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Decolorization of Vegetable Oils: A Study of the Mechanism of Adsorption of β-Carotene by an Acid-Activated Bentonite from Cyprus

Published online by Cambridge University Press:  01 January 2024

George E. Christidis  and
Sotiria Kosiari
George E. Christidis*
Affiliation:
Technical University of Crete, Department of Mineral Resources Engineering, 73100 Chania, Greece
Sotiria Kosiari
Affiliation:
Technical University of Crete, Department of Mineral Resources Engineering, 73100 Chania, Greece
*
*E-mail address of corresponding author: christid@mred.tuc.gr
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Abstract

The mechanism of decolorization of crude maize and sunflower oils was studied by means of adsorption of β-carotene by a low-grade bentonite, containing mixed-layered illite-smectite. Decolorization depends on temperature and the time required for equilibrium decreases with increasing temperature. The study of the kinetics of adsorption showed that decolorization of maize oil is a first-order process which occurs in two steps: a first fast step with higher activation energy (25.6 kJ mol−1), indicating the influence of a chemical interaction between the pigment and the clay surface, followed by a second slow step with low activation energy (12.3 kJ mol−1), characteristic of physical adsorption on the previously adsorbed molecules. Decolorization of sunflower oil is also a first-order process, described by a single mechanism with intermediate activation energy (19.0 kJ mol−1). Adsorption isotherms of decolorization of maize oil follow the Freundlich equation, indicating the existence of heterogeneous adsorption sites on the solid's surface. Heterogeneity is attributed both to different active centers on the smectite surface (Brönsted and Lewis centers) and to the different phases present in bentonite, such as illitic layers and clinoptilolite, which also have active centers on their surfaces.

Keywords

Acid-activated BentoniteActivation EnergyActive CentersAdsorption Kineticsβ-caroteneDecolorizationFreundlich IsothermReaction OrderVegetable Oils
Type
Research Article
Information
Clays and Clay Minerals , Volume 51 , Issue 3 , June 2003 , pp. 327 - 333
Copyright
Copyright © 2003, The Clay Minerals Society

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