Effective membrane area

Water Permeation and Solute Separation through the Membrane. The measurements of water permeability of the 67 membranes prepared under different conditions were carried out by using an Amicon Diaflo Cell (effective membrane area, 13.9 cm2) under a pressure of 3 kg/cm2 at 25 °C. Some results are listed in Table 1067. It is apparent that much higher water absorption and permeability than the cellulosic membrane are characteristic of the 67 membranes prepared by both the casting polymerization and conventional casting. 

Filtration coefficient The filtration coefficient, Lp, was measured under osmotic pressure utilizing thermostated glass cells ( 0.05°C) equipped with graduated cappillaries ( 0.001 cc). The cells had an effective membrane area of 1.77 cm and each compartment contained v25 cc of solution. One compartment was filled with deionized water and the second with a 1 or 2 molal solution of sucrose (depending upon lEC). 

The apparatus used in this study were illustrated in Fig. 2. The pervaporation cell was a two compartment cell with a 150mL upper compartment, 75 mL of lower compartment. Effective membrane area was 12.5 cm2. The pressure at the... 

FIGURE 6.17 Flat membrane module with an effective membrane area of 1 m (a), obtained by assembling channel corrugated porous ceramic supports (b), from (IGB, 26). 

C over 24 h. Initial pH was adjusted with HCl (5 N) and NaOH (5 N) solution. Batch ultrafiltration was performed in a stirred cell (Amicon model 52, feed volume 50 ml, effective membrane area 12.5 cm ), usually at 3 bars, with membrane YM5 (Amicon, mw cut off 5,000 Dalton). The first 10 ml of permeate were discarded. The next two consecutive 10 ml were analysed to determine the mercury concentration with an atomic absorption spectrophotometer. The rejection coefficient (R) defined as below, was calculated from the feed and permeate concentration of mercury. 

When an electrical potential gradient is imposed on the stack, alternate compartments become enriched and depleted in sodium chloride. A typical module of an electrodialytic salt plant has 1500 pairs of membranes, each with an effective membrane area of 1 m2. The current density is 3.65 A/dm2 at 620 V with a membrane spacing of about 0.75 mm. A brine concentrate containing about 118 g/1 of chloride can be attained. The overall current efficiency is 73% for Na+ and 85% for Cl". Typically, the membranes are divinylbenzene cross-linked polystyrene with sul-phonic acid, or quaternary ammonium exchange groups the exchange capacity is 1.8 to 2.8 meq/g at 25 °C34). 

Most experiments were performed at laboratory temperature using an Amicon low pressure cell model 40IS with an effective membrane area of 37.4 cm. An operating pressure of 0.3 MPa was used. The initial feed concentration was 1000 ppm. More details can be found in one of our future papers by Vugteveen et al. ( H.) ... 

We can now design a preliminary pilot setup. We use a spiral-type, flowing liquid membrane module, developed by the Teramoto group [87, 88], in which the effective membrane area is about 40% of the total membrane area (the increase of the membrane area is mainly due to blocking of the membrane surface by spacers, and by the adhesive used to seal the sides of the module). For our system, the total feed-side membrane area is 570 m and the total strip-side membrane area is 763 m , in which 360 m is the area needed for the separation of the strip solution concentrated by copper. By designing standard, three-compartment spiral-type BAHLM modules, with 100 m of the membrane on each side (feed and strip), and two-compartment modules, with 200 m of the membrane, we will obtain a setup, of six standard three-compartment modules and one two-compartment module connected in consecutive order (see Fig. 6.7). After the fourth module, we will... 

Membranes were evalu-effective membrane area... 

The operating correnl densities for each stage multiplied by the effective membrane area gives the stack currents for each stage. 

Figure 6.12 Model electrical equivalent circuit to calculate the leakage current in an electrodialyzer. C cation exchange membrane A anion exchange membrane Re electrical resistance of effective membrane area (cell resistance) Rc electrical resistance of channels between compartment of effective membrane area and internal conduits of concentrated and desalting stream (leakage resistance) Rd electrical resistance of conduits in the inlet and outlet of concentrated and desalting stream in the electrodialyzer (channel resistance).

The basic structure of the battery is the same as the electrodialyzer a plurality of a pair of cation and anion exchange membranes is alternately installed to form the concentrated and dilute compartment between electrodes at both ends. Then the concentrated and dilute solutions flow into each compartment and electric power based on the membrane potential is taken out from the electrodes. Various ion exchange membranes have been examined to calculate the energy conversion efficiency.284 A maximum power would be 0.33 Wm-2/pair when 0.57moll-1 solution (concentrated stream) and 0.026 mol l-1 solution (the dilute stream) are fed into a electrodialyzer with 30 pairs of cation and anion exchange membrane (effective membrane area 232 cm2).283 Also, it is calculated to be 0.6 W m-2/pair of electric power in an ideal scale-up based on experimental data when 30 gl-1 and 3 gl-1 solutions flow into the concentrated and dilute compartments.285... 

The performance of the membrane was evahiated by using two criteria (a) permeate flux and (b) component retention. The permeate flux was calculated by measuring the quantity of pameate collected during a certain time and dividing it by the effective membrane area for filtratiotL... 

To improve the delivery, 13-mm-diameter rate-controlling membranes held in a Swinnex filter chamber (Millipore Corp.) were inserted in the delivery line between the insulin reservoir and the micropump. The effective membrane area was 0.7 cm2. Membranes investigated were l- xm and 8- xm pore size polycarbonate filters (Nucle-pore Corp.), 0.45- xm cellulosic microporous filters (Amicon Corp.), Cuprophane PT-150 (from Ultra-Flow 145 Dialyser, Travenol Laboratories), and 0.2- xm and 1.2- xm pore size cellulose acetate filters (Schleicher and Schuell OE 66 and ST 69). 

A Effective membrane area C, Concentration of metal ion in bulk feed at time t Co Initial concentration of metal ion in bulk feed Membrane thickness Thickness of aqueous boundary layer Membrane diffusion coefficient Aqueous diffusion coefficient Aqueous feed film mass transfer coefficient Organic membrane phase mass transfer coefficient Overall mass transfer coefficient Distribution ratio Two-phase extraction constant Aqueous feed mass transfer coefficient Membrane mass transfer coefficient Aqueous strip mass transfer coefficient Length of the fiber Molecular weight of the complex Number of fibers Permeability coefficient (cm/s)... 

A quaternary ammonium salt, tetraoctylammonium bromide (TOABr) and doco-sane were used as solutes and toluene was used as the solvent. The membrane used in this study was again the solvent-resistant polyimide membrane, STAR-MEM 122. A dual-cell crossflow filtration rig, similar to the one described in Section 4.3.1 was used in all the experiments with an effective membrane area of 78 cm. The stage cut was between 0.01 and 0.3% over the whole concentration and pressure range. Ideal mixing is assumed throughout the system. 

A new development in this field is the use of fluidized-bed systems instead of a packed bed. For this purpose, steam reforming of methane has been used as a model reaction [88]. From experimental and theoretical work it can be concluded that fluidized-bed membrane reactors potentially represent a promising system as problems of heat transfer and equilibrium limitations can be addressed simultaneously. As one of the major problems encountered is to provide sufficient membrane area per volume, possible solutions are the use of hollow-fiber systems [13] or membranes based on microsystem technology. In Fig. 5.7 an indication can be obtained for the potential of this approach to enlarge the effective membrane area versus the superficial area of the wafers used [89]. 

The results of their work are given in Table 8.1. A linear relationship was found between the flux and the surface roughness, which was attributed to enlargement of the effective membrane area. 

Mass transfer from bulk to membrane surface is affected by external resistance much more in thin membranes than in thicker ones and, moreover, in the presence of inhibiting species for the membrane, the effective membrane area becomes smaller, thereby causing an additional reduction of the permeating flux. All these phenomena, negative for membrane performances, can cause the validity of Sieverts law (eqn (14.1)) to be compromised because the bulk properties (permeance and permeation driving force) are generally different from those evaluated immediately close to the membrane surfaces ... 

Species that interact more strongly with the metal surface. This type of interaction, which is competitive with that of hydrogen, causes a decrease of the effective membrane area, because of the consequent reduction of the adsorption sites. The species behaving in this way are usually regarded as inhibiting or poisoning species e.g. CO, CO2 or H2S on palladium ). 

Figure 16.4 Oxygen separation from air using inert sweep gases Oxygen flux through a BCFZ hollow fiber membrane as a function of temperature for steam (O) and He (O) as sweep gases (after Tablet et al. ). Experimental details Air flow rate on the core side = 150 mL min steam or He flow rate on the shell side= 10 mL min 0.35 cm effective membrane area. For comparison, different sweep gas flows of 5 ( ) and 20 (A) mL min He.

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