about the Foam Drainage and Coalescence of Bubbles.
9 Page 9 of 33
The time evolution of the liquid fraction of the foam column was monitored directly after the foam was generated to give out information about drainage. The measurement data of the third electrode was shown in
ip t
figure 4. The peak value of the curve represents the initial liquid fraction of the fresh foam, which are 13.5% and 7.5% for HMPAA and SDS foam respectively. This indicates that the HMPAA foam has greater water-
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carrying capability. During the drainage process the liquid fraction decreased until it reaches a constant level,
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The finial liquid fraction reflect the water-holding capacity, which is 5% for HMPAA foam and almost 0 for
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SDS foam. Therefore there is very little amount of water remained in the SDS foam film after complete drainage. It is very clear that both the water-carrying capability and the water-holding capacity of the HMPAA
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foam is high. These phenomena provide important clue for why the HMPAA foam has high static and dynamic
Ac ce p
te
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stability.
(Figure 4)
(Figure 5)
In the above experiment, the difference of foams bubble sizes for the two foam systems attracted our attention. According to images in figure 5, the initial bubbles size of the HMPAA foam is bigger than that of SDS. After 20 min, the bubble size of SDS foam increases about 10 times than initial, while the bubbles size of HMPAA foam just changed slightly. This suggests that the coalescence of bubbles in HMPAA foam is efficiently retarded. It is necessary to point out that the bubble size of the foam formed from HMPAA solution
10 Page 10 of 33
at very low concentration also increases distinctly, which shows that the coalescence of bubbles correlated with the adsorption amount of polymer molecules at gas/water interface.
ip t
3.4. The adsorption and array behavior of HMPAA on Gas/water interface and in Foam Film.
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Figure 6 (a) is the fluorescence microscopy image of bulk phase, it was found that the polymer molecules
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was distributed uniformly in the bulk phase solution. Figure 6 (b) is the fluorescence microscopy image of the same solution except for bubbles being put into the solution. It was clear that HMPAA molecules had the
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tendency to be adsorbed at the air/water interface. The thickness of the air/water interfacial layer was smaller
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than the size of the polymer aggregations in bulk phase. This can be due to that polymer opens its structure when it is adsorbed at the interface driven by the hydrophobic side chains. The bubbles in HMPAA solution
te
d
were covered very well by HMPAA molecules at the air-water interface which led to the decrease of the light transmittance in the foam, as shown in Figure 6 (c). However, in SDS system there is no light transmittance
Ac ce p
reduction across the bubbles.
(Figure 6)
Figure 7 showed the microscope, fluorescence microscope and TEM images of foam films formed from 0.05 wt% HMPAA solution and 0.1 wt% HMPAA solution. According to Figure 6, the polymer chains curled up and present as an aggregation state at low concentration (
11 Page 11 of 33
determined to be 28.64 mN/m, which is surely higher than normal surfactants. The results agreed very well with that in figure 2 and 5.i.e. full coverage of interface in foam film by the polymer molecules was important
ip t
to maintain high foam stability.
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(Figure 7)
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In order to get detailed information about the HMPAA molecular behaviour at the gas/water interface, molecular dynamics (MD) was used to simulate the foam film, and one of the snapshots was shown in Figure
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8. It was shown that, in the foam film, the hydrophobic side of HMPAA stretched out into the gas phase, the
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main chain docked beneath the gas/water interface and draw close to each other clustering, thus explained how the protective “shell” structure around the bubbles in figure 6 (b, c) could be formed. This simulation result
(Figure 8)
Ac ce p
te
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agrees very well with the experimental observation, and more systematic works are under going.
3.5. Characteristics of the Foam Film Detected by FT-IR.
The FT-IR spectroscopes of foam film formed from SDS and HMPAA solution were shown in figure 9. The absorption band around 1640 cm-1 and the region from 3200 to 3600 cm-1 all correspond to vibration modes of OH. The peak around 2350 cm-1 corresponds to the characteristic absorption of C-O. As shown in figure 9 a and b, all the absorption peak belong to water molecules got weakened quickly for SDS foam film, which means that the amount of water in the foam film decreases quickly along the drainage process. While all the absorption peaks belonging to water molecules do not change so much for the HMPAA foam film, and the
12 Page 12 of 33
light transmittance was very low. These indicated that the water content of HMPAA foam film was very high. This is consistent with previous observation that water-holding capacity was notably good. Therefore plenty of
ip t
water molecules was entrapped in the foam film and could not be drained out.
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(Figure 9)
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(Figure 10)
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The gas permeability of foam film was detected by FT-IR, the results was shown in figure 10 a) and b). The CO2 transmitted across the foam film decreased because of the light adsorption of CO2 molecules. It can
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be seen that the gas permeability of HMPAA foam film was much lower than that of SDS. This agrees very
d
well with that shown in figure 7 and 8 and further confirms that the gas/water interface was well covered by
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interacted polymer chains. In this case the thickness of interfacial layer is too high to allow the gas
Ac ce p
transmission efficiently. The interfacial layer of surfactant does not have such effect, so the gas could easily transmit through the foam film, and the coalescence of foam bubbles was easily to happen. The FT-IR results correspond perfectly with the experimental results mentioned above. 4. Conclusion
Ultra-stable aqueous foam was obtained using comb water-soluble polymer HMPAA as foam stabilizer. The influences of the polymer behavior and foam film properties on the foam stability have been discussed. It was found that the HAPAA molecules can be adsorbed onto air-water interface and interact with each other to form network structure through the hydrophobic and hydrogen bond interaction. The gas-water interface is therefore covered with the structured network. As a result, the thickness of the foam film of HMPAA was
13 Page 13 of 33
observed to be high and huge amount of water molecules were also trapped and hard to be drained out. Therefore the gas permeability of HMPAA foam film became low which makes and the coalescence of
ip t
bubbles in the foam was postponed. According to above, the aqueous foam stabilized by HMPAA becomes extremely stable, even under disturbing or using carbon dioxide as gas agent. We believe that our mechanisms
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on how HMPAA helps to stabilize foam can help to design a system with supper stable foam.
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Acknowledgment
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The funding from National Science Fund of China (No. 21173134) and National Municipal Science and
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Technology Project (No.2008ZX05011-002) is gratefully acknowledged. Thanks Dr. M. Tang (P﹠G) for the
Reference
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helpful discussion during the revise course of this work.
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[18] K. Golemanov, N. D. Denkov, S. Tcholakova, Surfactant Mixtures for Control of Bubble Surface Mobility in Foam Studies, Langmuir 24 (2008) 9956-9961.
[19] U. T. Gonzenbach, A. R. Studart, E. Tervoort, Stabilization of Foams with Inorganic Colloidal Particles, Langmuir 22 (2006) 10983-10988.
[20] U. T. Gonzenbach, A. R. Studart, E. Tervoort, Macroporous Ceramics from Particle•Stabilized Wet Foams, J. Am. Chem. Soc. 90 (2007) 16-22.
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[21] B. P. Binks, T. S. Horozov, Aqueous Foams Stabilized Solely by Silica Nanoparticles, Angew. Chem. Int. Ed. 117 (2005) 3788-3791.
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[22] U. T. Gonzenbach, A. R. Studart, E. Tervoort, Ultrastable Particle Stabilized Foams, Angew. Chem. Int.
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Ed. 45 (2006) 3526-3530.
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[23] R. G. Alargova, D. S. Warhadpande, V. N. Paunov, Foam Superstabilization by Polymer Microrods,
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Langmuir 20 (2004) 10371-10374.
[24] A. L. Fameau, A. Saint•Jalmes, F. Cousin, Smart Foams: Switching Reversibly between Ultrastable and
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Unstable Foams, Angew. Chem. Int. Ed. 50 (2011) 8264-8269.
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[25] R. Petkova, S. cholakova, N. D. enkov, Foaming and Foam Stability for Mixed Polymer–Surfactant
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Solutions: Effects of Surfactant Type and Polymer Charge, Langmuir 28 (2012) 4996-5009.
Ac ce p
[26] N. Kristen-Hochrein, A. Laschewsky, R. Miller, Stability of Foam Films of Oppositely Charged Polyelectrolyte/Surfactant Mixtures: Effect of Isoelectric Point, J. Phys. Chem. B 115 (2011) 14475-14483.
[27] H. A. Wege, S. Kim, V. N. Paunov, Long-Term Stabilization of Foams and Emulsions with In-Situ Formed Microparticles from Hydrophobic Cellulose, Langmuir 24 (2008) 9245-9253.
[28] Z. G. Cui, Y. Z. Cui, C. F. Cui, Aqueous Foams Stabilized by In Situ Surface Activation of CaCO3 Nanoparticles via Adsorption of Anionic Surfactant, Langmuir 26 (2010) 12567-12574.
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[29] O. E. Philippova, D. Hourdet, R. Audebert, pH-Responsive Gels of Hydrophobically Modified Poly (Acrylic Acid), Macromolecules 30 (1997) 8278-8285.
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[30] Q. Li, R. Yuan, Y. Li, Study on The Molecular Behavior of Hydrophobically Modified Poly (Acrylic
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Acid) in Aqueous Solution and Its Emulsion•Stabilizing Capacity, J. Appl. Polym. Sci. 128 (2013) 206-215.
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[31] K. T. Wang, I. Iliopoulos, R. Audebert, Viscometric Behaviour of Hydrophobically Modified Poly
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(Sodium Acrylate), Polymer Bulletin 20 (1988) 577-582.
[32] E. Carey, C. Stubenrauch, Properties of Aqueous Foams Stabilized by Dodecyltrimetylammonium
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Bromide, J. Colloid. Interface Sci. 333 (2009) 619-627.
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[33] E. Carey, C. Stubenrauch, A Disjoining pressure Study of Foams Films Stabilized by Mixtures of
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Nonionic (C12DMPO) and an Ionic Surfactant (C12TAB), J. Colloid Interface Sci. 343 (2010) 314-323.
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Tables Table 1
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The foamability and half life time (thalf) of the foams formed from surfactant or polymer solution using N2 or CO2 as gas agent. T=30±0.1 Time for forming 150ml Foam/s
thalf of N2 foam/h
thalf of CO2 foam/h
Life time of lamellar foam film in air/min
0.3 wt% SDS 0.1 wt% HMPAA
42 49
10 90
0.5 4
50 110
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Concentration of foam stabilizer
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Figure Captions Fig. 1. The schematic of the film permeability measurement equipment. a is gas cell, b is glass container, c is
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quartz tube, e and f are silicone tube, p1 – p4 are pistons. During the experiment the gas cell is always in the
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test chamber.
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Fig. 2. Variation of the thalf (•) of CO2 foam formed from HMPAA solution and HMPAA solution viscosity (•) as a function of concentration of polymer.
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Fig. 3. Variation of dynamic apparent viscosity of foams formed from SDS 0.3 wt% (●) and HMPAA 0.1 wt%
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(▲) under rotation as a function of time. The inset shows the curve of the SDS foam in detail.
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HMPAA 0.1 wt%(▲).
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Fig. 4. The variation of liquid fraction of the foams as a function of time: formed from SDS 0.3 wt%(●) and
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Fig. 5. The images of foams formed from different solutions: 0.3 wt% SDS (a, d), 0.05 wt% HMPAA (b, e), 0.1 wt% HMPAA (c, f). (a, b, c) images were taken immediately after the foam was formed. (d ,e, f) images were taken after 20 min, and the histogram of the bubble size was shown in the right of the images.
Fig. 6. (a), the fluorescence microscopy image of bulk phase solution of HMPAA. (b), the fluorescence microscopy image of bubbles in HMPAA solution. (c), the optical microscope image of bubbles in HMPAA solution. (d), the optical microscope image of bubbles in SDS solution.
Fig. 7. The images of foam films: microscope (a, b), fluorescence microscope (c, d), and TEM (e, f). (a, c, e) is of film formed from 0.05 wt% HMPAA solution; (b, d, f) is of film formed from 0.1 wt% HMPAA solution.
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Fig. 8. Snapshots of the equilibrium configuration of HMPAA foam film in MD simulation. The atoms drawn
Fig. 9. FT-IR spectra of foam film formed from (a) SDS and (b) HMPAA solutions.
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d
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Fig. 10. CO2 absorption peaks in (a) SDS and (b) HMPAA condition.
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as van der Waals spheres are shown as small colored sphere: C, gray; H, white; O, red.
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Figure 1
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4.75
0.15
4.50 4.25 4.00
0.10 0.05 0.00
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3.75 3.50
Viscosity (Pa•s)
0.25
half life viscosity
an
Half life time (h)
5.00
cr
5.25
0.040.060.080.100.120.140.160.180.20
d
Concentration (wt%)
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Figure 2
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SDS HMPAA
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3.5 3.0 1.05 1.00
2.0
1.0
0.85 0.80 0.75 0.70 0.65 0.60
10
20 30 Time (min)
400 600 Time (min)
800
d
0
200
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0.5
0.90
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1.5
0.95
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2.5
Foam Viscosity (mPa/s)
Foam Viscosity (mP/s)
4.0
0
40
50
1000
Figure 3
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12
cr
10
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SDS HMPAA
8
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6 4 2 0 400
800
1200 1600 2000
M
0
an
Liquid Fraction (%)
14
Time (s)
Ac ce p
te
d
Figure 4
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Ac ce p
te
d
M
an
Figure 5
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Ac ce p
te
d
M
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Figure 6
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Ac ce p
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d
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Figure 7
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d
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Figure 8
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85 80 75 70
cr
a
60 400 800 1200 1600 2000 2400 2800 3200 3600 4000
-1
Wavenumber (cm )
-1
Wavenumber (cm )
te
d
M
an
Figure 9
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65
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Transmittance (%)
90
100 0 min 90 b 0.5 min 80 1 min 1.5 min 70 2 min 60 2.5 min 50 3 min 40 4 min 5.5min 30 20 10 0 400 800 1200 1600 2000 2400 2800 3200 3600 4000
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0 min 0.5 min 1 min 1.5 min 2 min 2.5 min 3 min 4 min 5 min
95
Transmittance (%)
100
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60
40
95
20
90 85 80 75
2250
2300
2350
2400
2450
70 2200
2500
2300
2400
2500
Wavenumber (cm-1)
Wavenumber (cm -1)
cr
0 2200
0 min 2 min 5 min 10 min 20 min 30 min 40 min 50 min 60 min
b
te
d
M
an
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Figure 10
Ac ce p
Transmittance (%)
80
100
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0 min 2 min 5 min 10 min 20 min 30 min 40 min 50 min 60 min
a
Transmittance (%)
100
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Graphical Abstract
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Ultra-stable aqueous foam stabilized by water-soluble alkyl acrylate crosspolymer (HMPAA) was
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introduced. The HMPAA molecules adsorbed at the gas/water interface could interact with each other to form network structure through the hydrophobic force, and the interface could be covered very well.
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Besides, huge amount of water molecules was found to be strapped in the foam film and would not be
te
drained out. Therefore the gas permeability of HMPAA foam film was low, and the coalescence of
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bubbles in the foam was postponed.
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Highlights The foam formed from HMPAA solution was ultra-stable. The foam films characteristics were measured by FT-IR.
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The mechanism of the foam stability was revealed by diverse techniques.
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