[Objective] To clarify the occurrence state and distribution pattern of associated cobalt resources in a high-sulfur bauxite from Guizhou and to guide the synergistic recovery of aluminum, sulfur, and cobalt resources, [Method] a systematic process mineralogy study was conducted using multiple analytical techniques, including multi-element chemical analysis, X-ray Diffraction (XRD), Automated Mineral Identification and Characterization System (AMICS), Electron Probe Microanalysis (EPMA), and optical microscopy. [Result] The main chemical components of the ore are Al2O3 (58.98%), TFe (7.96%), and SiO2 (5.98%), with a Co content of 0.005 9% (59 g/t). The primary mineral composition consists of diaspore (68.3%), pyrite (17.95%), and illite (8.83%), accompanied by minor amounts of quartz, anatase, dolomite, as well as trace minerals such as chalcopyrite and cobaltite. Cobalt occurs in two distinct forms: approximately 55.21% is incorporated in pyrite via isomorphism (average Co content 163.38 g/t), while about 44.79% exists as discrete cobaltite minerals. The intergrowth between pyrite and diaspore is complex, and the extremely fine-grained cobaltite (2～4 μm), often encapsulated in chalcopyrite, presents significant challenges to its liberation, thereby constituting a key limiting factor for cobalt recovery. [Conclusion] This study reveals for the first time the dual occurrence state of associated cobalt in high-sulfur bauxite and its constraining mechanism during the separation process, offering new insights for the effective enrichment and comprehensive recovery of cobalt resources from this type of ore.
[Objective] To develop a new process for extracting yellow phosphorus from phosphate rock powder by silicon thermal reduction and study its non-isothermal kinetic behavior, [Method] the reduction rate, residual phosphorus content, mineral phase structure and morphology were analyzed by ICP-OES, XRD and SEM-EDS. The activation energy (Eα) and mechanism function G(α) were calculated by Coats-Redfern method and statava-stestak method. [Result] Silicothermic reaction of phosphate ore started at about 1 000 ℃. The reduction process can be divided into two stages: the initial stage involved a small portion of Ca5(PO4)3F in the ore powder reacting with SiO2 to form the intermediate product Ca3(PO4)2, which subsequently reacted with silicon, whereas the latter stage comprised the remaining Ca5(PO4)3F reacting directly with silicon. A large number of pores were formed due to the escape of the produced phosphorous gas, and the phase was identified as calcium silicate. [Conclusion] The phosphorus extraction reaction by the silicon thermal method is controlled by the Avrami-Erofeev nucleation and growth model. Increasing the heating rate can reduce the apparent activation energy. The reduction process occurs significantly above 1 000 ℃ and undergoes two reaction stages.
[Objective] To address the limitation of existing chemical analysis methods in evaluating the enrichment of valuable elements such as iron, nickel, and cobalt in oxidized and silicate minerals of laterite nickel ores, [Method] certified reference materials of lateritic nickel ores as research subjects and simulated a hydrometallurgical process were used. The tests focused on key factors, including the type and ratio of selective extractants, extraction temperature, and roasting pretreatment. The optimal extraction parameters were identified as follows: a mixed extractant composed of 1.5 mol/L hydrochloric acid and 1 mol/L ammonium fluoride, with extraction performed at 135 ℃ using 25 mL of extractant and no pre-roasting. [Result] The impact of the extractant on the matrix and the instrumental parameters for ICP-OES determination were investigated. Method validation results showed that the precision (RSD, n=12) was≤5.79%. The detection limits for MgO, CaO, total iron (TFe), cobalt (Co), nickel (Ni), alumina (Al2O3), manganese (Mn), and chromium (Cr) were≤0.007 7%, For limonite-type samples, the leaching rates of nickel and cobalt reached 99% and 91.67%, respectively. For serpentine-type samples, the leaching rates were 97.6% and 91.3%. [Conclusion] These values are consistent with the recovery rates of nickel and cobalt in industrial hydrometallurgical processes，indicating that this method is highly effective for analyzing and testing available metal elements in oxidized and silicate minerals of laterite nickel ores.
[Objective] To explore the enhancing effect of sodium hexametaphosphate as an inhibitor on the flotation performance of low-rank coal slime and its mechanism of strengthening flotation, [Method] The flotation experiment was conducted with low-rank coal slime as the research object and sodium hexametaphosphate as the inhibitor, and the influence of sodium hexametaphosphate dosage on the flotation indexes was investigated. The enhanced flotation mechanism was analyzed based on the contact angle test, Zeta potential test and EDLVO theory. [Result] When the dosage of sodium hexametaphosphate was 800 g/t, the flotation indexes of low-rank slime were relatively good, the cleaned coal yield, ash content, combustible recovery and flotation perfection index were 53.95%, 30.25%, 87.33% and 46.92%, respectively, the cleaned coal yield increased by 6.24 percentage points, the ash content increased by 6.24 percentage points, the combustible recovery increased by 17.01 percentage points, and the flotation perfection index increased by 15.14 percentage points. The contact angle of low-rank coal slime increased by 18.1°, and the Zeta potential values were significantly increased. [Conclusion] Sodium hexametaphosphate mainly acted on the mineral surface through electrostatic force to enhance the electrostatic repulsion between particles, reducing the cover of kaolinite and quartz on low-rank coal slime and making the flotation system more dispersed, and so as to obtain better flotation effect.
[Objective] In order to reveal the structural properties of hemimorphite from the microscopic atomic level, first-principles calculations based on density functional theory were carried out. [Method] The band structure, density of states, Mulliken population, surface energy of different structures and differential charge density of hemimorphite were systematically analyzed. [Result] The high-energy electrons near the Fermi level in hemimorphite crystal are mainly contributed by the 2p orbit of O, with the best chemical reactivity, and easily become the mineral surface action site during flotation. There is substantial electron enrichment around O in the hemimorphite ore lattice and increased charge density. The electrons are missing from the outside of Zn and transferred to O, and the Zn-O bond exhibits the characteristics of an ionic bond. The population value of the Zn-O bond Mulliken is low, and the surface energy of the (1 1 0) surface broken along the Zn-O bond is minimum, and the polar ore (1 1 0) surface is the most likely cleavage surface exposed. [Conclusion] The research results systematically reveal the crystal and surface structure characteristics of hemimorphite, which can provide useful reference and guidance for the study of hemimorphite flotation behavior and the development of flotation reagents.
