Organic compounds -- part of the class 532-570 series – Organic compounds – Phosphorus acids or salts thereof
Reexamination Certificate
2000-03-24
2001-09-18
Vollano, Jean F. (Department: 1600)
Organic compounds -- part of the class 532-570 series
Organic compounds
Phosphorus acids or salts thereof
Reexamination Certificate
active
06291705
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the removal and recovery of target species, such as metals, from feed solutions, such as waste waters and process streams, using supported liquid membrane technology.
BACKGROUND OF THE INVENTION
Liquid membranes combine extraction and stripping, which are normally carried out in two separate steps in conventional processes such as solvent extractions, into one step. A one-step liquid membrane process provides the maximum driving force for the separation of a targeted species, leading to the best clean-up and recovery of the species (W. S. Winston Ho and Kamalesh K. Sirkar, eds.,
Membrane Handbook
, Chapman & Hall, New York, 1992).
There are two types of liquid membranes: (1) supported liquid membranes (SLMs) and (2) emulsion liquid membranes (ELMs). In SLMs, the liquid membrane phase is the organic liquid imbedded in pores of a microporous support, e.g., microporous polypropylene hollow fibers (W. S. Winston Ho and Kamalesh K. Sirkar, eds.,
Membrane Handbook
, Chapman & Hall, New York, 1992). When the organic liquid contacts the microporous support, it readily wets the pores of the support, and the SLM is formed.
For the extraction of a target species from a feed solution, the organic-based SLM is placed between two aqueous solutions—the feed solution and the strip solution—where the SLM acts as a semi-permeable membrane for the transport of the target species from the feed solution to the strip solution. The organic liquid in the SLM is immiscible in the aqueous feed and strip streams and contains an extractant, a diluent which is generally an inert organic solvent, and sometimes a modifier.
The use of SLMs to remove metals from aqueous feed solutions has been long pursued in the scientific and industrial community. The removal of metals, including cobalt, copper, nickel, zinc, cadmium, and gallium, from aqueous solutions has been studied (R. S. Juang and J. D. Jiang, “Rate-controlling Mechanism of Cobalt Transport through Supported Liquid Membranes Containing Di(2-ethylhexyl) Phosphoric Acid,”
Sep. Sci. Technol
., 29, 223-237 (1994); T. Saito, “Selective Transport of Copper(I, II), Cadmium(II), and Zinc(II) Ions through a Supported Liquid Membrane Containing Bathocuproine, Neocuproine, or Bathophenanthroline,”
Sep. Sci. Technol
., 29, 1335-1346 (1994); M. Teramoto, N. Ohnishi, and H. Matsuyama, “Effect of Recycling of Feed Solution on the Efficiency of Supported Liquid Membrane Module,”
Sep. Sci. Technol
., 29, 1749-1755 (1994); F. F. Zha, A. G. Fane, and C. J. D. Fell, “Liquid Membrane Processes for Gallium Recovery from Alkaline Solutions,”
Ind. Eng. Chem. Res
., 34, 1799-1809 (1995); S. B. Kunungo and R. Mohapatra, “Coupled Transport of Zn(II) through a Supported Liquid Membrane Containing bis(2,4,4-Trimethylpentyl) Phosphinic Acid in Kerosene. II Experimental Evaluation of Model Equations for Rate Process under Different Limiting Conditions,”
J. Membrane Sci
., 105, 227-235 (1995)).
The extraction of rare earth metals, including europium, lanthanum, and neodymium, with SLMs has been investigated (C. Nakayama, S. Uemiya, and T. Kojima, “Separation of Rare Earth Metals Using a Supported Liquid Membrane with DTPA,”
J. Alloys Compounds
, 225, 288-290 (1995); R. S. Juang and S. H. Lee, “Analysis of the Transport Rates of Europium(III) across an Organophosphinic Acid Supported Liquid Membrane,”
J. Membrane Sci
., 110, 13-23 (1996)).
Recently, the removal of metals, including copper, zinc, cadmium, and palladium, with SLMs has been described (N. Aouad, G. Miquel-Mercier, E. Bienvenüe, E. Tronel-Peyroz, G. Jerninet, J. Juillard, and P. Seta, “Lasalocid (X537A) as a Selective Carrier for Cd(II) in Supported Liquid Membranes,”
J. Membrane Sci
., 139, 167-174 (1998); J. A. Daoud, S. A. El-Reefy, and H. F. Aly, “Permeation of Cd(II) Ions through a Supported Liquid Membrane Containing Cyanex-302 in Kerosene,”
Sep. Sci. Technol
., 33, 537-549 (1998); J. Vander Linden and R. F. De Ketelaere, “Selective Recuperation of Copper by Supported Liquid Membrane (SLM) Extraction,”
J. Membrane Sci
., 139, 125-135 (1998); M. E. Campderrós, A. Acosta, and J. Marchese, “Selective Separation of Copper with LIX 864 in a Hollow Fiber Module,”
Talanta
, 47, 19-24 (1998); M. Rovira and A. M. Sastre, “Modelling of Mass Transfer in Facilitated Supported Liquid-Membrane Transport of Palladium(II) Using Di-(2-ethylhexyl) Thiophosphoric Acid,”
J. Membrane Sci
., 149, 241-250 (1998); J. C. Lee, J. Jeong, J. T. Park, I. J. Youn, and H. S. Chung, “Selective and Simultaneous Extractions of Zn and Cu Ions by Hollow Fiber SLM Modules Containing HEH(EHP) and LIX84
,” Sep. Sci. Technol
., 34, 1689-1701 (1999); F. Valenzuela, C. Basualto, C. Tapia, and J. Sapag, “Application of Hollow-Fiber Supported Liquid Membranes Technique to the Selective Recovery of a Low Content of Copper from a Chilean Mine Water,”
J. Membrane Sci
., 155, 163-168 (1999); M. Oleinikova, C. González, M. Valiente, and M. Muñoz, “Selective Transport of Zinc through Activated Composite Membranes Containing Di(2-ethylhexyl) Dithiophosphoric Acid as a Carrier,”
Polyhedron
, 18, 3353-3359 (1999)).
The extraction of rare earth metals, including europium, lanthanum, neodymium, praseodymium, and gadolinium, with SLMs has been reported recently (M. R. Yaftian, M. Burgard, C. B. Dieleman and D. Matt, “Rare-earth Metal-ion Separation Using a Supported Liquid Membrane Mediated by a Narrow Rim Phosphorylated Calix[4]arene,”
J. Membrane Sci
., 144, 57-64 (1998)).
One disadvantage of SLMs is their instability due mainly to loss of the membrane liquid (organic solvent, extractant, and/or modifier) into the aqueous phases on each side of the membrane (A. J. B. Kemperman, D. Bargeman, Th. Van Den Boomgaard, H. Strathmann, “Stability of Supported Liquid Membranes: State of the Art,”
Sep. Sci. Technol
., 31, 2733 (1996); T. M. Dreher and G. W Stevens, “Instability Mechanisms of Supported Liquid Membranes,”
Sep. Sci. Technol
., 33, 835-853 (1998); J. F. Dozol, J. Casas, and A. Sastre, “Stability of Flat Sheet Supported Liquid Membranes in the Transport of Radionuclides from Reprocessing Concentrate Solutions,”
J. Membrane Sci
., 82, 237-246 (1993)). The prior art has attempted to solve this problem through the combined use of SLM with a module containing two sets of hollow fibers, i.e., the hollow-fiber contained liquid membrane (W. S. Winston Ho and Kamalesh K. Sirkar, eds.,
Membrane Handbook
, Chapman & Hall, New York, 1992). In this configuration, with two sets of microporous hollow-fiber membranes, one set of membranes carries the aqueous feed solution, and the other carries the aqueous strip solution. The organic phase is contained between the two sets of hollow fibers by maintaining the aqueous phases at a higher pressure than the organic phase. The use of the hollow-fiber contained liquid membrane increases membrane stability because the liquid membrane may be continuously replenished. However, this configuration is not advantageous because it requires mixing two sets of fibers to achieve a low contained liquid membrane thickness.
In ELMs, an emulsion acts as a liquid membrane for the separation of the target species from a feed solution. An ELM is created by forming a stable emulsion, such as a water-in-oil emulsion, between two immiscible phases, followed by dispersion of the emulsion into a third, continuous phase by agitation for extraction. The membrane phase is the oil phase that separates the encapsulated, internal aqueous droplets in the emulsion from the external, continuous phase (W. S. Winston Ho and Kamalesh K. Sirkar, eds.,
Membrane Handbook
, Chapman & Hall, New York, 1992). The species-extracting agent is contained in the membrane phase, and the stripping agent is contained in the internal aqueous droplets. Emulsions formed from these two phases are generally stabilized by use of a surfactant. The external, continuous phase is the feed solution containing the target species. The target species is extracted from the aqueous feed solution into the membrane ph
Ho W. S. Winston
Wang Bing
Commodore Separation Technologies Inc.
Kilpatrick & Stockton LLP
Vollano Jean F.
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