查看更多>>摘要：The dependence of the efficiency of biobeneficiation (via bioleaching) of bulk copper-nickel sulfide concentrates on the ratio of copper to nickel sulfide minerals was studied. The copper content in the concentrates ranged from 10.8 to 19.1% (copper occurred in chalcopyrite), while the content of nickel was within 4.6-9.5% (nickel occurred in pentlandite and violarite). Although the copper content was higher than the content of nickel in all concentrates, the rate of nickel leaching significantly exceeded that of copper leaching. For the concentrates characterized by copper/nickel ratio (k) equal to 1.15 and 1.5, the average nickel leaching rate was >8 times higher than the copper leaching rate. Bioleaching of all studied concentrates allowed the obtainment of copper concentrates in solids (copper content of 15.6-18.7%) in which nickel content was low (0.27-1.49%). The high level of nickel dissolution and the maximum increase in the copper content in the solids were shown for the concentrate with the initial copper and nickel content of 10.9 and 7.2%, respectively (k of 1.5). In this bioleach residue, the copper content increased by 4.7%, while the nickel content decreased by 6.86% compared to the original concentrate. Thus, bioleaching of copper-nickel concentrates can be considered biobeneficiation, and the highest efficacy of the process may be achieved at a copper/nickel ratio of ~1.5.
查看更多>>摘要：Bio-based flotation reagents are of great interest considering their low-cost, abundance, and sustainability. This study evaluates the performance of saponified vegetable oils as collectors in phosphate ores' flotation. Olive, nigella, and flaxseed oils were elected for their fatty acid composition and their local availability. Prior to saponification, the oils' acidity index, saponification value, and fatty acids profile were determined. Surface chemical characterization, adsorption quantification and isotherms, zeta potential, and wettability assessments were conducted on bare and treated pure fluorapatite, calcite, and quartz. At low collector dosages, results revealed the chemical adsorption of the synthesized collectors on calcite and fluorapatite surfaces. With increasing dosages, the collectors' molecules precipitated at the calcium-bearing minerals' surface as calcium dicarboxylates salts then as micelles of fatty acids. Furthermore, flaxseed's soap exhibited higher adsorption densities and significant contact angle increases on the surface of calcite (8.20 mg/m(2) and +32.93) compared to fluorapatite (2.43 mg/m2 and +3.65). Moreover, collectors' adsorption on the surface of quartz was minimal. Accordingly, flaxseed's soap, served as an efficient calcite collector in phosphate flotation while including phosphoric acid for apatite depression. It enabled the recovery of up to 95.7% calcite at pH 12.
查看更多>>摘要：The efficient processing of base metal sulfide ores and sulfidic gold ores is sometimes compromised by the presence of carbonaceous material (CM). One common way of dealing with the CM problem is to pre-float the CM before the flotation of the sulfide minerals. Most CM exhibits some crypto crystalline graphitic structure. Although the graphite face surface has been studied extensively and is well described, the structural and surface properties of the graphite edge surface are more complex. In this study, the surface topography, graphitic structure, and functional features of the highly ordered pyrolytic graphite (HOPG) edge surface are reported to help provide a fundamental understanding of the behavior of CM in sulfide flotation separations. Surface structural defects, disordered atomic structure, and polar groups (C-O and C=O) were found from Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Raman, and X-ray Photoelectron Spectroscopy (XPS) analyses. The armchair and zigzag edge surfaces of graphite have been examined by ab-initio and Mo-lecular Dynamics (MD) simulation to describe the experimental results, including wetting characteristics based on contact angle measurements. Polar oxygen species, such as C-O-C and C=O bonds, were identified during oxidation of the graphite edge surfaces by ab-initio simulation of the surface reaction with oxygen molecules. MD simulations indicated complete wetting of the simulated oxidized graphite edge surfaces by water, whereas previous experimental contact angle measurements at the HOPG edge surface (40) revealed some hydrophobic character, which indicate the complex heterogenous nature of the edge surfaces.
NSTL
Elsevier