Bleaching is one of the most critical stages in the refining of edible oils such as sunflower, soybean, canola, corn, olive, and palm. Bleaching earth adsorbs colour pigments (e.g., carotenoids, chlorophyll), soap residues, trace metals, and oxidation products in crude oils. This improves the colour and oxidative stability of the oil, resulting in clearer appearance, lighter colour, and longer shelf life.
Bleaching clays are also used in the purification of certain animal-derived fats (tallow, fish oil, milk fat found in butter, etc.). Activated clay can be applied to remove undesirable odors and colors in the pharmaceutical purification of omega-3-rich oils like fish oil or making them suitable for food production.
Biodiesel is generally derived from vegetable oils or waste cooking oils. Bleaching earth can be used to purify crude biodiesel or raw oil feedstocks, enhancing the color and bringing it to fuel standard compliance.
Bleaching earth is utilized for decoloring and purifying petroleum-derived mineral oils, white oils, vaseline, paraffin, diesel fuel, and waxes.
Waste oils such as used motor oil are purified with bleaching earth when being recycled in recovery plants. In the re-refining process, color, residues, and odor of the distilled oil are removed with clay application to produce base oil.
Active bleaching clays act not only as adsorbents but also function as catalysts thanks to their acidic properties. They serve as catalyst supports in certain chemical reactions (e.g. alkylation, isomerization).
Special mildly activated clays can be used to purify essential oils used as perfumes, cosmetics, or food flavorings (e.g. citrus oils) from undesirable resinous substances or coloring impurities.
The high adsorption capacity of bleaching earth is also utilized in treating certain industrial wastewaters. It serves as a filter material for color removal from dye-containing textile wastewater and retaining heavy metals or oil/grease residues.