Questions and Answers of Separation Process Principles Chemical

What is meant by regeneration?
In Example 15.6, pure-component, liquid-phase adsorption data are used with the extended-Langmuir isotherm to predict a binarysolute data point. Use the mixture data below to obtain the best fit to
Why is it easy to measure the amount of adsorption of a pure gas, but difficult to measure adsorption of a pure liquid?
Lewis, Gilliland, Chertow, and Hoffman [J. Am. Chem. Soc., 72, 1153–1157 (1950)] measured adsorption equilibria for propane, propylene, and binary mixtures thereof on activated carbon and silica
What is the BET equation used for? Does it assume physical or chemical adsorption? Does it assume monomolecular- or multimolecular-layer adsorption?
How is it possible to use a liquid sorbent in chromatography?
What is meant by loading in adsorption?
Sircar and Myers [J. Phys. Chem., 74, 2828–2835 (1970)] measured liquid-phase adsorption at 30°C for a binary mixture of cyclohexane(1) And ethyl alcohol (2) On activated carbon. Assuming no
Silver ion in methanol was exchanged with sodium ion using Dowex 50 cross-linked with 8% divinylbenzene by Gable and Stroebel [J. Phys. Chem., 60, 513–517 (1956)]. The molar selectivity coefficient
What is an adsorption isotherm? How can the heat of adsorption be determined from a series of isotherms?
What are the four steps that occur during the adsorption of a solute from a gas or liquid mixture? How do they affect adsorptive bandwidth, resolution, and throughput? Which step may be almost
Ion exclusion is a process that uses ion-exchange resins to separate nonionic organic compounds from ionic species contained in a polar solvent, usually water. The resin is presaturated with the same
Within a porous particle, why are mass and heat transfer not analogous?
For mass transfer outside a single spherical particle that is not close to a wall or other particles, what is the smallest value of the Sherwood number? What is the basis for this value?
Derive (15-44) and use it to solve the following problem. Sulfate ion is to be removed from 60 L of water by exchanging it with chloride ion on 1 L of a strong-base resin with relative molar
What is the difference between slurry adsorption (contact filtration) and fixed-bed adsorption (percolation)? When should each be considered and not considered?
How do pressure-swing and thermal-swing adsorption differ? What are inert-purge swing and displacement purge?
What is a mass-transfer zone (MTZ) and what causes it? Is it desirable? If not, why not?
For fixed-bed adsorption, what is the difference between superficial velocity, interstitial velocity, and concentration wave velocity? Which is the largest and which is the smallest?
For the conditions of Example 15.8, estimate the effective diffusivity of acetone vapor in the pores of activated carbon whose properties are: ρp = 0.85 g/cm3, ϵp = 0:48, average dp = 25 A
What is the difference between a true-moving-bed (TMB) system and a simulated-moving-bed (SMB) system?
How is port switching used in an SMB system?
Using data in Exercise 15.17, estimate the effective diffusivity of water vapor in the pores of activated alumina with the following properties: ρp = 1.38 g/cm3, ϵp = 0:52, average
In chromatography, what causes different solutes to pass through the chromatograph with different residence times?
The volume-average adsorbate loading of a spherical particle is given by (15-49). Show that a parabolic adsorbate loading profile proposed by Liaw, C.H. et al. [AIChE J., 25, 376–381 (1979)], q =
What are the differences among native gel electrophoresis, SDS-PAGE, isoelectric focusing, is otachophoresis, 2-D gel electrophoresis, and pulsed-field gel electrophoresis in terms of denaturants
Cytochrome C(ϵ*p = 0:38) and ovalbumin (ϵ*p = 0:34) in an equimolar mixture are to be purified by size exclusion to a resolution of R = 1.0 in a packed bed of Toyopearl1 (TSK gel) HW55F, which has
In electrophoresis, describe factors that affect mobility, electro-osmosis, and convective Joule heating, and their effects on electrophoretic resolution.
A 50 mg/mL aqueous solution of bovine hemoglobin is to be purified by size-exclusion chromatography using a 75 x 2.5 cm i.d. glass column packed with 75 μm (diameter) Toyopearl HW65C. Intraparticle
Compare the advantages and disadvantages of chromatographic purification of proteins bovine serum albumin, cytochrome C, and ovalbumin by size-exclusion, reversed-phase, hydrophobic-interaction,
What are dispersion, residence time, variance, and plate height in zone electrophoresis relative to pulse linear differential chromatography?
Adsorption with activated carbon, made from bituminous coal of soluble organic compounds (SOCs), to purify surface and groundwater is a proven technology, as discussed by Stenzel [Chem. Eng. Prog.,
Adeno-associated virus is a candidate viral vector for gene therapy. Estimate the static binding capacity of 20-nm adeno-associated virus on 15 mm ResourceTM ion-exchange resin. Compare the estimate
Repeat Exercise 15.26 for water containing 0.324 mg/L of benzene (B) and 0.630 mg/L of m-xylene (X). Adsorption isotherms at 25°C for these low concentrations are independent and given byThe SOC
Repeat Exercise 15.26 for water containing 0.223 mg/L chloroform whose concentration is to be reduced to 0.010 mg/L. The adsorption isotherm at 25C is given byData From Exercise 15.26Adsorption with
Determine the field gradient required to separate two polypeptides (D = 5 x 10-6 cm2/s), with respective pI values of 4.2 and 4.8, using IEF with a linear field gradient of 0.3/cm. Use a
Determine the number of pulses of equal duration that would be required to separate DNA strands of length 125 kbp and 250 kbp, respectively, by 1 mm, using PFGE. The electric field gradient in PFGE
Why is pretreatment of the solids to be leached often necessary?
CaCO3 precipitate can be produced by reaction of an aqueous solution of Na2CO3 and CaO, the byproduct being NaOH. Following decantation, slurry leaving the precipitation tank is 5 wt% CaCO3, 0.1
What is ideal fixed-bed adsorption? What assumptions are necessary for it to apply? What is meant by the stoichiometric front? What is meant by breakthrough?
A 55 mol% propane and 45 mol% propylene gas mixture is to be separated into products containing 10 and 90 mol% propane by adsorption in a continuous, countercurrent system operating at 25°C and 1
In Examples 15.13 and 15.18, benzene is adsorbed from air at 70οF in a 6-ft-high bed of silica gel and then stripped with air at 145°F. If the bed height is changed to 30 ft, the following data are
Repeat Example 15.24, except for a feed containing 400 ppm (by weight) of CaCl2 and 50 ppm of NaCl.Example 15.24Hard water containing 500 ppm (by weight) MgCO3 and 50 ppm NaCl is to be
An aqueous solution, buffered to a pH of 3.4 by sodium citrate and containing 20 mol/m3 each of glutamic acid, glycine, and valine, is separated in a chromatographic column packed with Dowex 50W-X8
Repeat Exercise 15.41 using Carta’s equation to account for mass transfer with the following effective diffusivities:Assume kc = 1.5 x 10-3 cm/s. Establish a cycle of feed pulses and
A dilute feed of 3-phenyl-1-propanol (A) and 2-phenyl ethanol (B) in a 60/40 wt% ratio methanol–water mixture is to be fed to a four-section laboratory SMB to separate A from B. The feed rate is
In the steady-state TMB run of Example 15.22, results for Example 15.21, from application of the steady-state, local-equilibrium TMB model, were used with a β of 1.05 to establish flow rates of the
Estimate the %T, %C, and voltage gradient required to completely resolve protein BSA (Uel = 1.04 x 10-5 cm2/V-s) from antibody IgG (Uel = 1.02 x 10-5 cm2/V-s) on a 20-cm polyacrylamide slab
Is leaching synonymous with solid–liquid and/or liquid– solid extraction?
In a leaching operation, what is the leachant, the overflow, and the underflow?
BaCO3, which is water insoluble, is to be made by precipitation from a solution containing 120,000 kg/day of water and 40,000 kg/day of BaS, with a stoichiometric amount of solid Na2CO3. The
Titanium dioxide, the most common white pigment in paint, can be produced from the titanium mineral rutile by chlorination to TiCl4, followed by oxidation to TiO2. To purify insoluble TiO2, it is
Why does the underflow consist of both leached solids and liquid containing leached material?
Zn is to be recovered from an ore containing ZnS. The ore is first roasted with oxygen to produce ZnO, which is leached with aqueous H2SO4 to produce water-soluble ZnSO4 and an insoluble, worthless
Under what conditions would leaching be expected to be very slow?
Fifty thousand kg/h of flaked soybeans, containing 20 wt% oil, is leached of oil with the same flow rate of n-hexane in a countercurrent- flow system consisting of an ideal leaching stage and three
Data of Othmer and Agarwal [1] for the batch extraction of oil from soybeans by oil-free n-hexane at 80°F are as follows:Determine whether these data are consistent with a constant effective
Sucrose in ground coffee particles of an average diameter of 2 mm is to be extracted with water in a continuous, countercurrent extractor at 25°C. Diffusivity of sucrose in the particles has been
What is dissolution?
Na2CO3 and the balance insoluble solids is to be leached and washed with water in a continuous, countercurrent system. Assume leaching will be completed in one ideal stage. It is desired to obtain a
What is the difference between suspension leaching and percolation leaching? For what conditions is each method used?
What are the advantages of the espresso machine over the drip method?
For the conditions of Example 16.8, determine the effect on leaching time of particle sizes from 0.5 mm to 50 mm.Example 16.8A copper ore containing 2 wt% CuO is to be leached with 0.5-M H2SO4.
Why do many leaching processes include multistage, countercurrent washing after the leaching stage?
What are the assumptions for an ideal leaching or washing stage?
What is meant by variable underflow and what causes it?
Why is an effective diffusivity that is obtained by experiment preferred for estimating the rate of leaching of food materials?
What is the pseudo-steady-state assumption used in the shrinking-core leaching model?
Repeat part (a) of Exercise 14.10 for a two-stage stripping cascade and a two-stage enriching cascade, as shown in Figure 14.14. However, select just one set of reasonable cuts for the two stages of
Can a near-perfect separation be made with gas permeation? If not, why not?
Plant capacity for the methanol–water distillation of Exercise 7.41 is to be doubled. Rather than installing a second, identical rayed tower, a packed column is being considered. This would have a
Liquids A and B, which have nearly identical boiling points, are to be separated by liquid–liquid extraction with solvent C. The following data represent the phase equilibrium at 95οC.Determine
When should batch distillation be considered?
A three-theoretical-stage batch stripper (one stage is the boiler) is charged to the feed tank (see Figure 13.8) with 100 kmol of 10 mol% n-hexane in n-octane mix. The boilup rate is 30 kmol/h.If a
Develop a procedure similar to that of §13.3 to calculate a complex, binary, batch-distillation operation using the equipment arrangement of Figure 13.9. Ø Main cut 1 Off cut Main cut 2 Feed
One hundred lbmol of 10 mol% propane, 30 mol% n-butane, 10 mol% n-pentane, and the balance n-hexane is to be separated in a batch rectifier equipped with a still-pot, a total condenser with a liquid
One hundred lbmol of benzene (B), monochlorobenzene (MCB), and o-dichlorobenzene (DCB) is distilled in a batch rectifier that has a total condenser, a column with 10 theoretical stages, and a
For a batch rectifier with appreciable column holdup: (a) Why is the charge to the still-pot higher in the light component than at the start of rectification, assuming that total-reflux
For a batch rectifier with appreciable column holdup, why do tray compositions change less rapidly than they do for a rectifier with negligible column holdup, and why is the separation improved?
A charge of 100 kmol of an equimolar mixture of A, B, and C, with aA;B = 2 and aA;C = 4, is distilled in a batch rectifier containing four theoretical stages, including the still-pot. If holdup can
A charge of 200 kmol of a mixture of 40 mol% A, 50 mol% B, and 10 mol% C, with aA;C = 2:0 and aB;C = 1:5, is to be separated in a batch rectifier with three theoretical stages, including the still
A charge of 100 lbmol of 35 mol% n-hexane, 35 mol% nheptane, and 30 mol% n-octane is to be distilled at 1 atm in a batch rectifier, consisting of a still-pot, a column, and a total condenser, at a
One hundred kmol of 30 mol% methanol, 30 mol% ethanol, and 40 mol% n-propanol is charged at 120 kPa to a batch rectifier consisting of a still-pot, a column with the equivalent of 10 equilibrium
Repeat Exercise 13.29 with the following modifications: Add a third operating step. For all three steps, use the same distillate rate and reflux rate as in Exercise 13.29. Use the following durations
One hundred kmol of 45 mol% acetone, 30 mol% chloroform, and 25 mol% benzene is charged at 101.3 kPa to a batch rectifier consisting of a still-pot, a column containing the equivalent of 10
Using a process simulator, make the following modifications to the C6–C7–C8 example in §13.7: (a) Increase the reflux above 8 to eliminate the second intermediate cut. (b) Change the
A hollow-fiber module has 4,000 ft2 of membrane surface area based on the size of the fibers, which are 42 mm i.d. x 85 mm o.d. x1.2 m long each. Determine the: (a) Number of hollow fibers in
What are the two products from a membrane separation called? What is a sweep?
What kinds of materials are membranes made from? Can a membrane be porous or nonporous? What forms pores in polymer membranes?
For the commercial application of membrane separators discussed at the beginning of this chapter, calculate the permeabilities of hydrogen and methane in barrer units.
What is the basic equation for computing the rate of mass transfer through a membrane? Explain each of the four factors in the equation and how they can be exploited to obtain high rates of mass
What is the difference between permeability and permeance? How are they analogous to diffusivity and the mass-transfer coefficient?
For a membrane separation, is it usually possible to achieve both a high permeability and a large separation factor?
A spiral-wound module made from a flat sheet of membrane material is 0.3 m in diameter and 3 m long. If the packing density (membrane surface area/unit module volume) is 500 m2/m3, what is the
A mixture of 60 mol% propylene and 40 mol% propane at a flow rate of 100 lbmol/h and at 25°C and 300 psia is to be separated with a polyvinyltrimethylsilane polymer (see Table 14.10 for
What are the three mechanisms for mass transfer through a porous membrane? Which are the best mechanisms for making a separation? Why?
What is the mechanism for mass transfer through a dense (nonporous) membrane? Why is it called solution-diffusion? Does this mechanism work if the polymer is completely crystalline? Explain.
Water at 70°C is passed through a polyethylene membrane of 25% porosity with an average pore diameter of 0.3 μm and an average tortuosity of 1.3. The pressures on the downstream and upstream sides
How do the solution-diffusion equations differ for liquid transport and gas transport? How is Henry’s law used for solution-diffusion for gas transport? Why are the film resistances to mass
What are the four idealized flow patterns in membrane modules? Which is the most effective? Which is the most difficult to calculate?

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