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Flat-sheet devices

Membrane Devices for Sample Preparation 13.1.3.1 Flat-Sheet Devices... [Pg.379]

The original expanded film membranes were sold ia roUs as flat sheets. These membranes had relatively poor tear strength along the original direction of orientation and were not widely used as microfiltration membranes. They did, however, find use as porous inert separating barriers ia batteries and some medical devices. More recentiy, the technology has been developed to produce these membranes as hoUow fibers, which are used as membrane contactors (12,13). [Pg.63]

Cassettes Cassette is a term used to describe two different cross-flow membrane devices. The less-common design is a usually large stack of membrane separated by a spacer, with flow moving in parallel across the membrane sheets. This variant is sometimes referred to as a flat spiral, since there is some similarity in the way feed and permeate are handled. The more common cassette has long been popular in the pharmaceutical and biotechnical field. It too is a stack of flat-sheet membranes, but the membrane is usually connected so that the feed flows across the membrane elements in series to achieve higher conversion per pass. Their popularity stems from easy direct sc e-up from laboratoiy to plant-scale equipment. Their hmitation is that fluid management is inherently veiy hmited and inefficient. Both types of cassette are veiy compact and capable of automated manufacture. [Pg.2046]

Two configurations of liquid membranes are mainly used in analytical applications flat sheet liquid membranes that give acceptable extraction efficiencies and enriched sample volumes down to 10-15 pL, and hollow fiber liquid membranes that allow smaller enriched sample volumes. Flat sheet liquid membrane devices consist of two identical blocks, rectangular or circular in shape, made of chemically inert and mechanically rigid material (PTFE, PVDF, titanium) in which channels are machined so that when... [Pg.576]

Emulsification devices where the membrane is immersed in a stirred vessel containing the continuous phase, so as to obtain a batch emulsification device operating in deadend emulsification mode, have also been developed (Figure 21.13). Both flat-sheet and tubular membranes are used. In this membrane emulsification device, the continuous phase kept in motion creates the shear stress at the membrane surface that detaches the forming droplets. In a different operation mode, that is, when the continuous phase is not stirred, droplet formation in quiescent conditions is obtained. [Pg.476]

The kinetics of drug release from matrix devices containing uniformly dissolved or dispersed drug are well documented. In a flat sheet geometry, where the surface area is relatively constant,... [Pg.7]

The objective in membrane design is to pack as much permeation surface area into as small a space as possible to minimize operation requirements. Depending on the application, various membrane designs are used, such as flat sheet, disc tube, hollow fiber, spiral wound, and ceramic (17). Module design has a measurable effect on the hydrodynamic performance of the cross-flow membrane device. The advantages and disadvantages of different membrane modules are summarized in Table 1. [Pg.2847]

From outward appearance membrane contactors look similar to other membrane devices. However, functionally the membranes used in contactors are very different. They are mostly nonselective and microporous. Membrane contactors can be made out of flat sheet membranes and there are some commercial apphcations. Most common commercial membrane contactors are, however, made from small-diameter microporous hollow fiber (or capillary) membranes with fine pores (illustrated in Figure 2.1) that span the hoUow fiber wall from the fiber inside surface to the fiber outside surface. The contactor shown as an example in Figure 2.1 resembles a tube-in-sheU configuration with inlet/outlet ports for the shell side and tube side. The membrane is typically made up of hydrophobic materials such as Polypropylene, Polyethylene, PTFE, PFA, and PVDF. [Pg.8]

Classically, flat-sheet porous PTFE or polypropylene membranes are used as support for the membrane liquid and mounted in holders (cells, contactors) permitting one flow channel on each side of the membrane [1,3,6,8,25]. See Figure 12.1. Such membrane units are typically operated in flow systems and in principle apphcable to aU versions of membrane extraction for analytical sample preparation or sampling. Such a setup can be easily interfaced with different analytical instmments, such as HPLC and various spectrometric instmments, and thereby provides good possibdities for automated operation. Drawbacks of this type of devices are relatively large costs and limited availability, as well as some carryover and memory problems as the membrane units are utilized many times, necessitating cleaning between each extraction. [Pg.347]

The term membrane element refers to the basic form in which a membrane is prepared. There are three types of membrane elements flat sheets, hollow hbers, and tubular membranes. The device within which the membrane element is housed is referred to as the membrane module. The design of the membrane module largely depends on the type of membrane element, as well as on additional requirements such as the need for cleaning and disassembling, the required transmembrane pressure (TMP), and the required hydrodynamic conditions. Some of the different modules types are (see Figures 18.3 through 18.7) ... [Pg.500]

Membrane separation devices are assembled in a number of forms. In a flat sheet form the membrane is laid over a flat porous support. A unit would include a large number of the flat sheets separated by spacers and stacked together. In another configuration the fiat sheet may be spiral-wound with spacers around a perforated tube. Other arrangements involve tubular membranes or hollow fiber membranes assembled in bundles. In the tubular module the membrane is wrapped around a tubular... [Pg.618]

Flat sheet membrane elements are a.ssembled in plate and frame devices to handle larger processing volumes. [Pg.284]

Hie three major membrane configurations, flat sheet, spiral wound, and hollow fiber, each having advantages and limitations, will he reviewed briefly prior to considering the detailed analysis of these devices. Some of these issues include relative magnitudes of active membrane area per unit separator volume, mtninrizakm of pressure buildup in the permeant stream, membrane integrity, and the ease of module manufacture and membrane replacement. [Pg.920]

These new membranes have increased affinity toward impurities and novel membrane chemistry has increased the capacity for impurities under high salt conditions. This new membrane technology offers manufacturers enhanced flexibility, reduced processing time, allows smaller and more flexible production facilities, and reduces operating costs. New device formats have improved scalability with the membranes designed as multiple stacked flat sheets versus the traditional pleated or wrapped membranes. [Pg.269]


See other pages where Flat-sheet devices is mentioned: [Pg.345]    [Pg.347]    [Pg.377]    [Pg.345]    [Pg.347]    [Pg.377]    [Pg.2041]    [Pg.2046]    [Pg.56]    [Pg.964]    [Pg.353]    [Pg.388]    [Pg.1785]    [Pg.1799]    [Pg.1804]    [Pg.51]    [Pg.2211]    [Pg.406]    [Pg.410]    [Pg.935]    [Pg.309]    [Pg.838]    [Pg.957]    [Pg.54]    [Pg.2195]    [Pg.2031]    [Pg.2045]    [Pg.2050]    [Pg.270]    [Pg.158]    [Pg.655]    [Pg.494]    [Pg.129]    [Pg.129]    [Pg.284]   
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