Shaoxian Song

Floc flotation of galena and sphalerite fines

The flotation of galena and sphalerite fines in the form of flocs, which is termed floc flotation, has been studied in the present work. The flocs formed through hydrophobic flocculation induced by potassium amyl xanthate (PAX) and kinetic energy input. The studies were performed on single minerals of -20 μm size by using micro-flotation and floc size measurements. Several parameters, including pH, PAX concentration, kerosene addition and stirring strength, have been investigated for their effects on the floc flotation. The results show that the floc flotation closely correlates with the size of flocs. At good operating conditions, the floc flotation of galena and sphalerite fines can reach floatability of 100%, in comparison to conventional flotation obtaining floatability of about 40%. It has been found that a small addition of kerosene greatly improved the floc flotation, saving a large amount of PAX. Also, the floc flotation was tested on the Rey de Plata ore of Guerrero of Mexico, in which some of the metallic (Pb, Zn, Ag, Au, Cu) sulfide minerals are finely disseminated. The beneficiation results have demonstrated that floc flotation not only reduces the losses of the valuable metals in tailing, but also greatly increases the separation efficiency at cleaner flotation steps, producing concentrates with much higher grade and recovery in comparison to conventional flotation. The former effect might be due to the increase in recovery of the valuable minerals fines, and the latter might be attributed to the increase of the flotation rate of valuable mineral, because of floc formation and kerosene addition.

Magnetic separation of hematite and limonite fines as hydrophobic flocs from iron ores

Magnetic separation of weakly magnetic iron mineral fines in the form of flocs, which is termed Floc Magnetic Separation (FMS) process, has been studied in the present work, in order to find a substitution for high-intensity or high-gradient magnetic separators to treat the ores with weakly magnetic iron minerals in the fine size range. This study was performed on a hematite ore and a limonite ore that were finely ground to be micron particles, through the hydrophobic flocculation induced by sodium oleate and kerosene to make flocs. The experimental results have shown that the FMS process is effective to recover hematite and limonite fines at a middle magnetic field intensity, greatly increased the separation efficiency, compared with the conventional magnetic separation at the same conditions. By applying the process to the fine hematite ore containing 30.5% Fe, a concentrate assaying 64% Fe with 82% recovery has been produced. It has been found that the separation efficiency of the FMS process closely correlates with the main parameters of hydrophobic flocculation such as sodium oleate addition, conditioning time and kerosene addition. This finding suggests that the high efficiency achieved by the FMS process might be attributed to the considerable increase of the magnetic force on the iron mineral fines in the form of hydrophobic flocs in a magnetic field, thus the fines can be held by the separation plates in a magnetic separator and then be collected as magnetic concentrates.

Arsenic Removal from Water by Adsorption Using Iron Oxide Minerals as Adsorbents: A Review

This review highlights the adsorption process by using iron oxide minerals as the adsorbent for arsenic removal from water. It includes the characteristics of arsenic in water and its toxicities, the adsorption process for arsenic removal from contaminated water, iron oxide minerals as the adsorbent, arsenic adsorption capacity on iron oxide minerals, main factors of the adsorption, and arsenic removal from water by the adsorption process, as well as the mechanisms by which arsenic species adsorb on iron oxide minerals.

Selective flotation of bastnaesite from monazite in rare earth concentrates using potassium alum as depressant

Abstract Electrokinetic and flotation studies were carried out on single particles of bastnaesite and monazite to develop a flotation scheme for selectively removing monazite in the rare earth bulk concentrate from the Baiyunebo mine, in China (60.7% rare earth oxides or REO, 75% as bastnaesite and 25% as monazite). Low additions of potassium alum were found to efficiently depress monazite at pH 5 without affecting the flotability of bastnaesite with the collector benzoic acid. The bulk concentrate was treated through this scheme, and 85% of the bastnaesite was recovered in a concentrate that assayed 69.5% REO and contained 97% bastnaesite. The depressing effect of potassium alum appeared to be due to the preferential adsorption of hydrolyzed aluminum species on monazite in comparison to bastnaesite.

Effects of nonpolar oil on hydrophobic flocculation of hematite and rhodochrosite fines

It is shown that a small amount of kerosene addition greatly enhances the hydrophobic flocculation of hematite and rhodochrosite fines rendered hydrophobic by the adsorption of oleate ions. This effect is not only closely related to kerosene concentration, but also to the hydrophobicity of mineral particles. Using the tilting plate technique, the hydrophobic adhesion force of the mineral particles was determined, indicating that kerosene addition increases the force by about 280-fold as compared to that without kerosene, and that this force is an exponential function of the particle contact angle. Flocculation kinetics studies, along with hydrophobic adhesion force measurements, reveal that the positive effect of kerosene on hydrophobic flocculation is mainly due to an increase in the strength of flocs, and thus the flocs can support greater floc-rupture force field from turbulent flows.

A new collector for rare earth mineral flotation

A new collector for bastnaesite flotation - modified hydroxamic acid (MOHA) has been developed through several years laboratory research. The experimental results of flotation of pure bastnaesite mineral and rare earth ores, and the application experience in flotation plants showed that MOHA is an efficient collector for bastnaesite flotation. MOHA has stronger collector ability and higher selectivity compared to the other commonly used collectors. Through the measurements of zeta-potential, adsorption and infrared adsorption spectrum and in terms of the electronegativity theory of reagent groups, the flotation mechanism has been discussed. It was concluded that the adsorption of MOHA on bastnaesite surfaces is chemical adsorption in nature through three oxygen atoms in the polar group of MOHA chelating the surface Ce(III) of bastnaesite to form a pentagon-cycle chelate: OCNOCe(III)). Additionally, the chemisorption is accompanied with the multilayer and non-homogeneous physical adsorption of the MOHA molecules. The MOHA adsorption equation at the surfaces of bastnaesite can be expressed as: Γ = 6.76×10−2C11.02, while the adsorption rate constant k is: k = 2.64×105min−1mol−1m2.

Elimination of Cr(VI) from electroplating wastewater by electrodialysis following chemical precipitation

Abstract In this work, the elimination of Cr(VI) from an electroplating wastewater in China was studied by chemical precipitation (CP), electrodialysis (ED), and their combination. The experimental results show that CP was effective as a rougher treatment for removing Cr(VI) from a high Cr(VI) wastewater, but not for a deep Cr(VI) elimination. ED alone failed to achieve a deep Cr(VI) elimination from a high Cr(VI) wastewater, although it was very effective for a medium Cr(VI) wastewater. The mechanism might be attributed to the sedimentation of chromatic ions as polychromates in the pores of ED membranes because of high Cr(VI) concentration in wastewater, which may block the pores and thus stop the transportation of the ions through the pores. It was found that the combined chemical precipitation and electrodialysis (CP + ED) process is an effective and economic process to treat high Cr(VI) electroplating wastewater. This process allows treated water to be completely recycled to electroplating lines, fewer environmental concerns, and lower reagent and operation costs.

Hydrophobic Flocculation Flotation for Beneficiating Fine Coal and Minerals

ABSTRACT It is shown that hydrophobic flocculation flotation (HFF) is an effective process to treat finely ground ores and slimes so as to concentrate coal and mineral values at a fine size range. The process is based on first dispersing the fine particles suspension, followed by flocculation of fine mineral values or coal in the form of hydrophobic surfaces either induced by specifically adsorbed surfactants or from nature at the conditioning of the slurry with the shear field of sufficient magnitude. The flocculation is intensified by the addition of a small amount of nonpolar oil. Finely ground coals, ilmenite slimes, and gold finely disseminated in a slag have been treated by this process. Results are presented indicating that cleaned coal with low ash and sulfur remaining and high Btu recovery can be obtained, and the refractory ores of ilmenite slimes and fine gold-bearing slag can be reasonably concentrated, leading to better beneficiation results than other separation techniques. In addition, the ...

Effects of oxidation on the defect of reduced graphene oxides in graphene preparation.

The relationship between the defects of reduced graphene oxide (RGO) and the oxidation degree of graphite in the preparation of graphene with chemical conversion method has been studied in this work. This study was performed on an artificial graphite through the measurements of X ray diffraction, Raman spectroscopy and particle size analysis. The experimental results have shown that there indeed was a close relationship between the defects and the oxidation degree, which appeared in the form of S-type curve. Also, it was found that a low KMnO4 addition would lead to a partial oxidation of graphite, leaving defects mainly on the edges of RGO; with a high KMnO4 addition, the defects on RGO mostly appeared on the surfaces.

Adsorption of As(V) inside the pores of porous hematite in water.

As(V) adsorption inside the pores of porous hematite in water has been studied in this work. This study was performed on nonporous hematite and porous hematite prepared from the thermal decomposition of goethite and siderite through the measurements of adsorption isotherm, SEM-EDX, XRD and BET. The results demonstrated that the As(V) adsorption was difficult to be realized inside pores if they were too small. This observation might be due to that the pore entrances were blocked by the adsorbed ions and thus the inside surfaces became invalid for the adsorption. Only if the pore size is large enough, the effective surface area inside pores would be close to that on non-porous hematite for As(V) adsorption. In addition, it was found that siderite is better than goethite for preparing porous hematite with thermal decomposition as adsorbent for arsenic removal.