The Mechanism of Chlorophyll Adsorption on Acid-Activated Clays

✍ Scribed by Robert Mokaya; William Jones; Mary E. Davies; Mavis E. Whittle

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 375 KB
• Volume: 111
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1994.1212

✦ Synopsis

Acid-activated montmorillonite clays are widely used to remove chlorophyll from edible oils. The exact properties of the clay responsible for the adsorption are still little understood as is the manner in which the chlorophyll is adsorbed. We report here various techniques applied to probe the nature of the interaction between the adsorbed chlorophyll molecule and the clay surface by following the adsorption properties of montmorillonite clays acid activated to varying degrees. Ion exchange of these acid-activated materials enables further control of their acidity; the influence of the exchangeable cation on the adsorption process is shown to decrease with increasing levels of acid activation, suggesting a possible existence of acid sites not associated with the cation. The nature of the acidity of the adsorbent (clay) is shown to change following chlorophyll adsorption; the chlorophyll molecule is believed to adsorb as a protonated species. We discuss the effect upon the chlorophyll adsorption process of the level of acid activation, the cation exchange capacity, and residual negative charge of the clay. 1994 Acadertic Press, Inc.