Sepiolite: An effective bleaching adsorbent for the physical refining of degummed rapeseed oil

The efficiency of Turkish sepiolite in bleaching degummed rapeseed oil has been investigated. Experimental results indicate that the bleaching efficiency is more dependent on the ratio of sepiolite to oil than on operating parameters such as contact time and temperature. An increase in the sepiolite dosage reduces the color bodies of the rapeseed oil. Its effect on oxidation state, however, is complex and related to both primary and secondary oxidation products. The removal of impurities such as chlorophyll a, β-carotene, and phosphorus increases with increasing sepiolite dosage and reaches a maxumum at 1.5% sepiolite addition and 100°C bleaching temperature. Chlorophyll a, β-carotene, and phosphorus adsorptions can be described by a mechanism involving surface are and porosity of acid-activated sepiolite as key variables. The sorption is also independent of the polarity of the adsorbate molecules. Direct comparison of activated sepiolite with the commercial bleaching earth Tonsil 210 FF shows that in some respects sepiolite offers significant advantages.