Polymeric resin adsorbents

Polymeric cation-exchange resins are also used in the separation of fmctose from glucose. The UOP Sarex process has employed both 2eohtic and polymeric resin adsorbents for the production of high fmctose com symp (HFCS). The operating characteristics of these two adsorbents are substantially different and have been compared in terms of fundamental characteristics such as capacity, selectivity, and adsorption kinetics (51). 

Adsorbent Life. Long term stability under rugged operating conditions is an important characteristic of an adsorbent. By their nature 2eohtes are not stable in an aqueous environment and must be specially formulated to enhance their stabiUty in order to obtain several years of service. Polymeric resins do not suffer from dissolution problems. However, they are prone to chemical attack (52). 

Gaseous and particulate pollutants are withdrawn isoldnetically from an emission source and collected in a multicomponent sampling train. Principal components of the train include a high-efficiency glass- or quartz-fiber filter and a packed bed of porous polymeric adsorbent resin (typically XAD-2 or polyurethane foam for PCBs). The filter is used to collect organic-laden particulate materials and the porous polymeric resin to adsorb semivolatile organic species (com-... 

SPATT Adsorbent polymeric resin Membranes made of porous materials Polar phytotoxins Integrative 1 week Solvent extraction 72... 

On the synthetic route to a novel class of orally active 2,3-benzodiazepines, scientists at Lilly have described a yeast reduction using Zygosaccharomyces rouxii (ATCC 14462) (Scheme 19.5).76-78 This intermediate is used in the synthesis of a novel class of benzodiazepines such as LY-300164 (1). The choice of this yeast strain came from a screen of numerous microbes. The product was isolated in >95% yield and >99.9% ee by use of an adsorbant polymeric resin.76-78... 

To remove the feedback regulation mechanism and to avoid product degradation various adsorbents have been used for the in situ separation of plant cell cultures as shown in Table 1. In situ removal with polymeric adsorbents stimulated anthraquinone production more than the adsorbent-free control in Cinchona ledgeriana cells [35]. It was found that nonionic polymeric resins such as Amberlite XAD-2 and XAD-4 without specific functional groups are suitable for the adsorption of plant metabolite [36]. The use of the natural polymeric resin XAD-4 for the recovery of indole alkaloids showed that this resin could concentrate the alkaloids ajmalicine by two orders of magnitude over solvent extraction [37] but the adsorption by this resin proved to be relatively nonspecific. A more specific selectivity would be beneficial because plant cells produce a large number of biosynthetically related products and the purification of a several chemically similar solutes mixture is difficult [16]. 

Adsorption of enzymes to various polymeric resins is a straightforward means for immobilization. Zwitterionic molecules such as proteins can bind to both anionic and cationic ion exchange resins. Hydrophobic macroporous resins are also useful for immobilizing many enzymes, particularly lipases. For example, an immobilized form of Candida antarctica lipase B (CAL-B) on acrylic resin has been sold for many years under the name, Novozym 435 (N435). The enzyme is produced in a modified Aspergillus organism by submerged fermentation and is subsequently adsorbed onto a macroporous... 

A quantitative jump was finally brought by a two-in-one resin-based in situ substrate feeding product removal method (SFPR) [104]. An adsorbent polymeric resin acts simultaneously as a reservoir for the substrate and as a trap for the product (Figure 21.5). The substrate, preloaded onto the resin, slowly diffuses into the broth and is hansformed by cells while the formed product is readsorbed onto the soUd. The system is conveniently tuned by a simple choice of substrate resin ratio. Thus, both the substrate and product concentrations are controlled in order to maintain them below their inhibitory or toxic levels and allow a higher productivity. Additional benefits are also to be considered for prachcal large-scale applica-... 

Regeneration efficiency of the polymeric resin or the desorption efficiency of the adsorbate, Rj%, can be found out according to equation (2). Where q (g/g) was initial amount adsorbed of the adsorbate on the resin before regeneration, and qi (g/g) was transient amount adsorbed of the adsorbate on the resin. 

Figures 1 3 showed the comparison between the microwave and thermal regeneration. It can be seen that the application of microwave to regenerate the polymeric adsorbents can get higher regeneration efficiency than the application of the thermal regeneration method. For three kinds of the polymeric resins that had adsorbed benzene, the regeneration efficiency obtained by using microwave was up to 90%, while the regeneration efficiency obtained by using microwave was merely about 60-70%.

A recently developed variation on these polymeric resins is the carbonaceous adsorbents. They are composed of hard, black, nondusting beads whose chemical composition is between that of activated carbon and polymeric adsorbents. 

Several simulation runs were carried out to gain insight into the effect of bead design parameters on the adsorption characteristics of immobilized adsorbent beads. The physical parameters (rate constant, diffusivity etc.) for the simulation studies were determined from experimental data on the adsorption of cycloheximide, a low molecular weight antibiotic, onto XAD-4 non-ionic polymeric resin (10.11) (Table I). The fit between the model and the experimentally determined adsorption curves is quite good (Figure 3). 

Polymeric resins have several advantages over the commonly used silica-gel based reverse phase materials. The cost of polystyrene-based resins is considerably less than bonded phase silica gel adsorbents. Also, the potential... 

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