Pingmin Zhang

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.

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 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.

Preparation of Al(OH)3 by ion membrane electrolysis and precipitation of sodium aluminate solution with seeds

The preparation of Al(OH)3 by the ion exchange membrane electrolysis followed by the precipitation of sodium aluminate solution with seeds was made. During the process of ion membrane electrolysis, the sodium aluminate solution is rapidly acidified and the caustic ratio (aK) is decreased due to oxygen evolution in the anodic region. And the causticity of solution is increased due to hydrogen evolution in the cathode region, producing the high concentration of caustic soda solution. Regulating the acidity of the anodic solution by controlling the electric quantity in the electrolysis and subsequent decomposing the solution, Al(OH)3 could yield with very large rate and high efficiency. The experiments also indicate that the quality of aluminum hydroxide product is greatly affected by the impurity silicon.

Plotting and application of predominance area diagram of In–S–O system based on topological rules

The mathematical topological rule was applied to plot the predominance area diagram. Based on the analysis of the mutually conjugated, only two diagrams were the best topological embryonic graphs to build the predominance area diagram of Me-S-O system. Combined with topological rules and thermodynamic calculation, four relation-diagrams were denoted as α and β stable and unstable plane-topological diagrams, which were plotted for the Pb-S-O system and Zn-S-O system. The results show that β stable plane-topological diagram of Pb-S-O system and α stable one of Zn-S-O system are in accordance with the traditional predominance area diagram, which indicates that it is feasible to plot the predominance area diagram based on mathematical topological rules. Meanwhile, α unstable plane-topological diagram of Pb-S-O system can elucidate the phenomenon that metallic lead exists in higher oxygen and sulfur pressure area in modern bath smelting furnace. The mathematical topological rules broaden the application scope of the predominance area diagram and enrich the practice of its plotting.

Calorimetric study of the mechanochemically activated sphalerite

The thermal behavior of mechanochemically activated sphalerite during aging was investigated by calorimetry. The results indicate that mechanochemically activated sphalerite releases the stored energy which may origin from a series of complex transformations. The amount of energy released increases with the grinding time but remains almost constant after grinding for 1 h. It is independent of the grinding atmosphere and is related to the ball-mill medium. The XRD results illustrate a difference of the microstructure between activated and non-activated sphalerite. The microstructure of the activated sphalerite remains the same when it is heated in a calorimeter for the measurement of the heat released. The particle size analyses show that the particle size of the activated sphalerite increases when it is heated in the calorimeter. Therefore, it can be concluded that the released energy is probably caused by the decrease of the specific surface energy.

Standard enthalpy of formation of sodium paratungstate Na10H2W12O42.27H2O(s)

The standard enthalpy of decomposition of Na 10 H 2 W 12 O 42 .27H 2 O(s) at 298.15 K was measured using the method of three-step calorimetry in a Calvet twin-vessel microcalorimeter. The standard enthalpy of formation of Na 10 H 2 W 12 O 42 .27H 2 O(s) at 298.15 K was first obtained as -(21898.2±10.8) kJ mol -1 .