How do fuller’s earth and activated carbon remove pigments from oils?

In the context of fat and oil processing, fuller’s earth and activated carbon are used as bleaching agents to remove pigments and other impurities from oils.1

These agents function primarily through the process of adsorption. When heated oils are treated with these materials, various impurities—specifically chlorophyll and carotenoid pigments—adhere to the surface of the bleaching agents. Once these pigments are bound to the agents, they are effectively removed from the oil through filtration.12

Fuller’s earth, which is composed mainly of hydrated aluminum silicates such as montmorillonite, is particularly effective due to its high adsorptive capacity for coloring bodies. While this process successfully decolorizes the oil, it is important to note that it can also remove natural antioxidants, which may increase the oil's susceptibility to rancidity.21