In this study, the influence of steel slag (SS) content on the strength of the cementitious materials was investigated. The quaternary active cementitious material (CaO-SiO₂-Al₂O₃-SO₃) was prepared using various proportions of steel slag (SS), granulated blast furnace slag (BFS), and desulfurized gypsum (DG). The mechanism of synergistic excitation hydration of the cementitious materials was examined using various techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectrometry (FTIR). The strength of the mortar test block was initially increased and decreased later with the increase of the SS content. Mortar test block with 20% steel slag, 65% granulated blast furnace slag, and 15% desulfurized gypsum with 0.35 water-binder ratio showed the highest compressive strength of 57.3 MPa on 28 days. The free calcium oxide (f-CaO) in the SS reacted with water and produced calcium hydroxide (Ca(OH)₂) which created an alkaline environment. Under the alkaline environment, the alkali-activated reaction occurred with BFS. In the early stage of hydration reaction, calcium silicate hydrate (C-S-H) gel and fibrous hydration product ettringite (AFt) crystals were formed, which provided early strength to the cementitious materials. As the hydration reaction progressed, the interlocked growth of C-S-H gel and AFt crystals continued and promoted the increase of the strength of the cementitious system.

Beneficiation of ultrafine mineral particles (typically with an average size less than 20 µm) remains a critical problem for the mineral processing industry. Selective flocculation technique has been found to show great potential to tackle this problem, whose success mainly depends on the selective adsorption of a flocculant on the target mineral particles. In this work, a novel copolymer flocculant was synthesized by grafting starch and acrylamide, which for the first time, was employed in the flocculation separation of fine hematite from quartz. The composites of the grafted copolymer flocculant (GCF) were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The single mineral flocculation results showed that at the pH of 10–11 and GCF concentration of 125 mg/L, hematite flocs with a compact texture were formed, whose average diameter and fractal dimension reached 36 µm and 2.02, respectively; while quartz flocs were barely observed, and the average diameter of particles stayed at approximately 20 µm. Furthermore, the selective flocculation separation was confirmed in the mixed mineral flocculation. From adsorption tests and zeta potential measurements, it is shown that GCF tended to adsorb more selectively and intensely on hematite surfaces compared with quartz. This study provides a valuable reference for the efficient recovery of fine hematite particles.

In this study, the zinc containing dust and sludge of iron and steel smelting was taken as the research object, and the new ionic liquid of choline-urea was prepared and synthesized as the leaching agent. The conventional and ultrasonic leaching of zinc were compared, and the influence of liquid-solid ratio, temperature, time, ultrasonic power and other conditions on the zinc leaching rate were analyzed. The leaching residue was characterized by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-ray diffraction (XRD), and the kinetic equations of ligand leaching based on ultrasonically enhanced metallurgical dust sludge were constructed. The results showed that the choline chloride-urea ionic liquid has a special solubilization ability for ZnO, and the leaching rate of Zn at temperature 60 °C, ultrasonic power 350 W, and leaching time 240 min reached more than 98%. Kinetic fitting of the ChCl-urea leaching process revealed that the ChCl-urea leaching process was in accordance with the nucleation contraction model under both conventional and ultrasonic conditions, and the leaching process was dominated by interfacial mass transfer and solid film layer diffusion control for the reactions, respectively. The activation energies were Ea₁ = 44.56 kJ/mol and Ea₂ = 23.06 kJ/mol.

The recovery of zinc from metallurgical dust sludge is a crucial component of using solid waste as a resource in the metallurgical process, and deep eutectic solvent–ultrasonic synergistic enhanced leaching is an efficient method of doing so with excellent economic effects. The leaching rate of zinc is used as the value of response in this study, along with the four process conditions of leaching temperature, leaching time, liquid–solid ratio, and ultrasonic power. By building a regression model, the relationship between the various parameter components is investigated, and a strategy for optimization is then chosen and confirmed. The findings indicate that, for the parameters of temperature 40 °C, ultrasonic power 90 W, liquid–solid ratio 7:1 g/L, stirring speed 250 rpm, and leaching duration 80 min, the prediction value of the regression model of the zinc leaching rate is 98.47%. The average zinc leaching rate obtained by the 3 parallel verification experiments was 98.49%; the deviation from the regression model’s predicted value was 0.02%. This demonstrated that the experimental results were consistent with those predicted by the regression model, the experimental results were reliable and trustworthy, and the optimization scheme was reasonable and accurate. Compared with the conventional leaching method (leaching rate: 91.61%), the method under ultrasound increased the zinc leaching rate by 6.88%.

In order to study the effect of temperature on the settling characteristics of overflow ultra-fine iron tailings, the settling velocity of overflow ultra-fine iron tailings at eight different temperatures at 10–80 °C was experimentally studied. The results show that, with the increase in slurry temperature, the flocculation settling velocity of overflow ultra-fine iron tailings increases first and then decreases. That is, when the temperature is less than 60 °C, the settling velocity of flocs increases with the increase in temperature. When the temperature is 60 °C, the settling velocity reaches the maximum 5.66 mm/s. When the temperature is more than 60 °C, the settling velocity of tailings flocs gradually decreases. In addition, with the increase in the test temperature, when the temperature is less than 60 °C, the particle size, fractal dimension, and density of tailings flocculant gradually increase, the gap of flocculant structure gradually decreases, and the floc structure becomes denser. When the temperature is higher than 60 °C, the particle size, fractal dimension, and density of flocs gradually decrease, and the gap between flocs is larger than that at 60 °C. On this basis, the temperature model of overflow ultra-fine iron tailings is established according to the analysis of particle settling process, and the settling model was optimized according to different settling areas. The mean absolute error between the optimized settling velocity and the actual velocity is 0.007, the root mean square error is 0.002, and the error is small. The theoretical calculation results are in good agreement with the experimental data, and the optimized flocculation settling model has an important role in promoting the theoretical study of the flocculation settling of such ultra-fine iron mineral particles, and can be used to guide the sedimentation and separation system to achieve good sedimentation treatment effect under the best working conditions as required.