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Energy input is an important factor affecting flotation effect, and energy input is mainly determined by stirring speed and stirring time. In order to explore the influence of energy input on the flotation kinetics of fine pyrochlore, the classical first-order kinetic model was determined as the best fitting model for the flotation process of fine pyrochlore by flotation rate test. The kinetic parameters of fine pyrochlore under different energy input were investigated. The mechanism of the agglomeration state of fine chaste stone and the adsorption capacity of surface reagent on the flotation kinetics under different energy input conditions was studied by means of optical microscope and mineral surface adsorption. The results show that the kinetic parameters of flotation rate constant k and the theoretical maximum recovery increase first and then decrease with the increase of energy input, and the maximum values of 0.038 78 and 89.711 8% are obtained at the stirring speed of 1 602 r/min and the stirring time of 3 min. The average particle size of the aggregates and the adsorption capacity on the mineral surface with the increase of energy input were consistent with the change trend of flotation kinetic parameters, and the maximum values of 141. 01 7m and 1. 377 mg/g were obtained at the stirring speed of 1 602 r/min and the stirring time of 3 min. When the energy input is too high or too low, the kinetic parameters are at a low level. The energy input is too low, the agglomeration effect is not good, there are more dispersed minerals, and the adsorption capacity of chemicals on the surface of minerals is low, which is not conducive to the collusion and adhesion between bubbles and particles. High energy input will destroy the formed clusters and the adsorbent layer on the surface, reduce the particle size of clusters and desorption of agents, and reduce the adhesion efficiency between bubbles and particles. Appropriate energy input is conducive to the formation of fine chastocystic agglomeration, enhance the adsorption of chemicals on the mineral surface, improve the collision and adhesion efficiency between bubbles and parties, and thus improve the flotation efficiency. [ABSTRACT FROM AUTHOR]

Objective The Shaxiongdong carbonatite-alkaline related Nb-REE deposit is located in the Wudang area of the south Qinling Belt, but the studies on Nb mineralization in this deposit are scarce. Methods Detailed petrographic observations were made by using polarizing microscope, optical cathodoluminescence and backscattered electron testing. The structure, composition and symbiotic relationship of the minerals were identified. The composition of two types of pyrochlore was analyzed by electron probe and the mechanism of niobium enrichment was discussed. Results The Shaxiongdong complex consists of three types of rocks that are spatially closely related: Meta-pyroxenite, syenite and carbonatite, of which the carbonatites are the major hosts of Nb mineralization characterized by main pyrochlore. This implies that Nb was concentrated to economic values in the carbonatite stage after extensive fractionation of the parental carbonated silicate magma. The pyrochlore in the deposit can be classified into two types on the basis of micro-textures: ① The primary ones (Pcl1) are euhedral to subhedral and display oscillatory zoning, implying their direct crystallization from carbonatite melts; ② The altered grains (Pcl2) exhibit patchy zonation under BSE images due to hydrothermal alteration. EPMA analytical results indicate that both types are rich in Nb and F at the B and Y sites, respectively, and at the A site, they are similarly mostly rich in Ca, thus named F-Ca-pyrochlore, with minor Na, thus named F-Na-pyrochlore. Conclusion The good positive correlations between F and Nb in both types of pyrochlore indicate that F plays a key role in the enrichment of niobium during magma differentiation. On the other hand, compared to the primary pyrochlore, the altered ones have relatively low Nb2O5, CaO, Na2O and F but high UO2, Ta2O5, SrO and SiO2, indicating that the fluids responsible for pyrochlore alteration are rich in Sr, Si and U, and the alteration tends to mobilize Nb in early pyrochlore, a process that is able to lower the Nb budgets of the deposit.

BACKGROUND: With the increasing demand for scandium resources, countries around the world have carried out scandium metallogenic mechanism research and prospecting in recent years. One of the key research contents is to clarify the occurrence characteristics of scandium. According to previous studies, scandium mainly exists in the form of isomorphism and ion adsorption in various scandium deposits. At present, more than 800 kinds of scandium-bearing minerals have been found. The scandium resource of the Bayan Obo deposit is large, which has the characteristics of dispersed distribution and low content. Scandium enters other minerals in the form of isomorphism and no independent scandium mineral is found. Due to the limitation of testing technology and sampling, there is no accurate quantitative research to systematically explore the occurrence characteristics of scandium in different minerals in the Bayan Obo deposit. Therefore, the identification of the main scandium-bearing minerals is insufficient, which is not conducive to further exploration of the enrichment mechanism of scandium and the utilization of scandium resources in the deposit. OBJECTIVES: To understand the occurrence of Sc in different minerals of the Bayan Obo deposit. METHODS: 34 kinds of minerals in the Bayan Obo deposit were systematically determined by electron probe microanalyzer (EPMA) technology. RESULTS: The test results showed that the average scandium content (Sc2O3) in 6 minerals was more than 0.100%. They were samarskite (with average Sc2O3 content of 2.485%), columbite (1.263%), manganocolumbite (0.251%), dark purple fluorite (0.181%), thorianite (0.145%) and Y-rich aeschynite (0.124%) from high to low. Samarskite had the highest scandium content (3.093%). The content of scandium in 16 minerals ranged from 0.004% to 0.067%, which were fergusonite (with average Sc2O3 content of 0.067%), alkaline amphibole (0.062%), ferrothorite (0.060%), pyrochlore (0.049%), fersmite (0.031%), bastnaesite (0.028%), apatite (0.028%), britholite (0.025%), monazite (0.023%), aegirine (0.02%), biotite (0.019%), humite (0.011%), fergusonite-(Ce) (0.008%), feldspar (0.007%), magnetite (0.005%), albite (0.004%). Scandium was not detected in the other 12 minerals. CONCLUSIONS: Samarskite has the highest scandium content in the deposit, and the 6 main scandium-bearing minerals are samarskite, columbite, manganocolumbite, dark purple fluorite, thorianite and Y-rich aeschynite. Among the 34 minerals, the content of scandium in 22 minerals is higher than the detection limit of EPMA, and scandium is distributed in a dilute manner. The occurrence of scandium is related to titanium, yttrium and thorium, and the correlation coefficients are 0.869, 0.835 and 0.720, respectively. Scandium is closely related to niobium minerals such as columbite, manganocolumbite, fersmite and Y-rich aeschynite. It can be considered to comprehensively utilize scandium and niobium resources at the same time. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Aeronautical Materials is the property of Editorial Board of Journal of Aeronautical Materials and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this work, the difference of adsorption behavior of three collectors on pyrochlore surface were studied by DFT and flotation experiment to provide theoretical support for selecting more efficient collectors. The results of calculation and XPS analysis show that the strong reactivity of Nb and Ca in the pyrochlore crystals and the instability of the dissociation surface enable collector to combine with it to produce flotation effect. BHA and DDA adsorbed on pyrochlore surface mainly through deprotonated and non deprotonated functional groups, the adsorption active site was Nb, so they have strong collection and selectivity, while NaOL was chemisorption mainly through the interaction of RCOO and Ca on pyrochlore surface, so its collection and selectivity are the worst The verification experiment shows that under the suitable flotation conditions, DDA has the best flotation effect and the recovery rate can reach 89%, and BH A and NaOL is slightly worse. [ABSTRACT FROM AUTHOR]

Copyright of Journal of the Chinese Society of Rare Earths is the property of Editorial Department of Journal of the Chinese Society of Rare Earths and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The chemical composition, mineral composition, occurrence state of niobium and niobium minerals’ dissemination characteristics of Nb-bearing mineral raw materials of Bayan Obo were investigated by means of mineral liberation analyzer ( MLA), X-ray diffraction, scanning electron microscope, energy disperse spectroscopy and chemical analysis. The research results show that the chemical and mineral composition of the raw materials are complex, of which the grade of niobium and the total mass fraction of rare earth oxide are 1.10% and 1.37%, respectively. The main niobium minerals are nioboaeschynite, ilmenorutile, pyrochlore, dingdaohengite, mangancolumbite, niobite, baotite, and fergusonite, in which the highest mass fraction of nioboaeschynite, the highest mass fraction of niobium in mangancolumbite, and the highest metal distribution rate of niobium in nioboaeschynite are 1.84%, 54.34%, and 44.85%, respectively. The particle size of niobium minerals is relatively fine. Except nioboaeschynite, the liberation degrees of the rest niobium minerals are relatively low, which are mainly attached with riebeckite and iron oxide. From the perspective of process mineralogy, only by solving the problems of efficient enrichment of micro fine-grained niobium minerals and separation of Nb / Ti in raw niobium-bearing mineral materials could the goal of efficient and comprehensive utilization of Bayan Obo niobium mineral resources be achieved. [ABSTRACT FROM AUTHOR]

Catalytic combustion is an efficient way to remove soot particulates from automobile exhausts. A series of rare earth pyrochlore oxides La 2 Sn 1.8 TM 0.2 O 7 (TM=Sn, Mn, Fe, Co, Cu) were prepared with CTAB-assisted sol-gel method. The products were characterized by XRD,N 2 Adsorption-Desorption, SEM, FT-IR, H 2 -TPR and PL techniques. Their catalytic activity for soot oxidation was investigated by TPO under tight conditions in both O 2 and NO+O 2 atmospheres. After calcination at 900℃, the as-synthesized oxides with pure pyrochlore phase displayed nanospheres with diameter of 30-60 nm and relatively large surface areas. The partial substitution of Sn with transition metals largely influenced the reduction behavior of pyrochlores especially on the low temperature range in H 2 -TPR profiles, which was due to the interactions between Sn and transition metals. The improved oxygen mobility might be derived from the structure defects induced by transition metals doping, which could be helpful in oxidation reactions. In comparison with uncatalyzed reactions, the La 2 Sn 2 O 7 catalyst exhibited modest catalytic activity for soot combustion, while transition metals incorporation further enhanced the activity and selectivity. The improved activity of transition metals doped samples was likely to be associated with the improved reducibility and increased surface oxygen vacancies on the pyrochlore oxides. The presence of NO in the gas phase significantly enhanced the soot oxidation activity, which was due to the promotion effect of NO 2 . Especially, the densities of active oxygen sites and turnover frequency (TOF) values of the catalysts, quantified by isothermal anaerobic titration with soot as a probe molecule, were used to explain the different soot combustion behaviors. Among the pyrochlore oxides, the Co-doped pyrochlore sample displayed the highest ignition activity and the largest intrinsic activity with TOF of 3.20×10 -3 s -1 .