The available data have shown that acid-leached clays had sites for adsorption of impurities in oils. Data obtained on residual impurities in cotton and sunflower-seed oils bleached with the same clay materials produced linear Langmuir and Freundlich isotherms. The increase in constant, k with increase in both temperature of thermal activation and concentration of acid used to leach the clay, suggests that bleaching efficiency increased. The value of n decreased with increase in temperature of activation and concentration of acid used to leach the clay suggesting that bleaching capacity increased. The mineral compositions of the clays influenced their surface, structural and bleaching properties.
Boki, K.M. and Kawasaki, N. (1994) Bleaching of Rape Seed and Soybean Oils with Synthetic Adsorbents and Attapulgites. Journal of the American Oil Chemists’ Society, 71, 595-601. http://dx.doi.org/10.1007/BF02540585
Achife, J. and Ibemesi, J. (1989) Applicability of Freundlich and Langmuir Adsorption Isotherms in Bleaching of Rubber and Melon Seed Oils. Journal of the American Oil Chemists’ Society, 66, 247-252. http://dx.doi.org/10.1007/BF02546069
De Greyt, W.F., Kellens, M.J. and Huyghebaert, A.D. (1999) Effect of Physical Refining on Selected Minor Components in Vegetable Oils. Lipid, 101, 428-432. http://dx.doi.org/10.1002/(SICI)1521-4133(199911)101:11<428::AID-LIPI428>3.0.CO;2-T
Rossi, M., Gianazza, M., Alamprese, C. and Stanga, F. (2001) The Effect of Bleaching and Physical Refining on Color and Minor Components of Palm Oil. Journal of the American Oil Chemists’ Society, 78, 1051-1055. http://dx.doi.org/10.1007/s11746-001-0387-8
Ng, M.H., Choo, Y.M., Ma, A.N., Chuah, C.H. and Mohd. Ali, H. (2004) Separation of Vitamin E (Tocopherol, Tocotrienol and Tocomonoenol) in Palm Oil. Lipids, 39, 1031-1035. http://dx.doi.org/10.1007/s11745-004-1327-y
Mbah, B.J.M., Kamga, J.F., Nguetnkam, J. and Fanni, J. (2005) Adsorption of Pigments and Free Fatty Acids from Shea Butter on Activated Cameroonian Clays. European Journal of Lipid Science and Technology, 107, 387-394. http://dx.doi.org/10.1002/ejlt.200501149
Temuujin, J., Senna, M., Jadambaa, T., Burmaa, D., Erdenechimeg, S. and MacKenzie, K.J.D. (2006) Characterization and Bleaching Properties of Acid-Leached Montmorillonite. Journal of Chemical Technology & Biotechnology, 81, 688-693. http://dx.doi.org/10.1002/jctb.1469
Christidis, G.E. and Kosiari, S. (2003) Decolorization of Vegetable Oils: A Study of the Mechanism of Adsorption of β-Carotene by an Acid-Activated Bentonite from Cyprus. Clays and Clay Minerals, 51, 327-333. http://dx.doi.org/10.1346/CCMN.2003.0510309
Olsen, R.S. and Watanabe, F.S. (1957) A Method to Determine a Phosphorous Adsorption Maximum of Soils as Measured by Langmuir Isotherms. Soil Science Society of America Journal, 21, 144-149. http://dx.doi.org/10.2136/sssaj1957.03615995002100020004x
Kothawala, D.N., Moore, T.R. and Hendershot, W.H. (2008) Adsorption of Dissolved Organic Carbon to Mineral Soils: A Comparison of Four Isotherm Approaches. Geoderma, 148, 43-50. http://dx.doi.org/10.1016/j.geoderma.2008.09.004
Vandenbruwane, J., De Neve, S., Hofman, G., Sleutel, S. and Hofman, G. (2007) Isotherm Models for Desired Organic Carbon (DOCS) and Nitrogen Sorption to Mineral Soil. Geoderma, 139, 144-153. http://dx.doi.org/10.1016/j.geoderma.2007.01.012
Madejova, J., Andrejkovicová, S., Bujjdak, J., Ceklovsky, A., Hrachova, J., Valuchova, J. and Komadel, P. (2007) Characterization of Products Obtained by Acid Leaching of Fe-Bentonite. Clay Minerals, 42, 527-540.
Proctor, A. and Toro-Vazquez, J.F. (1998) The Freundlich Isotherms in Studying Adsorption in Oil Processing. Journal of the American Oil Chemists’ Society, 73, 1627-1633. http://dx.doi.org/10.1007/BF02517963
Ujeneza, E., Njenga, H.N., Mbui, N.D. and Kariuki, D.N. (2014) Optimization of Acid Activation Conditions for Athi River Bentonite Clay and Application of the Treated Clay in Palm Oil Bleaching. IOSR Journal of Applied Chemistry (IOSR-JAC), 7, 29-38. www.iosrjournals.org