WO1995033541A1 - Extraction de metaux et metalloides de fluides - Google Patents

Extraction de metaux et metalloides de fluides Download PDF

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Publication number
WO1995033541A1
WO1995033541A1 PCT/US1994/006450 US9406450W WO9533541A1 WO 1995033541 A1 WO1995033541 A1 WO 1995033541A1 US 9406450 W US9406450 W US 9406450W WO 9533541 A1 WO9533541 A1 WO 9533541A1
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Prior art keywords
fluorinated
group
diketone
carbon dioxide
supercritical
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PCT/US1994/006450
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English (en)
Inventor
Chien M. Wai
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Idaho Research Foundation, Inc.
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Publication date
Application filed by Idaho Research Foundation, Inc. filed Critical Idaho Research Foundation, Inc.
Priority to EP94921262A priority Critical patent/EP0762918B1/fr
Priority to PCT/US1994/006450 priority patent/WO1995033541A1/fr
Priority to CA002191227A priority patent/CA2191227C/fr
Priority to DE69431260T priority patent/DE69431260D1/de
Priority to JP50079896A priority patent/JP2002508697A/ja
Priority to AU72052/94A priority patent/AU7205294A/en
Priority to KR1019960706769A priority patent/KR970703183A/ko
Publication of WO1995033541A1 publication Critical patent/WO1995033541A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
    • C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
    • C22B3/26—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D11/00—Solvent extraction
    • B01D11/02—Solvent extraction of solids
    • B01D11/0203—Solvent extraction of solids with a supercritical fluid
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D11/00—Solvent extraction
    • B01D11/02—Solvent extraction of solids
    • B01D11/0288—Applications, solvents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D11/00—Solvent extraction
    • B01D11/04—Solvent extraction of solutions which are liquid
    • B01D11/0403—Solvent extraction of solutions which are liquid with a supercritical fluid
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D11/00—Solvent extraction
    • B01D11/04—Solvent extraction of solutions which are liquid
    • B01D11/0403—Solvent extraction of solutions which are liquid with a supercritical fluid
    • B01D11/0407—Solvent extraction of solutions which are liquid with a supercritical fluid the supercritical fluid acting as solvent for the solute
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D11/00—Solvent extraction
    • B01D11/04—Solvent extraction of solutions which are liquid
    • B01D11/0492—Applications, solvents used
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/26—Treatment of water, waste water, or sewage by extraction
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/68—Treatment of water, waste water, or sewage by addition of specified substances, e.g. trace elements, for ameliorating potable water
    • C02F1/683—Treatment of water, waste water, or sewage by addition of specified substances, e.g. trace elements, for ameliorating potable water by addition of complex-forming compounds
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/20—Heavy metals or heavy metal compounds
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Definitions

  • This invention concerns extraction of metalloids and metals from solids and liquids, and is more particularly directed to a treatment process in which metals are efficiently extracted from waste material.
  • Waste treatment and disposal is an important social and economic issue.
  • An alternative detoxification process is to encapsulate contaminants in a container or insoluble matrix that prevents their entry into the environment. This approach still requires storage of the bulky matrix, and does not allow regeneration or reuse of the contaminants.
  • crown ethers such as crown ether carboxylic acids.
  • the inventors have found that these macrocyclic ethers have cavities that can selectively extract lanthanides and actinides by attracting these species with an ionized side chain. The metal ion is then inserted into the cavity of the macrocycle to form a chelate.
  • An unrelated solvent extraction method is fluid extraction, such as supercritical fluid extraction.
  • a supercritical fluid is typically one that is gaseous at ambient conditions, but which is maintained at a temperature and pressure above its critical temperature and pressure. Although materials may perform as solvents at sub-critical temperatures and pressures, fluids often perform better as solvents at supercritical conditions.
  • Supercritical solvents can be used to extract organic materials such as caffeine from coffee beans.
  • United States Patent No. 4,911, 94 l provides an example of supercritical carbon-dioxide extraction of caffeine in which green coffee beans are moved periodically through an extraction vessel and contacted with continuously flowing supercritical carbon dioxide.
  • U.S. Patent No. 4,898,673 shows a similar system in which soluble materials are continuously extracted from solids using supercritical carbon dioxide. The soluble solids are circulated in a closed-loop pipeline with the supercritical fluid.
  • Supercritical extraction of environmental wastes has not previously been suggested. This may be due to the relatively low solubility of metals and other non-organic materials in supercritical fluids.
  • Direct extraction of metal ions by supercritical carbon dioxide, for example, is inefficient because of the weak van der Waals interaction between metal ions and carbon dioxide. This weak interaction has apparently discouraged efforts to perform supercritical fluid extraction of metals from environmental wastes.
  • the present invention provides a method of extracting a metal species (including lanthanides and actinides) from a solid or liquid by exposing the solid or liquid to a fluid solvent, particularly a supercritical fluid solvent, that contains a chelating agent.
  • a fluid solvent particularly a supercritical fluid solvent
  • the fluid or supercritical fluid solvent and chelating agent are exposed to the solid or liquid for a sufficient period of time to form a chelate between the metal and chelating agent that is soluble in the fluid.
  • the fluid or supercritical fluid then is removed from the solid or liquid with the solubilized metal chelate dissolved in the fluid.
  • the metal chelates subsequently can be precipitated from the fluid. For example, if the fluid is supercritical, then the metal chelates can be precipitated by reducing the pressure of the supercritical fluid.
  • the chelating agent can also be regenerated for reuse. The resulting process is an efficient, cost-effective method for removing metals from the environment without using environmentally harmful extraction solvents.
  • the chelating agents can be any agent that forms a chelate with the metal being extracted, wherein the chelate is soluble in the fluid or supercritical fluid solvent.
  • suitable chelating agents include dithiocarbamates, ionizable crown ethers, ⁇ -diketones and trialkyl phosphates, as shown below.
  • the chelating agent is fluorinated to enhance the solubility of the metal chelate in supercritical carbon dioxide.
  • fluorinated chelating agents are:
  • the solubilities of some halogenated metal chelates in supercritical carbon dioxide, and in particular the fluorinated metal chelates, are enhanced by two to three orders of magnitude relative to the corresponding non-fluorinated metal chelates.
  • the solubility of Cu(FDDC) 2 in supercritical carbon dioxide is about 1 x 10 moles per liter at 50 oC and 100 atmospheres, whereas the solubility of the non-fluorinated compound, Cu(DDC) 2 , is less than 1 x 10 -6 moles per liter under the same conditions.
  • Fluorinated chelating agents have been found to greatly enhance the efficiency of metal extraction in supercritical carbon dioxide. As a result, fluorinated chelating agents currently are preferred chelating agents useful for practicing the present invention.
  • a modifier is added to the supercritical fluid to further enhance the efficiency of the extraction method by increasing the solubility of the metal chelate in the supercritical fluid.
  • Carbon dioxide for example, is a relatively non-polar solvent. Its polarity can be increased by adding a more polar solvent to the supercritical carbon dioxide.
  • more polar solvents are low to medium boiling point alcohols or esters, such as methanol. The alcohol or ester increases the polarity of the supercritical fluid, enhances the solubility of the metal chelate in the fluid, and further improves the extraction efficiency of the method.
  • lonizable crown ethers of a given ionic diameter can, for example, selectively remove lanthanides and actinides from the waste material.
  • Suitable crown ethers include dibenzo crown ether derivatives of a hydroxamic acid represented by the formula: wherein X is a dibenzo crown ether of the formula dibenzo [13 + 3m]-crown-[4 + m] ether, and m is an integer of from 0 to about 5; n is an integer from 0 to 6; and R 1 is H or a lipophilic hydrocarbyl group having from 1 to about 18 carbon atoms that is selected from the group consisting of alkyl, cycloalkyl.alkenyl and aryl groups.
  • the ionizable crown ether has the chemical formula
  • X is OH or NHOH
  • R 2 is alkyl, fluorinated alkyl, phenyl or fluorinated phenyl
  • R 3 is alkyl, fluorinated alkyl, phenyl or fluorinated phenyl
  • R 4 is H or F
  • R 5 is H or F
  • n is 1 to 3.
  • the chelating agent is a dithiocarbamate having the seneral formula
  • R 6 and R 7 are independently alkyl or aromatic groups that may contain one or more fluorine atoms.
  • the ligand is called diethyldithiocarbamate (DDC), and it forms a metal chelate such as
  • R 6 and R 7 are both CF 3 CH 2
  • the ligand is called bis(trifluoroethyl)dithiocarbamate
  • the resulting metal chelate has a structure such as
  • a system for treating waste material containing metal species.
  • the material is placed in a container through which the fluid or supercritical fluid is passed to solubilize the metal species.
  • the fluid or supercritical fluid and solubilized metal species are removed from the container to separate the metal species from the waste material.
  • a chelating agent is dissolved in the fluid to form chelates with the metal species that are soluble in the fluid.
  • the chelates are fluorinated to further increase their solubility and enhance the extraction efficiency of the separation method.
  • Polar solvents such as alcohols or esters can be added to the supercritical fluid to also enhance solubility of the metal chelate in the supercritical fluid.
  • Fluid or supercritical fluid can be flowed continuously through the waste material, or exposed to the material in a discontinuous batch process.
  • a supercritical fluid is flowed through a chelating agent before the waste material is exposed to the fluid to dissolve the chelating agent in the fluid.
  • the pressure on the supercritical fluid can be reduced to below supercritical levels such that the fluid becomes a gas and the metal chelates are precipitated from the system.
  • the pure metal can then be collected, and the chelating agent recycled to further extract the waste material.
  • the chelating agent can be separated from the metal, for example, by 0.1 M or more concentrated nitric acid with a pH less than or equal to 1.
  • the present invention also provides a method for extracting a metalloid or metal species from a solid or liquid comprising exposing the solid or liquid to a fluid solvent, particularly a supercritical fluid, containing a ⁇ -diketone chelating agent for a sufficient period of time to form chelates between the agent and species that are solubilized in the fluid solvent.
  • a preferred supercritical fluid is supercritical carbon dioxide.
  • the fluid typically is separated from the solid or liquid after the chelate is solubilized in the fluid.
  • Preferred ⁇ -diketones include halogenated ⁇ diketones, particularly fluorinated ⁇ -diketones.
  • the fluid solvent may further comprise a secondary modifying solvent, such as medium boiling point alcohols and esters, particularly methanol.
  • the ⁇ -diketone may be represented by the formula
  • R 1 and R 2 are independently selected from the group consisting of lower alkyl, fluorinated lower alkyl and thenoyl groups.
  • lower alkyl refers to compounds having ten or fewer carbon atoms, and includes both straight chain and branched chain compounds.
  • R 1 may be selected from the group consisting of methyl, trifluoromethyl, ethyl, fluorinated ethyl, propyl, fluorinated propyl, butyl and fluorinated butyl
  • R 2 may be selected from the group consisting of methyl, trifluoromethyl, ethyl, fluorinated ethyl, propyl, fluorinated propyl, butyl, and fluorinated butyl.
  • halogenated, lower alkyl group such as a fluorinated ethyl group
  • a halogenated, lower alkyl group means that at least one of the hydrogen atoms present on the alkyl group is replaced with a halogen atom, preferably a fluorine atom.
  • a "halogenated lower alkyl group” also can refer to compounds wherein all of the hydrogen atoms have been replaced with halogens, preferably fluorine atoms.
  • An example of such a halogenated lower alkyl group would be a trifluoromethyl group.
  • suitable ⁇ -diketones include acetylacetone, trifluoroacetylacetone, hexa-fluoroacetylacetone, thenoyltrifluoroacetylacetone and heptafluorobutanoylpivaroylmethane.
  • Especially preferred ⁇ - diketones include trifluoroacetylacetone, hexa-fluoroacetylacetone, thenoyltrifluoroacetylacetone and heptafluoro-butanoylpivaroylmethane.
  • a preferred method according to the present invention comprises exposing a solid or liquid containing metal or metalloid ions to carbon dioxide, particularly supercritical carbon dioxide, containing a ligand selected from the group consisting of fluorinated ⁇ -diketones, trialkyl phosphates, trialkylphosphine oxides, and mixtures thereof. At least of the fluorinated ⁇ -diketone, trialkyl phosphate and trialkylphosphine oxides forms chelates with the metal or metalloid species. The chelates are soluble in the supercritical carbon dioxide.
  • the fluorinated ⁇ -diketone may be represented by the formula
  • R 1 and R 2 are independently selected from the group consisting of fluorinated lower alkyl and fluorinated thenoyl groups.
  • the trialkyl phosphate may be represented by the formula
  • R 3 , R 4 and R 5 are independently selected from the group consisting of lower alkyl groups, and the trialkylphosphine oxide may be represented by the formula
  • R 6 - R 8 are independently selected from the group consisting of lower alkyl groups.
  • the ⁇ -diketone may be selected from the group consisting of trifluoroacetylacetone, hexafluoroacetylacetone, thenoyltrifluoroacetylacetone and heptafluoro- butanoylpivaroylmethane, and R 3 , R 4 and R 5 may be selected from the group consisting of n- butyl and n-octyl.
  • a modifying solvent also can l>e used with this particular embodiment of the present invention.
  • the modifying solvent may be selected from the group consisting of lower alkyl alcohols, with a particular embodiment of the modifying solvent being methanol.
  • the present invention also provides an extraction solvent, comprising a supercritical fluid and a ⁇ -diketone chelating agent.
  • the solvent preferably is supercritical carbon dioxide
  • the ⁇ -diketone preferably is a fluorinated ⁇ -diketone
  • the solvent preferably further comprises a trialkyl phosphate or a trialkylphosphine oxide chelating agent.
  • Another object of the invention to provide such an improved method that allows efficient and biologically compatible extraction of metals from the environment.
  • Another object is to provide such an improved method that allows selectivity as to the type of metal extracted by the system.
  • Another object is to provide such an improved method that can selectively extract lanthanides and actinides.
  • Another object of this invention is to provide such an improved method that is efficient and economical compared to many other extraction processes.
  • Another object of this invention is to provide a process for the selective removal of ions from acidic waste systems.
  • Another object of this invention to provide a process for the efficient extraction of metals and metalloids from solid and liquid materials using a ⁇ -diketone, particularly a fluorinated ⁇ -diketone.
  • FIG. 1 is a schematic view of a system for using supercritical fluid to extract
  • FIG. 2 is a graph illustrating the rate of extraction of Cu 2 + from water using supercritical CO 2 with varying densities at 35 °C saturated with
  • FIG. 3 is a chromatogram produced using a superbond capillary column injected at 100°C oven temperature with a hold time of 6.5 minutes at 100 atm followed by a 4.0 atm/minute ramp.
  • FIG. 4 is a chromatogram as in FIG. 3 showing peaks for (a) NaFDDC, (b) Zn(FDDC) 2 , (c) Ni(FDDC) 2 , (d) Co(FDDC) 3 , (e) Fe(FDDC) 3 , (f) Hg(FDDC) 2 , (g) As(FDDC) 3 , (h) Sb(FDDC) -, (i) Bi(FDDC) 3 .
  • FIG. 5 is a graph comparing solubilities of an unfluorinated lariat crown ether with fluorinated lariat crown ethers.
  • FIG. 6 is a schematic drawing of a waste treatment system in accordance with the present invention.
  • FIG. 7 is a phase diagram for carbon dioxide.
  • the present invention concerns a method for extracting metalloids or metals from solid or liquid materials by exposing the material to a fluid solvent or a supercritical fluid solvent.
  • the fluid or supercritical fluid preferably contains either a chelating agent that forms a metal chelate with the extracted metal, or the fluid may include a ligand and a solubility- enhancing agent.
  • the chelate is soluble in the fluid, particularly supercritical fluids, which allows efficient extraction of the chelate from the material.
  • the present invention is suitable for removing many different types of metalloids or metals from liquids or solids.
  • Metalloids are elements with both metallic and non-metallic properties, and include arsenic, selenium and tellurium.
  • a metal is an element that forms positive ions in solutions, and produces oxides that form hydroxides rather than acids with water.
  • Metals include alkali metals, alkali-earth metals, transition metals, noble metals (including the precious metals gold, platinum and silver), rare metals, rare-earth metals (lanthanides), actinides (including the transuranic metals), light metals, heavy metals, synthetic metals and radioactive metals.
  • extraction methods for removing lanthanides and actinides (collectively referred to as the f-group elements from the filling of their 4f and 5f orbitals) as well as transition metals such as copper.
  • the f group elements are commonly produced by nuclear fission reactions, and the actinides are radioactive. Transition metals are commonly used or produced in many industrial processes and products, such as mineral production or fly ash.
  • the present invention also provides specific examples of extraction methods for radioactive metals, such as uranium, particularly the extraction of such metals from acidic solutions. This provides an attractive alternative to the PUREX process for recovering uranyl ions from acidic solutions.
  • Suitable fluids and/or supercritical fluids for use in the present invention include carbon dioxide, nitrogen, nitrous oxide, methane, ethylene, propane and propylene.
  • Carbon dioxide also is a preferred solvent because it is abundantly available and relatively inexpensive.
  • FIG. 7 is a phase diagram for carbon dioxide which shows the conditions necessary to produce either subcritical liquid carbon dioxide or supercritical carbon dioxide. Although all conditions above the triple point (T P ) produce a carbon dioxide fluid solvent effective for practicing the present invention, the preferred carbon dioxide solvent is supercritical. Therefore the conditions typically must be above the critical temperature and pressure for carbon dioxide. However, virtually any conditions that are above the critical point are acceptable for producing a supercritical carbon dioxide fluid solvent useful for practicing the extraction process of the present invention.
  • the fluids may be used either individually or in combinations, as mixed fluids or supercritical fluid solvents. Examples of other fluids, and their critical temperature and pressure, are shown in the following Table I:
  • a modifier may be added to the fluid, including supercritical fluids, to improve the solvent characteristics thereof.
  • the most useful modifiers are the low to medium boiling point alcohols and esters. Typical modifiers include methanol, ethanol, ethyl acetate and the like.
  • the modifiers typically are added to the fluids at proportions of between about 0.1 % and 20.0% by weight.
  • the modifiers contemplated for use herein are most typically not supercritical fluids at the disclosed operating conditions. Rather, the modifiers are simply dissolved in the fluid solvents, including the supercritical fluid solvents, to improve their solvent properties.
  • the chosen enhancer is combined with a supercritical fluid at the described proportions prior to feeding the supercritical fluid to the extraction vessel.
  • the supercritical fluid is fed to the extraction vessel without the enhancer. The enhancer is then introduced into the extraction vessel and thereby combined with the supercritical fluid.
  • Some chelating agents that may be useful for solubilizing metals in supercritical fluids include:
  • the sample bulk extraction device of FIG. 1 includes a source 20 of supercritical CO 2 that directly extracts Cu ions from aqueous solution.
  • the supercritical CO 2 was delivered from a high pressure syringe pump 22 and passed through solid lithium bis(trifluoroethyl)dithiocarbamate (FDDC) which was contained in a stainless steel, high pressure extraction vessel 24.
  • FDDC solid lithium bis(trifluoroethyl)dithiocarbamate
  • the supercritical CO 2 containing dissolved FDDC was subsequently introduced to a second extraction vessel 26 fitted with quartz windows and containing an aqueous solution 28 of Cu(NO 3 ) 2 below a SCF CO 2 phase. Extraction of Cu was monitored by UV- Visible spectroscopy as the formation of the CO 2 soluble complex Cu(FDDC) 2 , the structure of which is shown below.
  • a continuous extraction process was set up using the apparatus of FIG. 1 in which a high pressure recirculating pump was installed in line with the extraction system. Quantitative extraction occurred even more rapidly than in the bulk system with quantitative extraction occurring in less than 5 minutes at 35 °C.
  • This example illustrates a process for extracting metals and/or metalloids from a solid matrix.
  • the same apparatus used in example I was also used in the extraction of Cu ions adsorbed on a solid matrix.
  • solid Cu(NO 3 ) 2 adsorbed on silica (SiO 2 ) was placed in the second extraction vessel.
  • Supercritical CO 2 containing dissolved ligand, FDDC was then introduced into the cell.
  • Extraction efficiency was again monitored spectroscopically as Cu(FDDC) 2 dissolved into the supercritical CO 2 .
  • Initial extraction rates were again very rapid. In about 20 minutes the CO 2 phase was saturated with dissolved metal complex. In this case approximately 80% of the Cu ions could be extracted at a final fluid density of 0.55 g/cm 3 .
  • the metal chelate could be collected in whole by precipitation from the supercritical CO 2 by decreasing the pressure of the system. It is also seen that the present invention is useful for removing contaminants from a complex matrix, which is either a solution or solid sample in which are present many different species (including organic and inorganic species).
  • This example describes the use of fluorinated chelating agents for SFE according to the present process.
  • fluorination of complexing agents yielded enhanced solubility behaviors of the metal chelates in supercritical CO 2 .
  • Fluorination of sodium diethyldithiocarbamate (DDC) to form sodium or lithium bis(trifluoroethyl)-dithiocarbamate (FDDC) was found to increase the solubilities of the metal-diethyldithiocarbamates by almost 3 orders of magnitude.
  • DDC sodium diethyldithiocarbamate
  • FDDC lithium bis(trifluoroethyl)-dithiocarbamate
  • Cu(DDC) 2 has a UV-Visible determined solubility in supercritical CO 2 of (1.1 ⁇ 0.2) x 10 -6 mol/L.
  • the solubility of Cu(FDDC) 2 in supercritical CO 2 was determined to be (9.1 ⁇ 0.3) x 10 -4 mol/L.
  • Another example of increased solubility in supercritical CO 2 was obtained with the ⁇ -diketone acetylyacetonate (AC AC).
  • the solubility of Cu(acac) 2 in supercritical CO 2 was substantially increased by forming Cu(HFACAC) 2 , which is the hexafluoroacetyl acetonate.
  • the present inventors have found that fluorination of chelating agents favors the extraction of fluorinated metal chelates in supercritical CO 2 .
  • the behaviors of metal fluorinated diethyldithiocarbamate (FDDC) complexes in supercritical fluid chromatography (SFC) have not previously been reported.
  • This example illustrates the separation of arsenic DDC and FDDC complexes in SFC using CO 2 , as a mobile phase.
  • a Lee Scientific Model 602 supercritical fluid chromatograph with a Neslab RTE- 100 constant temperature bath was used for all analysis reported in this example. This system was equipped with a timed-split rotary injection valve and an FID. All chromatograms were run using supercritical CO 2 as the mobile phase (Matheson) and a 5-meter 100-um ID by 195- um OD SB-Methyl- 100 Superbond capillary column (Lee Scientific). The chromatographic signals were recorded and processed using a HP 3390A integrator. The temperature and density conditions for the analysis were computer controlled and are reported below.
  • NaDDC diethyldithiocarbamate
  • Ammonium acetate buffer was prepared by mixing 120 g of glacial acetic acid (J.T. Baker Ultrapure Reagent) and 134 g of concentrated NH 4 OH (Aldrich A.C.S. Reagent) and diluting to 1 liter. The pH value was adjusted by drop wise addition of HNO 3 and/or NH 4 OH.
  • Deionized water was prepared by passing distilled water through an ion exchange column (Barnstead ultrapure water purification cartridge) and a 0.2-um filter assembly (Pall Corp, Ultipor DFA).
  • Sodium bis(tri_luoroethyl)amine was purchased from PCR Research
  • the metal-DDC and FDDC complexes were prepared by adding an excess amount of ligand to the metal solutions at the pH indicated in Anal. Chem 54:2536(1982). The resulting precipitates were extracted into chloroform, and the organic phase was washed with deionized water after phase separation. Purification of the metal complexes was done using recrystallization from a chloroform/ethanol solution (1: 1 v/v). Other chemicals used in the synthesis, including sodium amide, carbon disulfide, and potassium hydroxide were all obtained from Aldrich Chemical Company. All containers used in the experiments were acid washed, rinsed several times with deionized water, and dried in a class 100 clean hood.
  • the conditions used for chromatographic separation were an oven temperature of 100°C with initial CO 2 pressure of 100 atm, followed by a 6.50 min hold time with a pressure ramp of 4.0 atm/min to a final pressure of 200 atm.
  • Sample injection time was 0.1 seconds, which amounts to a calibrated 80 nL sample injection.
  • Flame ionization detector (FID) temperature was 325 °C.
  • As(DDC) 3 , Ni(DDC) 2 , Pb(DDC) 2 , and Zn(DDC) 2 were possible.
  • these particular metal complexes apparently have a lower solubility in supercritical CO 2 .
  • FIG. 3 illustrates this point with a comparison of a sample analyzed by capillary SFC containing the same concentration (6 x 10 -4 M) of As(FDDC) 3 and As(DDC) 3 with docasane (C 22 H 46 ) being used in this case as an internal standard.
  • the As(DDC) 3 peak is typical of metal-DDC complexes, being broader and less reproducible.
  • As(FDDC) 3 peak is sharp and well-defined, with a shorter retention time relative to the corresponding DDC complex.
  • the chromatographic results of As(FDDC) 3 were reproducible without any of the column contamination problems that were encountered using DDC.
  • FIG. 4 shows a series of metal -FDDC complexes that were separated and detected, which includes Zn, Ni, Co, Fe, Hg, As, Sb, and Bi.
  • Peak (a) is NaFDDC
  • peak (b) is Zn(FDDC) 2
  • peak (c) is Ni(FDDC) 2
  • peak (d) is Co(FDDC) 3
  • peak (e) is Fe(FDDC) 3
  • peak (f) is Hg(FDDC) 2
  • peak (g) is As(FDDC) 3
  • peak (h) is Sb(FDDC) 3
  • peak (i) is
  • Bi(FDDC) 3 The valence of the metal ionic species is the same as the number of FDDC ligands in the chelate. This chromatograph shows the ability of the present method to separate and detect arsenic from a mixture of metal complexes. The detection limit of these metal chelates is generally in the order of 1 ppm.
  • the extraction procedure serves as a
  • preconcentration step for SFC analysis With a preconcentration factor of 10 to 100, this technique can be used for trace analysis.
  • the percentages of recovery of these trace metals using FDDC extraction are generally ⁇ 95%.
  • This example describes the calculation of the stability constants for certain chelates useful for the present invention. Fluorination of diethyldithiocarbamate has been shown to increase the stability of metal chelates.
  • a numerical value for the enhancement of the stability constant of the arsenic complex was estimated using a competition experiment where As 3+ was added in a sub-stoichiometric amount to a mixture of equal amounts of Na- DDC and Na-FDDC. In this experiment, the concentration of As 3+ in the aqueous phase was 2.1 x 10 M and the concentrations of each ligand were 2.1 x 10 M. After extraction, the organic phase was analyzed by supercritical fluid chromatography (SFC) to determine the relative amounts of As(FDDC) 3 .
  • SFC supercritical fluid chromatography
  • K 1 /K 2 ([As(FDDC) 3 ]/[As(DDC) 3 ])([DDC-]/[FDDC -]) 3 (3)
  • K 1 can be calculated from equation (3).
  • the value of K 1 determined from this experiment is 2.1 x 10 24 .
  • the chelating agent is fluorinated to improve the solubility of the metal chelate in the supercritical fluid and enhance metal extraction.
  • the chelating agents in this example are DDC, FDDC, "H-crown”, “F2-crown”, and “F6-crown. " The structural formulae of these agents are:
  • H-crown refers to the non-fluorinated molecule
  • F2-crown has two added fluorine atoms
  • F6-crown has six added fluorine atoms.
  • Table III shows increases in solubility at the lower pressure/densities of CO 2 .
  • the solvation power of CO 2 at the higher pressures/densities increases significantly such that it is much more like a regular liquid organic solvent at those pressures.
  • the solubility enhancement from fluorine diminishes. This is advantageous because the solubility increase from fluorination occurs at moderate, easily achievable conditions.
  • Dithiocarbamate chelating agents are somewhat nonselective for the metal with which a chelate is formed. Fluorination of a dithiocarbamate chelating agent, however has a greater effect on increasing the solubility of transition metal chelates such as Cu, Ni, and Co than on alkali earth metals such as Na.
  • the crown ethers are general ly known as macrocycl ic polyethers. Many related compounds have been made involving heterocyclic rings containing 12 to 60 atoms. Crown ethers are particularly useful as chelating agents because they can be made selective for particular l igands. There are, for example, optimum polyether ring sizes for different alkal i metal cations. A 15 to 18 member ring has an optimal cavity size for chelating a cation having the radius of sodium; an 18 member ring is optimal for chelating potassium; and an 18 to 21 member ring is most suitable for cesium.
  • crown ethers with pendant carboxylate functional groups are quite efficient and selective for extracting trivalent lanthanide ions.
  • the negatively charged carboxylate group is believed to attract the positively charged lanthanide ions, which are then inserted into a ring having the appropriate cavity size.
  • the cavity size is preferably a 16 member crown ether ring.
  • the lariat crown ether system also shows high extraction efficiency for Lu 3+ (ionic radius 0.93 ⁇ ), and even has a selectivity for Lu 3+ over La 3+ by as much as an order of magnitude depending on the solvent.
  • the observed selectivity is bel ieved to result from smal l differences in ionic radius and bonding of the lanthanides with the ligand.
  • the crown ethers of the present invention include many hydroxamic acids that are described by the fol lowing empi rical formula:
  • n is an integer of from 0 to 6
  • X is a dibenzo crown ether of the formula dibenzo- [13 + 3m] -crown- [4 + m] -ether wherein m is an integer of from 0 to about 5 or so and R 8 is a lipophi lic group which imparts lipophi licity to the hydroxamic acid derivative.
  • the size of the dibenzo crown ether may be varied provided the metal to be extracted fits in the ring such that the donor atoms coordinate to the metal (or to water associated with the metal ) .
  • crown ethers in which the ring size of the crown is too large for a satisfactory host/guest interaction are not suitable.
  • Some preferred dibenzo crown ethers are those in which m is 0, 1 or 2, and are, respectively, dibenzo-13-crown-4 ether, dibenzo-16-crown-5 ether, and dibenzo-19-crow ⁇ -6 ether.
  • the hydroxamic acid derivatives of this invention are preferably lipophi l ic in order to minimize or even prevent the chelating agent from partitioning in the aqueous phase.
  • R may be hydrogen, i t is preferably a lipophi l ic moiety.
  • R is preferably a hydrocarbyl group having from 1 to about 18 carbon atoms and is selected from the group consisting of alkyl , cycloalkyl , alkenyl and aryl groups. These groups may also be substituted with other functional groups. For example, if aryl is phenyl , the phenyl may be substituted with electron withdrawing groups such as fluorine, or it may be substituted wi th electron donating groups such as methoxy.
  • the phenyl group may be completely substi tuted with f luorine, such that R is C 6 F 5 or it may be a 3,5-di -trifluoromethyl phenyl group.
  • Fluorinated derivatives of hydroxamic acid are bel ieved to be useful in the extraction of lanthanide and actinide metal ions using supercritical carbon dioxide.
  • the solubi lities of hydroxamic acid chelates is relatively low in supercritical CO 2 . Hence, side chain lipophi licity and fluorination are preferred to increase solubi l ity of the chelate in supercritical CO 2 .
  • R groups of from about 6 to about 10 carbon atoms wi l l sufficiently increase l ipophi l ici ty and maximize solubi l ity of the chelate in supercritical CO 2 . It is also bel ieved that higher extraction efficiency is achieved with R groups of greater lipophi licity, that is, where R is a longer chain hydrocarbon, and that hydroxamic acids in which the R group is aryl are often more selective.
  • the lipophi licity of the side chain should be less important for a more polar supercritical fluid such as N 2 O.
  • dibenzo ether derivatives of hydroxamic acid of the present invention are described by the following empirical formula:
  • Y is a member selected from the group consisting of (CH 2 ) 3 , [[CH 2 CH 2 O n CH 2 CH 2 ] wherein n is an integer of from 1 to about 4, and CH 2 CONHCH 2 CH 2 NH COCH 2 ; and R 9 and R 10 , which may be the same or different, are selected from the group consisting of H and a hydrocarbyl group having from 1 to about 18 carbon atoms, which is selected from the group consisting of alkyl , cycloalkyl , alkenyl and aryl groups.
  • the R groups are preferably lipophi lic when the supercritical fizid is CO 2 .
  • these groups may be substituted with other functional groups. Fluorination of these groups would also be preferred when the supercritical fucid is relatively non-polar (such as supercritical carbon dioxide) .
  • the present invention provides a bis-dibenzo crown ether derivative of a hydroxamic acid represented by the fol lowing empi rical formula: wherein X is a dibenzo crown ether of the formula dibenzo- [13 + 3m] -crown- [4 + m] -ether and m is an integer of from 0 to about 5 or so, and R 11 is hydrogen or a lipophi lic hydrocarbyl group having from 1 to about 18 carbon atoms and is selected from the group consisting of alkyl , cycloalkyl, alkenyl and aryl groups.
  • the R groups may be substi tuted wi th other functional groups, preferably f luorine.
  • the dibenzo crown ether X may be the same or different and its size may be varied provided the metal to be extracted fits into the ring to permit chelation.
  • the preferred dibenzo crown ethers are those in which m is 0, 1 or 2, and are, respectively, dibenzo- 13-crown-4 ether, dibenzo- 16- crown- 5 ether and dibenzo- 19-crown-6 ether. Fluorination of the benzene rings is especial ly preferred when the crown ether is to be used wi th a relatively non-polar supercri tical fucid such as CO 2 .
  • the present invention further provides a tridentate derivative of a hydroxamic acid represented by the formula:
  • R 12 or R 13 may be H, bu t preferably R 12 or R 13 is a l ipophi l ic moiety having of from 1 to about 18 carbon atoms and is selected from the group consisting of alkyl, cycloalkyl, alkenyl and aryl groups.
  • the R 12 , R 13 groups may be the same or different moieties, and may be substituted with other functional groups, such as f luorine.
  • a supercritical fucid such as carbon dioxide gas
  • CO 2 gas reservoi r 52 which is connected by a conduit 54 containing a valve 55 to a pressurization unit 56 that increases the pressure on the gas to greater than 73 atmospheres at a temperature greater than 32°C to form supercritical carbon dioxide.
  • the supercritical CO 2 then travels through a valve 57 and conduit 58 to a reservoir 60 that holds a sol id or l iquid chelating agent, such as any of the agents described in the earlier examples of this specification.
  • the CO 2 is there passed through a column containing solid or l iquid chelating reagent to extract the chelating agent into the supercritical fluid CO 2 stream.
  • the supercritical fizid and chelating agent leave reservoi r 60 through a conduit 62 and are introduced into container 50.
  • the supercritical fizid/chelating agent is intimately mixed with the solid or l iquid waste in container 50 using ei ther a batch or continuous process.
  • simple mixing would occur through stirring or sonif ication.
  • mixing could occur by al lowing CO 2 to flow through a column of solid waste.
  • CO 2 would flow through a column of solid waste material .
  • Continuous mixing with a liquid waste could be achieved with counter current flow.
  • metal chelate and CO 2 is removed through a conduit 64.
  • a depressurizer valve 66 is present in line 64 to reduce the pressure to below seventy-two atmospheres such that the metal chelate precipitates in container 67.
  • the CO 2 gas is then recycled by pump 68 through l ine 70 to gas reservoi r 52.
  • Metal chelates can be removed from the bottom of container 67 through line 72 such that the chelating agent can be regenerated from the metal chelate.
  • metal ions can be stripped from the chelate using a nitric acid solution having a pH less than one.
  • the extraction system should be thermal ly control led, either by known electrical means or immersion in a constant temperature bath. Thermal control allows the carbon dioxide or other supercri tical fucid to be maintained above its supercritical temperature.
  • Trivalent metal ions can be extracted by fucid CO 2 , particularly supercritical CO 2 , containing ⁇ -diketones.
  • Carbon atoms of a ketone are assigned greek letters to designate their position relative to the carbonyl carbon.
  • the first carbon adjacent the carbonyl carbon is designated a, the second such carbon being designated ⁇ , and so on.
  • a ⁇ -diketone has at least two ketone carbonyls wherein one ketone carbonyl is located on a carbon ⁇ to the other ketone functionali ty.
  • the extraction efficiency appears to be enhanced when the ⁇ -diketone is halogenated, particularly when the ⁇ -diketone is fluorinated.
  • a number of f luorinated ⁇ -diketones are commercial ly avai lable from such companies as Aldrich Chemical Company of Mi lwaukee, Wisconsin. These ⁇ -diketones form stable complexes wi th lanthanides and actinides, and hence are useful ligands for SFE of the f-block elements. Extraction and separation of actinides by supercritical fluids are of particular interest because of the potential appl ications for nuclear waste analysis and management.
  • Trialkyl phosphates such as tributyl phosphate, also function wel l as l igands for the extraction of metal and metal loids from liquids and solids. This is particularly true for acidic aqueous systems.
  • Mixed ligands such as ⁇ -diketones and trialkyl phosphates, also have been found to be useful for the supercritical fucid extraction of metals and metal loids, particutarly the actinides, using CO 2 .
  • Using a mixture of ligands comprising ⁇ -diketones and trialkyl phosphates appears to provide a synergistic extraction capability.
  • the fluorinated beta-diketones were purchased from the Aldrich Chemical Company of Milwaukee, WI, and were used without further purification.
  • ⁇ -diketones exist in at least two tautomeric forms, the "keto" tautomer and the
  • enoltautomer Tautomerism is a type of isomerism in which migration of a hydrogen atom results in two or more structures called tautomers. ⁇ -diketones react with metal ions to form chelates either through the enol tautomer or through an enolate anion (a negatively charged "enol” form of the molecule) illustrated by the following equilibria:
  • This example describes the extraction of uranyl and Th(IV) ions from a solid support using only supercritical CO 2 .
  • the solid support used in this example was a cellulose filter paper obtained from Whatman Ltd. (Maidstone, England).
  • the procedure for extracting the metal ions was substantially as described above in example II.
  • Uranyl (UO 2 ) 2+ and Th 4+ solutions were prepared from their nitrate salts, which were obtained from Baker Chemical Co. and from Mallinckrodt, Inc. (St. Louis, MO), respectively. All other chemicals used were analytical-reagent grade.
  • Solid samples were prepared by spiking 10 ⁇ g each of a mixture of (UO 2 ) 2+ and Th 4+ on pre-washed filter papers (Whatman 42, 0.5 cm x 2 cm in size).
  • the filter papers were washed with Ultrex HNO 3 and rinsed with deionized water.
  • the spiked filter papers were allowed to air dry at a room temperature of about 23 °C. All extractions were conducted with the SFE extraction apparatus described above in example I or a commercial extraction vessel that is available from Dionex, of Sunnyvale CA.
  • a glass tube 0.5 cm. i.d. and 3 cm. in length
  • a spiked sample was added to the open end of the glass tube. Water (10 ⁇ l) and about 80 ⁇ mole of a ligand were introduced to the sample in that order. The open end of the tube was then plugged with clean glass wool, and the sample tube was then placed in the extraction vessel and installed in an SFE oven. To extract the metal ions from the solid support, the solid samples were subjected to 10 minutes of static extraction followed by 10 minutes of dynamic flushing at 60 oC and 150 atm. These conditions were found satisfactory for the extraction of uranyl ions from the cellulose based filter paper and from sand by supercritical CO 2 .
  • This example concerns the extraction of uranyl and Th(IV) ions from a solid cellulose support using a ⁇ -diketone.
  • acetylacetone (AA) was used as the ⁇ -diketone, and the extraction procedure used was substantially as described above in example IX.
  • Table VI shows that the extraction of metal and/or metalloid ions from a solid support using a non-fluorinated ⁇ -diketone provides only limited extraction capability. More specifically, AA extracted only about 10 percent of the uranyl(VI) ions from the solid support, and only about 12 percent of the Th(IV) ions from the support.
  • This example describes the extraction of uranyl and Th(IV) ions from a solid cellulose support using FOD (heptafluorobutanoylpivaroylmethane), a fluorinated ⁇ -diketone.
  • FOD heptafluorobutanoylpivaroylmethane
  • the extraction procedure used in this example was substantially as described above in example IX.
  • FOD extracted about 51 percent of the uranyl(VI) ions, and about 80 percent of the
  • Th(IV) ions from the solid support (Table VI).
  • halogenated ⁇ -diketones particularly the fluorinated ⁇ -diketones, provide an enhanced capability for extracting metal ions from a solid support using CO 2 SFE.
  • This example describes the extraction of uranyl and Th(IV) ions from a solid cellulose support using TTA (thenoyltrifluoroacetone).
  • TTA thenoyltrifluoroacetone
  • the extraction procedure used in this example was substantially as described above in example IX.
  • TTA was able to extract about 70 percent of the uranyl(VI) ions, and about 82 percent of the Th(IV) ions.
  • TTA provided the best extraction of metal ions from a solid support using CO 2 SFE.
  • Each solid cellulose sample was 1 cm" in area and contained 10 ⁇ g of U and 10 ⁇ g of Th.
  • This example illustrates how modifying the polarity of the fluid phase significantly increases the extraction efficiencies of metal chelates in CO 2 , particularly supercritical CO 2 .
  • the procedure employed for this example was substantially as described above for examples X- XII, except that a 5% methanol modified CO 2 was used as the extraction fluid. This mixed solvent was prepared before the metal ions were exposed to the solvent.
  • This example describes the extraction of uranyl and Th(IV) ions from aqueous samples.
  • the procedure described in example I was used in this example as well.
  • Water samples were prepared from a 0.1 M LiClO 4 solution containing 2.5 ⁇ g/mL each of (UO 2 ) 2+ and Th 4+ at a pH of 3.5 controlled by an acetate buffer (HAc/LiAc).
  • Mine water samples were collected from an open pit uranium mine near Spokane, Washington.
  • 4 mL of the spiked water sample were placed in the liquid extraction vessel.
  • the pH of the solution was controlled by an acetate buffer.
  • About 50-100 mg of TTA were loaded in the ligand cylinder and placed upstream from the liquid extraction vessel.
  • the samples were extracted dynamically at 60 °C and 150 atm for 20 minutes.
  • the extraction conditions for real mine waters were slightly modified as specified in Table VIII.
  • the sample was removed from the extraction vessel and analyzed by NAA (non-destructive neutron activation analysis, which is a technique known to those skilled in the art).
  • NAA non-destructive neutron activation analysis, which is a technique known to those skilled in the art.
  • a standard solution containing 2.5 ⁇ g/mL each of thorium and uranium was irradiated and counted with the sample under identical conditions. The extraction efficiencies were calculated based on the amounts of thorium and uranium found in the aqueous solution before and after the extraction.
  • the extracted uranyl and Th(IV) complexes in the fluid phase were collected in a glass vial containing 5 mL of chloroform. The solutes trapped in the chloroform solution were determined by back-extraction with 50% HNO3 followed by NAA of the acid solution. The results were also used for recovery calculations.
  • TTA was chosen as the extractant simply because it is a solid which is easier to handle experimentally than the other ⁇ -diketones. This does not mean that the other ligands do not work for the extraction of metal ions from liquid solutions.
  • the extraction was performed dynamically at 150 atm and 60 °C for 20 minutes. In the absence of a ligand, free uranyl and Th(IV) ions cannot be extracted ( (2%) by CO 2 , or even supercritical fluid CO 2 . This is true even with 5% methanol in the fluid phase. However, with TTA present in the CO 2 , the extraction efficiencies for the uranyl and Th(IV) ions are 38% and 70%, respectively (Table VIII).
  • Table VIII also shows the extraction results using tributyl phosphate (TBP).
  • TBP tributyl phosphate
  • TBP alone shows low efficiencies (5-6%) for the extraction of uranyl and Th(IV) ions from the aqueous samples.
  • Table VIII also provides data for extractions using a mixed ligand comprising TBP and TTA. This mixed ligand system is described in more detail below in Section 2, “Synergistic Extraction Using Halogenated ⁇ -Diketones and Trialkyl phosphates. "
  • This example illustrates the benefits obtained in terms of extraction capability when a methanol modifier was used to extract uranyl(VI) and Th(IV) ions from an aqueous solution.
  • TTA was used as the ligand.
  • the procedure used was substantially as described above for example III.
  • Table IX shows that the addition of methanol substantially increases the efficiency of the extraction. More specifically, the addition of the methanol solvent modifier increased the extraction efficiency of uranyl (VI) ion from about 38 % to 85 percent, and from about 70 percent to about 90 percent for Th(IV) ions.
  • the solubility of water in supercritical CO 2 is only on the order of about (0.1 %, there was a concern that the presence of 5 % methanol would increase the solubility of water in the fluid phase.
  • the amount of water transported by the methanol-modified fluid phase is estimated to be small, on the order of about one percent. This estimate was based on the fact that no separate aqueous phase was observed in the collection vial containing chloroform which is known to have a solubility of about 1 % for water at 20 oC.
  • This example describes the extraction of metal ions from a solid sample.
  • Solid samples were prepared by spiking 10 ⁇ g each of a mixture of (UO 2 ) 2+ and Th 4+ on sand. The spiked sand was allowed to air dry at a room temperature of 23 oC.
  • TTA at an initial concentration of about 80 ⁇ moles has been used as the ligand for extracting U(VI) ions and Th(IV) ions from sand samples.
  • TTA extracted about 72 percent of U(VI) ions from sand, and about 74 percent of the Th(IV) ions present in the sand sample, as shown in Table XI.
  • This example illustrates the extraction of metal ions using 80 ⁇ moles of tributyl phosphate.
  • a Whatman filter paper was spiked with 10 ⁇ gs of either U(VI) or Th(IV) ions.
  • the extraction procedure was substantially as described above for examples II and IX.
  • Table X shows the results for extracting uranyl(VI) ions and Th(IV) ions from a cellulose solid matrix using tributyl phosphate (TBP) as the sole extractant in supercritical CO 2 .
  • TBP tributyl phosphate
  • TBP is a neutral ligand
  • anions such as nitrate, acetate, or perchlorate are probably involved in the transport of the uranyl-TBP complex in the fluid phase.
  • these anions are present in the system since the spiked solutions were prepared with uranyl and thorium nitrate in a LiClO 4 solution with pH controlled by an acetate buffer.
  • This example illustrates the extraction of metal ions using a mixed ligand comprising a trialkyl phosphate, such as tributyl phosphate, and a ⁇ -diketone.
  • a mixed ligand comprising a trialkyl phosphate, such as tributyl phosphate, and a ⁇ -diketone.
  • a Whatman filter paper was spiked with 10 ⁇ gs of either U(VI) or Th(IV) ions.
  • 40 ⁇ moles of TBP and 40 ⁇ moles of a fluorinated ⁇ -diketone were added to the sample in this order.
  • the procedure used for this example was substantially as described above for examples IX and XVII.
  • the ⁇ -diketones selected for this example included FOD, TTA, HFA, TAA and AA.
  • Equimolar amounts of the two ligands have been found to provide enhanced extraction capability. For instance, when TTA was used in combination with TBP as the extractant, an equal molar amount, such as about 40 ⁇ mol, of each component was used to perform the extraction. However, this does not mean that only equimolar amounts of the ligand are suitable for forming the mixed ligand systems of the present invention. Currently, it is believed that from about 25 mole percent to about 75 mole percent, preferably about 50 mole percent, of the trialkyl phosphate or trialkylphosphine oxide can be used in combination with the ⁇ -diketone to provide a useful and efficient mixed-ligand system.
  • the extraction efficiencies for Th(IV) by supercritical CO 2 containing TBP and one of the three ⁇ - diketones are also high, in the range of 92-98%. Only TAA shows a lower synergistic effect with TBP for the extraction of uranyl and Th(IV) ions relative to the other fluorinated ⁇ -diketones given in Table X.
  • the extraction efficiencies for the actimdes by neat supercritical CO 2 containing the mixed ligands are comparable to those observed for the methanol-modified CO 2 containing the fluorinated ⁇ -diketones as the extractant.
  • the synergistic approach has the advantage of avoiding the use of an organic solvent, such as methanol, in the SFE process.
  • This example concerns the extraction of Uranyl and Th(IV) ions from sand using the synergistic extraction procedure discussed above in example XVIII.
  • the procedure used for this extraction was substantially as described above in examples IX and XVI.
  • Table XI below illustrates the results of such extractions with neat supercritical CO 2 containing TTA, TBP, and mixed TTA + TBP at 60 °C and 150 atm.
  • Positive synergistic extractions of uranyl and Th(IV) ions also were found in this system for the mixed ligands.
  • the extraction efficiency for uranyl ions with TTA+TBP is 94% compared with 72% for TTA and 15% for TBP, individually.
  • a similar synergistic effect is also observed for the extraction of Th(IV) from sand.
  • Uranyl ions also have been extracted from natural aqueous samples using the mixed ligand approach.
  • the aqueous samples were mine waters collected from the Northwest region.
  • the uranium concentrations in two mine waters tested were 9.6 ⁇ g/mL and 18 ⁇ g/mL.
  • the mine waters were extracted with a 1: 1 molar mixture of TTA+TBP in neat CO 2 at 60 °C and 150 atm for a static time of 10 minutes followed, by 20 minutes of dynamic extraction. Under these conditions, the percent extraction of uranium from these samples were 81 ⁇ 4% and 78 ⁇ 5 %, respectively, for triplicate runs (Table XII).
  • the contaminated mine waters also were added to a top-soil sample collected from northern Idaho.
  • the contaminated soil samples were dried at room temperature prior to conducting the SFE experiments.
  • the results of the extraction of uranium from the contaminated soil samples with a 1: 1 mixture of TTA+TBP or HFA + TBP in supercritical CO 2 at 60 °C and 150 atm also are given in Table XII.
  • the percent extraction of uranium with HFA+TBP for both soil samples A and B is about 90%, whereas TTA+TBP shows lower percent extractions (77-82%) of uranium under the same conditions.
  • uranyl and Th(IV) ions can be efficiently extracted using supercritical CO 2 containing a halogenated ⁇ -diketone, preferably a fluorinated ⁇ -diketone.
  • a binary mixture consisting of tri-n-octylphosphine oxide (TOPO) and a fluorinated ⁇ -diketone is slightly more effective than a binary mixture of TBP and a fluorinated ⁇ -diketone for the extraction of uranyl and Th(IV) ions from the mine waters and contaminated soil samples as shown in Table XII.
  • TOPO is given below, wherein R 6 - R 8 are n-octyl groups, although it will be understood by those skilled in the art that R 6 - R 8 also may be selected from the group consisting of lower alkyl groups.
  • Uranium and thorium are usually extracted from these solids using strong acids for dissolution followed by various separation techniques.
  • fluorinated acids may be used in supercritical CO 2 .
  • the matrix interferences may be minimized using selective chelating agents.
  • the novel SFE technique which uses fluorinated ⁇ -diketones as extractants, and the synergistic effects obtained with trialkyl phosphates, offers numerous applications for the separation of metal and metalloid ions from solid and liquid materials.
  • This example describes the extraction of lanthanides [such as La(III), Eu(III) and Lu(III)] from a solid matrix using supercritical carbon dioxide and a binary mixture of TBP and a fluorinated ⁇ -diketone.
  • the fluorinated ⁇ -diketones were obtained from Aldrich Chemical Company.
  • Solutions of La 3+ , Eu 3+ and Lu 3+ were prepared from the nitrate salts, which were obtained from Aldrich.
  • Solid samples were prepared by spiking 10 ⁇ g each of a mixture of the ions on prewashed filter paper or sand. The spiked samples were allowed to air dry at room temperature. The weight of the dry sand samples was about 300 mg. All the experiments were conducted using the apparatus of FIG. 1 and as described in example 1.
  • Table XIII shows the results of extracting La 3+ , Eu 3+ and Lu 3+ from sand using neat supercritical carbon dioxide containing TTA, TBP and mixed TTA/TBP at 60 °C and 150 atm. Synergistic extraction of the lanthanides is again observed in this system when TTA is mixed with TBP. The extraction efficiencies of the La 3+ , Eu 3+ and Lu 3+ in sand are 91 %,
  • the percent extraction represents the amount of a lanthanide removed from the solid matrix.
  • the percent recovery represents the amount of the lanthanide trapped in the chloroform solution.
  • Each sand sample (300 mg by weight) contains 10 ⁇ g each of Lu , Eu , and Lu 3+ . 10 min static extraction followed by 20 min of dynamic extraction.
  • This example describes the extraction of lanthanides [such as La(III), Eu(III) and Lu(III)] from an aqueous matrix using supercritical carbon dioxide and a binary mixture of TBP and a fluorinated ⁇ -diketone.
  • the fluorinated ⁇ -diketones were obtained from Aldrich Chemical Company.
  • Solutions of La 3 + , Eu 3 + and Lu 3 + were prepared from the nitrate salts, which were obtained from Aldrich.
  • 4 ml of the spiked water sample was placed in a liquid extraction vessel. The pH of the solutions was controlled by an acetate buffer.
  • the water sample typically contained about 2.5 ⁇ g/ml each of La 3+ , Eu 3 + and Lu 3 + .
  • a ligand such as TTA
  • Each water sample (4 mL) contains 2.5 ⁇ g/mL of La 3 + , Eu 3 + , and Lu 3+ each at pH 4.0 controlled by an acetate buffer.
  • One specific embodiment of the present invention is the removal of radioactive ions from solid and liquid materials.
  • the described SFE process can be used to extract actinides in acid solutions such as those produced by the PUREX process (Plutonium Uranium Recovery by Extraction).
  • PUREX process nuclear fuel material is first dissolved in hot nitric acid followed by extraction of the dissolved uranian and plutonium with an organic solvent containing 20-30% of TBP in kerosene or in n-dodecane.
  • supercritical fluid extraction of metals and metalloids in acid solutions using carbon dioxide also has proven useful.
  • This example concerns the extraction of U(VI), Th(IV) and Nd(III) from 6 molar nitric acid (HNO 3 ).
  • the procedure used for the extraction was substantially as described above in example XIV.
  • the ligands used for this example included TBP and TTA, as well as TOPO and TTA.
  • the ligand 5ml TBP
  • the ligand was placed in a stainless steel vessel with supercritical carbon dioxide bubbled from the bottom of the vessel.
  • the fluid phase is saturated with TBP.
  • supercritical carbon dioxide was first saturated with TBP using the method described above.
  • the fluid phase then passed through a second ligand cell containing 100 mg of TTA.
  • example XXII shows that lanthanides and actinides can be extracted from acidic solutions, such as 6 M HNO 3 , using TBP in supercritical carbon dioxide.
  • a binary mixture of TBP and a fluorinated ⁇ -diketone, or TOPO and a fluorinated ⁇ -diketone, in supercritical carbon dioxide can enhance the extraction efficiencies of the lanthanides and the actinides from acidic solutions.
  • carbon dioxide can be used, either in a supercritical state or as a subcritical liquid under pressure, to replace the use of organic solvents, such as kerosene, for the extraction of lanthanide and actinides from acidic solutions.
  • the triple point of carbon dioxide is 5.1 atm and -56.3 oC.
  • liquid carbon dioxide becomes a liquid above 5.1 atm.
  • liquid carbon dioxide has a density comparable or slightly greater than supercritical carbon dioxide, thus the solvation power of liquid carbon dioxide is comparable to that of supercritical carbon dioxide.
  • liquid carbon dioxide should also be able to dissolve the metal complexes described above.
  • liquid carbon dioxide does not have the "gas-like" properties of the supercritical carbon dioxide. This means liquid carbon dioxide has large a viscosity, small diffusivity.and consequently poor penetration power compared with the supercritical carbon dioxide.
  • liquid carbon dioxide should also be able to extract lanthanides and actinides from acid solutions with TBP or a mixture of TBP and a fluorinated ⁇ -diketone as the extractant, but with lower efficiencies.
  • the extraction efficiency of liquid carbon dioxide is expected to depend on the applied pressure. It is also expected that the extraction efficiency of liquid carbon dioxide can be improved with mechanical stirring and agitation.

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  • Organic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Geology (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Water Supply & Treatment (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Health & Medical Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Extraction Or Liquid Replacement (AREA)

Abstract

Procédé d'extraction de métaux et de métalloïdes d'un matériau solide ou liquide consistant à le soumettre à un solvant fluide supercritique contenant un chélateur qui forme dans ledit fluide des chélats solubles permettant l'extraction desdits matériaux. On préconise du CO2 supercritique comme solvant et comme chélateur de la β-dicétone fluorée, ou mieux, du CO2 supercritique comme solvant, et de la β-dicétone fluorée associée à du trialkylphosphate, ou de la β-dicétone fluorée associée à de l'oxyde de trialkylphosphine. Bien que le trialkylphosphate soit à même d'extraire les lanthanides et actinides des solutions acides, une solution binaire de β-dicétone fluorée associée à du trialkylphosphate, ou à de l'oxyde de trialkylphosphine permet d'accroître les rendements d'extraction. Ce procédé constitue un moyen d'extraction de déchets contaminants des rejets industriels peu agressif pour l'environnement puisqu'il n'utilise ni acides, ni solvants préjudiciables sur le plan biologique, et son utilité principale réside dans l'extraction des lanthanides et actinides des solutions acides. Les chélates ainsi que le fluide supercritique peuvent être régénérés et les produits contaminants récupérés, ce qui rend le procédé efficace et économique.
PCT/US1994/006450 1994-06-02 1994-06-09 Extraction de metaux et metalloides de fluides WO1995033541A1 (fr)

Priority Applications (7)

Application Number Priority Date Filing Date Title
EP94921262A EP0762918B1 (fr) 1994-06-02 1994-06-09 Extraction de metaux et metalloides de fluides
PCT/US1994/006450 WO1995033541A1 (fr) 1994-06-09 1994-06-09 Extraction de metaux et metalloides de fluides
CA002191227A CA2191227C (fr) 1994-06-02 1994-06-09 Extraction de metaux et metalloides de fluides
DE69431260T DE69431260D1 (de) 1994-06-02 1994-06-09 Fluid-extraktion von metallen und/oder metalloiden
JP50079896A JP2002508697A (ja) 1994-06-02 1994-06-09 金属及び／又は半金属の流体抽出
AU72052/94A AU7205294A (en) 1994-06-09 1994-06-09 Fluid extraction of metals and/or metalloids
KR1019960706769A KR970703183A (ko) 1994-06-02 1994-06-09 금속 및/또는 메탈로이드의 유체 추출 방법(fluid extraction of metals and/or metalloids)

Applications Claiming Priority (1)

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PCT/US1994/006450 WO1995033541A1 (fr) 1994-06-09 1994-06-09 Extraction de metaux et metalloides de fluides

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US5606724A (en) * 1995-11-03 1997-02-25 Idaho Research Foundation, Inc. Extracting metals directly from metal oxides
WO1998004753A1 (fr) * 1996-07-26 1998-02-05 Idaho Research Foundation, Inc. Extraction de metaux ou de metalloides par des fluides
WO1998004754A1 (fr) * 1996-07-26 1998-02-05 Idaho Research Foundation, Inc. Procede et appareil pour l'extraction inversee de chelates
WO1999009223A1 (fr) * 1997-08-20 1999-02-25 Idaho Research Foundation, Inc. Procede permettant de dissocier des metaux ou des composes metalliques
US6187911B1 (en) 1998-05-08 2001-02-13 Idaho Research Foundation, Inc. Method for separating metal chelates from other materials based on solubilities in supercritical fluids
US7128840B2 (en) 2002-03-26 2006-10-31 Idaho Research Foundation, Inc. Ultrasound enhanced process for extracting metal species in supercritical fluids
WO2007096891A1 (fr) * 2006-02-27 2007-08-30 Zvi Ludmer Séparation simultanée de métaux lourds et de matières organiques présents dans le sol, dans de la boue ou dans des sédiments
RU2606973C2 (ru) * 2014-11-17 2017-01-10 Национальный Научный Центр "Харьковский Физико-Технический Институт" (Ннц Хфти) Способ сверхкритической флюидной экстракции комплексов урана
CN108409075A (zh) * 2018-03-23 2018-08-17 李凡 一种油基钻井废弃物临界流体萃取分离处理系统和方法
CN109772871A (zh) * 2019-01-29 2019-05-21 天津大学 一种利用亚临界低温萃取技术修复草甘膦污染农田土壤的方法
US10533239B2 (en) 2016-11-01 2020-01-14 Battelle Energy Alliance, Llc Methods of recovering rare earth elements from a material
RU2770418C1 (ru) * 2021-10-14 2022-04-18 Российская Федерация, от имени которой выступает Государственный корпорация по атомной энергии "Росатом" Способ удаления хлоридов щелочных металлов, хлоридов урана и плутония с поверхности твердых тел
WO2022167903A1 (fr) * 2021-02-04 2022-08-11 Marco Nahmias Nanni Procédé d'extraction de produits chimiques résiduels à partir d'une matrice polymère

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Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5606724A (en) * 1995-11-03 1997-02-25 Idaho Research Foundation, Inc. Extracting metals directly from metal oxides
WO1997016575A1 (fr) * 1995-11-03 1997-05-09 Idaho Research Foundation, Inc. Extraction de metaux directement des oxydes metalliques qui les contiennent
WO1998004753A1 (fr) * 1996-07-26 1998-02-05 Idaho Research Foundation, Inc. Extraction de metaux ou de metalloides par des fluides
WO1998004754A1 (fr) * 1996-07-26 1998-02-05 Idaho Research Foundation, Inc. Procede et appareil pour l'extraction inversee de chelates
US5840193A (en) * 1996-07-26 1998-11-24 Idaho Research Foundation Fluid extraction using carbon dioxide and organophosphorus chelating agents
WO1999009223A1 (fr) * 1997-08-20 1999-02-25 Idaho Research Foundation, Inc. Procede permettant de dissocier des metaux ou des composes metalliques
US6132491A (en) * 1997-08-20 2000-10-17 Idaho Research Foundation, Inc. Method and apparatus for dissociating metals from metal compounds extracted into supercritical fluids
US6187911B1 (en) 1998-05-08 2001-02-13 Idaho Research Foundation, Inc. Method for separating metal chelates from other materials based on solubilities in supercritical fluids
US7128840B2 (en) 2002-03-26 2006-10-31 Idaho Research Foundation, Inc. Ultrasound enhanced process for extracting metal species in supercritical fluids
WO2007096891A1 (fr) * 2006-02-27 2007-08-30 Zvi Ludmer Séparation simultanée de métaux lourds et de matières organiques présents dans le sol, dans de la boue ou dans des sédiments
RU2606973C2 (ru) * 2014-11-17 2017-01-10 Национальный Научный Центр "Харьковский Физико-Технический Институт" (Ннц Хфти) Способ сверхкритической флюидной экстракции комплексов урана
US10533239B2 (en) 2016-11-01 2020-01-14 Battelle Energy Alliance, Llc Methods of recovering rare earth elements from a material
CN108409075A (zh) * 2018-03-23 2018-08-17 李凡 一种油基钻井废弃物临界流体萃取分离处理系统和方法
CN109772871A (zh) * 2019-01-29 2019-05-21 天津大学 一种利用亚临界低温萃取技术修复草甘膦污染农田土壤的方法
WO2022167903A1 (fr) * 2021-02-04 2022-08-11 Marco Nahmias Nanni Procédé d'extraction de produits chimiques résiduels à partir d'une matrice polymère
RU2770418C1 (ru) * 2021-10-14 2022-04-18 Российская Федерация, от имени которой выступает Государственный корпорация по атомной энергии "Росатом" Способ удаления хлоридов щелочных металлов, хлоридов урана и плутония с поверхности твердых тел

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