Synthetic polymeric adsorbents

Synthetic polymeric adsorbents have a high porosity, large surface area, and an inert hydrophobic surface. These resins can be regenerated ... 

Kennedy, D.C. Treatment of effluent from manufacture of chlorinated pesticides with a synthetic, polymeric adsorbent, Amberlite XAD-4. Environ. Sci. Technol. 1973, 7 (2), 138-141. 

The dark-colored clarified liquor is presure-filtered and concentrated to 60 percent solids in multiple-effect evaporators. The concentrated liquor is decolorized with granular carbon in columns 12 ft in diameter and 30 ft high in a countercurrent manner that is, liquor flows upward in the columns, while a portion of the carbon is removed from the bottom periodically. Carbon is used at a rate of 2.5 percent of dry solid processed, and approximately 5 percent of carbon is lost during revivification.91 In some cases, granular carbon has been replaced by synthetic polymeric adsorbents to decolorize the syrup. Low ash syrups usually are deionized with ion-exchange resins. The processed liquor is evaporated to a final solids content of 75-85 percent in a single-effect evaporator. 

Synthetic polymeric adsorbants. D.H. Clarke details the use of polyurethane based forms which can absorb and subsequently desorb a range of volatile organic solvents such as chlorinated and aromatic hydrocarbons, or aliphatic ketones [20]. The precise composition of polyurethane foam has a profound effect on absorption performance. However providing the correct reaction and balance between specific isocyante... 

The most common methods for trapping pesticide vapors from air use adsorbents. Common air sampling adsorbents include charcoal (derived from petroleum or coconut) and synthetic polymeric materials, such as cross-linked polystyrene and open-cell polyurethane foam. Charcoal has been used for the cumulative sampling of volatile... 

Copolymers of styrene-divinylbenzene are the classical polymeric adsorbents, manufactured for producing synthetic ion exchangers. These types of materials are discussed in more in detail in Section 3.2.4. 

The fact that poloxamers and proteins were excellent steric stabilizers for double emulsions encouraged scientists to try and design an optimal synthetic polymeric emulsifier to be adsorbed both at the internal and the external interfaces. However, only few commercial polymeric surfactants are available, many of which are designed for... 

Slynihetic polymeric adsorbents [95]. These are porous spherical beads, O.S mm diameter, each bead a collection of microspheres, 10 mm diameter. The material is synthetic, made from polymerizable monomers of two major types. Those made from unsaturated aromatics such as styrene and divinylbenzene are useful for adsorbing nonpolar organics from aqueous solution. Those made from acrylic esters are suitable for more polar solutes. They are used principally for treating water solutions and are regenerated by leaching with low-molecular-wei t alcohols or ketones. 

The eluent compatibility of a polymeric adsorbent will be dependent upon the chemical structure of the polymer backbone, chemical type of the cross-linking agent, degree of cross-linking, and any subsequent covalent or dynamic modifications carried out. The natural polysaccharide polymers in their native state are hydrophilic and are therefore compatible with aqueous eluents whereas the synthetic polymers can be hydrophobic, as in the case of polystyrene, and hence compatible with organic eluents, or hydrophilic, as in the case of polyacrylamide, and so be compatible with aqueous mobile phases. It is of course possible to modify the eluent compatibility of a polymeric matrix by surface coating or derivatisation. For example, the very hydrophobic maeroporous polystyrene matrices may be coated with a hydrophilic polymer to make ion exchange adsorbents or materials suitable for aqueous size separations [25]. 

Most synthetic latices contain 5—10 wt % of nonelastomeric components, of which more than half is an emulsifier or mixture of emulsifiers. One reason for this relatively high emulsifier concentration as compared with natural latex is that emulsifier micelles containing solubiHzed monomer play a principle role in the polymerization process. A high emulsifier concentration is usually necessary to achieve a sufficiently rapid rate of polymerization. Secondly, a considerable fraction of the surface of the polymer particles must be covered by adsorbed soap or equivalent stabilizer to prevent flocculation... 

The concept of adsorption potential comes from work with high-purity, synthetic microporous carbon, which relies solely on van der Waals dispersive and electrostatic forces to provide the energy for adsorption. The polymeric microporous adsorbents that operate solely through van der Waals dispersive and electrostatic forces often cannot provide the surface potential energy needed to trap compounds that are gases under ambient conditions, and for very volatile compounds the trapping efficiency can be low for similar reasons. 

Ambersorb carbonaceous adsorbents (Rohm and Haas Company) are a new class of synthetic adsorbents which show interesting collection properties (37,38). The chemical composition is intermediate between that of activated carbon and polymeric sorbents. Ambersorb sorbents are available in various pore sizes and surface areas. 

The potential impurities for the synthetic polymers are enormous. The amounts can vary from substantial for those impurities associated with the polymerization process to negligible for some components adsorbed from the atmosphere. 

Amberlite XAD Resins. Amberlite XAD resins are synthetic adsorbents structurally composed of a styrene-divinylbenzene copolymer. Because of the polymeric production process, users are cautioned that these resins do contain significant quantities of preservatives and monomers as received from the manufacturer, Rohm and Haas (3,4). 

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