Advanced Materials Research Vols. 634-638

Abstract: Recycling of the shell of investment casting is meaningful. However，there are many factors which hamper the progress of this work, and one of these is that the Fe content is difficult to reach the standard under the present technological conditions. Through investigating and analyzing the sources of Fe in three factories which produce steel casting and a factory which is engaging in recycling of the shell of investment casting, a new idea which suggested to remove iron through controlling import of Fe form sources was put forward in this paper. To realize this idea, corresponding measures was suggested, such as classifying the shell, picking iron out manually, storing the shell appropriately, and selecting reasonable equipment for recycling processing.

Abstract: Stainless steelmaking dust contains significant levels of Cr-bearing phases (typically 0.28~16.5%). In this study, stainless steel was produced in an induction furnace, dust generated during the smelting process is collected in order to classify dust formation mechanisms and effects of operation parameters of smelting process on the formation of Cr(VI) species in the dust. The results showed that approximately 60% of dust generated during stainless steelmaking process by induction furnace is due to entrainment of charge fines, about 30% of dust formed due to metal and slag splashing result in oxygen and argon injection, and only about 10% of dust are formed through vaporization from the melt bath. In addition, the Cr-bearing phases in the dust mainly generate due to slag and metal splash. It can increase Cr(VI) content in the dust by increasing the chromium content in the molten steel, the amount of slag former and temperature of molten. To accelerate the cooling rate during the sampling period will decrease the Cr(VI) content in the dust.

Abstract: In this paper, the removal of aluminum in leach liquor of nitric acid pressure leaching laterite was investigated, and a new method of aluminum removal by precipitation with calcium sulphide was presented. The effect of reaction temperature, pH value before ageing and ageing time on the removal of aluminum were examined in details. The optimum conditions were determined as follows: reaction temperature 40 °C, pH 3.9~4.1 (before aging) and aging time 30 min. Compared with the traditional precipitation method, the loss of nickel and cobalt was less than 1% in the obtained aluminum precipitate slag, which is 3% lower than that by the traditional method; the filtration rate of aluminum precipitate slurry was faster than the traditional method, when the filtration press was controlled at -0.04 MPa, the filtration rate of aluminum precipitate slurry could reach 0.109 m3/(h•m2), which is 6.5 times higher than that obtained by the traditional method.

Abstract: A ferruginous nickel laterite was leached by sulfuric acid at atmospheric pressure. Nickel extraction was largely dependent on sulfuric acid concentration and leaching temperature. Besides these two factors, leaching time and liquid/solid ratio also influenced cobalt extraction significantly. Nickel was easier to be extracted than cobalt. About 95% nickel and cobalt could be extracted when leaching with 5mol/L sulfuric acid for 2h at 100°C, and the acid consumption was 1.417kg H2SO4/kg dry ore.

Abstract: A novel Cu metal complex [CuCl(C₁₂H₈N₂)₂]Cl _0.5(H₂O)_5.5 has been synthesized from a solution reaction and the crystal structure has been determined by means of single-crystal X-ray diffraction. [CuCl(C₁₂H₈N₂)₂]Cl _0.5(H₂O)_5.5, Monoclinic, C2/c. a=23.086(2)Å, b =30.090(3)Å, c=7.4580(8)Å, α=γ=90, β=97.67, V=5134.3ų, Z=8, R1 =0.0923, wR2 =0.2182, T=298K. The crystal packing is stabilized by O-H...O and O-H...Cl hydrogen bonding and Л-Л interactions.

Abstract: Commercial aluminum ingot with the diameters of 100 mm is produced by conventional out-phase electromagnetic field HDC casting process. The out-phase electromagnetic field is applied on the HDC casting process. The effect of out-phase electromagnetic filed on the ingot surface and structure is investigated. The result shows that the out-phase electromagnetic field is more effective in improving the upper surface, while, has little function on the bottom surface. The macro/microstructure of the ingot is changed by the out-phase electromagnetic field. Very long and coarse columnar grains evolve to short and thin columnar grains with the application of the out-phase electromagnetic field.

Abstract: Sulfuric Acid precure Pressure-atmospheriation leaching process from tin dust was studied. The factors had been investigated,which effects indium leaching rate,the factors are :the sulfuric acid initial temperature, curing time of heat, acid dosage, leaching reaction time, leaching temperature, the liquid-solid ratio and so on.The results show that the indium, zinc and tin leaching rate can be 96.68%, 97.70% and 0.52%,while pressure-atmospheriation leaching is carried out under the initial temperature 140°C,sulfuric acid, the time of heat aging 40 min, acid dosage and tin of tobacco smoke mass ratio0.7:1, leaching time 1.5h, leaching temperature 90°C,and the liquid-solid ratio 4:1 conditions.

Abstract: Under the premise of comprehensive recycling valuable metals, a novel technology was developed to extract vanadium from spent Al₂O₃-based catalyst. Mixture of spent catalyst and sodium carbonate was roasted at 1000°C for 30 min with the mol ratio of Na₂O to (Al₂O₃ + V₂O₅ + MoO₃) as 1.15, after water leaching, 97.3% of vanadium could be extracted. With CaO addition of 25 g/L and reacting at 90°C for 4 h, 98.6% of vanadium in sodium aluminate solution was precipitated as desilication residue. The desilication residue was leached at 80°C for 45 min with sodium bicarbonate concentration of 100 g/L and L/S of 4 mL/g, over 96.4% of vanadium could be leached. By two purification steps with addition of 30 wt.% H₂SO₄ and Mg(NO₃)₂, respectively, over 99% of Al, 96% of Si, 93% of P and 95% of As were removed from leach liquor. Adding 50 g/L NH₄NO₃ to the purified leach liquor and adjusting pH to 8.2, 99.8% of vanadium could be precipitated as ammonium metavanadate. After calcination, the purity of V₂O₅ product was 98.25%. In the whole process, up to 88.7% of vanadium could be recovered from the spent catalyst.

Abstract: Based on X-ray phase analysis and exploratory experiments, a novel process was proposed to recycle multiple valuable metals like Al, V, Mo, Ni and Co from spent Al₂O₃-based catalyst. The spent catalyst was roasted by adding sodium carbonate with certain mol ratio, after water leaching, Al, V and Mo could be extracted into leach liquor, whereas Ni and Co were enriched in the leaching residue. V and Mo were precipitated in step from leach liquor by adding CaO and BaAl2O4, respectively. After removal of V and Mo, Al(OH)₃ was prepared from sodium aluminate solution with carbonation decomposition process, and the purity of Al₂O₃ is 99.98%. With sodium bicarbonate leaching-purification-precipitation-calcination process, V₂O₅ could be prepared from V-bearing residue. Ni and Co were leached from water leaching residue with sulfuric acid. Recoveries of Al, V, Mo, Ni and Co from spent catalyst are 87.0%, 88.7%, 92.1%, 97.8% and 98.6%, respectively.

Abstract: Iodine-iodide leaching gold ore is a promising method alternative to cyanide leaching. In this paper, Eh—pH diagram of Au-I--I2-H2O system was established through calculating the equilibrium potentials of the main chemical reactions based on the thermodynamic data of the actual iodide leaching of gold system. Gold ore leaching experiments in iodine-iodide system under different influence factors were carried out to verify the effectiveness of the Eh-pH diagram. The results indicated the diagram of Eh-pH can effectively guide the actual gold ore leaching in iodine-iodide system.