Recovery from organic liquids

As highlighted above a wide variety of technologies are available for the recovery of organic solvents. The choice of process can be confusing. Table 7.7 is provided as guidance on the appropriate techniques suitable for solvent recovery from gases, liquids and solids. Disposal methods are also listed for completeness. Detailed descriptions of each technology are provided in the text below. 

The recovery of solvents from organic liquids. The principal method for the separation of one or more organic solvents is distillation and is both suitable for the bench and large scale [23]. The basic apparatus used for distillation is a vertical cylindrical column which contains either trays or packings which enhances the contact between vapour and liquid. A continuous process involves introduction of the feed at one or more points in the column. Batch processes consist of a vessel at the base of the column in which the material to be distilled is placed at the beginning of each process. 

Adsorption, which utilizes the ability of a solid adsorbent to adsorb specific components from a gaseous or a liquid solution onto its surface. Examples of adsorption include the use of granular activated carbon for the removal of ben-zene/toluene/xylene mixtures from underground water, the separation of ketones from aqueous wastes of an oil refinery, aad the recovery of organic solvents from the exhaust gases of polymer manufacturing facilities. Other examples include the use of activated alumina to adsorb fluorides and arsenic from metal-finishing emissions. 

If the recovered material is insoluble in the aqueous recovery solution and it is a liquid, you can use your separatory funnel to separate the aqueous recovery solution from your liquid product. Then dry your liquid product and distill it if it is not clean. Or, you might just do a back-extraction as just described. This has the added advantage of getting out the small amount of liquid product that dissolves in the aqueous recovery solution and increases your yield. Remember to dry the back-extracted solution before you remove the organic solvent. Then distill your liquid compound if it is not clean. 

Some potential limitations associated with this protocol merit note. For example, with sequence A in Fig. 1, insoluble by-products will interfere with catalyst recovery. With sequence B, interference will depend upon the type of support. For instance, the Teflon tape in Fig. 8 should be easily separable from another solid material, as would a mesh or reactor liner. Also, since heating is required to achieve homogeneity, the method is best suited for reactions conducted at elevated temperatures. However, there are many reactions which proceed rapidly under fluorous/organic liquid/liquid biphase conditions (i.e., before the miscibility temperature is reached) [55-57,70]. Therefore, it is not unreasonable to expect that sohd fluorous catalysts with little or no solubility can also efficiently promote certain reactions, as represented by sequence A-1 in Fig. 1 [29]. 

Monomer and initiator must be soluble in the liquid and the solvent must have the desired chain-transfer characteristics, boiling point (above the temperature necessary to carry out the polymerization and low enough to allow for ready removal if the polymer is recovered by solvent evaporation). The presence of the solvent assists in heat removal and control (as it also does for suspension and emulsion polymerization systems). Polymer yield per reaction volume is lower than for bulk reactions. Also, solvent recovery and removal (from the polymer) is necessary. Many free radical and ionic polymerizations are carried out utilizing solution polymerization including water-soluble polymers prepared in aqueous solution (namely poly(acrylic acid), polyacrylamide, and poly(A-vinylpyrrolidinone). Polystyrene, poly(methyl methacrylate), poly(vinyl chloride), and polybutadiene are prepared from organic solution polymerizations. 

Pertraction (PT) can be realized through a liquid membrane, but also through a nonporous polymeric membrane that was applied also industrially [10-12]. Apart from various types of SLM and BLM emulsion liquid membranes (ELM) were also widely studied just at the beginning of liquid membrane research. For example, an emulsion of stripping solution in organic phase, stabilized by surfactant, is dispersed in the aqueous feed. The continuous phase of emulsion forms ELM. Emulsion and feed are usually contacted in mixed column or mixer-settlers as in extraction. EML were applied industrially in zinc recovery from waste solution and in several pilot-plant trials [13,14], but the complexity of the process reduced interest in this system. More information on ELM and related processes can be found in refs. [8, 13-16]. 

Mass transfer occurs from the feed films into the stripping solution films through the bulk liquid membrane. Pertraction in RD contactors has been widely studied in the Boyadzhiev group for recovery of organic acids [50-53], antibiotics [54], alkaloids [55-58], biosurfactant [59] and metals [60-64],... 

Blanchard LA, Brennecke JF (2000) Recovery of organic products from ionic liquids using supercritical carbon dioxide. Ind Eng Chem Res 40(l) 287-292... 

Sulfur also is found as sulfide minerals in combination with iron or base metals (e g-, pyrites) and as sulfates in combination with alkali metals and alkaline earths (e.g., gypsum). Hydrogen sulfide, with its rotten egg odor, is the primary sour component of sour gas. Crude oil and coal contain a variety of complex sulfur-containing organic species. These sulfur compounds are removed from the liquid fuels by treatment with hydrogen to convert the sulfur to hydrogen sulfide, which is taken off in the gas stream. The recovery of sulfur from sour fuels for environmental reasons is the largest source of sulfur today. 

Contact Condensers Spray condensers, jet condensers, and barometric condensers all utilize water or some other liquid in direct contact with the vapor to be condensed. The temperature approach between the liquid and the vapor is very small, so tne efficiency of the condenser is high, but large volumes of the liquid are necessary. If the vapor is soluble in the liquid, the system is essentially an absorptive one. If the vapor is not soluble, the system is a true condenser, in which case the temperature of the vapor must be below the dew point. Direct-contact condensers are seldom used for the removal of organic solvent vapors because the condensate will contain an organic-water mixture that must be separated or treated before disposal. They are, however, the most effective method of removing heat from hot gas streams when the recovery of organics is not a consideration. 

Metcalf, J.S., Beattie, K.A., Saker, M.L., and Codd, G.A. 2002. Effects of organic solvents on the high performance liquid chromatographic analysis of the cyanobacterial toxin cylindrospermopsin and its recovery from enviromnental eutrophic waters by solid phase extraction. FEMSMicrobiology Letters 216 159-164. 

The term solid-phase extraction was introduced by personnel of the J. T. Baker Company in 1982. The method consists of retention of the analytes from a liquid or gaseous sample to a solid stationary phase and subsequent removal of analytes using an appropriate eluent. The main purpose of SPE is isolation and preconcentration of compounds of interest or sample clean-up and simplification of the matrix. Application of this sample preparation technique also allows extract fractionation. As a result of significant reduction in the volume of organic solvents used, high recovery, and the possibility of process automation, SPE is a good alternative for conventional liquid-liquid extraction. According to their affinity for the compound of interest, stationary phases are classified as follows ... 

The recovery of iodine from waste liquids.—E. Beilsteini2 recovered iodine from laboratory residues by evaporation to dryness with an excess of sodium carbonate and calcination until the organic matter is all oxidized. The mass is dissolved in sulphuric acid and treated with the nitrous fumes, obtained by treating starch with nitric acid, until all the iodine is precipitated. The iodine is washed in cold water, dried over sulphuric acid, and sublimed. Other oxidizing agents less unpleasant than the nitrous fumes employed by F. Beil stein—e.g. hydrogen peroxide—-were recommended by G. Torossian for the residues obtained in copper titrations. F. Beilstein s process is applicable to soluble but not to insoluble, oxidized forms of ioffine. F. D. Chattaway... 

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