Inclusion Removal Process of Homogeneous CuCr50 Alloy In-Situ Synthesized by Al-Mg Composite Strengthening Reduction Coupling Slagging.

To overcome the problem of Cr2O3 and Al2O3 inclusions in CuCr50 alloy prepared by aluminothermic reduction method, in this paper, a novel methodology for strengthening metal-slag separation through in situ slagging is proposed. CuCr50 alloys were prepared by metallothermic reduction using Al and Al-Mg as reducing agents, and the physical properties of the slag, such as viscosity, density, and surface tension, were adjusted by controlling the proportion of CaO in the slagging agent in the raw material to achieve good separation of the slag-metal. The results show that with the ratio of CaO increased, CaO and MgO were coupled to make slag, which combined with Cr2O3 and Al2O3 to form CaCr2O4, MgCr2O4, and CaAl4O7 in the slag, thus reducing the content of impurities in the alloy. When RCaO/(CaO + Al2O3 + MgO) = 20%, the Cr content ranged from 46.61% to 47.09%, the inclusions accounted for 1.60%, the Cr particle size was refined to 20 µm, the number of Cr spherical crystals accounted for 9.88%, the conductivity reached 14.96 MS/m, and the hardness reached 100.23 HB. After heat treatment, the Cr phase was refined in the alloy, the conductivity increased from 14.96 MS/m to 18.27 MS/m, and the hardness increased from 100.23 HB to 103.1 HB. This method is expected to provide an effective method for the preparation of CuCr50 contact materials.

Summary of research progress on separation and extraction of valuable metals from Bayer red mud.

Bayer red mud is a strong alkaline solid waste discharged during alumina production. Due to large emissions and strong alkalinity, red mud is now mostly dammed or buried, which not only occupies huge land but also contaminates the surrounding ecosystem, causing the risk of collapse and landslide. In addition to its overall utilization in building materials, agriculture, the environment, and the chemical industry, red mud also contains valuable metals such as sodium, aluminum, iron, titanium, and scandium and is considered to be an important secondary resource. In this paper, the physicochemical properties and hazards of red mud are first introduced, and then, the overall utilization of red mud is summarized. Then, the latest research progress on the separation and extraction of valuable metals from red mud is reviewed in detail and a new comprehensive utilization method is recommended and evaluated. This paper also provides suggestions for the future development direction of the comprehensive utilization technology of red mud.

A perspective of stepwise utilization of hazardous zinc plant purification residue based on selective alkaline leaching of zinc.

A new route for selective recovery of zinc from hazardous zinc plant purification residue was proposed by alkaline leaching process. The thermodynamic analysis revealed that by controlling solution pH in the range from 14.30 to 16.78 at 25 °C, basic zinc sulfate can be converted to ZnO22- instead of Zn(OH)2, while Cd will enter into alkaline leaching residue as a hydroxide. It is feasible to leach selectively Zn and to separate it with Cd by alkaline leaching, and the experimental results confirm that. Under the conditions of NaOH concentration of 3 mol/L, L/S of 20 ml/g, temperature of 40 °C, and time of 50 min, LR of Zn reached 96.14% while them of Pb and Cd were only 0.66% and 2.83% respectively. ZnO with hexagonal wurtzite structure and Cd(OH)2 were the main phases of leaching residue. They crystallized and adhered to the surface of leaching residue particles, which result in the loose and random particle morphology. The findings confirm that alkaline leaching is efficient in separation of Zn and Cd in ZPPR. In addition, nano-ZnO with flowerlike was synthesized with the zinc-rich leaching solution by precipitation method and the its photocatalytic property was similar to that of nano-ZnO purchased.