Micellar-enhanced ultrafiltration MEUF

Nonselective membranes can assist enantioselective processes, providing essential nonchiral separation characteristics and thus making a chiral separation based on enantioselectivity outside the membrane technically and economically feasible. For this purpose several configurations can be applied (i) liquid-liquid extraction based on hollow-fiber membrane fractionation (ii) liquid- membrane fractionation and (iii) micellar-enhanced ultrafiltration (MEUF). 

Ultrafiltration of micellar solutions combines the high permeate flows commonly found in ultrafiltration systems with the possibility of removing molecules independent of their size, since micelles can specifically solubilize or bind low molecular weight components. Characteristics of this separation technique, known as micellar-enhanced ultrafiltration (MEUF), are that micelles bind specific compounds and subsequent ultrafiltration separates the surrounding aqueous phase from the micelles [70]. The pore size of the UF membrane must be chosen such, that the micelles are retained but the unbound components can pass the membrane freely. Alternatively, proteins such as BSA have been used in stead of micelles to obtain similar enan-tioselective aggregates [71]. 

Fig. 5-17. Principle of micellar-enhanced ultrafiltration (MEUF). The d-enantiomer of a racemic mixture is preferentially bound to the micelles, which are retained by the membrane. The bulk containing the 1-enantiomer is separated through the membrane [72].

Micellar enhanced ultrafiltration (MEUF) is a recently proposed technique to separate dissolved organic compounds from aqueous streams [256-258]. In this process, surfactant is added to an aqueous stream containing organic solute for forming micelles in order to solubilize the target compound. The subsequent concentration and purification of the target compound is achieved by ultrafiltration by optimizing the process parameters [259-261]. 

Biologically friendly ionic surfactants can be added to the wastewater at concentrations above the threshold value beyond which the surfactants self-assemble to form micelles. The resulting micelles can trap the hydrocarbon wastes since the hydrocarbon solutes prefer the hydrocarbon interior of the micelle over the aqueous environment outside. In addition, ionic wastes in the water adsorb to the polar heads of the surfactants (see Fig. 8.1). The resulting waste-laden micelles can then be removed more easily using ultrafiltration methods. Such a process, known as micellar-enhanced ultrafiltration (MEUF), can be made continuous, scalable, cost effective, and environmentally friendly (through the use of biodegradable surfactants). 

An automated vapor pressure method has been used to obtain highly precise values of the partial pressure of benzene as a function of concentration in aqueous solutions of sodium dodecylsulfate (at 15 to 45 C) and 1-hexadecylpyridinium chloride (at 25 to 45 C). Solubilization isotherms and the dependence of benzene activity on the intramicellar composition are inferred from the measurements and related to probable micellar structures and changes in structure accompanying the solubilization of benzene. Calculations are made to determine the efficiency of micellar-enhanced ultrafiltration (MEUF) as a process for purifying water streams contaminated by benzene,... 

The mobility of solute species in aqueous media and the transfer of these solutes to other phases can be greatly influenced by their association with ordered entities such as surfactant micelles. Thus, the effectiveness of micellar-enhanced ultrafiltration (MEUF) in removing organic (1 -4) and metal ion ( 5, 6)... 

Iqbal, J., Kim, H.-J., Yang, J.-S., Back, S., and Yang, J.-W. 2007. Removal of arsenic from groundwater by micellar-enhanced ultrafiltration (MEUF). Chemosphere, 66 970-6. 

The micellar-enhanced ultrafiltration MEUF technique, based on addition of surfactants and chelating agents to complex and enhance removal of undesirable compounds, show considerable promise in membrane degumming applications. The natural substances such as phospholipids act as surfactants to form large micelles that will be rejected by the membrane. 

The other approach utilizes the surfactants for separation purposes and the possibility of removal of metals in the process of micellar-enhanced ultrafiltration (MEUF) [100-103]. MEUF can be applied to separate the micellar phase using membranes with a pore size smaller than the micellar diameter. In such a process, surfactant is added to an aqueous... 

Jung J, Yang J K, Kim S H and Yang J W (2008), Feasibility of micellar-enhanced ultrafiltration (MEUF) or the heavy metal removal in soil washing effluent . Desalination, 222,202-211. 

Extraction and concentration schemes based on analyte solnbilization in cationic surfactant micelles, such as miceUar-assisted extraction, coacervative extraction (CAE) [6], micellar-enhanced ultrafiltration (MEUF), smd actant-assisted transport of solutes across bquid membranes (LSM), smd actant-mediated solid-phase extractions (MSPEs), and micellar sobd-phase microextractions (MSPMEs), can be cited [3],... 

Colloid-enhanced ultrafiltration (CEUF) is a separation technique based on the use of colloids able to bind multivalent metal ions by electrostatic interactions. The colloidal solution is then filtered under pressure through a UF membrane with a pore size smaller than the size of the colloid, producing a purified water stream (permeate) and a concentrated stream containing almost all of the colloid and metal ions (retentate) (Dunn et al, 1989). CEUF can be distinguished in micellar-enhanced ultrafiltration (MEUF), if the colloidal species is a micelle-forming surfactant, and in polyelectrolyte-enhanced ultrafiltration (PEUF) when the colloidal species is a polyelecrolyte. 

Liu, C.K. Li, C.W. (2005) Combined electrolysis and micellar enhanced ultrafiltration (MEUF) process for metal removal. Separation and Purification Technology, 43 (1), 25-31. 

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