Ning Peng

Recovery of iron from zinc leaching residue by selective reduction roasting with carbon

The recovery of iron from zinc leaching residue by selective reduction roasting with carbon was studied. The effects of roasting temperature, duration time and mass ratio of carbon to residue on decomposition of ZnFe(2)O(4), iron recovery and iron grade were investigated based on thermodynamic calculation and phase composition analysis of zinc leaching residue. 58.6% of iron grade in magnetic concentrate and 68.4% of iron recovery were achieved after the residue roasted at 750°C for 1h under carbon to residue mass ratio of 4%. The phase composition of roasted residue indicated that the ZnFe(2)O(4) decomposed in four stages: reduction of ZnFe(2)O(4) to ZnO and Fe(3)O(4), reduction of Fe(3)O(4) to FeO, formation of Fe(0.85-x)Zn(x)O and reduction of FeO to Fe. A technological process for simultaneously recovering iron and zinc from zinc leaching residue is proposed.

Technological mineralogy and environmental activity of zinc leaching residue from zinc hydrometallurgical process

Abstract Chemical, physical, structural and morphological properties of zinc leaching residue were examined by the combination of various detection means such as AAS, XRF, XRD, Mossbauer spectrometry, SEM-EDS, TG-DSC, XPS and FTIR. The toxicity characteristic leaching procedure (TCLP) was used to investigate the environmental activity of zinc leaching residue for a short contact time. The phase composition analysis indicated that the zinc leaching residue mainly consists of super refined flocculent particles including zinc ferrite, sulfate and silicate. The physical structural analysis showed that it has a thermal instability and strong water absorption properties. The results of TCLP indicated that the amounts of Zn and Cd in the leaching solution exceed 40 and 90 times of limit, respectively, which demonstrate that this residue is unstable in weak acidic environment for a short contact time.

Selective reduction process of zinc ferrite and its application in treatment of zinc leaching residues

Abstract The traditional zinc hydro-metallurgy generates a large amount of zinc ferrite residue rich in valuable metals. The separation of iron is crucial for resource recycling of valuable metals in zinc ferrite residue. A novel selective reduction roasting–leaching process was proposed to separate zinc and iron from zinc leaching residue which contains zinc ferrite. The thermodynamic analysis was employed to determine the predominant range of Fe 3 O 4 and ZnO during reduction roasting process of zinc ferrite. Based on the result of thermodynamic calculation, we found that V (CO)/ V (CO+CO 2 ) ratio is a key factor determining the phase composition in the reduction roasting product of zinc ferrite. In the range of V (CO)/ V (CO+CO 2 ) ratio between 2.68% and 36.18%, zinc ferrite is preferentially decomposed into Fe 3 O 4 and ZnO. Based on thermogravimetric (TG) analysis, the optimal conditions for reduction roasting of zinc ferrite are determined as follows: temperature 700–750 °C, volume fraction of CO 6% and V (CO)/ V (CO+CO 2 ) ratio 30%. Based on the above results, zinc leaching residue rich in zinc ferrite was roasted and the roasted product was leached by acid solution. It is found that zinc extraction rate in zinc leaching residue reaches up to 70% and iron extraction rate is only 18.4%. The result indicates that zinc and iron can be effectively separated from zinc leaching residue.

Element distribution of high iron-bearing zinc calcine in high gradient magnetic field

High gradient magnetic separation was conducted in order to separate insoluble zinc ferrite from zinc calcine before acid leaching of hydrometallurgical process. Chemical composition and structural characterization of zinc calcine were studied via inductively coupled plasma (ICP), X-ray diffraction (XRD), Mossbauer spectra, scanning electron microscopy (SEM) and laser particle analysis (LPA). The parameters of magnetic separation which affect the distribution of zinc ferrite and undesired elements, such as calcium, sulfur and lead in magnetic concentrate were investigated. The results of high gradient magnetic separation indicate that more than 85% of zinc ferrite is distributed into magnetic concentrate from the zinc calcine under the magnetic induction of 0.70 T. In addition, about 60% of calcium and 40% of sulfur distribute in non magnetic phases of tailings during magnetic separation process. Most of lead distributes uniformly along the zinc calcine in superfine particle size.

Leaching kinetics modelling of reductively roasted zinc calcine

ABSTRACT The kinetics of the acid leaching of reductively roasted zinc calcine was studied on sample particles with a fine-grained sediment structure. This structure has a porous surface during acid leaching, and the leaching behaviours of roasted zinc calcines are complicated. The leaching of iron is controlled by reactions at the solid–liquid interface with an active energy of 51.40 kJ mol−1, the kinetics model is described by The extraction of zinc could be expressed as with an active energy of 10.01 kJ mol−1 and this process is controlled by diffusion through the porous structure. Temperature is a key factor for the iron extraction, while acidity particle size may play an important role in the leaching of zinc. It is concluded that the selective leaching of zinc is favoured at a high acidity above 90 g L−1 and a low temperature.

Reductive roasting and ammonia leaching of high iron-bearing zinc calcines

ABSTRACT The separation of iron and zinc is a considerable challenge in the zinc smelting processes. A reduction roasting-ammonia leaching process is proposed in this paper. In roasting experiments, the apparent active energy of the reductive roasting of zinc ferrite is 31-35kJmol−1, and the diffusion of the reactant is the rate-determining step. Zinc ferrite was well decomposed into ZnO and Fe3O4 in reductive roasting. However, byproducts including FeO and Fe0.85−xZn xO were also detected. To achieve a high zinc recovery and to avoid the leaching of FeO, ZnO was selectively extracted via ammonia leaching, while magnetite and ferrous oxide were left in residues and recovered through magnetic separation (MS). The optimal operations of the proposed process were 750°C for 45min under a CO concentration of 8% and a CO intensity of 20%, and leached at 30°C for 1 h with a solid/liquid ratio of 1:7 and a stir speed of 200 revmin−1. A total of 88.56% of the zinc was extracted, and just 1.2% of the iron was extracted. The recovery and grade of iron reached 86.46 and 46.5%, respectively, after MS. This reduction roasting-ammonia leaching process is a favourable option for efficient zinc recovery from high iron-bearing zinc ores.