Bleaching earth spent

M. Mahramanlioglu, I. Kizilcikli, I.O. Biccer, Adsorption of fluoride from aqueous solution by acid treated spent bleaching earth, J. Fluorine Chem. 115 (1) (2002) 41-47. 

Spent Bleaching Earth (color, residual soapstock)... 

R. Eahn and W. Zschau, Possibilities for the Use of Spent Bleaching Earth, presented at the AOCS 75th Annual Meeting, 1984. 

The major requirement for operation of this extractor is that the densities of the solid material and the solvent be different enough so that the particles will settle out. The Model IV extractor reportedly is efficient in extracting finely particulate foods, pharmaceuticals, and spent bleaching earth (146). 

However, Dijkstra states that current industrial bleaching processes are scaled up laboratory experiments. Accordingly, spent bleaching earth has been in adsorption equilibrium with bleached oil and thus has a much lower adsorbate loading than if this spent earth had been in equilibrium with nonbleached oil. He then raises the question of how much bleaching earth could possibly be saved if spent earth were to be in equilibrium with nonbleached earth as in a truly counter-current process with respect to the present, cocurrent processes. 

Oil Retention/Treatment and Recovery of Entrained Oil As discussed above, the extent of oil retention by the spent bleaching earth (SBE) is mostly a function of filtration equipment performance and the particular blow-down procedure employed by the refiner. Certain properties of SBE (particularly, porosity, and... 

Uses and Methods of Disposal Concerning disposal, there are a number of strategies for dealing with spent bleaching earth, as summarized below Disposal as Generated... 

Direct disposal of spent bleaching earth on farmland is another option that has been examined and found to work well. Studies (138) have shown that 60-90% of the oil is decomposed during the course of a normal six-month growing season by soil bacteria this approach works best in warm climates on sandy soils where some fertilizer has been added. Plants grown in soils treated with spent bleaching earth were normal and may even have benefited from improvements in soil water retention caused by the spent clay addition. 

Another approach for directly disposing spent bleaching earth is to blend it back in with seed being processed through an oil extraction plant. However, if too much is blended in, it can adversely affect the quality of the crude oil being extracted and may cause the mineral limits of the seed meal to be exceeded (128, 129). Spent bleaching clay can also be used as animal feed supplement (139, 140), particularly in broiler feed diets. In pelletized form, the spent bleaching clay is noncombustible. 

The oil content of the spent bleaching earth may range from 25—75% of the weight of the earth. Oil retention is affected by the type of filters, the type of refined oil bleached, and the degree of color reduction. It is important to recover as much of this oil as possible, but methods that are too efficient may cause desorption of the impurities adsorbed by the bleaching earth from the refined oil. Because it is possible to remove a substantial portion of the oil from the spent earth, it may become a regulatory requirement in the future. Oil can be recovered by several methods, some performed on the cake while it is still in the filter and others after it has been removed from the filter. Some of the procedures for oil recovery include (Patterson, 1976 Ong, 1983 Hong, 1983 Svensson, 1976) ... 

Pollard, S.J.T. Sollars, C.J., and Perry, R., A low cost adsorbent from spent bleaching earth The selection of an activation procedure, J. Chem. Technol. Biotechnol.. 50(2). 265-276 (1991). 

Next, the refined oil is bleached (reacted with activated clays, diatomaceous earths, or recoverable silicas) to adsorb phospholipids, color pigments, soaps, peroxides, aldehydes, and other polar compounds, and is recovered by filtration. Spent bleaching earths in the filter cake contain pigments, occasional residual pesticides, aldehydes, and other compounds removed from the oil, and they often present disposal problems. 

Bleaching is carried out under a vacuum of 20-25 mmHg and at a temperature of 95-110°C with retention time of 30-45 min (47). The slurry containing the oil and earth is then filtered to recover a clear, light orange color pretreated oil. Usually a small amount of diatomaceous earth is used to precoat the filter leaves to improve the filtration process. As a quality precaution, the filtered oil is polished through another security filter bag in series, to trap any earth particles that escape through the first filter. This is essential as the presence of spent earth particles in the pretreated oil reduces the oxidative stability of the final RBD oil (46). The spent... 

---