The use of bentonite to remove dark colour in repeatingly used palm oil.

Acid-activated bentonite was used as a bleaching agent to remove the dark color in repeatingly used palm oil. Two bentonite samples with different colors were used. It was found that the paler one gave better bleaching results. The optimum condition needed 5 h to reflux bentonite with sulfuric acid; pH of the bentonite suspension was 3, bleaching temperature was 80-85 degrees C and bleaching time was 30 min. The experiments also showed that bentonite could adsorb impurities and toxic compounds such as benzo(a)pyrene in palm oil. Chemical and physical properties of the bentonite samples were analyzed by X-ray fluorescence spectrometer (XRF), X-ray diffraction spectrometer (XRD) and scanning electron microscope (SEM). Particle size and specific surface area were also studied.