Retentate, membrane technology

Membrane extraction offers attractive alternatives to conventional solvent extraction through the use of dialysis or ultrafiltration procedures (41). The choice of the right membrane depends on a number of parameters such as tlie degree of retention of the analyte, flow rate, some environmental characteristics, and tlie analyte recovery. Many early methods used flat, supported membranes, but recent membrane technology has focused on the use of hollow fibers (42-45). Although most membranes are made of inert polymers, undesired adsorption of analytes onto the membrane surface may be observed, especially in dilute solutions and when certain buffer systems are applied. 

Concentrate the CO2 using membrane technology. Distill the retentate to remove the methane. Take the bottoms from the demethanizer and perform an azeotropic distillation to separate CO2 from C2 using a C4 extraction fluid. Treat theazaotrope overhead with a membrane distillation hybrid to remove the CO2. Now combine the various streams as shown in Fig. P-23b. 

Both retentate and permeate from membrane separation techniques have become important starting materials in producing novel products and ingredients from milk of unique functional properties and organoleptic quality. Henning et al. [7] enumerated the current and new applications of membrane technologies in the dairy industry, which include... 

Microfiltration membranes can be used as pretreatment for other membrane technologies and to remove microbes and total suspended sohds (TSS) including fibers and particles. Retention of salts and dissolved organics is negligible, if they are not bound to the suspended sohds. MF can be used for the recovery of coating color pigments. MBRs generally use UF or MF membranes. The materials used in microfiltration are polyvinylidenefluoride (PVDF), polypropylene, polyethylene, polysulfone, polyether suUbne, Teflon, and ceramic materials. 

Koyuncu, I., An advanced treatment of high-strength opium alkaloid processing industry wastewaters with membrane technology Pretreatment, fouling and retention characteristics of membranes. Desalination, 155, 265, 2003. 

M. Nystr6m, S. Butylina, S. Piatt, NF retention and critical flux of small hydro-philic/hydrophobic molecules. Membrane Technology, October 2004, p. 5-8. 

The membrane separation process was initially conducted in degumming vegetable oil and then was adapted for the recovery of carotenoids. Dense polymeric membranes are employed in this system and are very effective in the separatirm of xanthophylls, phospholipids, and chlorophyll, with retention of 80-100 %, producing an oil rich in carotenes [72,73]. This process, however, requires an additional step of hydrolysis or transesterification. Chiu, Coutinho, and Gruigalves examined the membrane technology as an alternative to concentrate carotenoids from crude palm oil in detriment of ethyl esters. A flat sheet polymeric membrane constituted by polyethersulfone was used and obtained a retention rate of 78.5 % [74]. Damoko and Cheryan obtained similar results using nanofiltration with 2.76 MPa and 40 °C in red palm methyl esters [75]. Whereas Tsui and Cheryan combined ultraiiltration with nanofiltration to separate zein and xanthophylls from ethanolic com extract [76]. 

Membrane technology applications today focus considerable interest on the continuous performance of a membrane. It is well known that fouling reduces the flux and changes the retention properties of membranes, which makes the process less economic. Characterization of protein fouling has been reviewed by Chan and Chen [1], Chen et al. [2, 3]. The goal would be a non-fouling process with a steady flux and retention. 

A bench top polysulfone hollow fiber membrane (0.0325m ) with molecular weight cutoff (MWCO) of 30K (A/G Technology Corp., Needham MA) was used (24). UF was run in a total recycle mode at a rate of 1.2 L/min (flow speed of 0.73 m/sec), cross membrane pressure of 25 PSIG and 10 + 1°C. PE permeability is expressed as the fraction of PEU/mL in the permeate to PEU/mL in the retentate. Data presented are representative of at least duplicate replications. 

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