Qiming Feng

Flotation Mechanism of Wolframite with Varied Components Fe/Mn

ABSTARCT Wolframite is a series of minerals belonging to the isomorphic (Fe, Mn)WO4 with varied Fe/Mn ratios, for which the floatability changes with its composition. In this work, the effects of composition on floatability were studied using micro flotation, collector adsorption tests, infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS). The results showed that with an increasing Fe/Mn ratio, the flotation recovery of wolframite increased when using benzohydroxamic acid (BHA) as collector, but decreased when sodium oleate (NaOl) was applied. The chemisorption differences of these collectors were observed on the surface of wolframite, i.e., adsorption of BHA is greater at the surface of high-Fe wolframite, while NaOl is more easily adsorbed on high-Mn wolframite. Moreover, XPS analysis indicates that a new ferric product was generated on the surface of wolframite in the presence of BHA. In contrast, a new manganese product was formed after the addition of NaOl. These results demonstrate that Fe is the adsorption site for BHA, while Mn is the site for NaOl.

Carbon-coated cobalt oxide porous spheres with improved kinetics and good structural stability for long-life lithium-ion batteries

Current anode materials for lithium-ion batteries (LIBs) mainly suffer from poor electronic conductivity and large volume expansion upon cycling. Improving kinetics and designing good morphology structural stability of electrode materials can effectively enhance the lithium storage performances of LIBs. In this study, we successfully synthesized hierarchical carbon-coated cobalt oxide (C@CoO) porous spheres with improved kinetics and good structural stability, which were investigated by ex situ electrochemical impedance spectrometry, scanning electron microscopy, and powder X-ray diffraction. We also optimized the preparation conditions of the C@CoO porous spheres. The C@CoO350 porous spheres exhibited good electrochemical performances including the high 2nd specific capacity of 811mAhg-1 at 0.1Ag-1 and good rate property of 450mAhg-1 at 4Ag-1. Furthermore, it demonstrated an excellent cyclic stability with a high capacities of 669mAhg-1 after 400 cycles at 0.5Ag-1. Results demonstrated that C@CoO350 porous spheres are promising LIBs anodes.

Utilization of pyrogallol in flotation separation of scheelite from calcite

Scheelite is a typical tungsten-containing mineral and usually co-exists with calcite in deposits. The flotation separation of scheelite from calcite is a hard work in mineral processing. In this p...

A novel technique for microcrystalline graphite beneficiation based on alkali-acid leaching process

ABSTRACT Purification of microcrystalline graphite concentrate with alkali-acid leaching process was studied in this paper. The influences of alkali leaching temperature, NaOH concentration, alkali leaching time, HCl consumption, liquid-solid ratio, and acid leaching times were investigated respectively. Final refined products with carbon content in the range of 90.88%–98.36% were prepared from flotation concentrate with carbon content of 84.27%. In addition, the volatile content in the end product was reduced from 2.7% to 1.17%. X-ray diffraction (XRD) and scanning electron microscope equipped with energy-dispersive X-ray spectroscopy (SEM-EDS) analysis revealed that the crystal structure and morphology of graphite had no obvious change when impurities composed of Si, Al, and O were almost completely removed. Alkali-acid leaching process could enhance the carbon content of microcrystalline graphite to a higher level than the traditional method of alkali roasting-acid leaching process.

Improved hemimorphite flotation using xanthate as a collector with S(II) and Pb(II) activation

The flotation of hemimorphite using the S(II)–Pb(II)–xanthate process, which includes sulfidization with sodium sulfide, activation by lead cations, and subsequent flotation with xanthate, was investigated. The flotation results indicated that hemimorphite floats when the S(II)–Pb(II)–xanthate process is used; a maximum recovery of approximately 90% was obtained. Zeta-potential, contact-angle, scanning electron microscopy–energy-dispersive spectrometry (SEM–EDS), and diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements were used to characterize the activation products on the hemimorphite surface and their subsequent interaction with sodium butyl xanthate (SBX). The results showed that a ZnS coating formed on the hemimorphite surface after the sample was conditioned in an Na2S solution. However, the formation of a ZnS coating on the hemimorphite surface did not improve hemimorphite flotation. With the subsequent addition of lead cations, PbS species formed on the mineral surface. The formation of the PbS species on the surface of hemimorphite significantly increased the adsorption capacity of SBX, forming lead xanthate (referred to as chemical adsorption) and leading to a substantial improvement in hemimorphite flotation. Our results indicate that the addition of lead cations is a critical step in the successful flotation of hemimorphite using the sulfidization–lead ion activation–xanthate process.

Recovery Enhancement of Ultrafine Wolframite through Hydrophobic Flocs Magnetic Separation

ABSTRACT The recovery of ultrafine wolframite (<10 μm) by using flocs magnetic separation was investigated. Magnetic-separation results showed that recovery was closely correlated with the particle size of wolframite, where ultrafine particles were difficult to capture. Hydrophobic particles induced by octyl hydroxamic acid (OHA) could generate flocs, which enlarged the apparent size of particles. Furthermore, the recovery of ultrafine wolframite by flocs magnetic separation was higher than that by conventional magnetic separation. These findings indicated that the recovery was related to the increase in the magnetic force due to the particles’ size induced by hydrophobic flocculation.