Effect of Foam Boosters on the Micellization and Adsorption of Sodium

Article pubs.acs.org/jced

Effect of Foam Boosters on the Micellization and Adsorption of Sodium Dodecyl Sulfate Ramesh R. Prajapati and Sunil S. Bhagwat* Department of Chemical Engineering, Institute of Chemical Technology, Matunga, Mumbai 400 019, India S Supporting Information *

ABSTRACT: The interactions between the anionic surfactant sodium dodecyl sulfate and various foam boosters such as cocodiethanolamide, cocoamidopropylbetaine, and monoethoxylated cocomonoethanolamide are investigated. Interfacial interactions between sodium dodecyl sulfate and foam boosters were assessed by the surface tension method. An increase in the mole fraction of foam boosters reduced the critical micelle concentration (CMC) of anionic surfactant. The strength of interaction for micellization (βM) and adsorption (β40) are calculated from surface tension studies. The zwitterionic foam booster cocoamidopropylbetaine showed strong synergistic interaction with sodium dodecyl sulfate for both adsorption and micellization.

1. INTRODUCTION Surfactants used in numerous applications, ranging from industrial to household products, are mostly mixtures, due to their superior properties as compared to pure surfactants. A cosurfactant or an additive is often added deliberately to enhance the properties of a surfactant solution. The synergistic interaction between surfactants is used in detergents, household applications, and various other formulations.1,2 Foam boosters are among the most effective and extensively used additives, to improve the foaming properties of commercial products. Alkanolamides and betaines are the types of foam boosters presently being used for practical applications.3,4 The effect of these foam boosters on different surfactants and their properties have attracted the researchers into this field. The surfactant mixtures are known to have lower critical micelle concentration (CMC) values than the pure surfactant.1,5,6 In addition, foam boosters increase the viscosity of the surfactant solution and alter the softening and antistatic properties7 which make them important additives in the production of shampoo. The addition of foam boosters to surfactant causes an increase in the bulk viscosity by enhancing the packing at the air−liquid interface. It also helps in delaying the liquid drainage from the foam lamellae, thus resulting in higher foam stability.8 Basheva and co-workers3,4 reported similar behavior by lauric diethanolamide (LDEA) and cocoamidopropylbetaine (CAPB) in sodium dodecyl polyoxyethylene-3 sulfate (SDP3S) solution in the presence of silicone oil. The increase in foamability and foam stability in the presence of silicone oil are related to a very strong attraction between the molecules of SDP3S and the boosters in the adsorption layers (negative interaction parameter). Surface tension isotherms of dodecyl acid diethanol amide (DADA) with sodium dodecyl sulfate (SDS) and SDS− CAPB mixtures are also reported.9,10 It is shown that the © 2012 American Chemical Society

DADA molecule prevails more on the surface and in the micelles even though it is present in small fraction due to its higher surface activity compared to SDS. In studies consisting of a SDS−betaine mixture, the surface tension relaxation kinetics for the determination of equilibrium surface tension was established.9 Synergistic dependence of CMC on the composition of surfactant blend was established, and various properties including adsorption, elasticity, occupancy of Stern layer by bound counterions, and the surface electric potential were calculated. The appearance of cylindrical micelles in the SDS−CAPB system has also been identified11 at concentrations as low as 0.01 mol·kg−1, and it is shown to increase the viscosity. The above investigations suggest a strong attractive interaction in SDS−betaine mixtures in solution. The addition of alkanolamides to SDS proved effective in reducing the Krafft temperature by altering the CMC of the mixture.12,13 The decrease in the Krafft temperature was larger for surfactants with bivalent counterions as compared to the surfactants with monovalent counterions. Strong interaction or complex formation was reported by Tsujii and co-workers14 for a sulfobetaine−SDS mixed system. In the present study, the variation in the solution properties of binary mixture of SDS with foam boosters was investigated. The nature and strength of foam booster interaction with SDS both at the interface and inside the micelles is evaluated on the basis of molecular interaction parameter (β). This would help in evaluating the foam boosters on the basis of efficiency and effectiveness and their extent of interaction with SDS. Received: August 2, 2012 Accepted: November 1, 2012 Published: November 7, 2012 3644

dx.doi.org/10.1021/je3008155 | J. Chem. Eng. Data 2012, 57, 3644−3650

Journal of Chemical & Engineering Data

Article

Table 1. Specification of the Surfactant and Foam Boosters Used for Measurements chemical name

source

purity/%

SDS CDEA CAPB

Sisco Research Lab Pvt. Ltd. Galaxy Surfactants Ltd. Galaxy Surfactants Ltd.

> 99.9 % 94.96 % 83.17 %

CMEA(EO)1

Galaxy Surfactants Ltd.

98.5 %

compositions of mixture on dry basis C12H25SO4Na C8H17−C4H10NO3 to C18H37−C4H10NO3, free fatty acid (0.26 %), free amine (4.78 %) C8H17−C7H15N2O3 to C18H37−C7H15N2O3, free fatty acid (1.34 %), free amine (1.09 %), NaCl (14.39 %) C8H17−C4H10NO3 to C18H37−C4H10NO3, free fatty acid (0.5 %), free amine (1.0 %)

2. EXPERIMENTAL PROCEDURE 2.1. Materials. Anionic surfactant sodium dodecyl sulfate (SDS) (electrophoresis extrapure AR grade; average molar mass, 0.288 kg·mol−1) was procured from Sisco Research Laboratories Pvt. Ltd. India. Coconut oil fatty acid derivatives CDEA, CAPB, and CMEA(EO)1 were mixtures of alkyl chain comprising of C8H17 to C18H37 with the given average molar mass. Cocoamidopropylbetaine (CAPB) (average molar mass, 0.360 kg·mol−1), cocodiethanolamide (CDEA) (average molar mass, 0.298 kg·mol−1), and monoethoxylated cocomonoethanolamide (CMEA(EO) 1 ) (average molar mass, 0.297 kg·mol−1) were provided by M/s Galaxy Surfactant Ltd. (India). The CAPB is associated with nearly equimolar concentration of NaCl generated during manufacture and is mostly used along with this salt in final formulations.15 The experimental materials used in measurements are summarized in Table 1. The chemical structures of the three foam boosters (CAPB, CDEA, CMEA(EO)1) and pure surfactant (SDS) are shown in Figure 1. Distilled water of surface tension (71.0 ± 1.0) mN·m−1 and conductivity 0.0002 S·m−1 was used for preparing surfactant solutions for all experimental studies.

readings was within 1 %. The instrument was standardized by measuring the surface tension of water having a value of (71.0 ± 1.0) mN·m−1. All measurements were carried out at (298 ± 0.5) K using a thermostat (Thermo-Haake DC 10, Germany) that allowed constant temperature regulation to (298 ± 0.1) K. The desirable composition of the SDS−foam booster mixture was prepared by weighing a known amount of SDS and foam booster on balance procured from AND Company Ltd., model GR 202, with an accuracy of 0.01 mg. Further they were mixed in desirable compositions and diluted to desired concentration with distilled water. The solutions of different mixtures (of foam booster and SDS) were prepared by maintaining the total concentration constant and varying the relative proportions of SDS and the foam boosters to obtain the desired mole fraction within the surfactant mixture. The general representation of the same is as shown in eq 1. The total surfactant molality (S) is an addition of SDS molality (A) and foam booster molality (B). S=A+B

(1)

αA = A /(A + B)

(2)

The uncertainty in the mole fraction was around 0.1 %, and the uncertainty in the concentration of the prepared solution was within 1 %. The error in CMC values was less than 3 %, and the error in the corresponding beta values derived from it was estimated to be less than 5 %. The surface tension of aqueous SDS solution was measured at various total concentrations of SDS and a graph of surface tension against total concentration of SDS was plotted and is shown in Figure 2. Similarly for mixed surfactant (surfactant + foam booster) solutions the surface tension was measured at

Figure 1. Structure of surfactant and foam boosters I, sodium dodecyl sulfate; II, cocoamidopropylbetaine; III, cocodiethanolamide; IV, monoethoxylated cocomonoethanolamide.

2.2. Methods and Instrumentation. 2.2.1. Surface Tension Measurements. The steady state surface tension (γ) of pure surfactant and mixed surfactant solutions was measured using a Krüss K11 tensiometer by the Wilhelmy plate method. The platinum plate used for the measurement had dimensions of 20 × 10 × 0.1 mm (length × height × thickness). The plate was cleaned with distilled water and flamed before each measurement. Every surface tension value was an average of five readings at intervals of 30 s, and the final value is considered which had a relative standard deviation of less than 1 %. The experiments were repeated at least three times with fresh solutions, and the relative deviation of the average of five

Figure 2. Schematic representation of surface tension isotherm of SDS. The solid continuous curve () passing through data points (□) was fitted by Szyszkowski equation to obtain CMC and C20 values, and the horizontal line (- - -) above CMC gives the γmin value. 3645



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Table 2. Variation in Mixed CMC (Cmix) and CMC/C20 and γmin Values of SDS−Foam Booster Mixtures as a Function of Mole Fractions (α) of Foam Booster in Total Concentrationa 103·Cmix (exp) foam booster CDEA

CAPB

CMEA(EO)1

a

α 0.0 0.50·10−2 1.0·10−2 5.0·10−2 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 0.95 1.0 0.0 0.50·10−2 1.0·10−2 5.0·10−2 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.0 0.0 0.50·10−2 1.0·10−2 5.0·10−2 0.10 0.20 0.30 0.40 0.50 0.60 0.70 1.0

mol·kg

−1

103·Cmix (ideal) mol·kg

7.6 3.7 2.8 1.6 1.1 0.80 0.48 0.35 0.28 0.22 0.17 0.15 0.15 0.17 0.25 5.6 2.1 1.2 0.73 0.52 0.32 0.27 0.23 0.18 0.18 0.12 0.14 0.17 0.23 7.6 3.3 2.6 1.3 1.0 0.71 0.49 0.43 0.30 0.23 0.20 0.13

−1

7.6 6.6 5.9 3.1 1.9 1.1 0.77 0.60 0.48 0.41 0.35 0.31 0.28 0.26 0.25 5.6 5.0 4.5 2.6 1.7 0.99 0.70 0.54 0.44 0.37 0.32 0.28 0.25 0.23 7.6 5.9 4.8 2.0 1.1 0.61 0.42 0.32 0.26 0.21 0.18 0.13

103·γmin CMC/C20 (exp)

CMC/C20 (ideal)

N·m−1

3.9 23 22 30 33 49 48 35 35 33 40 44 41 36 30 12 25 17 9.2 10 5.4 5.7 21 4.3 28 14 8.8 10 92 3.9 15 22 25 9.4 37 18 34 24 23 19 33

3.9 3.9 3.9 4.1 4.3 4.7 5.3 6.0 6.9 8.2 10 13 18 22 30 12 12 12 13 13 15 16 18 21 25 31 39 55 92 3.9 3.9 3.9 4.1 4.3 4.7 5.3 6.0 7.0 8.3 10 33

37 36 36 35 35 33 32 32 30 29 28 28 26 27 28 37 36 35 35 33 31 30 30 30 29 29 29 30 34 37 37 36 35 34 32 32 28 28 27 27 26

Standard uncertainties u are u(α) = 0.0001, u(Cmix) = 1·10−6 mol·kg−1, u(CMC/C20) = 0.01, u(γmin) = 1·10−4 N·m−1.

The efficiency (C20) of a surfactant is defined as the concentration of surfactant required to reduce the surface tension of the solvent (usually water) by 20 mN·m−1. The effectiveness (γmin) of a surfactant is defined as the minimum surface tension achieved by a given surfactant irrespective of its concentration.

various total concentrations. The falling surface tension region was correlated using Szyszkowski equation (eq 3)1 and the post CMC (near horizontal) region was correlated as a straight line. γ0 − γ = π = nRT Γmax ln(1 + KC)

(3)

where γ0 and γ are the surface tension of the water and surfactant solution, π is a surface pressure (the reduction in surface tension), Γmax is maximum surface excess concentration, C is the concentration of surfactant, R is the universal gas constant, T is the absolute temperature, and n is a prefactor which is the number of ionizable species in the surfactant molecule. Thus, for ionic surfactants such as SDS the value of n is 2, and for nonionic surfactants the value of n is 1. K is the adsorption constant, and for SDS the value obtained is 2.9 m3·mol−1.

3. THEORY The pseudophase separation approach is a very effective tool for understanding micelle formation.16 In this model, the micelles and the monomeric molecules in the bulk with the adsorbed molecules at the interface are assumed to be in equilibrium with each other. The micelle is treated as a separate phase, and the condition of equality of the chemical potential in the different phases is applied. In ideal binary mixtures of 3646



Article

Figure 3. C40 against mole fractions (α) of foam boosters and the corresponding interaction parameter (β40) for mixed monolayer formation at the solution−air interface for various foam boosters. Graph a represents the SDS−CDEA system having β40 = −5.0, graph b represents the SDS−CAPB system in the presence of 0.01 mol·kg−1 of NaCl with β40 = −6.1, and graph c represents the SDS−CMEA(EO)1 system with β40 = −3.6, respectively. The solid line () represents the ideal values for the mixture. The dashed line (- - -) passing through data points is obtained by fitting the nonideal equation to experimental data. The horizontal dashedline (- - -) is the C40 value of pure surfactant SDS.

surfactants the CMC of the mixed surfactant system is related to the pure surfactant CMC by the Clint equation.17,16 α α 1 = 1 + 2 C12 C1 C2

(4)

where C12, C1, and C2 are the CMC values of the mixture, foam booster, and SDS. α1 and α2 are the mole fractions of the respective foam booster and SDS in the total mixed solute. The mole fractions of these species in the micelle (X1, X2) will be different from α1 and α2 and can be calculated as X1 =

X2 =

α1C12 C1 α2C12 C2

α α 1 = 1 + 2 C12 a1 a2

(7)

α α 1 = 1 + 2 C12 f1 C1 f2 C2

(8)

where f1 = exp[β(1 − X1)2] and f 2 = exp[β(X1)2] are the activity coefficients of foam booster and SDS. X1 is the mole fraction of foam boosters in the mixed micelle. In case of nonideal systems, X1 and X2 can be calculated from eqs 9 and 10. X1 =

(5)

α1C12 exp(β(1 − X1)2 )C1

(9)

where (1 − X1) = X2 (6)

X2 =

Some surfactant mixtures do not obey the above ideal mixture equation (eq 4) because the interaction between different species molecules is different from the interaction between molecules of the same species. Nonideality can be modeled by using a regular solution theory approach employing an adjustable parameter, β, developed by Rubingh and Mittal.18 β provides an indication of the degree of interaction between the foam booster and SDS and is assumed to remain constant across the whole range of composition. Negative β implies a negative deviation from ideality, that is, an attractive interaction. The more negative the β, greater the attraction. A positive β implies a repulsive interaction. A negative β indicates synergistic behavior, since the mixed surfactant has CMC lower than that calculated by the ideal mixed equation (eq 4). The CMC of a nonideal mixture can be calculated using eq 8 where the concentrations in eq 4 are replaced by activities (a1, a2).

α2C12 exp(β(X1)2 )C2

(10)

The interaction parameter β is obtained by minimizing the sum of squared differences between calculated C12 and experimental values of C12. The above eqs 4 and 8 can also be used for adsorption calculations by replacing the CMC values correspondingly with 40 40 C40 values (C40 12, C1 , and C2 ) which are the concentrations of the mixture, foam booster and SDS, when the surface tension reaches 40 mN·m−1. The molecular interaction parameter (β) at the solution−air interface is referred as β40, and X in this case will be the interfacial fraction within the foam booster− surfactant mixture. The β obtained from CMC values is termed as βM. The magnitude and sign of βM indicates the magnitude and nature of interaction within the micelle, while β40 is a measure of interaction in the adsorbed layer. The parameter β is thus an indication of whether synergism exists or not, in a given mixed binary system. 3647



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Figure 4. CMC of the mixture (Cmix) against mole fractions (α) of foam boosters and the corresponding interaction parameter (βM) for mixed micelle formation for various foam boosters. Graph a represents the SDS−CDEA system having βM = −3.2, graph b represents the SDS−CAPB system in the presence of 0.01 mol·kg−1 of NaCl with βM = −5.0, and graph c represents the SDS−CMEA(EO)1 system with βM = −2.5, respectively. The solid line () represents the ideal values for the mixture. The dashed line (- - -) passing through data points is obtained by fitting the nonideal equation to experimental data. The horizontal dashed line (- - -) is the CMC value of pure surfactant SDS.

The following two conditions must be complied for synergism to exist in mixed micelle formation: (1) βM must be negative and (2) |βM| > |ln(C1/C2)|.19 Both synergistic and antagonistic behavior of nonionic/nonionic, nonionic/ionic, and ionic/ionic surfactants is reported in literature.20

ratio is higher than that predicted using the ideal mixture theory. The higher CMC/C20 ratios suggest that, when the SDS−CDEA were mixed, adsorption is a favored process in comparison to micellization. This highlights the difficulty in the packing of SDS−CDEA in the micelles. The CMC of SDS−CAPB was studied in the presence of sodium chloride (0.01 mol·kg−1) using the technique described in Section 2.2.1. The SDS−CAPB system also showed a negative beta for both adsorption and micellization as seen from Figures 3b and 4b. It was due to the electrostatic attraction between the anionic SDS and zwitterionic foam booster CAPB.9 The observed C40 at every mole fraction was smaller than the ideal mixture predictions as observed from Figure 3b. The γmin at all of the mole fractions was lower than that of pure SDS surfactant, indicating a smaller headgroup area and tighter packing in the adsorption film. The CMC/C20 values are shown in Table 2. It was observed that CMC/C20 experimental values are smaller than the ideal mixture prediction values at all mole fractions, indicating effective packing of the SDS−CAPB micelle. In the case of SDS−CMEA(EO)1 system, a less negative beta was observed for both adsorption and micellization as compared to SDS−CDEA and SDS−CAPB systems. The plot of which is shown in Figures 3c and 4c. This could be due to a weak reduction in electrostatic repulsion. At low proportions of foam booster (i.e., below 0.1 mole fraction of CMEA(EO)1) it shows a synergistic interaction. However, as the mole fraction of CMEA(EO)1 increases, the SDS− CMEA(EO)1 system behaves more like an ideal system or shows preference to form their own micelles. The same can also be observed from the CMC values as shown in Table 2. It was also observed that the experimental CMC/C20 ratio is higher than that predicted using the ideal mixture theory, indicating difficulty in packing of SDS−CMEA(EO)1 in the micelles. The interaction between the surfactant and the foam boosters was analyzed by using Rubingh and Mittal regular

4. RESULTS AND DISCUSSION The CMC of SDS in all SDS−foam booster systems was lowered on the addition of foam booster as shown in Table 2. The interaction parameter for the solutions of SDS−foam booster mixture in the micelles (βM) and at the surface (β40) was calculated by fitting the CMC and C40 values with nonideal eq 8. The C40 was used for calculating the interaction parameter at surface because at this concentration almost entire surface is fully occupied by the surfactant monolayer.1 The CMC/C20 ratio indicates the preference of surfactant for micellization or adsorption. A higher CMC/C20 ratio implies that adsorption is preferred over micellization. The CMC of SDS−foam boosters was measured by a technique described in Section 2.2.1. In the SDS−CDEA system, a negative beta was observed for both adsorption and micellization as shown in Figures 3a and 4a. This is due to the decrease in electrostatic repulsion between SDS head groups caused by the presence of CDEA molecules between charged SDS head groups.10,13,21,22 The C40 value at all mole fractions was smaller than the ideal C40 calculated from a similar equation as shown in eq 4. Also, the γmin values at every mole fraction was smaller than the γmin value of the pure surfactant, indicating a smaller headgroup area and a tightly packed adsorbed film. However, a less negative βM value was observed in the case of micellization of the mixture as shown in Figure 4a. The less negative βM value observed for micellization indicates a weak interaction between the SDS−CDEA molecules. The data of ideal and experimental values for SDS−CDEA system are given in Table 2. It was observed that the experimental CMC/C20 3648



■

solution theory.18 The interaction parameter β was calculated for all of the systems. The magnitude of the interaction parameters in both mixed micelle (βM) and mixed monolayer (β40) is listed in Table 3.

a

βM

β40

βM−β40

SDS−CDEA SDS−CAPB SDS−CMEA(EO)1

−3.2 −5.0 −2.5

−5.0 −6.1 −3.6

1.8 1.1 1.1

ASSOCIATED CONTENT

S Supporting Information *

This material is available free of charge via the Internet at http://pubs.acs.org.

■

Table 3. Effect of Various Foam Boosters with SDS on Interaction Parameter Values, for Both Adsorption (β40) and Micellization (βM), and the Differences between Them (βM−β40)a mixture

Article

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Telephone: +91-223361-2001/2011. Fax: +91-22-3361-1020. Notes

The authors declare no competing financial interest.

■ ■

ACKNOWLEDGMENTS The authors would like to thank M/s Galaxy Surfactant for providing the foam booster samples.

Standard uncertainties u are u(β) = 0.01.

Another important parameter is the difference between βM−β40, which gives the extent and the direction of interaction. A positive βM−β40 indicates that the attractive interactions in the mixed adsorbed layer are greater than the interactions in the mixed micelle or that the repulsive interactions in the adsorbed layer are weaker than that in the mixed micelle. A negative βM−β40 means that the attractive interactions in the mixed micelles are greater than that of the mixed adsorbed layer or that the repulsive interactions in the mixed micelles are weaker than the repulsive interactions in the adsorbed layer. The SDS−foam booster systems have their average value of β40 negative, indicating synergistic interaction at the surface. Compared to the β40 value, a less negative βM value shows weak interaction behavior, suggesting strong synergism in the mixed monolayer than in a mixed micelle. Furthermore, it was observed that all systems had a positive difference between β40 and βM values. A positive difference in βM−β40 suggested the reduction of electrostatic interaction and indicated a greater effect at the surface than in the micelle as shown in Table 3 for all SDS−foam booster systems. In all systems, it can be observed that the interaction at surface was more as compared to micelles. This suggests that adsorption is more favored in all of these systems than micellization.

REFERENCES

(1) Rosen, M. J. Surfactants and Interfacial Phenomena, 2nd ed.; John Wiley and Sons: New York, 1989. (2) Zhou, Q.; Rosen, M. J. Molecular Interactions of Surfactants in Mixed Monolayers at the Air/Aqueous Solution Interface and in Mixed Micelles in Aqueous Media: The Regular Solution Approach. Langmuir 2003, 19, 4555−4562. (3) Basheva, E. S.; Ganchev, D.; Denkov, N. D.; Kasuga, K.; Satoh, N.; Tsujii, K. Role of Betaine as Foam Booster in the Presence of Silicone Oil Drops. Langmuir 2000, 16, 1000−1013. (4) Basheva, E. S.; Stoyanov, S.; Denkov, N. D.; Kasuga, K.; Satoh, N.; Tsujii, K. Foam Boosting by Amphiphilic Molecules in the Presence of Silicone Oil. Langmuir 2001, 17, 969−979. (5) Hines, J. D.; Thomas, R. K.; Garrett, P. R.; Rennie, G. K.; Penfold, J. Investigation of Mixing in Binary Surfactant Solutions by Surface Tension and Neutron Reflection: Strongly Interacting Anionic/Zwitterionic Mixtures. J. Phys. Chem. B 1998, 102, 8834− 8846. (6) Zhu, Z. H.; Rosen, M. J. Synergism in Binary Mixtures of Surfactants. 7. Synergism in Foaming and its Relation to other types of Synergism. J. Am. Oil Chem. Soc. 1988, 65, 663−668. (7) Ernst, R.; Miller, E. J., Jr. Surface Active Betanies. In Amphoteric Surfactants; Blustein, B., Hilton, C., Eds.; Marcel Dekker, Inc.: New York, 1982; Vol. 12, Chapter 2, pp 71−173. (8) Sawyer, W. M.; Fowkes, F. M. Interaction of Anionic Detergents and Certain Polar Aliphatic Compounds in Foams and Micelles. J. Phys. Chem. 1958, 62, 159−160. (9) Danov, K.; Kralchevska, S.; Kralchevsky, P.; Ananthapadmanabhan, K.; Lips, A. Mixed Solutions of Anionic and Zwitterionic Surfactant (Betaine): Surface-Tension Isotherms, Adsorption, and Relaxation Kinetics. Langmuir 2004, 20, 5445−5453. (10) Angarska, J. K.; Tachev, K. D.; Denkov, N. D. Composition of Mixed Adsorption Layers and Micelles in Solutions of Sodium Dodecyl Sulfate and Dodecyl acid Diethanolamide. Colloids Surf., A 2004, 233, 193−201. (11) Christov, N. C.; Denkov, N. D.; Kralchevsky, P. A.; Ananthapadmanabhan, K. P.; Lips, A. Synergistic Sphere-to-Rod Micelle Transition in Mixed Solutions of Sodium Dodecyl Sulphate and Cocoamidopropyl Betaine. Langmuir 2000, 20, 565−571. (12) Prajapati, R. R.; Bhagwat, S. S. Effect of Foam Boosters on Krafft Temperature. J. Chem. Eng. Data 2012, 57, 869−874. (13) Feng, J.; Rodriguez, C.; Izawa, T.; Kunieda, H.; Sakai, T. Effect of Novel Alkanolamides on the Phase Behavior and Surface Properties of Aqueous Surfactant Solutions. J. Dispersion Sci. Technol. 2004, 25, 163−172. (14) Tsujii, K.; Okahashi, K.; Takeuchi, T. Addition-Compound Formation between Anionic and Zwitterionic Surfactants in Water. J. Phys. Chem. 1982, 86, 1437−1441. (15) Domsch, A.; Jenni, K. Biodegradability of Amphoteric Surfactants. In Handbook of Detergents Part B: Environmental Impacts;

5. CONCLUSIONS The interaction between SDS and the foam boosters was quantified by an interaction parameter (β). The value of this parameter was determined by applying Rubingh’s regular solution model to experimental data. It was observed that CAPB was more efficient in reducing the CMC when compared to other surface active foam boosters. The strength of interaction decreased in the order CAPB > CDEA > CMEA(EO)1 for both micellization and adsorption. CAPB is compatible and effective in both micellization and adsorption in comparison with the other foam boosters. It showed better synergistic interaction in micellization and in adsorption with SDS, whereas CDEA showed higher synergistic interaction with SDS in adsorption compared to CMEA(EO)1 which had weak interaction with SDS during micellization and adsorption. The βM−β40 values suggested the SDS−CDEA system had a higher affinity for adsorption than micellization compared to SDS− CAPB and SDS−CMEA(EO)1. 3649



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Zoller, U., Ed.; Surfactant Science Series 121; Marcel Dekker, Inc.: New York; Chapter 20, pp 551−571. (16) Clint, J. H. Surfactant Aggregation; Chapman and Hall: New York, 1992. (17) Clint, J. H. Micellization of Mixed Nonionic Surface Active Agents. J. Chem. Soc., Faraday Trans. 1 1975, 71, 1327−1334. (18) Rubingh, D. N.; Mittal, L. Solution Chemistry of Surfactants; Plenum Press: New York, 1979; Vol. 1. (19) Li, F.; Li, G. Z.; Chen, J. B. Synergism in Mixed ZwitterionicAnionic Surfactant Solutions and the Aggregation Number of the Mixed Micelles. Colloids. Surf., A 1998, 145, 167−174. (20) Sambhav, V.; Alex, G.; Hemangi, D.; Bahadur, P. Mixed Micelles of Some Anionic-Anionic, Cationic-Cationic, and Ionic-Nonionic Surfactants in Aqueous Media. J. Surfactants Deterg. 1999, 2, 213−221. (21) Ogino, K.; Abe, M. Mixed Surfactant Systems; ACS Symposium Series 68; American Chemical Society: Washington, DC, 1986. (22) Camp, M.; Durham, K. The Foaming of Sodium Laurate Solutions-Factors Influencing Foam Stability. J. Phys. Chem. 1955, 59, 993−997.

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Effect of Foam Boosters on the Micellization and Adsorption of Sodium

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