Alternative Extractants

W. D. Arnold md D. J. Crouse, Evaluation of alternative Extractants to TBP-1, ORNL/TM-7536, Oak Ridge National Laboratory, Oak Ridge, Term., 1980. 

Modifications and improvements to the basic process have been made to reduce the quantity of waste products (21,22) in the wet chemical process, to recover HF, and to economically process low Ta, high Nb containing raw materials (23). Several alternative extraction media have been reported in the hterature. Most, except for tributylphosphate (TBP) (24) and tri- -octylphosphine oxide (TOPO) (25), have never been used in industry. 

Costley et al. [113] have evaluated the use of a range of organic solvents (dichloromethane, water, acetone, hexane, xylene) in the microwave extraction of oligomers from PET and have compared MAE to alternative extraction approaches (Soxhlet, Pan-bomb). 

The extraction procedure described by Aepli, Munter, and Gall (1) may be used, if preferred, as an alternate extraction procedure for the residue after ether extraction. 

A recirculation system extracts contaminated groundwater from the site, adds to or amends the extracted water ex situ, and reinjects the activated water to the subsurface, generally upgradient of the contaminated zone. As an alternative, extraction and injection are performed at different elevations in a single well, creating vertical circulation. A groundwater recirculation configuration may be used to provide containment of a plume or to allow the addition of amendments in a more controlled environment. 

An alternate extraction procedure used by Aspila et al. [60] involves ignition of the sediment with potassium persulphate in a PTFE-lined Parr bomb. 

Potable water and raw source water Sample acetylated in situ by addition of acetic anhydride, solvent extracted and concentrated alternatively, extracted acidic sample derivatized by pentafluorobenzyl bromide and cleaned up by column chromatography HRGC-ECD (for pentafluorobenzyl derivative) HRGC-MS (for acetyl derivative) <50 ng/L (pentafluorobenzyl) <50 ng/L (acetyl derivative) 10-64% (pentafluorobenzyl derivative) 70-132% (acetyl derivative) Sitholeetal. 1986... 

The overall method includes sample collection and storage, extraction, and analysis steps. Sampling strategy is an important step in the overall process. Care must be taken to assure that the samples collected are representative of the environmental medium and that they are collected without contamination. There is an extensive list of test methods for water analysis (Tables 8.2, 8.3, and 8.4), which includes numerous modifications of the original methods, but most involve alternative extraction methods developed to improve overall method performance for the analysis. Solvent extraction methods with hexane are also in use. 

Producing data that cannot be compared directly with other total petroleum hydrocarbons data or guidelines because one data set is the result of a Soxhlet extraction method and the other reflects a sonication or other alternative extraction method. 

Much of the current interest in using analytical-scale SFE systems comes from the need to replace conventional liquid solvent extraction methods with sample preparation methods that are faster, more efficient, have better potential for automation, and also reduce the need for large volumes of potentially hazardous liquid solvents. The need for alternative extraction methods is emphasized by current efforts to reduce the use of methylene chloride as an extraction fluid for environmental sample preparation [158]. The potential for applying SFE to a wide variety of environmental and biological samples for both qualitative and quantitative analyses is widely described in reviews [159-161] and the references therein. Analytical-scale SFE is most often applied to relatively small samples (e.g., several grams or less). 

Alternative extraction methods [20, 35], oximation [9, 35], and derivatization agents [26] are available, but will not be discussed further in this chapter. 

Solid-phase extraction (SPE) it is widely accepted as an alternative extraction/clean up method [39]. SPE has been used for the extraction of PCBs in various types of human milk. Milk powder and evaporated milk were constituted with water prior to extraction. The milk sample was mixed with 5mL of water and 10 mL of methanol and sonicated, followed by passing the sample through the column. 

Since the pioneering work of Siddall, /V./V-dialkyl amides have been evaluated extensively as alternative extractants to TBP (200, 201). The salient features of amides as extractants are (i) low volume of secondary waste generated (completely incinerable), (ii) innocuous nature of chemical and radiolytic degradation products (better decontamination from fission products andregeneration/clean up easier), (iii) low aqueous-phase solubility, (iv) final U and Pu products streams are free of P contamination, and (v) ease of synthesis. However, LOC values of U and Pu as well as viscosity are... 

Blake, C.A., Davis, W., Schmitt, J.M. 1963. Properties of degraded TBP-Amsco solutions and alternative extractant-diluent systems. Nucl. Sci. Eng. 17 626-637. 

Alternatively, extract exchanged into 2-propanol derivatized with pentaflu-orobenzyl bromide, and determined by GC-ECD. 

Alternatively, extracted with methylene chloride by LLE extract concentrated and analyzed by a GC using a PID, FID, ECD, or GC/MS. 

Water Condensates. When stack gas was cooled during sampling, water vapor condensed. The organic components in these condensates were extracted with methylene chloride. Diethyl ether, pentane and isooctane were used as alternative extraction solvents when subsequent gas chromatographic determinations required the use of electron capture detectors. 

In contrast to alkamides, alternative extraction solvents such as SF carbon dioxide appear to be ineffective as an extraction solvent for CAP removal (Catchpole et al., 2002 Sun et al., 2002). Conditions evaluated by these researchers include pressures of 31 - 55 MPa and temperatures between 41 and 60°C. In both studies, ethanol was used as a solvent modifier, but the supercritical carbon dioxide was not modified sufficiently to promote the extraction of CAP. The addition of 10% methanol to the supercritical carbon dioxide at 25 MPa and 60°C was sufficient to promote the extraction of rosmarinic acid, a compound with similar structure features as cichoric acid (Bicchi et al., 2000). Thus, additional work is needed to determine if SFE can be used as a method to remove CAP. 

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