Extraction practical examples

Before going on to some practical examples, you might want to know more about where all this washing and extracting is carried out. I ve mentioned that it s a special funnel called a separatory funnel (Fig. 53) and that you can impress your friends by calling it a sep funnel. Here are a few things you should know. 

Here are some practical examples of washings and extractions, covering various types and mixtures and separations and broken down into the four classifications listed above. 

For the two-component, two-phase liquid system, the question arises as to how much of each of the pure liquid components dissolves in the other at equilibrium. Indeed, some pairs of liquids are so soluble in each other that they become completely miscible with each other when mixed at any proportions. Such pairs, for example, are water and 1-propanol or benzene and carbon tetrachloride. Other pairs of liquids are practically insoluble in each other, as, for example, water and carbon tetrachloride. Finally, there are pairs of liquids that are completely miscible at certain temperatures, but not at others. For example, water and triethylamine are miscible below 18°C, but not above. Such pairs of liquids are said to have a critical solution temperature, For some pairs of liquids, there is a lower (LOST), as in the water-tiiethylamine pair, but the more common behavior is for pairs of liquids to have an upper (UCST), (Fig. 2.2) and some may even have a closed mutual solubility loop [3]. Such instances are rare in solvent extraction practice, but have been exploited in some systems, where separations have been affected by changes in the temperature. 

Before a detailed analysis of the chemical reactions that govern the distribution of different solutes in solvent extraction systems, some representative practical examples are presented to Ulnstrate important snbprocesses assnmed to be essential steps in the overall extraction processes. 

Use of reflux is most effective with Type II systems since then essentially pure products on a solvent-free basis can be made. In contrast to distillation, however, extraction with reflux rarely is beneficial, and few if any practical examples are known. A related kind of process employs a second solvent to wash the extract countercurrently. The requirements for this solvent are that it be only slighly soluble in the extract and easily removable from the extract and raffinate. The sulfolane process is of this type it is described, for example, by Treybal (1980) and in more detail by Lo et al. (1983, pp. 541-545). 

Biotech may be gaining importance in the food and nutrition sector, but many nutritional ingredients are still produced by chemical synthesis or via extraction for example, carotenoids are currently most competitively produced by chemical means. For vitamin B2, however, the situation has changed completely in the last five years. The traditional eight-step chemical synthesis has been replaced by one fermentation process. This biotech process, which is also practiced by BASF on a large scale, reduces overall cost by up to 40 percent and the overall environmental impact by 40 percent, as has been shown by detailed life cycle assessments. Similar trends have been described for other bio-based processes, indicating that economic and environmental benefits go hand in hand in today s white biotech practice (EuropaBio and McKinsey Company, 2003, DSM position document, 2004). 

There are In the literature many practical examples of the application of solvent extraction to the separation of short-lived, radionuclides. A number of these are given below. 

Before going on to some practical examples, you might want to know more about where all this washing and extracting is carried out. I ve mentioned... 

Earlier chapters use simplified and binary models to analyze in a very informative manner some fundamentals such as the effect of reflux ratio and feed tray location, and to delineate the differences between absorption/stripping and distillation. Following chapters concentrate on specific areas such as complex distillation, with detailed analyses of various features such as pumparounds and side-strippers, and when they should be used. Also discussed are azeotropic, extractive, and three-phase distillation operations, multi-component liquid-liquid and supercritical extraction, and reactive multistage separation. The applications are clearly explained with many practical examples. 

In this section we therefore introduce the special challenges of automotive sensor testing. First, some specific characteristics of sensing devices with respect to testability for functional parameters are pointed out. Then, conclusions are deduced leading to an optimized approach to test methods suitable for batch fabrication processes (i.e., model-based tests, test functions, test-pattern based tests, parameter extraction methods based on on-wafer tests). Practical examples show the potential of the methodical approach. 

Amine extraction in the Kerr-McGee mill. As a practical example of the use of organic amines to extract uranium from leach liquors, a description will be given of the solvent extraction section of the Kerr-McGee uranium mill, whose leaching section was described in Sec. 8.5 of this chapter [M3, H4]. The solvent extraction plant consists of two similar circuits process conditions approximating those of one circuit are shown in Fig. 5.9. 

PRACTICAL EXAMPLES OF EXTRACTION WITH REFLUX. There are few, if any, practical examples of reflux in the simple manner shown in Fig. 20.14. For systems such as aniline-heptane-methylcyclohexane (Fig. 20.11), the ratio of MCH to heptane in the extract is only modestly greater than in the raffinate, so a great many stages would he needed for high-purity products. Furthermore, the low solubility of both solutes in aniline would mean a very large flow of solvent to be handled. However, a modification of the reflux concept has been applied in several industrial processes for extraetive separation. Enrichment of the extract is accomplished by countercurrent washing with another liquid, chosen so that the small amounts of this liquid that dissolve in the extract can be easily removed. The Sulfolane process for extraction of aromatics is an example of this type. 

COMMERCIAL PROCESS. A practical example of a supercritical fluid extraction process is the decaffeination of coffee. Coffee beans are first soaked in water to make the extraction more selective and then are loaded into an extraction vessel through which supercritical CO2 is circulated to dissolve the caffeine. In a separate scrubbing vessel the caffeine is transferred from the CO2 to water, also at high pressure. Extraction is continued until the caffeine content of the beans, originally... 

Asa practical example of the significance of elevation in chemical processes, consider the steam extraction of essential oils. Low temperatures are preferred to extract oil from plants because of their susceptibility to degradation. Thus, an alternative to vacuum extraction would be to operate at higher elevation. 

A practical example for the behavior of a bitumen B80 (sample 6) during manufacmre is shown in Fig. 4-70 and 4-71. Fig. 4-70 shows the plot of weight loss versus time at three different isothermal temperatures, for virgin material. Fig. 4-71 shows a similar plot for the bitumen after passage through the asphalt mixing plant (extracted sample). 

Another practical example is glucose isomerase. It is connected to 5-HMF, another platform molecule, that has been synthesized using a chemo-enzymatic route [95]. Accordingly, glucose isomerase immobilized on a solid support catalyzed the glucose isomerization into fructose followed by the catalytic dehydration (oxalic acid catalyst) step to the target compound (5-HMF). The reaction was carried out in seawater since high salt concentration enhanced the efficiency of the whole process. 5-HMF product is continuously extracted from the reaction medium into... 

If the source of the polyunsaturated acid is a tissue rather than a pure fat or oil, the total lipid must first be extracted by some method of wet extraction. For example, Holman and Greenberg (1953) employ ethanol, or ethanol-ether, as a solvent, or separate the acid after digestion of the tissue with 30% potassium hydroxide. It is important to protect the sample as much as possible during all stages of preparation, and for this reason the reactions are generally carried out as far as is practicable under nitrogen. After isolation of the lipid mixture, the material is saponified (if this step has not been previously carried out), and the acid is freed, washed, and dried. 

As stated before, electrodes are not standard linear electrical elements. Electrode properties depend on the electrode potential. Especially, in stimulation electrodes, the electrode potential fluctuates over a relatively wide range, thus enhancing the nonlinear characteristics of the electrode-electrolyte interface. However, an approximate electrical model can be helpful in designing the interface circuits to the electrodes, like signal recording or driver circuits. As explained in Chap. 5, impedance spectroscopy is one of the methods to extract the electrode model. In the following this and other methods are explained through practical examples. 

---