Abstract: In this study, attapulgite was used as an adsorbent in the bleaching process of soybean oil, and its adsorption behavior and mechanism were explored by physical characteristics, kinetic and thermodynamic analysis. Our investigation showed that attapulgite mainly consisted of small crystal bunches and monocrystals with pore size distributed in the range of 1.5–10.0 nm. Thermodynamic analysis indicated that the adsorption capacity of attapulgite increased with elevating temperature, while the adsorption pattern kept stable. Kinetic analysis showed that attapulgite could rapidly adsorb minor components like chlorophyll. The adsorption rate onto attapulgite in hexane followed the decreasing order: chlorophyll > linoleic acid > phosphatide > carotenoid, whereas the adsorption rate in soybean oil followed the decreasing order: chlorophyll > carotenoid > free fatty acid > phosphatide. All the results revealed that the mechanism of oil bleaching with attapulgite was via pore filling adsorption accompanied by hydrogen bond adsorption and chemical adsorption.

Key words: attapulgite, oil bleaching process, absorption kinetics, mechanism