Journal of Mining and Metallurgy, Section B: Metallurgy

Solidification behavior and environmental risk assessment of toxic elements on tailings from carbothermic reduction-magnetic separation of lead blast furnace slag

ziwei jiang; Min-ting Li, xingbin li, zhigan deng, chang wei, yinlei cao — Mon, 25 Dec 2023 00:00:00 +0100

Lead blast furnace slag (LBFS) generated during lead smelting is a hazardous solid waste containing potentially toxic elements (Pb, Zn, As, and Cd) with high mobility and solubility. In this study, a process for the utilization of LBFS by carbothermic reduction-magnetic separation method is proposed. Leaching toxicity and Tessier sequential extraction experiments were conducted on LBFS and magnetic separation tailings (TS), and the environmental risk was evaluated using the risk assessment coding index and potential ecological risk index. The obtained results showed that the potentially toxic elements in the TS were solidified in the spinel phase or silicate phase. In addition, the XRD, SEM-EDS, and FTIR results showed the formation of PbCa2Si3O9, ZnAl2O4, and Ca3(AsO4)2 phases. The leaching concentrations of Pb, Zn, As, and Cd in TS were much lower than the toxicity characteristic leaching procedure (TCLP) and China standard leaching test (CSLT) limits. The results of Tessier sequential extraction procedure confirmed that the proportions of the stable residual state of the potentially toxic elements in TS were significantly higher than in LBFS. Furthermore, the ecological environmental risk level for the TS decreased significantly compared to that of LBFS.

Phase transformation mechanism of oxidation roasting of low-grade polymetallic chalcopyrite ore in the presence of CaO

Haifei Ma, Yalong Liao, Min WU, Xiaobao Jia, shuangyu Yang — Mon, 25 Dec 2023 00:00:00 +0100

Low-grade polymetallic chalcopyrite ore has a high lead and iron content and a low softening point, which is difficult to treat using conventional pyrometallurgical and hydrometallurgical processes. In order to investigate the suitable methodology for efficient utilization, it was pelletized with CaO for oxidation roasting in the present work. By controlling the Po2 and Pso2 in the gas phase, the metal sulfide in the ore was converted into easily soluble metal oxide, the thermal analysis of the roasting process was carried out and the acid leaching of the extracted calcine at atmospheric pressure was investigated. The results show that by pelletizing with CaO and then roasting at 800 ℃ for 1 h, chalcopyrite is converted into CuO, which can be easily dissolved, galena and pyrite are converted into PbO2 and Fe2O3, respectively, and sulfur reacts with CaO and turns into CaSO4, which can fix the sulfur in the calcine. The copper leaching rate of calcine can reach 98.60 wt.% under atmospheric pressure in the H2SO4-H2O system. CaO can increase the softening point of raw materials, improve the roasting effect, promote the phase transformation of chalcopyrite in the oxidation process, and convert sulfur into CaSO4 to fix sulfur, effectively avoiding SO2 pollution to the environment.

Recovery of pure MnSO4 by crystallization after separation of Fe(III) and Zn(II) from the reductive leaching solution of manganese dust containing Mn3O4

Manseung Lee, Jiangxian Wen — Mon, 25 Dec 2023 00:00:00 +0100

Manganese dust generated during the production of ferroalloys contains iron and zinc oxides together with other minor oxides. Pure manganese compounds can be recovered from the leaching solution of the manganese dust by removing the impure ions. In this work, sulfuric acid and ferrous sulfate were employed as leaching and reducing agents for the manganese oxides in the dust. First, the leaching conditions for complete dissolution of the manganese oxides were investigated by varying the concentration of sulfuric acid and ferrous sulfate, and pulp density. Second, after oxidizing Fe(II) to Fe(III) by hydrogen peroxide, Fe(III) was removed from the solution by three stages of counter current extraction with D2EHPA. Third, Zn(II) was removed by two stages of cross current extraction with Cyanex 272. Stripping conditions for Fe(III) and Zn(II) were determined from the respective loaded organics. Fourth, Mn(OH)2 was precipitated from the raffinate by adjusting the pH of the solution to 10 with NaOH solution. The MnSO4 crystals with 99.5% purity were recovered by crystallization from the sulfuric acid solutions after the precipitates of Mn(OH)2 were dissolved. A comparison of the cost of the chemicals used to recover MnO2 and MnSO4 indicated that the current process was much more economical.

Thermodynamic description of the Mg-O and Al-O systems

Shuhong Liu, Xiaojing Li — Mon, 25 Dec 2023 00:00:00 +0100

Thermodynamic properties of oxides have a significant impact on the corrosion behavior of alloys. MgO and Al₂O₃ are important products in the corrosion process of Mg-Al alloys, so it is necessary to investigate their thermodynamic properties. The Mg-O and Al-O systems have been critically evaluated and re-assessed by the CALPHAD (CALculation of PHAse Diagram) approach. The liquid phases of these systems were described using the ionic liquid model. According to the literature data, the oxide phases, MgO and Al₂O₃ were treated as stoichiometric compounds. Thermodynamic parameters of the two stoichiometric compounds were optimized by considering both phase diagram and thermodynamic data and a set of self-consistent thermodynamic parameters was finally obtained for each system. The calculated results using the presently obtained thermodynamic parameters can reproduce the reliable experimental data in the literature reasonably.

Thermodynamic measurements and ab initio calculations of the indium-lithium system

Wojciech Gierlotka, Adam Dębski, Miłosz Zabrocki, Anna Góral, Władysław Gąsior — Mon, 25 Dec 2023 00:00:00 +0100

The limiting enthalpy of the solution of liquid indium in liquid tin was measured at 723 K. The calorimetric method was applied to determine the standard enthalpy of the formation of intermetallic phases and alloys from the In-Li system. The measurements were done at 747 K and 756 K. The structures of prepared alloys were confirmed by the X-ray diffraction measurements. Besides that, the ab initio calculations allowed the modeling of the formation energies, the volume thermal expansion, the heat capacity under constant pressure, and the elastic properties of the intermetallic phases. The theoretical formation energies show good agreement with the experimental findings. The analysis of the phonon dispersion indicates an instability of the InLi phase in the Fd-3m space group. A further investigation on the atomic arrangement in the case of the equiatomic ratio is suggested.

Thermal upgrading of manganese ores prior to smelting

Said Eray — Mon, 25 Dec 2023 00:00:00 +0100

Ferromanganese smelting in electric arc furnaces is an energy-intensive process with corresponding CO2 emissions and environmental impacts. Upgrading the furnace charge can improve process efficiency and decrease electricity consumption. An oxide manganese ore, consisting mainly of pyrolusite, calcite and goethite, was thermally upgraded by calcination and solid-state reduction. During calcination of the ore at 900-1100°C, carbonates and hydroxides were decomposed and a considerable amount of oxygen was removed. The manganese content of the run-of-mine ore was increased from 39.86% to 47% after calcination. Carbothermic reduction of the ore at 1250°C resulted in almost all of the iron oxide and some of the manganese oxide passing into the metallic form. The results showed that a significant part of the endothermic reactions during the solid-state treatment of the ore can be carried out with low-cost fossil fuels. This leads to enrichment of the electric arc furnace charge, lower electricity consumption in the furnace, lower overall processing costs and a more efficient smelting process.

Effect of temperature on oxidation behavior and occurrence state of sulfur in KR slag

Jianli Li, JiaJun Jiang, Chao Xiao, Yue Yu — Mon, 25 Dec 2023 00:00:00 +0100

The main component (CaO) in KR (Kambara reaction) desulfurization slag is a high value slag raw material for converter smelting, and attempts to utilize KR desulfurization slag in converter smelting are conducive to reducing the buildup of KR desulfurization slag and improving the economic efficiency of converter smelting. However, the removal of sulfur in the slag is a key issue. The influence of temperature on the sulfur oxidation behavior in KR slag in the form of synthetic slag was investigated. SEM-EDS, XRD, and an infrared carbon and sulfur analyzer were used to analyze and detect the oxidized slag samples at different temperatures. The results show that the desulfurization rate increases gradually with the increase in temperature at a flow rate of Ar-50%O2 of 2 L/ min. Under the condition of low temperature (T ≤ 1220 oC), the desulfurization rate of slag is less affected by temperature. When T > is 1220 oC, the desulfurization rate of slag is greatly affected by temperature. When the reaction temperature reaches 1420 oC, the desulfurization rate reaches 93.5%. Furthermore, the types of sulfur-containing phases in the oxidized slag samples gradually decrease with the increase of temperature, and the sulfur in the oxidized slag samples is mainly present in the silicate phase when the temperature is less than or equal to 1220 oC.

Characterization of cryorolled low carbon steel using ferrite-martensite starting microstructure

Mon, 25 Dec 2023 00:00:00 +0100

Cryo-rolling, a technique of severe plastic deformation (SPD) performed at cryogenic temperatures, has proven to be a promising technique for improving the microstructure and mechanical properties of low-carbon steels. Low carbon steel with a two-phase ferrite-martensite starting microstructure was subjected to cryogenic rolling at liquid nitrogen temperature to produce sheets with different deformation rates: 50%, 70%, and 90%. The microstructure, mechanical properties, and corrosion resistance were investigated. The results show that cryo-rolling effectively refines the microstructure and leads to a higher dislocation density and smaller grain size as the deformation rate increases. The cryo-rolled sample deformed at 90% has the highest grain aspect ratio (35.5), the smallest crystallite size (13.70 nm), the highest lattice strain (74.6 x 10-3), and the highest dislocation density compared to the samples deformed at 50% and 70%. This refined microstructure significantly improves the mechanical properties, with the cryo-rolled sample deformed at 90% exhibiting the highest hardness (152 HV), tensile strength (1020 MPa), and yield strength (950 MPa), corresponding to an increase of 175.6%, 344.0%, and 466.5%, respectively. In addition, cryo-rolling at 90% showed a decrease in corrosion resistance, with the lowest corrosion rate observed at 90% deformation (5.97 mm/year).

Effect of olivine as MgO-bearing flux on low- and high-alumina iron ore pellets

Umadevi T, Rameshwar Sah — Mon, 25 Dec 2023 00:00:00 +0100

In the present study, the effect of MgO in the form of olivine flux on low- and high-alumina iron ore pellet mineralogy and pellet quality was studied. Green pellets were prepared by varying the MgO content from 0 to 1.5% with a basicity (CaO/SiO2) of 0.30. The pellets were tested for green pellet properties, cold crushing strength (CCS), and reduction degradation index (RDI) and fired at temperatures between 1300 and 1320 oC. An optical microscope with an image analyzer, SEM-EDS, was used to assess the mineralogical phases present in the pellets and the chemical analysis of the mineralogical phases, respectively. The laboratory tests showed that with increasing MgO addition in both low and high alumina pellets, magnesio-ferrite & silicate melt phases increased and the porosity and hematite phases decreased. The decrease in porosity was due to increase in silicate melt formation from the silica in the olivine. With increasing MgO addition, the CCS value of the pellets increased up to an MgO content of 0.9 to 1.1%. Thereafter, the CCS value of the pellets decreased with increasing MgO addition for both low and high alumina pellets. At an MgO content of 0.9 to 1.1%, the CCS value was higher due to the formation of a low melting point magnesio-ferrite phase, which imparted strength to the pellets. For pellets with an MgO level of >1.1, the RDI was within the control limit for both low- and high-alumina pellets. This may be due to a reduction in the porosity of the pellet and a better distribution of the silicate melt phase. Low-alumina pellets showed better physical and metallurgical properties compared to high-alumina iron ore pellets.

Synergistic effect of Pd+Rh on the microstructure and oxidation resistance of aluminide coatings

Maryana Zagula-Yavorska — Mon, 25 Dec 2023 00:00:00 +0100

The Pd+Rh modified aluminide coatings were deposited on nickel and CMSX-4 nickel superalloy. The Pd layer (2.5 µm thick) and the subsequent Rh layer (0.5 µm thick) were electroplated on both nickel and CMSX-4. The aluminization of the substrates with Pd+Rh layers was carried out using the CVD method. Two zones (outer and interdiffusing) were observed on both coatings. The β-NiAl phase doped in palladium was formed in the outer zones and β-NiAl phase doped with palladium and rhodium was formed at the boundary between the outer and interdiffusion zones of both coatings. The γ’-Ni3Al phase and μ-Co7Mo6 precipitates in the β-NiAl matrix were found in the interdiffusion zone on nickel and CMSX-4 superalloy respectively. The simultaneous use of Pd and Rh in the aluminide coating slowed down their oxidation rate. Moreover, Pd+Rh co-doping is more efficient than Pd+Hf in reducing the oxidation rate of aluminide coating on CMSX-4 superalloy.

Synthesis of ultrafine (Mo,W)Si2 composite powders from high purity molybdenum concentrate

Guohua Zhang, Jia-Bing Huang — Mon, 25 Dec 2023 00:00:00 +0100

(Mo,W)Si2 composite powders with the grain size of about 1 μm were synthesized at 1150 ℃ for 2 h. The high purity molybdenum concentrate (with the main component of MoS2), W and Si powders were utilized as raw materials and lime as desulfurizer. The graphite felt was laid between the compact (made of MoS2, W and Si) and the lime to facilitate the separation of the produced composite powders from desulfurization product. The phase composition, microstructure evolution, and residual sulfur content during the silicothermic reduction reaction were evaluated. The experimental results showed that the reaction could be completed after a reaction time of 1150 ℃ for 2 h, and the residual sulfur content of the product was 0.087 wt.%. It was concluded that the interactions between Si and the intermediate products of SiS and SiS2 are crucial for the preparation of (Mo,W)Si2 composite powders at low temperatures. The preparation process could be divided into three stages: solid state reactions between MoS2, W and Si to produce MoSi2, WSi2 and gaseous SiS; gas-solid reaction between MoS2, W and gaseous SiS to generate MoSi2, WSi2 and gaseous SiS2; and gas-solid reaction between gaseous SiS2 and Si to form SiS gas. With this short flow process, fine-grained (Mo,W)Si2 composite powders can be produced at low cost at low temperature, which has great application potential.

Lithium slag leach solution refining by hydroxide precipitation

Mon, 25 Dec 2023 00:00:00 +0100

Lithium-ion batteries contain many of critically important metals and their effective recycling is key for the sustainable development of the EU. In the past, only metals such as Co, Ni, and Cu were recycled by pyrometallurgy, and Li and Al were concentrated in the slags and not further processed. Novel approach of a black mass pyrometallurgical treatment propose possibility of further hydrometallurgical recycling of slags. In this paper, refining of solution obtained by leaching of slag in sulfuric acid is studied. Leach solution most valuable element is Li, but in addition it also contains Al, Si, Co, Mn, Ni and Cu, which removal is essential before high purity Li recovery is possible. Refining is performed by pH adjustment by addition of NaOH, which confirm the possibility of 100% removal of Al, Mn, 93.56% removal of Si, 86.36% removal of Cu and 61.75% removal of Co. Results also confirmed that solution refining by the addition of NaOH is causing lithium losses from 10% at pH 7 to 28% at pH 12, therefore it is proposed to combine more solution refining methods before pure Li₂CO₃ with minimum losses is precipitated.

Smelting of low-grade saprolitic nickel ore in DC-Arc furnace

Mon, 25 Dec 2023 00:00:00 +0100

Most nickel laterite smelting to produce ferronickel is carried out using an AC-arc furnace. Although the DC-arc furnace is advantageous in the smelting of fine ore, it is rarely used for nickel laterite. In this work, the effects of slag basicity and stoichiometry of reductant addition during smelting of low-grade saprolitic nickel ore on nickel content and nickel recovery, yield, and phases of the slag were studied in detail. The smelting process was conducted in a laboratory DC-arc furnace with a a single electrode of 30 cm diameter. A 5 kg of low-grade saprolitic nickel ore (1.92 Ni-12.97 Fe), some coke as reductant, and some limestone as flux were smelted in a DC-arc furnace for about one hour. The pouring temperature of hot metal and slag was 1400-1500 °C. The basicity of the quaternary slag of 0.8 and the stoichiometric carbon of 0.8 of the reductant resulted in an optimum smelting process of nickel ore in a DC-arc furnace, producing ferronickel with a Ni content of 14.59% with 92.26% recovery.

Combing role of MgO and Al2O3 on viscosity and its correlation to structure of fluorine-free mold fluxes

Hai-chuan Wang, Guangda Bao, Shama Sadaf, Si-shuo Mao, Ting Wu — Mon, 25 Dec 2023 00:00:00 +0100

By using FactSage calculations, Fourier transform infrared spectroscopy (FTIR), rotational viscometers, and X-ray diffraction (XRD), the combined effect of MgO and Al2O3 on fluorine-free mold flux was confirmed. The viscosity of the slag at 1300 oC decreased with 2-10 wt% MgO, and higher Al2O3 increased the overall viscosity. The trend of the experimental results was consistent with the models of Riboud and Iida, while the FactSage calculation values were relatively higher. The viscosity of the slag was more influenced by the Si-O network than by the Al(B)-O structure and the MgO has a dual effect on the slag structure. The viscosity-temperature curves changed from alkaline to acidic slag characteristics when Al2O3 increased from 8 wt% to 12 wt%, and the trend was not uniform with the addition of 2-10 wt% MgO. Both FactSage calculation and XRD patterns showed that increasing MgO content gradually promoted the growth of Ca3MgSi2O8 and Ca11Si4B2O22 crystals, while the addition of Al2O3 inhibited crystal precipitation.

The influence of new severe plastic deformation on microstructure, mechanical, and corrosion properties of Mg-0.8Mn-0.5Ca alloy

Masood Khani; Gholamreza Ebrahimi, H.R. Ezatpour; Amir Momeni — Mon, 25 Dec 2023 00:00:00 +0100

In this research, the effect of accumulative extrusion bonding (AEB) on the microstructure and mechanical properties of Mg-0.8Mn-0.5Ca biocompatible alloy was investigated. The goal of this research was to develop the mechanical and corrosion properties of Mg-0.8Mn-0.5Ca alloy after ABE process as a novel severe plastic deformation process. The simulation of AEB process showed that the average effective strain per pass for channels with the internal angle of 120 was about 1.93. The average grain size was dramatically decreased from about 448.3 µm for the homogenized alloy to 1.55 µm for the 3-pass processed sample. Microstructural observations suggested a combination of continuous, discontinuous, and twinning-induced dynamic recrystallization as the major mechanisms of grain refinement. Tensile and compressive strengths were improved from 150 and 205 MPa to 330 and 301 MPa after three passes of AEB, indicating 2 and 1.5 times improvements, respectively. Tensile elongation decreased from 26% for the homogenized sample to 7.5% for the 3-pass processed sample due to the severe work-hardening, non-uniform strains, and inhomogeneous microstructure produced by the ABE process. Corrosion resistance in SBF solution was improved from 1.1 to 14.159 〖KΩ Cm〗^2 after three passes of ABE due to the presence of hydroxyapatite formed on the surface of the AEBed samples.