Adsorption of Vitamin E on Mesoporous Carbon Molecular Sieves

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Chem. Mater. 2005, 17, 829-833

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Adsorption of Vitamin E on Mesoporous Carbon Molecular Sieves Martin Hartmann,*,† A. Vinu,†,‡ and G. Chandrasekar† Department of Chemistry, Chemical Technology, TU Kaiserslautern, P.O. Box 3049, D-67653, Kaiserslautern, Germany, and International Center for Young Scientists, National Institute for Materials Science, 1-1, Namiki, Tsukuba, 305-0044, Japan ReceiVed August 27, 2004. ReVised Manuscript ReceiVed NoVember 30, 2004

The adsorption of vitamin E onto mesoporous carbons CMK-1 and CMK-3 from vitamin E solutions with different concentrations in nonpolar (n-heptane) and polar (n-butanol) solvent has been studied for the first time, and the results are compared to a conventional microporous carbon adsorbent, activated carbon. The amount of vitamin E adsorption on the different adsorbents depends on the solvent as well as the mesopore volume and the surface area of the adsorbent. It has been found that n-heptane is preferred to achieve a maximum amount of vitamin E adsorption. Among the carbon materials studied, CMK-3 shows the highest vitamin E adsorption due to the large specific mesopore volume of this adsorbent. CMK-3 was characterized after vitamin E adsorption to confirm the structure of the adsorbent and prove that the adsorption takes place in the channels of the mesoporous carbon adsorbent. XRD and nitrogen adsorption data recorded after vitamin E adsorption confirm the tight packing of the vitamin E molecules inside the mesopores of CMK-3.

Introduction Porous materials such as zeolites, zeotype materials, active carbons, silica gels, and metal oxides are of tremendous importance in many areas of research and development, mainly in adsorption, catalysis, energy storage, electrochemistry (e.g., battery electrodes), and biomedical engineering.1-8 Among these porous materials, activated carbons have been extensively used in various industrial adsorption and separation processes of bulky organic molecules such as vitamins, dyes, and humic substances.5-8 However, the performance of these materials in the adsorption of giant organic molecule is not optimal because of their disordered pore structure, low specific pore volume, and significant amount of micropores, which only allows the adsorption of relatively small molecules from the gas or liquid phase.1 Vitamin E (tocopherol) is a fat-soluble vitamin, which functions solely as a membrane-bound antioxidant that prevents cell membrane damage by inhibiting peroxidation of membrane phospholipids and disrupting free radical chain reactions induced by formation of lipid peroxides. Vitamin E also increases the bioavailability of vitamin A by inhibiting * To whom correspondence should be addressed. Phone: +49-631-205-3559. Fax: +49-631-205-4193. E-mail: [email protected]. † TU Kaiserslautern. ‡ National Institute for Materials Science.

(1) Bansal, C. R., Donnet, J.-B., Stoeckli, F., Eds. ActiVe Carbon; Marcel Dekker: New York, 1998. (2) Foley, H. C. Microporous Mater. 1995, 4, 407. (3) Inagaki, M. New Carbons; Elsevier: Amsterdam, 2000. (4) Yohimura, S., Chang, R. P. H., Eds. Supercarbon, Synthesis, Properties and Applications; Springer-Verlag: New York, 1998. (5) Akolekar, D. B.; Hind, A. R.; Bhargava, S. K. J. Colloid Interface Sci. 1998, 199, 92. (6) Tamai, H.; Kakii, T.; Hiroto, Y.; Kumamoto, T.; Yasuda, H. Chem. Mater. 1996, 8, 454. (7) Tamai, H.; Ikenchi, M.; Kojima, S.; Yasuda, H. AdV. Mater. 1997, 9, 55. (8) Tamai, H.; Yoshida, T.; Sasaki, M.; Yasuda, H. Carbon 1999, 37, 983.

its intestinal oxidation. As the only membrane-bound lipidsoluble antioxidant, vitamin E plays a key role in preventing cellular injury from oxidative stress associated with premature aging, cataracts, uncontrolled diabetes, cardiovascular disease, inflammation, and infection. Vitamin E occurs in food as tocopherols or tocotrienols. R-Tocopherol has the highest bioactivity and is thus used as a model system for vitamin E. Adsorption of vitamin E on solid surfaces has attracted significant attention due to its importance for the food industry and in the medicinal field. Recently, Kavalenko et al.9 reported the adsorption of vitamin E on carboncontaining enterosorbents to obtain drugs with slow release of the active ingredient. They also found that the adsorbed vitamin E molecules are oriented in such a way that their OH groups remain free and retain their biological activity. For the adsorption of large biomolecules such as vitamins and proteins, the carbon adsorbents should possess mesopores, allowing the adsorption of molecules and ions that are too large to enter micropores. In recent years, there has been significant interest in the development of mesoporous carbon materials with uniform and tailored pore structure. Mesoporous carbons with uni- and three-dimensional pore systems were prepared from mesoporous silica templates such as MCM-48, SBA-1, and SBA-15 using sucrose as the carbon source by Ryoo et al.10-13 These materials possess a well-ordered pore structure, high specific pore volume, high specific surface area, and tunable pore diameters in the (9) Kovalenko, G. A.; Kuznetsova, E. V. Pharm. Chem. J. 2000, 34, 327. (10) Ryoo, R.; Joo, S. H.; Jun, S. J. Phys. Chem. B 1999, 103, 7743. (11) Ryoo, R.; Joo, S. H.; Kruk, M.; Jaroniec, M. AdV. Mater. 2001, 13, 677. (12) Joo, S. H.; Choi, S. J.; Oh, I.; Kwak, J.; Liu, Z.; Terasaki, O.; Ryoo, R. Nature 2001, 412, 169. (13) Jun, S.; Joo, S. H.; Ryoo, R.; Kruk, M.; Jaroniec, M.; Liu, Z.; Ohsuna, T.; Terasaki, O. J. Am. Chem. Soc. 2000, 122, 10712.

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mesopore range. Until now, there have only been few studies on the adsorption of large biomolecules such as vitamins and proteins over mesoporous carbon molecular sieves. Recently, we have reported the influence of solution pH, pore volume, and pore diameter on the adsorption of cytochrome c over mesoporous carbon materials with different textural properties and found that the protein adsorption capacity is mainly dependent on the mesopore volume and structural order of the materials.14 Han et al.15 reported the adsorption of humic acids over mesoporous carbon materials which were prepared using silica sol particles. These materials also showed higher and faster adsorption of humic acids than commercial activated carbons such as F400 and Norit SA. However, to the best of our knowledge, there has been no report on the adsorption of vitamin over mesoporous carbon molecular sieves. In the present contribution, we report the adsorption of vitamin E over mesoporous carbon molecular sieves with different textural properties in comparison to activated carbon. It has been found that the amount of adsorption mainly depends on the specific pore volume of the mesoporous carbon adsorbent. Moreover, it has been observed that the solvent used plays an important role for the amount of vitamin E adsorption and that a nonpolar solvent is preferred for a high loading of vitamin E. Among the carbon materials studied, CMK-3 shows a higher amount of vitamin E adsorbed as compared to activated carbon and the other mesoporous carbon CMK-1. Experimental Section Preparation of CMK-3 and CMK-1. The mesoporous carbon CMK-3 was prepared by using SBA-15 as the template and sucrose as the carbon source. In a typical synthesis of mesoporous carbon, 1 g of template (mesoporous silica material) was added to a solution obtained by dissolving 1.25 g of sucrose and 0.14 g of H2SO4 in 5 g of water, and keeping the mixture in an oven for 6 h at 100 °C. Subsequently, the oven temperature was raised to 160 °C for another 6 h. To obtain fully polymerized and carbonized sucrose inside the pores of the silica template, 0.8 g of sucrose, 0.09 g of H2SO4, and 5 g of water were again added to the pretreated sample, and the mixture was again subjected to the thermal treatment described above. The template-polymer composites were then pyrolyzed in a nitrogen flow at 900 °C and kept under these conditions for 6 h to carbonize the polymer. The mesoporous carbon was recovered after dissolution of the silica framework in 5 wt % hydrofluoric acid, by filtration, washed several times with ethanol, and dried at 120 °C. CMK-1 was synthesized by using MCM-48 as template and sucrose as carbon source by a procedure similar to that used for the synthesis of CMK-3.11,12 Activated carbon (ABET ) 1620 m2/g) was supplied by Alfa Aesar. Characterization. The powder X-ray diffraction patterns of mesoporous carbon materials were collected on a Siemens D5005 or a Rigaku diffractometer using Cu KR (λ ) 0.154 nm) radiation. The diffractograms were recorded in the 2θ range of 0.8-10° with a 2θ step size of 0.01° and a step time of 10 s. High-resolution thermogravimetric analysis (SETARAM setsys 16MS) was carried out in a nitrogen atmosphere in the temperature range from 20 to (14) Vinu, A.; Streb, C.; Murugesan, V.; Hartmann, M. J. Phys. Chem. B 2003, 107, 8297. (15) Han, S.; Kim, S.; Lim, H.; Choi, W.; Park, H.; Yoon, J.; Hyeon, T. Microporous Mesoporous Mater. 2003, 58, 131.

Hartmann et al.

Figure 1. XRD powder patterns of CMK-3 and CMK-1 and their corresponding silica templates SBA-15 and MCM-48.

1300 °C with a heating rate of 5 K/min to determine the ash content of the samples. Nitrogen adsorption and desorption isotherms were measured at 77 K on a Quantachrome Autosorb 1 sorption analyzer. All samples were outgassed for 3 h at 250 °C under vacuum (p < 10-5 hPa) in the degas port of the adsorption analyzer. The specific surface area was calculated using the BET model. The pore size distributions were obtained from the adsorption and desorption branch of the nitrogen isotherms by Non Local Density Functional Theory (NLDFT). Vitamin E (r-Tocopherol) Adsorption. A series of standard vitamin E solutions with concentrations ranging from 0.25 to 60 g/L was prepared by dissolving different amounts of vitamin E in different solvents (n-heptane and n-butanol). In each adsorption experiment, 20 mg of the different mesoporous adsorbents was suspended in 4 g of the respective vitamin E solution. The resulting mixture was continuously shaken in a shaking bath at a speed of 160 shakes/min at 293 K until equilibrium was reached (typically 24 h). The amount of vitamin E adsorbed was calculated by subtracting the amount found in the supernatant liquid after adsorption from the amount of vitamin E present before addition of the adsorbent by UV absorption at 285.0 nm. Calibration experiments were done separately before each set of measurements with vitamin E solution of different concentrations in different organic solvents. Centrifugation prior to the analysis was used to avoid potential interference from suspended scattering particles in the UV-vis analysis.

Results and Discussion Characterization of the Adsorbents. Figure 1 shows the powder X-ray diffraction patterns of CMK-3, CMK-1, and their corresponding silica templates. CMK-3 possesses a hexagonally ordered mesostructure as evident from the presence of at least three XRD lines that can be indexed to (100), (110), and (200) reflections of the two-dimensional hexagonal space group p6mm. Consequently, the synthesized material is a true replica of the parent material SBA-15.16 CMK-1 exhibits three reflections in the region 2θ ) 2-3.5°, which are indexed to the (110), (211), and (220) reflections of the cubic space group I4132. Higher order reflections are observed in the region 2θ ) 3.5-6.5°, which are a superposition of various reflections that are indexed according to the I4132 space group. It is interesting to note that the XRD pattern of the material before the silica template removal is similar to that of MCM-48, which indicates an analogous structure. However, after the removal of the silica template, CMK-1 has an additional relatively narrow (110) (16) Hartmann, M.; Vinu, A. Langmuir 2002, 18, 8010.

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Figure 2. Nitrogen adsorption isotherms at 77 K on different carbon adsorbents: (b) CMK-3, (9) CMK-1, and (2) activated carbon.

Figure 3. Adsorption isotherm of vitamin E onto different carbon adsorbents from n-heptane as solvent at 293 K.

Table 1. Textural Properties of the CMK-1, CMK-3, and Activated Carbon Employed in This Study

bents and explained by multilayer (polynuclear) adsorption.9 An alternative explanation is follows: when the vitamin E concentration on the surface is low, the vitamin E molecules may be deposited randomly on the surface. However, when the vitamin E surface concentration is high, the vitamin E molecules are rearranged in such a way that a close packing occurs and the amount adsorbed increases strongly. Moreover, the high concentration of vitamin E may also favor surface crystallization, allowing a dense packing of vitamin E in the mesopores. It is evident from Figure 3 that each isotherm exhibits a pore-filling step that is in line with the different pore diameter of the adsorbents. CMK-3 shows a pronounced pore-filling step at higher final solution concentrations. It is also important to note that CMK-3 exhibited a high amount of vitamin E adsorption (5.94 mmol/g), which is higher as compared to CMK-1 and activated carbon, where the amount of vitamin E adsorbed corresponds to 5.01 and 4.10 mmol/ g, respectively. It has been reported that the BET surface area of the adsorbent is a crucial factor which determines the adsorption capacities of carbon adsorbents.17 In the range of final solution concentrations of vitamin E shown in Figure 3, the adsorption capacity of the carbon adsorbents decreases in the following order, CMK-3 > CMK-1 > activated carbon, although activated carbon has a higher specific surface area as compared to CMK-1. A reasonable explanation is that part of the micropores in active carbon contributing to the high surface area is not accessible to vitamin E. However, up to an initial solution concentration of vitamin E of ca. 2 g/L, the three adsorbents show an almost similar amount of vitamin E adsorption, which could be attributed to a monolayer on the accessible surface of each adsorbent. When the initial solution concentration of vitamin E is raised above 2 g/L, the adsorption capacity depends on the accessible pore volume of the adsorbent. Therefore, the textural properties of the porous adsorbents other than BET surface area such as pore volume and pore diameter also play an important role in determining the vitamin E adsorption capacity of mesoporous carbon adsorbents. It should also be noted that, although the difference in the pore volume of CMK-1 and CMK-3 is very small, there is a large difference in their amount of vitamin E adsorption. We surmised that this could be due to the difference in the

catalyst CMK-1 CMK-3 activated carbon

d spacing (nm)

ABET (m2/g)

Vp (cm3/g)

dp,NLDFT (nm)

5.14d210 8.72

1675 1260 1629

1.05 1.1 0.70

2.3 3.3

diffraction line in its diffraction pattern, confirming that MCM-48 is transformed into another structure with somewhat lower symmetry (i.e., different space group symmetry). This indicates that the topology has changed and CMK-1 is not a true replica of MCM-48.10 The TGA measurements revealed that the ash content of the mesoporous carbon samples after the silica dissolution is below 1 wt %. Figure 2 shows the nitrogen adsorption isotherms of CMK-3 and CMK-1 in comparison to the isotherm of activated carbon. The isotherm of CMK-3 is of type IV according to the IUPAC classification and exhibits a H1 hysteresis loop, whereas CMK-1 exhibits a type IV isotherm without hysteresis. As is evident from Figure 2, the isotherms of CMK-3 and CMK-1 featured a narrow capillary condensation step, indicating uniformly sized mesopores. The adsorption isotherm of activated carbon is a type I isotherm, which is characteristic for a microporous adsorbent. The textural properties of the different micro- and mesoporous carbon adsorbents are collected in Table 1. The specific surface areas of CMK-1 and activated carbon are 1675 and 1629 m2/g, respectively, which are higher than the specific surface area of CMK-3 (1260 m2/g). However, the specific pore volume of activated carbon is 0.7 cm3/g, which is lower as compared to the specific pore volume of CMK-1 (1.05 cm3/g) and CMK-3 (1.1 cm3/g). Figure 3 shows the equilibrium adsorption isotherms of vitamin E onto CMK-1, CMK-3, and activated carbon from the nonpolar solvent n-heptane. Each isotherm is characterized by a sharp initial rise, suggesting a high affinity between the vitamin E molecule and the adsorbent surface. All adsorbents studied exhibit isotherms with three well-defined stages. The first stage is indicative of monolayer adsorption of vitamin E at lower final solution concentration, and the second stage at an intermediate final concentration corresponds to a layer by layer adsorption in the mesopores. The plateau at the end of the each isotherm is associated with the complete filling of the mesopores by vitamin E molecules. Such a stepwise isotherm was also reported for the adsorption of vitamin E on carbon-containing enteroadsor-

(17) Noll, K. E.; Gournaris, V.; Hou, W. S. Adsorption technology for air and water pollution control; Lewis Publishers: Chelsea, MI, 1992.

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Figure 4. Adsorption isotherm of vitamin E onto different carbon adsorbents from n-butanol as solvent at 293 K.

Hartmann et al.

Figure 5. XRD powder patterns of CMK-3 before and after vitamin E adsorption at different initial solution concentrations (solvent: n-heptane).

pore structure and the smaller pore diameter of CMK-1 as compared to CMK-3. It has been recently reported that the surface of the pores with smaller pore diameter cannot be utilized in adsorption and the fractional coverage of the small pore surface may depend on the length of the diffusion path.18 In the adsorbent with smaller pores, CMK-1, pore blocking may occur due to aggregation of two or more vitamin E molecules.19 Consequently, the long diffusion path in the small mesopores will result in a greater probability for pore blocking to occur, and, thus, a smaller loading is obtained in CMK-1. However, in the case of CMK-3, the large pore diameter facilitates the diffusion of the vitamin E molecules from the mesopore entrance to the interior part of the carbon, and pore blocking might not occur. Hence, it is tentatively assumed that the higher vitamin E adsorption capacity of CMK-3 carbon is due to the larger pore diameter CMK-3, which allows full access of the mesopores by the vitamin E molecules. To study the effect of solvent polarity on the amount of vitamin E adsorption, adsorption measurements were carried using the polar solvent n-butanol (Figure 4). As compared to adsorption from n-heptane as the solvent, CMK-3 and activated carbon exhibited significantly lower vitamin E adsorption when n-butanol is used as the solvent. Moreover, the difference in vitamin E adsorption capacities between CMK-3 and activated carbon is lower as compared to the adsorption from n-heptane. The lower amount of vitamin E adsorption of CMK-3 and activated carbon from n-butanol can be explained by a stronger interaction between vitamin E and the solvent n-butanol. In the presence of n-butanol, hydrogen-bond formation between the OH groups of nbutanol and the active hydroxyl and ether groups of vitamin E will occur. This may result in a strong vitamin E and n-butanol interaction and thus reduce interaction between the carbon surface and the vitamin E molecule. Consequently, we tentatively assume that the lower vitamin E adsorption capacities of carbon adsorbents from n-butanol result from the increased formation of n-butanol solvent clusters on hydroxyl and ether groups of vitamin E molecule, the reduced access to the carbon surface, or the reduced interaction energy between vitamin E and the adsorbent surface and/or blocked pores. On the other hand, when we used n-heptane as a solvent, the interaction between the hydrophobic tail group

of vitamin E and the hydrophobic carbon surface was not affected by the nonpolar solvent. Hence, the vitamin E adsorption capacity from n-heptane is higher as compared to the polar solvent n-butanol. Thus, it can be concluded that a nonpolar solvent such as n-heptane is a good choice for a high loading of carbon adsorbents with vitamin E. However, when medical applications of carbons loaded with vitamin E are envisaged, only water and ethanol are tolerable as solvents. Further studies regarding this aspect are currently underway. Characterization of the Adsorbent after Vitamin E Adsorption. To know whether the vitamin E molecules are adsorbed inside the mesopores of CMK-3, the adsorbent was also characterized by XRD and nitrogen adsorption after vitamin E adsorption. Figure 5 shows the powder XRD patterns of CMK-3 before and after the vitamin E adsorption experiments at three different initial vitamin E concentrations, 1, 4, and 40 g/L, in n-heptane as the solvent. It can be seen from Figure 5 that all CMK-3 samples display a strong (100) reflection at low angle and two very small peaks at higher angles, which are characteristic for CMK-3 mesoporous carbons. However, with increasing initial concentration of vitamin E in n-heptane, the intensity of all three low angle peaks decreases as compared to the CMK-3 carbon before vitamin E adsorption. This is probably not due to lower structural order but to the larger contrast in density between the carbon walls and the empty pores relative to that between the carbon walls and the pores filled with vitamin E molecules.20 Moreover, the reduction in the intensity of the higher angle peaks was much higher when a higher vitamin E loading was achieved. The reduction in the intensity of the XRD peaks of CMK-3 with increasing amount of vitamin E adsorption supports the fact that vitamin E molecules are adsorbed inside the mesopores of the CMK-3 without affecting its structure. Figure 6 shows the nitrogen adsorption isotherms of CMK-3 before and after vitamin E adsorption from nheptane. The amount of nitrogen adsorbed is decreasing with increasing vitamin E loading. Table 2 summarizes the textural properties of the carbon adsorbents before and after vitamin E adsorption with different initial solution concentrations. Moreover, the specific surface area and the pore volume are concomitantly reduced. The specific pore volume of CMK-3

(18) Teng, H.; Hsieh, C. T. Ind. Eng. Chem. Res. 1998, 37, 3618. (19) Mckay, G.; Bino, M. J.; Altamemi, A. R. Water Res. 1985, 19, 491.

(20) Marler, B.; Oberhagemann, U.; Vortmann, S.; Gies, H. Microporous Mesoporous Mater. 1996, 6, 375.

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Figure 6. Nitrogen adsorption isotherms of CMK-3 before and after vitamin E adsorption at different initial solution concentrations in n-heptane: (open symbols, desorption; closed symbols, adsorption): (b) CMK-3, (9) CMK-3 (1 g/L), (2) CMK-3 (4 g/L), and ([) CMK-3 (40 g/L).

Figure 7. Comparison of the nitrogen adsorption isotherms of CMK-3 after vitamin E adsorption at different initial solution concentrations in n-heptane and n-butanol: (b) CMK-3 (4 g/L-n-butanol), (9) CMK-3 (40 g/L-nbutanol), (2) CMK-3 (4 g/L-n-heptane), and ([) CMK-3 (40 g/L-n-heptane).

Table 2. Textural Properties of CMK-3 Materials after Vitamin E Adsorption from Different Solvents at Various Initial Solution Concentrations

tonic decrease of specific surface area and pore volume with increased amount of vitamin E adsorption confirms the tight packing of the vitamin E molecule inside the mesopores of CMK-3 (Table 2).

solvent n-heptane n-butanol

initial concentration (g/L)

ABET (m2/g)

Vp (cm3/g)

1 4 40 1 4 40

733 501 178 786 647 298

0.78 0.53 0.19 0.81 0.68 0.30

decreases from 1.1 to 0.19 cm3/g after vitamin E adsorption, which is a 82.8% reduction in the total specific pore volume, whereas the specific surface area is reduced from 1260 to 178 m2/g, which is a 85.87% reduction in the total specific surface area. In addition, it is interesting to note that there is almost no capillary condensation step in the nitrogen adsorption isotherm of CMK-3 after vitamin E adsorption from a high concentrated solution (40 g/L). This is attributed to the tight packing of vitamin E inside the mesopores of CMK-3. A similar reduction in the specific pore volume and specific surface area was also observed for the other adsorbents employed in this study. Moreover, information concerning the textural parameters of CMK-3 after adsorption of different concentrations of vitamin E from n-butanol has been obtained. Figure 7 compares the nitrogen adsorption isotherms of CMK-3 after vitamin E adsorption from both n-heptane and n-butanol solutions with different concentrations. It is quite interesting to note that the amount of nitrogen adsorbed in CMK-3 loaded with vitamin E from n-butanol is always higher as compared to n-heptane regardless of the initial concentration of vitamin E (1, 4, and 40 g/L). The specific pore volume of CMK-3 after vitamin E adsorption from n-butanol (initial concentration of 40 g/L) decreases from 1.1 to 0.31 cm3/g, which is only a 71.8% reduction of the total specific pore volume, whereas the specific surface area is reduced from 1260 to 300 m2/g (76.2% reduction of the total specific surface area). The observed reduction in pore volume is in line with the amount of vitamin E adsorbed, which is lower when n-butanol is used as a solvent. Moreover, the mono-

Conclusions Adsorption of vitamin E over mesoporous carbon materials such as CMK-1 and CMK-3 has been studied from vitamin E solutions with various concentrations in different solvents such as n-heptane and n-butanol, and the results are compared to a conventional microporous carbon adsorbent, activated carbon. It has been observed that the vitamin E adsorption capacities of the adsorbents depend on the solvent used as well as the mesopore volume and the pore diameter of the adsorbent. It has also been found that a nonpolar solvent such as n-heptane is more suitable as compared to the polar solvent n-butanol to achieve high loadings of vitamin E. The lower vitamin E adsorption of carbon adsorbents from n-butanol presumably resulted from the increased formation of n-butanol solvent clusters interacting with hydroxyl and ether groups of the vitamin E molecule. The influence of the specific pore volume on the adsorption of vitamin E has also been studied by using adsorbents with different textural properties. It has been observed that the amount adsorbed is mainly a function of the specific mesopore volume rather than the specific surface area. Among the carbon materials studied, CMK-3 adsorbed a large amount of vitamin E (5.94 mmol/g), which is higher as compared to CMK-1 and activated carbon, where the vitamin E adsorption amounts to 5.01 and 4.10 mmol/g, respectively. N2 adsorption and XRD data after vitamin E adsorption reveal that the vitamin E molecules are tightly packed inside the mesopores of CMK-3 and CMK-1. Acknowledgment. Financial support of this work by the Fonds der Chemischen Industrie is gratefully acknowledged. A.V. is grateful to Prof. Y. Bando for the award of an ICYS Research Fellowship, National Institute for Materials Science, Japan. CM048564F