Zhoulan Yin

Effect of grinding atmosphere on the leaching of mechanically activated pyrite and sphalerite

Abstract The effects of grinding atmosphere, such as highly pure nitrogen (99.999 vol.%) (abbreviated as nitrogen), less air, and air on the leaching of pyrite and sphalerite mechanically activated for 20 and 120 min, respectively, were investigated. The results indicate that the leaching recovery of mechanically activated pyrite varies with the grinding atmosphere, and increases in the sequence of nitrogen, air, and less air. In contrast, the leaching recovery of mechanically activated sphalerite is insensitive to the different grinding atmospheres. The structural changes of the sulfide minerals mechanically activated under different grinding atmospheres were investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction analysis (XRD) and X-ray diffraction laser particle size analysis. The results show that the XRD spectra and the specific granulometric surface area ( S G ) do not vary with the grinding atmosphere, neither do the S2p and Zn2p XPS spectra of mechanically activated sphalerite and Fe2p XPS spectra of mechanically activated pyrite. However, a change was observed in the S2p XPS spectra of pyrite mechanically activated under different grinding atmospheres. The lattice distortion, S G and the elemental sulfur contents of pyrite and sphalerite mechanically activated under nitrogen were also investigated using XRD, X-ray diffraction laser particle size analysis and a gravimetric method, respectively. The results indicate that the elemental sulfur content of mechanically activated pyrite rises significantly and the lattice distortion ratio ( e ) rises only slightly with increasing grinding time. In contrast, the elemental sulfur content of mechanically activated sphalerite remains constant at 0.5 mg/g while the lattice distortion ratio ( e ) increases rapidly with increasing grinding time. Therefore, the formation of lattice defects on the surface of mechanically activated pyrite, and the lattice distortion on the surface of mechanically activated sphalerite may be mainly responsible for the enhancement of the leaching process for the corresponding sulfide minerals.

Leaching kinetics of low-grade copper ore containing calcium-magnesium carbonate in ammonia-ammonium sulfate solution with persulfate

The leaching kinetics of copper from low-grade copper ore was investigated in ammonia-ammonium sulfate solution with sodium persulfate. The effect parameters of stirring speed, temperature, particle size, concentrations of ammonia, ammonium sulfate and sodium persulfate were determined. The results show that the leaching rate is nearly independent of agitation above 300 r/min and increases with the increase of temperature, concentrations of ammonia, ammonium sulfate and sodium persulfate. The EDS analysis and phase quantitative analysis of the residues indicate that bornite can be dissolved by persulfate oxidization. The leaching kinetics with activation energy of 22.91 kJ/mol was analyzed by using a new shrinking core model (SCM) in which both the interfacial transfer and diffusion across the product layer affect the leaching rate. A semi-empirical rate equation was obtained to describe the leaching process and the empirical reaction orders with respect to the concentrations of ammonia, ammonium sulfate and sodium persulfate are 0.5, 1.2 and 0.5, respectively.

Removal of impurities from copper electrolyte with adsorbent containing antimony

Abstract A new adsorbent was synthesized with antimony oxide and barium sulfate to be used in the purification of copper electrolyte. The adsorbent possesses not only the properties of common adsorbents, but also special merits of its own. It can adsorb antimony from copper electrolyte, which then becomes adsorbent itself after regeneration; so the more the use-times, the more the amount of the adsorbent. Under the conditions of fixed contents of Cu and H 2 SO 4 in copper electrolyte, the adsorbent can adsorb 90% of Bi, 80% of Sb, as well as parts of As. The paper presents the results of adsorbent synthesis, characterization, regeneration, and metal ion separation. The feasibility of utilizing this adsorbent for copper electrolyte purification has been examined.

Preparation, characterization and photo-catalytic behavior of WO3-TiO2 catalysts with oxygen vacancies

Abstract TiO 2 photocatalysts compounded with WO 3 were prepared via a modified hydrolysis process and the 2% WO 3 -TiO 2 catalysts with different oxygen vacancies were obtained by calcination at 873 K in H 2 atmosphere. The catalysts were identified using X-ray diffractometry (XRD), specific surface measurement (BET), electron paramagnetic resonance spectroscopy (EPR), UV-Vis diffusion refraction spectroscopy (DRS), and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of 2% WO 3 -TiO 2 with different oxygen vacancies was investigated employing splitting of water for O 2 evolution. The results indicate that appropriate oxygen vacancies can obviously improve the photocatalytic activity of 2% WO 3 -TiO 2 catalysts, and using Fe 3+ as an electron acceptor under UV irradiation in 12 h, the maximum rate for O 2 evolution is 667 µmol/(L·h).

Preparation and characterization of SnO2-Li4Ti5O12 composite by sol-gel technique

Abstract SnO 2 -Li 4 Ti 5 O 12 was prepared by sol-gel method using tin tetrachloride, lithium acetate, tetrabutylorthotitanate and aqueous ammonia as starting materials. The composite was characterized by thermogravimertric (TG) analysis and differential thermal analysis (DTA), X-ray diffractometry (XRD) and transmission electron microscopy (TEM) combined with electrochemical tests. The results show that SnO 2 -Li 4 Ti 5 O 12 composite derived by sol-gel technique is a nanocomposite with core-shell structure, and the amorphous Li 4 Ti 5 O 12 layer with 20–40 nm in thickness is coated on the surface of SnO 2 particles. Electrochemical tests show that SnO 2 -Li 4 Ti 5 O 12 composite delivers a reversible capacity of 688.7 mA·h/g at 0.1 C and 93.4% of that is retained after 60 cycles at 0.2 C . The amorphous Li 4 Ti 5 O 12 in composite can accommodate the volume change of SnO 2 electrode and prevent the small and active Sn particles from aggregating into larger and inactive Sn clusters during the cycling effectively, and enhance the cycling stability of SnO 2 electrode significantly.

Predominance diagrams for Zn(II)–NH3–Cl−−H2O system

Abstract The thermodynamics in zinc hydrometallurgical process was studied using a chemical equilibrium modeling code (GEMS) to predict the zinc solubility and construct the species distribution and predominance diagrams for the Zn(II)–NH3–H2O and Zn(II)–NH3–Cl−−H2O system. The zinc solubilities in ammoniacal solutions were also measured with equilibrium experiments, which agree well with the predicted values. The distribution and predominance diagrams show that ammine and hydroxyl ammine complexes are the main aqueous Zn species, Zn(NH3)42+ is predominant in weak alkaline solution for both Zn(II)–NH3–H2O and Zn(II)–NH3–Cl−−H2O systems. In Zn(II)–NH3–Cl−−H2O system, the ternary complexes containing ammonia and chloride increase the zinc solubility in neutral solution. There are three zinc compounds, Zn(OH)2, Zn(OH)1.6Cl0.4 and Zn(NH3)2Cl2, on which the zinc solubility depends, according to the total ammonia, chloride and zinc concentration. These thermodynamic diagrams show the effects of ammonia, chloride and zinc concentration on the zinc solubility, which can provide thermodynamic references for the zinc hydrometallurgy.

Structural and electrochemical characterization of Li1.2NixCoxMn0.8 − 2xO2 (x = 0.128, 0.16, and 0.2) as cathode materials for lithium-ion batteries

Li1.2NixCoxMn0.8 − 2xO2 (x = 0.128, 0.16, and 0.2) cathode materials have been synthesized by a simple carbonate precipitation method followed by high-temperature calcination. The effects of the transition metal content on the structure, physical property, and electrochemical performance of the samples have been investigated. As the manganese content increases, we observed not only a well-ordered layered structure and uniform morphology but also remarkable improvements in capacity and better cycling properties.

Synergistic extraction of zinc from ammoniacal solutions using β-diketone mixed with CYANEX923 or LIX84I

Abstracts The extraction behaviors of zinc from ammoniacal solutions were investigated using β-diketone (HA) and their mixtures with CYANEX923 or LIX84I. The effects of pH, total ammonia concentration, extractant concentration, anion species and temperature on zinc extraction were examined. The synergistic mechanism was discussed with regard to the structure of extractant and the extracted zinc complexes. It is found that the increase of total ammonia concentration and pH inhibits zinc extraction for all extraction systems due to the formation of zinc ammine complexes in aqueous phase. This effect of HA with CYANEX923 is evidently smaller than that of HA with LIX84I or HA alone system. Effect of anion species on the zinc extraction by HA with CYANEX923 can be neglected, but this effect of HA alone and the mixture of HA with LIX84I decreases in the order of (NH 4 ) 2 SO 4 > NH 4 NO 3 > NH 4 Cl.

Preparation of metal zinc from hemimorphite by vacuum carbothermic reduction with CaF2 as catalyst

Abstract Zn reduction was investigated by the vacuum carbothermic reduction of hemimorphite with or without CaF 2 as catalyst. Results indicate that CaF 2 can catalyze the carbothermic reduction of zinc silicate, decrease the reaction temperature and time. The lower the reaction temperature and the more the amount of CaF 2 , the better the catalytic effect. The optimal process condition is obtained as follows: the addition of about 10% CaF 2 , the reaction temperature of 1373 K, the molar ratio of C to Zn Total of 2.5, the pressure of system lower than 20 kPa, the reaction time of about 40 min. Under the optimal process condition, the zinc reduction rate is about 93% from hemimorphite.

Framework-solvent interactional mechanism and effect of NMP/DMF on solvothermal synthesis of [Zn4O(BDC)3]8

Abstract In order to explore the effect mechanism of solvent on the synthesis of the metal organic framework materials, the microscopic interaction between solvent and framework and the effects of N,N-dimethyl-formamide (DMF) or N-methyl- 2-pyrrolidone (NMP) on solvothermal synthesis of [Zn4O(BDC)3]8 were investigated through a combined DFT and experimental study. XRD and SEM showed that the absorbability of NMP in the pore of [Zn4O(BDC)3]8 was weaker than that of DMF. The thermal decomposition temperature of [Zn4O(BDC)3]8 synthesized in DMF was higher than that in NMP according to TG and FT-IR. In addition, the nitrogen sorption isotherms indicated that NMP improved gas sorption property of [Zn4O(BDC)3]8. The COSMO optimized calculations indicated that the total energy of Zn4O(BDC)3 in NMP was higher than that in DMF, and compared with non-solvent system, the charge of zinc atoms decreased and the charge value was the smallest in NMP. Furthermore, the interaction of DMF, NMP or DEF in [Zn4O(BDC)3]8 crystal model was calculated by DFT method. The results suggested that NMP should be easier to be removed from pore of materials than DMF from the point of view of energy state. It can be concluded that NMP was a favorable solvent to synthesize [Zn4O(BDC)3]8 and the microscopic mechanism was that the binding force between Zn4O(BDC)3 and NMP molecule was weaker than DMF.