Improved Understanding of the Sulfidization Mechanism in Amine Flotation of Smithsonite: An XPS, AFM and UV–Vis DRS Study

Editorial on Special Issue “Surface Chemistry in Mineral Processing and Extractive Metallurgy”

“Mineral Processing” and “Extractive Metallurgy” are the key operations for the entire mining, metallurgy, and chemical industries [...]

Controlled dispersion of ZnO nanoparticles produced by basic precipitation in solvothermal processes

Zinc oxide nanoparticles were successfully synthesized under precipitation processes, using ZnSO4·7H2O as a Zn2+ precursor and K2CO3 used as a basic source, and hydrozincite was obtained as an intermediary, which was treated under two procedures; first procedure involved multiple stages to get final precipitated with NaOH, and in the second procedure the hydrozincite was straightforwardly dried at 220 °C. By both processes ZnO structures were obtained, which were turned into nanoparticles by a solvothermal treatment, for four hours in ethylene glycol at 200 °C. The final products for the first procedure was conglomerate of spherical nanoparticles with sizes ranged between 5-10 nm and dispersed ellipsoidal nanoparticles for the second procedure. Apart off the two procedures mentioned above, another synthesis was carried out with the same Zn2+ precursor but now using NaOH, and the solvothermal treatment produced ZnO mixed micro-structures which under ultrasonic cavitation disaggregated on mesoporous ZnO nanoplates of hexagonal shapes with nanopore sizes of approximately 0.35 nm. All ZnOs synthesized were structurally characterized with XRD, TEM and FT-IR techniques, and electronically with UV-Vis absorption and diffuse reflectance spectroscopies.

Reexamining the Role of Ammonium Ions in the Sulfidization, Xanthate-Flotation of Malachite

Ammonium ions have positive effects on the sulfidization flotation of malachite; however, the underlying mechanisms remain poorly understood. In the present work, micro-flotation tests, field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and solution analysis for ammonium nitrogen were carried out. The flotation results showed positive effects of ammonium on the sulfidization flotation of malachite. Macroscopically, the sulfidized malachite produced with ammonium exhibited a darker color than that without ammonium, whereas the opposite appeared to be true for their corresponding residual liquids. FESEM images highlighted the larger particle size and higher converge density of the sulfidization product when the presence of ammonium. Furthermore, XPS results indicated a higher sulfur concentration on malachite surfaces when the presence of ammonium. XRD results showed that Cu31S16 (djurleite) and Cu7S4 (anilite) comprised the sulfidization products, regardless of the presence or absence of ammonium. However, neither EDS nor XPS analysis showed nitrogen on malachite surfaces; moreover, the residual-ratio results for ammonium nitrogen clearly demonstrated that most ammonium continued to be held in solution before and after malachite sulfidization. Based on these findings, we inferred that ammonium ions may mediate the nucleation and growth of sulfidization product during malachite sulfidization, rendering larger sulfidization product particles. The larger size of sulfidization products may result in a darker, stabler and denser sulfidization product coating layer, and then may reduce the generation of colloidal copper sulfide in the residual liquids. Ultimately, ammonium facilitates better performance of sulfidization flotation of malachite.