Siyu Chen

The selective separation of sphalerite from Fe-bearing sulphides remains a persistent challenge in the flotation of complex sulphide ores and can lead to Zn misreporting to Fe-bearing concentrates. This study aimed to identify the origins of Zn misreporting to a pyrite concentrate and to evaluate whether regrinding-assisted flotation could mitigate Zn misreporting. XRF, XRD, zinc phase analysis, flotation experiments, and process mineralogical characterisation were used to determine Zn deportment and evaluate the effect of regrinding on mitigating Zn misreporting to the pyrite concentrate. The results showed that the Zn was mainly associated with sphalerite rather than water-soluble Zn species. Reagent adjustment and additional cleaning stages reduced Zn misreporting moderately, but were insufficient to fully separate Zn-bearing phases from the pyrite concentrate. Process mineralogical characterisation further revealed that Zn was predominantly hosted in sphalerite, which commonly occurred as attached, locked, or disseminated particles associated with pyrite. Under the same Na₂SiO₃ dosage, regrinding-assisted flotation reduced the Zn grade in the final pyrite concentrate from 0.29% to 0.14%, indicating reduced Zn misreporting. These findings indicate that close sphalerite–pyrite association and incomplete sphalerite liberation were the principal mineralogical factors governing Zn misreporting, while regrinding-assisted flotation provides a practical approach for reducing Zn misreporting to pyrite concentrates. This study provides a process mineralogy-guided approach for diagnosing Zn misreporting and improving impurity control in pyrite-rich concentrate production.

Imidazole-based ionic liquids hold immense potential in the field of mineral flotation due to their tunable properties. In this study, three imidazole-based ionic liquids with varying carbon chain lengths (OMB, DMB, and HMB) were selected as collectors for quartz flotation to systematically investigate the microscopic mechanisms by which carbon chain length influences the agglomeration and flotation behavior of quartz. Flotation tests and online particle-bubble monitoring (PBM) results indicate that the elongation of the collector’s carbon chain significantly enhances its collecting ability and reduces the required reagent dosage. To achieve the complete recovery of quartz in a neutral system, a dosage of 35 mg/L is required for OMB, whereas HMB requires only 8 mg/L. As the carbon chain lengthens, the optimal pH range for highly efficient flotation shifts from alkaline to neutral-acidic. Interfacial measurements and mechanistic analyses (Zeta potential and FTIR spectroscopy) confirm that the imidazole ring of the collector physically adsorbs onto the quartz surface through the synergistic action of electrostatic forces and hydrogen bonding, thereby inducing the hydrophobic agglomeration of particles. Notably, in a strongly alkaline system (pH = 11), the long-chain HMB promotes the formation of oversized quartz agglomerates. This leads to a depletion of free reagents in the liquid phase and destabilizes the bubble liquid film, ultimately triggering a sharp decline in recovery. Density functional theory (DFT) calculations further corroborate the structure–activity relationship at the molecular level: the extension of the carbon chain increases the highest occupied molecular orbital (HOMO) energy and electron-donating ability. The adsorption energy of HMB on the quartz (001) surface reached −350.2 kJ/mol, exhibiting the strongest solid–liquid interfacial affinity. This study elucidates the competitive mechanism of carbon chain length in regulating electrostatic adsorption, hydrophobic agglomeration, and froth stability, providing a solid theoretical foundation for the molecular design of novel green flotation reagents for quartz.

Quartz and feldspar have similar physical, chemical, and surface properties. Effectively separating them in near-neutral systems has long been a challenging research focus. This study introduces 1-Dodecyl-3-methylimidazolium bromide (DMB), an ionic liquid, as a collector in a quartz–feldspar flotation separation system to investigate its effects on the flotation behavior of quartz and feldspar. The interaction between the collector and the minerals is explained through zeta potential measurements, infrared spectroscopy analysis, and DFT calculations. The flotation test results indicate that DMB exhibits selective flotation separation properties enabling the separation of quartz from feldspar. Across the pH range of 3 to 11, DMB demonstrates high collection capability for quartz, but lower capability for feldspar. In particular, at pH levels of 7 to 8, the recovery difference between the two minerals exceeds 80%, achieving optimal selective separation. Mechanistic studies indicate that DMB primarily adsorbs on quartz and feldspar through electrostatic adsorption. The adsorption energy between DMB and quartz reaches −340.59 kJ/mol, forming a stable adsorption layer on the quartz surface. However, electrostatic repulsion arises over a broad area due to the large volume and cationic nature of DMB’s polar group and the exposed cationic Al sites on the feldspar surface, thereby hindering the interaction between DMB and feldspar. This research establishes the foundation for achieving efficient selective flotation separation of quartz and feldspar in a neutral system.