The oxidative flotation separation of chalcopyrite from pyrite in weak alkaline seawater solution was investigated using potassium ferrate (K₂FeO₄) as the oxidizing reagent. The optimal K₂FeO₄ concentration of 0.25 kg/t was found to strongly depress pyrite (from 88.05% to 7.92%) but insignificantly influence chalcopyrite (remaining at around 93%). K₂FeO₄ oxidized pyrite to form hydrophilic Fe₂O₃, Fe(OH)₃, FeOOH, and Fe₂(SO₄)₃ that covering on pyrite surface to prevent the adsorption of collector sodium butyl xanthate (SBX), thereby depressing pyrite flotation. Although a small amount of hydrophilic species was formed on chalcopyrite surface after the addition of K₂FeO₄, some hydrophobic substances such as S₂^2-/S_n^2-/S⁰ were also observed, resulting in an unaffected overall floatability. Further, density functional theory (DFT) calculation proved that the activity of Fe on chalcopyrite surface was much lower than that on pyrite. Therefore, this study provides a green way to separate chalcopyrite from pyrite effectively in a low-alkali seawater system, which is of significance to the separation of sulfide minerals in the fresh water-lack areas.

Seawater has been increasingly used as an alternative to freshwater in mineral flotation. Although previous studies suggest that Mg²⁺ ions in seawater have the primary negative roles in chalcopyrite flotation, insufficient work has been conducted to understand the effects of kerosene as a collector in chalcopyrite flotation. In this study, the influence of kerosene emulsion on chalcopyrite floatability in a solution containing Mg²⁺ was systematically investigated. The results indicated that the addition of kerosene significantly reduced the adsorption of hydrophilic Mg-precipitates onto the chalcopyrite’s surface. In addition to contact angle, zeta potential, optical microscopy, and Fourier-transform infrared spectroscopy analyses, extended Derjguin–Landau–Verwey–Overbeek (EDLVO) theory and density functional theory (DFT) calculations were conducted to understand the influencing mechanisms of kerosene on chalcopyrite flotation. The adsorption energies showed an order of kerosene and Mg(OH)₂ > kerosene and chalcopyrite > chalcopyrite and Mg(OH)₂, indicating kerosene was preferentially adsorbed on the Mg(OH)₂ surface, forming agglomerates and therefore reducing the adsorption of Mg(OH)₂ precipitates onto the chalcopyrite’s surface. In addition, hydrophobic agglomerates were also formed due to the attachment of kerosene to the chalcopyrite’s surface when additional kerosene was added, further enhancing chalcopyrite floatability.

Due to the shortage of freshwater, seawater has been widely considered for mineral flotation. However, the presence of Mg²⁺ in seawater plays an apparently negative role. In this work, two dispersants (i.e., sodium silicate (SS) and sodium hexametaphosphate (SH)) were applied to reduce the detrimental effects of Mg²⁺ on the flotation of molybdenite (MoS₂). Various measurements including contact angle, zeta potential, FTIR and XPS were carried out to understand the impacts of these two dispersants on MoS₂ flotation. Results indicate that both dispersants prevented the adsorption of colloidal Mg(OH)₂ onto MoS₂ surface under alkaline conditions, thereby improving MoS₂ floatability. In addition, both dispersants are physically adsorbed on MoS₂ surface, but chemically adsorbed on Mg(OH)₂ surface. In addition, the extended Derjaguin–Landau–Verwey–Overbeek (DLVO) calculation suggests that both SS and SH reverse the total interaction energies between MoS₂ and colloidal Mg(OH)₂ from negative (attraction force) to positive (repulsive force), with the impact of SH being more significant.

Chalcopyrite (CuFeS₂) particles, exposing anisotropic crystal planes during the grinding process, possess comprehensive surface properties that affect their leaching behaviors. In order to investigate the influence of anisotropic crystal planes on the leaching mechanisms, CuFeS₂ particles with anisotropic crystal planes were produced by employing three-head laboratory grinder mill (TM), rod mill (RM), and ball mill (BM) and were then leached in a sulfuric acid solution at pH = 1. Based on the XRD, SEM, XPS, and simulation results, (112), (102), (312), (110), (116), (100), and (001) planes were mainly exposed on the CuFeS₂ surface during the crushing and grinding process. In addition, fewer (112), (102), (312), and (110) planes but more (116), (100), and (001) planes were exposed on the CuFeS₂ samples in the TM method than in the RM and BM methods. Since the leaching rates were in the order of (001) > (100) > (116) > (110) > (312) > (102) > (112) planes, the Cu extractions followed an order of TM > RM > BM. This study, therefore, provides an excellent theoretical basis for the effect of anisotropic crystal planes on CuFeS₂ leaching, further improving the understanding of CuFeS₂ leaching mechanisms.