The characterisation and origins of interphase substances (cruds) in the rhenium solvent extraction circuit of a copper smelter

It has been determined that the reason for the formation of interphase substances (IS) during rhenium extraction is the presence of a black-colored fine precipitate in the feed solution. The same precipitate is formed when extraction process solutions are mixed with the original feed solution, which is wash sulfuric acid from the scrubbing of copper smelter off-gases. The elemental composition of the interphase substances has been determined, including the content of trialkylamine. The precipitate in the original solution is the result of chemical reactions between Re and Os oxides, and SO2 and H2S. It is also the result of the formation of humic acid in the gas phase and in the scrubbing of metallurgical gases.