Sorbent capacity

A counter current movement of the mobile phase and the sorbent has some unique advantages when designing separation processes for maximum economy. The efficiency requirement for the sorbent is lower compared to other chromatographic modes, since no individual column has to achieve full resolution. Instead only the pure fractions of the zones obtained are withdrawn from the system. The time-space yield in terms of productivity is enhanced considerably by the improved utilization of the sorbent capacity. The product dilution is lower, pure fractions are withdrawn with high yield and it is not necessary to consider fractions of less then the desired purity. Early on it was re-... 

An example of method development using porous polymers is the work done for n-butyl mercaptan. n-Butyl mercaptan collected on charcoal was found to oxidize readily to the dibutyldisulfide. It was not feasible to analyze for the mercaptan as the disulfide, because the disulfide could also be present in the workplace. Silica gel was an excellent collector for the mercaptan in a dry atmosphere however, at 80% relative humidity the sorbent collected moisture preferentially, and sorbent capacity was severely reduced. 

The sorbents, Chromosorb 102 and XAD-2, which are styrene-divinyl benzene cross-linked porous polymers, proved to be most useful in our studies. Capacity of the sorbent sampling tubes was not a problem with the pesticides we studied since most were not extremely volatile. Sampling humid atmospheres of the pesticides also did not affect the sorbent capacity since these porous polymers are hydrophobic. 

Figures 2 through 4 are graphical representations of the tests performed on the filter/sorbent sampling trains to test for sorbent capacity or breakthrough, and to best determine aerosol/vapor partitioning.

Among these sorbents, only activated carbon is hydrophobia However, water vapor also adsorbs, and it does decrease the sorbent capacity for hydrocarbons quite substantially (Doong and Yang, 1987 Huggahalh and Fair, 1996 Russel and LeVan, 1997). 

Table 18.8 Chlorine content in PVC mixed PP/PE/PS plastic degradation liquid products using Ca-C and theoretical consumed sorbent capacity for each run . (Reproduced with permission from the American Chemical Society)...

One of the key problems with many ion-exchange materials, including the polyamidoxime sorbents used for uranium extraction is encountered in the desorption (elution) stage. With the polyaminodimer, the HCl elution of uranium is usually carried out in two steps. The removal of calcium and magnesium with dilute HCl solution ( 0.01 M) is followed by uranium elution with 0.3-1.0 M HCl [212, 213]. The concentrated efSuent contains tens to hundreds of milligrams of uranium per liter and the removal of uranium reaches 93%. However, the elution with HCl seriously reduces the sorbent capacity [198, p. 213 163, 207, 208], e.g., a six-day treatment of the fibrous amidoxime sorbents with 1 M HCl... 

As seen from Fig. 6, an equilibrium capacity of the fibrous anion exchanger is essentially unaffected with increasing gas flow rate and amount to 0.8 mole of S02/eqv. It is usual that in the adsorption processes, the dynamic sorbent capacity in this case decreases. However, at the rate of 6.0 m/min it remains sufficiently high and is 0.4 mole of S02/eqv. 

Particle-loaded membrane extraction disks, the so-called Empore disks, form an alternative to SPE cartridges [27, 78-79]. With Empore disks, higher sampling flow-rates are possible. They show excellent sorbent capacity. Recoveries at 0.1-pg/l level... 

Sorbent capacity (i.e., how much material is adsorbed per unit quantity of sorbent). The surface area per unit volume of the sorbent has an important influence on this value. For this reason, sorbents are usually highly porous materials. Obviously, one would want the capacity to be as high as possible. 

Sorbent Capacity or Saturation Point. After a certain amount of substance has been adsorbed by the dosimeter the ability of the sorbent to remove vapors from the diffusion space is reduced and the sampling rate begins to decrease. The saturation point for many chemicals can be obtained from the manufacture or determined experimentally in the lab. To determine the saturation point in the lab, the dosimeter is exposed to various doses and the response or sampling rate is plotted against the dose. The point at which an unacceptable deviation in linearity occurs is taken as the saturation point. Fig. 6. Some dosimeters are designed with a backup pad which is placed behind the primary pad to measure the overload and extend capacity. 

The main endogenous factor responsible for the enormous capability to absorb inorganic substances from the environment is a different structure of seaweed cell wall polysaccharides. Each of different seaweed groups possesses various structural polysaccharides such as fibrilar, nonfibrilar, and sulphated derivates with diverse number of bound sites for metal ions resulting in dissimilar mineral sorbent capacity. Structural polysaccharides show strong ion-exchange properties. 

The performance impact of SEWGS vessel size and sorbent capacity are shown in Figure 6.21 and Table 6.4. 

Polyolefins, Polyethylenes, Polyisobutylenes, Poly(Methyl Methacrylates), and Poly(Styrene Sulfonates), In addition to polyurethane foams, polyethylene and polypropylene fibers can be manufactured as alternative polymeric sorbents. However, based on sorbent capacity, cost, and availability, these materials would be considered inferior to polyurethane. 

Evaluation of Sorbent Capacity. The quantity of pollutant that a sorbent can adsorb is defined by the equilibrium isotherm. This is a mathematical relationship between the liquid phase concentration of the spill chemical, Q, and the solid phase concentration of the spill chemical on the sorbent, when the contacting system has reached equilibrium. Figure 15.10 shows this relationship for cadmium salt in solution that has been spilled. 

Reformate from fuel processing can be directly used in aU fuel cells except PEFCs. In PEFC systems, an additional ZnO adsorbent is required at operating temperatures of 350-400 °C. The sorbent capacity for a threshold of 0.1 ppmv H2S is 9mg of S per gram of ZnO at Ippmv H2S in the reformate [31]. For European gasoHne with 10 ppmv S and a ISkWth fuel processor, an adsorbent mass of 1.3 gh operating time is necessary to decrease the sulfur concentration to 0.1 ppmv H2S. 

In the commercial operation of incinerators, activated carbon is used to adsorb both dioxins and Hg. The temperature of adsorption is near 150 °C. Adsorption at higher temperatures would be more economical however, the temperature is limited by the sorbent capacity. By replacing activated carbon with carbon nanotubes, operation at higher temperatures would be possible. 

The catalytic activities of these metal oxides for NO oxidation to NO2 by O2 at ambient temperature were also measured by Huang and Yang (2001). The sorbent capacities were directly dependent on the catalytic activities for NO oxidation. Many surface species were formed upon adsorption. Nitrate and nitrite were the main species, and they also desorbed at the highest temperatures. Desorption began at about 70 °C, and essentially all species were desorbed below 400 °C. 

The required mercury capacities of sorbent as predicted by mass transfer analysis are presented in Table 1. Under a mass transfer limited process, a low capacity sorbent is required. For example for a 5 pm carbon particle size, the mass transfer capacity is only 217 pg/g carbon. When the mercury capacity of a sorbent is comparable to that of the mass transfer capacity, however the C/Hg ratio is determined by both mass transfer parameters and adsorbent capacity. Under some extreme conditions, the mercury capacity of the adsorbent could limit the removal efficiency, and the C/Hg ratio is determined by the sorbent capacity rather than the mass transfer capacities presented in Table 1. 

Zeolites, Activated carbon, Modified activated Alumina Thiophene, Benzene The sorbent capacities for thiophene at the low pressure Cu-Y, Ag-Y Na-ZAM-5 > activated carbon > Na-Y > modified alumina, H-USY. 

Zeolites Thiophene, Benzene, n-Octane The sorbent capacities for thiophene Cu-Y > H-Y > Na-Y > Ag-Y. 

Cu -Y, Ni-based sorbent Commercial gasohne (305 ppmw S) CuQ-Y and Ni-based adsorbent showed the sorbent capacities of 0.22 and 0.37 mg S/g of sorbent at room temperature, respectively. 

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