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Ultrafiltration transmembrane pressure differences

Microfiltration (MF) and ultrafiltration (UF) involve contacting the upstream face ofa porous membrane with a feed stream containing particles or macromolecules (B) suspended in a low molecular weight fluid (A). The pores are simply larger in MF membranes than for UF membranes. In either case, a transmembrane pressure difference motivates the suspending fluid (usually water) to pass through physically observable permanent pores in the membrane. The fluid flow drags suspended particles and macrosolutes to the surface of the membrane where they are rejected due to their excessive size relative to the membrane pores. This simple process... [Pg.141]

The physical Interpretation of these results is rather straightforward. We have shown equation 6 as an accurate representation of ultrafiltration during hemodialysis. The effective solute transmembrane osmotic pressure differences given by... [Pg.72]

In hemodialysis, low molecular metabolic waste such as urea, creatinine, and other toxic substances (solutes up to 6000 mol wt) are removed from the blood of uremia patients by diffusive transport, which is driven by a concentration gradient of blood solutes being dialyzed against a physiological solution. A complimentary process is hemofiltration, in which solutes up to 20,000 mol wt are removed via an ultrafiltration membrane, the transport being caused by a convective transmembrane flux generated by mild hydraulic pressure differences across the membrane. [Pg.655]

The bench-scale continuous membrane bioreactor (MBR) system consisted of three parallel bioreactors, each with 1 L working volume and designated as bioreactors 2, 3 and 4. A hollow fiber immersed ultrafiltration membrane (ZeeWeed, ZW-1 , GE Water) with 0.045 m (0.5 tf) of membrane area was installed in each bioreactor (Figures 1 2). Filtration was by siphon demanding no permeate pumping. The transmembrane pressure (TMP) necessary to produce permeation was provided by the 1.1 m difference in elevation between the bioreactors (installed in a fume hood), and the permeate collection assembly at floor level. The TMP was kept constant at 0.11 bar or 11 kPa. [Pg.295]

In order to solve the problems that occurred with unmodified cellulosic membranes, synthetic membranes were developed. The first synthetic polymeric membrane was produced in the early 1970s. Since that time, various synthetic polymers such as poly-sulfone, polyamide, poly(methyl methacrylate), polyethersulfone, polyethersulfone/ polyamide have been used in the production of synthetic hemodialysis membranes [20,21]. Synthetic membranes have large mean pore size and thick wall structure. These properties provide high ultrafiltration rate, which is necessary for hemodialysis to be achieved with relatively low transmembrane pressures [20]. The main difference in synthetic and cellulosic membranes is the chemical composition of the membrane. Synthetic membranes are made from manufactured thermoplastics, while both modified and unmodified cellulosic membranes are prepared from natural polymers [20]. [Pg.446]

Ultrafiltration can adequately produce disinfected water directly from strrface water for different applications. MF can also be used for disinfection, although not all viruses are removed. However, direct membrane filtration is limited by fouling, which, during constant-flux filtration, leads to a continuous increase in transmembrane pressure. In addition, UF and MF membrane treatment alone cannot effectively and consistently remove organic material, measured as total organic carbon (TOC), and THM (tri-halo-methane) precursors, measured as chloroform formation potential (Berube et al., 2002). [Pg.142]


See other pages where Ultrafiltration transmembrane pressure differences is mentioned: [Pg.321]    [Pg.259]    [Pg.179]    [Pg.442]    [Pg.294]    [Pg.258]    [Pg.397]    [Pg.849]    [Pg.67]    [Pg.353]    [Pg.955]    [Pg.19]    [Pg.261]    [Pg.990]    [Pg.955]    [Pg.155]    [Pg.493]    [Pg.371]   
See also in sourсe #XX -- [ Pg.134 , Pg.136 ]




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