Copper slag (CS) contains a high content of valuable iron, the stockpile of CS occupies a large amount of land and leads to a waste of secondary resources. This study proposed producing battery-grade FePO4 & sdot;2H2O from CS through selective leaching, synthesis, and purification. The combined acid leaching/evaporation method was used to leach out Fe and inhibit Si from fayalite selectively, and then FePO4 & sdot;2H2O was formed by adding Na2HPO4 & sdot;12H2O without extra pH adjustment. The purity of FePO4 & sdot;2H2O obtained by using a reactor heated for 5 h at 180 degrees C with an HCl concentration of 2.5 M was 99.47 %, and the impurities were all by the industry standard for battery-grade FePO4 & sdot;2H2O (HG/T 4701-2021). The LiFePO4/C material was further synthesized and tested for battery performance. Under the test current of 0.1C, the charging-specific capacity of the battery in the first week was 175.8 mAh/g, and the discharge-specific ability was 159.3 mAh/g, which was close to the theoretical specific capacity and effective. Life cycle assessment (LCA) indicated that for each 1 kg of iron phosphate produced, the carbon emission of this study was reduced by 4.71 kg CO2 eq compared with the traditional technology.

Copper smelting slag (CSS) are waste slag obtained from smelters after reusing sulphur smelting slag. This study explores the potential of CSS to serve as a resource in cement mortar construction. Specifically, the study investigates the use of mechanical and chemical methods to enhance the volcanic ash activity of CSS, enabling them to replace up to 30 % of the cement content in cement mortar. The modified CSS was analyzed in terms of particle size and (Toxicity Characteristic Leaching Procedure) TCLP testing, while cement mortar specimens were subjected to a battery of tests including compressive strength, Freeze-thaw experiment, TCLP testing and cement stability testing. The results showed that compared with the unmodified CSS material, the copper smelting slag cement material with CaCO3 3 meets the requirements of GB/T 1596-2017 on the standard compressive strength of OPC 42.5 grade, with a compressive strength of 38.88 MPa at 10 % CaCO3 3 admixture, among which the CSS cement material with 10 % CaCO3 3 is the best and meets the leaching toxicity standard. Moreover, the modified CSS reduced energy consumption by 7.15 %, CO2 2 emissions by 27.41 %, and cost by 19.84 %. XRD, FTIR and SEM analysis showed that the mechanical activation of CaCO3 3 doping more drastically damaged the crystal structure of CSS, and local lattice distortion occurred, which induced the transformation of CSS from crystalline phase to amorphous phase and destroyed the ordered structure of minerals, resulting in the volcanic ash activity increased. Overall, this study demonstrates that CSS can serve as a viable raw material in cement mortar samples, reducing environmental impact and achieving resourceful use of slag.

The recovery of metal from copper slag is of great significance to the resource utilization of copper slag and the sustainable development of copper smelting industry. Currently, hydrometallurgy is the traditional method used to recover mineral metals. However, as copper slag is a silicate mineral, the traditional acid-leaching process of metal results in the leaching of Si, resulting in the formation of silica gel. The silica gel can inhibit the recovery of metal while making metal difficult to separate from Si and causing filtration problems. This study proposed a two-stage method (evaporation + water washing) to selectively recover Fe and Zn from copper slag. Under the optimal conditions (evaporation: H2SO4 = 3 M; time = 60 min; temperature = 120celcius; and liquid-solid ratio = 4; water washing: liquid-solid ratio = 5), the leaching efficiency of Fe, Zn, and Si reached 99.94 %, 97.40 %, and 0.15 % respectively. The separation mechanism was determined through mineral characterization (XRD, SEM, HRTEM-EDS, SAED, AFM, etc.) and the application of DLVO theory. It was found that H+ destroyed the Fe2SiO4 structure in copper slag during the evaporation stage, which promoted the release of Fe and Zn, forming soluble sulfate crystals. Simultaneously, evaporation increased the ion concentration, reducing the repulsive force between colloids, resulting in the aggregation and precipitation of silica gel into stable amorphous silica. After washing, soluble sulfate is dissolved in water. The recovered Fe can be processed to get red iron oxide (96.32 % purity), the Zn-containing solution can be recycled for electrolytic Zn, and the residue can be used to prepare geopolymer (52.47 MPa, 28 days). The two-stage method for recovering metals from copper slag is highly efficient and provides valuable insights into resource utilization of metals and Si in silicon-containing solid wastes.

Chromite ore processing residue (COPR) and copper slag (CS) are industrial waste slags that cause environmental pollution and require effective treatment. This study proposes a new strategy for the co-treatment and resource utilization of COPR and CS. Under the optimal conditions (liquid-solid ratio of 9.99; H2SO4 concentration of 0.85 M; the CS/COPR mass ratio of 9.98%; temperature of 88.20 celcius; and duration of 60 min), the reduction efficiency of Cr(VI) reached 99.48%, and the total Cr leaching concentration of residue reached 1.35 mg/L, which was below the USEPA regulatory limit of 5 mg/L. In addition, the detoxicated slag containing 61.44 wt% Fe2O3 can be used as a raw material in the steel industry. Through kinetic, characterization, and DFT analyses, the effective remediation of Cr(VI) in COPR by CS is a combination of adsorption and reduction. The unreacted shrinkage nuclear reaction model under the control of the surface chemical reaction is the most suitable model to describe the process, and when the apparent activation energy is 63.90 kJ/mol, the apparent rate equation is: 1-(1-x)1/3= 1 & sdot;371x107[CS/COPR]2 & sdot;35004 [H2SO4]2 & sdot;3945 [L/S]1 & sdot;95338 exp(-63 & sdot;90/RT) This is an important study for waste-waste co-treatment and resource utilization of industrial waste.

With the shortage of high-quality raw materials and increasingly strict environmental regulations, the recovery of metals from copper slag and pyrolusite has become a research hotspot. A novel method for simultaneously extracting Mn and Fe from pyrolusite and copper slag has been proposed. Under the optimal conditions (Copper slag / Pyrolusite = 2, H2SO4 = 2 M, liquid—solid ratio = 10, T = 90 ℃, holding time = 60 min), the leaching efficiencies of Mn and Fe can reach 98.28 1-(1-×)^1/3=979.65[CS/Pyrolusite]^2.6072[H_4SO_4]^1.3143[L/S]^0.5649exp(-35.50/RT)

The comprehensive and harmless utilization of copper slag flotation tailing (CSFT) is the key to a waste-free and sustainable copper industry. Here, the mineralogy and molybdenum micro-dissemination in CSFT were quantified and characterized, and the feasibility of the comprehensive recovery of Mo, Cu and Fe resources from CSFT and hazardous elements fractionation behavior by magnetic separation was discussed. To investigate the occurrence and abundance of Mo in each phase, CSFT was classified into four types of phases, including magnetite/hematite (27.26%), silicate associations (43.37%), and metallic sulphides and oxides. Molybdenum distribution is closely related to magnetite/hematite-Fe and S. The magnetic separation results indicated that Mo and Cu were enhanced in magnetic products by 34–41 and 15–21%, respectively. Cleaner non-magnetic residues were found to decrease significantly by 37–44, 58–60, and 11–19% for Cu, As, and Cr, respectively. Mineral fractionation was observed instead of chemical changes during magnetic separation. Despite a weak separation effect on magnetic and non-magnetic phases due to their close bonds and fine-disseminated minerals, the Fe-silicate associations without magnetic phases were well separated into non-magnetic residues. The enrichment of Ca, Mg and separation of an iron-silicate component in non-magnetic residues enhanced the cementitious property and allowed the development of more pathways of reutilization.

The traditional chromite ore processing residue (COPR) detoxification process is carried out in strong acid or anoxic high-temperature condition, which not only has a high input cost but leading difficulties for resource utilization of treated COPR. This study first reported the efficient reduction of Cr(VI) and recovery of Fe from COPR by waste molasses-assisted hydrothermal treatment. Under optimal conditions (i.e., the Na2CO3 dosing of 0.5 mol/L, the molasses/COPR mass ratio of 10%, hydrothermal treatment at 140 degrees C for 150 min), the Cr(VI) reduction efficiency reached 99.96 +/- 0.01%, and the leaching toxicity of total Cr met the USEPA regulatory limit of 5 mg/L. Moreover, Fe was recycled in the form of magnetic magnesioferrite with Fe2O3 grade of 52.58 +/- 0.90%, which can be used as raw material in steel industry. The Cr(VI) reduction reaction conforms to a pseudo-first-order kinetic model, and the reaction rate constants increase with increasing temperature (120 similar to 160 degrees C). As a potential mechanism of the reaction, the Mg-Al hydrotalcite (LDHs) structure collapses in the presence of Na2CO3 during the hydrothermal treatment, and the embedded Cr(VI) is released, which is then reduced to Cr(OH)3 by reducing substances such as fructose, sucrose, and glucose in waste molasses. From the standpoint of a circular economy, this study may provide a potential strategy for minimizing resource input and waste/emission production by harmless disposal and resource utilization of COPR and waste molasses.(c) 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).