Abstract
Adsorption isotherms in bleaching hazelnut oil were determined to investigate the applicability of the Langmuir and Freundlich equations and to elucidate the adsorption characteristics of oil on bentonite EY-09 (Bensan Co. Ltd., Edirne, Turkey). The degree of bleaching was monitored spectrophotometrically. Absorbance measurements were carried out to investigate the adsorption force of clay during bleaching of hazelnut oil with 0.3, 0.5, 0.7, and 0.9 wt% clay at 50, 60, 70, 80, and 90°C. Bentonite EY-09 was used as the bleaching clay (adsorbent). Plots of log(x/m) vs. log X e (for the Freundlich isotherm) and X e /(x/m) vs. X e (for the Langmuir isomtherm) were made (where x is the amount of pigment removed per unit mass of the adsorbent, m, and X e is the equilibrium concentration of the pigment). The Freundlich constants were found to increase with temperature for a given oil/bleaching agent ratio, showing the formation of more active sites on the adsorbent with a rise in temperature. Since the heat evolved during adsorption (0.32–1.03 kJ mol−1) was less than 20 kJ mol−1, the forces between the adsorbent and adsorbate appeared to be van der Waals forces. This type of adsorption is defined as physical or van der Waals adsorption. The results obtained show good agreement with the Freundlich isotherm, indicating that the adsorption of the pigment from the oil proceeds by monolayer formation on the surface of the adsorbent.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Boki, K., M. Kubo, T. Wada, and T. Tamura, Bleaching of Alkali-Refined Vegetable Oils with Clay Minerals, J. Am. Oil Chem. Soc. 69: 232–236 (1992).
Krishna, A.G.G., A Method for Bleaching Rice Bran Oil with Silica Gel, Ibid. 69: 1257–1259 (1992).
Norris, F.A., Bailey’s Industrial Oil and Fat Products, 3rd edn., edited by D. Swern, Interscience, New York, 1964, pp. 769–792.
Taylor, D.R., and C.B. Ungermann, The Adsorption of Fatty Acids from Vegetable Oils with Zeolites and Bleaching Clay/Zeolite Blends, J. Am. Oil Chem. Soc. 61: 1372–1375 (1984).
Habile, M., P.J. Barlow, and M. Hole, Adsorptive Bleaching of Soybean Oil with Non-montmorillonite Zambian Clays, Ibid. 69: 379–383 (1992).
Toro-Vazquez, J.F., E.O. Garcia, and L.L. Guerrero, Adsorption Isotherms of Squash (Cucurbita moschata) Seed Oil on Activated Carbon, Ibid. 68: 596–599 (1991).
Laidler, K.J., Chemical Kinetics, 3rd edn., Harper & Row, New York, 1987, pp. 215–238.
Langmuir, I., Adsorption Isotherms, in Physical Chemistry, 4th edn., edited by I.N. Levine, McGraw-Hill, New York, 1995, pp. 365–367.
Freundlich, H., Adsorption Isotherms, in Physical Chemistry, 6th edn., edited by P.W. Atkins, Oxford University Press, Oxford, 2000, pp. 861–863.
Boki, K., H. Mori, and N. Kawasaki, Bleaching Rapeseed and Soybean Oils with Synthetic Adsorbents and Attapulgites, J. Am. Oil Chem. Soc. 71: 595–601 (1994).
Achiefe, E.C., and J.A. Ibemesi, Applicability of the Freundlich and Langmuir Adsorption Isotherms in the Bleaching of Rubber and Melon Seed Oils, Ibid. 66: 247–252 (1989).
Mingyu, J., and A. Proctor, The Effect of Added Solvents on Soy Oil Lutein Adsorption by Silicic Acid, Ibid. 70: 575–578 (1993).
Palaniappan, S., and A. Proctor, Evaluation of Soy Oil Lutein Isotherms Obtained with Selected Adsorbents in Hexane Miscellas, Ibid. 68: 79–82 (1991).
Suzuki, M., Adsorption Engineering, Elsevier Science, Amsterdam, 1990, pp. 35–62.
Weber, W.J., Jr., Adsorption Technology. A Step-by-Step Approach to Process Evaluation and Application, Marcel Dekker, New York, 1985, pp. 1–35.
Chang, Y.Y., C.I. Lin, and H.K. Chen, Rice Hull Ash Structure and Bleaching Performance Produced by Ashing at Various Times and Temperatures, J. Am. Oil Chem. Soc. 78: 657–660 (2001).
Norris, F.A., Bailey’s Industrial Oil and Fat Products, 4th edn., edited by D. Swern, Wiley Interscience, New York, 1982, pp. 294–314.
Author information
Authors and Affiliations
About this article
Cite this article
Bayrak, Y. Adsorption isotherms in bleaching hazelnut oil. J Amer Oil Chem Soc 80, 1143–1146 (2003). https://doi.org/10.1007/s11746-003-0833-7
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/s11746-003-0833-7