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In the mid 1980's, work was undertaken to develop a gallium processing operation
using the high gallium content waste product from elemental phosphorous plants.
At that time, the gallium was intended for use by Monsanto’s Electronic Materials
group for gallium-arsenide chip manufacturing. Testwork included developing an
acid leach process for making phosphoric acid, extracting the gallium from this
phosphoric acid by solvent extraction, purifying the gallium by ion exchange and
electrowinning. Silver was also recovered from the leach residue using cyanide
leaching and Merrill-Crowe processing.
The lab and Monsanto’s Electronic Materials group worked together to develop a
solvent extraction technique. From this, both Monsanto and N. A. Degerstrom
developed unique processes on which individual patents were issued.
A full-scale commercial processing plant was installed in Idaho in 1990 and
was operated for a short period of time until the price of gallium dropped
to such a low level that it made the processing uneconomic.
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