147 publications from this institution
A new approach of removing the phosphorus-rich phase from high-phosphorous iron ore by melt separation at 1573 K in a super- gravity field was investigated
Rare-earth concentrate obtained through mineral processing of rare-earth ore was characterized by a high rare-earth content and various rare-earth minerals. To effectively recover rare earth from the rare-earth concentrate, a novel method of enriching rare-earth elements and separating the RE-rich phases from Bayan Obo rare-earth concentrate by super gravity was proposed in current study. The mineral evolutions of rare-earth phases and the migrations of rare earth in various phases with temperature rising were investigated. The variations of mineralogical compositions and microstructures indicated the rare-earth phases transformed into fine britholite, cerium oxyfluoride, rare-earth ferrate and monazite particles at a low temperature range of 1423 K–1523 K, which transformed further into lager equiaxed cerium oxyfluoride crystals and most rare-earth elements enriched into the cerium oxyfluoride phase significantly at a higher temperature range of 1573 K–1773 K. Consequently, separation of the RE-rich phases was carried out at the high temperature range in a super-gravity filed, and the cerium oxyfluoride phase and the britholite containing slag phase were effectively separated by super gravity.
Replicated open-cell aluminum foams were produced by infiltration casting in super-gravity fields. Infiltration of preforms packed by NaCl particles with different sizes was conducted to demonstrate the technical feasibility of this method. The relative densities between 0.25 and 0.34 of the aluminum foams were obtained by varying the NaCl particle size of the preform from 600 to 200 μm. Increasing the gravity coefficient (G) increased the centrifugal pressure (P c) and correspondingly improved the relative densities and structural integrity of the resulting foams. As P c increased, the aluminum foam exhibited a transition from a structure of smooth struts to a relatively complex structure where many protrusions extended inside the pores from the surface of the struts. Also, the specific relationship between the minimum centrifugal pressures necessary to produce self-standing aluminum foams and the NaCl particle size of the preform was established. The minimum centrifugal pressures of 32, 49 and 83 kPa were required for aluminum foams with pore sizes of 600, 400 and 200 μm, respectively. Preliminary results show that super-gravity infiltration is promising to be a practical manufacture process for replicated open-cell aluminum foams.
Selective precipitation and concentrating of perovskite crystals from titanium-bearing slag melt in the supergravity field was investigated in this study.
Reports the selective crystallization and separation of REEs in RE-concentrate. The mineral evolution and mineral reconstruction behaviors of RE-concentrate are reported, and the study on selective concentration and selective separation of cerium oxyfluoride in RE-concentrate is included in Sects. 5.1 and 5.2, respectively. The study on stepwise crystallization, stepwise concentration, and stepwise separation of REEs (Ce, La, Pr, Nd) in RE-concentrate is included in Sect. 5.3.
As an environmentally hazardous waste, blast furnace (BF) flue dust had a potential to reduce CO2 emission if recycled as fuels or reducing agents due to the high carbon content. The structure of carbon was a principal factor to the reactivity of carbon conversion and therefore was highly relevant to efficient utilization. In this work, the characteristics and chemical structures of carbonaceous materials in BF flue dust were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared, and Raman analysis. The results showed that the aromatic structure of crystalline carbon was dominant in carbonaceous materials. Polymeric aromatic carbon and oxygen-containing groups (epoxide and esters carbon) existed on the surface. The stacking height (Lc), the in-plane crystallite sizes (La), and the interlayer spacing (d002) of the aromatic structure layer were 2.45, 3.31, and 0.347 nm, respectively. The mass ratios of chars and cokes to carbonaceous matter were estimated to be 90.56% and 9.44%, respectively, by Raman spectroscopy. Then, the combustion reactivity was studied by thermogravimetric analysis using the Kissinger–Akahira–Sunose kinetics method. The activation energy as a function of conversion degree was determined. The results thus provided fundamental information for the utilization of BF flue dust for thermochemical conversion.
In this study, the investigation on the isothermal enrichment of P-concentrating phase from CaO-SiO 2 -FeO-MgO-P 2 O 5 melt with super gravity was carried out.The results show that there was an obvious stratification appearing in the sample after centrifugal enrichment.The upper part of the sample is loose and porous, while the lower part is smooth and compact.With the help of metallographic microscopy and X-ray diffraction, it is found that the P-concentrating phase gathered in the upper part, while it is hard to find any P-concentrating phase in the lower part of the sample.In addition, the volume fraction and equivalent diameter of P-concentrating phase present gradient distribution along the direction of super gravity.After centrifugal enrichment, the mass fraction of P 2 O 5 in the concentrate is up to 4.92%, while that in the tailing is just 1.08%.The recovery ratio of P 2 O 5 in the concentrate is up to 72.62% with the gravity coefficient G = 600, time t = 20 minutes and temperature T = 1 623 K.
Sustainable utilization of rare earth elements (REEs) in REE-bearing slag has recently attracted significant interest in industries and research community. However, few thermodynamic and kinetic data have been reported for REEs systems, which greatly limits the sustainable utilization of REE-bearing slag in ceramics and other fields. Therefore, the isothermal phase diagram of CaO–SiO2–CaF2–Ce2O3 system was constructed, and the phase equlibria data of REEs in REE-bearing slag were provided in this study. On this basis, the phase equilibria of the RE-phase in CaO–SiO2–CaF2–Ce2O3 system was investigated, the exact initial crystallization temperature of cefluosil (Ce9.33-xCax(SiO4)4O5-0.5xF2) in the system was 1450 K and the cefluosil crystals were in a hollow hexagonal prism shape. The isothermal crystallization and growth kinetics of cefluosil were further studied. The crystallization kinetics of cefluosil were found to be described by the Johnson-Mehl-Avrami-Kolmogoro (JMAK) equation (when χ < 1), and the growth of cefluosil in the non-equilibrium stage is controlled by the coarsening energy. In this research, the thermodynamic and kinetic data of REEs in CaO–SiO2–CaF2–Ce2O3 system are supplied, which providing the theoretical basis for sustainable utilization of REEs in REE-bearing slag.
With the massive consumption of rare earth resources, the recovery of rare earth elements (REEs) from secondary resources has become a focus of attention. It is economically necessary to recover REEs from Bayan Obo RE-containing blast furnace slag (RE-BFS), which contains considerable REEs. However, due to the lack of relevant thermodynamic data, it is difficult to effectively recover REEs from RE-BFS. Therefore, the isothermal phase diagram of CaO–SiO2–Al2O3–Ce2O3 at 1100 °C was constructed in this work, according to the principle of phase diagram construction combined with the method of equilibrium experiments. The optimal rare earth equilibrium phase in this system was defined as Ce4.667-xCax(SiO4)3O1-0.5x. According to the actual composition of the RE-BFS, a dominant separation region of L + Ce4.667-xCax(SiO4)3O1-0.5x was obtained in the phase diagram. Subsequently, the extraction of REEs in the RE-BFS could be completed by solid–liquid separation, which allowed economic benefits without affecting the environment. The data reported in this work provide a theoretical basis for solving the problem of recovery from RE-containing secondary resources and developing high value-added materials.
The effects of super-gravity field on metal–slag separation at different gravity coefficients were investigated in this study. In a super-gravity field, the liquid metal concentrated along the direction of super-gravity, while the molten slag migrated and aggregated along the opposite direction thereafter separated from the metal. Moreover, a straight interface between the metal and slag appeared in the perpendicular direction to the super-gravity. Consequently, increasing the gravity coefficient could definitely increase the driving force of phase separation between metal and slag, and so enhance the removal of oxide and the purity of metal significantly.
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 industrial RE‐bearing (rare‐earth‐bearing) slag has a considerable concentration of rare‐earth elements (REEs), so the recovery of REEs resources from these systems has attracted widespread attention. However, the basic data of RE phases is seriously lacked and divergent, which greatly limits the efficient utilization. In this study, in situ separation of RE phases from RE‐bearing slag systems was conducted via super gravity, and the high‐purity crystals of calcium cerite (CaO: 13.53 wt.%, SiO 2 : 26.02 wt.%, Ce 2 O 3 : 65.45 wt.%) and cefluosil (CaO: 14.67 wt.%, SiO 2 : 22.14 wt.%, CaF 2 : 2.64 wt.%, Ce 2 O 3 : 67.23 wt.%) were selectively separated from the CaO–SiO 2 –Ce 2 O 3 and CaO–SiO 2 –CaF 2 –Ce 2 O 3 systems with the high REEs recovery percentages of 96.10% and 98.23%, respectively. Based on the characterization of high‐purity calcium cerite and cefluosil crystals, the chemical formula, crystal structure, and Rietveld refinement were characterized, and the data has been assigned the deposition numbers of 2130965 and 2142394 in CCDC database. This study supplements the lack of basic data of RE crystals and provides theoretical reference and guidance for the utilization of RE‐bearing slag systems.
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.
Electronic waste (e-waste) contains plenty of toxic substances as well as valuable metals (e.g. Pb and Sn). The storage of e-waste presents a long-term environmental issue but also an opportunity to recover valuable metals. Supergravity asa novel technology was used to separate and recover Pb-Sn alloy from e-waste in this study. Based on the different melting points of various metals, it can separate Pb and Sn from e-waste by melt separation in a supergravity field produced by a centrifugal apparatus. Several parameters affecting the recovery of Pb and Sn were investigated. Under optimal conditions including a gravity coefficient of 1000, centrifugal time of 5min, and temperature of 410°C, the recovery values of Pb and Sn were 54.41% and 41.94%, respectively. The (Pb+Sn)% of Pb-Sn alloy was 94.84wt.% and the mass ratio of Pb/Sn was 0.66. This Pb-Sn alloy was suitable as raw materials for industrial applications. Some solid solutions were formed with Sn may be the main reason for the low recovery of Sn.
A new approach to enrich MFe and RO phase from the converter slag by super gravity was investigated. The samples obtained by the gravity coefficient G=600 and cooling rate V=5K/min from 1623K to 1373K appeared significant stratification and the MFe gathered at the...
Perovskite phase was successfully separated from CaO-TiO2-SiO2-Al2O3-MgO melt by super gravity. Under the hypothesis that the titanium ex
The ‘plainification of materials’ has been conceptualized to promote the sustainable development of materials. This perspective, for the first time in the field of biomaterials, proposes and defines ‘plain metallic biomaterials (PMBs)’ with demonstrated research and application case studies of pure titanium with high strength and toughness, and biodegradable, fine-grained and high-purity magnesium. Then, after discussing the features, benefits and opportunities of PMBs, the challenges are analyzed from both technical and regulatory aspects. Regulatory perspectives on PMB-based medical devices are also provided for the benefit of future research, development and commercialization.
In order to take the advantage of the large reaction surface of fine iron ore concentrates and expect a high reaction rate without sticking or agglomeration problems, a suspension gas-solid reaction system was designed to explore the feasibility of fast direct reduction of fine iron ore. In this study, upward gas flow was used to prolong the particles' falling time. Pure silica particles were chosen as the dispersion agent. The Stokes gas-particle model with the relaxation time concept was applied to accurately model the falling process. Highly metallized porous iron particles over 90% of Rd (reduction degree) were obtained at 1273 K with 20.1 s of hydrogen reduction. The morphology evolution characteristics of the fine particles during reduction were investigated via SEM, and a conceptual diagram was formulated in this paper in order to well understand the relationship between the reduction condition and the structural evolution. The shrinking core model was introduced to analyzing the reduction kinetics in this experiment system, which indicates that the microstructure evolution of the particle during reduction can be influenced by temperature and the resistance of internal mass transfer cannot be ignored under this experiment condition especially in the later stage of reduction.
