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.

The surface oxidation of chalcopyrite is one of the most important factors affecting its flotation performance. In this study, a critical oxidation degree is proposed to define “slight” and “significant” oxidation in terms of surface species and chalcopyrite flotation recovery. Slight oxidation enhanced chalcopyrite hydrophobicity, but significant oxidation reduced its recovery apparently. Microthermokinetic measurements indicated that the apparent activation energy (E_a) of chalcopyrite oxidation was reduced from around 173 kJ·mol⁻¹ to 163 kJ·mol⁻¹ when the reaction changed from slight oxidation to significant oxidation when applying H₂O₂. The surface oxidation degree was defined as the ratio of hydrophilic species to hydrophobic species. The highest recovery (94.8%) and contact angle (93°) were achieved at a concentration of 0.1 vol.% H₂O₂, with the lowest oxidation degree of 0.388 being observed. The oxidation degree was correlated to the flotation recovery, with a quantitative relationship (y = −298.81x + 213.05, y and x represent flotation recovery and oxidation degree, respectively, 0.388 ≤ x ≤ 0.618) being established, thereby giving a guideline to better manage chalcopyrite flotation by controlling its surface oxidation and SBX adsorption on chalcopyrite surfaces.

With the continuous development of easily accessible resources, the exploitation of complex mineral resources, metallurgical waste slag containing high-value metals, and secondary resources is gradually becoming a mainstream trend. Due to the complex distribution characteristics of elements in these resources, efficient recycling is difficult to achieve. A phase reconstruction strategy has been proposed to address the distribution forms of elements. The phase reconstruction strategy employs pyrometallurgical methods to subject complex resources to high-temperature smelting and cooling crystallization. In the cooling crystallization process, the target elements in melt are selectively enriched into engineered artificial minerals (EnAMs). Then, the target elements can be recovered by subsequently separating these EnAMs. However, the concept of and design strategies for EnAMs are still unclear. In this review, the concept of EnAMs is proposed based on previous studies. This review explores how to design EnAMs by phase equilibrium studies and utilizing geochemical behaviors. Additionally, the application cases of EnAMs in treating challenging tantalum–niobium and rare earth element (REE) resources, secondary resource recycling, and metallurgical slag were collected. Furthermore, the challenges and future perspectives of EnAMs for complex resources are discussed.

This research mainly investigated the flotation kinetics of molybdenite in seawater based on four flotation models. Molybdenite flotation presented an excellent agreement with the first-order model with rectangular distribution. The ultimate cumulative recovery (R_∞) and flotation rate constant (k) of molybdenite decreased in seawater, mainly due to the divalent cations, with the impact of Mg²⁺ being significantly greater than that of Ca²⁺. The addition of sodium silicate (SS) and sodium hexametaphosphate (SH) increased the flotation recovery and rate, probably due to the positive role of dispersants on preventing the attachment of seawater precipitates onto molybdenite surface. In addition, three different stages of flotation kinetics were proposed to reveal the molybdenite flotation for the first time, with the highest flotation recovery and rate being found at Stage I. However, seawater showed a negative role on Stage I, i.e. resulting in a longer duration and lower recovery, as compared to that in pure water. The addition of both SS and SH improved the flotation kinetics at Stage I, with SH being more significant. Therefore, it is more feasible to eliminate the negative effects of seawater on molybdenite flotation at the initial stage (Stage I).