Effect of lime (CaOH+) on chalcopyrite-arsenopyrite separation in high gradient magnetic separation: Experiment and molecular simulation

Abstract

During the flotation of chalcopyrite from arsenopyrite, the addition of lime (with CaOH+ as the active component) can affect the subsequent high-gradient magnetic separation (HGMS) performance. However, this issue has been overlooked in previous researches. The present study confirms this effect and elucidates its underlying mechanism. Findings demonstrate that CaOH+ could decrease the magnetic moment of Fe atoms in chalcopyrite, deteriorating its separation from arsenopyrite via HGMS method. For a high-arsenic copper ore assaying 0.63 % Cu and 0.78 % As with chalcopyrite and arsenopyrite as the dominant copper-bearing and arsenic-bearing minerals, the HGMS results has confirmed that increasing the lime dosage from 0 kg/t to 14 kg/t reduced the copper grade in the copper concentrate from 0.92 % to 0.61 % and decreased the copper recovery from 67.03 % to 53.95 %. However, the arsenic grade and recovery in the concentrate were improved from 0.35 % to 0.64 % and from 28.27 % to 42.19 %, respectively. The calculations using Density Functional Theory and Crystal-Field Theory revealed that the interaction between Fe ions in chalcopyrite and CaOH+ in lime leads to a considerable change in the single electron occupancy of the d orbitals, that is, it transitions from a high-spin state to a low-spin state; thus, the magnetic susceptibility of the chalcopyrite decreases, reducing the HGMS efficiency for separation of chalcopyrite from arsenopyrite. The findings of this study provide considerable theoretical insights and improved understanding for the effect of lime on the chalcopyrite-arsenopyrite separation efficiency in HGMS process.