Permeation batch

All parameters required for simulation can be estimated from the diameters of the emulsion drop and internal water droplet. Experimental results for the batch permeation of copper and zinc were satisfactorily predicted by the model. 

Kataoka T, Nishiki T, Kimura S, and Tomioka Y. Batch permeation of metal ions using liquid surfactant membranes. J Membr Sci 1989 46 67-80. 

Batch. Permeation involves the transport of molecules across a membrane phase. The transport process involves either dissolution or adsorption within the substance of the membrane and then transport from regions of higher to lower "potential" (that is, concentration) within the membrane phase. The global measurement of the rate of transport across the membrane, given in terms of the measurable changes in the concentrations in the bulk above and below the membrane, is permeation. Transport within the membrane, described quantitatively in terms of the concentration within it, is diffusion. The processes that take gas phase species from the bulk either to the surface of the membrane or that lead to their dissolution within the near surface region are adsorption and partitioning (dissolution), respectively. 

Consider the following diagram. Figure 1, for a simple system for batch permeation. 

Flux is maximized when the upstream concentration is minimized. For any specific task, therefore, the most efficient (minimum membrane area) configuration is an open-loop system where retentate is returned to the feed tank (Fig. 8). When the objective is concentration (eg, enzyme), a batch system is employed. If the object is to produce a constant stream of uniform-quahty permeate, the system may be operated continuously (eg, electrocoating). 

Constant-volume batch diafiltration is the most efficient process mode. Eor species that freely permeate the membrane. 

In the preparation of commercial DGEBPA, an excess of epichl orohydrin is used in order to minimize polymeriza tion of the reactants to higher molecular-weight species. Nevertheless, the typical viscous final product usually contains ca 80% by weight of the monomeric (n = 0) DGEBPA as deterrnined by gel-permeation chromatography (gpc). The manufacture of Hquid epoxy resins in a batch process has been described in some detail (9). 

Diafiltration If a batch process is run so that the permeate is replaced by an equal volume of fresh solvent, unretained solutes are flushed through the system more efficiently. A major use of UF is fractionation, where a solvent, a retained solute and an unretained solute are present. An example is whey, containing water, protein, and lactose. If the retention of protein is I and the retention of lactose is 0, the concentration of protein in the retentate rises during UF. The ratio of protein to lac tose rises, but the feed concentration of lactose is unchanged in retentate and permeate. Diafiltration dilutes the feed, and permits the concentration of lactose to be reduced. Diafiltration is used to produce high-purity products, and is used to fractionate high-value products. R is always 0 for eveiy component. 

Nonionic surfactants, including EO-PO block copolymers, may be readily separated from anionic surfactants by a simple batch ion exchange method [21] analytical separation of EO-PO copolymers from other nonionic surfactants is possible by thin-layer chromatography (TLC) [22,23] and paper chromatography [24], and EO-PO copolymers may themselves be separated into narrow molecular weight fractions on a preparative scale by gel permeation chromatography (GPC) [25]. 

A flow diagram of a simple cross-flow system is shown in Figure 16.12. This is the system likely to be used for batch processing or development rigs it is in essence a basic pump recirculation loop. The process feed is concentrated by pumping it from the tank and across the membrane in the module at an appropriate velocity. The partly concentrated retentate is recycled into the tank for further processing while the permeate is stored or discarded as required. In cross-flow filtration applications, product washing is frequently necessary and... 

N, and solute passage Si needed to produce desired retentate product with impurity concentrations Cj and retentate product yield Mj/Mjo. Permeate product characteristics for batch operation can be determined by mass balances using a permeate volume of Vp = Vo(l 1/X + N/X), a mass of solute i in the permeate as Mj perme e = Mjo(l — and the permeate concentration as the ratio of the... 

The system area A needed for batch or fed-batch operation can be calculated by using the formulas in Table 20-19 for production rates V(/t based on feed volume Vq and average fluxes during process steps. The final retentate batch volume Vr = Vq/X or permeate batch volume Vp = Vo(l — l/X + N/X) can be used to restate the production rate on other bases. Although experience can be used to estimate solute passage and process fluxes, they should be determined e3q)erimentally for each application. 

Single-Pass TFF Single-pass TFF or NFF operation is typical of water treatment. Low sofids allow high fluxes with high permeate product recovery and low retentate disposal costs. NFF operation is also used for virus retention in small-batch biologicals processing where low NFF fluxes (high areas) are compensated by ease of use, low residence time, and low capital costs. 

Continuous Multicomponent Distillation Column 501 Gas Separation by Membrane Permeation 475 Transport of Heavy Metals in Water and Sediment 565 Residence Time Distribution Studies 381 Nitrification in a Fluidised Bed Reactor 547 Conversion of Nitrobenzene to Aniline 329 Non-Ideal Stirred-Tank Reactor 374 Oscillating Tank Reactor Behaviour 290 Oxidation Reaction in an Aerated Tank 250 Classic Streeter-Phelps Oxygen Sag Curves 569 Auto-Refrigerated Reactor 295 Batch Reactor of Luyben 253 Reversible Reaction with Temperature Effects 305 Reversible Reaction with Variable Heat Capacities 299 Reaction with Integrated Extraction of Inhibitory Product 280... 

A typical extraction manifold is shown in Figure 13.2. The sample is introduced by aspiration or injection into an aqueous carrier that is segmented with an organic solvent and is then transported into a mixing coil where extraction takes place. Phase separation occurs in a membrane phase separator where the organic phase permeates through the Teflon membrane. A portion of one of the phases is led through a flow cell and an on-line detector is used to monitor the analyte content. The back-extraction mode in which the analyte is returned to a suitable aqueous phase is also sometimes used. The fundamentals of liquid liquid extraction for FIA [169,172] and applications of the technique [174 179] have been discussed. Preconcentration factors achieved in FIA (usually 2-5) are considerably smaller than in batch extraction, so FI extraction is used more commonly for the removal of matrix interferences. 

Cabral and coworkers [253] have investigated the batch mode synthesis of a dipeptide acetyl phenylalanine leucinamide (AcPhe-Leu-NH2) catalyzed by a-chymotrypsin in a ceramic ultrafiltration membrane reactor using a TTAB/oc-tanol/heptane reverse micellar system. Separation of the dipeptide was achieved by selective precipitation. Later on the same group successfully synthesized the same dipeptide in the same reactor system in a continuous mode [254] with high yields (70-80%) and recovery (75-90%). The volumetric production was as high as 4.3 mmol peptide/l/day with a purity of 92%. The reactor was operated for seven days continuously without any loss of enzyme activity. Hakoda et al. [255] proposed an electro-ultrafiltration bioreactor for separation of RMs containing enzyme from the product stream. A ceramic membrane module was used to separate AOT-RMs containing lipase from isooctane. Application of an electric field enhanced the ultrafiltration efficiency (flux) and it further improved when the anode and cathode were placed in the permeate and the reten-tate side respectively. 

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