A laboratory study of the press effect in adsorptive bleaching

The so-called press effect is widely credited with enhancing the overall efficiency of bleaching clays in commercial operations. Laboratory bleaches are generally done with one use of bleaching clay, while plant operations often include a process in which spent clay in a filter press acts as a fixed bed to remove additional impurities from slurry-treated oil. In this study, the press effect is simulated in the laboratory by measuring the influence of a progres-sively-built filter cake on concentrations of carotenes and chlorophyll in successive batches of slurry-contacted oils. The oil used was canola; the clay tested was a commercially available acid-activated clay classified to two different average particle sizes. Conditions were chosen to simulate those used in commercial operations. Better total bleaching was seen from the first batch to the last as filter cake was built up. In addition, a significant particle size effect was seen. Presented at the 83rd AOCS Annual Meeting and Exposition, Toronto, Ontario, Canada, May 10–14, 1992.