Solid/liquid separation diatomaceous earth

Filter. A filter is used in some cases when coagulation and sedimentation do not completely separate the solids from the liquid waste in areas where sand and sandstone formations are susceptible to plugging. Filters with a series of metal screens coated with diatomaceous earth or cartridge filters are typically used.27 Where limestone formations with high solution porosity are used for injection, filtration is usually not required. 

The material to be filtered is fed into the vessel under pressure, and separation takes place with the solids being deposited on the leaf surface, and the liquid passing through the drainage system and out of the filter. Cycle times are determined by pressure, cake capacity or batch quantity. Where particularly fine solids must be removed, a layer of precoat material may be deposited on the leaves prior to filtration, using diatomaceous earth, Perlite, or other suitable precoat materials. 

Column packing consists of two essential ingredients—the inert supporting phase and the stationary liquid phase. The solid supporting phase is usually an insert material of uniform particle size. Diatomaceous earth is a frequently used solid support, although celite, firebrick, and glass beads are also used. The particle size is important in achieving the maximum separation or efficiency. However, smaller particles inhibit the flow rate of gas due to the increased resistance of the denser medium. 

In solid-supported LLE (SS-LLE) or liquid-liquid cartridge extraction, the aqueous sample is applied on to a dry bed of inert diatomaceous earth particles in a flow-through tube or in 96-well plate format. After a short equihbration time (3-5 nun), organic solvent is added. The organic eluate is collected, evaporated to dryness, and reconstituted in mobile phase. Compared to conventional LLE procedures, SS-LLE avoids the need for vortex-mixing, phase separation by centrifugation, and phase transfer by aqueous layer freezing. 

However, conventional LLE requires precise removal of the aqueous layer, which is not amenable to large number of samples. To solve this problem, solid supported liquid-liquid extraction (SLE) was developed. Instead of using separation funnels, the reaction mixture is loaded on a cartridge packed with diatomaceous earth, which is pretreated with an aqueous buffer and contains an aqueous layer. A water-immiscible solvent, usually methylene chloride or ethyl acetate, is then applied to elute the products off the cartridge, leaving more water-soluble impurities on the column. 

There are two general types of GC column packed and capillary (also known as open tubular). Packed columns contain a finely divided, inert, solid support material (commonly based on diatomaceous earth) coated with a viscous liquid stationary phase. Most packed columns are 1.5-lOm in length and have an internal diameter of 2-4mm. The original glass capillary columns had an internal diameter of a few tenths of a millimeter and were also one of two types, wall-coated open tubular (WCOT) and support-coated open tubular (SCOT). WCOT columns consist of a capillary tube whose walls are coated with liquid stationary phase. In SCOT columns the inner wall of the capillary is lined with a thin layer of support material such as diatomaceous earth, onto which the stationary phase has been adsorbed. Both of these types of capillary column provide greater separation efficiency than packed columns, but since 1979 they have... 

Kirkland [6] has studied the support in some detail for several model systems, and has reported much improved performance for this material in liquid-liquid chromatography when compared to coated glass beads or diatomaceous earth. A number of separations have been described using Durapak type supports and by Majors [1] using various solid core supports operating at 34 MPa. 

The stationary liquid phase is normally coated as a thin film on an inert solid support. The support is composed of small, uniformly meshed granules, so that a large surface area of the liquid phase is available for contact with the vapor phase to ensure efficient separation. Some common types of solid supports indude Chro-mosorb P and Chromosorb W, which are composed of diatomaceous earth. The surface areas of these supports vary from 1 to 6 m g- Columns are now commercially available with a wide variety of liquid phases on different solid supports. An alternative method of supporting the liquid phase is used in capillary columns. In these columns, the liquid is coated directly onto the inner walls of the tubing. These columns are highly efficient but relatively expensive. 

The simplest equipment consists of a tube, which may be straight, U-shaped or coiled, containing an inert solid acting as a support for the stationary phase. The support usually consists of narrow screen fractions of a diatomaceous earth (Celite, kieselguhr) or ground firebrick (Chromo-sorb), and the stationary phase is a liquid which has low volatility at the temperature of the experiment. It may be either polar or non-polar depending on the composition of the mixture to be separated. The column... 

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