Heavy metal , removal using emulsion

Several methods exist for deacidification of fat or oil. The choice depends on the amount of free fatty acidspresent in crude fat or oil. The removal of fatty acids with 15% sodium hydroxide (alkali refining) is the most frequently used method. Technically, this is not very simple since fat hydrolysis has to be avoided and, moreover, the sodium soap (the soap-stock ), which tends to form stable emulsions, has to be washed out by hot water. After vacuum drying, the fat or oil may contain only about 0.05% free fatty acids and 60 to 70 ppm of sodium soaps. When the fat or oil is treated with diluted phosphoric acid, the content of sodium soaps decreases to 20 ppm and part of the trace heavy-metal ions is removed. 

Semi-aqueous cleaning processes apply hydrocarbon solvent-surfactant emulsions in concentrated form followed by a water rinse, or emulsions in water are used in processes similar to aqueous cleaning. Semi-aqueous cleaning processes are very effective in removing heavy grease, tar, waxes, and other hydrocarbon-based soils. Cleaning solutions can be made compatible with most metals and polymers and metals are not likely to be etched as the solutions are neutral. 

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