Refining of edible oils using recycled spent bleaching earth.
Nalugo, Alice Tendo
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Spent bleaching earth (SBE), a solid waste generated from the oil refinery, may be recycled rather than being simply disposed of in landfills. The aim of this research was to investigate the recycling of SBE and to evaluate the performance of the recycled SBE in bleaching crude oil. Two types of regeneration processes were performed, i.e. (a) Solvent extraction followed by heat treatment, and (b) direct heat treatment. Heat treatment was conducted in a muffle furnace at temperatures ranging from 586 to 603°C. The ash content in the SBE was 56.83 % was found to be lower than that of Tonsil, 85.21% due to the presence of phosphate mineral residues carried away from the crude palm olein degumming process. Some of the deoiled heat-regenerated SBE (DHRSBE) was treated with 0.1N of hydrochloric acid to investigate to the effect of acid activation on the adsorbability of neutral recycled bleaching earth. Red colour indices of oils were used to determine the regeneration efficiency. Direct heated- regenerated spent bleaching earth (HRSBE) yielded a higher regeneration efficiency than the deoiled-heated-regenerated spent bleaching earth (DHRSBE) produced by solvent extraction and heat treatment. This is because moisture, impurities and dirt were more completely removed by direct heating than by solvent extraction. Physiochemical characteristics of oil were analyzed on the extracted residual oil and the results obtained were: 1.1934% free fatty acids; 3.5R/5.0Y colour; cloud point, 6.50C; melting point, N/A; iodine value, 56g/1000g and saponification value, N/A. The pH of fresh bleaching earth, fresh SBE, HRSBE,DHRSBE and acid- leached DHRSBE were 7.74, 4.6, 7.78, 7.85 and 3.0 respectively.The heat regenerated spent bleaching earth (HRSBE) was also compared with the fresh bleaching earth (Tonsil) based on their moistur content and the experimental results showed that the moisture content in HRSBE was 1.2%, while that in Tonsil was 13%. It can be concluded from the present study that acid activated bleaching earth is more effective than natural bleaching earth.