Gravity filtered

Fig. 5. Example of a deep bed filter, ie, a downflow gravity filter.

When the resistance opposing fluid flow is small, gravity force effects fluid transport through a porous filter medium. Such a device is simply called a gravity filter. 

Potable water treatment Granular activated carbons (GAC) installed in rapid gravity filters Removal of dissolved organic contaminants, control of taste and odor problems... 

Gravity filters used in the density removal are subdivided into... 

Vacuum Filters. If, due to the nature of the liquid, the gravity filter be comes unsuitable, a vacuum filter is used to create a substantial pressure difference. Vacuum filters can be divided into the following types ... 

Dissolve your product in a low boiling point solvent. Maybe ether or hexane or the like. Now dry this whole solution, and gravity filter. Remove the solvent carefully. Hoo-ha Dried product. 

Trash in the sample. Redissolve the sample, gravity filter, then evaporate the solvent. 

Water in the sample. This shows up as droplets or as a layer of water on the top or the bottom of the vial, or the sample is cloudy. Dry the sample with a drying agent (see Chapter 7, Drying Agents ) and gravity filter into a clean dry vial. 

Trash floating in the sample. For that matter, it could be on the bottom, lying there. Gravity filter into a clean, dry vial. 

When shaking is complete, the suspension is gravity filtered through a standard fine filter paper into a sample container. If the filtrate is cloudy, it can be filtered through the same filter paper again. If this is not sufficient, the filter... 

Batch vacuum filters were developed from gravity filters and, in essence, Buchner funnels as used in laboratories and Nutsche type filters as used in industry are similar to gravity filters, except that they feature a vacuum pump or some other vacuum generating equipment to reduce the pressure under the filter medium, thereby increasing the driving force across the filter medium. 

The purple solid is collected by suction filtration and subsequently dissolved in diethyl ether (300 mL), and the resulting dark blue solution is washed with 5 x 200 mL portions of distilled water. The diethyl ether layer is dried over anhydrous MgS04, gravity filtered, and evaporated to dryness on a rotary evaporator. The resulting dark purple/blue crystals are allowed to air dry. Yield 85 g (0.20 mol) of crude Cu(tmhd)2, 75%. 

Samples of gravity-filtered broth are invariably turbid and, without treatment, totally unsuitable for spectrophotometric work. The form of treatment depends... 

Five grams of starch-g-polyacrylamide was dispersed in 333 ml of water and the mixture was heated for 4.5 hr at 95-100°C. The cooled dispersion was then treated with ultrasound, as described for starch-g-PAN in DMSO. The resulting solution was gravity-filtered through fluted Whatman 54 paper, and the filtrate was freeze-dried to give 4.4 g of polymer. To give a denser, more compact product, which might more closely resemble soluble starch-g-PAN, the freeze-dried polymer was dispersed in 20 ml of water, and the polymer was precipitated from the thick paste by addition of ethanol. The polymer was separated by filtration, washed with ethanol, and vacuum dried at 60°C. 

Gravity filters are seldom used in the process industries because they offer low filtration rates, however, simple Nutsch filters are sometimes found in the pharmaceutical industry at pilot scale. The Nutsch filter is a tank with a perforated base on which a filter cloth can be supported. The feed slurry liquid filters through the cake and cloth under its own weight. Although these units are low cost, they are labor intensive to operate, cannot be contained for protection of the product or the operator, and are slow. 

For purification, the crude product is dissolved in dichloromethane (8 mL/g) and is gravity-filtered through a fine-mesh paper (Whatman no. 542 or equivalent). The product is precipitated by dropwise addition of anhydrous diethyl ether to the dichloromethane solution, until 5 mL ether has been added for every milliliter of dichloromethane solution originally present. The mixture is chilled for several hours at — 35°, filtered, washed with diethyl ether, and air-dried. 

The product (0.5 g) is recrystallized by stirring it with acetonitrile (20 mL) for 5 min (or until product has dissolved) and then is gravity-filtered (Whatman no. 1 paper). The filtrate is warmed to about 65°, and water (about 5 mL) is added while the solution is kept warm. Crystals usually appear upon addition of the water, and then the solution is allowed to cool to room temperature and evaporate for 24 hr. Approximate yield is 0.45 g. Anal. Calcd. for C50H48N6O8B2Fe C, 63.99 H, 5.16 N, 8.96. Found C, 63.43 H, 5.12 N, 9.04. 

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