Chemistry of inorganic compounds – Treating mixture to obtain metal containing compound – Group vib metal
Reexamination Certificate
1999-01-21
2001-01-09
Bos, Steven (Department: 1754)
Chemistry of inorganic compounds
Treating mixture to obtain metal containing compound
Group vib metal
C210S638000, C210S643000
Reexamination Certificate
active
06171563
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a supported liquid membrane process that is useful for removal and recovery of chromium from waste waters and process streams.
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. ELMs are usually prepared by first forming an emulsion between two immiscible phases, and then dispersing the emulsion in a third (continuous) phase by agitation for extraction. The membrane phase is the liquid phase that separates the encapsulated, internal 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 use of liquid membranes to remove chromium from wastewaters has long been pursued by the scientific and industrial community (W. S. Winston Ho and Kamalesh K. Sirkar, eds.,
Membrane Handbook
, Chapman & Hall, New York, 1992; J. W. Frankenfeld and N. N. Li in N. N. Li, ed.,
Recent Developments in Separation Science
, pp. 285-292, CRC Press, Boca Raton, Fla., 1977; E. J. Fuller and N. N. Li,
J. Membrane Sci.,
18, 251 (1984); A. I. Alonso and C. C. Pantelides,
J. Membrane Sci.,
110, 151 (1996)). Nonetheless, there remains a need for a process that not only can remove chromium but also can recover it.
The chromium recovered in high concentration is desirable for reuse or resale. For example, a highly concentrated chromium solution containing at least 15 wt. % hexavalent chromium (Cr(VI)), e.g., 46.7 wt. % Na
2
CrO
4
, and less than 10 wt. % Na
2
SO
4
is a useful form of a product for reuse or resale.
It is an object of the present invention to provide a novel supported liquid membrane process that not only removes chromium to an acceptable level in the treated water suitable for discharge or recycle but also recovers the chromium in a usable form for reuse or resale. This process not only solves the environmental problem but also recovers the chromium.
SUMMARY OF THE INVENTION
The present invention is directed toward a process using a supported liquid membrane comprising two steps: (1) a feed solution containing hexavalent chromium (Cr(VI)) is treated to decrease the chromium to an acceptable level for discharge or recycle with a strip solution which results in a moderately concentrated Cr(VI) and (2) the resulting strip solution is then processed to decrease Cr(VI) to a concentration similar to that in the feed solution in Step (1), for recycling back to the feed solution in Step (1), by the use of a new strip solution which results in a highly concentrated Cr(VI) solution, said supported liquid membrane comprising an amine. The highly concentrated Cr(VI) solution is a product of this process which contains no sulfate or a low level of sulfate and is suitable for reuse or resale. Therefore, this process not only solves the environmental problem but also recovers the chromium.
REFERENCES:
patent: 4051230 (1977-09-01), Miyauchi
patent: 4956154 (1990-09-01), Magdics et al.
Chaudry, et al., “Supported Liquid Membrane Technique Applicability for Removal of Chromium from Tannery Wastes,”Waste Management, vol. 17, No. 4, pp. 211-218 (1997).
Chiarizia, Application of Supported Liquid Membranes for Removal of Nitrate, Technetium (VII) and Chromium (VI) from Groundwater,J. Membr. Sci., vol. 55, pp. 39-64 (1991).
Chiarizia, et al, “Removal of Inorganic Contaminants from Groundwater, Use of Supported Liquid Membranes,”Environmental Remediation: Removing Organic and Metal Ion Pollutants, ACS Symposium Series 509, American Chemical Society, Washington, D.C. pp. 22-33 (1992).
Chiarizia, “Stability of Supported Liquid Membranes Containing Long-chain Aliphatic Amines as Carriers,”J. of Memb. Sci, vol. 55, pp. 65-77 (1991).
Hodgson, et al., “Demonstration of Technologies to Remove Contamination from Groundwater,” Proceedings of the Third International Conference on New Frontiers for Hazardous Waste Management, Westinghouse Hanford Co., Richland, WA (U.S.), Report No. CONF-890927, pp. 26-34 (Sep. 10-13, 1989).
Loiacono, et al., “Metal Ion Separation and Concentration with Supported Liquid Membranes,”J. Membr. Sci., vol. 28, No. 2, pp. 123-138 (1986).
Molinari, et al., “Stability and Effect of Diluents in Supported Liquid Membranes for CR (III), CR (VI), and CD (II) Recovery,”Sep. Sci. Technol., vol. 24, No. 12, pp. 1015-1032 (1989).
Bos Steven
Commodore Separation Technologies Inc.
Kilpatrick & Stockton LLP
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