Extractions solvents

Extraction - making a cup of coffee involves extraction of the flavour chemicals and caffeine from the insoluble vegetable matter using hot water and is an example of liquid-solid extraction. 

This technique separates the components of chemical mixtures by using the dissimilar solubility properties of the components of the mixture in different solvents. Extraction is used mainly to purify a reaction product partially before final purification by recrystallization (p. 92) or distillation (p. 107). The two common types of extraction process used in the laboratory are  

Liquid-liquid extraction this uses two immiscible solvents the desired compound in solution or suspension in one solvent is extracted into the other solvent. For example, covalent organic compounds are extracted from aqueous solution into dichloromethane, leaving the ionic byproducts or reagents in the aqueous phase. 

Solid liquid extraction this involves the use of a solvent to remove solvent-soluble components of a solid mixture. 

Several experimental processes in practical chemistry are based on liquid- 

Solvent extraction is an excellent choice for aroma-compound isolation from foods when applicable. Unfortunately, many foods contain some lipid material, which limits the use of this technique since the lipid components would be extracted along with the aroma compounds. Alcohol-containing foods also present a problem in that the choice solvents (e.g. dichloromethane and diethyl ether) would both extract alcohol from the product, so one obtains a dilute solution of recovered volatiles in ethanol. Ethanol is problematic since it has a high boiling point (relative to the isolated aroma compounds), and in concentration for analysis, a significant proportion of aroma compounds would be lost with the ethanol. As one would expect, the recovery of aroma compounds by solvent extraction is dependent upon the solvent being used, the extraction technique (batch or continuous), and the time and temperature of extraction. 

Solvent extraction is a technology that the Army originally determined to be infeasible for treating explosives-contaminated soils. The technology, however, might have potential for treating these soils if a few lingering technical issues can be resolved. 

In 1982, the Army conducted laboratory-scale solvent extraction on explosives-contaminated lagoon samples from a number of sites. Each sample was washed with a solution of 90% acetone and 10% water. This process achieved greater than 99% contaminant removals. 

In 1985, the Army conducted a pilot-scale engineering analysis to determine the feasibility of full-scale solvent extraction. This analysis indicated that, for solvent extraction to be economically feasible, the number of required washes would have to be reduced and acetone would have to be recovered and reused. Currently, the only available technology for recovering acetone is distillation, which exposes acetone to heat and pressure. 

Exposing a solvent that has been used to extract explosive contaminants to heat and pressure raises serious safety considerations. In fact, the distillation column used to recover acetone often is referred to as an acetone rocket. Nevertheless, the Army believes that full-scale solvent extraction would be feasible if a safe, efficient, alternative recovery method were developed. 

A number of processes have been considered, or investigated, including  

Solvent extraction (SX), also called liquid-liquid-extraction (LEE), is the transfer of one or more solutes contained in a feed solution to another, essentially immiscible liquid (solvent). It takes place with aqueous and organic solutions at ambient temperatures and pressures (Kishk 2012). 

The organic phase used in the extraction process usually consists of two or more substances. One is the extractant itself, but very often this is as such a very viscous material, which cannot be applied in practice. It is therefore dissolved into a suitable solvent to ensure that there is good contact with the aqueous phase. 

Solvent extraction is based on preferential solubility of an analyte in one of two immiscible phases. There are two common situations that are encountered in analysis extraction of an organic analyte from a solid phase, such as soil, into an organic solvent for subseqnent analysis and extraction of an analyte from one liquid phase into a second immiscible liquid phase, such as extraction of PCBs from water into an organic solvent for subsequent analysis. 

The percent extracted can be increased by increasing the volume of solvent 1, but it is more common to use a relatively small volume of extracting solvent and repeat the extraction more than once. The multiple volumes of solvent 1 are combined for analysis. Multiple small extractions are more efficient than one large extraction. 

Liquid-liquid extraction is used extensively in environmental analysis to extract and concentrate organic compounds from aqueous samples. Examples include the extraction of pesticides, PCBs, 

Extraction of organic analytes such as pesticides, PCBs, and fats from solid samples such as food, soil, plants, and similar materials can be done using a Soxhlet extractor. A Soxhlet extractor consists of a round-bottom flask fitted with a glass sample/siphon chamber in the neck of the flask. On top of the sample chamber is a standard water-cooled condenser. The solid sample is placed in a cellulose or fiberglass porous holder, called a thimble the solvent is placed in the round-bottom flask. Using a heating mantle around the flask, the solvent is vaporized, condensed, and drips or washes back down over the sample. Soluble analytes are extracted and then siphoned back into the round-bottom flask. This is a continuous extraction process as long as heat is applied. The extracted analyte concentrates in the round-bottom flask. 

Pump clean solvent into sample cell 

Solvent extraction has one great disadvantage in that it requires a non-aqueous solvent for its operation. The solvent may be more environmentally hazardous than the metal it is extracting from effluent. Therefore, this section will only briefly describe the theory of the technique and some possible specialised applications. 

As all the major equations are described by solution equilibria the extraction process can be easily modelled. The equilibrium analysis, which is described in detail elsewhere [37], holds for the majority of cases and yields equation (14.1). 

Concentration of metal complex in organic phase divided by concentration of metal in aqueous phase. 

Solvent extraction has been used in food and feedstock applications for many years, for example in the recovery of edible oil from oilseeds (Norris, 1982). 

The use of solvent extraction has been considered for fish processing (Levin, 1958) and for meat processing (Levin, 1970) fish protein concentrate (FPC) and meat protein concentrate (MPC), respectively, are produced. MPC with a protein content of approximately 80% protein and less than 1% fat can be prepared from mixtures of meat by-products using the technique. 

The solvent used was ethylene dichloride, and as yet the MPC produced is only likely to be of use as an animal feed, owing to concerns about the use of organic solvents for foodstuffs. If new applications of solvent extraction are to be utilised, care must be taken to avoid the use of solvents that pose any potential food safety hazard. 

Solvent extraction is a separation process by which solutes are transferred from a solid or liquid mixture into a solvent. Oilseed extraction refers to preferential dissolution of oil by contacting oilseeds with a liquid solvent. Solvent extraction is the most efficient technique to recover oil from oilseeds. The process efficiency depends on the oilseed preparation prior to extraction, temperature, mode of operation (batch vs. continuous and co-current vs. countercurrent operations), equipment design and, most importantly, solvent type. Residual oil in the meal is expected to be less than 1% after commercial solvent extraction. 

A number of alternative solvents have been examined to replace hexane. For example, trichloroethylene, which is a non-flammable and non-explosive compound, received some attention as an alternative solvent to hexane during the period 1930-1955. Trichloroethylene has a high solvent capacity (oil solnbility) but it is less selective and extracts more pigments than hexane. Yet, oil can be bleached without excessive losses during reflning (Duncan, 1948). Oilseed extraction plants nsing trichloroethylene were converted to hexane after only 

Ethanol has also been utilized for oil extraction. Oil solubility in ethanol varies with temperature and water content. Soybean oil is completely miscible with absolute ethanol above 70 °C (Johnson and Lusas, 1983). As ethanol concentration decreases and water content increases, oil solubility is significantly reduced in the mixture. The higher cost and latent heat of vaporization are the major disadvantages of ethanol as a solvent for oilseed extraction. Recent developments in bioethanol production may reduce the cost of ethanol, making it a viable alternative to hexane. Solvent mixtures can also be used to extract oil. Hexane/alcohol azeotropes have been used for extraction of residual lipids from hexane-extracted meals to improve flavor and odor, specifically from soybean and peanuts. Grassy and beany flavors in oilseeds are associated with the presence of phosphatides, which can be easily extracted with hexane/alcohol mixtures. Similarly, hexane/alcohol azeotropes, specifically hexane/methanol, are very effective in extracting aflatoxin from meal. 

Dichloromethane or methylene chloride is an excellent solvent for oil extraction because of its low boiling point (39.8 °C), which makes desolventization of oil and meal easy. Furthermore, it is non-flammable and has low specific heat, latent heat of vaporization and low solubility of water. Utilization of dichloromethane for oil extraction was first demonstrated in the 1940s but the process was not economically feasible at the time because of the relatively high cost of dichloromethane. In 1986, the feasibility of cottonseed oil extraction by using dichloromethane was demonstrated at a pilot scale study (Johnson et ai, 1986). Residual oil content in the meal was lower than typically achieved with hexane extraction. Cottonseed meal produced during the process was suitable for use in poultry feed formulations, because gossypols present in cottonseed were extracted with oil and removed from meal. No residual aflatoxin was detected in alkali-refined oil. 

Acetone, isopropyl alcohol, methyl and ethyl acetate esters, ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol monoethyl ether (ethylene cellosolve) and amines have also been examined to determine their suitability for oil extraction from oilseeds (Johnson and Lnsas, 1983) but hexane remains to the choice of solvent for large oilseed extraction operations today. 

Liquid-liquid extraction is a unit operation frequently employed in the pharmaceutical industry, as in many others, for recovery and purification of a desired ingredient from the solution in which it was prepared. Extraction may also be used to remove impurities from a feed stream. 

Extraction is the removal of a soluble constituent from one liquid into another. By convention, the first liquid is the feed (F) which contains the solute at an initial concentration The second liquid is the solvent (S) which 

The solvent does the extraction, so the solvent-rich liquid leaving the extractor is the extract E). With the solute partially or completely removed from the feed, the feed has become refined so the feed-rich liquid leaving the extractor is the raffinate R). 

When the feed and solvent are brought together, the solute (A) will distribute itselfbetween the two liquid phases. At equilibrium, the ratio of this distribution is called the distribution coefficient (m)  

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  

In solvent extraction, the species to be separated is transferred between two immiscible or partially miscible phases, such as water and a nonpolar organic phase. To achieve sufficient solubility in the organic phase, the species must be in the form of a neutral, nonhydrated species. The transfer between phases is achieved by selectively complexing the species of interest causing its solubility in water to decrease with a concomitant increase in its solubility in the organic phase. 

A hydrated metal ion (Mz+) will always prefer the aqueous phase to the organic phase. To get the metal ion to extract, some or all of the inner hydration sphere must be removed. The resulting complex must be electrically neutral and organophilic, that is, have an organic surface that interacts with the organic solvent. This can be done by  

Forming a neutral complex MAZ by coordination with organic anions A-. 

Replacing water in the inner coordination sphere by large organic molecules B such that one forms MB +, which is extracted into the organic phase as an ion association complex (MBN)Z 1 Lz.  

Forming metal complexes of form ML N with ligands (L) such that they combine with large organic cations RB+ to form ion pair complexes 

Automated solvent extraction is very efficient and economical (only a fraction of the organic solvent needed for manual procedures is used by the FI A method), and more environmentally acceptable than manual methods because no solvent vapors can escape into the laboratory atmosphere from a closed FI A system. Since very small volumes of solutions are used—less than 1 mL per determination—the hazards associated with the use of inflammable solvents are reduced. It must be borne in mind, however, that certain solvents might attack pump tubing and Perspex or PVC components of the system, and therefore the compatibility of liquids handled with the manifold materials used should always be checked (see Chapter 5 and Section 6.1). 

Therefore, the dispersion process within the extraction coil should, according to the arguments raised in discussing Fig. 4.31, be less significant when the film is thinner. Experimental results reveal that this is 

being able to manipulate the manifold parameters, flow velocity, inner tube diameter, segment length, and coil length in a reproducible manner, it might eventually be possible to reach conditions at which the extraction rate is controlled by the extraction kinetics only. This would mean that FIA extractions could be used as a new tool for the study of extraction kinetics. 

Finally, it should be pointed out that a very critical part of a practical extraction system, with respect to overall dispersion or dilution of the sample zone, is the phase separator [1372]. Thus, Karlberg [116] found an almost linear relationship between the peak height and the fraction of organic phase transported to the flow cell, which observation emphasizes the importance of the incorporation of an efficient phase separator. Separators of the membrane type seem to be preferred for flow-injection 

The extraction of technetium with organic solvents was extensively used in numerous separation and concentration procedures. Technetium is extracted as pcrtcchnctate. predominantly in the form of large organic cation salts, or in lower oxidation states in the form of complex compounds. 

ITie dependence of the pertechnetate extraction with cyclohcxanol on the concentration of acid, initially in the aqueous phase, demonstrates the rapid extraetion increase upon the addition of small amounts of aeid. After a maximum extraction coefficient is reached, an exponential decrease sets in (Fig. 7.4.A). Curves similar to those in Fig. 7.4.A were also observed with eyelohexanone, tri-/t-butyl phosphate (TBP), and with solutions of TBP in a liquid hydrocarbon. 

TCO4 can be extracted by the following main types of reactions  

The solvent extraction of KTCO4 from aqueous nitric or hydrochloric acid solutions by TBP dissolved in -dodccane was studied over a wide range of TBP, HNO3 or HCI concentrations at 25, 40, and 60 °C. The extraction [114,116 was found to proceed according to the reaction  

In addition, the extraction of MTCO4 (M=H, Li, Na, K, Rb. or NH4) by TBP from aqueous solutions of MCI was examined as a function of temperature and concentration. The distribution of the pertechnetate salts to the organic phase increased in the order Rb K Na NH4 Li H. The stoichiometry of the extraction reaction was determined (120] to be 

The most common form of sample preparation is the extraction of analytes from one liquid phase to another. Clearly for this type of procedure 

Chemical derivatisation Solid phase extraction Soxhlet extraction Steam distillation Supercritical fluid extraction Homogenisation Precipitation Dialysis 

Hence if the partition coefficient of an analyte between dichloromethane and water is four, then after extracting an aqueous solution with an equal volume of dichloromethane, four times the concentration of analyte would be in the dichloromethane as in the aqueous layer. The fraction of analyte extracted into the organic solvent is also dependent on the volume of the respective phases, hence increasing the volume of the organic layer would increase the fraction of analyte extracted (and therefore the recovery). 

For analytes that are ionisable, the other factor to consider in solvent extraction is pH. Using a compound with a carboxylic add fimction (RCOOH) or a base (B) as an example, then the compoimd can exist in its ionised or its unionised form as shown below. 

The form that predominates will depend on the pAa or pAb of the compound and the pH. The unionised form will be more soluble in the organic phase and the ionised form more soluble in the aqueous phase. RCOOH RCOO +H  

Practical procedures for liquid-solid and liquid-liquid extraction are given in sections 3.1.1 and 3.1.2. 

Liquid-solid extraction involves stirring or heating the sample with a solvent to dissolve selectively one component or one group of components. Its chief use is the extraction of surfactants from an inorganic matrix. The sample is dried and treated with a dry solvent, typically a low-molecular-weight alcohol. The solvent is then filtered and evaporated. For powders it is often most effective to do the extraction in a Soxhlet apparatus, but this is not very effective for spray-dried powders. 

Liquid-liquid extraction in its simplest form involves shaking the sample in a separating funnel with two immiscible solvents, chosen so that the material to be extracted is much more soluble in solvent A than in solvent B, while the material from which it or they are to be separated is much more soluble in B than in A. The denser solvent is run off into a second separating funnel, and solvent B is re-extracted with more A, Several extractions may be necessary. The portions of solvent A are washed with solvent B, The extracted material is recovered by evaporating solvent A. 

The liquid-liquid extraction procedure tends to be tedious, but if properly conducted it is very quantitative and it can be used to extract quite large quantities of material. Typical aqueous phases are water alone and mixtures of water with methanol, ethanol or propan-2-ol, while typical non-aqueous phases are petroleum ether or other hydrocarbons, diethyl ether, chloroform and butanols. It is used chiefly to extract fatty alcohols and ethoxylates, fatty acids, fatty amines and alkanolamides from mixtures containing more polar surfactants, but the possible range of uses is much wider than this. 

From a more practical viewpoint, the solvent extraction of bituminous coals has been used as a means of coproducing clean liquid transportation fuels as well as solid fuels for gasification. Coal solvents are created by hydrogenating coal tar distillate fractions to the level of a fraction of a percent, thus enabling bituminous coal to enter the liquid phase under conditions of high temperature (above 400°C [750°F]). The pressure is controlled by the vapor pressure of the solvent and the cracked coal. Once liqnefied, mineral matter can be removed via centrifnga-tion, and the resultant heavy oil prodnct can be processed to make pitches, cokes, as well as lighter products. 

Solvents for coal extraction (Chapters 10 and 11) have been classified into four types  

Nonspecific solvents They extract a small amount (up to approximately 10%) of coal at temperatures up to 100°C (212°F). These are low boiling liquids like methanol, ethanol, benzene, acetone, and ether. The extract is believed to arise from the resins and waxes occluded in the coal matrix. 

Specific solvents They extract 20%-40% of coal at temperatures below 200°C. The nature of the coal extract and the parent coal is believed to be similar. Hence, such solvents can be in fact considered nonselective in their action on coal. Pyridine, A -methylpyrrolidone, dimethylformamide, and dimethylacetamide are examples of this type of solvent. They are mostly nucleophilic in nature due to the presence of a lone pair of electrons on the nitrogen atom. 

Degrading solvents They extract up to 90% of the coal at temperatures up to 400°C (750°F). The mechanism of solvent action is by thermal degradation of coal into smaller fragments. At the end of the extraction, the solvent can be almost completely recovered without change in its chemical form. Examples of this type of solvents include phenan-threne, diphenyl, phenanthridine, and tar oil fractions. 

OTHER SEPARATION METHODS WITH ICP-MS 5.5.1. Solvent extraction 

Many of the LC-ICP-MS studies mentioned above employ solvent extraction for fractionating and cleaning up the sample prior to the 

Determination of trace impurities in uranium is one of the potentially major applications of ICP-MS because the mass spectrum of uranium from an ICP is very simple. Spectral overlap with analyte signals is not a problem, as is often the case in many optical emission methods. In ICP-MS, however, this analysis is often limited by suppression of analyte signal induced by the large excess of uranium in the solution. Various selective extracting agents (e.g, tri-n-octylphosphine oxide) have been 

Lobster hepatopancreas. Also from National Research Council of Canada. 

If a sample, solid or liquid, is known to be a mixture, solvent extraction may be used to selectively remove or extract a material. Solvent extraction is also a convenient method to enrich a particular component—either in the extracted phase or in the residual phase (what is left behind). Many of the comments provided earlier (Section 5.1) apply here. Obviously, it is necessary to find a solvent that has a high affinity for the component(s) to be extracted and a low affinity for the remaining material. It is not a good idea to select a solvent that is midway in its ability to extract an ingredient. If affinity exists for both phases then there is a risk of estabUshing a stable emulsion. 

Obviously, it is not always possible to overcome this problem, especially if the system contains surfactant materials. In such cases, in which aqueous systems are involved, the addition of a polar ionic substance, such as salt or sodium sulfate, may be necessary to help break (salt-out) an emulsion. Once a material has been extracted, it may be measured directly either in the extraction medium (see comments about solutions in Section 5.1) or on the isolated material after removing the extraction solvent (see comments in Section 5.2). If the solvent is removed, make sure that all traces of solvent are eliminated prior to analysis, and always document what solvents have been used. 

Examples of the practical use of solvent extraction are the use of water to remove water-soluble components from organic mixtures (the remaining organic phase is analyzed), the use of methanol with mineral oils or polymers to remove polar additives, the use of compound-selective solvents on powdered mixtures, and the use of Freon for the extraction and measurement of hydrocarbons and organics from soil and environmental water 

Liquid-liquid extraction is a technique in which a solution (usually aqueous) is brought into contact with a second solvent (usually organic), essentially immiscible with the first, in order to bring about a transfer of one or more solutes into the second solvent. The separations that can be performed are simple, clean, rapid, and convenient. In many cases separation may be effected by shaking in a separatory funnel for a few minutes. The technique is equally applicable to trace level and large amounts of materials. 

In the case of inorganic solutes we are concerned largely with samples in aqueous solution so that it is necessary to produce substances, such as neutral metal chelates and ion-association complexes, which are capable of extraction into organic solvents. For organic solutes, however, the extraction system may sometimes involve two immiscible organic solvents rather than the aqueous-organic type of extraction. 

Although solvent extraction has been used predominantly for the isolation 

To understand the fundamental principles of extraction, the various terms used for expressing the effectiveness of a separation must first be considered. For a solute A distributed between two immiscible phases a and b, the Nernst Distribution (or Partition) Law states that, provided its molecular state is the same in both liquids and that the temperature is constant  

Concentration of solute in solvent a [/l]a Concentration of solute in solvent b [4] , D 

Difficult separations can often be effected by liquid-liquid solvent extraction, which depends on differences in the distribution of solute species between two immiscible or partially immiscible phases. For a solute species A, this distribution is governed by the Nernst partition law 

UO2 fuel elements may be contemplated for use in nuclear power plants or weapons. 

A further possible reason for separating plutonium from uranium and the fission products relates to the extreme toxicity of Pu. Plutonium(IV) mimics iron(lll) (the aqueous E° and charge-to-radius ratios of the two ions are very similar), so that cancers are likely to result from the absorption of even microgram amounts of ingested radioactive Pu into organs of the human body (bone marrow, spleen, liver) that store iron(III). It may therefore be considered desirable to remove Pu, a long-lived health hazard, from spent nuclear fuels before disposal of the latter in repositories that may not remain inviolate for thousands of years into the uncertain future (most of the fission products decay away to negligible levels of activity in an acceptable time). 

The spent fuel element is still mainly UO2 and is dissolved in aqueous nitric acid, which is oxidizing enough to take the uranium to the VI oxidation state as 1102 (aq) and Pu to Pu +(aq) (the uranyl ion U02 can be regarded as hydrolyzed see Section 13.6). Treatment of the solution of uranyl and plutoniura(IV) nitrates with either an iron(II) salt or SO2 will reduce all the Pu to Pu + (aq), which is not extractable with TBP, but will leave the uranium(VI) untouched (see Exercise 15.5). The solution is then equilibrated with TBP (which is immiscible with water) or TBP in an alkane solvent. The U02 forms a neutral complex containing both TBP and the nitrate ions, which are present in large excess  

The U complex, having no net charge and already containing TBP solvent ligands, passes preferentially into the TBP solvent phase, leaving the Pu and almost all the fission products such as Sr +, I , and Cs+ behind in the aqueous phase. 

One of the simplest and most efficient approaches for aroma isolation is direct solvent extraction. The major limitation of this method is that it is most useful on foods that do not contain any lipids. If the food contains lipids, the lipids will also be extracted along with the aroma constituents, and they must be separated from each other prior to further analysis. Aroma constituents can be separated from fat-containing solvent extracts via techniques such as molecular distillation, steam distillation, and dynamic headspace. 

A second consideration in solvent extraction is for solvent purity. Solvents must be of the highest quality, which often necessitates in-house distillation prior to use. One must be mindful that various qualities of solvents can be purchased, and GC grade is highly recommended (not high pressure liquid chromatography (HPLC) or other quality). Furthermore, a reagent (solvent) blank must always be run to monitor solvent artifacts irrespective of the quality of the solvent 

Recovery of Model Compounds from an Alcohol-Water (12% v/v) System 

Source From Cobb, C.S., M.W. Bursey, J. Agric. Food Chem., 26, p. 197, 1978. With permission. 

This technique has often been used to treat ammonia water from coking processes or even from coal gasification processes. In these processes, phenol production flows are very high and concentrations are at least 3 g T, The aim is to reclaim and market ctesylic adds. The technique is coo expensive because the solvent must necessarily be regenerated (solvent stripping). 

As a result, it has been phased out in coking plants, but nevertheless remains feasible in refineries because the solvent, a light fuel oil of the LCO type, is used in much smaller volumes and sent back to the refinery FO network in an open system without regeneration. This cuts investments by two-thirds. Typical LCO flow races in refineries vary from 1 to 16 m h , whereas they are at least five times higher in caking plants. 

ArCOOH -H ArOH NS2C03 CH2CI2 ArCOO- Na+ -h ArOH 

Distillation splits a mixture into Auctions according to the boiling points of the mixture constituents. In contrast, solvent refining segregates compoimds with similar compound types, such as paraffins and aromatics. The three main types of solvent refining are solvent deasphalting, solvent extraction, and solvent dewaxing. 

Solvent deasphalting takes advantage of the fact that aromatic compounds are insoluble in paraffins. Propane deasphalting is commonly used to precipitate asphaltenes from residual oils. Deasphalted oil (DAO) is sent to hydrotreaters, FCC units, hydrocrackers, or fuel-oil blending. In hydrocrackers and FCC units, DAO is easier to process than straight-run residual oils. This is because asphaltenes easily form coke and often contain catalyst poisons such as nickel and vanadium, and the asphaltene content of DAO is (by definition) almost zero. 

An advanced version of solvent deasphalting is residuum oil supercritical extraction, or ROSE. The ROSE Process was developed by the Kerr-McGee Corporation and now is offered for license by KBR Engineering and Construction, a subsidiary of Halliburton. In this process, the oil and solvent are mixed and heated to above the critical temperature of the solvent, where the oil is almost totally insoluble. Advantages inelude higher recovery of deasphalted liquids, lower operating costs due to improved solvent recovery, and improved energy efficiency. The ROSE process can employ three different solvents, the choice of which depends upon process objectives Propane Preparation of lube base stocks 

phenol, furfural, and cresylic acid are widely used as solvents. In the past, some refiners installed the Edeleanu process, in which the solvent is liquid sulfur dioxide, but the hazards of potential leaks made it imdesirable. Chlorinated ethers and nitrobenzene also have been used. 

Solvent dewaxing removes wax (normal paraffins) from deasphalted lube base stocks. The main process steps include mixing the feedstock with the solvent, chilling the mixture to crystallize wax, and recovering the solvent. Commonly used solvents include toluene and methyl ethyl ketone (MEK). Methyl isobutyl ketone (MIBK) is used in a wax deoiling process to prepare food-grade wax. 

To extract a desired component A from a homogeneous liquid solution, one can introduce another liquid phase which is insoluble with the one containing A. In theory, component A is present in low concentrations, and hence, we have a system consisting of two mutually insoluble carrier solutions between which the solute A is distributed. The solution rich in A is referred to as the extract phase, E (usually the solvent layer) the treated solution, lean in A, is called the raffinate, R. In practice, there will be some mutual solubility between the two solvents. Following the definitions provided by Henley and Staffin (1963) (see reference Section C), designating two solvents as B and S, the thermodynamic variables for the system are T, P, x g, x r, Xrr (where P is system pressure, T is temperature, and the a s denote mole fractions).. The concentration of solvent S is not considered to be a variable at any given temperature, T, and pressure, P. As such, we note the following  

Graphical methods at best are simply illustrative for the student today, but they are occasionally referenced by the process engineer. Extraction, like distillation can be viewed as a stage-wise operation, and hence metliods based on the McCabe Thiele approach briefly described in Chapter 4 have been applied to preliminary design cases. Indeed, both absorption and adsorption are stage-wise operations. 

Suitable organic solvents, such as ether, benzene, naphtha and the like, are more soluble than in water. This makes it possible to separate them from other substances which may accompany them in the water solution but which are not soluble in the solvents employed. Hence, one application of solvent extraction is the analytical determination of unsaponifiable oils and waxes in admixture with fatty material by submitting the mixture to vigorous saponification with alcoholic potash or, if necessary, sodium ethylate, and to dilute the product with water and extract with petroleum ether. The soaps remain in the aqueous solution while the unsaponifiable oils and waxes dissolved in the ether. The addition of a salt to an aqueous solution prior to extraction is sometimes practiced in some processes. In older processes, SOj is employed in the separation of aromatic and highly saturated hydrocarbons, taking advantage of the much greater solubility of the solubility of the aromatics and 

The efficiencies which may be obtained can consequently be calculated by simple stoichiometry from the equilibrium data. In the ease of countercurrent-packed columns, the solute can theoretically be completely extracted, but equilibrium is not always reached because of the poorer contact between the phases. The rate of solute transfer between phases governs the operation, and the analytical treatment of the performance of such equipment follows closely the methods employed for gas absorption. In the ease of two immiscible liquids, the equilibrium concentrations of a third component in each of the two phases are ordinarily related as follows  

As was pointed out in Section 2.18, the crude products of most organic reactions are multicomponent mixtures, and a convenient initial isolation procedure, for the first stages of both the separation of such mixtures and of the purification of the components, may involve solvent extraction processes. The general cases which are discussed below to illustrate the technique of solvent extraction are selected to cover many of the commonly met systems. The student is recommended to refer to the comments in Section 2.18 on the necessity of assessing the chemical and physical nature of the components of a particular reaction mixture with regard to their solubilities in solvents, and to their acidic, basic or neutral characteristics. 

Batch-extraction processes. Perhaps one of the most frequent cases that is encountered is the separation of a neutral organic compound (or compounds) from a solution or suspension (as either a solid or liquid) in an aqueous medium, by shaking with an organic solvent in which the compound is soluble and which is immiscible (or nearly immiscible) with water. 

If prior information is not available, solvent selection should be based on some small-scale trials. A few millimetres of suspension or solution to be extracted are placed in a small test tube and shaken with an equal volume of diethyl ether, when dissolution of suspended material clearly indicates that the solvent would be satisfactory. If the solution to be extracted is homogeneous initially, then the ether solution is removed with a dropper pipette on to a watch glass, and the ether is allowed to evaporate to determine whether material has been extracted. A little experience soon enables the student to differentiate between organic liquids so extracted and traces of water simultaneously removed during the extraction process. If extraction with diethyl ether proves unsatisfactory the experiment is repeated with a fresh sample of reaction mixture 

Occasionally emulsions are formed in the extraction of aqueous solution by organic solvents, thus rendering a clean separation impossible. Emulsion formation is particularly liable to occur when the aqueous solution is alkaline, and when dichloromethane is the extracting solvent. The emulsion may be broken by any of the following devices, but in general its occurrence may be minimised 

An increase in concentration of ionic species may be helpful as the result of the addition of sodium chloride, sodium sulphate or potassium carbonate, for example. With extractions involving alkaline solutions the addition of dilute sulphuric acid may be helpful, providing that complete neutralisation or acidification does not take place since this may result in a change in the chemical nature of some of the components (see below). 

Perfume materials obtained in this way are referred to as essential oils. Thus, for example, the oil obtained by steam distillation of lavender is known as the essential oil of lavender, or lavender oil. Sometimes, the monoterpene hydrocarbons are removed from the oils by distillation or solvent extraction to give a finer odour in the product. The process is known as deterpenation and the product is referred to as a terpeneless oil. This is, of course, a misnomer since, for example, the major component of lavender oil terpeneless is linalyl acetate, a monoterpene. 

Ethanolic extraction is not used very much for plant materials because of the high proportion of water compared with oil in the plant (vanilla beans are an important exception). It is more important with 

The most important extraction technique nowadays is simple solvent extraction. The traditional solvent for extraction was benzene, but this has been superseded by other solvents because of concern over the possible toxic effects of benzene on those working with it. Petroleum ether, acetone, hexane and ethyl acetate, together with various combinations of these, are typical solvents used for extraction. Recently, there has been a great deal of interest in the use of carbon dioxide as an extraction solvent. The process is normally referred to as super-critical carbon dioxide extraction but, in fact, the pressures employed are usually below the critical pressure and the extraction medium is sub-critical, liquid carbon dioxide. The pressure required to liquefy carbon dioxide at ambient temperature is still considerable and thus the necessary equipment is expensive. This is reflected in the cost of the oils produced, but carbon dioxide has the advantage that it is easily removed and there are no concerns about residual solvent levels. 

The product of such extractions is called a concrete or resinoid. It can 

The product of such solvent extractions is called a concrete or resinoid. It can be extracted with ethanol to yield an absolute or distilled to give an essential oil. The oil can then be deterpenated. With some particularly viscous concretes, such as those from treemoss or oakmoss, it is more usual to dissolve the concrete in a high boiling solvent and then codistil the product with this solvent. 

Oil Types of process used Plant part extracted Approximate annual production (tonnes) Typical country of origin 

The detection limits obtained by flame and graphite furnace AAS and the concentration levels of the elements in seawater are summarized in Table 2. In general, graphite furnace AAS provides better sensitivities for many elements than the flame technique. Even so, AAS sensitivity is insufficient for the direct determination of most ultra-trace elements. Furthermore, concentrated salts and undissolved particulates cause severe interferences with the determination of trace elements by AAS. Therefore, it is necessary to concentrate the analytes before the determination, and, if possible, to separate the analytes from dissolved major constituents and particulates. Solvent extraction, coprecipitation and ion-exchange techniques are the most widely used techniques for the preconcentration of seawater. In the following sections, these techniques will be reviewed. It should be noted here that the efficiencies of the recovery of the analytes as well as the contamination from reagents and solvents must be carefully examined when the preconcentration techniques are applied. Chakrabarti et al. [10] have summarized the work on the application of preconcentration techniques to marine analysis by AAS. Hence, only some representative applications will be introduced hereafter. 

Solvent extraction is one of the methods widely used for concentration and separation. Most heavy metals are extracted with chelating reagents into organic solvents [35]. Some chelating agents commonly used in atomic absorption spectrometry are shown in Fig. 3. APDC and DDC are most commonly used in AAS. Solvents such as ketones, esters, ethers, alcohols, and other oxygen-containing hydrocarbons are suitable for the flame atomic absorption technique. Of these solvents, MIBK (methyl isobutyl ketone, 

Brooks et al. [36] pioneered solvent extraction for seawater with an APDC—MIBK extraction technique for the determination of six elements in seawater by flame AAS. However, the metal complexes extracted into 

MIBK were unstable (decomposing within one day), which makes the technique inconvenient for routine analysis. 

The procedure of MIBK—nitric acid successive extraction employed by Jan and Young [37] is as follows. For the APDC—MIBK extraction, a 200 ml seawater sample in a Teflon beaker containing 2 ml of 1% APDC is heated to incipient boiling at a pH of about 4. After cooling to room temperature, 7 ml of MIBK is added to the sample, and the mixture is transferred into a polyethylene bottle and shaken for 25 min on a mechanical shaker. After 

The properties of the lube oil that are set by the extraetion process are the viscosity index (VI), oxidation stability and thermal stability. These properties are related to aromatics, aliphatic sulfur, total sulfur and nitrogen levels present in the base stock. 

Base stock VI has historically been used as a performance indicator for the base stoek. The VI specifieation sets the extraction severity required to achieve the target. VI is also an indicator of relative stability from the same feed. VI is crude sensitive under constant extraction conditions. 

Molecular Weight Specific Heat 130°F Boiling Point 1 atm., °F Flash Point, F Viscosity 140°F, Cp Melting Point, °F Latent Heat b.p., Btu/lb Toxicity 

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Francis, A. W. "Handbook for Components in Solvent Extraction," Gordon Breach, New York, 1972. 

Pu (86 years) is formed from Np. Pu is separated by selective oxidation and solvent extraction. The metal is formed by reduction of PuF with calcium there are six crystal forms. Pu is used in nuclear weapons and reactors Pu is used as a nuclear power source (e.g. in space exploration). The ionizing radiation of plutonium can be a health hazard if the material is inhaled. 

This technique is based on the selectivity of a solvent for different families or individual components in a mixture. Solvent extraction can be either analytical or preparatory in function. 

There are of course liquid-liquid equilibria between hydrocarbons and substances other than water. In practice these equilibria are used in solvent extraction processes. The solvents most commonly used are listed as follows ... 

The foremost separation process is crude distillation and in second place, if deeper conversion is envisaged, solvent extraction (deasphalting). 

Processing Vacuum Residue by Solvent Extraction (Deasphalting) (Biedermann et al., 1987)... 

To ensure disposal water quality is in line with regulatory requirements (usually 40 ppm), the oil content in water is monitored by solvent extraction and infrared spectroscopy. The specification of 40 ppm refers to an oil in water content typically averaged over a one month period. 

J. A. Marinsky and Y. Marcus, eds.. Ion Exchange and Solvent Extraction, Marcel Dekker, New York, 1973. 

Finally, micellar systems are useful in separation methods. Micelles may bind heavy-metal ions, or, through solubilization, organic impurities. Ultrafiltration, chromatography, or solvent extraction may then be used to separate out such contaminants [220-222]. 

Lanthanum was isolated in relatively pure form in 1923. Iron exchange and solvent extraction techniques have led to much easier isolation of the so-called "rare-earth" elements. 

The element may be obtained by separating neodymium salts from other rare earths by ion-exchange or solvent extraction techniques, and by reducing anhydrous halides such as NdFs with calcium metal. Other separation techniques are possible. 

Gadolinium is found in several other minerals, including monazite and bastnasite, both of which are commercially important. With the development of ion-exchange and solvent extraction techniques, the availability and prices of gadolinium and the other rare-earth metals have greatly improved. The metal can be prepared by the reduction of the anhydrous fluoride with metallic calcium. 

The cost of dysprosium metal has dropped in recent years since the development of ion-exchange and solvent extraction techniques, and the discovery of large ore bodies. The metal costs about 300/kg in purities of 99+%. 

Ytterbium occurs along with other rare earths in a number of rare minerals. It is commercially recovered principally from monazite sand, which contains about 0.03%. Ion-exchange and solvent extraction techniques developed in recent years have greatly simplified the separation of the rare earths from one another. 

In 1965, the Dubna workers found a longer-lived lawrencium isotope, 256Lr, with a half-life of 35 s. In 1968, Thiorso and associates at Berkeley used a few atoms of this isotope to study the oxidation behavior of lawrencium. Using solvent extraction techniques and working very rapidly, they extracted lawrencium ions from a buffered aqueous solution into an organic solvent — completing each extraction in about 30 s. 

Different types of other coal liquefaction processes have been also developed to convert coals to liqnid hydrocarbon fnels. These include high-temperature solvent extraction processes in which no catalyst is added. The solvent is usually a hydroaromatic hydrogen donor, whereas molecnlar hydrogen is added as a secondary source of hydrogen. Similar but catalytic liquefaction processes use zinc chloride and other catalysts, usually under forceful conditions (375-425°C, 100-200 atm). In our own research, superacidic HF-BFo-induced hydroliquefaction of coals, which involves depolymerization-ionic hydrogenation, was found to be highly effective at relatively modest temperatnres (150-170°C). 

Another line of analytical use is exemplified by the properties of l-(2-thiazolylazoi-2-naphthol (305), whose complexes with metals may be used for their spectrophotometric and titrimetric determination, as wel] as for their separation by solvent extraction (564, 568, 953-957, 1040). 

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