Weiheng Chen

Extraction of zinc from blast furnace dust in ammonia leaching system

Abstract In this research, the extraction of zinc from the blast furnace dust in the ammonia leaching system containing different leaching agents (NH3, (NH4)3AC, (NH4)2CO3, (NH4)2SO4, NH4Cl) was investigated. Meanwhile, the effects of different total ammonia concentrations, ammonia/ammonium ratios, solid-liquid ratios, stirring speeds, and leaching temperatures on the extraction of zinc were studied. The results showed that ammonium sulfate was particularly effective and the extraction efficiency of zinc is up to 86.48% under the following conditions: total ammonia concentration of 5.0 mol/l, ammonia/ammonium ratio of 1:1, solid-liquid ratio of 1:5, temperature of 45°C, leaching time of 60 min, and stirring speed of 350 rpm.

Effects of roasting pretreatment on zinc leaching from complicated zinc ores

Abstract Roasting pretreatment and ammonia leaching were performed to extract zinc from complicated zinc ores. The residue of the unroasted ore showed that the zinc containing phase ZnCO3 cannot be effectively leached in the ammonia leaching system. Mineral phase transformation of ZnCO3 takes place at a roasting temperature of 673 K, and this is the reason for the improvement of zinc leaching recovery. Additionally, the parameters that can influence the leaching rate of zinc such as the calcined temperature, the total ammonia concentration, the ratio of liquid to solid, the stirring speed and the leaching time were also investigated. Zinc leaching recovery from the complicated zinc ores could reach 84.7% under the following optimized experiment conditions: roasting temperature of 673 K, leaching temperature of 298 K, stirring speed of 500 rpm, total ammonia concentration of 6 mol/l, liquid to solid ratio of 11:1 and leaching time of 60 min. Compared to the zinc leaching recovery from unroasted ore (49.7%, ammonia concentration 6 mol/l), roasting pretreatment and optimization of process parameters can increase the zinc leaching recovery by 70.4%.

Impacts of ultrasound on leaching recovery of zinc from low grade zinc oxide ore

Abstract On the basis of an experiment on ultrasonic enhanced ammonia leaching of low grade zinc oxide ores, the effects of the total ammonia concentration, the ratio between the NH3 concentration (CNH3) and that of ammonium sulfate (NH4)2SO4 (C(NH4)2SO4), and the ultrasound power on zinc leaching rate were studied. The results showed that the leaching efficiency of zinc observably increased with the increase of the total ammonia concentration, and that the ratios between CNH3 and C(NH4)2SO4 can remarkably affect the zinc extraction from the low grade zinc oxide ores. When the ratio between CNH3 and C(NH4)2SO4 is 2 to 1, the leaching rates of zinc are observably improved. The ultrasound can improve the leaching efficiency of zinc, and its effect was especially pronounced when the NH3 concentrations were low. The higher ultrasound power cannot sensibly improve the leaching rate of zinc, but it can improve the leaching speed and shorten the leaching time. Under the optimized conditions - total ammonia concentration of 8 mol/l, ratio between CNH3 and C(NH4)2SO4 of 2 to 1, and ultrasound power of 600 W – 83.33% of zinc is recovered.

Alkaline leaching of zinc from low-grade oxide zinc ore using ammonium citrate as complexing agent

Abstract In this study, the effect of ammonium citrate (AC) on the leaching of low grade zinc oxide ore in the 5 m ammonia solution was studied. AC served as a leaching agent and complexing agent, respectively. The results of the leaching experiments showed that AC increased the leaching rate of zinc, which increased with the rise of the concentration of AC. Under conditions of temperature of 30°C, reaction time of 60 min, citric acid concentration of 1 mol/l and solid to liquid ratio of 1:5, 88.83% of zinc was leached. The enhancement mechanism of AC to the leaching rate of zinc was studied by Fourier transform infrared (FT-IR) spectra.

Ammonia Leaching of Zinc from Low-grade Oxide Zinc Ores Using the Enhancement of the Microwave Irradiation

Abstract Irradiated roast treatment and the ammonia leaching processing were conducted to deal with the low-grade oxide zinc ores. The ZnCO3 phase was hard to be attended, which was the reason for the low leaching rate of the complicated zinc ores. The mineral phase transformation of the ZnCO3 phase was generated after the ores irradiated in the microwave at the temperature of 673 K. The irradiated ores generated more small particles, it was the reason that the leaching rate of the complicated zinc ores was increased. When the leaching processing of the irradiated roasted ores was conducted under the conditions of the total ammonia concentration of 6 mol/L, the liquid to solid phase ratio of 11:1, the leaching temperature of 298 K, the leaching time of 150 min and the stirring speed of 400 rpm, 88.3 % of zinc could be achieved, which was the maximum leaching rate of the irradiated ores.

The Enhancing Effect of Microwave Irradiation and Ultrasonic Wave on the Recovery of Zinc Sulfide Ores

Abstract A novel process for the treatment of zinc sulfide ores is discussed in this paper, which consists of two procedures: microwave roasting pretreatment and synergistic chelation. What’s more, the reaction mechanism also has been studied. By comparing XRD patterns before and after roasting, it can be concluded that microwave truly alleviates the reaction energy, and adding Na2O2 avoids the emission of SO2. % recovery of zinc can reaches 72.47 % on conditions of adding Na2O2 25 %, microwave activating temperature 500 °C, holding time 10 min, leaching temperature 40 °C, ultrasonic wave power 1,800 W, leaching time 4.5 h and solid to liquid ratio 10:1 in ammonium chloride solution whose total ammonium concentrate is 7.5 mol/L (c(NH3)T=7.5 mol/L). The molar ratio of NH4Cl and NH3·H2O is 1:1 (c(NH4Cl): c(NH3·H2O)=1:1). The effect of ultrasonic wave power in this process is to shorten reaction time.

Effects of La and Mg on Microstructure and Mechanical Property of Al‐15Si Alloy

The effects of La on the microstructures and mechanical properties of Al‐15Si alloy were investigated, and the results showed that 0.3% La could availably modify the Al‐15Si alloy. The morphology of the eutectic Si obviously changed into the short flake and the dot shape, and the angle of primary Si was refined to bluntness with the contents of La increasing from 0.1 % to 0.3%. In addition, the effects of Mg on the microstructures and mechanical properties Al‐15Si‐0.3La alloy were studied. The optical micrographs showed that the eutectic Si were further refined to the shorter bar the dot shape, and the amount of primary Si reduced with the increase of Mg addition. The formation of Mg2Si strengthening phase improved the mechanical properties of the modified Al‐15Si‐0.3La alloy. Compared with Al‐15Si alloy, the tensile strength and the elongation of Al‐15Si‐0.3La‐2.0Mg alloy increased 41.4% and 40%, respectively.

Effects of Nd and Cu on Microstructure and Mechanical Properties of Hypereutectic Al‐20Si Alloy

In this paper, the modification of Nd to hypereutectic Al–20Si alloy was studied, and the effects of Cu on the microstructures and mechanical properties of the modified Al‐20Si alloy were investigated. The results showed that the primary Si transformed from irregular morphology to fine polyhedral morphology, and the morphology of eutectic Si transformed from acicular/ lamellar to short‐rod and point like after modification. Compared with Al‐20Si alloy, the tensile strength of Al‐20Si‐0.3Nd increased by 22.8%, and the elongation increased by 127.8%. The strengthening phase CuAl2 appeared in the Cu‐containing Al‐20Si‐0.3Nd alloy; as a result, the mechanical properties of Al‐20Si‐0.3Nd‐Cu alloy were improved. Compared with Al‐20Si alloy, the tensile strength of Al‐20Si‐0.3Nd‐2.0Cu alloy increases by 39.5%, and the elongation doesn’t decrease.

Research on Leaching of Zinc Sulfide Ores Through Synergistic Coordination

In this thesis, a new process of recovering zinc sulfide ores was developed. The novel synthetic coordination leaching process mainly included two steps: microwave assisted phase reconstruction and compound coordination leaching. By applying various techniques, such as chemical composition analysis, X-ray diffractometry (XRD) and Raman spectroscopy, it could be concluded that sulfide phases would directly oxidized to zinc oxides under the 500 °C microwave roasting and adding 30% Na2O2. What’s more, zinc leaching rate reached to 61.16% within 2 hours. Compared to the current technologies, this procedure had the advantage of avoiding SO2 emission, high leaching efficiency, simple process, manipulate easily, and low cost, which could be expected tremendous application potentials.