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Carbothermal reduction of red mud for iron extraction and sodium removal

  • Huaixuan Feng , Xue-feng She EMAIL logo , Xiao-min You , Guang-qing Zhang , Jing-song Wang and Qing-guo Xue
Published/Copyright: June 28, 2022
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High Temperature Materials and Processes
From the journal High Temperature Materials and Processes Volume 41 Issue 1

Abstract

In this work, the technology of carbothermic reduction was used to extract iron and remove sodium from red mud. The effect of various parameters like reduction time, temperature, and basicity on melting separation and de-alkalization was studied. At the optimum reduction temperature of 1,450°C, the basicity of 1.5, and reduction time of 12 min, the metallization rate and sodium removal reach 96.63 and 90.62%, respectively. Melting and separating conditions gradually improve with the temperature increasing from 1,350 to 1,450°C. At high basicity (R = 2), the condition of melting and separation is poor due to a large amount of Ca2Al2SiO7 produced, which has a high melting point. Subsequently, in order to explore the aggregation state of iron ions under different basicities, the microstructure of pellets was observed by scanning electron microscopy. It was found that when the basicity is 1.5, the aggregation degree of iron particles significantly increases. X-ray diffraction (XRD) analyses of the reduced pellets indicated that at different basicities, the final phase composition of reduced pellets is mainly Ca2Al2SiO7, which is the basic material for preparing cement materials and glass ceramics. Thus, the carbothermic-reduction method is a sustainable process for dealing with the Bayer bauxite residue.

Keywords: red mud; de-alkalization; carbothermic reduction; valuable element recycling; iron particle

1 Introduction

The Bayer process is one of the important methods or approaches to producing aluminum. It is reported that more than 90% of alumina is produced via the Bayer process. Thus, the Bayer bauxite residue accounts for a considerable percentage of the by-products of alumina extraction. For each ton of alumina produced, 1.0–1.5 tonnes of Bayer red mud is produced from different sources and processing parameters [1,2]. At present, it is reported that more than 2.7 billion tonnes of red mud have been accumulated in the world [3,4,5,6]. It contains aluminum, iron, and other valuable metals. Unfortunately, the average utilization factor of global red mud is only 15%, and for China it is 4% [7]. For the large-scale solution of the problem of red mud, the idea of extracting valuable metals first, and then using the residue in an integral unit is encouraged to completely recover or reuse all valuable components in red mud. However, on the one hand, the direct use of red mud for ironmaking has low economic benefits. On the other hand, the high content of alkalinity hinders the further use of red mud. Sintered brick and other wall materials produced from red mud generate alkali efflorescence that results in size expansion, cracking, and disintegration, thus decreasing the service life of buildings [8]. Its heavy metals and a certain amount of radioactive material poses a great challenge to the ecological environment. Moreover, red mud takes a large number of expenditures on stacking yard construction, maintenance, and management [9,10].

Thus, it is an urgent target to comprehensively use red mud and find a possible way for a nonhazardous treatment. As the red mud characters differ, different aspects were considered including valued metals recovered and de-alkalization for the materials of cement. Wang and Sun [11], Jiang et al. [12], and Yu et al. [13] reported that nickel and iron in red mud can be effectively recovered by direct reduction and magnetic separation. Alkaline metal salts were added, which enhanced the reduction of laterite ores, and the recovery rates of iron and nickel were 93.77 and 95.25 wt%, respectively. Jayasankar and Ray [14] used thermal plasma technology to deal with red mud waste fines for recovering pig iron. They studied various process parameters like reductant, fluxes, and smelting time on the effect of iron recovery. Wang and Zhang [15,16] used the calcification-carbonization process to recover alumina and alkali from red mud. The process contained three steps: calcification transformation, carbonization transformation, and Al(OH)3 leaching. They obtained the final residue, and Na2O contents of the alumina below 0.3 and 46.5% were extracted, which can be used for cement material. Although some progress has been achieved, these methods are complicated and a great amount of Al(OH)3 was consumed.

In this work, the carbothermic reduction of Bayer red mud was performed to recover valued elements and de-alkalization. At enough content of carbon, iron oxide in red mud can be reduced to metallic iron, Na2O can be reduced to sodium vapor, and the residue can be transformed to gehlenite. First, the effect of temperature and CaO content on pellet melting separation was investigated. Then, the metallization rate and sodium removal rate of pellets before and after reduction were obtained by using X-ray fluorescence (XRF). X-ray mapping via scanning electron microscopy (SEM) for elements Fe and Na in the reduction process was used to study the state of aggregation. The residual phase composition was established by X-ray diffraction (XRD). The main objectives of this research are to investigate the behavior of red mud in the carbothermic reduction and melting separation process and to remove sodium.

2 Experiment materials and methods

2.1 Raw materials

The red mud used in this experiment came from a steel plant in China. The XRF analysis results of red mud in this work are shown in Table 1. As can be seen, the Al2O3 and Fe2O3 contents were relatively high, 20.28 and 33.21%, respectively, which indicated that the red mud was the residue formed in the Bayer process [17]. It is worth noting that the content of Na2O was 8.63%. XRD analysis was used to determine the phases, and the results are shown in Figure 1. The main phases in the red mud were hematite (Fe2O3), goethite (FeOOH), sodalite (1.06Na2OAl2O31.60SiO21.60H2O), gibbsite (Al(OH)3), quartz (SiO2), and the iron element in the red mud existed in the form of hematite and goethite. In addition, the particle size of red mud was tiny (0.088–0.25 mm), which was beneficial for the reduction treatment [18]. The scanning electron microscopy image of the red mud is also shown in Figure 2, revealing that the surface of red mud agglomerates was made of many small compact particles that were amorphous and irregular. Pulverized anthracite coal was used as a reductant. The chemical composition of the anthracite coal is listed in Table 2, which indicated that it was high in fixed carbon and relatively low in ash and sulfur.

Table 1

Chemical composition of the red mud (wt%)

Na2O Al2O3 SiO2 CaO TiO2 Fe2O3
8.63 20.28 16.66 3.84 3.92 33.21
Figure 1 XRD analysis of the Bayer red mud.
Figure 1

XRD analysis of the Bayer red mud.

Figure 2 Microstructure of the Bayer red mud.
Figure 2

Microstructure of the Bayer red mud.

Table 2

Chemical composition of anthracite (wt%)

Proximate analysis Ash analysis S P
FCd Vd Ad Mad SiO2 Al2O3 Fe2O3 CaO MgO
81.05 5.98 10.14 2.83 42.79 35.70 2.82 7.89 0.92 0.32 0.06

2.2 Experimental methods

Before being crushed and screened to <200 µm, the red mud and anthracite coal were dried in an oven at 105°C for 48 h. Then, these materials were fully mixed with CaO as shown in Table 3. Furthermore, the mixture was pressed at 20 kN for 2 min into ∼7.0 g cylindrical tablets of 15 mm diameter and 10 mm height for the reduction experiment [19].

Table 3

The main composition of carbon-bearing pellets under different conditions (wt%)

Red mud CaO Anthracite coal
T = 1,350°C 74.24 15.74 10.02
T = 1,400°C 74.24 15.74 10.02
T = 1,450°C 74.24 15.74 10.02
R = 1.0 79.11 10.21 10.68
R = 1.5 74.24 15.74 10.02
R = 2.0 69.93 20.63 9.44

Basicity, time, and temperature were considered in the present work. The basicities of the pellets were set as 1.0, 1.5, and 2.0, and the temperature of the experiment was varied in the range of 1,350–1,450°C (50°C increments). First, the effect of temperature on melting and separating the pellet was investigated with the basicity fixed at 1.5. The amounts of anthracite coal in the current study were 1.5 times larger than the stoichiometric needed to ensure the complete reduction of iron oxides. The muffle furnace was first preheated to a temperature of 1,350°C; then, the carbon-bearing pellets were put into the furnace with the holding time set to 2–12 min. After the reaction, the pellets were taken from the furnace and cooled to ambient temperature under an argon atmosphere. Then, the preheating temperatures were set at 1,400 and 1,450°C, and the experiment process was repeated as before.

Second, in order to explore the influence of basicity on the experiment, different alkalinities were set up for experimental analysis. The value of basicity in the experiment was obtained by calculating the mass ratio of calcium oxide and silicon dioxide. Since the mass of silica in the red mud was more than that of calcium oxide, calcium oxide was added to adjust the alkalinity to 1.0–2.0. To avoid the energy deficiency at low temperatures, the furnace temperature was set at 1,450°C. The basicity of the pellets in the experiment varies from 1.0 to 2.0. One of the reduced pellets was cut from the middle, and then were mounted in epoxy resin, polished, sprayed by the carbon film for the cross-sectional observation by SEM-EDS. Moreover, X-ray mapping was used to observe the distribution density variation of the element Na in different positions of the pellets with increasing reduction time. The other reduced pellet was ground for XRD analysis and chemical analysis.

The metallization rate ( η F e ) and sodium removal rate ( ε ) were adopted as evaluation indices of the process of carbothermal reduction.

The metallization rate of iron components ( η F e ) can be expressed as

(1) η Fe = M Fe / T Fe × 100 % ,

where M Fe is the metallic iron content in the reduced pellets and T Fe is the total iron content in reduced pellets.

The sodium removal rate of pellets can be calculated as

(2) ε = m 1 α − m 2 β m 1 α × 100 % ,

where m 1 is the initial mass of the pellet, g; m 2 is the mass of pellets after reduction, g; α is the content of Na2O in the initial pellets; and β is the content of Na2O in the pellets after reduction.

3 Results and discussion

3.1 Effect of temperature on the reduction and melting separation

One of the purposes of studying red mud was to recycle valued elements. In this study, carbothermal reduction at high temperatures was used for separating iron and slag. The morphology of pellets was discussed with respect to temperature first, as shown in Figure 3.

Figure 3 The melting and separation of red mud at different times and temperatures: (a) 1,350°C, (b) 1,400°C, and (c) 1,450°C.
Figure 3

The melting and separation of red mud at different times and temperatures: (a) 1,350°C, (b) 1,400°C, and (c) 1,450°C.

It was clearly seen that the morphology of the pellets was different from the temperature change.

When the temperature increased, the amount of carburizing gradually increased, and the melting point of iron decreased, which was easy to separate from the slag. At 1,350°C, the condition of melting separation was poor, and the slag and iron cannot be completely separated. With the temperature further increasing, the iron nugget and slag can separate well at 1,450°C. The iron element exists in the form of an iron bead, scattered on the edge of the pellet, and the diameter can grow up to 5 mm. At 1,450°C, the shape of pellets at 6 and 10 min were almost the same, indicating that the melting and separation were completed at 6 min. In addition, in order to study the metallization rate of the pellets after melting and separation, XRF was used to determine the content of Fe2+ and TFe. According to equation (1), the metallization rate ( ε ) was calculated and the results are shown in Figure 4.

Figure 4 Effect of temperature on the metallization rate of pellets.
Figure 4

Effect of temperature on the metallization rate of pellets.

Figure 4 shows that the temperature greatly influences the metallization rate. The metallization rate increased initially from 78.59 to 96.63% as the temperature increased from 1,350 to 1,450°C. Afterward, the metallization rate was basically unchanged when the reduction time reached 12 min. Thus, a temperature of 1,450°C was an advantage for the red mud reduction and melting separation.

In the smelting reduction separation process, the melting of reduced iron and slag were the decisive factors. The melting temperature of reduced iron was mainly related to carburization, while the melting of slag was mainly related to composition. Since the composition of slag had not changed, the temperature of reduced iron became the main factor that limited the melting and separation of the pellets. At 1,350°C, because of the low temperature and insufficient iron carburization, the iron element was difficult to melt, thus the slag and iron could not be completely separated. As the temperature increased, the carburizing process sped up, resulting in the melt of metallic iron. Under the high heating temperature, the fluidity of the slag and iron was improved, and the separation was more thorough. Due to the difference in density, the metallic iron sank downward while the slag moved upward. According to Wang et al. researched [20], in the initial stage of isothermal thermal reduction, the content of FeO in the slag was related to its surface tension, i.e., as the FeO content decreased, the surface tension of the slag gradually increased. Therefore, the slag could not gather on the upper part of the iron and would move to the side of the iron.

3.2 Effect of basicity on reduction and melting separation

In this section, different basicity on the influence of melting and separation were studied. Results were shown in Figure 5 with the basicity of the pellets set as 1.0, 1.5, and 2.0. It could be concluded that basicity has an important effect on the iron-slag melting separation of the pellets. As the basicity increases from 1.0 to 1.5, the separation effect of slag and iron was remarkable. Metal iron aggregated and grew to form iron beads. When the basicity was 1.5 and the reduction time was 4 min, the diameter of the metallic iron in the pellets could reach about 6.5 mm. When the reduction time was prolonged to 6 and 10 min, the pellet melting effect was basically the same, indicating that the melting was over at 6 min. While the basicity increased to 2.0, as the reduction time increased, a large number of fine iron particles gradually precipitate out, scattered on the surface of the slag. The condition of iron-slag melting separation of the pellet was poor. It may be due to the fact that the fluidity in the slag was poor, resulting in the decrease of the rate of mass transfer so that the iron produced by the reduction fails to accumulate.

Figure 5 The melting and separation of red mud at different times and basicities at a temperature of 1,450°C: (a) R = 1.0, (b) R = 1.5, and (c) R = 2.0.
Figure 5

The melting and separation of red mud at different times and basicities at a temperature of 1,450°C: (a) R = 1.0, (b) R = 1.5, and (c) R = 2.0.

It is well known that can play the role of network modifier in the slag [21,22,23]. [SiO4]-tetrahedral and [AlO4]-tetrahedral could be formed by SiO2 and Al2O3 in the molten slag, which was combined through the bridging oxygen (O0) [24,25]. With the increasing content of CaO, the availability of free oxygen ions ( O 2 − ) in the molten slag was increased. Then, O 2 − could react with O0 in the network structure to form nonbridging oxygen (O−), which simplified the structure of the melt. In this way, the viscosity of slags decreased and the fluidity was improved. The mass transfer conditions were improved, promoting the separation of iron and slag.

However, when the basicity of the pellet increased to 2.0, iron and slag could not separate well. It might be ascribed to the fact that a large amount of gehlenite was formed at the high content of CaO, which had a high melting point [26]. Thus, the mass transformation got worse when the basicity was 1.5.

Figure 6 shows the metallization rate under different basicities. The metallization rate of the reduced pellet with a basicity of 1.5 was higher than that at 1.0 and 2.0. Moreover, the metallization rate of the pellet with a basicity of 1.5 was 96.37% when the reduction time was 12 min, remaining stable for the rest of the time, indicating that the carbothermal reduction process was completed. Considering the melting separation condition and the metallization rate of the pellet synthetically, the optimal reduction temperature and basicity were 1,450°C and 1.5, respectively.

Figure 6 Effect of basicity on the metallization rate of pellet at 1,450°C.
Figure 6

Effect of basicity on the metallization rate of pellet at 1,450°C.

The iron mineral reduction of red mud included the reduction of iron oxides and the growth of metallic iron. Figure 5 shows that the iron oxide in the red mud could be reduced to metallic iron. Therefore, the main factor influencing the microstructure of the pellet was the grain size of metallic iron, which was the premise of the liberation of iron shot [26]. Thus, in this work, we approaced from a microscopic perspective of pellets under different basicities, which is shown in Figure 7.

Figure 7 Microstructure of reduced pellets of the red mud under different reduction conditions: (a and b) R = 1.0, (c and d) R = 1.5, and (e and f) R = 2.0.
Figure 7

Microstructure of reduced pellets of the red mud under different reduction conditions: (a and b) R = 1.0, (c and d) R = 1.5, and (e and f) R = 2.0.

It was clearly seen that at a basicity of 1.5, the growth of metallic iron particles (light white area) was enhanced significantly with the diameter size above 80 µm. At a basicity of 1.0 (Figure 7(a)), most metallic iron particles were isolated from each other, while there were some sheets that appeared as the basicity increased to 1.5 (Figure 7(c)). In addition, as shown in Figure 7(c) and (d), adjacent iron particles gradually aggregated and grew to form a sheet, which was consistent with the results of Fan and Ni [26]. However, when the basicity increased from 1.5 to 2.0, it was obvious that the iron particles evenly dispersed on the surface of the pellet without aggregation. small amounts of big particles was found at a basicity of 2.0, as shown in Figure 7(e). Thus, it was testified that due to an excessive formation of gehlenite, the mass transfer in the pellets got worse. Furthermore, comparing Figure 7(a), (c), and (e) with (b), (d), and (f), the metallic iron particles mainly assembled in the edge part around the pellets, and the center of the pellet was in disperses state.

3.3 Phase transformation of the pellet under different basicities and temperatures

The phase compositions of the slag after reduction under different basicities are shown in Figure 8. Figures 1 and 8 show that the peaks of hematite and goethite disappear and the peaks of Ca2Al2SiO7 and NaCaAlSi2O7 appear in the reduced pellets. The results indicate that the iron minerals in the original pellets were reduced and transformed into metallic iron. The peaks of sodalite, gibbsite, and quartz were not detected. Ca2Al2SiO7 was the main phase in the reduced pellets, which was one of the components of cement materials and glass-ceramics [27,28]. The composition of pellets under different basicities had not changed and there were two phases in the pellets. With the increase of the basicity from 1.0 to 1.5, the content of different phases increased, which might be the reason that CaO changed the mass transfer conditions in the slag thereby increasing the mass transfer rate in the slag. It was obvious that the content of Ca2Al2SiO7 was increased with the basicity increase from 1.0 to 2.0. As discussed above, a large amount of Ca2Al2SiO7 improved the melting point of the whole molten slag, resulting in the melting and separation getting worse, which was in accordance with the result of Figure 6.

Figure 8 The phase compositions of the slag after reduction under different basicities: (a) NaCaAlSi2O7; (b) Ca2Al2SiO7; and (c) CaTiO3.
Figure 8

The phase compositions of the slag after reduction under different basicities: (a) NaCaAlSi2O7; (b) Ca2Al2SiO7; and (c) CaTiO3.

Likewise, to investigate the relationship between the reduction process and temperature, XRD was used to study the phase transformation of the slag, and the results are shown in Figure 9. It is obvious that temperature had an important effect on the reduction of the pellets. When the temperature was increased to 1,200°C, diffraction peaks of hematite (Fe2O3) vanished, indicating that the reduction process of the pellet was complete. As suggested in the Ellingham diagram [29], there were three steps in the reduction of iron oxides: Fe2O3 → Fe3O4 → FeO → Fe. However, as the temperature gradually increased from 1,350 to 1,450°C, the peak of hematite (Fe2O3) did not appear in the XRD result, which was not consistent with the result of the metallization rate (Figure 4). This was due to the fact that during the reduction of the pellets, the iron grade in the slag gradually decreased, and thus the content of iron oxide was too small to be detected by XRD. In addition, it could be seen that the main components of slag at high temperatures are Ca2Al2SiO7 (C2AS) and a small part of NaCaAlSi2O7. With the increase of temperature, the sodium salt gradually decreased while the content of C2AS gradually increased. The detailed discussion is described in Section 3.4.

Figure 9 XRD pattern of the slag at different temperatures: (a) Fe2O3; (b) Ca2Al2SiO7; (c) NaCaAlSi2O7; (d) sodalite; (e) Al(OH)3; and (f) SiO2.
Figure 9

XRD pattern of the slag at different temperatures: (a) Fe2O3; (b) Ca2Al2SiO7; (c) NaCaAlSi2O7; (d) sodalite; (e) Al(OH)3; and (f) SiO2.

3.4 De-alkalization

The production of building materials (such as cement, brick, and road base material) with the bauxite residue was a direct, simple, economical, and quick way to consume a large amount of the substance [30,31]. However, the component of red mud that was used for cement was strictly controlled. If the alkali content of the cement was too high [32], an alkali-aggregation reaction would occur in the concrete, resulting in low strength and inadequate durability, which might cause serious project quality or safety issues and accidents [16]. Therefore, from the perspective of waste utilization, this section studied the removal efficiency of sodium from the red mud by carbothermal reduction.

As shown in Figure 10, the removal rate of alkali increased with the increase of temperature and alkalinity under different conditions. The temperature was more important than the basicity for sodium removal. At a fixed basicity, the temperature was increased by 100°C, and the alkali removal rate was increased from 49.29 to 90.62%. When the basicity was increased from 1.0 to 2.0, the change range of the alkali removal rate was relatively small (75.79–92.07%).

Figure 10 Effect of temperature and basicity on the alkali removal rate: (a) different basicities, T = 1,450°C and (b) different temperatures, R = 1.5.
Figure 10

Effect of temperature and basicity on the alkali removal rate: (a) different basicities, T = 1,450°C and (b) different temperatures, R = 1.5.

The reactions of sodium in red mud are shown in equations (3)–(5). Sodium oxide reacts with silica to form sodium silicate. It was more important than calcium oxide being used as an additive. Excess carbon reduced the sodium in sodium silicate and was released as sodium vapor. The calcium silicate produced in equation (4) reacted with the alumina in the red mud. These results basically corresponded to the XRD patterns. However, in Figures 8 and 9, a part of sodium existed as NaCaAlSi2O7because the Ca element in Ca2Al2SiO7 was replaced by the Na element to form sodalite, and thus sodium could not be completely removed [33]. Meanwhile, from the thermodynamics viewpoint, equation (5) is an endothermic reaction. As the temperature increased, the reaction proceeded in the direction of the positive reaction, thereby promoting the removal of sodium. The removal rate improved with an increase in basicity due to the improvement in the mass transfer. Therefore, the alkalinity content in the red mud could be reduced to a certain level, which provided a convenient condition for further utilization:

(3) Na 2 O + SiO 2 = Na 2 SiO 3 ,

(4) x C + x CaO + Na 2 SiO 3 = x CO ( g ) + 2 Na ( g ) + Ca x SiO 3 ,

(5) CaSiO 3 + Al 2 O 3 = Ca 2 Al 2 SiO 7 .

Furthermore, in order to investigate the initial position of sodium removal and the time the steady state was reached, X-ray mapping via SEM was used for the pellets (R = 1.5, T = 1,450°C) with the reduction time lasting for 2, 6 min, and 15 min. The center and right edge of the projectile were selected as the observation positions. The scanning results are illustrated in Figure 11, and the concentration of sodium elements measured in different regions is shown in Figure 12. The detailed operation for measuring the element content by the LA-ICP-MS system was given in the previous article.

Figure 11 X-ray mapping analysis via SEM of Na in the reduction process (R = 1.5, T = 1,450°C) (a and b) 2 min, (c and d) 6 min, (e and f) 15 min.
Figure 11

X-ray mapping analysis via SEM of Na in the reduction process (R = 1.5, T = 1,450°C) (a and b) 2 min, (c and d) 6 min, (e and f) 15 min.

Figure 12 Sodium content at different positions of the pellets (R = 1.5, T = 1,450°C).
Figure 12

Sodium content at different positions of the pellets (R = 1.5, T = 1,450°C).

As can be clearly seen from Figures 11 and 12, the concentration of sodium gradually decreased with the increase of the reduction time. At 2 min, there was no obvious change in the sodium concentration between the edge and center of the pellets. However, the concentration of sodium at the center of pellets was significantly lower than that at the edge as the reduction time increased to 6 min, showing a clear concentration gradient. It was speculated that the carbothermal reduction started at the center of the pellet, and the generated sodium vapor flowed out from the gap of the pellets, resulting in the difference in the removal rate at different positions. Furthermore, when the reduction time was increased to 15 min, they appeared almost the same distribution at low concentration, indicating that the reduction process of sodium had been completed and reached a steady state.

4 Conclusion

In this work, the carbothermic reduction was used to extract iron and remove alkali from the red mud. The effect of different parameters like reduction time, temperature, and basicity on melting, separation, and de-alkalization was studied, and some conclusions can be drawn as follows:

  1. At a basicity of 1.5 and temperature of 1,450°C, the melting and separation of slag iron in the red mud produced by the Bayer method was thorough, the metallization rate reached 96.63%, and the sodium removal rate reached 90.62%.

  2. At 1,450°C, the melting and separation condition gradually improved with increasing basicity from 1.0 to 1.5. However, when the basicity further increased to 2.0, the condition did not improve. Because high basicity results in a large amount of gehlenite, it causes an increase in the melting point of the system. Thus, the melting and separation were poor.

  3. The product after carbothermal reduction of the red mud is mainly Ca2Al2SiO7, which can be used as cement materials and glass-ceramics in the construction industry.

  4. The concentration of sodium at the center of pellets was significantly lower than that at the edge when the reduction time increased to 6 min, showing a clear concentration gradient.

Acknowledgements

This work was supported by the National Key Research and Development Program of China (2019YFC1905703), and the National Natural Science Foundation of China (No. 51874029), which is acknowledged.

  1. Funding information: This work was supported by the National Key Research and Development Program of China (2019YFC1905703), and the National Natural Science Foundation of China (No. 51874029).

  2. Author contributions: Jing-song Wang and Xue-feng She were engaged in research on the recycling of solid waste from iron and steel metallurgy.

  3. Conflict of interest: Authors state no conflict of interest.

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Received: 2021-06-29
Revised: 2021-09-27
Accepted: 2021-10-14
Published Online: 2022-06-28

© 2022 Huaixuan Feng et al., published by De Gruyter

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

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  2. Numerical and experimental research on solidification of T2 copper alloy during the twin-roll casting
  3. Discrete probability model-based method for recognition of multicomponent combustible gas explosion hazard sources
  4. Dephosphorization kinetics of high-P-containing reduced iron produced from oolitic hematite ore
  5. In-phase thermomechanical fatigue studies on P92 steel with different hold time
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  10. Single-source-precursor synthesis and characterization of SiAlC(O) ceramics from a hyperbranched polyaluminocarbosilane
  11. Carbothermal reduction of red mud for iron extraction and sodium removal
  12. Reduction swelling mechanism of hematite fluxed briquettes
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  14. Corrosion behavior of WC–Co coating by plasma transferred arc on EH40 steel in low-temperature
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https://doi.org/10.1515/htmp-2022-0005
Keywords for this article
red mud; de-alkalization; carbothermic reduction; valuable element recycling; iron particle
Creative Commons
BY 4.0

Articles in the same Issue

  1. Research Articles
  2. Numerical and experimental research on solidification of T2 copper alloy during the twin-roll casting
  3. Discrete probability model-based method for recognition of multicomponent combustible gas explosion hazard sources
  4. Dephosphorization kinetics of high-P-containing reduced iron produced from oolitic hematite ore
  5. In-phase thermomechanical fatigue studies on P92 steel with different hold time
  6. Effect of the weld parameter strategy on mechanical properties of double-sided laser-welded 2195 Al–Li alloy joints with filler wire
  7. The precipitation behavior of second phase in high titanium microalloyed steels and its effect on microstructure and properties of steel
  8. Development of a huge hybrid 3D-printer based on fused deposition modeling (FDM) incorporated with computer numerical control (CNC) machining for industrial applications
  9. Effect of different welding procedures on microstructure and mechanical property of TA15 titanium alloy joint
  10. Single-source-precursor synthesis and characterization of SiAlC(O) ceramics from a hyperbranched polyaluminocarbosilane
  11. Carbothermal reduction of red mud for iron extraction and sodium removal
  12. Reduction swelling mechanism of hematite fluxed briquettes
  13. Effect of in situ observation of cooling rates on acicular ferrite nucleation
  14. Corrosion behavior of WC–Co coating by plasma transferred arc on EH40 steel in low-temperature
  15. Study on the thermodynamic stability and evolution of inclusions in Al–Ti deoxidized steel
  16. Application on oxidation behavior of metallic copper in fire investigation
  17. Microstructural study of concrete performance after exposure to elevated temperatures via considering C–S–H nanostructure changes
  18. Prediction model of interfacial heat transfer coefficient changing with time and ingot diameter
  19. Design, fabrication, and testing of CVI-SiC/SiC turbine blisk under different load spectrums at elevated temperature
  20. Promoting of metallurgical bonding by ultrasonic insert process in steel–aluminum bimetallic castings
  21. Pre-reduction of carbon-containing pellets of high chromium vanadium–titanium magnetite at different temperatures
  22. Optimization of alkali metals discharge performance of blast furnace slag and its extreme value model
  23. Smelting high purity 55SiCr automobile suspension spring steel with different refractories
  24. Investigation into the thermal stability of a novel hot-work die steel 5CrNiMoVNb
  25. Residual stress relaxation considering microstructure evolution in heat treatment of metallic thin-walled part
  26. Experiments of Ti6Al4V manufactured by low-speed wire cut electrical discharge machining and electrical parameters optimization
  27. Effect of chloride ion concentration on stress corrosion cracking and electrochemical corrosion of high manganese steel
  28. Prediction of oxygen-blowing volume in BOF steelmaking process based on BP neural network and incremental learning
  29. Effect of annealing temperature on the structure and properties of FeCoCrNiMo high-entropy alloy
  30. Study on physical properties of Al2O3-based slags used for the self-propagating high-temperature synthesis (SHS) – metallurgy method
  31. Low-temperature corrosion behavior of laser cladding metal-based alloy coatings on EH40 high-strength steel for icebreaker
  32. Study on thermodynamics and dynamics of top slag modification in O5 automobile sheets
  33. Structure optimization of continuous casting tundish with channel-type induction heating using mathematical modeling
  34. Microstructure and mechanical properties of NbC–Ni cermets prepared by microwave sintering
  35. Spider-based FOPID controller design for temperature control in aluminium extrusion process
  36. Prediction model of BOF end-point P and O contents based on PCA–GA–BP neural network
  37. Study on hydrogen-induced stress corrosion of 7N01-T4 aluminum alloy for railway vehicles
  38. Study on the effect of micro-shrinkage porosity on the ultra-low temperature toughness of ferritic ductile iron
  39. Characterization of surface decarburization and oxidation behavior of Cr–Mo cold heading steel
  40. Effect of post-weld heat treatment on the microstructure and mechanical properties of laser-welded joints of SLM-316 L/rolled-316 L
  41. An investigation on as-cast microstructure and homogenization of nickel base superalloy René 65
  42. Effect of multiple laser re-melting on microstructure and properties of Fe-based coating
  43. Experimental study on the preparation of ferrophosphorus alloy using dephosphorization furnace slag by carbothermic reduction
  44. Research on aging behavior and safe storage life prediction of modified double base propellant
  45. Evaluation of the calorific value of exothermic sleeve material by the adiabatic calorimeter
  46. Thermodynamic calculation of phase equilibria in the Al–Fe–Zn–O system
  47. Effect of rare earth Y on microstructure and texture of oriented silicon steel during hot rolling and cold rolling processes
  48. Effect of ambient temperature on the jet characteristics of a swirl oxygen lance with mixed injection of CO2 + O2
  49. Research on the optimisation of the temperature field distribution of a multi microwave source agent system based on group consistency
  50. The dynamic softening identification and constitutive equation establishment of Ti–6.5Al–2Sn–4Zr–4Mo–1W–0.2Si alloy with initial lamellar microstructure
  51. Experimental investigation on microstructural characterization and mechanical properties of plasma arc welded Inconel 617 plates
  52. Numerical simulation and experimental research on cracking mechanism of twin-roll strip casting
  53. A novel method to control stress distribution and machining-induced deformation for thin-walled metallic parts
  54. Review Article
  55. A study on deep reinforcement learning-based crane scheduling model for uncertainty tasks
  56. Topical Issue on Science and Technology of Solar Energy
  57. Synthesis of alkaline-earth Zintl phosphides MZn2P2 (M = Ca, Sr, Ba) from Sn solutions
  58. Dynamics at crystal/melt interface during solidification of multicrystalline silicon
  59. Boron removal from silicon melt by gas blowing technique
  60. Removal of SiC and Si3N4 inclusions in solar cell Si scraps through slag refining
  61. Electrochemical production of silicon
  62. Electrical properties of zinc nitride and zinc tin nitride semiconductor thin films toward photovoltaic applications
  63. Special Issue on The 4th International Conference on Graphene and Novel Nanomaterials (GNN 2022)
  64. Effect of microstructure on tribocorrosion of FH36 low-temperature steels
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