The present invention relates to the removal and recovery of penicillin and organic acids from feed solutions, such as process streams and waste waters, using supported liquid membrane technology.
Liquid membranes combine extraction and stripping into one step, rather than the two separate steps required in conventional processes such as solvent extractions. 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 and 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 and 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 solutionsxe2x80x94the 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, and sometimes a modifier. The diluent is generally an inert organic solvent.
The use of SLMs to remove penicillin and organic acids from aqueous feed solutions has attracted considerable attention in the scientific and industrial community. The extraction of penicillin G from aqueous feed solutions has been investigated (C. J. Lee, H. J. Yeh, W. Y. Yang, and C. R. Kan, xe2x80x9cPreparation of penicillin G from Phenylacetic Acid in a Supported Liquid Membrane Systemxe2x80x9d, Biotechnol. Bioeng., 43, 309-313 (1994); R. S. Juang and Y. S. Lin, xe2x80x9cInvestigation on Interfacial Reaction Kinetics of Penicillin G and Amberlite LA-2 from Membrane Flux Measurementsxe2x80x9d, J. Membrane Sci., 141, 19-30 (1998)).
The extraction of organic acids, including phenylalanine, acrylic acid, lactic acid, proprionic acid, citric acid, and acetic acid, from aqueous solutions with SLMs has been studied (L. K. Ju and A. Verma, xe2x80x9cCharacteristics of Lactic Acid Transport in Supported Liquid Membranesxe2x80x9d, Sep. Sci. Technol., 29, 2299-2315 (1994); J. T. Rockman, E. Kehat, and R. Lavie, xe2x80x9cMathematical Model for Thermally Enhanced Facilitated Transportxe2x80x9d, Ind. Eng. Chem. Res., 34, 2455-2463 (1995); F. Ozadali, B. A. Glatz, and C. E. Glatz, xe2x80x9cFed-batch Fermentation with and without On-line Extraction for Propionic and Acetic Acid Production by Propionibacterium Acidipropionicixe2x80x9d, Applied Microb. Biotechnol., 44 710-716 (1996); R. S. Juang and L. J. Chen, xe2x80x9cAnalysis of the Transport Rates of Citric Acid through a Supported Liquid Membrane Containing Tri-n-octylaminexe2x80x9d, Ind. Eng. Chem. Res., 35, 1673-1679 (1996); R. S. Juang, S. H. Lee, and R. C. Shiau, xe2x80x9cMass-transfer Modeling of Permeation of Lactic Acid across Amine-mediated Supported Liquid Membranesxe2x80x9d, J. Membrane Sci., 137, 231-239 (1997); R. S. Juang, S. H. Lee, and R. H. Huang, xe2x80x9cModeling of Amine-facilitated Liquid Membrane Transport of Binary Organic Acids, Sep. Sci. Technol., 33, 2379-2395 (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, xe2x80x9cStability of Supported Liquid Membranes: State of the Artxe2x80x9d, Sep. Sci. Technol., 31, 2733 (1996); T. M. Dreher and G. W Stevens, xe2x80x9cInstability Mechanisms of Supported Liquid Membranesxe2x80x9d, Sep. Sci. Technol., 3, 835-853 (1998); J. F. Dozol, J. Casas, and A. Sastre, xe2x80x9cStability of Flat Sheet Supported Liquid Membranes in the Transport of Radionuclides from Reprocessing Concentrate Solutionsxe2x80x9d, 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 and Hall, New York, 1992). In this configuration with two sets of microporous hollow-fiber membranes, one 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 can 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 and 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 phase and then stripped into the aqueous droplets in the emulsion. The target species can then be recovered from the internal aqueous phase by breaking the emulsion, typically via electrostatic coalescence, followed by electroplating or precipitation.
The use of ELMs to remove penicillin and organic acids from aqueous feed solutions has long been pursued in the scientific and industrial community. The use of ELMs for the extraction of Penicillin G from aqueous feed solutions has been described (T. Scheper, Z. Likidis, K. Makryaleas, Ch. Nowattny, and K. Schugerl, xe2x80x9cThree Different Examples of Enzymatic Bioconversion in Liquid Membrane Reactorsxe2x80x9d, Enzyme Microb. Technol., 2, 625-631 (1987); K. H. Lee, S. C. Lee, and W. K. Lee, xe2x80x9cPenicillin G Extraction from Model Media Using an Emulsion Liquid Membrane: A Theoretical Model of Product Decompositionxe2x80x9d, J. Chem. Technol. Biotechnol., 59, 365-370 (1994); K. H. Lee, S. C. Lee, and W. K. Lee, xe2x80x9cPenicillin G Extraction from Model Media Using an Emulsion Liquid Membrane: Determination of Optimum Extraction Conditions, J. Chem. Technol. Biotechnol., 59, 371-376 (1994); Y. S. Mok, S. C. Lee, and W. K. Lee, xe2x80x9cSynergistic Effect of Surfactant on Transport Rate of Organic Acid in Liquid Emulsion Membranesxe2x80x9d, Sep. Sci. Technol., 30, 399-417 (1995); S. C. Lee, K. H. Lee, G. H. Hyun, and W. K. Lee, xe2x80x9cContinuous Extraction of Penicillin G by an Emulsion Liquid Membrane in a Countercurrent Extraction Columnxe2x80x9d, J. Membrane Sci., 124, 43-51 (1997); S. C. Lee, J. H. Chang, B. S. Ahn, and W. K. Lee, xe2x80x9cMathematical Modeling of Penicillin G Extraction in an Emulsion Liquid Membrane System Containing only a Surfactant in the Membrane Phasexe2x80x9d, J. Membrane Sci., 149, 39-49 (1998); S. C. Lee, xe2x80x9cEffect of Volume Ratio of Internal Aqueous Phase to Organic Membrane Phase (W/O Ratio) of Water-in-Oil Emulsion on Penicillin G Extraction by Emulsion Liquid Membranexe2x80x9d, J. Membrane Sci., 163, 193-201 (1999)).
The extraction of organic acids, including phenylalanine, acrylic acid, lactic acid, proprionic acid, citric acid, and acetic acid, from aqueous solutions with ELMs has been investigated (M. P. Thien and T. A. Hatton, xe2x80x9cLiquid Emulsion Membranes and Their Applications in Biochemical Processingxe2x80x9d, Sep. Sci. Technol., 23, 819-853 (1988); D. J. O""Brien and G. E. Senske, xe2x80x9cSeparation and Recovery of Low Molecular Weight Organic Acids by Emulsion Liquid Membranesxe2x80x9d, Sep. Sci. Technol., 24, 617-628 (1989); H. Itoh, M. P. Thien, T. A. Hatton, and D. I. C. Wang, xe2x80x9cWater Transport Mechanism in Liquid Emulsion Membrane Process for the Separation of Amino Acidsxe2x80x9d, J. Membrane Sci., 51, 309-322 (1990); T. Hano, M. Matsumoto, T. Kawazu, and T. Ohtake, xe2x80x9cSeparation of Di- and Tripeptides with Solvent Extraction and an Emulsion Liquid Membranexe2x80x9d, J. Chem. Technol. Biotechnol., 62, 60-63 (1995); P. J. Pickering and J. B. Chaudhuri, xe2x80x9cEnantioselective Extraction of D-Phenylalanine from Racemic D- and L-Phenylalanine Using Chiral Emulsion Liquid Membranesxe2x80x9d, J. Membrane Sci., 127, 115-130 (1997); M. Matsumoto, T. Ohtake, M. Hirata, and T. Hano, xe2x80x9cExtraction Rates of Amino Acids by an Emulsion Liquid Membrane with Tri-n-octylmethylammonium Chloridexe2x80x9d, J. Chem. Technol. Biotechnol., 73, 237-242 (1998); X. R. Liu and D. S. Liu, xe2x80x9cModeling of Facilitated Transport of Phenylalanine by Emulsion Liquid Membranes with Di(2-ethylhexyl) Phosphoric Acid as a Carrierxe2x80x9d, Sep. Sci. Technol., 33, 2597-2608 (1998)).
One disadvantage of ELMs is that the emulsion swells upon prolonged contact with the feed stream. This swelling causes a reduction in the stripping reagent concentration in the aqueous droplets which reduces stripping efficiency. It also results in dilution of the target species that has been concentrated in the aqueous droplets, resulting in lower separation efficiency of the membrane. The swelling further results in a reduction in membrane stability by making the membrane thinner. Finally, swelling of the emulsion increases the viscosity of the spent emulsion, making it more difficult to demulsify. A second disadvantage of ELMs is membrane rupture, resulting in leakage of the contents of the aqueous droplets into the feed stream and a concomitant reduction of separation efficiency. Raghuraman and Wiencek (B. Raghuraman and J. Wiencek, xe2x80x9cExtraction with Emulsion Liquid Membranes in a Hollow-Fiber Contactorxe2x80x9d, AIChE J., 39, 1885-1889 (1993)) have described the use of microporous hollow-fiber contactors as an alternative contacting method to direct dispersion of ELMs to minimize the membrane swelling and leakage. This is due to the fact that the hollow-fiber contactors do not have the high shear rates typically encountered with the agitators used in the direct dispersion. Additional disadvantages include the necessary process steps for making and breaking the emulsion.
Thus, there is a need in the art for an extraction process which maximizes the stability of the SLM membrane, resulting in efficient removal and recovery of penicillin or organic acids from the aqueous feed solutions.
The present invention relates generally to a process for the removal and recovery of target species from a feed solution using combined SLM/strip dispersion. The invention also relates to a process resulting in efficient removal and recovery of penicillin and organic acids from process streams and waste water.
It must be noted that, as used in this specification and the appended claims, the term penicillin shall be inclusive of all members of the group of antibiotics biosynthesized by several species of molds and any synthetic derivatives.
In one embodiment, the present invention relates to a process for the removal and recovery of penicillin and organic acids from a feed solution which comprises the following steps. First, a feed solution containing penicillin or organic acids is passed on one side of the SLM embedded in a microporous support material to remove the penicillin or organic acids by the use of a strip dispersion on the other side of the SLM. As described above, the strip dispersion can be formed by dispersing an aqueous strip solution in an organic liquid, for example, using a mixer. The strip dispersion, or a part of the strip dispersion, is then allowed to stand, resulting in separation into two phases: the organic liquid phase and the aqueous strip solution phase containing a concentrated solution of the target species.
The continuous organic phase of the strip dispersion readily wets the pores of a microporous support to form a stable SLM. The process of the present invention provides a number of operational and economic advantages over the use of conventional SLMs.
Thus, it is an object of the present invention to provide an SLM process for the removal and recovery of target species which provides increased membrane stability.
It is another object of the invention to provide an SLM process having improved flux.
It is yet another object of the present invention to provide an SLM process having improved recovery of the target species to provide a concentrated strip solution.
It is a further object of the invention to provide an SLM process for the removal and recovery of a target species from a feed solution which exhibits decreased operation costs and a decreased capital investment over conventional SLM processes.