Adsorption Operations

Adsorption can be carried out by stagewise or continuous-contacting methods. The stagewise operation of adsorption is called contact filtration because the liquid and the solid are contacted in a mixer and then the solid is separated from the solution by filtration. 

Multistage Crosscurrent Adsorption The amount of adsorbent required for the separation of a given amount of solute can be decreased by employing multistage crosscurrent contact, which is usually operated in batch mode, although continuous operation is also possible. The required adsorbent is further decreased by increasing the number of stages. However, it is seldom economical to 

Therefore, from Eqs. (10.28)and (10.29), the relationship for the intermediate concentrations for the minimum total adsorbent can be obtained as 

We are planning to isolate an antibiotic from a fermentation broth (10 L) by using activated carbon. The concentration of the antibiotic is 1.1 x 1CT6 g per g water. Ninety-five percent of the antibiotic in solution needs to be recovered. Absorption studies at the operating condition gave the following result. 

Isotherm Plot Slope Intercept Corr. Coeff. 

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Adsorber Vessel The most frequently used method of fluid-solid contac t for adsorption operations is in cyhndrical, vertical vessels, with... 

These simplified schematles provide an overall view of the types of operations, equipment and eonfigurations typieally employed in adsorption operations. Additional diseussions on these systems ean be found among the referenees cited in Seetion (B) of the suggested readings at the end of this ehapter. 

This equation is a straight line whose slope is 1/n and whose intercept is k at C = 1. Therefore, if straight line will normally be obtained. However, there are occasions, as explained later, when this is not true. The straight and the curved isotherm lines provide valuable information for predicting adsorption operations. 

Physical, thermal, and chemical stability in order to reduce operating costs, solid sorbents must demonstrate stability under flue gas conditions, adsorption operation conditions, and during the multi-cycle adsorption-regeneration process. In particular, stability in the presence of water vapor is essential for the sustainable performance of the solid sorbent. In addition to thermal properties of the solid sorbent, heat capacity and thermal conductivity are also important in heat transfer operations. 

The adsorption operation was conducted by feeding 1 mM phosphate solutions to the conditioned column at SV 10 or 20 h 1, and then 20 BV of water at SV 3 h 1. The elution operation consisted of feeding 0.1 M NaOH solution (80 BV) and then 20 BV of water at a flow rate of SV 3 h1. The regeneration of the column was conducted by feeding 0.5 M sulfuric acid (20 BV) and 20 BV of water at SV 10 h"1. All column effluents including washings in the adsorption and elution operations were collected on a fraction collector, and concentrations of phosphorus and zirconium in each fraction were determined by ICP-AES. Volume of each fraction was 5 BV for the adsorption operation and 4 BV for the elution operation. However, column effluents in regeneration operations were not analyzed. 

All procedures for removal of the arsenate were conducted by the method (ii). Feeding solutions used in the adsorption operation for arsenate were prepared by dissolving Na2HAs047H20 into water, and those used in the arsenite adsorption were prepared by dissolving NaAs02 into water. The pH of these solutions was adjusted with HNO3. 

Since properties of both phosphate and arsenate are very similar each other, the adsorption of phosphate was examined prior to the adsorption of arsenic species. Here, the feeding solution in the adsorption operation was 1 mM phosphate solution of pH3. Table 1 summarizes detailed experimental conditions and column performances during repeated adsorption-elution-regeneration cycles. Since supplied volumes of the feed are not constant (101 - 193 BV), it is not easy to judge the efficiency of the adsorption from total uptake of phosphate. Thus, removal of phosphate until 100 BV is listed at the last column of Table 1 as an index of the column performances. 

Figure 4 shows breakthrough profiles during the adsorption operation of Pb(II) by both FPS-f and FP-f packed columns. Surprisingly, both columns gave flow rate independent breakthrough profiles of Pb(II), although the... 

The SoilTech ATP system is a type of indirectly fired rotary kiln. The system treats soils, sediments, and sludges contaminated with compounds that vaporize at temperatures up to 1100°F (590°C), resulting in treated solids that are free of organics and suitable for on-site backfill. The treatment system uses filtration, oxidation, and adsorption operations to remove contaminants from aqueous condensate. 

This parameter is frequently used in ion-exchange and adsorption operations in fixed-beds and it is frequently called relative volumetric flow rate ... 

Considering most environmental applications, for catalytic as well as for adsorption operations, the gas species to be removed are in such low concentrations (large excess of inerts) that the expansion factor is practically zero and the temperature is nearly constant throughout the reactor volume. 

Diffusion-type models are two-parameter models, involving kt or Ds and La, while BDST models are one-parameter models, involving only 0, as gmax is an experimentally derived parameter. The determination of La requires the whole experimental equilibrium curve, and in case of sigmoidal or other non-Langmiur or Freundlich-type isotherms, these models are unusable. From this point of view, BDST models are more easily applied in adsorption operations, at least as a first approximation. 

In order to increase the recovery of adsorbate by adsorption, and to reduce the amount of adsorbent required to attain a specific recovery, a multistage adsorption operation can be used. In such an operation (as shown in Figure 11.3), a liquid solution is successively contacted at each stage with the adsorbent. In such a scheme, the relationship given by Equation 11.7 can be applied to each stage, with assumptions similar to the single-stage case, and the concentration ofthe adsorbate in the... 

The PSA operation was carried out at 30-1000 and atmospheric pressure by using a N2 carrier gas (60 ml/min). Adsorbates was butanone. Before PSA operation the adsorbents was pretreated at 400-90010 for 2 h in flowing N2. In the adsorption operation, N2 with butanone vapor (27.2 or 5.44 Torr) was passed through a column of the adsorbent (0.3 g for 27.2 Torr and 0.6 g for 5.44 Torr of butanone pressure) until there was almost no further adsorption (2 h). In the desorption operation, pure N2 was passed through the column in a countercurrent way for 2 h instead of evacuation. The concentration of the organic solvent vapor in the effluent gas was always monitored with a TCD detector to obtain breakthrough curves. Amounts of adsorption and desorption were calculated from the breakthrough curves. 

The expanded bed is, in principle, similar to a fluidized bed, a common unit-operation in the chemical industry.3 However, in the expanded-bed method, mixing of the adsorbent material is minimal during the operation, whereas a fluidized bed is turbulent. This means that an expanded bed is more effective for adsorption and elution processes than the fluidized bed. A complete review of all engineering aspects, comparing expanded beds and fluidized beds, can be found in Thommes.4 The expanded-bed adsorption operation is illustrated in Fig. 2. 

Head loss calculations for bed adsorption are therefore the same as those with filtration. Since head loss formulas through beds of solids have already been discussed under filtration, they will not be pursued here. The important point to remember is that for filtration formulas to apply under moving-bed adsorption operations, the superficial velocity should now be considered relative velocity. 

For low-temperature N2 production, Pignet and Schmidt conclude that, since the reaction rate increases with a decrease in ammonia pressure in the ammonia-rich regime, there must be competitive adsorption operating. This effect was more pronounced for NH3/O2 reactants than for NH3/NO reactants. Their equation for the rate of N2 production below 800 °C is ... 

Sircar, S. Myers, A.L. Liquid adsorption operations equilibrium, kinetics, column dynamics and applications. Sep. Sd. Technol. 1986, 21, 535-562. 

The term adsorption operations, as used in this chapter, is intended to refer to all methods of separation that can be carried out with arrangements of apparatus characteristic of adsorption, or appropriate to it. Any separation operation based upon fluid-solid contact is thus somewhat related to adsorption, and the calculation methods developed for adsorption may prove applicable to it. 

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