Qiang Song

The flotation separation of cassiterite from calcite has long posed a technical challenge. In this study, λ-carrageenan (NV‐L), an eco-friendly bio-depressant extracted from marine red algae, was innovatively adopted for the selective depression of calcite in cassiterite flotation. Single-mineral micro-flotation test results demonstrated that NV L exerted a robust depressive effect on calcite while exhibiting a negligible influence on cassiterite floatability. Mixed ore flotation further showed that with 80 mg/L NV‐L, the grade and recovery of the cassiterite concentrate attained 66.81% and 86.33%, respectively. T The selective depression mechanism was explored through contact angle measurements, zeta potential analysis, MD simulations, and a combination of spectroscopic techniques including SEM‐EDS, FTIR, XPS, and DFT calculations. The findings reveal that the sulfate ester groups (-OSO3-) of NV‐L coordinate with calcium sites on calcite via S-O- and S=O bonds, accompanied by notable electron transfer and orbital hybridization, which culminate in the formation of stable Ca-O-S linkages. Such chemisorption constructs a dense hydrophilic layer on the calcite surface, whereas adsorption onto cassiterite remains extremely weak, thereby substantially amplifying the wettability contrast and permitting NaOL to exhibit excellent selectivity during cassiterite flotation. In summary, the selective chemisorption of NV‐L onto calcite is the decisive factor enabling the separation of cassiterite from calcite, underscoring its considerable promise for the selective flotation of these two minerals.

To overcome the severe interference of carbonaceous gangue during the flotation of a carbon-rich, low-grade lead–zinc sulfide ore from Danzhai, Guizhou (0.71% Pb, 4.35% Zn, and 4.49% C), while avoiding valuable metal losses associated with pre-decarbonization, a ”direct Pb–Zn sequential flotation without pre-decarbonization” process was developed. In addition, the activation mechanism of a novel complex activator, T-47, was investigated through solution chemistry and surface analyses. The results showed that, at a grinding fineness of 85% passing -200 mesh, efficient preferential recovery of galena was achieved in the lead flotation stage using a flowsheet consisting of one roughing, three cleaning, and one scavenging stages, with Na2SO3 and ZnSO4 as combined depressants and DDTC together with ADD as combined collectors. In the subsequent zinc flotation stage, T-47 (700 g/t) was employed to replace conventional CuSO4 as the activator. Closed-circuit flotation tests produced a lead concentrate with a Pb grade of 40.31% and a recovery of 92.55%, as well as a zinc concentrate with a Zn grade of 43.45% and a recovery of 94.12%, indicating that efficient Pb–Zn separation can still be achieved under high-carbon conditions without pre-decarbonization. UV–Vis analysis indicated that T-47 could form stable copper–ammonia complex species in solution, thereby improving the stability of Cu2+ under alkaline conditions and suppressing its hydrolytic precipitation. XPS results further revealed that, compared with the conventional CuSO4 system, T-47 reduced the surface coverage of oxidized species and hydroxides on sphalerite, promoted the exposure of active sulfur sites, and facilitated the formation of Cu(I)–S activation species. These effects enhanced collector adsorption on the mineral surface and consequently improved the activation efficiency and flotation recovery of sphalerite in complex high-alkaline and high-carbon flotation systems.

The selective separation of chalcopyrite from pyrrhotite is a crucial prerequisite for the efficient utilization of pyrrhotite-rich type copper sulfide ore. In this study, pulp aeration was utilized to depress pyrrhotite and its function mechanism was revealed systematically. Flotation results confirmed that pulp aeration could selectively depress pyrrhotite when utilizing ML-8 as collector, and the Cu/Fe selectivity index was improved to 4.34, thus achieved the efficient separation of chalcopyrite from pyrrhotite. Mechanism research demonstrated that pulp aeration severely increased the surface roughness and wettability of pyrrhotite, but its impact on chalcopyrite was negligible. Furthermore, the rapid surface passivation of pyrrhotite was observed after aeration, its electrochemical impedance increased from 248565 Ω to 262956 Ω, while the conductivity decreased from 1665.42 S/cm to 284.87 S/cm. Likewise, the adsorption of ML-8 on pyrrhotite surface was strongly depressed while that on chalcopyrite was unaffected after surface passivation. In addition, pulp aeration destroyed the galvanic effect between chalcopyrite-pyrrhotite via the selective passivation of pyrrhotite, which promoted chalcopyrite flotation and depressed pyrrhotite, thus chalcopyrite successfully separated from pyrrhotite during actual ore flotation. Ultimately, a galvanic interaction model was established, which provided theoretical support for copper-sulfur separation based on pulp aeration regulation.

The reactivation efficiency of depressed marmatite is a critical determinant of zinc recovery in polymetallic flotation. This study systematically investigates the interfacial behavior of representative inorganic (ZnSO₄, Na₂SO₃) and organic (sodium thioglycolate, guar gum) depressants across the full ”depression–activation–collection” sequence by integrating microflotation with comprehensive surface and electrochemical analyses. The results demonstrate that the depressant-induced surface reconstruction mode directly governs the efficacy of copper activation. Inorganic depressants promote mild surface hydroxylation, forming a loosely structured, low-impedance hydrophilic layer with high reversibility, which enables Cu²⁺ to penetrate and substitute lattice zinc ions, generating highly active hydrophobic Cu(I)–S sites and facilitating efficient flotation. In contrast, organic depressants establish dense interfacial barriers—sodium thioglycolate via chelation and guar gum via thick physical adsorption—inducing a distinct ”pseudo-activation” phenomenon. Despite significant Cu²⁺ adsorption, the copper species are predominantly trapped as inactive, hydrophilic Cu(II)–OH complexes owing to high interfacial impedance and severe steric hindrance, preventing effective collector adsorption and resulting in ”high adsorption, low recovery” flotation failure. This study elucidates the structure–stability–reactivation relationship within the depression layer, offering molecular-level insights into the intrinsic mechanisms underlying the superior performance of inorganic depressants and establishing a theoretical foundation for optimizing reagent schemes in complex sulfide ore flotation.

Using hydrogen peroxide (H₂O₂), a simple and easily accessible reagent, as a selective depressant, flotation separation experiments of chalcopyrite and copper-activated sphalerite were conducted. The micro-flotation tests of single minerals indicated that H₂O₂ selectively depresses copper-activated sphalerite and exerted almost no depressant effect on chalcopyrite. In the flotation tests of artificially mixed minerals, a copper concentrate with a grade of 29.95% and a recovery of 87.30% was obtained, while the zinc content was only 5.76%, demonstrating a significant separation effect. The results of contact angle measurement, Zeta potential measurement, surface adsorption analysis, and XPS analysis suggested that H₂O₂ had a stronger oxidation capacity on the surface of copper-activated sphalerite than chalcopyrite, generating hydrophilic hydroxyl groups on the surface of sphalerite and preventing further adsorption of the collector Z-200 on the surface of sphalerite.

In industrial manufacturing, pyrrhotite(Fe_1−xS), once depressed, is commonly activated for flotation. However, the replacement of CuSO₄ is necessary due to the need for exact control over the dosage during the activation of pyrrhotite, which can pose challenges in industrial settings. This research introduces the use of FeSO₄ for the first time to efficiently activate pyrrhotite. The impact of two different activators on pyrrhotite was examined through microflotation experiments and density functional theory (DFT) calculations. Microflotation experiments confirmed that as the CuSO₄ dosage increased from 0 to 8 × 10⁻⁴ mol/L, the recovery of pyrrhotite initially increased slightly from 71.27% to 87.65% but then sharply decreased to 16.47%. Conversely, when the FeSO₄ dosage was increased from 0 to 8 × 10⁻⁴ mol/L, pyrrhotite’s recovery rose from 71.27% to 82.37%. These results indicate a higher sensitivity of CuSO₄ to dosage variations, suggesting that minor alterations in dosage can significantly impact its efficacy under certain experimental conditions. In contrast, FeSO₄ might demonstrate reduced sensitivity to changes in dosage, leading to more consistent performance. Fe ions can chemically adsorb onto the surface of pyrrhotite (001), creating a stable chemical bond, thereby markedly activating pyrrhotite. The addition of butyl xanthate (BX), coupled with the action of Fe²⁺ on activated pyrrhotite, results in the formation of four Fe-S bonds on Fe²⁺. The proximity of their atomic distances contributes to the development of a stable double-chelate structure. The S 3p orbital on BX hybridizes with the Fe 3d orbital on pyrrhotite, but the hybrid effect of Fe²⁺ activation is stronger than that of nonactivation. In addition, the Fe-S bond formed by the addition of activated Fe²⁺ has a higher Mulliken population, more charge overlap, and stronger covalent bonds. Therefore, Fe²⁺ is an excellent, efficient, and stable pyrrhotite activator.

Fluorite and calcite were separated with nitrilotriacetic acid (NTA) as a depressant. The single mineral flotation experiment confirmed that with 40 mg/L NaOL and 80 mg/L NTA, the fluorite recovery and calcite recovery were 24.37 and 94.13%, respectively, at pH 9. Meanwhile, in the fluorite-calcite binary mixed ore flotation experiment, the calcite recovery and fluorite recovery were 75.50 and 26.84%, respectively, and the CaCO₃ and CaF₂ grade in concentrate was 74.32 and 25.61%, respectively. The results confirmed that NTA could be used as a depressant to selectively inhibit fluorite flotation. The mechanism study illustrated that NTA was selectively reacted with fluorite by chemical interaction between O of NTA and Ca of fluorite. The adsorption of NTA on fluorite will impede the interaction between fluorite and NaOL. NTA could adsorb on fluorite in three ways, while the dominant two ways were the complex between double O of NTA and Ca of fluorite in a vertical model and the complex between double O of NTA and Ca of fluorite in a horizontal model.

In this paper, the adsorption of cyanide and its combination with zinc sulfate on the surface of sphalerite (110) was studied by density functional theory (DFT), and its configurational relationship was analyzed by coordination chemistry. The calculation results show that the adsorption configuration stability of CN⁻ is stronger than that of Zn(CN)₂; the chemical bond of Zn(OH)₂ is less covalent. The three adsorption modes all make the surface of sphalerite lose more electrons, thereby weakening the reactivity of S and Zn atoms on the sphalerite surface. During the CN⁻ adsorption process, both the 3d and 4p orbital peak energy levels of Zn decrease, indicating the strong inhibitory effect of CN⁻. Coordination chemistry also shows that CN⁻ matches the Zn ion orbital in sphalerite and the π electron pair on the Zn ion can easily interact with the empty π orbital on CN⁻ to form π-backbonding.