A STUDY OF THE PYRRHOTITE DEPRESSION MECHANISM BY DIETHYLENETRIAMINE

Diethylenetriamine (DETA) is a selective depressant for nickeliferous pyrrhotite during pentlandite flotation. Laboratory flotation tests co nducted on ore and process samples showed that pyrrhotite rejection is greatly improved by small additions of DETA; however, the effectivene ss of this depressant is most noticeable when the mineral sample is ox idized. LIMS and XPS analyses conducted on flotation products and pyrr hotite specimens showed that the difficulty in pyrrhotite rejection ar ises from inadvertent activation of the mineral by heavy metal ions, s uch as Ni2+, Cu2+ and Ag+, that are present in the process water. In t he presence of DETA, however, the mineral is deactivated under oxidizi ng conditions. The deactivation mechanism may involve oxidation of the activation products, which are likely in the form of heavy metal sulf ides, followed by solubilization by DETA. FTIR spectra of pyrrhotite e lectrodes contacted with DETA showed no trace of the reagent on the su rface substantiating the view that its role is one of complexing agent that enhances the dissolution of activation products under oxidizing conditions. FTIR spectra of pyrrhotite contacted with amyl xanthate so lutions showed that both dixanthogen and iron xanthate are formed on t he surface, the latter becoming more predominant at higher potentials. In the presence of DETA, however, only a small amount of xanthate is adsorbed on the mineral at potentials (E(h)) approximately 200 mV high er than the case without DETA.