COLEX process
method of isotopic separation of lithium-6 and lithium-7
The COLEX process (or COLEX separation) is a chemical method of isotopic separation of lithium-6 and lithium-7, based on the use of mercury. COLEX stands for column exchange.
Since the beginning of the atomic era, a variety of lithium enrichments methods have been developed (such as chemical exchange, electromagnetic, laser, centrifugal) and the COLEX process has been the most extensively implemented method so far.
Early development
In the US, several chemical exchange methods for lithium isotope separation have been under investigation in the 1930s and 1940s to develop a process for lithium-6 production, so that tritium could be obtained for thermonuclear weapons research.
The system finally selected was the COLEX process, with aqueous lithium hydroxide (LiOH) contacted with lithium-mercury amalgam. This process was initially used in the US between 1955 and 1963 in the Y12 plant in Oak Ridge, Tennessee. The COLEX plants in Oak Ridge had a very rough start in 1955 with major problems in this entirely new, complicated, and potentially hazardous technology. Stockpiles of lithium-6 and lithium-7 from that period have been available until recently to meet the relatively small domestic and world demand
Since then, due to environmental concerns, the US has stopped lithium enrichments operations in 1963.
South Africa also built a pilot plant using the COLEX method to make lithium-6 for its nuclear weapons program in the 1970s.
Lithium isotopes and uses
Natural lithium contains about 7.5% lithium-6 ( 63Li ), with the rest being lithium-7 ( 73Li ).
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