Electrolysis: processes – compositions used therein – and methods – Electrolytic material treatment
Patent
1996-11-15
1999-09-21
Phasge, Arun S.
Electrolysis: processes, compositions used therein, and methods
Electrolytic material treatment
205688, 205746, 205753, 205754, 205758, 205760, 204551, 204267, 204269, 204275, 204284, 204294, C02F 1461, B01D 1508
Patent
active
059549378
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrochemical separation method and apparatus for removing ions, contaminants and impurities from water, fluids, and other aqueous process streams, and for placing the removed ions back into solution during regeneration.
2. Background Art
The separation of ions and impurities from electrolytes has heretofore been generally achieved using a variety of conventional processes including: ion exchange, reverse osmosis, electrodialysis, electrodeposition, and filtering. Other methods have been proposed and address the problems associated with the conventional separation processes. However, these proposed methods have not been completely satisfactory and have not met with universal commercial success or complete acceptance. One such proposed ion separation method is a process for desalting water based on periodic sorption and desorption of ions on the extensive surface of porous carbon electrodes.
The conventional ion exchange process generates large volumes of corrosive secondary wastes that must be treated for disposal through regeneration processes. Existing regeneration processes are typically carried out following the saturation of columns by ions, by pumping regeneration solutions, such as concentrated acids, bases, or salt solutions through the columns. These routine maintenance measures produce significant secondary wastes, as well as periodic interruptions of the deionization process. Secondary wastes resulting from the regeneration of the ion exchangers typically include used anion and cation exchange resins, as well as contaminated acids, bases and/or salt solutions.
In some instances, the secondary radioactive wastes are extremely hazardous and can cause serious environmental concerns. For instance, during plutonium processing, resins and solutions of HNO.sub.3 become contaminated with PuO.sub.2.sup.++ and other radioisotopes. Given the high and increasing cost of disposal of secondary wastes in mined geological repositories, there is tremendous and still unfulfilled need for reducing, and in certain applications, eliminating the volume of secondary wastes.
Another example is the use of the ion exchange process for industrial purposes, such as in the electroplating and metal finishing industries. A major dilemma currently facing the industry relates to the difficulties, cost considerations and the environmental consequences for disposing of the contaminated rinse solution resulting from the electroplating process. A typical treatment method for the contaminated rinse water is the ion exchange process.
Other exemplary processes which further illustrate the problems associated with ion exchange include residential water softening and the treatment of boiler water for nuclear and fossil-fueled power plants. Such water softeners result in a relatively highly concentrated solution of sodium chloride in the drinking water produced by the system. Therefore, additional desalination devices, such as reverse osmosis filters are needed to remove the excess sodium chloride introduced during regeneration.
Therefore, there is still a significant and growing need for a new method and apparatus for deionization and subsequent regeneration, which significantly reduce, if not entirely eliminate secondary wastes in certain applications. The new method and apparatus should enable the separation of any inorganic or organic ion or dipole from any ionically conducting solvent, which could be water, an organic solvent, or an inorganic solvent. For example, it should be possible to use such a process to purify organic solvents, such as propylene carbonate, for use in lithium batteries and other energy storage devices. Furthermore, it should be possible to use such a process to remove organic ions, such as formate or acetate from aqueous streams.
The new method and apparatus should further be adaptable for use in various applications, including without limitation, treatment of boiler water in nuclear and fossil power plants, production
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Phasge Arun S,.
Sartorio Henry
The Regents of the University of California
Thomas Alan H.
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