Publications

The iron-slag separation of gaseous reduced Bayan Obo ore was conducted at a low temperature by super-gravity for the aim of separating rare earth and fluorite phases. Driven by the super-gravity, the slag melt went through the filter, whereas the iron grains were effectively intercepted by the filter. Moreover, the fluorite remained in solid particles and migrated to the lower slag, while all REEs precipitated into Ca3(Ce,La,Pr,Nd)2[(Si,P)O4]3F crystals and concentrated in the bottom slag at 1373 K–1473 K.

NdFeB waste is both a secondary resource rich in rare earth elements and a hazardous waste, posing significant recycling potential alongside environmental concerns. However, conventional recycling methods face significant challenges due to high separation temperatures and limited product purity. In response to these issues, this study introduces a novel recycling approach that integrates selective oxidation with a supergravity separation technique, enabling the efficient recovery of rare earth resources from NdFeB waste. Experimental results demonstrate that the addition of 14 wt% carbon powder effectively modulates the oxygen partial pressure within the system, facilitating the formation of rare earth oxides while maintaining iron in its metallic state. Following this, supergravity separation is employed within a temperature range of 1260°C to 1350°C to achieve effective segregation of iron from REEs-rich slag. The findings reveal that, when compared to the rare earth slag produced by traditional slag-iron separation methods at 1550°C, the new process at 1320°C yields a REEs-rich slag with a rare earth content increase from 67.3 wt% to 82 wt% and an improvement in the RE extraction rate from 82.7 % to 99.9 %. These results highlight the potential of this low-temperature, highly efficient process for the recovery of high-purity REEs-rich slag, offering a promising technological pathway for the environmentally sustainable recycling of NdFeB waste.

It reports the selective crystallization and separation of REEs in RE-bearing slag. The selective crystallization behaviors of RE in RE-bearing slag, including the isothermal phase diagram of CaO–SiO2–CaF2–Ce2O3 system, the phase equilibria of RE-phase, and the isothermal crystallization and growth kinetics of RE-phase are reported, respectively, in Sect. 4.1. The study on selective separation of RE in RE-bearing slag, including the motion and separation behaviors of cefluosil in molten RE-bearing slag, is included in Sect. 4.2.

The lack of thermodynamic data on vanadium slag, the main raw material for vanadium extraction, limits the efficient extraction of vanadium from vanadium s

Experiments on the solid-state reaction between iron ore particles and MgO were performed to investigate the coating mechanism of MgO on the iron ore parti

The reduction behavior of single iron ore particle was investigated at high temperatures (above 1373 K) with CO/CO2 mixture. A high-temperature la

Glass ceramics were synthetized using Cr2O3 and CaF2 as additives, and their structure, crystal growth behavior, and physicochemical properties were investigated. The results showed that an excessive amount of Cr2O3 leads to the formation of a spinel structure in the glass matrix and an increase in the number of Q3Si units. The addition of CaF2 promoted the decomposition of Q2Si into Q1Si and Q3Si. Compared with the sample with Cr2O3 alone, the addition of CaF2 helped reduce the glass transition and crystallization temperatures, forming sharper crystallization peaks. Although CaF2 increased the activation energy of crystallization, it increased the degree of crystallinity and Avrami parameter (2.019). In terms of the microstructure, the sample added with CaF2 formed a snowflake-like structure with a spinel core. An excessive amount of spinel reduced the strength of the samples. The samples (1.5Cr2O3-3.5CaF2) exhibited a maximum flexural strength of 149.85 MPa and a good chemical resistance.

In this study, a novel method was developed for direct preparation of magnesium borate (Mg2B2O5) ceramic from boron-bearing slag. The amorphous boron was efficiently enriched into Mg2B2O5 via crystalline phase transformation in the condition of B/S (B2O3/SiO2) = 1.20 and wt.% (MgO) = 36.00. High-purity Mg2B2O5 crystals were fully recovered from molten slag by super-gravity separation at G ≥ 500 and t ≥ 240 s. The Mg2B2O5 ceramic was directly prepared at various temperature by using the recovered Mg2B2O5, and the Mg2B2O5 ceramic displayed a favourable microwave dielectric properties including the dielectric constant ( ε r ) of 6.05, the quality factor (Q × f) of 38,147 GHz and the temperature coefficient of resonant frequency (TCF) of -20.98 ppm/K. Compared with synthetic methods that use high-purity oxides, this study provides a green and economical method for direct utilisation of industrial slag to prepare microwave dielectric materials.

As mining waste, alunite is a potential resource to produce potassium salt. The decomposition of alunite is closely associated with the recovery of soluble potassium. In this study, the effect of CaO on phase transformation of alunite in the desulfation stage was examined. The results showed that CaO was beneficial to the desulfation of alunite. The decomposition temperature to obtain soluble potassium salt (K2SO4) was reduced from 800 °C to 700 °C by adding CaO. When the mass ratio of CaO/alunite was 0.1, 81% of soluble potassium was extracted by water leaching after calcination at 700 °C for 2 h. The mechanism of CaO to promote the disintegration of alunite was proposed through analyzing the phase transformation sequences. Alkaline Ca ion was inclined to bond with acidic [SO4] groups, and thus the breakage of S–O linkages between [AlO6] octahedron and [SO4] tetrahedron were improved. Monomer [SO4] tetrahedrons were released to form K2SO4 at a lower decomposition temperature. With the increase of the amount of CaO, the excess CaO bonded with neutral Al. [AlO6] tetrahedrons in alunite transformed into [AlO4] octahedrons due to the breakage of the Al–O network. Al3+ was dissociated and bonded with [SO4] tetrahedron to form soluble Al salts.

No abstract is provided for this article.

The phosphorus migration mechanism during melting separation of non-carbon-reduced high phosphorus iron ore was investigated. Firstly, the equilibrium comp

Copper smelter dust is an ultrafine hazardous waste containing various heavy metallic elements. This manuscript proposed a novel method for efficient recovery of crown zinc and metallic copper from copper smelter dust, including evaporation and condensation of zinc vapor, and super-gravity separation of copper droplets. Firstly, the fine zinc oxide powders mixed in the dust were efficiently transformed into zinc vapor and escaped from the dust through carbothermal reduction at 1373–1573 K, which was effectively condensed into the metallic zinc named as “crown zinc” above its melting point. Subsequently, the dispersed fine copper droplets were evidently separated from the residue above the melting point of Cu as driven by super-gravity. Accordingly, crown zinc and metallic copper, with high purity of 98.57 wt% and 99.99 wt%, were efficiently recovered from the copper smelter dust with the high recovery ratios of 99.94% and 98.86%, respectively.

In order to expand the application of the electrodeposited Ni-Fe alloy foil, their mechanical and magnetic properties were studied after heat treatment. The development of grain growth during annealing was in-situ online investigated using a heating stage microscope, and the texture was analyzed via X-ray diffraction (XRD) and electron back-scattered diffraction (EBSD). The results indicated that abnormal grain growth usually occurred during annealing at 1000–1050 °C. The {111} oriented grains preferentially grew as the annealing temperature and holding time increased. The plasticities of the electrodeposited Ni-Fe alloy foils after heat treatment were better than those of the original samples. The excellent ductility was obtained without a loss in magnetic properties after annealing at 1100 °C for 6 h.

In this study, the effects of different Cr2O3 contents and optical basicity (denoted by Λ) on the viscosity and structure of the Cr2O3-bearing CaO-SiO

The effects of particle size distribution (narrow, Gaussian, binary and flat) on high-temperature defluidization behavior of iron powder were investigated. The fluidization characteristics were studied involving minimum fluidization velocity, bubbling velocity and bed voidage. The thermo-mechanical analysis was applied to examine the sintering temperature and surface viscosity of iron powder due to surface softening. The results indicated that the effects of PSD on defluidizaton were dependent on temperature. The Gaussian distribution was favorable to fluidization and presented better fluidization quality at lower temperatures. However, at higher temperatures, the narrow distribution exhibited a higher defluidization temperature and thus a lower agglomeration tendency due to a larger apparent viscosity and lower particle stickiness. Therefore, the PSD apparently affected not only hydrodynamic behavior, but also particle adhesion of bed materials for defluidization.

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