Publications

Red mud is a hazardous waste produced from Bayer process, and its high alkalinity caused by soluble sodium (Na) poses a major threat to environment. In this study, an environmental-friendly method was proposed for recovery of soluble sodium (Na) and harmless utilization of red mud. First, soluble sodium was selectively solidified into Na-rich phases (anorthite and melilite). Subsequently, high-purity Na-rich phases were efficiently recovered from red mud under super gravity. Finally, solidification mechanism of sodium in anorthite and melilite was confirmed by characterizing high-purity Na-rich crystals. The leaching rates of Na+ were only 0.01% and 0.04% in anorthite and melilite, respectively, and high alkalinity was minimized. In addition, the anorthite was found to possess a stronger solidification capacity of Na as compared with melilite based on the reaction mechanism of Na+ + Si4+= Ca2+ + Al3+. This provides a theoretical basis for alkalinity minimization and harmless utilization of red mud.

Perovskite phase was successfully separated from CaO-TiO2-SiO2-Al2O3-MgO melt by super gravity. Under the hypothesis that the titanium ex

Abstract Vanadium (V) and titanium (Ti) are widely used in high‐performance ceramics due to their excellent magnetic, electrical, and chemical properties. Vanadium slag from the smelting of vanadium–titanium magnetite contains large amounts of V and Ti, which are enriched into spinel in the form of mutual replacement. However, the lack of research on the crystallization mechanism of V and Ti limits their respective recovery. In this study, the crystallization of V and Ti in vanadium slag with temperature was investigated, where V was primarily crystallized into V‐spinel between 1773 and 1573 K, while Ti was mainly crystallized into Ti‐spinel between 1573 and 1373 K. Afterward, the enhanced separations of V‐spinel and Ti‐spinel were realized by controlling the cooling rate using super‐gravity in the corresponding temperature range, respectively. High‐purity crystals of V‐spinel with up to 42.68 wt.% V 2 O 3 and Ti‐spinel containing up to 32.87 wt.% TiO 2 was obtained. On this basis, the crystallization mechanism of V and Ti was revealed by crystal characterization, and the results showed that the crystallization of Ti lagged behind that of V due to the lower crystal stability of Ti‐spinel than that of V‐spinel. This study provides a theoretical basis and methodological guidance for the efficient utilization of vanadium slag.

The aim is exploring a new MgO heterogeneous deposition coating method to increase the coating amount, and investigating its sticking prevention effect on the fluidized bed reduction of iron ore. The pure Fe2O3 or iron ore particles were coated with Mg(OH)2 using the heterogeneous deposition coating method. In order to restrain the homogeneous nucleation and promote the heterogeneous nucleation during precipitation, the NH4Cl–NH3·H2O pH buffer solution was employed to adjust the OH− concentration. The actual MgO coating amount on the particle surface has been improved to 3.8 wt%, and the sticking problem of Hualian iron ore during fluidized reduction can be avoided with the MgO coating amount of 0.91 wt%. This coating method achieved a satisfactory uniformity of the coating film, and there was nearly no uncoated part on the coated particle surface. The combination strength between the coating layer and particles' surface with different coating methods was investigated via a blowing system, and it was concluded that the solution and heterogeneous deposition coating methods could achieve a higher coating strength than the dry or slurry coating methods.

Recently, the recovery and utilization of rare earth elements (REEs) from secondary resources have become increasingly important with the rapid consumption

Magnesium salt slag is generated during the refining of crude magnesium and usually contains a large amount of soluble chloride salts, which will cause serious environmental problems. In this study, a new method was proposed for sustainable recovery and reutilization of molten salt from magnesium salt slag via supergravity separation. The phase transformation of molten salt with temperature was studied. The molten salt was in a fully molten state at 800–750 °C, while the NaCl precipitated at 750–700 °C, meantime combined with MgCl2 and tightly encapsulated the fine MgO particles. Therefore, recovery of molten salt was conducted at 800 °C enhanced by supergravity separation, where the molten salt and MgO-rich particles were efficiently recovered within 5 min with high recovery rates of 98.9 % and 99.5 %, respectively. Moreover, the recovered molten salt removed 98.6 % of oxide inclusions in the crude magnesium refining process. Meanwhile, the fine MgO-rich particles with w(MgO)=76.3 % and 1–10 µm was recovered from the magnesium salt slag, where the leaching amount of Cl- was decreased to 0.586 g/L, which was below the Chinese standard for chlorine ion content in solid wastes. Therefore, this manuscript provided a novel process for recovering molten salt from magnesium salt slag without additives and secondary pollution, meanwhile reducing the generation of solid waste and hazards.

The stickiness of bed material was highly relevant to agglomeration/defluidization in fluidized-bed reduction of iron ore. In this paper, a quantitative model was developed to associate solid surface viscosity (particle adhesion) of a granular group with particle size distribution (PSD) function. The calculation was focused on the sintering behavior of particles with different sizes. This model explained theoretically the dependence of particle adhesion on PSD parameters and thus can be used as a reference to select the particle composition of bed materials for fluidization reduction of iron ore.

Bayan Obo tailings is unique polymetallic resource associated with iron, niobium (Nb) and rare earths (REEs). However, conventional extraction processes are not economically viable for Nb and REEs due to their low-grade nature. To overcome this challenge, a new approach was employed in this study. The Fe-Nb-RE associated tailings were first reduced and iron-slag was separated at low temperatures under super gravity. This process transformed Nb and REEs into a Nb/REEs-rich phase in the primary enriched slag, which was then separated from the slag by super gravity to obtain a high-grade enriched sample. The end result was a sample with Nb2O5 and RE2O3 mass fractions of up to 24.98 wt% and 30.01 wt%, respectively. This process successfully concentrated Nb and REEs from associated elemental impurities and gangue minerals in the Fe-Nb-RE associated ultra-low-grade tailings, making extraction easier, optimizing subsequent leaching/dissolution, and reducing the number of steps and material flows required in the downstream hydrometallurgical extraction.

The precipitation and growth behaviours of perovskite crystals from CaO–TiO2–SiO2–Al2O3–MgO melt in a super-gravity field with different gravity coefficients at different cooling rates were investigated in this study. In a super-gravity field, the first precipitated perovskite crystals migrated quickly along the super-gravity direction, and gradually concentrated and grown into larger crystals in the bottom area, while the new perovskite crystals keep precipitating and concentrating towards the bottom area simultaneously. Furthermore, by simplifying the layered samples obtained by super-gravity into three areas along super-gravity direction: slag-rich area, interface area and perovskite-rich area, the variations in volume fractions and equivalent diameters of perovskite crystals against gravity coefficients and cooling rates were obtained by weighting the values of the three areas. And the results indicated that increasing gravity coefficient was not only beneficial for the precipitation but also for the growth of perovskite crystals in the slag melt. Afterwards, the effects of super-gravity field on the precipitation and growth kinetics of perovskite crystals were further discussed.

Residual phosphorus (P) is one of the main factors limiting the recycling of steelmaking slag from the steelmaking process. In this study, the effect of ba

<title>Abstract</title> The adsorption interaction between cotton fibers and dye maxilon blue GRL was systematically investigated under varying contact times, initial dye concentrations, agitation speeds and temperatures; and the adsorption capacity of dyes increases with the increase of those four parameters. Analysis of adsorption isotherms revealed superior fit with the Langmuir model compared to the Freundlich model, and both the saturated adsorption capacity <italic>q</italic>_m and adsorption capacity <italic>K</italic>_F exhibited temperature-dependent enhancement. The adsorption of dye onto cotton fibers could be described satisfactorily by the pseudo-second-order rate model, where both the equilibrium adsorption amount <italic>q</italic>_e and the apparent rate constant <italic>k</italic>₂ increase with elevated agitation speeds and temperatures. Thermodynamic analysis yielded an enthalpy change Δ<italic>H</italic>* of 63.5 kJ·mol⁻¹ and Gibbs energy change Δ<italic>G</italic>* of 8.7 kJ·mol⁻¹, collectively indicating a non-spontaneous endothermic process. The negative entropy change (Δ<italic>S</italic>* = ⎼209.3 J·mol^{− 1}·K^{− 1}) suggested reduced molecular randomness at the solid-liquid interface during adsorption. The low activation energy (<italic>E</italic>ₐ = 11.34 kJ·mol⁻¹) and adsorption enthalpy change confirmed physical adsorption mechanisms dominated by hydrogen bonding. Understanding the interaction between fiber and dye is helpful for optimizing dye utilization in industrial processes and engineering modified cotton fibers for wastewater decolorization.

A laboratory scale rotary furnace has been developed for gaseous reduction of ultrafine metallurgical dusts to produce iron, zinc and other metal resources at submelting point temperatures. The kinetics of this process is much higher than say static or moving bed systems. By way of example, using dust with 38%Fe and 10%Zn, a 17 min treatment at 900°C produces an iron product of ∼92%Fe and a zinc product of ∼86%Zn.

The thermal decomposition mechanism of K-feldspar with industrial waste of FGD gypsum to produce soluble potassium (K) salt was investigated. Effects of the reaction temperature and the amount of reagents used on the recovery of K were studied. The results showed that increasing the reaction temperature and mass ratio of CaCO3/KAlSi3O8 and CaSO4/KAlSi3O8 was beneficial to the decomposition of K-feldspar. The recovery ratio of K was higher than 90% with the mass ratio of KAlSi3O8:CaSO4:CaCO3 = 1:1:3 at 1373 K for 40 min, and the product K2SO4 with a purity of 91.3% was obtained. A crystal structure disintegration mechanism for KAlSi3O8 was proposed on the basis of the characterization of phase transformation sequences by XRD, FTIR, and SEM/EDS. It was found that two product layers formed successively during the KAlSi3O8 decomposition process. K was enriched in the outer product layer, and the decomposition rate was controlled by Ca diffusion through the inner one. Based on the experimental results, a kinetics model of K-feldspar decomposition was established using the Crank-Ginstling-Brounshtein equation, and the apparent activation energy was determined.

V containing spinel phase was successfully separated from vanadium slag by centrifugal casting. With the process parameters of G = 900 (where normal gravity G = 1), t = 20 min and T = 1557 K, almost all V containing spinel phase is enriched in the concentrate, while the tailing is made up of Fe2SiO4, Fe2TiO4 and Mn2VO4 phases. Under the hypothesis that the vanadium and silicon exist in the slag as V2O3 and SiO2, the mass fractions of V2O3 and SiO2 in the concentrate are 25·2 and 2·2%, while those of the tailing are 0·8 and 32·2% respectively. The recovery ratio of V in the concentrate is up to 97·4%, while the removal ratio of Si is 92·5% by centrifugal separation.

It reports the selective crystallization and separation of B in B-bearing slag. The competitive crystallization behavior of B, Si, and Mg in B-bearing slag is reported in Sect. 3.1. The study on two-stage separation of olivine and suanite, the selective separation of last precipitated suanite, and the crystalline phase transformation and one-step separation of suanite in molten B-bearing slag are included in Sect. 3.2, 3.3, and 3.4, respectively.

The RE-bearing slag with a considerable concentration of rare earths have attracted widespread attention in recent years, while the serious lack of basic data greatly limits its development and utilization. The viscosity of RE-bearing slag and kinetics for nucleation and growth of RE-phase are basic data which closely related to the mass transfer, separation and recovery of rare earths in the slag. However, the current reports on viscosity of RE-bearing slags are extremely scanty, and the existing viscosity models also have limitations due to the lack of thermodynamic data of rare earths. In this study, the viscosities of various RE-bearing slag systems (CaO–SiO2–Ce2O3, CaO–SiO2–CaF2–Ce2O3 and CaO–SiO2–CaF2–P2O5–Ce2O3) were firstly measured by the rotating cylinder method, and the change rules of viscosity for RE-bearing slag with CaF2 and P2O5 were reported. Moreover, the nucleation and growth kinetics of various RE-phases (calcium cerite, cefluosil, and britholite) were comprehensively studied, and the crystallization ability of RE-phases in RE-bearing slag was found to be cefluosil, followed by britholite and calcium cerite. The basic data reported in this study provide the necessary reference and guidance for recovery and utilization of rare earths in RE-bearing slag.

Reports the selective crystallization and separation of P in P-bearing slag. The solid solution behavior of P and selective crystallization behavior of C2S-C3P in CaO–SiO2–FeO–MgO–P2O5 system are reported in Sect. 6.1. The study on motion and separation of C2S–C3P in CaO–SiO2–FeO–MgO–P2O5 system and steelmaking slag is included in Sects. 6.2 and 6.3, respectively.