Study on the Mechanism of an Eco-Friendly Galena Depressant in the Flotation Separation of Chalcopyrite from Galena

The similar surface characteristics of chalcopyrite and galena make their separation challenging during flotation, and finding an effective galena depressant is crucial for mineral recovery. In this study, C₂H₅O₆P was used as a depressant in the flotation separation of chalcopyrite and galena. The results of single-mineral tests showed that under conditions of a pulp pH of 8, a C₂H₅O₆P concentration of 1.8 × 10^-5 mol/L, and an <i>O</i>-isopropyl-<i>N</i>-ethyl thionocarbamate (IPETC) concentration of 1 × 10^-5 mol/L, the recovery of galena was only 5.24%, whereas that of chalcopyrite was 94.36%. In artificial mixed ore tests, flotation results showed chalcopyrite and galena recovery rates of 92.69 and 6.04%, respectively, which confirm the effectiveness of C₂H₅O₆P in separating the two minerals. Contact angle measurements and local electrochemical impedance spectroscopy tests indicated that although C₂H₅O₆P can adsorb on chalcopyrite and galena surfaces, it only depresses the subsequent adsorption of collector IPETC on galena. Fourier transform infrared spectroscopy and time-of-flight secondary ion mass spectrometry analyses further confirmed that C₂H₅O₆P interacts with the mineral surfaces via its P═O group. X-ray photoelectron spectroscopy, inductively coupled plasma, and density functional theory calculations showed that C₂H₅O₆P adsorbs on the Cu sites of chalcopyrite and on the Pb sites of galena via its P═O functional group.