Abstract

• Bleaching or purification is an important step in the refining of fats and vegetable / animal oils for industrial applications. Bleaching clay primarily removes colouring pigments such as chlorophylls and carotenes but peroxide and other impurities (e.g., soaps, trace metals and phosphatides) are also important target of the bleaching process. In the research, palm oil sample was collected to carry out the adsorption of colouring materials and impurities by using raw bentonite, 4 M and 8 M HCl activated bentonite and foreign bleaching clay. In this study, raw bentonite clay was treated with 4 M HCl and 8 M HCl solutions to get better adsorption properties. Characterizations of raw bentonite clay, 4 M HCl and 8 M HCl activated bentonite clay samples were carried out by using FT IR, XRD and chemical analyses. Before bleaching processes, some properties (moisture and impurities, iodine value, peroxide value, free fatty acid content, saponification value, unsaponifiable matters, refractive index and specific gravity) were determined by AOAC and AOCS methods. After treatment with raw and acid activated bentonite clay sample, iodine value and saponification value of palm oil increased, while free fatty acids content, peroxide values, unsaponifiable matters, moisture and impurities of palm oil sample decreased. In this research, bleaching efficiencies of the bentonite clay on plam oil were determined spectrophotometrically. In this research, bleaching efficiency of the raw bentonite clay, 4 M HCl activated and 8 M HCl activated bentonite clay samples were determined at 65, 80 and 90 ºC for different contact times. The bleaching efficiencies of raw bentonite clay samples, 4 M HCl activated bentonite clay, 8 M HCl activated bentonite clay samples and foreign bleaching clay were 14.3, 42.8, 49.9 and 26.6 %, respectively, for 100 min contact time. Therefore, 8 M HCl activated bentonite clay sample give the highest bleaching efficiencies. This may concern with the structure of 8 M HCl activated bentonite clay sample. According to XRD data, 8 M HCl activated bentonite clay sample showed the amorphous nature due to the clay structure collapsing, whereas raw and 4 M HCl activated bentonite clay samples were crystalline nature. The amorphous nature of the 8 M HCl activated bentonite clay sample has more sorption ability to carotene in oil sample.