Filter membranes

Filtration. The filtration process depends on the physical retardation of microorganisms from a fluid by a filter membrane or similarly effective medium. The effectiveness of this process is also influenced by the bioburden (6). HoUow-fiber membranes (qv) are most often employed. The resultant... 

In Sittt Filter Membranes In situ membranes are being fitted into incinerator flue-gas stacks in an attempt to reduce hydrocarbon emissions. Two types of commercially available gas separation membranes are being stndied (I) flat cellnlose acetate sheets and (2) hoUow-tnbe fiber modules made of polyamides. 

R/0 unit Reverse Osmosis Unit for water purification in small aquariums and miniature yard-ponds, utilizes a membrane under pressure to filter dissolved solids and pollutants from the water. Two different filter membranes can be used the CTA (cellulose triacetate) membrane is less expensive, but only works with chlorinated water and removes 50-70% of nitrates, and the TFC membrane, which is more expensive, removes 95% of nitrates, but is ruined by chlorine. R/0 wastes water and a system that cleans 100 gallons a day will cost ft-om 400 to 600 with membrane replacement adding to the cost. A unit that handles 140 gallons a day will cost above 700,00. 

Cellulose acetate (CA) has been known, and industrially employed for decades as films, fibers, filters, membranes, tubes, and utensils, as well as other consumer products, including eyewear, fashion accessories, pens, brushes, toys, among others [13]. The market for Filter Tow, which is made from crimped, endless CA filaments, has seen a tremendous growth in the cigarette market, reaching more than 600 thousand metric tons in 2003 [14]. Additionally, cellulose mono-acetates have several potential applications, because they can be made into either water absorbent, or water-soluble polymers [15]. 

They may also be required in industrial applications where they become part of venting systems on fermenters, centrifuges, autoclaves and freeze-dryers. Certain types of filter (membrane filters) also have an important role in sterility testing, where they can be employed to trap and concentrate contaminating organisms from solutions under... 

Mobile phase The HPLC mobile phase is made up as follows. Prepare 2 L of acetate buffer by dissolving 13.6 g of sodium acetate and 6 mL of glacial acetic acid in 2 L of deionized water. Adjust the solution to pH 4.8 with concentrated sodium hydroxide solution (or glacial acetic acid) if necessary. Mix 2 L of buffer with 1.6-2 L (the amount depends on the particular commodity) of methanol. Eilter the solution through a 0.22-pm Nylon 66 filter membrane before using the mobile phase Absolute ethanol Aaper Alcohol and Chemical Co. (200 proof)... 

Hydrophilic Filter Membrane PAMPA Model (Aventis Model)... 

Shasby DM, SS Shasby. (1990). Endothelial cells grown on filter membranes. In HM Piper, ed. Cell Culture Techniques in Heart and Vessel Research. Stuttgart Springer-Verlag, pp 212-219. 

Two-Filter Method TF flow rate 40 /min, sampling time lhr, filter membrane filter, gross counting or -spectrometry, Rn and Tn measured... 

The objective of the present study is to develop a cross-flow filtration module operated under low transmembrane pressure drop that can result in high permeate flux, and also to demonstrate the efficient use of such a module to continuously separate wax from ultrafine iron catalyst particles from simulated FTS catalyst/ wax slurry products from an SBCR pilot plant unit. An important goal of this research was to monitor and record cross-flow flux measurements over a longterm time-on-stream (TOS) period (500+ h). Two types (active and passive) of permeate flux maintenance procedures were developed and tested during this study. Depending on the efficiency of different flux maintenance or filter media cleaning procedures employed over the long-term test to stabilize the flux over time, the most efficient procedure can be selected for further development and cost optimization. The effect of mono-olefins and aliphatic alcohols on permeate flux and on the efficiency of the filter membrane for catalyst/wax separation was also studied. 

The prototype shell-and-tube type cross-flow filtration modules (Pall Corp.) used for filtration tests are welded into a stainless steel shell enclosure. The modules have an inlet (filtrate) and outlet (retentate) port (both at tube sides) with Vi-inch tubing ends, and a permeate port, located near the midpoint of the shell side of the unit. The stainless steel filter membranes have a nominal pore size of 0.1 pm. The surface of the filter media is coated with a proprietary submicron layer of zirconia. 

Cross-flow filtration systems utilize high liquid axial velocities to generate shear at the liquid-membrane interface. Shear is necessary to maintain acceptable permeate fluxes, especially with concentrated catalyst slurries. The degree of catalyst deposition on the filter membrane or membrane fouling is a function of the shear stress at the surface and particle convection with the permeate flow.16 Membrane surface fouling also depends on many application-specific variables, such as particle size in the retentate, viscosity of the permeate, axial velocity, and the transmembrane pressure. All of these variables can influence the degree of deposition of particles within the filter membrane, and thus decrease the effective pore size of the membrane. 

As presented in Figure 15.10, after 100 h TOS the permeate valve was closed, and thus the transmembrane pressure fell to zero. The pilot plant remained in a standby mode and unmanned for approximately 75 h. During this period, the catalyst slurry was circulated through the cross-flow filter, without permeate flow radially through the filter membrane (i.e., test conditions were constant with the... 

An active flux maintenance procedure was initiated at this point (about 330 h TOS), beginning with a 2 s back-flush of clean permeate through the filter membrane. This active flux maintenance cycle was continued every 30 min for just over 24 h. The flux initially recovered to 0.90 lpm/m2 (32.0 GPD/ft2), but declined again within 24 h to a baseline value of 0.76 lpm/m2 (26.7 GPD/ft2) without clean permeate back-flush. The flux maintenance method was then returned to passive (no back-flush with clean permeate) mode, only increasing the flux off-time to 60 s every 30 min. Thereafter, the flux steadily declined over the next 120 h TOS from 0.77 to 0.58 lpm/m2 (27.3 to 20.4 GPD/ft2). At 480 h TOS, a 1 h flux off-cycle was attempted, resulting in an increase of the flux back to 0.82 lpm/m2 (29.1 GPD/ ft2), a 42.6% increase. When the flux off-cycle was returned to the 60 s off-cycle for the next 48 h, it was found that the permeate flux decreased to 0.62 lpm/m2 (21.9 GPD/ft2). Applying another 1 h flux off-cycle returned the flux to 0.721pm/... 

In this chapter we report recent analytical applications of CL imaging for the detection of biospecific reactions in macrosamples such as microtiter plates of different format (96 or 384 wells), filter membranes and irregular surfaces represented by specimens related to the cultural heritage, and results obtained when the CCD detector is coupled with optical microscopy for enzyme localization, immunohistochemical reactions, and complementary DNA (cDNA) detection (Table 1). 

Filter membranes HRP/H202/luminol AP/dioxetanes Detection of nucleic acids and proteins... 

Beside SILP experiments with silica as support material, reports have also been made on the use of membranes coated with ionic liquid catalyst solution for the hydrogenation reaction of propene and ethene. The membranes were obtained by supporting various ionic liquids, each containing 16 to 23 mmol Rh(I) complex Rh(nbd)(PPh3)2 (nbd=norbornadiene), in the pores of poly(vinylidene fluoride) filter membranes [118]. 

Drever JI. Preparation of oriented clay mineral specimens for X-ray diffraction analysis by a filter-membrane peel technique. Am. Mineral. 1973 58 553-554. 

Each filter has demonstrated the capacity to filter the full brine flow of 195 m3 h 1. The pressure drop through the filter medium is measured and monitored continuously. Typically, it is nearly constant over a 2-h filtration at 195 m3 h 1. Back-pulse cleaning restores the initial pressure drop from cycle to cycle, with only a slow increase over time. After 12 months running time, the initial pressure drop at the beginning of the filter cycle had increased by 0.6 bar. The filter membranes were chemically cleaned with 5 % hydrochloric acid. After a cleaning time of 2 h the filter was started again and the pressure drop was less than 0.1 bar greater than that of new filter socks. 

Since the installation of the retrofit, the brine quality has been monitored using different types of analysis (MS, ICP, EDX, etc.). The filtration efficiency of the GORE-TEX membranes has always met the Bayer specifications, which are significantly less than 100 ppb iron and aluminium. The filter membranes were put into operation in August 1998 and continue in service at this time. 

---