Claims
- 1. A cold trap useful for the purification of the effluent formed in a photochemical mercury enrichment reactor during the operation thereof, which enables the separation of the effluent, which contains both .sup.196 Hg and one or more of the particulate mercury compounds selected from the group consisting of Hg.sub.2 Cl.sub.2 and HgO,
- said cold trap comprising in combination two concentrically arranged glass tubes, a smaller (inner) and open tube surrounded by a larger closed outer tube with the peripheral space between the inner and outer tubes being at least partially filled with glass packing, wherein the temperature within the trap, T.sup.p, is sufficiently low such that most of the effluent Hg condenses at the point of junction between the open end of the inner tube.
BACKGROUND OF THE INVENTION
This is a divisional of copending application Ser. No. 07/289,640 filed on Dec. 23, 1988.
The present invention is directed to a method and apparatus useful in conjunction with the isotopic enrichment of a predetermined isotope of mercury (Hg) from a naturally occurring mercury mixture. While the present invention may be used in conjunction with the enrichment of any one of the seven naturally occurring isotopes of mercury (.sup.202 Hg, .sup.200 Hg, .sup.199 Hg, .sup.201 Hg, .sup.198 Hg, .sup.204 Hg, and .sup.196 Hg,) it has particularly advantageous application in conjunction with the enrichment of the .sup.196 Hg isotope, which has a natural abundance of only about 0.146 percent.
Many devices utilize mercury in their operation, particularly in the field of electric lamps and lighting. Such devices include arc discharge lamps which typically employ mercury as one of the vaporizable components therein. See, for example, Waymouth, Electric Discharqe Lamos, MIT Press 1971 for a description of the basic principles of such lamps.
In U.S. Pat. No. 4,379,252, (the '252 patent), the advantages of utilizing higher than normal levels of .sup.196 Hg in the Hg added to fluorescent lamps are described and include unexpectedly high efficiency gains in light output. The disclosure of this patent is hereby incorporated herein by reference.
The drawback of using this isotope lies in its high cost. For example, using conventional enrichment techniques, mercury which has been enhanced to contain about 35% of the .sup.196 Hg isotope can cost about $500 per milligram. While only sub-milligram quantities of this isotope need be added to an incandescent lamp to afford beneficial results, economic realities always play a part in consumer products. Accordingly, it is easy to understand why more economical methods of obtaining this isotope continue to be sought.
Isotopically enriched mercury can be produced by a number of methods. One method involves photosensitized chemical reactions utilizing elemental mercury and various compounds. The compounds HCl and O.sub.2 react with mercury atoms when the mercury atoms are excited by resonance radiation, in particular, 2537.ANG. radiation produced in a Hg (.sup.3P - .sup.1 S.sub.o) transition generating isotopically selective reactions. Thus, the Hg compound formed contains Hg enriched in a particular isotope, and the Hg must be separated from the compound into its free state in order to recover the isotopically enriched metal.
Although it has been possible to separate mercury from mercury compounds by a number of techniques, previously employed techniques suffer from significant disadvantages. For example, it has been possible to separate Hg from Hg.sub.2 Cl.sub.2 via electroless methods using a mixture of methanol and HCl as an electrolyte solution. However, this method produced low yields and the electrolyte solution had a tendency to become contaminated with impurities and to become blackened and corroded.
Hg can also be separated from HgO via thermal decomposition. However, this requires high temperature baking [T>500.degree. C.]and it can easily result in the introduction of trace impurities into mercury. Additionally, vacuum baking at high temperatures requires hardware and techniques that are very complex.
The following additional documents are recited as general background information with respect to the subject matter of the present invention. To the extent deemed necessary by artisans of ordinary skill in the art to which this invention pertains, the teachings of these documents are hereby incorporated herein by reference.
It has been discovered that most effluent samples from a .sup.196 Hg photochemical isotope enrichment processes forming Hg.sub.2 Cl.sub.2 as a product, contain mercury with varying trace quantities of particulate mercurous chloride, Hg.sub.2 C1.sub.2. Particularly in the case of multipass systems where the feedstock is enriched in .sup.196 Hg for all but the first pass this trace impurity needs to be removed. This is true since the effluent in all but the first pass could have an .sup.196 Hg concentration higher than natural mercury and thus should be re-used in a feedstock.
Thus, the present invention is directed to a method of purifying such contaminated mercury effluents, by the use of mechanical filtering means e.g. thin glass tubes, for the removal of the particulates such as Hg.sub.2 Cl.sub.2, from this effluent mercury. It has also been discovered that ultrasonic rinsing with acetone (dimethyl ketone) and a specially designed cold trap are also particularly effective in removing this Hg.sub.2 Cl.sub.2 contamination from such mercury effluents.
STATEMENT OF GOVERNMENT INTEREST
The Governement of the United States of America has rights in this invention pursuant to Subcontract 4540710 under Prime Contract DE-AC03-76SF00098 awarded by the Department of Energy.
US Referenced Citations (1)
| Number |
Name |
Date |
Kind |
| 3983019 |
Botter et al. |
Sep 1976 |
|
Non-Patent Literature Citations (1)
| Entry |
| Corning Labware, (1977); 42nd Edition, Corning Glass Works; Corning, N.Y., p. 182. |
Divisions (1)
|
Number |
Date |
Country |
| Parent |
289640 |
Dec 1988 |
|
Patent Grant
5031883
