Chemistry: electrical and wave energy – Processes and products – Electrophoresis or electro-osmosis processes and electrolyte...
Reexamination Certificate
1999-01-22
2001-04-10
Phasge, Arun (Department: 1741)
Chemistry: electrical and wave energy
Processes and products
Electrophoresis or electro-osmosis processes and electrolyte...
C204S600000, C205S687000, C205S742000, C588S253000
Reexamination Certificate
active
06214189
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and an apparatus for electro-kinetically decontaminating the soil contained in a radioactive waste drum.
2. Description of the Prior Art
Patent applications for the technique similar to the present invention have been filed since 1989, and the last patent was issued in 1998 under U.S. Pat. No. 5,725,752.
Between 1981 and 1985 in the United States, there were developed a method for extracting water from a sludge by using a dynamic electric current, a method for drying wet soil, and a method for adjusting the water flow amount or for reversing the water flow direction. Patents were issued for these techniques (U.S. Pat. Nos. 4,305,800, 4,382,341, and 4,479,857). Between 1976 and 1993 in Japan, a method for extracting water from soil was developed, and patents were issued (02136435 JP A1). Besides the environmental industries, the Hewlett-Packard company utilized the electroosmosis to develop an ink distribution unit for the ink jet printer. Patent applications for this technique were filed in the U. S. and Japan.
To describe the patents related to the present invention, R. F. Probstein et al. filed a patent application in 1989, and obtained a patent in 1991 (U.S. Pat. No. 5,074,986). The technique was on decontaminating the soil site, and the title of the invention was “Electroosmosis Techniques for Removing Materials from Soil”. The main claim was on electrically decontaminating the contaminated soil site, and the related claims were on the voltage gradients, on the electrodes, and on the purging liquid supply method.
Almost simultaneously with R. F. Probstein et al., Y. B. Acar et al. obtained a patent (U.S. Pat. No. 5,137,608) under the title of “Electrochemical Decontamination of Soils or Slurries”. The total number of claims were 33, and the technique was on an inert anode (containing graphite) and a non-reactive cathode (containing graphite). The object to be decontaminated is metals (such as Pb ions), organic materials, and radioactive nuclides. The Pb ions are recovered at the cathode. The main electrochemical process within the soil includes the steps of: (1) transmitting direct electric current through the soil between an inert anode and non-reactive cathode; (2) supplying a first liquid which comprises water to the soil near said anode; and (3) introducing a nutrient into the soil thorough electroosmosis.
J. P. Bibler obtained in 1993 a patent under the title of “Method and Apparatus for Removing Ions from Soil” (U.S. Pat. 5,190,628). The technique is on selectively removing ions from the soil. That is, a permeable membranes impregnated with an ion exchange resin that is specific to one or more species of chemical ions are inserted into ground. Then electrodes are installed near the membrane, and a voltage is supplied to them. Preferably, the resin exchanges ions of sodium or hydrogen for ions of metal that it captures from soil area. When the permeable membrane is saturated with the metal ions, the potential applied across electrodes is discontinued and membranes are preferably removed from soil for storage or recovery of the ions. The claims state the following matters. That is, there is provided a method for removing one or more species of ions from an area of soil groundwater. That is, (1) placing at least two electrodes in spaced relation with respect to each other and to said area of soil; (2) placing a permeable barrier adjacent each of said at least two electrodes and said area of soil, said barrier adapted to pass said groundwater, said barrier carrying an ion exchange resin, said resin being selective for said at least one species of ions; and (3) applying a potential across said electrodes, said potential causing said at least one species of ions to migrate with respect to said electrodes, thereby allowing said ion exchange resin carried in said permeable barrier to capture said species. The main species removed is assumed to be a mercury ion, and at least two titanium electrodes are installed. The first and second membranes are spaced approximately 10 feet apart and said electric potential is approximately 60 volts DC.
H. R. Chang et al. obtained a patent in 1993 under the title of “Surfactant Augmented In-situ Removal of Poly-chloro-benzenes from Soil by Electroosmosis” (U.S. Pat. No. 5,240,570). In this method, the contaminants such as poly-chloro-benzenes are electro-osmotically extracted from soil at the contamination site. By adding a low concentration surfactant solution, the decontamination capability is reinforced.
R. A. Jacobs obtained a patent in 1995 under the title of “Removal of Contaminant Material from a Soil Site” (U.S. Pat. No. 5,415,744). In this method, at least one anode is positioned in the soil site, and a plurality of cathodes are disposed around the anode. Then a voltage gradient is established between the anode and the cathodes. Owing to the electroosmosis, the solution at the anode moves to the cathodes. That is, the contaminant materials are moved together with the solution, and are removed at the cathodes. The total number of the claims was 19, and the method includes the steps of: (1) positioning one anode at a first location within said soil site; (2) positioning a plurality of only cathodes at second locations around said anode; (3) establishing voltage gradients between said anode and the said plurality of cathodes; (4) supplying a non-contaminated solution to the anode so as to make the solution and the contamination substances move toward the cathodes; and (5) removing said material from said cathodes. Here, the number of the cathodes should be at least three, and the cathodes should be disposed symmetrically relative to the anode. The cathodes are disposed in a circular form. At the step
5
, the solution together with the contamination substances can be removed through separate paths for the respective cathodes, or can be combinedly removed.
W. Pool of Netherlands obtained a patent in 1995 under the title of “Process for the Electroreclamation of Soil Material” (U.S. Pat. No. 5,433,829). The content of this invention is similar to the other ones, but is characterized in that: (1) one or more anodes and one or more cathodes are used, and different levels of voltages are applied between different electrodes; and (2) the contaminants are removed both at the anode and at the cathode unlike the other inventions. The total number of claims was 11. Claim 1 defines as follows. That is, an anode and a cathode are installed within a soil which is contaminated with heavy metals and cyanides. Then an electric current is made to flow between the electrodes so that the contaminants would be gathered to the electrodes. Specifically, claim 1 includes the steps of: (1) inserting an electrode into a porous container to make the electrode serve as an anode (or a cathode) so as to make an electric current flow between this electrodes and another electrode (cathode or anode); (2) installing the electrode into the soil; (3) injecting an electrolytic solution into the electrodes through a cathode circulation system and through an anode circulation system; (4) supplying a dc current to the electrodes to make the contamination substances move to the electrodes (electro-migration); and (5) removing the contamination substances from the anode and the cathode.
Further, continuous adjustments are carried out on the pH level of the circulation system, the electrical conductivity, temperature and current density within the solution. Other claims contain the following contents. That is, an acid is added to adjust the acidity of the solution so as to improve the decontamination effect. The anode is made of a noble metal, and the cathode is made of graphite. The heavy metals to be removed are ions of Cu, Pb, Zn, Ni, Co, Fe, Sr, Mg and Ca. In this method, the migration of the contaminants can also be prevented by the application of electrical method.
R. J. Griffith et al. obtained a patent in 1996 under the title of “Electric Field Method And Apparatus for dec
Ahn Byung-Gil
Jung Chong-Hun
Kim Gye-Nam
Kwon Hoy-Sam
Lee Byung-Jik
Arent Fox Kinter Plotkin & Kahn PLLC.
Korea Atomic Energy Research Institute
Phasge Arun
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