Yang Shenghai

Preparation of tetrapod-like ZnO whiskers from waste hot dipping zinc

Large and uniform tetrapod-like ZnO whiskers (T-ZnO) were prepared from waste hot dipping zinc by vapor oxidation and examined by means of X-ray diffraction and ICP-AES analysis and scanning electron microscope. The products are pure hexagonal wurtzite crystals with tetrapod shape and edge size of center body 5–6 µm and needle length of 100–130 µm. The size and shape of ZnO particles are fully controlled by the growth conditions and T-ZnO can be obtained only at 850–1000 °C and total gas flow rate ranging from 40 to 250 L · h−1 in which the size of the T-ZnO particles varies slightly with temperature. The process of the formation of T-ZnO is that T-ZnO may nucleate at the initial stage with a complete tetrapod shape and develop to the large size, but not the process of preferential growth of octahedral nuclei and subsequent growth of the needles. The experiment presents a new method to prepare T-ZnO economically by using the waste hot dipping zinc.

Concentrating Ge in zinc hydrometallurgical process with hot acid leaching-halotrichite method

In recovering Ge and Ag from the calcine and fume dusts mixture of Huidong Lead-zinc Mine, the flow sheet of hot acid leaching-halotrichite method mainly consists of neutral leaching, low-acid leaching, high acid leaching and jarosite precipitation. In the ten circulation periods, the technology flow sheet was carried out smoothly. The loss of Ge in halotrichite residue is less than 5.0%, when iron is precipitated by using ferric potassium alum instead of common Na or ammonium alum and the conditions are controlled at temperature about 95 °C for more than 3 h, pH values below 1. 5. Ge and Ag are concentrated in the high acid leached residue, and their contents are 0.032% and 0.162%, respectively, and the total recovery and direct recovery of zinc are 98.94% and 96.15%, respectively.

Thermodynamic Research of Leaching Copper Oxide Materials with Ammonia-ammonium Chloride-water Solution

Abstract The solubilities of copper hydroxide Cu(OH)2, copper oxide CuO, atacamite Cu(OH)1.5Cl0.5, malachite Cu2(OH)2CO3 and chessylite Cu3(OH)2(CO3)2 in an ammonia-ammonium chloride-water solution were calculated using an exponential computation method based on both mass balance and charge balance equations. The range of stability of each solid phase was also established. A group of experiments were designed to validate the veracity of the results of the thermodynamic calculation.

Effect of Bromide Ions on the Pitting Corrosion of Hafnium in Anhydrous t-Butanol and Acetonitrile

Pitting of Hf in Et4NBr t-butanol and acetonitrile (ACN) solutions was studied by means of cyclic voltammetry, potentiodynamic anodic polarization, galvanostatic, potentiostatic and impedance techniques. The potentiodynamic anodic polarization curves did not exhibit an active dissolution region near corrosion potential due to the presence of an oxide film on the electrode surface, which was followed by pitting corrosion resulting from the passivity breakdown by the aggressive attack of bromide (Br−) ion. The pitting potential (E pit) increased with increasing potential scanning rate but decreased with increasing temperature and Br− concentration. Cyclic voltammetry and galvanostatic measurements allowed the pitting potential (E pit) and the repassivation potential (E p) to be determined. Analysis of the potential/time transients revealed that the applied anodic current density had a significant influence on the values of E pit. On the other hand, the E p values were independent on the applied current density. The current/time transients indicated that the incubation time (t i) for passivity breakdown decreased slightly with increasing potential and solution temperature. The impedance spectra showed that the resistance of passive layer decreased with increasing potential.