Multiple batch extraction

Continuous Extraction. For relatively small DRy values, even multiple batch extraction cannot conveniently or economically be used—too much organic solvent is required. Continuous extraction using volatile solvents can be carried out in an apparatus in which the solvent is distilled from an extract-collection flask, condensed, contacted with the aqueous phase, and returned to the extract collection flask in a continuous fashion. 

As in the case of multiple-batch extraction already discussed, it is possible to relate mathematically the feed concentrations to the final aqueous (or solvent) concentration in an elementary manner via the distribution coefficient, the number of stages and the solvent and aqueous volumes or flow rates. As with multiple-batch extraction, however, it is necessary for both distribution coefficient and flow rates to be constant for the calculation to be valid. 

Analytical techniques to evaluate potential lubricating oil stocks are essential to a refiner s planning program. When sulfuric acid was the sole chemical used to refine burning oils and lubricants, it was a simple matter to carry out acid-treating experiments on a small scale in the laboratory, and results so obtained were quite reliable. With the advent of solvent treating, analytical techniques were developed which consisted of single or multiple-batch laboratory extractions in conjunction with correlations based on plant experience (17). 

This paper addresses the release patterns of heavy metals from cement solidified wastes and examines the import of alkalinity in the waste on metal leaching rates. These studies were done using both multiple batch and column extraction procedures. 

Attempts to increase pyrite removal by increasing the reaction time met with limited success under our standard conditions because reaction of the ferric ion with the coal matrix depleted the ferric ion that was needed for extraction of the pyrite. Thus, for example, increasing the coal reaction time from 2 to 12 hrs only increased pyritic sulfur removal from 60 to 80% for Pittsburgh coal. Similar results were obtained for the other three coals. The only alternatives were to increase the amount of leach solution or to use a continuous or semi-continuous (multiple-batch) reactor. A multiple-batch mode was chosen because it was a simple laboratory procedure and at the same time it could approximate conditions encountered in a commercial plant. A 1-hr-per-batch leach time was used because our 2 hr results indicated that in the early stages of removal the rate begins to decrease after 1 hr, and six leaches (or batches) per run were used to assure that any pyrite that could be removed in a reasonable amount of time was removed. The progress of removal was monitored by analyzing the sulfate content in each spent leach solution elemental sulfur was not removed until all the leaches were completed. Table VII shows pyrite extraction as a function of successive leaches as followed by sulfate analysis of the leach solution. Note that the major portion of pyritic sulfur is removed in the first two leaches or 2 hrs, followed by lesser amounts in... 

Multiple batch tests comprise the leaching of a single sample of material sequentially with fresh leachant, to identify the changes in leaching over time rather than the average rate of release of contaminants as in a single batch test. A low liquid to solid ratio (L/S ratio) such as 0.1 or 0.21/kg generally is used for each extraction in multiple batch tests. The low liquid to solid ratio for each extraction is commonly referred to as a bed volume. This is effectively the minimum L/S ratio necessary to conduct a shake test. 

If larger quantities of the water precursors are used, one must use multiple batches of freshly activated sieves during the dehydration process. If water is detected in the infrared spectrum of the product, then it is necessary to redissolve the solids in dry acetonitrile and repeat the Soxhlet extraction reflux procedure. 

The simplest method of solvent extraction is batch extraction using a separatory funnel. The need to use multiple extractions using limited solvent quantities rather than a single extraction using a large solvent volume is obvious from the concern for artifacts introduced by the extracting solvent (minimize solvent use) and extraction efficiency as evident from the following equation ... 

Identification of dyes on dyed textiles is traditionally carried out by destructive techniques [493], TLC is an outstanding technique for identification of extracted dyestuffs and examination of inks. Figure 4.9 shows HPTLC/SERRS analysis of acridine orange [492], Wright et al. [494] have described a simple and rapid TLC-videodensitometric method for in situ quantification of lower halogenated subsidiary colours (LHSC) in multiple dye samples. The results obtained by this method were compared with those obtained by an indirect TLC-spectrophotometric method and those from HPLC. The total time for the TLC-videodensitometric assay of five standards and four samples applied to each plate was less than 45 min. The method is applicable for use in routine batch-certification analysis. Loger et al. [495,496] have chromatographed 19 basic dyes for PAN fibres on alumina on thin-layer with ethanol-water (5 2) and another 11 dyes on silica gel G with pyridine-water... 

Solid-handling techniqnes are typically physical methods, such as grinding and milling, that rednce solid dosage forms into small particles (i.e., fine powders) to facilitate extraction." Grinding multiple tablets (composite) into a homogeneons pnlverized form (typically 10-20 tablets for assay and >5 tablets for imparity testing) also provides a more representative sample for the batch. 

The main distillation types include atmospheric, vacuum, steam, azeotropic, extractive, and pressure distillation [45]. AU of these distillation methods can be carried out in a batch or continuous marmer with the exception of extractive distillation, which is solely continuous by nature. Gomplex solvent systems often require the use of multiple distillation columns in series to purify certain solvents that are not easily separated. The energy consumption in distillation columns can therefore be quite large because of the continuous operation of condensers and reboilers over extended periods of time. In order to cut down on these costs, both vacuum and steam distillation can be employed ]45]. 

Viewing the procedure from the aspect of solid material in a single-batch vessel, the solid material is subjected to multiple washes of leaner and leaner miscella and is finally extracted with fresh solvent. The solvent, on the other hand, is brought into contact with material of progressively increasing fat content until the solvent finally encounters fresh solid material. From there, the solvent leaves as full miscella. In this way, miscella is brought out of the system at a high oil content. 

Qualitative and quantitative leachables/extract-ables correlations exist for multiple container closure system component batches/lots, and multiple drug product batches/lots. 

In some cases, especially with multiple solutes and complex phase equilibria, it may be useful to perform laboratory batch experiments to simulate a continuous, countercurrent, multistage process. These experiments can be used to test/verify calculation results and determine the correct distribution of components. For additional information, see Treybal, Chap. 9 in Liquid Extraction, 2d ed. (McGraw-Hill, 1963), pp. 359-393, and Baird and Lo, Chap. 17.1 in Handbook of Solvent E raction (Wiley, 1983 Krieger, 1991). 

Specially purified APT (by multiple-step liquid extraction of selected, very pure batches under clean-room conditions) for the production of 4N and 6N tungsten sputter targets shows a much lower impurity content (Table 5.8). 

Manual methods using 1-, 3-, and 6-station manifolds are also available (Fig. 11.4). Using the manifold, up to six extractions can be completed simultaneously and multiple manifolds can be managed by a single operator. Extraction time is dependent on the amount of particulate matter in the sample. Typically drinking waters take approximately 30 min per batch for a 1-L sample. For lake and river water, it is necessary to add Filter Aid 400 in order to keep extraction time from taking hours for a 1-L sample. 

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