Dmitry Sukhomlinov

This study explores a sustainable approach for the recovery of metal values from copper slag using hydrogen (H₂). The high-temperature isothermal reduction experiments were carried out under a controlled H₂-Ar atmosphere and the subsequent molten slag extraction technique was employed. The elemental concentrations in both the metal/matte and the reduced slag were examined using inductively coupled plasma optical emission spectroscopy and electron probe microanalysis. It was found that the submerged H₂ blowing technique has a superior impact to top surface blowing on recovering metals from copper slag due to improved mass and heat transfer in the slag. Approximately 65 pct of copper of the initial 1.19 wt pct can be reduced into copper alloy after reduction by submerged H₂ blowing with the lowest concentration of 0.4 wt pct in slag. More than 90 pct of zinc and lead deported into the gas phase as metals. This research contributes to the ongoing efforts to enhance the sustainability of metallurgical processes and reduce their environmental footprint. Graphical Abstract

Antimony is one of the most deleterious impurity elements in copper smelting and has a strong tendency to vaporize in the smelting furnace resulting in an enrichment of antimony in smelter flue dusts. The vaporization and condensation behavior of antimony species was studied in dust-free conditions simulating the off-gas train of a Flash Smelting Furnace at temperatures below 1273 K (1000 °C). The influences of the oxygen partial pressure and the condensate formation temperature on the characteristics of the precipitated antimony species were determined. It was found that practically all the vaporized antimony species precipitated between 853 K and 546 K (580 °C and 273 °C) and that a higher oxygen partial pressure favored precipitation at higher temperatures. The formation of antimony sulfate, which thermodynamically is the most stable antimony species in the studied conditions at temperatures below approximately 723 K (450 °C), was found to be kinetically constrained and the vaporized antimony species precipitated as oxides or sulfides depending on the oxygen partial pressure and the precipitate formation temperature.

Large amounts of slag are generated during pyrometallurgical processing in copper production. Due to the presence of valuable elements, the improper disposal of huge quantities of copper slag produced, results in significant loss of resources as well as environmental issues. Analyses of the copper slag show that it contains valuable metals, particularly copper and nickel. In this work, four biochars were employed as fossil-free reducing agents to recover valuable metals from the slag. Reduction experiments were performed in a vertical furnace at temperatures 1250, 1300 and 1350 °C for 60 min in order to investigate the effect of temperature. Moreover, the effect of time on reduction progress was studied at 1250 °C and the concentrations of CO and CO₂ in the off-gas were measured with a gas analyzer. Copper slag was reacted with metallurgical coke for comparison and the products were analyzed with EPMA and LA-ICPMS. The results revealed that reduction rapidly progresses to the formation of metal alloy within 10 min. Valuable metals like copper, nickel and arsenic were the first to be reduced to the metal phase. As reduction time increased, iron was also reduced and combined with the metal droplet. The use of biochar as reductant was shown to be more effective than coke especially at lower temperatures. In addition, thermodynamic modelling was performed with FactSage and HSC and compared with the experimental results. The simulations with HSC showed the sequence of reactions taking place and the calculations by FactSage were in agreement with the experiments. Graphical Abstract

The Na ₂ O‐SiO ₂ ‐TiO ₂ system is important for the glass, ceramic, and metallurgical industries. Its features provide information on the composition and melting temperature to be utilized during the production of glass and ceramic and during the processing of TiO ₂ ‐bearing material in the metallurgical industry. The liquidus temperatures between 900 and 1600°C in the ternary system at saturation of solid SiO ₂ , TiO _2, Na ₂ Ti ₆ O ₁₃ , Na ₂ SiTiO ₅ , and Na ₂ Ti ₃ O ₇ were measured using the equilibration‐quenching energy‐dispersive X‐ray spectroscopy/Electron Probe Microanalyzer technique. A wide range of liquidus compositions were obtained with Na ₂ O between 0 and 41.7 mol% in the SiO ₂ ‐ and TiO ₂ ‐rich regions. The present study provides liquidus data at 1500 and 1600°C for the first time. Liquidus temperatures at various double saturations were also obtained in the present investigation to determine univariant lines in the phase diagram. The present experimental data were compared with previous investigations and computed phase diagrams. The data obtained in the present investigation can be employed to optimize the thermodynamic properties and phase diagrams of the Na ₂ O‐SiO ₂ ‐TiO ₂ system.

With the purpose of recovering the metal values, in this study the copper slag was reduced by coke and biochar at 1250 °C in an argon gas atmosphere using the isothermal reduction/drop quenching technique. The phase compositions of metal, matte, and slag were determined using electron probe microanalysis (EPMA). The effects of reduction time and amount of reductant were investigated. The distribution of elements between metal/matte and slag was ascertained based on the elemental concentrations determined by EPMA. It was found that copper concentration in slag can be effectively decreased to approximately 0.4–0.6 wt% within 5 min by coke and biochar. Copper and nickel can also be successfully recovered into the copper alloy phase once settling has been accomplished. Graphical Abstract

Phase equilibria in the CaO–SiO ₂ –CrO _x system were experimentally investigated at 1600°C and p O ₂ of 10 ⁻¹⁰ to 10 ⁻¹¹ atm using the high‐temperature isothermal equilibration/drop quenching/electron probe X‐ray microanalysis technique. The constrained isothermal sections of the CaO–SiO ₂ –CrO _x system were constructed at 1600°C and p O ₂ of 10 ⁻¹⁰ to 10 ⁻¹¹ atm based on the experimental results. The primary phase fields including cristobalite (SiO ₂ ), larnite (Ca ₂ SiO ₄ ), (Ca,Cr)Cr ₂ O ₄ , and corundum (Cr ₂ O ₃ ) were determined. Simulations by thermodynamic software MTDATA, FactSage, and Thermo‐Calc were compared with the present experimental results.

Arsenic is a common impurity element in sulfide concentrates. It tends to accumulate in the flue dust of smelting furnace due to the volatility and internal circulation of the flue dust practiced in the smelting-converting process chain. The only outlets for arsenic are anodes and discard slag. Arsenic condensation in dust-free conditions was studied below 800 °C where the gas atmosphere was controlled by SO₂-air-N₂ gas mixtures. Based on these experimental results, we confirm the kinetically constrained formation mechanism of the arsenic-containing dust, and its speciation into metallic, oxidic (III, V), and sulfidic species. The influences of temperature and atmosphere on the speciation of arsenic were compared with industrial data and discussed. Graphical Abstract Condensed arsenic‐bearing particles collected by electrophoretic forces on the surface of fused SiO₂ in SO₂‐O₂ atmospheres: the crystal morphology shows euhedrally facetted As₂O₃ crystals and initially molten As‐OS alloy droplets together with poorly crystallized AsS_x particles.