Fiber extraction

The depressed prices of most metals in world markets in the 1980s and early 1990s have slowed the development of new metal extraction processes, although the search for improved extractants continues. There is a growing interest in the use of extraction for recovery of metals from effluent streams, for example the wastes from pickling plants and electroplating (qv) plants (276). Recovery of metals from Hquid effluent has been reviewed (277), and an AM-MAR concept for metal waste recovery has recentiy been reported (278). Possible appHcations exist in this area for Hquid membrane extraction (88) as weU as conventional extraction. Other schemes proposed for effluent treatment are a wetted fiber extraction process (279) and the use of two-phase aqueous extraction (280). 

Lanka. The fruits are broken by hand or machine, and the fiber extracted from the broken husks from which the coconut has been removed for copra. The husks are retted ia rivers, and the fiber separated by hand beating with sticks or by a decortication machine. The fibers are washed, dried, and hackled, and used ia upholstery, cordage, fabrics, mats, and bmshes. 

RoUer-top cards have five to seven sets of workers and strippers to mix and card the fibers carried on the cylinder. The multiple transferring action and re-introduction of new groupings of fibers to the carding zones provides a doubling effect which enhances web uniformity. Stationary-top cards have strips of metallic clothing mounted on plates positioned concavely around the upper periphery of the cylinder. The additional carding surfaces thus estabhshed provide expanded fiber alignment with minimum fiber extraction. 

The fiber extraction (milling) process must be chosen so as to optimize recovery of the fibers in the ore, while minimizing reduction of fiber length. Since the asbestos fibers have a chemical composition similar to that of the host rock, the separation processes must rely on differences in the physical properties between the fibers and the host rock rather than on differences in their chemical properties (33). 

The instrumentation which until now has been used in chiral extraction experiments is very diverse, ranging from the simple extraction funnel [123, 180], the U-or W-tubes [171, 181], to more sophisticated devices, such as hollow-fiber extraction apparatus [175] or other membrane-assisted systems. Most of these experiments... 

Miranda, et al. Antimicrobial and an- CN080 tiviral activities of polyphenolics from Cocos nucifera Linn. (Palmae) husk fiber extract. Res Microbiol 2002 ... 

S. Naser, R. Fournier, A numerical evaluation of a hollow fiber extractive fermentor process for the production of ethanol, Biotechnology Bioengineering, 32(5), 628-638, 1988... 

The technique was further improved by employing a polymer coating on the polymeric fibers packed in a fused silica capillary. The coating material was based on GC stationary phases. The polymer-coated fiber-packed capillary was used as the sample loop of the LC injection valve for the extraction of phthalate esters from river water and wastewater.22 The coated-fiber extraction capillaries demonstrated a better extraction efficiency and lower limit of quantification (LOQ) than the uncoated-fiber capillaries. Also, the coated fibers were similarly packed in a PEEK tube, which was used as the injection loop or integrated in the rotor of an LC injection valve employed for the extraction of phthalates. The results clearly showed that an extraction with high selectivity could be established with an appropriate type of polymer coating.23... 

After fiber extraction, a slurry containing starch, small fiber particles that were not removed during extraction and some remaining protein is obtained. The goal of the classification step is to free the starch slurry of fiber. This classification is done in a separator centrifuge. Figure 11.16 shows a schematic diagram of this type of separator. 

Fiber extraction-------Starch classification-------Fiber classification------Side line sieving... 

Figure 11.15 Particle size distributions ofthe starch and fiber fractions after fiber extraction.

The goal of sideline extraction is to regain the starch (fine granules) that has been lost in the overflow of the classification. Figure 11.19 indicates that the particle sizes of starch and fiber are sufficiently different to enable separation by sieving. This is done by the same conical rotating sieves that were used in the fiber extraction, but with a... 

H. Hollow-fiber extraction inside fibers Nsh = 0.5NGzMGz[Pg.66]

Ding HB, Carr PW, and Cussler EL, Racemic leucine separation by hollow-fiber extraction, AIChE Journal 1992, 38(10), 1493-1498. 

Ortiz, I., Galan, B., and Irahien, A., Membrane mass transport coefficient for the recovery of Cr(VI) in hollow fiber extraction and back-extraction modules. J. Membr. Sci., 1996, 118 213-221. 

Figure 5.3 Linear relationships between concentrations (mg/L) of some aroma compounds evaluated by GC-FID after XAD-2 enrichment technique in different wines and the relevant ratios of the compounds areas to that of internal standard (2-octanol evaluated on the fragment at m/z 45) determined by GC-MS after HS-SPME (PDMS fiber) extraction (some scores could be hidden)... 

Cotton fibers extracted with 68/32 chloroform/acetone. 

Hollow fiber extractive membrane bioreactors (EMB), have been modelled by Pavasant et al [5.104]. For this purpose the authors employed a diffusion-reaction model for the membrane to describe the dynamic biofilm growth. The wastewater and the biological treatment compartments were considered completely mixed. Pavasant et al [5.104] report... 

Solid-phase micro-extraction (SPME) first became available to analytical researchers in 1989. The technique consists of two steps first, a fused-silica fiber coated with a polymeric stationary phase is exposed to the sample matrix where the analyte partitions between the matrix, and the polymeric phase. In the second step, there is thermal desorption of analytes from the fiber into the carrier gas stream of a heated GC injector, then separation and detection. Headspace (HS) and direct insertion (DI) SPME are the two fiber extraction modes, whereas the GC capillary column mode is referred to as in-tube SPME. The thermal desorption in the GC injector facilitates the use of the SPME technology for thermally stable compounds. Otherwise, the thermally labile analytes can be determined by SPME/LC or SPME/GC (e.g., if an in situ derivatization step in the aqueous medium is performed prior to extraction). Different types of commercially-avarlable fibers are now being used for the more selective determination of different classes of compounds 100 /rm polydimethylsiloxane (PDMS), 30 /rm PDMS, 7 /rm PDMS, 65 /rm carbowax-divinylbenzene (CW-DVB), 85 /rm polyacylate (PA), 65 /rm PDMS-DVB, and 75 /rm carboxen-polydimethyl-siloxane (CX-PDMS). PDMS, which is relatively nonpolar, is used most frequently. Since SPME is an equilibrium extraction rather than an exhaustive extraction technique, it is not possible to obtain 100% recoveries of analytes in samples, nor can it be assessed against total extraction. Method validation may thus include a comparison of the results with those obtained using a reference extraction technique on the same analytes in a similar matrix. 

H. B. Ding, P. W. Carr and E. L. Cussler, Racemic Leucine Separation by Hollow-Fiber Extraction, AIChE J., 38 (1992) 1493. 

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