Acetone from water

The selectivity of pervaporation membranes varies considerably and has a critical effect on the overall separation obtained. The range of results that can be obtained for the same solutions and different membranes is illustrated in Figure 41 for the separation of acetone from water using two types of membrane (89). The figure shows the concentration of acetone in the permeate as a function of the concentration in the feed. The two membranes shown have dramatically different properties. The siUcone mbber membrane removes acetone selectively, whereas the cross-linked poly(vinyl alcohol) (PVA) membrane removes water selectively. This difference occurs because siUcone mbber is hydrophobic and mbbery, thus permeates the acetone preferentially. PVA, on the other hand, is hydrophilic and glassy, thus permeates the small hydrophilic water molecules preferentially. 

Example 1 Partition Ratios Let us estimate the partition ratio in weight fractions K for extracting low concentrations of acetone from water into chloroform. The solute is acetone, the feed solvent is water, and the extraction solvent is chloroform in this case. 

Extraction of Acetone from Water Use of the Phase Diagram... 

Estimate the distribution coefficient for transferring acetone from water into benzene at 25° C. The concentration of acetone in benzene is assumed to be dilute. 

Therefore, monopolar solute values vary significantly between different organic liquid/water systems in a predicable way. As shown above, the complementary H-donor functionality of chloroform increases the distribution coefficient of acetone (an H-acceptor) by a factor of 10. Therefore, chloroform would be the better solvent for the extraction of acetone from water. 

Consider for example, the system acetone/water. Acetone is concentrated in the vapor phase at low concentrations, hence stripping of acetone from water is easy. At high concentrations this is not the case. Complete dehydration of acetone is difficult (Fig. 14). 

Figure 4. The isotherms of excess adsorption on silica gel of acetone from water (a), dioxane from water (b) and dioxane from acetone (c).

The distribution coefficient, m, is a measure of the affinity of the solute (A) for one phase (E, S) over the other phase (F, R). The concentration of A may be expressed in various units, but for ease of subsequent calculations, it is preferable to express the concentration on a solute-free basis for both phases. For example, in the extraction of acetone from water with toluene ... 

VI.10 Figure PVI.2 shows a process for the recovery of acetone from an air-acetone mixture. The air-acetone gaseous mixture enters the absorber at the bottom, and as it goes up the column the acetone is absorbed by the falling liquid water. The solution of acetone in water is subsequently preheated, first by the bottom stream of the distillation column and then by steam. Distillation is used to separate acetone from water. 

High Ka to extract acetone from water into MIBK low Ka to extract acetone from MIBK into water. 

Distillation of acetone from water presents no difficulty if very dry acetone is not required, but for a recovered acetone of less than 2% water a considerable reflux ratio is needed and the separation of water becomes progressively more difficult at pressures above atmospheric. 

Because of the ease of stripping acetone from water and the comparative difficulty of producing a dry distillate, acetone is particularly well suited to recovery in a batch still rather than a continuous fractionating column. Typically the numbers of theoretical trays required are as given in Table 16.12. 

From this exanple it is evident that a single extraction stage is sufficient to remove a considerable amount of acetone from water. However, quite a bit of solvent was needed for this operation, the resulting extract phase is not very concentrated, and the raffinate phase is not as dilute as it could be. 

D19. Many extraction systems are partially miscible at high concentrations of solute, but close to immiscible at low solute concentrations. At relatively low solute concentrations both the McCabe-Thiele and trianglar diagram analyses are applicable. This problem explores this. We wish to use chloroform to extract acetone from water. Equilibrium data are given in Table 13-4. Find the number of equilibrium stages required for a countercurrent cascade if we have a feed of 1000.0 kg/h of a 10.0 wt % acetone, 90.0 wt % water mixture. The solvent used is chloroform saturated with water (no acetone). Flow rate of stream Eq = 1371 k. We desire an outlet raffinate concentration of 0.50 wt % acetone. Assume immiscibility and use a weight ratio units graphical analysis. Conpare results with Problem 13.D43. 

Extraction of acetone from water with trichloroethane using cocurrent multiple... 

Pb(ATZ)2 Colorless Precipitated with acetone from water... 

The tests by Seibert et al on 25 and 40IMTP packings using dispersed toluene to extract acetone from water showed the Hql for the 40 size to be 17% greater than the Hql for the 25 size at continuous phase rates greater than 37 ft/h [14]. These investigators also tested a sheet metal... 

Example 8.1 Extraction of Acetone from Water by Methyl Isobutyl Ketone... 

Example 8.3 Extraction of Acetone from Water Using MIBK... 

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