Shaojun Bai

Process Optimization and Reaction Mechanism of Removing Copper From an Fe-Rich Pyrite Cinder Using Chlorination Roasting

The aim is to remove copper from a pyrite cinder by optimzing the chlorination roasting process using response surface methodology (RSM) and the reaction mechanism of chlorination roasting based on thermodynamic calculation was discussed. A quadratic model was suggested by RSM to correlate the key parameters, namely, dosage of chlorinating agent, roasting temperature and roasting time to the copper volatilization ratio. The results indicate that the model is well consistent with the experimental data at a correlation coefficient (R2) of 0.95, and the dosage of chlorinating agent and roasting temperature both have significant effects on the copper volatilization ratio. However, a roasting temperature exceeding 1170 °C decreases the volatilization ratio. The optimum condtions for removing copper from the cinder were identified as chlorinating agent dosage at 5%, roasting temperature at 1155.10 °C and roasting time of 10 min; under such a condition, a copper volatilization ratio of 95.16% was achieved from the cinder. Thermodynamic calculation shows that SiO2 in the pellet plays a key role in the chlorine release from calcium chloride, and the chlorine release reactions cannot occur without it.

Microstructure Characteristic and Phase Evolution of Refractory Siderite Ore during Sodium-carbonate-added Catalyzing Carbothermic Reduction

Thermodynamic analysis of refractory siderite ore during carbothermic reduction was conducted. Micro-structure characteristics and phase transformation of siderite ore during sodium-carbonate-added catalyzing carbothermic reduction were investigated. X-ray diffraction (XRD), scanning electron microscopy and energy-dispersive analysis of X-rays were used to characterize the reduced samples. Results indicate that the solid reaction between FeO and SiO2 is inevitable during carbothermic reduction and the formation of fayalite is the main hindrance to the rapid reduction of siderite. The phase transformation of present siderite ore can be described as: siderite-magnetite-metallic iron, complying with the formation of abundant fayalite. Improving the reduction temperature (≤ 1050 °C) and duration is helpful for the formation and aggregation of metallic iron. The iron particle size in the reduced ore was below 20 μm, and fayalite was abundant in the absence of sodium carbonate. With 5% Na2CO3 addition, the iron particle size in the reduced ore was generally above 50 μm, and the diffraction intensity associated with metallic iron in the XRD pattern increased. The Na2 O formed from the dissociation of Na2 CO3 can catalyze the carbothermic reduction of the siderite. This catalytic activity may be mainly caused by an increase in the reducing reaction activity of FeO.

First-principle study on the surface atomic relaxation properties of sphalerite

The surface properties of sphalerite (ZnS) were theoretically investigated using first principle calculations based on the density functional theory (DFT). DFT results indicate that both the (110) and the (220) surfaces of sphalerite undergo surface atom relaxation after geometry optimization, which results in a considerable distortion of the surface region. In the normal direction, i.e., perpendicular to the surface, S atoms in the first surface layer move outward from the bulk (d1), whereas Zn atoms move toward the bulk (d2), forming an S-enriched surface. The values of these displacements are 0.003 nm for d1 and 0.021 nm for d2 on the (110) surface, and 0.002 nm for d1 and 0.011 nm for d2 on the (220) surface. Such a relaxation process is visually interpreted through the qualitative analysis of molecular mechanics. X-ray photoelectron spectroscopic (XPS) analysis provides the evidence for the S-enriched surface. A polysulphide (Sn2−) surface layer with a binding energy of 163.21 eV is formed on the surface of sphalerite after its grinding under ambient atmosphere. This S-enriched surface and the Sn2− surface layer have important influence on the flotation properties of sphalerite.

Separation of Phosphorus and Magnetic Mineral Fines from Siderite Reductive Ore by Applying Magnetic Flocculation

The characteristics of siderite reductive ore and the ultrafine grinding-magnetic flocculation separation (MFS) of this ore were investigated in the present work. The results indicated that the iron phase in the raw ore was predominantly metallic iron with an iron particle size below 30 μm, and the phosphorus compound was apatite. By applying MFS to siderite reductive ore containing 37.14% Fe and 0.52 P, a concentrate assaying 66.37% Fe and 0.19 P with 74.32% recovery was produced. The iron recovery increased by 5.77% compared with the results of the conventional magnetic separation. The high efficiency in phosphorus removal and iron recovery achieved by the MFS process may be attributed to the adequate liberation of iron particles and the increase in magnetic force on the iron mineral fines in the form of flocs in a magnetic field.

Beneficiation of micro-fine magnetic minerals from reductive iron ore with ultrafine grinding-magnetic flocculation separation

ABSTRACT Beneficiation of micro-fine magnetic minerals from reductive iron ore was investigated. Sample characteristics and main force analysis of magnetic floc were conducted. The results indicated that the iron phase in reductive iron ores was predominantly metallic iron (below 20 μm). By applying ultrafine grinding-magnetic flocculation separation (MFS) to the raw ore (29.85% Fe), a concentrate assaying 74.12% Fe with 81.45% iron recovery was obtained. The iron recovery increased by 6.68% compared with the conventional magnetic separation (CMS). The high efficiency in beneficiation may be attributed to an increase in magnetic force on the micro-fine iron minerals in the form of flocs.

Effect of Ethylenediamine on Smithsonite Flotation

Smithsonite, a typical zinc oxide mineral, has been developed for many years as an alternative source. However, restricted to inferior ability of floating, zinc oxide is one well-known refractory mineral with poor selectivity and high regent consumption. In this paper, ethylenediamine (NH2CH2CH2NH2) was selected to active flotation of smithsonite using dodecylamine as collector. The effect of ethylenediamine on flotation efficiency was conducted; the results showed that without addition of ethylenediamine, the recovery of smithsonite was only 32.85% when the usage of dodecylamine-hydrochloride as collector was 5 × 10−4 mol/L. The optimum dosage of ethylenediamine was 6 × 10−3 mol/L and flotation recovery could be obviously improved to 92% under the same usage of collector. This finding may promote the recovery of refractory zinc oxide mineral resource in future.