A short history of hydrometallurgy

Thousands of years ago people had learned how to build furnaces and use fire to melt rocks and produce metals but the use of aqueous solutions for ore processing came much later, mainly at the time of the alchemists when acids and alkalies became known and used. Modern hydrometallurgy, however, can be traced back to the end of the 19th century when two major operations were discovered: the cyanidation process for gold and silver extraction and the Bayer process for bauxite treatment. Later, in the 1940s, a breakthrough came during the Manhattan Project in USA in connection with uranium extraction. Since then, it has been advancing progressively and even replacing some pyrometallurgical processes. Canadian contribution is significant particularly in the recovery of uranium, nickel, cobalt, and zinc.