Aqueous phase liquid extractor

Clement RE, Suter SA,Tosine HM (1989), Chemosphere 18 133-140. Analysis of large volume water samples near chemical dump sites using the aqueous phase liquid extractor (APLE) Hellmann A (1986), Analytik von Oberflachengewassern". Thieme Verlag, Stuttgart Le Bel GL, Williams DT, Ryan JJ, Lau BPY (1986), in Chlorinated Dioxins and Dibenzofurans in Perspective . Evaluation of XAD-2 resin cartridge for concentration/isolation of chlorinated dioxins and furans from drinking water at the parts-per-quadrillion level", p. 329-341, Eds. Rappe C, Choudhary G, Keith LH Lewis Publishers, Chelsea Mahle NH, Lamparski L, NestrickTJ (1989), Chemosphere 18 2257-2261. A method for determination of 2,3,7,8-tetrachlorodibenzo-p-dioxin in processed waste water at the parts per quadrillion level"... 

In addition to solid-liquid collection techniques, in situ sampling methods were developed that contemporarily performed analyte collection and extraction. These systems utilize either sequential or continuous LLE. An example is provided by the aqueous phase liquid extractor (APLE) of Clement and coworkers [22] designed to sample surface water near dump sites where PCDDs and PCDFs were present at level of pg/L. The APLE was capable of extracting up to 200 L water in a single batch process. A spray-bar on the top dispersed a heavier-than-water solvent (methylene chloride) as a fine spray across the surface of the water sample, pushed into the system by a submersible pump. Efficiency in extraction is ensmed by continuous recirculation of the solvent. Devices like the one described avoid the problem of transporting to the laboratory large volumes of sample, but they often remain cumbersome and difficult to be transported. 

Clement, R.E., Suter, S.A., and Tosine, H.M., Analysis of large volume water samples near chemical dump sites using the aqueous phase liquid extractor (APLE), Chemosphere, 18 (suppl 1-6), 133,1989. 

A total of 25 samples were collected from the upper and lower St. Clair and Detroit Rivers, and from the lower Niagara River and the river plume in Lake Ontario in the summers of 1984 and 1985. Water was pumped from a 1 m depth using a submersible pump which fed directly into a Westphalia continuous-flow centrifuge (9500 rpm). The centrifuged water was then collected in a 200 L stainless-steel aqueous phase liquid-liquid extractor (APLE)..A surrogate spike containing 1,3-dibromobenzene 1,3,5-tribromobenzene 1,2,4,5-tetra-... 

Plot of extraction efficiency versus pH of the aqueous phase for the liquid-liquid extractor of the molecular weak acid in Example 7.16. 

B. Tropohne. In a 1-1., three-necked, round-bottomed flask equipped with a mechanical stirrer, addition funnel, and reflux condenser are placed 500 ml. of glacial acetic acid and then, cautiously, 100 g. of sodium hydroxide pellets. After the pellets have dissolved, 100 g. of 7,7-dichlorobicyclo[3.2.0]hept-2-en-6-one is added and the solution is maintained at reflux under nitrogen for 8 hours. Concentrated hydrochloric acid is then added until the mixture is about pH 1 approximately 125 ml. of acid is required. After the addition of 1 1. of benzene, the mixture is filtered and the solid sodium chloride is washed with three 100-ml. portions of benzene. The two phases of the filtrate are separated and the aqueous phase is transferred to a 1-1. continuous extractor (Note 8) which is stirred magnetically. The combined benzene phase is transferred to a 2-1. pot connected to the extractor and the aqueous phase is extracted for 13 hours. Following distillation of the benzene, the remaining orange liquid is distilled under reduced pressure... 

The concept of extractive reaction, which was conceived over 40 years ago, has connections with acid hydrolysis of pentosans in an aqueous medium to give furfural, which readily polymerizes in the presence of an acid. The use of a water-immiscible solvent, such as tetralin allows the labile furfural to be extracted and thus prevents polymerization, increases the yield, and improves the recovery procedures. In the recent past an interesting and useful method has been suggested by Rivalier et al. (1995) for acid-catalysed dehydration of hexoses to 5-hydroxy methyl furfural. Here, a new solid-liquid-liquid extractor reactor has been suggested with zeolites in protonic form like H-Y-faujasite, H-mordenite, H-beta, and H-ZSM-5, in suspension in the aqueous phase and with simultaneous extraction of the intermediate product with a solvent, like methyl Aobutyl ketone, circulating countercurrently. 

For the determination of cresol in water, CLP guidelines state that the aqueous sample be brought to pH 11 by the addition of sodium hydroxide (NaOH). The basic mixture is then extracted with methylene chloride either in a separatory funnel or a continuous liquid-liquid extractor. The aqueous phase is then acidified to pH 2 and reextracted with methylene chloride. This second extract is concentrated by evaporation and subjected to GC/mass spectrometry (MS) analysis for identification and quantification. 

For the purposes of this method, a water sample is defined as a single phase system that is primarily clear water but may contain very small amounts of floating, suspended and settled particulate matter. Multiple phases should not be present (see Section 8.4). Approximately 1 L of the water sample is spiked with the internal standard solution and filtered to separate the aqueous and particulate fractions. The filtered aqueous fraction is extracted with methylene chloride using a separatory funnel or continuous liquid-liquid extractor. The particulate fraction is extracted with toluene in a SDS extractor. The extracts of the two fractions are then combined for cleanup. 

A flask was charged with the bis-sulfonamide (1.31 g, 3.00 mmol), and NIL was condensed at -78 C with magnetic stirring. The mixture was allowed to warm to -33 "C and solid Li (220 mg, 31.7 mmol) was gradually added. The suspension turned blue and the reaction was quenched after 80 min by dropwise addition of brine (0.5 mL). NH3 was evaporated and the residue was diluted with H2O (10 mL) and concentrated in vacuo until the condensation of water was observed. The residue was diluted with water (10 mL), acidified with concentrated HCl, and extracted with CH2CI2. The aqueous phase was concentrated in vacuo until a white precipitate formed. NaOH (25% aqueous, 15 mL) was added and the aqueous solution was extracted with CH2CI2 in a liquid/liquid extractor for 42 h. Concentration of the organic phase yielded 2,5-diaminobicyclo[2.2.1]heptane as a colorless oil (321 mg, 85%). 

An extractor with hollow fibres of polypropylene could operate with the aqueous phase inside the fibers at a pressure slightly greater than the pressure of the organic phase on the outside. The pores of the membrane would fill with the organic solvent, and the liquid-liquid interface would be at the pore mouths. The concentration gradients are sketched in Fig. 26.14 for an example where the equilibrium solute concentration is much higher in the organic phase. The overall resistance for this case is... 

Figure 4.23 Illustrates another alternative for the separation of both phases once the batch liquid-liquid extraction has been finished. Formerly conceived for solid-liquid extractions, this complex mechanical assembly [20] consists of two automatic burettes for addition of the two phases, the extractor —moveable in various fashions— and a vertically moving paddie stirrer. The extraction vessel rotates at a high speed, which promotes phase separation, as shown in the figure. The lighter phase creeps up the walls and passes to an upper receptacle —the separation is facilitated by adding more aqueous phase. Once separation Is complete, an aspiration probe withdraws the organic phase. Finally, a mechanical system turns the vessel over for cleaning.

Solvent extraction (3) Liquid-liquid extraction is used to separate water and AA. The top of the extractor is forwarded to a solvent separator. The extractor bottom Is sent to the raffinate stripper (5) to recover solvents. Crude acrylic acid (CAA) is separated from the solvents by distillation. The overhead vapor is condensed in an internal thermoplate condenser. The two-phase condensate is separated. The organic phase is recycled. The aqueous phase is sent to the raffinate stripper (5). The column bottom, mostly AA and acetic acid, is routed to the CAA separator (4). 

Where Vscf - volume of ScF phase in extractor (ml). Vl- volume of liquid phase in extractor (mL). C/ = concentration of flow into ScF phase = DCag, D = distribution coefficient = Cscf/Cag, Co, = concenb ation of metal in aqueous phase (mol/mL). Cscf = concentration of metal complex in ScF phase (mol/mL), Q = flow rate through extractor (mL/min), and / time (min). 

LIE can be performed simply using separatory funnels. The partition coefficient should therefore be large because ffiere is a practical Umit to the phase-volume ratio and the number of extractions. When the partition coefficient is small and the sample very dilute, a large volume must be handled and continuous liquid-liquid extractors should be used. The extractions then take several hours. Such extractors have been described in the literature [ 187]. The partition coefficient may be increased by adjusting the pH to prevent ionization of acids or bases or by forming ion pairs or hydrophobic complexes with metal ions, for example. The solubihty of analytes in the aqueous phase can be reduced by adding salts. Fractionation of samples into acidic, basic and neutral fractions can be attained by successive extractions at different pH [ 1 ]. 

In contrast to gas/liquid contactors the two-phase system in the mass transfer zone of solvent extractors has a well-defined structure, which is called drop regime. One phase, mostly the organic phase, is dispersed in droplets in the other (mostly aqueous) phase. Therefore, the dimensioning of solvent extractors should be less empirical than that of distillation and absorption colmnns. 

Dynamic PFE usually requires implementing a concentration step prior to the determinative step, and because the extracted analytes are dissolved in a liquid (usually aqueous) phase, SPE is a highly useful tool for avoiding the dilution effect. For this purpose, SPE cartridges and columns packed with appropriate sorbents and coupled online to the extractor outlet can be employed in the same way as commented on for static PEE. Miniaturized retention has also been developed by using solid-phase microextraction (SPME). 

Liquid-liquid extraction (LLE) LLE is the classical method used for herbicide isolation, especially from water and biological fluid samples. Ethyl acetate, dichloromethane, and their mixtures are among the preferred extraction solvents for phenylureas, triazoles, amides, carbamates, benzimidazoles, and chlorotriazines. The extraction efficiency is modified by adjustment of pEI and ionic strength in the aqueous phase. In situ derivatization of the target analytes is also used as an effective tool (e.g., chlorophenoxy acidic herbicides are derivatized with dimethyl sulfate prior to their extraction by n-hexane). The classical way of performing LLE is the separation funnel extraction. Some continuous LLE extractors or steam distillers are also available. 

The transfer of the phosphine-assisted catalytic processes to aqueous media prompts the development of specific hydrophilic ligands. The most important rationale for the application of such ligands is the development of phase-separation techniques. In the biphasic liquid-liquid technique, the hydrophilic phosphine works as an effective extractor of palladium to the aqueous phase. However, numerous recent works coming primarily from Genet s group (vide infra) show that many important Pd-catalyzed reactions can be made to run under very mild conditions in homogeneous aqueous media if carried out in the presence of hydrophilic phosphines—essentially aqueous phosphine-assisted catalysis. 

Thermospray nebulizers can be used to extract SVOCs from aqueous samples. When several thermospray probes simultaneously deliver solvent and sample into a cooled extraction vessel an efficient extraction can occur because of the increased exposure of the phases. Farrel and Pacey built a device called a thermospray liquid-liquid extractor (TSLLE). Using the TSLLE and methylene chloride they evaluated aqueous mixtures of SVOCs and obtained recoveries ranging from 80 to 100% during a single, 1-h cycle. The aqueous sample was dehvered at 4 or 5 mL/min, and the methylene chloride was delivered at 2 or 3 mL/min. through heated capillaries into the chilled extraction vessel. The system was vented above a chilled condenser, and a stopcock at the bottom of the vessel allowed for phase separation of the methylene chloride after extraction (72). 

The final type of hybridization is the use of different models for different unit operations. Although this appears to be inconsistent at first, it is reality that thermodynamic models are not perfect and that some work much better for LLE than for VLE, some work better for low pressures and others for high pressures, and some work for hydrocarbons but not for aqueous phases. Furthermore, simulators perform calculations for individual units and then pass only component flowrates, temperature, and pressure to the next unit. Thus, consistency is not a problem. Therefore, one should always consider the possibility of using different models for different unit operations. All the simulators allow this, and it is essential for a complex flowsheet. An activity-coefficient model can be used for the liquid-liquid extractor and an equation of state for the flash unit. This hybridization can be extremely important when, for exanple, some units contain mainly complex organics and other units contain light hydrocarbons and nitrogen. 

Each cell in the extraction system presented in Fig. 122 is called a mixer-settler extractor and is made up of two parts. The role of the first part, the mixer, is to emulsify the incoming aqueous and organic phases and to transfer the emulsion to the second part of the extractor-settler cell. The purpose of the settler is to stratify the phases and enable the separation of the two liquids. 

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