Cobalt loss due to iron precipitation in ammoniacal carbonate solutions

Restrictions in the proportion of recoverable cobalt from laterite ores in the Caron process are attributed to multiple effects. One of these is adsorption of cobalt solution species on the precipitated iron oxide phase. Cobalt loss to an iron oxide precipitate produced in an ammoniacal carbonate solution was investigated. Adsorption experiments, both during and after iron precipitation, were conducted under a variety of process conditions. While prior research has focused more on cobalt adsorption on hematite, the primary phase present in the residue was found to be ferrihydrite. Based on significant differences in adsorption capacity between various iron oxide phases, the material present in the residue will make a significant difference in cobalt losses. Cobalt loss was minimised at low iron concentrations, pH 10 and high ammonia concentrations, while temperature (over the range tested) did not display a significant impact on cobalt loss or the precipitated phase.

► Cobalt adsorption on and co-precipitation with iron oxide was conducted in ammoniacal carbonate solutions (simplistic simulation of Caron Process).
► Ferrihydrite was found to be the primary iron oxide phase formed.
► Cobalt adsorption/co-precipitaion higher than observed on hematite.
► Minimum cobalt loss observed at ~pH 10 and highest NH3 concentration.