UBC Theses and Dissertations
Cobalt adsorption and/or co-precipitation onto ferric oxyhydroxide Su, Lun Wei
The Caron process was developed in the 1920s. In this process, the ore is dried and milled, then roasted in a reducing atmosphere to convert nickel and cobalt to their metallic form. Nickel and cobalt are then leached in ammoniacal solution but some losses occur due to adsorption and co-precipitation with iron oxide or hydroxide precipitates. The effects of various parameters on iron precipitation in the Caron process leach were studied. The parameters studied include pH, temperature, contact time with iron and its precipitates and initial ferrous concentration. The adsorption of otherwise soluble Co onto freshly precipitated ferric hydroxide was measured at four different temperatures between 20ºC and 35ºC. The percentage of cobalt adsorbed onto iron precipitates was directly related to the initial iron concentration but the effect of temperature was less clear. The amount of cobalt adsorbed depended on the pH. Solution contact time with iron precipitates had a very small effect on cobalt adsorption (2-3% difference). The highest adsorption of cobalt (99%) was obtained with an initial concentration of 0.2 M ferrous sulfate at pH 7 after 2 hours of contact time. The main iron precipitate was ferrihydrite. X-ray analysis revealed the characteristic “2 line” ferrihydrite (Fe₅HO₈4H₂O) with no goethite being observed in any of the precipitates. TEM revealed an amorphous structure, which is also indicative of ferrihydrite. SEM showed a preponderance of poorly resolved precipitates, which did not appear to be crystalline. Traces of cobalt were measured in the ferrihydrite particulate by EDX.
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