A large amount of carbon dust is generated in the process of aluminum smelting by molten salt electrolysis. The carbon dust is solid hazardous waste but contains a large quantity of recyclable components such as carbon and fluoride. How to recycle carbon dust more effectively is a challenge in the aluminum electrolysis field. In this study, X-ray diffraction, scanning electron microscope, and other methods were used to analyze the phase composition of electrolytic aluminum carbon dust. The effects of particle size distribution of carbon dust, impeller speed, reagent addition, mixing time, and flotation time on the flotation recovery of carbon dust were studied. The optimal flotation conditions were obtained and the flotation products were analyzed. The results show that the optimal particle size distribution is 70% of particles below 200 mesh, corresponding to a grinding time of 11 min. The optimum speed of the flotation machine was to be between 1600 and 1800 r/min with the best slurry concentration of 20–30% and 5 min mixing time, and the collector kerosene was suitable for adding in batches. Under the above conditions, the recovered carbon powder with a carbon content of 75.6% was obtained, and the carbon recovery rate was 86.9%.

A new method for the disposal of the spent refractory materials by adding them directly to electrolytic cells requires our better knowledge of the Na₃AlF₆–Al₂O₃–SiO₂ melt system. The development of computational materials science offers us a new way to avoid the limitation of the experiment under a strong corrosive environment at high temperatures. First-principles simulation is applied to study the structure information, electronic properties, and transport properties of the system. The study reveals that the main Si and Al ions in the melt are complex ion groups such as [SiF₂O₂]^2–, [SiFO₃]^3–, [SiF₃O₂]^3–, [AlF₂O₂]^3–, [AlF₃O]^2–, and [AlF₄O]^3–. Tangled structures like [SiAlO₃F₅]^4– also exist in the melt. The average coordination number of Al–F and Si–F is 3.21 and 2.45, respectively. O ions mainly act as bridge ions in the melt. The bonding ability of Al with O ions is stronger than that of Si with O ions. Moreover, the Al–O bond is mainly covalent, while the Al–F bond is basically ionic characters. The order of diffusion ability of ions from large to small is Na, F, Al, Si, and O. Addition of SiO₂ into the Na₃AlF₆–Al₂O₃ molten salt causes an increase of the viscosity and a decrease of ionic conductivity.

Aiming at the current lack of thermodynamic parameters related to the preparation of aluminum–silicon–iron alloys from spent refractory materials in aluminum electrolytic cells, the Miedema model was used to calculate the thermodynamic parameters of Al–Si, Al–Fe, and Si–Fe binary alloys. On this basis, the Toop model was combined to calculate the mixing enthalpy ΔH, excess entropy SE, excess Gibbs free energy GE, and component activity α of Al–Si–Fe ternary alloys. The results show that ΔH, SE, and GE of binary alloys are all negative values. The properties of the Al element and Si element are similar, and they are different from the Fe element. The ternary alloys also have negative values of ΔH, SE, and GE in the alloy composition range, and their values change obviously in the region where the content of Fe is high or low. The activity values of all components decrease dramatically along with the diminishing of the corresponding molar fractions, and the activity values of Al, Si, and Fe are smaller in the central portion of the triangle of ternary components. It indicates that there is a strong interaction between the three elements, which easily forms ternary intermetallic compounds.

Despite the dominance of the blast furnace ironmaking process, more attention is being paid to the new technologies with lower energy consumption and carbon dioxide emissions. A novel flash ironmaking technology using pulverized coals and iron concentrates as raw materials, which is different from flash ironmaking with the reductive gas as the reducing agent, is studied. In order to obtain the flow patterns, temperature, and gas composition distribution, as well as particle trajectories in the reaction shaft of the flash ironmaking furnace, the Euler–Lagrangian model with a custom user defined function (UDF) code is used to simulate the processes of the fluid flow, heat and mass transfer, and chemical reactions, including the combustion reaction of pulverized coals and reduction reaction of iron concentrates. The results indicate that the flow patterns, temperature, and gas composition distributions present symmetrical distribution characteristics. The central oxygen expands rapidly after entering the reaction shaft and its distribution is approximately bell-shaped. The temperature distribution in the reaction shaft is wing-shaped. The maximum temperature, 2615 K, is reached at 5 m below the roof of the reaction shaft. The O₂ is quickly consumed after entering the reaction shaft. At 6 m below the roof of the reaction shaft, the oxygen concentration becomes almost zero, with the CO concentration reaching the highest. The Fe₂O₃ and FeO in the iron concentrates are mostly reduced to Fe at 9 m below the roof of the reaction shaft, and more than 95 wt% iron particles could be obtained within 1.2–7.7 s.

The sustainable utilization of solid waste is crucial for environmental protection. This work investigates the fabrication of foamed ceramics from Cr slag and municipal solid waste incineration (MSWI) fly ash, focusing on the effects of three inhibitors—NH₂SO₃H, ZnO·TiO₂, and (NH₄)₂HPO₄—on material properties and Cr leaching behavior. Experimental analysis, chemical thermodynamic calculations, and material characterization were all employed. Results show that the prepared foamed ceramics meet the JG/T 511-2017 standard for building materials, exhibiting excellent physical properties but significant Cr leaching. Among the inhibitors, (NH₄)₂HPO₄ with a molar ratio of n(P)/n(Cr) = 1 shows the best performance, achieving a bulk density of 205 kg/m³, compressive strength of 0.850 MPa, Cr leaching concentration of 188 μg/L, and a 70.0% of Cr leaching inhibition rate. The improvement is attributed to the AlPO₄ formation that enhancing the strength, and Ca₂P₂O₇ that stabilizing Cr during sintering. This work provides a feasible method for the safe resource utilization of Cr-containing waste.

A homogeneous and high-purity titanium silicon carbon powder (Ti₃SiC₂) is synthesised, using titanium, silicon and carbon black powders as raw starting materials at low temperatures via an improved molten salt method. This work demonstrates that multiple molten salts are more beneficial in facilitating the synthesis of Ti₃SiC₂ powder. The effect of reaction temperature on the purity of the synthesis was investigated, and the amount of excess Si required to compensate for their evaporating losses was determined. The powders were characterised by Various instruments. SEM and TEM images show that the as-prepared Ti₃SiC₂ retained its homogeneous morphology, and is near-pure, 500-600 nm in size, and generally well-dispersed. We believe that TiC and TiSi₂ formed by the molten salt method at low temperatures is the dominant factor in the reduced synthesis temperature and good dispersion of the final Ti₃SiC₂ powder.