Extractions stages, determination

Clearly the concept of a stage has no meaning in such a tower. Instead, we deal with differential transfer units, which are a measure of the change in concentration per unit of difference in concentration (recall that the rate of extraction is determined largely by the difference between the actual and the equilibrium concentration of a solute, or driving force ). 

Sekine et al. [27] used a-spectrometry to determine plutonium (and americium) in soil. The chemical recovery of plutonium was 51-99% and averaged 81%, while for americium the recovery was 60-70%. The method is coupled with the liquid-liquid extraction stage, taking about two days less than the ion exchange method a complete analysis takes about one week. 

In the (usually brief) intervals between extraction stages the beds were allowed to stagnate at the appropriate temperature and pressure. Tests on the beds of Thyme and similar materials in which we have varied the stagnation and flow periods over wide ranges have shown that, for these systems, it is the flow time of the C02 which determines the extent of extraction, ie that extraction during the periods of stagnation is negligible for our equipment within the accuracy of our experiments. 

By substitution of known values into this expression, the concentration is found to be 9 X 10 M. Thus, one extraction stage as described decreases the benzoic acid concentration in the effluent to just under one-half the original value. Similarly, by substituting this concentration value and Kp into Eq. 10.36, the concentration of benzoic acid obtained in the benzene extract is found to be 0.04 M, a ratio corresponding to the benzoic acid partition factor between these two liquids. The same equation may also be used to calculate the single-stage extraction parameters for any other solute of interest, provided that Kp for the system is known, or is determined experimentally. 

An extraction process for separating actinide elements (principally uranium, U, and plutonium, Pu) from fission products in an aqueous solution of spent fuel rods is illustrated in Figure 5.31. The extraction solvent is 30% tributyl phosphate (TBP) in kerosene. The most extractable of the fission products are zirconium, niobium and ruthenium. Zirconium, Zr, is used herein to represent the fission products. Determine the number of stages required in the wash section and in the extraction section. Determine the percentage of the Pu in the feed which is recovered in the extract product. V denotes the relative volumetric flowrate. 

Starting with Yg, which is Tj for the first extraction stage, the raffinate Xy in equilibrium is determined from the distribution curve Fig. 6 ... 

The preferred ratio of fresh solvent to feed in the extractive still has not been determined but should be a function of the specific countersolvent used in the initial extraction stage, the number of plates in the distillation section, and the amount of benzene tolerated in the overhead product. We have selected arbitrarily a feed-to-solvent ratio in the E. D. 

The feed of Example 7.2 is extracted three times with pure chloroform at 298 K, using 8 kg/h of solvent in each stage. Determine the flow rates and compositions of the various streams. 

Separation, identification, and quantification Using GC-MS with internal quantification standards that are added as spikes at the extraction stage. If the subsequent GC-MS analyses reveal that accurate determination of PCDDs and PCDFs is not possible owing to the presence of interfering peaks then liquid chromatography separation may be employed. 

Figure 5. McCabe-Thiele plot for the stage determination for Co extraction with solvent 5% PC 88A+2%Cyanex 272, Aqueous feed 30.86g/L Ni, 3.6g/L Co.

To design such a process, the McCabe-Thiele method may be used to determine the number of theoretical separation stages, as examined in Sections 3.3.2-3.3.4 for distillation, absorption (gas scrubbing), and liquid-liquid-extraction. Thus, we obtain the number of theoretical extraction stages of a countercurrent extraction column based on the equilibrium curve (solubility of extract in the solvent for a given content in the solid) and the operating line. The latter depends on the extract content of the solid feed and residue, and on the in- and outlet extract concentration in the solvent The extract content of the feed is fixed, and the value of the residue is specified by the required degree of extraction. The inlet content of the extract in the solvent is also fixed, as either pure solvent is used or the value is specified by separation of the extract from the used solvent after the extraction. Therefore, the only parameter that is left is the outlet concentration of the extract in the solvent, which depends on the ratio of the solvent flow to the feed rate of the solid feedstock (mass balance). 

All extractions and determinations were conducted in triplicate. Data is expressed as meaniS.D. The means were compared by using the one-way analysis of variance (ANOVA) followed by Duncan s multiple range tests. The differences between individual means were deemed to be significant atp< 0.05. A principal component analysis (PCA) was performed in order to discriminate between different maturity stages and irrigation regime on the basis of their fatty acids composition. 

Ulustratitm 10.1 If 100 kg of a solution of acetic acid (C) and water (A) containing 30% acid is to be extracted three times with isopropyl ether (B) at 20 C, using 40 kg of solvent in each stage, determine the quantities and compositions of the various streams. How much solvent would be required if the same final raffinate concentration were to be obtained with one stage ... 

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