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Simultaneous extraction of uranium and niobium from a low-grade natural betafite ore

  • Zihu Lv , Dengkui Zhao , Qiliang Sun , Changmiao Liu , Hongwei Cheng , Fei Yang and Bo Zhang EMAIL logo
Published/Copyright: February 2, 2023
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High Temperature Materials and Processes
From the journal High Temperature Materials and Processes Volume 42 Issue 1

Abstract

This work efficiently investigated the simultaneous extraction of uranium (U) and niobium (Nb) from a low-grade natural betafite ore by using novel technique, namely, sulfatizing roasting coupled to sulfuric acid leaching process. First, the sulfatizing roasting was adopted to alert the properties of the raw ore, aiming to destroy the crystal structure of the ores and convert the valuable elements to soluble sulfate compounds. Moreover, the influences of the parameters affecting the sulfatizing roasting including roasting temperature, amount of sulfuric acid, and roasting time were studied. The results indicated that the extraction of U and Nb from the ores with sulfatizing roasting was an order of magnitude higher than the extraction of U and Nb from the ores without roasting under the same test conditions. Then, the effects of amount of sulfuric acid concentration, liquid–solid ratio, leaching temperature, and leaching time on U and Nb recoveries were systematically investigated. To verify the process parameters of extracting U and Nb for the novel technique, three validating tests were conducted, and the results showed that over 95% of U and 85% of Nb were leached out under the optimal conditions. The novel technique was proven as advantageous since it conspicuously improved the leaching rates of U and Nb and promoted the refractory natural betafite ores to become an economic source for uranium.

Keywords: uranium; niobium; betafite; leaching; sulfatizing roasting

1 Introduction

With the intensification of the world energy crisis and environmental pollution, nuclear energy, as an efficient, clean, most potential, and promising new energy, has attracted prominent attention of all countries in the world [1,2,3,4,5]. However, the development of nuclear energy is inseparable from the supply security of nuclear fuel such as uranium (U), which seriously restricts the sustainable development of nuclear power. Nowadays, the major challenge for nuclear energy industry is a severe decline in the reserves for high grade U ores that can be financially exploited by conventional technologies [6,7,8,9]. Hence, the commercial focus has largely been on exploiting low-grade U minerals such as the betafite ores.

Betafite identified as A2B2O7-x (OH) x is a U pyrochlore group mineral, in which A = Na, K, Ca, Sr, Sn, Ba, Pb, Bi, REE, and U and B = Ti, Nb, Ta, Zr, and Al [10]. Because of the relatively low content of U and the complex crystal structure, it is difficult to extract U from the betafite ores using traditional techniques such as alkali leaching, acid leaching, and bioleaching. Yang et al. synthesized five U minerals and the bioleaching process was employed to investigate the leaching behavior for U [11]. The results demonstrated that the leaching rate of U-bearing minerals was in the order of pitchblende ≈ uraninite > coffinite ≫ brannerite > betafite. The betafite showed minimal recovery rate of U which was less than 5% in a series tests. Hence, the authors suggested that the betafite ore should be a viable future host for long term storage for nuclear waste forms. McMaster investigated the influence of reaction time, reaction temperature, H2SO4 concentration, oxidant concentration, redox potential, and lixiviant on the leaching behavior of U for a synthetic pyrochlore group betafite [12]. The extent of U leaching in majority of the experiments was less than 2% and the maximum leaching rate of U was less than 10%. McMaster et al. investigated the leaching efficiency of three natural betafite samples from Ambatofotsy Madagascar, Miarinarivo Madagascar, and Silver Crater Mine, Canada [13]. The results showed that under the conditions, H2SO4 concentration of 5 g·L−1, Fe concentration of 3 g·L−1, Fe3+/Fe2+ ratio of 9:1, reaction temperature of 368 K, and reaction time of 6 h, the leaching rates of U were 38.03, 39.28, and 9.14% for the three natural betafite samples. Nettleton accomplished the practically complete extraction of U from the natural betafite under the conditions, H2SO4 concentration of 57.1 g·L−1, Fe3+ concentration of 36.7 g·L−1, reaction temperature of 362 K, and reaction time of 48 h, or alternative conditions, H2SO4 concentration of 214.5 g·L−1, Fe3+ concentration of 2 g·L−1, reaction temperature of 362 K, and reaction time of 48 h [14]. Although the leaching efficiency of U was fairly high, the reaction time of 48 h was too long to reduce the production efficiency. The kinetics investigation confirmed that the leaching process was specifically controlled by U diffusion through an inert product layer formed on the surface of the dissolving particles.

In conclusion, the abovementioned studies dramatically verified the highly refractory nature of the betafite minerals, and the considerably lower leaching rate of U had been observed, which demonstrated that the natural betafite ores could hardly be financially exploited via conventional process flow sheets. On the other hand, the concomitant valuable elements in betafite ores were barely simultaneously extracted in previous investigations. Therefore, it is necessary to investigate a novel technique for efficiently extracting U and concomitant valuable elements from the natural betafite ores, aiming to promote the natural betafite ores to become an economic source for U in the future.

In this work, the simultaneous recovery of U and niobium (Nb) from a low-grade natural betafite ores was systematically investigated. First, the sulfatizing roasting was employed to alter the ore properties, and the parameters that affected the roasting process over a range of roasting temperature, S/O ratio, and roasting time were studied. Based on the roasting parameters, the effect of the amount of sulfuric acid concentration, liquid–solid ratio, leaching temperature, and leaching time were investigated in detail to determine the optimum values for leaching tests.

2 Experimental methods

2.1 Materials

The representative samples of the ores were derived from Huayangchuan deposit located in the Shaanxi Province of China. The ore was crushed by a jaw crusher and screened. Then, the samples with particle size of 0.3–3 mm were concentrated by a 250 mm gravity-fed heavy medium cyclone. The resulting concentrates were further pulverized to −0.074 mm for the following experiments using a vibration mill.

2.2 Roasting experiments

Before leaching process, betafite sample was heated in a thermostatic drying oven with concentrated sulfuric acid in order to alter the characteristics of betafite ores. In each test, 50 g sample was weighed and placed in a 200 mL porcelain crucible, then 10 mL of water and a certain amount of sulfuric acid were added, and the mixture need to be thoroughly stirred. Next the loaded crucible was transferred to a thermostatic drying oven for roasting in air at a set temperature for a certain period of time. After the reaction duration, the roasted ore was cooled down to room temperature, and weighed for the leaching experiments.

The influences of various process parameters, such as the amount of sulfuric acid, roasting temperature, and roasting time were investigated in order to obtain the optimum roasting conditions. S/O (w/w) ratio was used to express the ratio of sulfuric acid dosage to ore weight and the values were selected as 0.2, 0.4, 0.6, 0.8, and 1.0. The effect of roasting temperature was analyzed at varying temperatures of 423, 453, 483, 513, and 543 K, while the roasting time was 30, 60, 90, 120, and 180 min.

2.3 Leaching experiments

A predetermined volume of the sulfuric acid solution was charged to a conical flask and heated to a desired temperature while being magnetically stirred at a specific stirring rate. Then, a measured amount of the aforementioned roasting sample was added to the flask and the reaction time was initiated. After the required time, the obtained ore slurry was separated from the leaching solution by vacuum filtration and washed with distilled water. Next the residues were dried at 378 K in an oven to a constant mass. The leaching experiments were carried out by varying acid concentrations (1, 1.5, 2, 2.5, and 3 mol·L−1), liquid–solid ratios (2, 3, 4, and 5 v/w), leaching temperatures (303, 313, 323, 333, 343, and 353 K), and leaching time (30, 60, 90, and 120 min).

The leaching rate (η) was calculated using equation (1) as follows:

(1) η = ( 1 − W t × R t W × R ) × 100 % ,

where η is the leaching rate of metal (%); W t and W refer to the mass of leaching residue and the feed, respectively (g); R t and R represent the grade of metal in leaching residue and feed, respectively (wt%).

2.4 Analysis

The chemical composition of the raw ore, the roasting sample, and the leaching residue was measured by using inductively coupled plasma-atomic emission spectroscopy (Intrepid II XSP, Thermo Electron, USA), while the X ray diffraction (XRD) analysis were performed using an X-ray diffraction spectrometer (SmartLab, Rigaku, Japan). The EPMA analysis was conducted using EPMA-1720 (Shimadzu, Japan) with a beam current of 10 nA and accelerating voltage of 15 kV.

3 Results and discussion

3.1 Characteristics of ore sample

The elemental analysis of the major elements for the ore sample is presented in Table 1. It can be seen that the amounts of U and Nb are 0.275 and 0.271%, respectively, which confirms that the mineral is a low-grade U ore. Apart from the valuable elements, the betafite ores also contain Si, Al, Ca, K, Na, Fe, and S in appreciable quantities. It is worth mentioning that there exist abundant iron contents in the ores, in which the amounts of Fe2+ and Fe3+ are 1.61 and 1.64%, respectively. Fe3+ ions can act as chemical oxidant in leaching process to provide the oxidative conditions required for the desired dissolution reaction and improve the leaching rate of U.

Table 1

Chemical analysis of the ore sample (wt%)

U Nb Pb Ag Fe Ti Ba
0.275 0.271 3.57 0.338 3.25 0.228 1.05
K Na Ca Mg Al Si S
3.01 0.80 5.89 0.46 3.29 21.7 2.24

XRD technique was applied to examine the mineralogical composition of the sample, and the XRD patterns are shown in Figure 1, which revealed that the main phases of the ore sample were quartz, barite, albite, microcline, and zeolite. A weak characteristic peak was observed at 30° corresponding to the presence of betafite phase, which was consistent with the lower content of U and Nb in the ore sample.

Figure 1 XRD patterns of raw ore.
Figure 1

XRD patterns of raw ore.

The ore sample was mapped by EPMA to examine the textures of the betafite phase and the back scattered electron images over the betafite phase areas are shown in Figure 2. It can be seen that the betafite phase, which was identified as the principal economic mineral constituent, appeared as granular crystalline form. The chemical compositions associated with the betafite phase shown in Table 2 revealed that its main compositions were UO2 31.02%, Nb2O5 30.28%, CaO 14.06%, and TiO2 17.86%.

Figure 2 EPMA spectrum of betafite phase.
Figure 2

EPMA spectrum of betafite phase.

Table 2

Chemical compositions of the betafite phase

Elements PbO2 CaO Nb2O5 UO2 TiO2 ThO2 Fe2O3
Contents (%) 0.39 14.06 30.28 31.02 17.86 0.06 0.11

3.2 Sulfatizing roasting process

Based on previous studies, the complex structure of the betafite ores results in the difficulty to extract valuable elements from the ores in the traditional techniques. On the other hand, U occurs in most ores in either the reduced U4+ or oxidized U6+ valence state. It is well known that U4+ is insoluble in acidic sulfate solution, yet its solubility can be prominently enhanced by oxidizing U4+ to U6+ state. In order to prominently improve the leaching behavior of valuable elements from the low-grade betafite ores, the mineral structure must be destroyed and U4+ need to be oxidized to U6+. Hence, sulfatizing roasting process is used to exploit the low-grade betafite ores, and its reaction mechanisms for main elements in the betafite phase are illustrated using the following equations:

(2) CaO + H 2 SO 4 = CaSO 4 + H 2 O ,

(3) 2 UO 2 + 2 H 2 SO 4 + O 2 = 2 UO 2 SO 4 + 2 H 2 O ,

(4) Nb 2 O 5 + H 2 SO 4 = Nb 2 O 4 SO 4 + H 2 O .

In the sulfatizing roasting process, U and Nb can be converted to soluble sulfate form representing as equations (3) and (4), while Ca can also react with H2SO4 according to equation (2) and form CaSO4. In order to in depth elaborate the mechanisms of the roasting process, the thermodynamic properties of the reactions are conducted as essential. As Nb2O4SO4 is an unstable compound which is liable to hydrolysis, there is lack of sufficient information with the thermodynamic parameters of Nb2O4SO4. Hence, the thermodynamic properties of equation (4) is not calculated.

The variations in the standard Gibbs free energy for equations (2) and (3) are shown in Figure 3 within the temperature range of 423–543 K. The results indicated that all values of the Gibbs free energy were negative within the considered temperature range which suggested that both the reactions occurred spontaneously in the sulfatizing roasting process. For the valuable element U, the sulfatizing roasting in air leads to an oxidation of U4+ into U6+, which is easy to dissolve in sulfuric acid solution.

Figure 3 Variations in the standard Gibbs free energy for equations (2) and (3).
Figure 3

Variations in the standard Gibbs free energy for equations (2) and (3).

3.2.1 Effect of roasting temperature

The roasting temperature plays an important role in the sulfatizing roasting process, and the influence of temperature on U and Nb recoveries was investigated at 423, 453, 483, 513, and 543 K. The U and Nb contents in each temperature is presented in Figure 4 under the following conditions: S/O rate of 0.8, roasting time of 1 h, sulfuric acid concentration of 2 mol·L−1, liquid–solid ratio of 4:1, leaching temperature of 323 K, and leaching time of 60 min. It can be seen that an increase in the roasting temperature from 423 to 513 K apparently accelerated the transformation of U and Nb to water soluble compounds and increased their leaching rates. Also the maximum values of leaching rates for 94.90% U and 73.51% Nb were obtained at temperature 513 K. In comparison, when the ores were not subjected to the sulfatizing roasting process, the leaching rates of U and Nb were merely 10.92 and 2.13%, respectively, which explicitly manifested that the betafite ores was highly stable and virtually inert under the same experimental conditions applied.

Figure 4 Effect of roasting temperature on the leaching rates of U and Nb.
Figure 4

Effect of roasting temperature on the leaching rates of U and Nb.

The refractory nature of the betafite ores inhibited the occurrence of the leaching reaction and hence only surface oxidized U and Nb were leached, which resulted in the comparative lower leaching rate of the valuable elements. Through the sulfatizing roasting process, the crystal structure of the betafite ores was completely destroyed, which was confirmed by the following XRD analysis. Therefore, the valuable elements locking in the inner structure of the ores were exposed to the leaching solution, thus obtaining considerable high leaching rates of U and Nb.

With further increase in the roasting temperature to 543 K, the leaching rates of both U and Nb slightly decreased. This fact may be explained as due to the mixture becoming more viscous due to the decomposition and volatilization of roasting agent at higher temperature, which adversely affected the roasting reaction between the ore and the H2SO4 agent. Therefore, the suitable roasting temperature was determined to be 513 K.

X ray diffraction analysis was conducted on all roasting samples after being subjected to sulfatizing roasting in the temperature range of 423–543 K and the XRD patterns are presented in Figure 5. Compared to the raw ore, the absence of the characteristic peak in 30° implied that the betafite phase had been decomposed owing to the valuable elements U and Nb being preferentially transformed to their corresponding sulfates as equations (3) and (4). Instead, new diffraction lines in 12° and 26° were clearly observed, which matched the characteristic peaks for gypsum phase and anhydrite phase, respectively. These peaks became sharper and more intense in the range of 423–483 K. Upon further heating to 513 K, the gypsum phase gradually converted to anhydrite phase owing to the evaporation of its crystal water. With additional heating to 543 K, the sharper diffraction lines for anhydrite phase and the lower diffraction lines for gypsum phase indicated that the conversion was continuous. On the other hand, the main phase of the roasting samples was quartz phase below the roasting temperature of 483 K, while the diffraction lines matching microcline phase became gradually intense with the increase in the roasting temperature. At 543 K, the crystal structure of the roasting samples had undergone significant alteration and the main phase converted to the microcline phase.

Figure 5 XRD patterns of all roasting samples.
Figure 5

XRD patterns of all roasting samples.

It is worth noting that the Gibbs free energy increased from −88.26 to −81.74 kJ·mol−1 for equation (3) accompanying with the increase in the temperature from 423 to 543 K, which was in conflict with the variation in the leaching rate for U. This phenomenon demonstrated that the higher recoveries of U and Nb during roasting process were mainly attributed to the transformation of the crystal structure for the minerals.

3.2.2 Effect of the amount of sulfuric acid

Sulfuric acid was used as roasting agent for generating water soluble sulfate compounds of the valuable elements, hence the effect of H2SO4 mass/ore mass ratio was studied at five different ratios: 0.2, 0.4, 0.6, 0.8, and 1.0. Figure 3 shows the results regarding the effect of S/O ratio variation on U and Nb recoveries under the following conditions: roasting temperature of 513 K, roasting time of 60 min, sulfuric acid concentration of 2 mol·L−1, liquid–solid ratio pf 4:1, leaching temperature of 323 K, and leaching time of 60 min.

As can be seen from Figure 6, the leaching rates of U and Nb dramatically increased in the range of 0.2–0.8 for the S/O ratio, whereas slightly slowed down with further increase in the S/O ratio. The higher S/O ratio increases its availability of H2SO4 for the desired roasting reaction, thus facilitating the U and Nb transformation towards the desired water-soluble species. Hence, the sufficient S/O ratio must be secured to obtain high recoveries of U and Nb during roasting. Nevertheless, the higher S/O ratio renders the mixture more viscous, thus complicating the following separation process. Considering the cost reasons and the viscosity issues, a further increase in S/O ratio should be avoided. Finally, the optimal S/O ratio was selected as 0.8, at which the leaching rates of U and Nb were 94.72 and 70.24%, respectively.

Figure 6 Effect of the amount of sulfuric acid on the leaching rates of U and Nb.
Figure 6

Effect of the amount of sulfuric acid on the leaching rates of U and Nb.

3.2.3 Effect of roasting time

The effect of varying roasting time on the leaching rates of U and Nb was studied in the range of 30–180 min under the following conditions: S/O rate of 0.8, roasting temperature of 513 K, sulfuric acid concentration of 2 mol·L−1, liquid–solid ratio of 4:1, leaching temperature of 323 K, and leaching time of 60 min, and the corresponding results are shown in Figure 7. The results showed that both U and Nb recoveries increased with the increase in the roasting time, which may be explained by the fact that the longer the roasting time, the deeper the degree of the reactions between the ore and the H2SO4 agent. At 120 min of the roasting time, 94.90% of U and 73.51% of Nb were leached out. After this period, the U and Nb recovery curves established a plateau, which implied that less valuable elements can be extracted with longer roasting time. According to the results, the optimal roasting time can be determined to be 120 min.

Figure 7 Effect of roasting time on the leaching rates of U and Nb.
Figure 7

Effect of roasting time on the leaching rates of U and Nb.

3.3 Leaching process

Based on the roasting experiments, the optimal process parameters of sulfatizing roasting were determined as following: S/O ratio of 0.8, roasting temperature of 513 K, and roasting time of 120 min. Under these optimal conditions, the effect of several parameters on the leaching rates of U and Nb in the leaching process was investigated in detail.

3.3.1 Effect of acid concentration

The influence of sulfuric acid concentration on U and Nb recoveries was investigated in the range of 1–3 mol·L−1 under the following conditions: liquid–solid ratio of 4:1, leaching temperature of 323 K, and leaching time of 60 min. The results of this experimental trial are presented in Figure 8.

Figure 8 Effect of sulfuric acid concentration on the leaching rates of U and Nb.
Figure 8

Effect of sulfuric acid concentration on the leaching rates of U and Nb.

It can be seen that the leaching rate of U varied between 93.55 and 94.90% in the range of sulfuric acid of concentration ranging from 1 to 3 mol·L−1, which indicated that the leaching behavior of U was not evidently impacted by the acid concentration. In comparison, the leaching rate of Nb significantly increased from 41.29 to 82.73% with the increase in the acid concentration from 1 to 2.5 mol·L−1, while it moderately increased to 84.39% with further increase in the acid concentration to 3 mol·L−1. It could be observed that the recovery of U was always higher than Nb during all the experiments, which was most likely due to the hydrolysis properties of the Nb tetroxysulfate compound. According to the results and analysis, the optimal sulfuric acid concentration can be determined to be 2.5 mol·L−1.

3.3.2 Effect of oxidizing agent

Table 3 compares the leaching rates of U and Nb for different oxidants (NaClO3, KMnO4, and H2O2) under the following conditions: sulfuric acid concentration of 2.5 mol·L−1, liquid–solid ratio of 4:1, leaching temperature of 323 K, and leaching time of 60 min.

Table 3

Effect of oxidizing agents (wt%) on the leaching rates of U and Nb

Oxidizing agent Amount of oxidant (%) U leaching rate (%) Nb leaching rate (%)
Blank 0 94.72 86.95
NaClO3 2 94.67 86.90
KMnO4 2 95.85 88.27
H2O2 2 94.81 87.04

The amount of added oxidants was 2% of total mass compared to the raw ores. The data from Table 3 showed that the leaching rates of U and Nb with the addition of oxidants were close to that measured without any additives, which clearly revealed that the addition of oxidants rarely benefited the leaching behavior of U and Nb, thus meaning that most U4+ had been oxidized in the sulfatizing roasting process. Furthermore, 1.6% Fe3+ existed in the raw ore, which can meet the oxidation conditions required for the conversion from U4+ to UO2 2+ according to equation (5). Therefore, it is unnecessary to add additional oxidants to the leaching tests.

(5) U 4 + + 2 Fe 3 + + H 2 SO 4 + 2 H 2 O = UO 2 SO 4 + 2 Fe 2 + + 6 H + .

3.3.3 Effect of liquid–solid ratio

The effect of the liquid–solid ratio on U and Nb recoveries was investigated at 2, 3, 4, and 5 v/w under the following conditions: sulfuric acid concentration of 2.5 mol·L−1, leaching temperature of 323 K, and leaching time of 60 min.

The results from Figure 9 shows that varying the liquid–solid ratio had no significant effect on U and Nb leaching. The only observable difference was that the leaching rate of Nb slightly decreased in higher liquid–solid ratio. A reasonable explanation of this phenomenon is the hydrolysis of Nb tetroxysulfate described by the reaction (6).

(6) Nb 2 O 4 SO 4 + 6 H 2 O = 2 Nb(OH) 5 + H 2 SO 4 .

Figure 9 Effect of liquid–solid ratio on the leaching rates of U and Nb.
Figure 9

Effect of liquid–solid ratio on the leaching rates of U and Nb.

It can be seen that when the amount of H2O increases, the reaction tends to switch to the right side to generate Nb(OH)5, which is difficult to dissolve in sulfuric acid solution. As a result, the suitable liquid–solid ratio was determined to be 2:1.

3.3.4 Effect of leaching temperature

The influence of the leaching temperature on U and Nb recoveries in the range of 303–353 K was conducted under the following conditions: sulfuric acid concentration of 2.5 mol·L−1, liquid–solid ratio of 2:1, and leaching time of 60 min. As shown in Figure 10, the leaching rate of U increased marginally for leaching temperature in the range of 303–353 K. In comparison, the maximum value of leaching rate achieved for Nb was 86.95% at 313 K, whereas it apparently declined beyond this point.

Figure 10 Effect of leaching temperature on the leaching rates of U and Nb.
Figure 10

Effect of leaching temperature on the leaching rates of U and Nb.

The leaching curves of leaching temperature had profiles similar to those observed in the influence of liquid–solid ratio tests. This phenomenon was most probably due to causes explained previously for the hydrolysis nature of Nb tetroxysulfate. Based on the test results, the optimal leaching temperature was determined to be 313 K, at which the leaching rates of U and Nb were 94.72 and 86.95%, respectively.

3.3.5 Effect of leaching time

The effect of leaching time on U and Nb recoveries was studied in the range of 30–120 min under the following conditions: acid concentration of 2.5 mol·L−1, liquid–solid ratio of 2:1, and leaching temperature of 313 K. Results shown in Figure 11 indicated that the amount of U leached varied between 94.12 and 94.72%, while the amount of Nb leached varied between 82.93 and 86.95%, which suggested that there was no significant effect on the amount of U and Nb leached. Considering the production efficiency, the optimal leaching time was adopted as 60 min.

Figure 11 Effect of leaching time on the leaching rates of U and Nb.
Figure 11

Effect of leaching time on the leaching rates of U and Nb.

3.4 Verification tests

To verify the obtained process parameters of the sulfatizing roasting coupled to sulfuric acid leaching, three validating tests were carried out under the following optimal conditions: roasting temperature of 513 K, S/O ratio of 0.8, roasting time of 120 min, sulfuric acid concentration of 2.5 mol·L−1, liquid–solid ratio of 2:1, leaching temperature of 313 K, and leaching time of 60 min without adding additives.

The results listed in Table 4 shows that over 95% U and 85% Nb were leached out in the optimal conditions, which undoubtedly confirmed that the novel technique was an advanced process to exploit the refractory natural betafite ores.

Table 4

Validating tests under optimal conditions

Item U leaching rate (%) Nb leaching rate (%)
Test 1 95.11 85.26
Test 2 95.24 85.56
Test 3 96.06 85.81

4 Conclusion

In this work, the novel technique, namely, sulfatizing roasting coupled to sulfuric acid leaching was adopted to extract U and Nb from a low-grade natural betafite ore, and the following conclusions could be drawn:

  1. In the sulfatizing roasting process, all parameters including roasting temperature, amount of sulfuric acid, and roasting time significantly affected the leaching behaviors of U and Nb. Compared to the extraction of U and Nb without roasting, the leaching rates of U and Nb with sulfatizing roasting was an order of magnitude higher under the same test conditions. The XRD analysis verified that the improvement in the U and Nb recoveries was attributed to the transformation of the crystal structure of betafite ores.

  2. In the leaching process, the parameters including the amount of sulfuric acid concentration, liquid–solid ratio, leaching temperature, and leaching time had no substantial impact on the leaching rates of U and Nb.

  3. The optimum process parameters of the novel technique were determined as follows: roasting temperature of 513 K, S/O ratio of 0.8, roasting time of 120 min, sulfuric acid concentration of 2.5 mol·L−1, liquid–solid ratio of 2:1, leaching temperature of 313 K, and leaching time of 60 min without adding oxidants. The validating tests showed that over 95% U and 85% Nb were leached out under the optimal conditions.

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Acknowledgements

The authors acknowledge the support of the Major Research Plan of the National Natural Science Foundation of China (No. 91962223), and the Geological Survey Evaluation Project of China Geological Survey (No. DD20190269).

  1. Funding information: The authors acknowledge the support of the Major Research Plan of the National Natural Science Foundation of China (No. 91962223), and the Geological Survey Evaluation Project of China Geological Survey (No. DD20190269).

  2. Author contributions: The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

  3. Conflict of interest: The authors declared that they have no conflict of interest, financial or otherwise, in this work.

  4. Data availability statement: The data used to support the findings of this study are available from the corresponding author upon request.

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Received: 2022-10-15
Revised: 2022-12-01
Accepted: 2022-12-02
Published Online: 2023-02-02

© 2023 the author(s), published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

Articles in the same Issue

  1. Research Articles
  2. First-principles investigation of phase stability and elastic properties of Laves phase TaCr2 by ruthenium alloying
  3. Improvement and prediction on high temperature melting characteristics of coal ash
  4. First-principles calculations to investigate the thermal response of the ZrC(1−x)Nx ceramics at extreme conditions
  5. Study on the cladding path during the solidification process of multi-layer cladding of large steel ingots
  6. Thermodynamic analysis of vanadium distribution behavior in blast furnaces and basic oxygen furnaces
  7. Comparison of data-driven prediction methods for comprehensive coke ratio of blast furnace
  8. Effect of different isothermal times on the microstructure and mechanical properties of high-strength rebar
  9. Analysis of the evolution law of oxide inclusions in U75V heavy rail steel during the LF–RH refining process
  10. Simultaneous extraction of uranium and niobium from a low-grade natural betafite ore
  11. Transfer and transformation mechanism of chromium in stainless steel slag in pedosphere
  12. Effect of tool traverse speed on joint line remnant and mechanical properties of friction stir welded 2195-T8 Al–Li alloy joints
  13. Technology and analysis of 08Cr9W3Co3VNbCuBN steel large diameter thick wall pipe welding process
  14. Influence of shielding gas on machining and wear aspects of AISI 310–AISI 2205 dissimilar stainless steel joints
  15. Effect of post-weld heat treatment on 6156 aluminum alloy joint formed by electron beam welding
  16. Ash melting behavior and mechanism of high-calcium bituminous coal in the process of blast furnace pulverized coal injection
  17. Effect of high temperature tempering on the phase composition and structure of steelmaking slag
  18. Numerical simulation of shrinkage porosity defect in billet continuous casting
  19. Influence of submerged entry nozzle on funnel mold surface velocity
  20. Effect of cold-rolling deformation and rare earth yttrium on microstructure and texture of oriented silicon steel
  21. Investigation of microstructure, machinability, and mechanical properties of new-generation hybrid lead-free brass alloys
  22. Soft sensor method of multimode BOF steelmaking endpoint carbon content and temperature based on vMF-WSAE dynamic deep learning
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  26. Study on diffusion kinetics of chromium and nickel electrochemical co-deposition in a NaCl–KCl–NaF–Cr2O3–NiO molten salt
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  38. Investigation of the microstructure and mechanical properties of Mg–Al–Zn alloy joints formed by different laser welding processes
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  40. Effect of P and Ti on the agglomeration behavior of Al2O3 inclusions in Fe–P–Ti alloys
  41. Cation-doping effects on the conductivities of the mayenite Ca12Al14O33
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  64. Topical Issue on Focus of Hot Deformation of Metaland High Entropy Alloys - Part I
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https://doi.org/10.1515/htmp-2022-0260
Keywords for this article
uranium; niobium; betafite; leaching; sulfatizing roasting
Creative Commons
BY 4.0

Articles in the same Issue

  1. Research Articles
  2. First-principles investigation of phase stability and elastic properties of Laves phase TaCr2 by ruthenium alloying
  3. Improvement and prediction on high temperature melting characteristics of coal ash
  4. First-principles calculations to investigate the thermal response of the ZrC(1−x)Nx ceramics at extreme conditions
  5. Study on the cladding path during the solidification process of multi-layer cladding of large steel ingots
  6. Thermodynamic analysis of vanadium distribution behavior in blast furnaces and basic oxygen furnaces
  7. Comparison of data-driven prediction methods for comprehensive coke ratio of blast furnace
  8. Effect of different isothermal times on the microstructure and mechanical properties of high-strength rebar
  9. Analysis of the evolution law of oxide inclusions in U75V heavy rail steel during the LF–RH refining process
  10. Simultaneous extraction of uranium and niobium from a low-grade natural betafite ore
  11. Transfer and transformation mechanism of chromium in stainless steel slag in pedosphere
  12. Effect of tool traverse speed on joint line remnant and mechanical properties of friction stir welded 2195-T8 Al–Li alloy joints
  13. Technology and analysis of 08Cr9W3Co3VNbCuBN steel large diameter thick wall pipe welding process
  14. Influence of shielding gas on machining and wear aspects of AISI 310–AISI 2205 dissimilar stainless steel joints
  15. Effect of post-weld heat treatment on 6156 aluminum alloy joint formed by electron beam welding
  16. Ash melting behavior and mechanism of high-calcium bituminous coal in the process of blast furnace pulverized coal injection
  17. Effect of high temperature tempering on the phase composition and structure of steelmaking slag
  18. Numerical simulation of shrinkage porosity defect in billet continuous casting
  19. Influence of submerged entry nozzle on funnel mold surface velocity
  20. Effect of cold-rolling deformation and rare earth yttrium on microstructure and texture of oriented silicon steel
  21. Investigation of microstructure, machinability, and mechanical properties of new-generation hybrid lead-free brass alloys
  22. Soft sensor method of multimode BOF steelmaking endpoint carbon content and temperature based on vMF-WSAE dynamic deep learning
  23. Mechanical properties and nugget evolution in resistance spot welding of Zn–Al–Mg galvanized DC51D steel
  24. Research on the behaviour and mechanism of void welding based on multiple scales
  25. Preparation of CaO–SiO2–Al2O3 inorganic fibers from melting-separated red mud
  26. Study on diffusion kinetics of chromium and nickel electrochemical co-deposition in a NaCl–KCl–NaF–Cr2O3–NiO molten salt
  27. Enhancing the efficiency of polytetrafluoroethylene-modified silica hydrosols coated solar panels by using artificial neural network and response surface methodology
  28. High-temperature corrosion behaviours of nickel–iron-based alloys with different molybdenum and tungsten contents in a coal ash/flue gas environment
  29. Characteristics and purification of Himalayan salt by high temperature melting
  30. Temperature uniformity optimization with power-frequency coordinated variation in multi-source microwave based on sequential quadratic programming
  31. A novel method for CO2 injection direct smelting vanadium steel: Dephosphorization and vanadium retention
  32. A study of the void surface healing mechanism in 316LN steel
  33. Effect of chemical composition and heat treatment on intergranular corrosion and strength of AlMgSiCu alloys
  34. Soft sensor method for endpoint carbon content and temperature of BOF based on multi-cluster dynamic adaptive selection ensemble learning
  35. Evaluating thermal properties and activation energy of phthalonitrile using sulfur-containing curing agents
  36. Investigation of the liquidus temperature calculation method for medium manganese steel
  37. High-temperature corrosion model of Incoloy 800H alloy connected with Ni-201 in MgCl2–KCl heat transfer fluid
  38. Investigation of the microstructure and mechanical properties of Mg–Al–Zn alloy joints formed by different laser welding processes
  39. Effect of refining slag compositions on its melting property and desulphurization
  40. Effect of P and Ti on the agglomeration behavior of Al2O3 inclusions in Fe–P–Ti alloys
  41. Cation-doping effects on the conductivities of the mayenite Ca12Al14O33
  42. Modification of Al2O3 inclusions in SWRH82B steel by La/Y rare-earth element treatment
  43. Possibility of metallic cobalt formation in the oxide scale during high-temperature oxidation of Co-27Cr-6Mo alloy in air
  44. Multi-source microwave heating temperature uniformity study based on adaptive dynamic programming
  45. Round-robin measurement of surface tension of high-temperature liquid platinum free of oxygen adsorption by oscillating droplet method using levitation techniques
  46. High-temperature production of AlN in Mg alloys with ammonia gas
  47. Review Article
  48. Advances in ultrasonic welding of lightweight alloys: A review
  49. Topical Issue on High-temperature Phase Change Materials for Energy Storage
  50. Compositional and thermophysical study of Al–Si- and Zn–Al–Mg-based eutectic alloys for latent heat storage
  51. Corrosion behavior of a Co−Cr−Mo−Si alloy in pure Al and Al−Si melt
  52. Al–Si–Fe alloy-based phase change material for high-temperature thermal energy storage
  53. Density and surface tension measurements of molten Al–Si based alloys
  54. Graphite crucible interaction with Fe–Si–B phase change material in pilot-scale experiments
  55. Topical Issue on Nuclear Energy Application Materials
  56. Dry synthesis of brannerite (UTi2O6) by mechanochemical treatment
  57. Special Issue on Polymer and Composite Materials (PCM) and Graphene and Novel Nanomaterials - Part I
  58. Heat management of LED-based Cu2O deposits on the optimal structure of heat sink
  59. Special Issue on Recent Developments in 3D Printed Carbon Materials - Part I
  60. Porous metal foam flow field and heat evaluation in PEMFC: A review
  61. Special Issue on Advancements in Solar Energy Technologies and Systems
  62. Research on electric energy measurement system based on intelligent sensor data in artificial intelligence environment
  63. Study of photovoltaic integrated prefabricated components for assembled buildings based on sensing technology supported by solar energy
  64. Topical Issue on Focus of Hot Deformation of Metaland High Entropy Alloys - Part I
  65. Performance optimization and investigation of metal-cored filler wires for high-strength steel during gas metal arc welding
  66. Three-dimensional transient heat transfer analysis of micro-plasma arc welding process using volumetric heat source models
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