Powdered activated carbons layer filtration

In order to prevent peptization of the carbon that often occurs, Bender, Douglas, and Cuthbert40 developed a percolation unit. One part of cellulose pulp is intimately mixed with 1 to 3 parts of powdered activated carbon and a 2 to 4 inch layer of the mixture is placed in the filter unit. A 1 % pectin solution at 50° C is then percolated through the unit. The filtrate usually has no smoky appearance which would indicate the presence of fine carbon particles, but, should any carbon pass through, it is removed by filtration through a layer of filter aid. 

Decolorization of sugar solutions using powdered active carbons can be carried out by two methods contact batch method and the continuous layer filtration method. There is a third method, which is a combination of both the methods. 

In a 500 ml round-bottomed flask equipped with a magnetic stirrer are placed 22 5 g (0 105 mole) of powdered sodium metaperiodate and 210 ml of water The mixture is stirred and cooled m an ice bath (Note 1), and 12 4 g (0 100 mole) of thio-anisole (Note 2) is added The reaction mixture is stirred for 15 hours at ice-bath temperature and is then filtered through a Buchner funnel The filter cake of sodium iodate is washed with three 30-ml portions of methylene chloride The wrater methylene chloride filtrate is transferred to a separatory funnel, the lower methylene chloride layer is removed, and the water layer is extracted with three 100-ml portions of methylene chloride The combined methylene chloride extracts are treated with activated carbon (Note 3) and dried over anhydrous sodium sulfate (Note 4) The solvent is removed at reduced pressure to yield 13 6-13 9 g of a slightly yellow oil (Note 5) which crystallizes on cooling The crude sulfoxide is transferred to a 25 ml distillation flask with the aid of a small amount of methylene chloride After removal of the solvent, a pinch of activated carbon is added to the distillation flask (Note 6) Simple vacuum distillation (Note 7) of the crude product through a short path still affords 12.7-12 8 g (91%) of pure methyl phenyl sulfoxide, b p 78-79° (0 1 mm ), m p. 33-34° (Notes 8 and 9)... 

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