Specialized metallurgical processes – compositions for use therei – Processes – Free metal or alloy reductant contains magnesium
Reexamination Certificate
1998-11-04
2001-01-23
King, Roy V. (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Processes
Free metal or alloy reductant contains magnesium
C423S226000, C524S424000, C526S245000, C526S329400, C526S328500, C526S244000
Reexamination Certificate
active
06176895
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to polymers and polymer compositions useful for the extraction and separation of metals and metalloids (including complexes thereof) with a carbon dioxide fluid, along with methods of using the same.
BACKGROUND OF THE INVENTION
Supercritical fluids have received considerable attention as extraction solvents primarily owing to their desirable mass transfer characteristics Hawthorne, S. B.,
Anal. Chem.
62:633A-642A(1990). Carbon dioxide has received particular interest as a replacement solvent in extraction McHugh, M. A. and Krukonis, V. J.,
Supercritical Fluid Extraction: Principles and Practice,
2
nd
ed., Butterworth-Heinemann, Newton, Mass. (1994). Carbon dioxide is nontoxic, nonflammable, relatively inert, relatively inexpensive on a per extraction basis, and generally environmentally innocuous as compared with typical, often toxic, organic solvents.
One area of interest for the application of carbon dioxide is the reduction of contamination from processes involving metals which is a major environmental challenge. A first aspect of this area involves the remediation of legacy waste discharged into the environment and contained in storage. A second aspect of this area involves developing new environmentally friendly processes upstream which eliminate metal contamination sources. Typical metal solvent extraction techniques used for both remediation and processing involve the generation of additional solvent waste streams. Herein lies an opportunity to affect both ongoing processes involving metals and decontamination methods by taking advantage of carbon dioxide as an ideal replacement solvent.
Carbon dioxide is, however, a nonpolar solvent and consequently not capable of dissolving highly polar species such as metal ions. In traditional solvent extraction systems, chelating agents are utilized to bind the metal ions forming neutral metal complexes capable of dissolving in nonpolar organic solvents. As a nontraditional solvent, carbon dioxide poses its own difficulties with regard to appropriate chelating agents to achieve solubility of metal species. The vast majority of the work in this area has focused on utilizing conventional solvent extraction chelating agents such as dithiocarbamates, &bgr;-diketones, crown ethers, and organophosphorous compounds U.S. Pat. No. 5,087,370, U.S. Pat. No. 5,221,480, U.S. Pat. No. 5,356,538, U.S. Pat. No. 5,770,085, U.S. Pat. No. 5,730,874, U.S. Pat. No. 5,606,724, U.S. Pat. No. 5,561,066, Saito et al, Bull. Chem. Soc. Jpn. 63:1532-1534 (1990), and Smart et al,
Ind. Eng. Chem. Res.
36:1819-1826 (1997). Typically a large excess of the chelating ligand or a cosolvent is required. UO
2
(NO
3
)
2
.2TBP appears to be an isolated example of one particularly highly CO
2
-soluble complex Carrott, M. J. et al
Chem. Commun.
373-374 (1998). When TBP was used in a more general study for the extraction of lanthanides, greater than 10% TBP in CO
2
as a solvent modifier was necessary to effect extractions higher than 25% Laintz, K. E. et al,
Anal. Chem.
66:2190-2193. Fluorinated analogs of dithiocarbamate and &bgr;-diketone chelating agents have shown enhanced solubility in CO
2
over their hydrocarbon counterparts although a large excess of ligand is still necessary to improve extraction efficiency. This enhanced solubility is likely related to the enhanced volatility of metal complexes with fluorinated ligands. Lagalante, A. F. et al
Inorg. Chem.
34:5781-5785 (1995). In some instances liquid CO
2
may serve as a more attractive medium due to lower operating pressures.
Several studies have addressed the performance of chelating agents in liquid carbon dioxide extraction of metals. Laintz et al
Anal. Chem.
70:440-404 (1998) found that liquid and supercritical carbon dioxide at the same density have comparable efficiencies for the extraction of nickel and zinc from spent plating bath solutions using acetylacetone and its fluorinated analog. Yadzi and Beckman U.S. Pat. No. 5,641,887 have developed a number of picolylamine, dithiol, and dithiocarbamate derivatives of Krytox acids that are soluble in liquid carbon dioxide. Similarly derivatized polysiloxanes were found to be much less soluble in CO
2
than the fluorinated polyether Krytox chelates.
Clearly, both liquid and supercritical carbon dioxide have desirable qualities as extraction solvents. Therefore, the need for chelating agents useful for carbon dioxide systems, especially for relatively low pressure operations, is evident.
SUMMARY OF THE INVENTION
A first aspect of the present invention is a composition useful for the extraction of metals and metalloids. The composition comprises (a) carbon dioxide (preferably liquid or supercritical carbon dioxide); and (b) a polymer in the carbon dioxide, the polymer having bound thereto a ligand that binds the metal or metalloid; with the ligand bound to the polymer at a plurality of locations along the chain length thereof (i.e., a plurality of ligands are bound at a plurality of locations along the chain length of the polymer). The polymer is preferably a copolymer, and the polymer is preferably a fluoropolymer such as a fluoroacrylate polymer.
A second aspect of the present invention is a method of extracting metals and metalloids. The method comprises the steps of (a) contacting a first composition containing a metal or metalloid to be extracted with a second composition, the second composition being as described above; and then (b) extracting the metal or metalloid from the first composition into the second composition. The first composition may be in any form, such as a solid, a liquid, a slurry, etc., and may be heterogeneous or homogeneous.
A third aspect of the present invention is a composition comprising: (a) carbon dioxide (preferably liquid or supercritical carbon dioxide); (b) a polymer in the carbon dioxide, the polymer having bound thereto a ligand that binds the metal or metalloid; with the ligand bound to the polymer at a plurality of locations along the chain length thereof; and (c) a metal or metalloid bound to the polymer by the ligand (i.e., a plurality of the metals or metalloids are bound to the polymer by virtue of a plurality of the ligands being bound to the polymer).
A fourth aspect of the present invention comprises a method for the separation of metals and metalloids from a carrier medium. The method comprises: (a) providing a composition comprising (i) carbon dioxide, (ii) a polymer in the carbon dioxide, the polymer having bound thereto a ligand that binds the metal or metalloid; with the ligand bound to the polymer at a plurality of locations along the chain length thereof, and (iii) a metal or metalloid bound to the polymer by the ligand; and then (b) separating the polymer from the carbon dioxide.
The present invention is explained in greater detail in the drawings herein and the specification below.
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DeSimone et al. “Synthesis of Fluoropolymers in Supercritical Carbon Dioxide”Sciencevol. 257 Aug. 1992 pp. 945-947.
International Search Report,PCT/US99/25969, Date of Mailing: Mar. 14, 2000.
Ashraf-Khorassani et al.; Separation of Metal-Containing Compounds by Supercritical Fluid Chromatography,Anal. Chem.59:17 2077-2081 (1987). No Month.
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Carrott et al.; High solub
Birnbaum Eva R.
DeSimone Joseph M.
McClain James B.
McCleskey T. Mark
Powell Kimberly R.
King Roy V.
McGuthry-Banks Tima
Myers Bigel Sibley & Sajovec P.A.
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