Xiao-yi Shen

Preparation and characterization of ultrafine zinc oxide powder by hydrothermal method

Abstract With Zinc acetate and sodium hydroxide as raw materials, while polyethylene glycol employed as dispersant agent, ultrafine zinc oxide powder was synthesized by hydrothermal method. Influence of NaOH concentration on morphology of ZnO powder was studied. The as-synthesized ZnO powder looked like flower cluster and consisted of microrods with hexagonal morphologies. The crystal structure and optical property of the as-prepared powder were also characterized using XRD, UV-visible absorption spectrum and photoluminescence spectrum. The results indicate that ZnO powder is of hexagonal wurtzite structure and well crystallized with high purity. There is a strong excitation absorption peak at 300 nm in UV-visible absorption spectrum and blue shift exists obviously. The optical property of ZnO powder is excellent.

Reaction condition optimization and kinetic investigation of roasting zinc oxide ore using (NH4)2SO4

An orthogonal test was used to optimize the reaction conditions of roasting zinc oxide ore using (NH4)2SO4. The optimized reaction conditions are defined as an (NH4)2SO4/zinc molar ratio of 1.4:1, a roasting temperature of 440°C, and a thermostatic time of 60 min. The molar ratio of (NH4)2SO4/zinc is the most predominant factor and the roasting temperature is the second significant factor that governs the zinc extraction. Thermogravimetric–differential thermal analysis was used for (NH4)2SO4 and zinc mixed in a molar ratio of 1.4:1 at the heating rates of 5, 10, 15, and 20 K·min−1. Two strong endothermic peaks indicate that the complex chemical reactions occur at approximately 290°C and 400°C. XRD analysis was employed to examine the transformations of mineral phases during roasting process. Kinetic parameters, including reaction apparent activation energy, reaction order, and frequency factor, were calculated by the Doyle–Ozawa and Kissinger methods. Corresponding to the two endothermic peaks, the kinetic equations were obtained.

Preparation of ammonium jarosite from clinker digestion solution of nickel oxide ore roasted using (NH4)2SO4

To obtain the appropriate conditions for eliminating Fe3+ from NiSO4 solution, the digestion solution of the clinker was used as raw material, which was obtained from roasting the nickel oxide ore with (NH4)2SO4. The ammonium jarosite was successfully synthesized from the solution with analytic grade NH4HCO3. The effects of reaction temperature, reaction time, end pH value of reaction on the removal rate of iron were investigated, and the effect of the initial concentration of Fe3+ was also discussed. All of those factors had significant effects on the removal rate of Fe3+, among which the reaction temperature was the most prominent. The appropriate reaction conditions were concluded as follows: reaction temperature 95 °C, reaction time 3.5 h, end pH value of reaction 2.5 at initial concentration of Fe3+ 19.36 g/L. The physical aspect of (NH4)2Fe6(SO4)4(OH)12 was cluster figure composed of sheet or prismatic particles with smooth surface.

Preparation of ultrafine silica from potash feldspar using sodium carbonate roasting technology

A novel process was developed for the preparation of ultrafine silica from potash feldspar. In the first step, potash feldspar was roasted with Na2CO3 and was followed by leaching using NaOH solution to increase the levels of potassium, sodium, and aluminum in the solid residue. The leaching solution was then carbonated to yield ultrafine silica. The optimized reaction conditions in the roasting process were as follows: an Na2CO3-to-potash feldspar molar ratio of 1.1, a reaction temperature of 875°C, and a reaction time of 1.5 h. Under these conditions, the extraction rate of SiO2 was 98.13%. The optimized carbonation conditions included a final solution pH value of 9.0, a temperature of 40°C, a CO2 flow rate of 6 mL/min, a stirring intensity of 600 r/min, and an ethanol-to-water volume ratio of 1:9. The precipitation rate and granularity of the SiO2 particles were 99.63% and 200 nm, respectively. We confirmed the quality of the obtained ultrafine silica by comparing the recorded indexes with those specified in Chinese National Standard GB 25576―2010.