There are many method for oil decolorization, the most widely used in industrial production is the adsorption decolorization method. Oil adsorption decolorizing, is the method to use some materials which has strong selective function (adsorbent) to adsorpt pigments and other impurities from the oil.
Currently, there are mainly two kinds of adsorbent used in oil industry decolorizing:
1)Activated clay
Activated clay is a kind of high adsorbent which is processed from bentonite , and is widely used in the oil decolorization. Activated clay has a strong adsorption ability for pigment, especially the chlorophyll and other colloidal impurities, and has stronger adsorption ability in basic group and polarity radicals. After use clay for decolorizing, the oil will have a taste that like the clay,so it can be edible after deodorization.
2)Activated carbon
Activated carbon is made of tree branches, leather case and so on after coking, then through the activation treatment. With fine porous structure, the decoloring coefficient is very high, to remove the red pigment in oil is very effective. We can get the oil without peculiar smell after decolorizing. The activated carbon also can adsorpt some materials with low smoke point, but the filtering seed will be very slow after using the carbon,and it’s expensive and also has a higher oil absorption. So the activated carbon is generally not used alone,often used with activated clay with the rate of 1:10-20.
