Magnetic properties of chalcopyrite and arsenopyrite for high-gradient magnetic separation with Crystal-Field Theory

• Pulsating HGMS achieved effective separation of chalcopyrite from arsenopyrite . • Crystal-Field Theory was applied to reveal the magnetic difference of two minerals. • The separation of the two minerals was explained at atomic and electronic scales. Separating chalcopyrite from arsenopyrite using flotation has been a big challenge due to their similar floatability. However, this challenging condition may be partially solved by employing their difference in magnetic susceptibility. As a matter of fact, pulsating high-gradient magnetic separation (PHGMS), as an environment-friendly and economic strategy, was recently attempted to remove arsenopyrite from chalcopyrite with considerable performance. In this study, the magnetic difference of chalcopyrite and arsenopyrite was confirmed using the Density Functional Theory (DFT) calculation and the Vibrating Sample Magnetometer (VSM) measurement. The results indicated that the two minerals possess significant magnetic property difference, and the chalcopyrite has a much larger magnetic susceptibility than that of arsenopyrite. The theoretical analysis based on the Crystal-Field Theory revealed that the difference was resulted from their spin state of d electrons in Fe ions. This has been further demonstrated by the separation performance of a cyclic PHGMS separator in separating a pure chlacopyrite-arsenopyrite mixture, which assays 15.69% Cu and 22.66% As. Under the optimized conditions, the separator produced a chalcopyrite concentrate assaying 20.25% Cu and 9.92% As, with 79.07% Cu and 26.82% As recovered respectively; in the non-magnetic product, the Cu grade was reduced to 8.48% and the As grade was improved to 42.83%. This investigation has demonstrated a potential perspective for the environmental-friendly and economic removal of arsenopyrite from chalcopyrite using PHGMS method.