Solvent extraction – electrowinning (often referred to as "SX–EW") is a process frequently applied for recovering copper from low-grade and/or oxidised copper ore. It involves leaching the copper from the ore using an acidic solution, collecting the leach liquor containing the copper and contacting this solution with an organic extractant. The copper ions in the leach liquor transfer to the organic extractant, moving from a relatively low concentration to a higher concentration. The extractant is subsequently brought into contact with a second aqueous solution that is more acid than the original leach liquor, and the copper again moves, this time from the extractant into the aqueous solution. The result is an acidic solution of copper in which the copper concentration is high enough for it to be recovered by electrowinning. The solution destined for electrowinning is known as the electrolyte.
The electrolyte solution usually contains traces of the organic extractant that exist as tiny droplets within it. These need to be removed before the copper can be recovered in the electrowinning process, as the presence of minimal amounts of the extractant can cause difficulties by stripping and damaging the cathodes with a subsequent loss of cathode copper quality.
In the late 1980s, MIM built an SX–EW plant at Mount Isa to recover copper leached from low grade ore stockpiled while mining its Black Rock open cut in the 1960s. In a world first, a Jameson Cell was used to clean the electrolyte solution by removing the remaining organic solvent. This replaced the sand filters traditionally used.
The cell was 3 m high, twice the height of the early Cells used in MIM's lead–zinc concentrators, as it was thought that additional residence time would enhance recovery. It used a single downcomer. The downcomer was used to contact the electrolyte with air and the droplets of the organic extractant attached themselves to the air bubbles created in the downcomer.
After some initial modifications to the orifice size, the Cell was able to remove 70–90% of the entrained organic extractant.