An Investigation of Selective Galena Recovery Following Its Depression
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It is challenging to obtain a final lead concentrate from copper-lead-zinc ores due to the complex mineralogy of the ore and the similar flotation behaviour of minerals within the ore. This study was carried out to investigate a new method of separating lead, found in the form of galena, through the use of the polyamine chelating agent triethylenetetramine (TETA). Fundamental micro-flotation, X-Ray Photoelectron Spectroscopy (XPS), and leaching tests were conducted on pure galena to investigate the ability of TETA to reactivate galena previously depressed using sulphite or dichromate ions. From the micro-flotation and XPS experiments it was found that when galena was depressed using sulphite ions, the addition of TETA resulted in the reactivation of galena and an increase in recovery. However when galena was depressed using dichromate ions, the addition of TETA caused a further decrease in recovery. Leaching experiments showed that lead dichromate is not easily leached by TETA. Bench scale studies were conducted to verify whether TETA could be used to reactivate galena from complex copper-lead-zinc ores. Results for the bench scale experiments were consistent with the fundamental studies. When sulphite ions were used to depress galena, TETA was able to effectively reactivate the galena. However when dichromate was used as the depressant, the addition of TETA did not result in the reactivation and flotation of galena. These findings further suggested that the addition of TETA in the sulphite system resulted in the removal of lead sulphite from the mineral surface. It is believed that this is lead xanthate, being more stable than lead sulphite, remained on the mineral surface, resulting in an increase in hydrophobicity and a subsequent increase in recovery. In the dichromate system, TETA did not remove the lead dichromate bearing hydrophilic product, which is believed to act as a barrier for required xanthate interaction. Interestingly, action of TETA at this stage caused reactivation of other sulphides co-existing with galena. Residual xanthate, which cannot be utilized by depressed galena, promoted stage flotation of sphalerite, pyrite and copper bearing minerals. Removal of these minerals was helpful for further upgrading of galena in the tailings fraction.