Adsorption of Sodium Dodecyl Sulfate and Butanol onto Acidic and Basic Alumina

Adsorption of Sodium Dodecyl Sulfate and Butanol onto Acidic and Basic Alumina

JOURNAL OF COLLOID AND INTERFACE SCIENCE ARTICLE NO. 182, 348–355 (1996) 0473 Adsorption of Sodium Dodecyl Sulfate and Butanol onto Acidic and Basi...

132KB Sizes 0 Downloads 5 Views

Recommend Documents

Adsorption of sodium dodecyl sulfate and sodium dodecyl benzenesulfonate on poly(vinyl chloride) latexes
The adsorption of sodium dodecyl sulfate (SDS) and sodium dodecyl benzenesulfonate (SDBS) on poly(vinyl chloride) (PVC)

The effect of butanol on the micellar properties of sodium dodecyl sulfate in aqueous electrolyte solutions
The effect of butanol on the micellar properties of sodium dodecyl sulfate in aqueous solutions containing a range of co

Three—dimensional phase diagram of the brine-toluene-butanol-sodium dodecyl sulfate system
A type of representation based upon variance for the quaternary system brine-oil-surfactant and cosurfactant is proposed

Influence of the peroxodisulfate counterion on the dodecyl sulfate adsorption onto polystyrene latex particles
Results of an experimental study are reported on the influence of the nature of the peroxodisulfate counterion (NH4+, K+

Direct carbohydrate analysis of glycoproteins electroblotted onto polyvinylidene difluoride membrane from sodium dodecyl sulfate-polyacrylamide gel
A procedure for the carbohydrate analysis of glycoproteins electrotransferred to a polyvinylidene difluoride membrane is

Adsorption of dodecyl trimethylammonium and hexadecyl trimethylammonium onto kaolinite — Competitive adsorption and chain length effect
Adsorption of dodecyl trimethylammonium (DDTMA) and hexadecyl trimethylammonium (HDTMA) from single and mixed surfactant

Sodium dodecyl sulfate-protein polypeptide complexes in 8 M urea with special reference to sodium dodecyl sulfate-polyacrylamide gel electrophoresis
The effects of 8 M urea on the complexes formed between sodium dodecyl sulfate and protein polypeptide were found to be

Thermodynamics of Sodium Dodecyl Sulfate Partitioning into Lipid Membranes
The partition equilibria of sodium dodecyl sulfate (SDS) and lithium dodecyl sulfate between water and bilayer membranes

Estimation of micellization parameters of sodium dodecyl sulfate in water+1-butanol using the mixed electrolyte model for molar conductance
The mixed electrolyte model of Shanks and Franses has been applied to estimate the critical micelle concentration, aggre

The interaction of sodium dodecyl sulfate with gelatin
The interaction of sodium dodecyl sulfate with gelatin at pH 7 has been investigated by measuring the surface tension of

JOURNAL OF COLLOID AND INTERFACE SCIENCE ARTICLE NO.

182, 348–355 (1996)

0473

Adsorption of Sodium Dodecyl Sulfate and Butanol onto Acidic and Basic Alumina GEIR M. FØRLAND, 1 TAMIZUR RAHMAN, HARALD HØILAND,

AND

KNUT J. BØRVE

Department of Chemistry, University of Bergen, Allegt. 41, N-5007 Bergen, Norway Received June 19, 1995; accepted March 28, 1996

The adsorption of sodium dodecylsulfate (SDS) and the coadsorption of SDS and 1-butanol from aqueous electrolyte solutions and from microemulsions containing heptane onto acidic and basic aluminum oxide were measured. The aluminum oxides contain quasi-spherical highly porous particles with an amorphous structure. The measurements were carried out just above the Krafft temperature at 267C. It is shown that the adsorption capacity of SDS and butanol onto the acidic alumina is slightly higher than that onto the basic. The adsorption of SDS decreases while butanol adsorption increases upon increasing alcohol concentration. The alcohol to surfactant mol ratio on the oxide surface reaches 2.3 for the acidic oxide and 2.1 for the basic oxide in solutions containing 0.8 M butanol. The result indicates that to a certain degree, SDS becomes gradually replaced by butanol on the alumina surface. In order to describe the surfactant/alcohol exchange on the surface, a simple model is proposed and fitted to the obtained adsorption data. According to this model, the alcohol to surfactant area ratios in the adsorbed patches are 0.48 and 0.71 on the acidic and basic oxide respectively. Addition of heptane does not show any considerable alteration in the adsorption density of the surfactant and alcohol, which indicates that heptane does not solubilize to any appreciable extent in the adsorbed aggregates on the oxide surface. q 1996 Academic Press, Inc. Key Words: adsorption; surfactant; co-surfactant; hemimicelles; admicelles; micelles; microemulsion.

INTRODUCTION

Adsorption of ionic surfactants onto mineral oxide surfaces has been extensively studied due to its wide industrial applications in systems involving wettability phenomena. Most works have focused on the characterization of adsorption isotherms in order to discuss adsorption capacities and molecular organization on the solid surface. This is due to the fact that the shape of these isotherms depends on the relative contributions of hydrophobic bonding interaction and coulombic interaction among adsorbed surfactant ions and the solid surface ( 1, 2 ) . 1 To whom correspondence should be addressed. E-mail: [email protected] nkj.uib.no.

348

0021-9797/96 $18.00 Copyright q 1996 by Academic Press, Inc. All rights of reproduction in any form reserved.

AID

JCIS 4334

/

6g14$$$561

Aluminum oxides have been especially useful in such studies since their surface charge and electrical double layer properties are well characterized and controlled by the pH ( 3, 4 ) . In contrast to the large amount of literature on surfactant / cosurfactant association and micellar solubilization, considerably less work has been done on adsorption at solid / liquid interfaces of surfactant systems containing additives. However, some previous papers have investigated the mutual adsorption of anionic surfactants and nonionic cosurfactants onto solid oxide surfaces ( 5 – 10 ) . These works show that surfactant ions adsorb readily onto oppositely charged oxides and form a characteristic isotherm ( 11 ) . Moreover, adsorption of cosurfactants only takes place if the surfactant already is present on the solid surface, and a decrease in the surfactant adsorption level is observed with increasing cosurfactant adsorption. Thus, the results indicate that the cosurfactant adsorbs onto the preadsorbed surfactant colloids present on the oxide surface. In an aluminum oxide / water system, the OH groups on the solid surface are the most important sites for surface interactions. These groups can act as acids or bases depending on the pH of the solution. With decreasing pH, the net positive surface charge increases and with increasing pH, the net positive charge decreases and becomes negative. The adsorption process is highly dependent on the various parameters such as pH and electrolyte content. In the present work, adsorption of SDS onto basic and acidic aluminum oxide in absence and presence of additives has been studied. The adsorption was measured from micellar solutions in absence and presence of butanol and from oil in water ( o / w ) microemulsions. The microemulsions or swollen micelles were prepared by adding heptane to the aqueous micellar solutions containing SDS, butanol and sodium chloride. The resulting solutions consist of small oil droplets dispersed in the aqueous medium. The aim of this study was to obtain quantitative adsorption data in order to compare the mutual adsorption of surfactant and cosurfactant from micellar solutions and

08-06-96 01:17:21

coida

AP: Colloid

ADSORPTION OF SODIUM DODECYL SULFATE AND BUTANOL ONTO ALUMINA

microemulsions, and to observe whether the heptane molecules solubilize in the adsorbed aggregates. MATERIALS AND METHODS

Materials Sodium dodecylsulfate was supplied by Merck, ‘‘purified grade more than 99%.’’ 1-butanol (99% pure), heptane (99% pure), trichloromethane ( ú99%), and sodium chloride (A.R. grade) were also obtained from Merck. The radioactive 1-butanol ( 14C labelled) and scintillation liquid-emulsifier safe (containing both solvent and scintillator) were delivered by Du Pont. The adsorbents were obtained from Aldrich and are specified as aluminum oxide, activated, 155 m2 /g (i) weakly acidic and (ii) basic, Brockman I, standard grade, Ç150 mesh. Preparation and Analysis The sodium dodecylsulfate was dried at 507C while the oxide was dried at 1107C for at least 24 h. The adsorption measurements were performed from aqueous solutions with various SDS concentrations having sodium chloride concentration fixed at 0.3 and 0.57 M. Solutions containing SDS, 1-butanol, and NaCl were mixed with oxides and analyzed in order to study the adsorption of surfactant and alcohol onto alumina. First, a stock solution containing known concentration of SDS and NaCl was prepared. This stock solution was mixed with radioactive 1-butanol to attain a 0.87 M 1-butanol solution. This was diluted with the stock solution. This procedure causes a successive decrease in the concentration of butanol, while the concentration of both SDS and NaCl varied just slightly. Next, the solution containing 0.87 M butanol was mixed with various amounts of heptane to obtain single phase oil in water (o/w) microemulsions. These solutions were mixed with oxides, and the adsorption of SDS and butanol was measured. The adsorption experiments were performed according to the batch method (12) and all adsorption studies were carried out at 26 { 0.27C. The solid to liquid weight/volume (g/ml) ratio was 0.12. In a typical experiment, the oxide was mixed with surfactant solutions in a centrifuge glass tube and rotated in a thermostated water bath until equilibrium was attained. The tube was centrifuged and SDS and butanol concentrations were determined by two-phase titration (13) and liquid scintillation counting (14), respectively. The well described two-phase Epton titration method (13) was used with a methylene blue indicator. The adsorption density G (mol/m 2 ) of surfactant and butanol was calculated according to the equation G Å DCV/MsSo ,

AID

JCIS 4334

/

6g14$$$562

[1]

08-06-96 01:17:21

349

where DC (mol/l) is the difference in molarity of the surfactant or alcohol due to adsorption, V is the volume of the liquid, Ms is the weight of the oxide, and So is the specific area of the oxide surface. The specific surface areas of the aluminum oxides were measured by a multipoint Brunauer–Emmet–Teller method (BET method), using nitrogen as adsorbate. BET surface areas obtained show 147 and 145 m2 /g respectively for the acidic and basic alumina. This is slightly lower than the surface area of 155 m2 /g specified by the Aldrich company. The X-ray fluorescence spectroscopy measurements were done using a Philips PW1404 spectrometer with the PW1492 (Version 3.0B) software. The X-ray diffraction analysis were measured using a Philips PW1700 automated powder diffractometer system with CuKa radiation. Dynamic light scattering measurements were performed on the microemulsion in order to get information on the mutual diffusion coefficient, size, and polydispersity of the oil droplets. A Malvern particle size processor (PC 12) was used. The glassware was carefully cleaned and dried, and the distilled water was filtered in a microporefilter in order to minimize the amount of dust. In addition, a facility for dust rejection was used throughout the measurement. This facility is a standard software produced and delivered by Malvern. The scattered light was collected at an angle of 307 by the photomultiplier tube. The time dependent correlation function was obtained by the computer, and the data were fitted to a single exponential equation to obtain the average self diffusion coefficient (Dm ). The polydispersity factor is the normalized variance associated with the correlation function as described by Pusey (15). RESULTS

The activated alumina is a porous high-area form of aluminum oxide prepared from a hydrated form by dehydration and recrystallisation. Electron micrograph pictures show quasi-spherical polydisperse particles with an average diameter of approximately 100 mm. Elemental analysis by X-ray fluorescence spectroscopy shows that the alumina surface contains more than 99.9% aluminum oxide. The X-ray diffraction measurements indicate an amorphous surface structure. The time required for the attainment of adsorption equilibrium was approximately 48 h for both oxides. The adsorption was notably higher in the case of acidic alumina than that of its counterpart. This is caused by a high degree of surface protonation giving the anionic surfactant a more favorable electrostatic force of attraction for the acidic oxide. The experimentally determined adsorption isotherms of SDS with different electrolyte concentrations are shown in Fig. 1a and 1b for the acidic and basic aluminum oxide respectively. The adsorption capacity of both oxides increases with increased ionic strength over the whole range

coida

AP: Colloid

350

FØRLAND ET AL.

FIG. 1. The adsorption isotherms of SDS in 0.3 and 0.57 M NaCl on (a) acidic and (b) basic aluminum oxide.

of equilibrium concentrations investigated. This is due to a reduced lateral electrostatic repulsion among adsorbed surfactant ions upon increasing salt content, and this decreased repulsion causes the adsorbed molecules to obtain a closer packing. The equilibrium concentration of SDS at which adsorption saturation is reached is approximately equal for the different sodium chloride content. However, the surfactant adsorption onto acidic alumina reaches the plateau section at lower surfactant concentration than the corresponding adsorption onto basic oxide due to higher electrostatic interaction on the acidic mineral surface. The pH of the aqueous SDS suspension containing acidic oxide was 5.7. The corresponding value of the basic alumina was about 8.0. The reported point of zero charge (pzc) lies in the vicinity of 9 (16–18). Figures 2a and 2b show the coadsorption of SDS and butanol onto acidic and basic alumina against the equilibrium concentration of butanol. The concentration of SDS and sodium chloride was approximately 0.13 M and 0.57 M respectively throughout the measurements. This corresponds to an SDS concentration far above the adsorption saturation level, at the plateau of the isotherm. The measurements were done according to previously described procedure and no pH adjustments were made. The adsorption of butanol increases while SDS adsorption decreases upon increasing alcohol content. The alcohol adsorption shows a large initial slope that gradually decreases upon increasing butanol concentration. This is due to a high affinity of alcohol for the oxide when surfactant is present. The affinity was essentially higher towards the acidic oxide than that of its counterpart. In the suspension containing acidic oxide, the adsorption of SDS and butanol reaches a unity mole ratio when the equilibrium concentration of butanol is about 0.25 M. The

AID

JCIS 4334

/

6g14$$$562

08-06-96 01:17:21

corresponding value for the basic oxide is 0.45 M. The data indicates that SDS get gradually replaced by butanol on the alumina surface. This corresponds well to previously reported data on coadsorption of surfactant and alcohol onto alumina (7–9). In order to make a microemulsion, heptane was added to the aqueous SDS/butanol/NaCl solution. Figure 3 shows a partial pseudo-ternary phase diagram of the water/SDS/ NaCl/butanol/heptane mixtures. The dotted line represents the compositions of the single phase microemulsions used in the adsorption process. These solutions consist of oil in water (o/w) microemulsions where oil droplets are dispersed in the aqueous solution. In order to elucidate some characteristics like diffusion coefficients, size and polydispersity of the droplets, dynamic light scattering (DLS) measurements were done. The data is presented in Table 1. The reported error in the droplet size is based on repetitive measurements. The large droplet size is due to the high salt content giving a screening of the electrostatic repulsion among the surfactant headgroups surrounding the microemulsion droplets. The hydrodynamic diameters of the droplets show a slight increasing tendency upon increasing heptane content. However, the observed size increment of the droplets is small. The successively increasing polydispersity index upon addition of heptane may be due to an increased size distribution and flexibility in the droplet shape when an essential amount of heptane becomes solubilized into the hydrophobic core of the micelle aggregates. Figures 4a and 4b show the adsorption density of SDS and butanol onto acidic and basic alumina in presence of various amounts of heptane. The measurements were done in accordance to previously described procedure. SDS and butanol does not display any significant change in the ad-

coida

AP: Colloid

351

ADSORPTION OF SODIUM DODECYL SULFATE AND BUTANOL ONTO ALUMINA

FIG. 2. The saturation adsorption density ( Gi ,sat ) of SDS and the adsorption density ( Gi ) of butanol plotted against the equilibrium concentration of butanol on (a) acidic oxide and (b) basic oxide.

sorption density when heptane was added to the solution. The solid to liquid ratio was reduced from 0.12 to 0.08 in the case of acidic oxide because in the 0.12 ratio a phase separation occurred. The observed destabilisation and phase separation of the microemulsion upon addition of acidic ox-

ide are caused by the alteration in the composition of the components. Two phases were formed consisting of a water in oil (w/o) microemulsion plus excess water known as a Winsor II system (19, 20). The phase separation and invertation of the microemulsion can be understood in terms of the geometry of the surfactant at the oil–water interface. The high ionic strength in these solutions produces an effective screening of the electrostatic repulsion among the surfactant headgroups. This screening decreases the cross sectional area of each headgroup and increases the radius of curvature of the droplets. Once the effective cross sectional area of the hydrocarbon tail in the surfactant molecule becomes higher than the corresponding area of the head group, the micelles acquire a negative or reverse curvature corresponding to a TABLE 1 The Measured Diffusion Coefficients, Calculated Hydrodynamic Diameters, and Polydispersity Indices of the Dispersed Oil Droplets at Various Heptane Contents Heptane [%]

FIG. 3. A partial pseudo-ternary phase diagram of the water/SDS/ NaCl/butanol/heptane system at 267C. The diagram is plotted on weight fraction basis, and the numbers on the axis refers to butanol and heptane. The composition of the aqueous corner is 0.13 mol/liter SDS and 0.57 mol/liter NaCl.

AID

JCIS 4334

/

6g14$$$562

08-06-96 01:17:21

4 5 6 7

coida

Diff. coefficient [cm2/s] 1.8 2.0 1.6 1.4

1 1 1 1

1007 1007 1007 1007

AP: Colloid

Hydrodyn. diameter [nm]

Polydisp. index

{ { { {

0.11 0.14 0.25 0.43

20 18 23 26

2 2 2 3

352

FØRLAND ET AL.

FIG. 4. The saturation adsorption density ( Gi ,sat ) of SDS and the adsorption density ( Gi ) of butanol plotted against the weight percent of heptane on (a) acidic oxide and (b) basic oxide.

w/o microemulsion, and a phase separation occurs. In the pseudo-ternary diagram shown in Fig. 4, the Winsor II region is located on the left hand side of the single phase area. DISCUSSION

The shape of the isotherms shown in Fig. 1 indicates a strong ‘‘adsorbate adsorbent bond’’ system. These isothermshapes are typical for systems containing aggregates with strong lateral bonds among perpendicularly oriented hydrocarbon chains (21). This is in agreement with previously reported data on adsorption of anionic surfactants onto alumina (22). It has been shown that the increasing surfactant adsorption with decreasing pH near the pzc, is highly dependent on the surfactant concentration (16). For solutions containing SDS above the cmc, the surfactant adsorption increases dramatically upon a minor decrease in the solution pH. This demonstrates that the obtained adsorption density onto the basic aluminum oxide is sensitive for variations in the pH. On the other hand, the adsorption capacity for the acidic oxide is not so pH dependent, and it can be interpreted as being cmc limited not so far away from a completed surface coverage. It is well known that micelles do not adsorb significantly when ionic surfactants adsorb onto mineral oxide surfaces from simple aqueous micellar solutions (1). It seems reasonable to assume that the mixed solutions also obey these

AID

JCIS 4334

/

6g14$$$562

08-06-96 01:17:21

criteria, although the butanol molecules are located in the palisade layer of the micelles giving mixed aggregates in the solution. Therefore, surfactant/co-surfactant adsorption is primarily considered a function of the monomer concentration. According to the pseudo-phase separation model, the surfactant monomer concentration is equal to cmc in solutions where the total content of surfactant greatly exceeds the CMC (23). Hence the system is even further complicated by introduction of an equilibrium between the bulk phase, surfactant in monomeric form and in micellar aggregates. Thus, the alcohol becomes distributed among three different pseudo-phases. It is adsorbed at the solid surface, dissolved in the aqueous bulk phase and in the micellar aggregates. The adsorbed phase on the oxide and the bulk phase of surfactant and alcohol will be affected by changes in the CMC. It is known that addition of alcohol to aqueous ionic surfactant systems lowers the CMC, and that the more hydrophobic the alcohol, the more marked is the decrease in the CMC (6, 24). Here, the effect of butanol on the adsorption level of SDS was studied by choosing a surfactant content at the plateau of the isotherm. As the surfactant adsorption capacity at the plateau is CMC limited, the reduction in SDS adsorption density upon addition of alcohol may be in accordance with the fact that there are fewer monomers available for adsorption due to the decrease in the CMC. The result shows that the decreased SDS adsorption upon increasing butanol concentration is approximately equal for

coida

AP: Colloid

ADSORPTION OF SODIUM DODECYL SULFATE AND BUTANOL ONTO ALUMINA

the two oxides. A loss of about 42% and 44% of the adsorbed surfactant from the saturation level can be observed for the basic and acidic oxide respectively, when 0.5 M butanol is present. The loss of adsorbed surfactant reaches between 55% and 60% near the end of the butanol concentration range. Previously reported result shows that a decrease in SDS adsorption level follows the decrease in cmc upon addition of 1-butanol (6). Moreover, a requirement for significant alcohol adsorption is that surfactant must be present at the solid surface. This means that co-adsorption of alcohol will directly influence the specific adsorption density of the surfactant. Some authors have compared the molecular arrangement at the solid surface with that in liquid crystal lamellas on the basis of adsorption density data (7). However, one normally believes that the heterogeneity of most mineral oxide surfaces gives rise to patchwise adsorbed surfactant aggregates called solloids (25). The term hemimicelles or admicelles is used where either of the terms are dedicated to a particular structure of the aggregates (26, 27). The hemimicelles are defined as aggregates of ‘‘head on’’ adsorbed surfactant molecules, while the admicelles are defined as aggregates of both ‘‘head on’’ and ‘‘head out’’ adsorbed aggregates (27). For adsorption of ionic surfactants onto mineral oxide surfaces, local bilayers (admicelles) are thought to be formed near the saturation adsorption level (1, 28, 29). The molecular arrangement of the admicelle aggregates is not well defined. However, three prevalent models of adsorption have lately been discussed (30); the reverse orientation model (31), the bilayer model (29), and the surface micelle model (32). These are schematically presented in Fig. 5. Most data seem to favor the first two models where the surfactant molecules show a well organized adsorption with the head groups in the bottom layer oriented towards the mineral and the head groups in the second layer oriented towards the aqueous bulk solution (27, 33, 34). Due to the nonionic character of butanol, it is reasonable to assume that the molecular exchange (surfactant–alcohol exchange) on the alumina surface mainly occurs in the second layer. In this position, the adsorbed surfactant molecules take hold by association of the hydrocarbon chains gaining their stability through lateral hydrophobic chain–chain interactions. In the bottom layer, the surfactant ions exhibit both electrostatic interactions toward the oxide surface as well as lateral chain–chain interactions. The electrostatic interaction has a strong impact on the surfactant molecules adsorbed with their headgroups toward the oxide surface. Therefore, we assume that the molecular exchange does not occur in any appreciable extent in this position. Thus, the adsorption of alcohol molecules is thought to be occurred by exchanging position with the weakly adsorbed surfactant ions located in the second layer. The alcohol molecules may penetrate the hydrocarbon chains of the surfactant molecules in the bottom

AID

JCIS 4334

/

6g14$$$562

08-06-96 01:17:21

353

FIG. 5. A schematic presentation of three adsorption models.

layer, orienting their OH groups toward the aqueous bulk solution. In an organized surfactant adsorption consistent with any of the first two models shown in Fig. 5, the total surface area (Atot ) of the mineral can be expressed by the equation Atot Å As (n os 0 n sm ) / Ae ,

[2]

where As is the area occupied by each surfactant molecule, Ae is the surface area where no adsorption of alcohol or surfactant occurs, n os is the total number of adsorbed SDS molecules and n sm is the number of SDS molecules adsorbed in the bottom layer. If alcohol is present, the mineral area can be expressed as

coida

AP: Colloid

354

FØRLAND ET AL.

FIG. 6. The number of adsorbed surfactant molecules (ns ) plotted against the number of adsorbed alcohol molecules ( na ).

Atot Å As (ns 0 n sm ) / Aana / Ae ,

[3]

where ns and na are the number of surfactant and alcohol molecules adsorbed, and Aa is the area occupied by each alcohol molecule. By combining Eq. [2] and [3], one obtains ns Å n os 0

Aa na . As

[4] ACKNOWLEDGMENTS

A plot of the number of surfactant molecules, ns , against the number of alcohol molecules, na , should give a straight line where the intercept provides the maximum number of adsorbed surfactant molecules and the slope of the line provides the area ratio of the alcohol to that of the surfactant molecules. A plot of ns against na is shown in Fig. 6. The linear equation fits the experimental data well for both the acidic and basic alumina, indicating a highly correlated adsorption–desorption process. It also indicates that butanol does not create any new adsorption sites on the mineral surface. The adsorption density of surfactant was found by dividing the values for the intercept with Avogadros number and with the surface area available for adsorption. This gives 2.54 and 2.84 mmol each m2 for the basic and acidic alumina respectively. The values agree well with the obtained adsorption plateau values shown in Fig. 1. The area ratios of alcohol to surfactant were found to be 0.71 and 0.48 for the basic and acidic alumina respectively. This result shows that each alcohol molecule requires half the area available each surfactant molecule on the acidic oxide, while it uses approximately three-fourths of the area of each surfactant molecule

AID

JCIS 4334

/

6g14$$$563

on the basic oxide. This indicates a looser molecular packing structure in the admicelles on the basic oxide compared to the corresponding values on the acidic oxide. One may assume that the electrostatic attraction of surfactant ions to the aluminum oxide influences the adsorption capacity giving higher SDS adsorption density for the acidic oxide compared to the corresponding value for basic oxide. This high adsorption density of surfactant obviously favors the adsorption of alcohol, resulting in a higher alcohol to surfactant packing value in the case of the acidic oxide compared to the corresponding value obtained for the basic oxide. In conclusion, the adsorption of surfactant onto acidic as well as basic aluminum oxide decreases considerably when butanol is added to the solution. At the same time, the adsorption of butanol increases with concentration. The data indicates that butanol gradually replaces SDS on the alumina surface. The alcohol to surfactant mol ratio near the end of the added alcohol concentration reaches 2.3 and 2.1 on the acidic and basic oxide respectively. According to the observed adsorption behavior of SDS and alcohol on the solid surface, a simple model was proposed and fitted to the obtained adsorption data. The result shows that the alcohol to surfactant area ratios was 0.48 and 0.71 for the acidic and basic oxide respectively. The adsorption density of SDS and butanol seems unchanged upon addition of heptane to the solutions indicating that heptane does not solubilize in any appreciable extent into the adsorbed aggregates. Moreover, the light scattering data indicates that heptanol solubilizes into the micellar core, giving an slightly increased size and size distribution of the droplet particles.

08-06-96 01:17:21

The authors are grateful to Dr. Magne Tysseland for his assistance on the X-ray analysis and to Dr. Leif Brunchorst Garmann for his assistance on the liquid scintillation counting analysis.

REFERENCES 1. Scamehorn, J. F., Schechter, R. S., and Wade, W. H., J. Colloid Interface Sci. 85, 463 (1982). 2. Gu, T., Gao, Y., and Huang, Z., J. Surf. Sci. Technol. 5(2), 133 (1989). 3. Fuerstenau, D. W., and Wakamatsu, T., Discuss. Faraday Soc. 59–60, 157 (1975). 4. Madsen, L., and Blokhus, A. M., J. Colloid Interface Sci. 166, 259 (1994). 5. Lee, C., Yeskie, M. A., Harwell, J. H., and O’Rear, E. A., Langmuir 6, 1758 (1990). 6. Blokhus, A. M., Colloid Polym. Sci. 268, 679 (1990). 7. Blokhus, A. M., and Sjo¨blom, J., J. Colloid Interface Sci. 141, 395 (1991). 8. Sjo¨blom, J., Blokhus, A. M., and Høiland, H., J. Colloid Interface Sci. 136, 584 (1990). 9. Ruths, M., Sjo¨blom, J., and Blokhus, A. M., J. Colloid Interface Sci. 145, 108 (1991). 10. Clemens, W. D., Haegel, F. H., and Schwuger, M. J., Langmuir 10, 1366 (1994).

coida

AP: Colloid

ADSORPTION OF SODIUM DODECYL SULFATE AND BUTANOL ONTO ALUMINA 11. Somasundaran, P., and Fuerstenau, D. W., J. Phys. Chem. 70, 90 (1966). 12. Kipling, J. J., in ‘‘Adsorption from Solutions of Nonelectrolytes’’ (J. J. Kipling, Ed.), Academic Press, London/New York, 1965. 13. Cross, J. T., Analyst 90, 315 (1965). 14. Horrocks, D. L. in ‘‘Liquid Scintillation, Science and Technology’’ (A. A. Noujaim, C. Ediss, and L. I. Weibe, Eds.), pp. 1–16, Academic Press, New York/London, 1976. 15. Pusey, P. N., in ‘‘Photon Correlation and Light Beating Spectroscopy’’ (H. Z. Cummins and E. R. Pike, Eds.), pp. 387–428, Plenum, New York/London, 1974. 16. Dick, S. G., Fuerstenau, D. W., and Healy, T. W., J. Colloid Interface Sci. 37, 595 (1971). 17. Goddard, E. D., and Somasundaran, P., Croat. Chem. Acta 48, 451 (1976). 18. Tamamushi, B., and Tamaki, K., Trans. Faraday Soc. 55, 1007 (1959). 19. Robinson, B. H., Chem. Britain 26(4), 342 (1990). 20. Binks, B. P., Chem. Ind. (14), 537 (1993). 21. Cases, J. M., and Villieras, F. in ‘‘Innovations in Flotation Technology’’ (P. Mavros and K. A. Matis, Eds.), pp. 25–54, Kluwer Academic, Dordrecht, 1992.

AID

JCIS 4334

/

6g14$$$563

08-06-96 01:17:21

355

22. Scamehorn, J. F., Schechter, R. S., and Wade, W. H., J. Colloid Interface Sci. 85, 479 (1982). 23. Shinoda, K., in ‘‘Colloidal Surfactants’’ (K. Shinoda, B. Tamamushi, T. Nakagawa, and T. Isemura, Eds.), Chap. 1, Academic Press, New York, 1963. 24. Hayase, K., and Hayano, S., Bull. Chem. Soc. Jpn. 50, 83 (1977). 25. Somasundaran, P., and Kunjappu, J. T., Colloids Surf. 37, 245 (1989). 26. Wa¨ngnerud, P., Berling, D., and Olofson, G., J. Colloid Interface Sci. 169, 365 (1995). 27. Koopal, L. K., Lee, E. M., and Bo¨hmer, M. R., J. Colloid Interface Sci. 170, 85 (1995). 28. Harwell, J. H., Hoskins, J. C., Schechter, R. S., and Wade, W. H., Langmuir 1, 251 (1985). 29. Yeskie, M. A., and Harwell, J. H., J. Phys. Chem. 92, 2346 (1988). 30. So¨derman, O., and Stilbs, P., Prog. NMR Spectrosc. 26, 445 (1994). 31. Kunjappu, J. T., and Somasundaran, P., J. Phys. Chem. 93, 7744 (1989). 32. Gao, Y., Du, J., and Gu, T., J. Chem. Soc. Faraday Trans. 1 83, 2671 (1987). 33. Quist, P-O., and So¨derlind, E., J. Colloid Interface Sci. 172, 510 (1995). 34. Chandar, P., Somasundaran, P., and Turro, N. J., J. Colloid Interface Sci. 117, 31 (1987).

coida

AP: Colloid