Waste copper slag is a typical hazardous solid waste containing a variety of valuable elements and has not been effectively disposed of so far. In this paper, a stepwise extraction process was proposed to recover valuable elements (copper, iron, lead and zinc) from waste copper slag. The specific procedures are as follows: (1) A flotation process was adopted to enrich copper, and when the copper grade in the flotation concentrate was 21.50%, the copper recovery rate was 77.78%. (2) The flotation tailings were pelletized with limestone, then the green pellets were reduced, and the magnetic separation process was carried out. When the iron and copper grades in the magnetic concentrate were 90.21% Fe and 0.4% Cu, 91.34% iron and 83.41% copper were recovered, respectively. (3) Non-magnetic tailings were mixed with clinker and standard sand to produce common Portland cement. Several products were obtained from the waste copper slag through the proposed process: flotation concentrate, measured 21.50% Cu; magnetic concentrate, containing 90.21% TFe and 0.4% Cu; direct reduction dust, including 65.17% ZnO and 2.66% PbO; common Portland cement for building construction. The comprehensive utilization method for waste copper slag achieved zero tailing and has great potential for practical application.

In this paper, an innovative method is proposed to upgrade iron and remove phosphorus from high-phosphorus oolitic hematite ore by the sodium magnetization roasting–magnetic separation–sulfuric acid and sodium hydroxide leaching process. The process parameters of sodium magnetization roasting, acid leaching, and alkaline leaching were optimized. The results show that by only adopting traditional magnetization roasting–magnetic separation, an iron ore concentrate containing 57.49% Fe and 1.4% P₂O₅ at an iron recovery rate of 87.5% and a dephosphorization rate of 34.27% was produced, indicating that it is difficult to effectively dephosphorize and upgrade iron by the conventional magnetization roasting–magnetic separation process. The obtained rough magnetic concentrates were then subjected to acid and alkaline leaching steps, and the final product, assayed at 64.11% iron and 0.097% P₂O₅, was manufactured successfully. Moreover, the added NaOH could promote the mineral phase reconstruction of aluminum- and silica-bearing minerals during magnetization roasting and intensify the upgrading of iron as well as enhance the growth of iron grains.

Recovery of valuable metals from red mud smelting separation slag is important for environmental protection and saving of natural resources. In this paper, we propose a recycling process of red mud smelting separation slag by mineral phase reconstruction conducted under an air atmosphere. In this process, NaOH and Ca(OH)₂ roasting of Al₂O₃ and NaAlSiO₄ was performed, and Al₂O₃ and SiO₂ were converted into alkaline-soluble NaAlO₂ and Ca₂SiO₄, respectively. In the consequent steps, more than 80% of Al₂O₃ was selectively dissolved into a leaching solution using a NaOH solution under 95 °C, and the obtained NaAlO₂ solution can be used as a source for extracting alumina. Then, a 20 wt.% HCl solution was used to remove SiO₂ from the residue, obtaining a SiO₂-containing solution and a concentrated residue of undissolved TiO₂ and CaO. Finally, this mineral phase reconstruction process can enable a higher metal leaching rate, and this study provides a novel, clean, and sustainable method for recycling valuable metals from red mud smelting separation slag.