Mitigating the effect of inevitable Cu2+ by PHGMS for improving chalcopyrite-molybdenite flotation separation performance

Abstract

The release of Cu²⁺ from secondary copper minerals such as bornite and malachite has been a prevalent issue in the chalcopyrite-molybdenite flotation separation, as it significantly impacts the separation performance. This study investigated the depressing effect of Cu²⁺ released from bornite and malachite on chalcopyrite-molybdenite flotation and the adsorption mechanism of sodium sulfide on Cu²⁺ activated molybdenite surface, and the magnetic capture properties of these minerals during the pulsating high-gradient magnetic separation (PHGMS) were compared. The flotation results indicated that Cu²⁺, as the main component in the supernatant of bornite and malachite, significantly depressed the molybdenite in the sodium sulfide kerosene system, reducing its recovery from 84.87 % in deionized water to 60.44 % in the supernatant. The Zeta potential measurements and the Density Functional Theory (DFT) calculations confirmed that HS⁻ was chemisorbed on the molybdenite surface through the bridging effect of Cu²⁺, thus impairing the molybdenite flotation performance. The PHGMS experiments indicated that the recoveries of chalcopyrite, bornite, and malachite in the magnetic concentrate exceeded 90 %, while that of molybdenite was below 10 % at 0.8 T magnetic induction. The verification experiments showed that the recovery of pure molybdenite pre-treated by PHGMS was nearly 20 % higher than that of untreated samples in the supernatant. It is clear the PHGMS pretreatment for porphyry copper-molybdenum ore might effectively mitigate the impact of Cu²⁺ released from bornite and malachite on the chalcopyrite-molybdenite flotation separation, by separating out magnetic copper-containing minerals. This study has fully elucidated the effect of released Cu²⁺ on flotation performance and affirmed the efficacy of PHGMS in mitigating this effect, providing vital insight into the highly efficient and environmentally friendly utilization of porphyry copper-molybdenum ore resources.