Kieselguhr filtration

An editorial in "Filtration and Separation" [59] highlights the reluctance of the beer brewers to change over from kieselguhr filtration to membranes, but judges that the examples of fruit juice and wine production show good market prospects. 

Control Precoat and kieselguhr filtration Tangential filtration ... 

F. 20.16 Kieselguhr filtration diagram showing a section through sheet or leaf, precoat, and normal kieselguhr. 

H. S. Thatcher, Sugar Filtration—Improved Methods Filtration, Kieselguhr Co. of America, Lompoc, Calif., 1915. 

Diatomaceous earth (Celite 535 or 545, Hyflo Super-cel, Dicalite, Kieselguhr) is purified before use by washing with 3M hydrochloric acid, then water, or it is made into a slurry with hot water, filtered at the pump and washed with water at 50° until the filtrate is no longer alkaline to litmus. Organic materials can be removed by repeated extraction at 50° with methanol or chloroform, followed by washing with methanol, filtering and drying at 90-100°. 

The phosphorodichloridate was hydrolyzed by adding to a stirred solution of sodium carbonate (253 grams) in water (2.9 liters). After 1 hour the solution was cooled and acidified with a solution of concentrated sulfuric acid (30 ml) in water (150 ml) and then extracted with a mixture of tetrahydrofuran and chloroform (2.3/1 3 x 1 liter). The tetrahydro-furan/chloroform liquors were bulked and evaporated to dryness to give a light brown oil. This was dissolved in water (1 liter) and titrated with 2N sodium hydroxide solution to a pH of 4.05 (volume required 930 ml). The aqueous solution was clarified by filtration through kieselguhr and then evaporated under reduced pressure to a syrup (737 grams). 

A mixture of 1-methoxynaphtalene (1.90 g, 12 mmol) and Kieselguhr-supported copper(II) bromide (24 g) in benzene (150 ml) was stirred at 30°C for 3 h. The rnixmre was filtered, and the spent reagent was washed with benzene. The combined filtrate was concentrated, and the residue was distilled under vacuum to give 2.3 g (85 %) of 4-bromo-1-methoxynaphtalene. Bp 155-157°C/5 Torr (lit. 159-160°C/5 Torr (ref 15)). 

All the filtrations in the purification of tyrosine, except possibly the last, are best done on a 20-cm. Buchner funnel. Whenever charcoal is used, kieselguhr may be employed to obtain a clear filtrate. 

In order now to remove proteins from the thin sludge it is vigorously stirred with 0-05 A-acetic acid in amount just sufficient to change the colour of methyl red (pH=4) (test with a sample), and is then filtered as above after shaking with a little kieselguhr if necessary. The filtrate is made neutral to litmus with dilute ammonia and in this condition, protected by a little toluene, can be kept unchanged for several days. 

Filter Aids are porous powders added in small quantities to a soln or suspension to be filtered, in order to increase the efficiency of filtration. They are useful when handling suspensions of finely divided solids or of colloidal materials. The aid should not be much. heavier than die liquids to be filtered, so that it will not settle immediately but will remain in suspension for a while. Kieselguhr and paper pulp are the most widely used filter aids. Others are sawdust, charcoal, Fuller s earth, magnesia, salt, gypsum and some activated charcoals. The charcoals act as decolorizers at the same time... 

Filtration through Hopkins and Williams kieselguhr filter-aid cake speedily removes even colloidal copper halides and breaks up any emulsion. 

A solution of S-iodomethyl-6a,9a-difluoro-lip-hydroxy-16a-methyl-3-oxo-17a-propionyloxyandrosta-l,4-diene-17p-carbothioate (310 mg) in acetonitrile (10 ml) was stirred with silver fluoride (947 mg) for 3 days at room temperature in the dark. Ethyl acetate (100 ml) was added and the mixture was filtered through kieselguhr. The filtrate was washed successively with 2 N hydrochloric acid, water, saturated brine, then dried. The solvent was removed and the residue was subjected to column chromatography in chloroform then chloroform-acetone (19 1). The product was eluted with ethyl acetate and crystallised on concentration of the solution to give S-fluoromethyl 6a,9a-difluoro-lip-hydroxy-16a-methyl-3-oxo-17a-propionyloxyandrosta-l,4-diene-17p-carbothioate (0.075 g) melting point 272-273°C (dec.), [a]D= +30° (c 0.35). 

Dissolve the copper(ll) nitrate solid (6.0 g) in water (300 mL) in a 1 L conical flask containing a stirrer bead and add a solution of the 3,7-dithianonane-1,9-diamine (5.0 g) in methanol (50 mL) slowly. Warm (to 50°C) and stir for 1 h. Cool and filter through Kieselguhr (or an alternative filter aid) under suction to yield a dark purple filtrate. 

Palladium on carbon (10%, 1.00 g) was added to a suspension of 3-(l-naphthyl)acrylic acid (50.0 g) in 500 ml THF and hydrogenated 18 hours at 6 atm of hydrogen. The mixture was then filtered through a kieselguhr pad and the pad washed three times with 10 ml EtOAc. The filtrate was concentrated and 50.0 g product isolated as a solid. 

The oil was dissolved in 45 ml THF and added to a mixture of 10% palladium on carbon (0.50 g) and 5.82 ml 2,6-lutidine in 30 ml THF, then hydrogenated 4 days at 2 atm hydrogen. The mixture was then filtered through a kieselguhr pad, the filtrate concentrated, and a solid isolated. The solid was then dissolved in 20 ml DMF and treated with 4.53 ml ethyl cyanoacetate and sulfur (1.36 g), then stirred 2 hours at 50°C. The mixture was then treated with 300 ml water and 50 ml brine and extracted three times with 300 ml diethyl ether. The extracts were dried with MgS04 and concentrated. The residue was purified by chromatography with silica using diethyl ether/hexane, 2 3, and ll.OOg product isolated. 

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