Surfactant-based ultrafiltration

Surfactant-based ultrafiltration (SBUF) has been investigated since the 1980s for removing dissolved organic compounds, especially hazardous wastewater, as discussed in Chapter 1. The basis of SBUF is that at concentrations above the critical micelle... 

Enormous advances and growth in the use of ordered media (that is, surfactant normal and reversed micelles, surfactant vesicles, and cyclodextrins) have occurred in the past decade, particularly in their chromatographic applications. New techniques developed in this field include micellar liquid chromatography, micellar-enhanced ultrafiltration, micellar electrokinetic capillary chromatography, and extraction of bioproducts with reversed micelles techniques previously developed include cyclodextrins as stationary and mobile-phase components in chromatography. The symposium upon which this book was based was the first major symposium devoted to this topic and was organized to present the current state of the art in this rapidly expanding field. 

Ultrafiltration of whey is a major membrane-based process in the dairy industry however, the commercial availability of this application has been limited by membrane fouling, which has a concomitant influence on the permeation rate. Ultrasound cleaning of these fouled membranes has revealed that the effect of US energy is more significant in the absence of a surfactant, but is less markedly influenced by temperature and transmembrane pressure. The results suggest that US acts primarily by Increasing turbulence within the cleaning solution [91]. 

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. 

Several researchers have investigated the possibilities of membranes for the removal of dispersed water-based ink pigments from wash effluent [121-126]. Generally, membranes, in particular ultrafiltration membranes, have been found to completely remove ink pigments from effluent streams. It has also been observed that the permeate flux and the fouling tendency depend on operational conditions and effluent composition. For instance, coagulation pretreatment [125], feed water acidification [121], and surfactant addition [123] have been found to improve the flux and decrease fouhng. 

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],... 

Liithi and Luisi [44] have used a hoUow fiber membrane reactor for peptide synthesis catalyzed by a-chymotrypsin in microemulsion. Chang et al. [110] described the immobilization of lipase on liposomes, which, in turn, were solubilized in AOT/isooctane reversed micelles and used for the continuous glycerolysis of olive oil in an ultrafiltration cell. The half-Ufe of the Chromo. viscosum lipase was 7 weeks. The development of an ultrafiltration ceramic membrane bioreactor for the simultaneous lipolysis of olive oil and product separation in AOT/isooctane reversed micellar media has been also reported [106,107], Cutinase performance was also evaluated in a ceramic membrane reactor [9]. An attempt to minimize the surfactant contamination problem was based on the use of an electro-ultrafiltration method which can decrease the gel formation in the membrane surface, improving the filtration flux, achieving the separation of the AOT reverse micelles [187],... 

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. 

In a scheme designed to estimate the concentration of biological surfactants in fermentation broth, Lin et al. demonstrated a two-step analysis based on ultrafiltration (1) The aqueous broth is subjected to ultrafiltration using a membrane of 10,000 MW cutoff macromolecules, including micelles, do not permeate this membrane. An HPLC chromatogram with RI or low wavelength UV detection is made of the permeate. (2) The solution is adjusted to contain 50% methanol, breaking up the micelles, and the ultrafiltration and HPLC analysis is repeated. Compounds in the filtrate which were absent or at very low concentration in step 1 are assumed to be surfactants (105). 

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