Sorbents activated carbon

In studies of mice, rats, and dogs, diisopropyl methylphosphonate was rapidly absorbed into plasma (Hart 1976). The plasma data indicate that all three species rapidly absorbed diisopropyl methylphosphonate, although the exact rate was species specific. Although no studies were located regarding human absorption, diisopropyl methylphosphonate is also likely to be absorbed rapidly into the plasma of humans. The ability of porous polymeric sorbents, activated carbon, and dialysis to remove diisopropyl methylphosphonate from human plasma has been studied (McPhillips 1983). The grafted butyl-XAD-4 was found to be the most efficient sorbent for the removal of diisopropyl methylphosphonate from human plasma. Hemoperfusion of plasma over synthetic XAD-4 or butyl-XAD-4 sorbent resin was more efficient than dialysis/ultrafiltration for the removal of diisopropyl methylphosphonate from human plasma the smaller surface of the packed resins provided less area to minimize damage to molecular constituents of the plasma. These methods are useful in reducing diisopropyl methylphosphonate concentrations in the plasma. However, since diisopropyl methylphosphonate and its metabolites are not retained by the body, the need for methods to reduce body burden is uncertain. 

Methods for Reducing Toxic Effects. Little information is available regarding reducing the toxic effects of diisopropyl methylphosphonate following exposure. Recommended treatments include general hygienic procedures for rapid decontamination. The ability of porous polymeric sorbents, activated carbon, and dialysis to remove diisopropyl methylphosphonate from human plasma has been studied. However, since diisopropyl methylphosphonate and its metabolites are not retained by the body, the need for methods to reduce body burden is uncertain. 

This chapter discusses the fundamental principles for designing nanoporous adsorbents and recent progress in new sorbent materials. For sorbent design, detail discussion is given on both fundamental interaction forces and the effects of pore size and geometry on adsorption. A summary discussion is made on recent progress on the following types of materials as sorbents activated carbon, activated alumina, silica gel, MCM-41, zeolites, n -complexation sorbents, carbon nano tubes, heteropoly compounds, and pillared clays. 2001 Academic Press. 

The enrichment of organic sulfur compounds has been described on several solid-phase extraction materials, such as bounded silicates, polymers, ion-exchange materials, metal-loaded sorbents, activated carbon, and materials with several adsorption sites. 

Sorbents used in industrial wastewater purification should possess high sorptive capacity, and have developed surface and high kinetic characteristics. They must be available and affordable. Long-term studies confirm that mineral sorbents (activated carbon, metal oxides, waste production), synthetic materials (resins and fibers), and so on can satisfy these requirements [3]. 

The use of carbons as sorbents for preconcentration of pollutants, an application that has much in common with the preceding one, was recently reviewed by Matisova and Skrabakova [23], who investigated the applicability of carbon sorbents (active carbon, graphitized carbon black, molecular sieves, and porous carbon) for preconcentration of organic pollutants in environmental samples and their analysis by GC and HPLC. Another example of an application of carbonaceous materials in which surface chemistry is involved is the reduction of pollutant emissions from aqueous and gaseous media [24]. 

The commercial sorbents (activated carbon, activated alumina, and zeolites) have all been studied for sulfur removal. The zeolites included 5A 13X (Salem, 1994 Salem and Hamid, 1997) various ZSM s, including ZSM-5 and silicalite (Weitkamp et ah, 1991) and ion-exchanged zeolites (Michlmayr, 1980 Vansant et al., 1988). The ion exchange was intended for the exchanged cation to form a bond with the sulfur atom in thiophene. Although some of these sorbents showed... 

Reduction of sorptive gas pressure, (p 0) vacuum technology. Sorbent Activated carbon, zeolites. Cycle period 1 -30 Air separation (N, C ) Recovery of solvents (VOCs) Natural gas cleaning (CH4, HjS) 10-30... 

Reversible thermal regeneration using a) hot air (200 °C < T < 500 °C) or b) water vapor (T < 900 °C), Cycle period 1 h - 8 h Sorbent Activated carbon, zeolites Flue-gas purification Recovery of volatile solvents 20-40 30-60... 

Thermal regeneration including catalytic chemical reactions. Sorbent Activated carbon Cycle periods Id-... Recovery of complex organic compounds from the flue gas or waste water >70... 

Hollow Fiber with Sorbent Walls. A cellulose sorbent and dialy2ing membrane hoUow fiber was reported in 1977 by Enka Glan2stoff AG (41). This hoUow fiber, with an inside diameter of about 300 p.m, has a double-layer waU. The inner waU consists of Cuprophan ceUulose and is very thin, approximately 8 p.m. The outer waU, which is ca 40-p.m thick, consists mainly of sorbent substance bonded by ceUulose. The advantage of such a fiber is that it combines the principles of hemodialysis with those of hemoperfusion. Two such fibers have been made one with activated carbon in the fiber waU, and one with aluminum oxide, which is a phosphate binder (also see Dialysis). 

If the system under consideration involves use of the sorbent for only a single feed step or reuse after uniform regeneration, as in many apphcations with activated carbons and ion exchangers, then one of two paths is often followed at this point to simplify Eq. (16-124) further. The second term on the left-hand side of the equation is often assumed to be negligibly small (usually a good assumption), and time is redefined as... 

Adsorption and Desorption Adsorbents may be used to recover solutes from supercritical fluid extracts for example, activated carbon and polymeric sorbents may be used to recover caffeine from CO9. This approach may be used to improve the selectivity of a supercritical fluid extraction process. SCF extraction may be used to regenerate adsorbents such as activated carbon and to remove contaminants from soil. In many cases the chemisorption is sufficiently strong that regeneration with CO9 is limited, even if the pure solute is quite soluble in CO9. In some cases a cosolvent can be added to the SCF to displace the sorbate from the sorbent. Another approach is to use water at elevated or even supercritical temperatures to facilitate desorption. Many of the principles for desorption are also relevant to extraction of substances from other substrates such as natural products and polymers. 

Characteristics of attrition and adsorption were investigated to remove CO2 in fluidized hed using activated carhon, activated alumina, molecular sieve 5 A and molecular sieve 13X. For every dry sorbent, attrition mainly still occurs in the early stage of fluidization and attrition indexs(AI) of molecular sieve 5A and molecular sieve 13X were higher than those of activated carbon and activated alumina. Percentage loss of adsorption capacity of molecular sieve 5A and molecular 13X were 14.5% and 13.5%, but that of activated carbon and activated alumina were 8.3% and 8.1%, respectively. Overall attrition rate constant (Ka) of activated alumina and activated carbon were lower than other sorbents. 

Therefore, in this study, activated carbon, activated alumina, molecular sieve 5A, and molecular sieve 13X were used as dry sorbents to control carbon dioxide in a fluidized bed. In addition, the attrition and percentage loss of adsorption capacity of the dry sorbents were investigated. 

Fig. 1 shows that minimum fluidization velocities of activated carbon, activated alumina, molecular sieve 5A and molecular sieve 13X are 8.0 cm/s, 8.5 cm/s, 6.2 cm/s and 6.5 cm/s, respectively. Also, theoretical calculation values of minimum fluidization velocity and terminal velocity of each dry sorbent were summarized in Table 1. 

Table 2 summaries overall attrition rate constants (Ka) and physical properties for each dry sorbent. As shown in Table 2, Ka of activated alumina was the lower than any other sorbent, but was similar to activated carbon. However, we used activated carbon as dry sorbent to control CO2 because it is the most cost-effective among others.

PT catalysts are often difficult to separate from the product, while it is also desirable that the catalyst should be reusable or recyclable. Distillation and extraction are the most common separation processes. The main disadvantage of lipophilic quats is their tendency to remain in the organic phase and consequently contaminate the product. Therefore, extraction in water often is not satisfactory. Furthermore, products in the fine chemicals industry often have high boiling points and/or are heat sensitive, which makes separation of the catalyst by distillation impossible. Often the only means to remove the catalyst in these cases is to adsorb it using a high surface area sorbent such as silica, Florisil or active carbon (Sasson, 1997). After filtration, the catalyst can then be recovered by elution. 

For more efficient utilization of MOFs sorbents, several hybrid systems based on MOFs with other solid sorbents have been investigated in the literature. The objective of having hybrid materials is to utilize the synergism between the two sorbents and therefore ultimately improve the overall performance in C02 separation. Moreover, sorbents such as activated carbons, graphenes, and CNTs provide the added feature of high surface area and easily functionalized sites which contribute to the tuning of the final properties of the composite... 

Mechanism of 2,3,7,8-TCDD was not established so far means of specific therapy as to this compound poisoning are not available. Experiments with animals have shown that activated carbon, zeolite (subject to introduction of sorbents immediately after poison), unithiol, Liv-52, carsil, festal, guaranteed survival of 20-50% laboratory rats [6],... 

This is an alternative technique to headspace analysis for the identification and determination of volatile organic compounds in water. The sample is purged with an inert gas for a fixed period of time. Volatile compounds are sparged from the sample and collected on a solid sorbent trap—usually activated carbon. The trap is then rapidly heated and the compounds collected and transferred as a plug under a reversed flow of inert gas to an external gas chromatograph. Chromatographic techniques are then used to quantify and identify sample components. 

The Diffusion Model. The uptake of a solute by a sorbent can be analyzed by a diffusion model, which has been used successfully to model adsorption rates onto activated carbon (74, 75), ion exchangers (72), heterogeneous catalysts (76), and soil columns (77). For the purpose of illustration, we can consider the diffusion of a compound into a spherical sorbent grain under conditions of linear sorption and no exterior mass transfer limitations (73), which is described by... 

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