China Nonferrous Metallurgy

Abstract:Deep-sea polymetallic nodules are widely distributed on the seafloor, rich in manganese, iron, cobalt, nickel, copper and other metal elements, and have significant economic value. In order to maximize the use of these precious metal resources, this study conducted a systematic mineralogical analysis of deep-sea polymetallic nodules. The research content covers chemical composition analysis, morphological characterization, phase structure evaluation and microscopic observation. The mineral composition of nodules was systematically studied by means of X-ray diffraction (XRD), all element chemical analysis, particle size analysis, scanning electron microscope energy dispersive spectroscopy (SEM-EDS) and Fourier transform infrared spectroscopy (FT-IR). The results show that the main mineral components of polymetallic nodules are manganese olivine, manganese spinel and nepheline, with low crystallinity. The chemical phase analysis shows that manganese, iron, copper, cobalt and nickel mainly exist in the form of oxides. Iron ore mostly exists in the crust of nodules and core debris in the form of fine-grained colloid or cryptocrystalline, which makes it impossible to achieve enrichment and separation through mechanical separation. Silicon-alumina-bearing vein minerals such as quartz and feldspar are mainly concentrated in rock debris, clay clusters, or dispersed in iron rich micro layers, further increasing the difficulty of mechanical separation. The chemical composition of polymetallic nodules is extremely complex and contains many elements. The total content of cobalt, nickel, copper (CO+Ni+Cu) and other precious heavy metals was 2.28%, and the content of manganese and iron were 28.51% and 9.06%, respectively. In addition, molybdenum, zinc, vanadium, yttrium and other trace elements with potential economic value also exist in it. Because the authigenic mineral particles in the polymetallic nodules are extremely small and the metal elements such as nickel, cobalt, copper and manganese are closely symbiotic, the traditional mineral processing method is difficult to work. Therefore, metallurgical processing has become the only feasible way to extract precious metals from deep-sea polymetallic nodules.

Abstract:The main metal elements in deep-sea polymetallic nodules include manganese, iron, nickel, cobalt, and copper, mainly existing in the form of silicate-aluminum-manganese oxides. To achieve green and efficient extraction of the target metals (manganese, nickel, cobalt, copper) from this ore, this study employs a ammonium chloride roasting-leaching process. Ammonium chloride roasting can convert the target metal ores into soluble chlorides, which can then be separated from gangue and impurities through water leaching. Single-factor experiments were used to optimize the process parameters, and various characterization methods were applied to investigate the changes in the occurrence states of the target metals, leading to the following main conclusions. Thermodynamic analysis indicates that at 300°C, CoO, NiO, CuO, and MnO₂ in the nodules can undergo chlorination to form chlorides, while the chlorination reaction of Fe₂O₃ has a ΔG much greater than 0, so it cannot occur spontaneously. Under the conditions of a mass ratio of deep-sea polymetallic nodules to ammonium chloride of 1:1.6, roasting temperature of 300°C, roasting time of 90 minutes, liquid-solid ratio (mL/g) of 6:1, leaching temperature of 40°C, and leaching time of 60 minutes, the leaching rates of manganese, nickel, cobalt, and copper can reach over 99%, while the leaching rate of iron is about 20%, effectively separating manganese, nickel, cobalt, and copper from iron, facilitating subsequent purification of the target metals. Multiple characterization analyses show that the chlorine element is successfully incorporated into the lattice of the roasted products, Mn⁴⁺ and Mn³⁺ oxides in the raw ore convert to Mn²⁺, accompanied by the formation of Fe₂O₃. The main phases in the leach residue were SiO₂, with only weak characteristic peaks of Fe₂O₃, and the extraction of manganese was nearly complete. These results can provide theoretical and technological references for the industrial utilization of deep-sea polymetallic nodule resources.

Abstract:The efficient separation of manganese, nickel and cobalt from copper and iron in deep-sea polymetallic nodules is an urgent technical challenge in hydrometallurgy. In this work, deep-sea polymetallic nodules collected from the South Pacific were used as raw materials, and a sulfur dioxide reductive leaching process was adopted. The effects of reductant dosage, leaching temperature, sulfuric acid dosage and stirring speed on the leaching behavior of each metal were systematically investigated, and the selective leaching mechanism was elucidated by combining thermodynamic analysis and phase characterization. The results show that under the optimal conditions of no additional sulfuric acid, a leaching temperature of 70℃, a liquid-to-solid ratio of 5 mL/g, an SO? dosage of 1000 mL per 20 g of raw ore, a stirring speed of 350 r/min and a leaching time of 2 h, the leaching efficiencies of Mn, Ni and Co reach 94. 89%, 81. 81% and 84. 17% respectively, while those of Cu and Fe are only 28. 43% and 9. 91%, realizing selective and efficient extraction of manganese, nickel and cobalt. At a sulfuric acid dosage of 10 g per 20 g of raw ore, the manganese leaching efficiency can be further increased to 99. 89%, but the system selectivity is significantly reduced, with the leaching efficiencies of copper and iron rising to 95. 15% and 80. 87% respectively. Mechanistic analysis reveals that SO? preferentially reduces MnO? to form soluble Mn2?; in the acid-free system, goethite is transformed into a stable magnetite phase, which naturally suppresses iron leaching; the addition of sulfuric acid alters the thermodynamic stability region of the system, promotes the dissolution of iron oxides and releases occluded copper, thus reducing the separation efficiency. These findings can provide theoretical and technical support for the clean and efficient utilization of deep-sea polymetallic nodule resources.

Abstract:More than 70% of the world's lithium resources exist in the form of salt lake brine, and the characteristics of high magnesium-lithium ratio and complex impurity components put forward strict requirements for the selectivity and separation efficiency of lithium extraction technology. This paper focuses on the technology of extracting lithium from salt lake with high Mg: Li ratio (Mg: Li > 500). In view of the problems of poor selectivity and difficult separation in the traditional technology of extracting lithium from salt lake with high Mg: Li ratio （chemical precipitation method and solvent extraction method）, this paper deeply analyzes the emerging technologies of ion sieve adsorption, membrane separation method and coupling lithium extraction from the aspects of molecular action mechanism, crystal structure change and ion migration law, and introduces their application. Ion sieve adsorption is the mainstream technology in the field of extracting lithium from salt lakes at present. Among them, aluminum ion sieve has been industrialized, while manganese ion sieve and titanium ion sieve are still in the stage of laboratory and pilot test. However, due to their excellent saturated adsorption capacities (30-35 mg·g^-1, 15-25 mg·g^-1, respectively, while aluminum ion sieve is only 3-5 mg·g^-1), aluminum ion sieve has been widely used. Lithium ion selective membrane method is a special technology for extracting lithium from salt lakes with high magnesium-lithium ratio, which has the advantages of continuous operation and no secondary pollution, but the flux and stability of membrane materials restrict its industrial application. Coupled lithium extraction technology includes adsorption-membrane separation coupling technology, high gravity enhanced extraction coupling technology, electrochemical intercalation-deintercalation (IDI) lithium extraction technology, etc. , which has the advantages of strong adaptability, high comprehensive benefit and flexible adjustment of process parameters, and is an important development direction of lithium extraction technology in salt lakes with high magnesium-lithium ratio in the future. The adsorption capacity and cycle stability of ion sieve adsorbents can be improved by means of material modification, morphology control and composite modification. In the future, with the research and development of new adsorbents and membrane materials, the optimization of coupling process and the application of intelligent technology, the lithium extraction technology from salt lakes with high magnesium-lithium ratio will achieve leap-forward development, providing a solid resource guarantee for the sustainable development of global new energy industry.

Abstract:Chlorination roasting represents a critical thermal treatment technology offering distinct advantages in processing complex polymetallic materials. It continues to play a pivotal role in fields such as the comprehensive recovery and utilization of secondary resources, the processing of low-grade refractory ores, and the deep purification of high-purity materials. This paper systematically reviews recent research progress and industrial applications of chlorination roasting technology, highlighting its classification methods, reaction mechanisms, and thermodynamic and kinetic fundamentals. Key process units, including feedstock pretreatment, the roasting process, product recovery, and waste treatment, are thoroughly discussed. Furthermore, by reviewing numerous relevant studies, this paper demonstrates the significant merits of this technology in efficiently recovering valuable metals from complex feedstocks such as refractory ores, solid mining waste, and e-waste and in deeply removing impurity elements to produce high-purity materials. However, the technology faces challenges such as severe equipment corrosion, high capital and maintenance costs, elevated energy consumption, and complex off-gas treatment systems. Future efforts should focus on low-temperature chlorination, chlorinating agent recycling, multi-technology integration, and intelligent process control to achieve green, efficient, and large-scale industrial application.

Abstract:The non-ferrous metal industry is a key industry for carbon emissions in China's industrial sector. Carbon Capture, Utilization and Storage (CCUS) technology is an important way to achieve carbon neutralization in the non-ferrous metal industry. Among them, the solid adsorption carbon capture technology has attracted extensive attention from researchers and industry experts due to its simple process flow and high degree of automation. The CO? pressure swing adsorption technology using carbon based materials, molecular sieves, and solid amine based adsorbent materials as adsorbents has gradually been carried out in pilot and engineering demonstration projects for post combustion flue gas carbon capture in coal-fired power plants, lime kilns, etc. , and has made critical progress. At the same time, the research on new CO? adsorption materials such as metal organic framework materials (MOFs), porous organic polymers (POPs), and layered double hydroxides also provides more material choices for carbon capture technology under different working conditions. At present, adsorption based CO? separation and capture technology is mainly applicable to the CO? capture process at the end of non-ferrous metal smelting. However, the stability and cost control of adsorbents and process related parameters under high sulfur conditions in non-ferrous smelting flue gas still need to be further improved and optimized through research. In the actual application process, it is also necessary to draw on the experience of application fields such as coal-fired power plants, combined with multi-disciplinary fields such as non-ferrous metallurgy, to seek the application scenarios of carbon capture technology COproducts in non-ferrous metallurgy and related fields, solve the economic benefits of carbon capture processes, and further explore the process path of cost reduction and efficiency improvement.

Abstract:There is still 44.93% of iron in the tailing, which is generated during the treatment of high-iron bauxite by the novel reductive Bayer process. This study adopted a magnetization roasting-magnetic separation process for enhanced recovery of Fe-bearing minerals in the tailing. The effects of process parameters on the products were investigated through single-factor experiments. The roasted products, magnetic concentrate, and tailings were characterized to analyze the magnetization roasting behavior and magnetic separation behavior. The main conclusions are as follows: the main mineral in the tailings is hematite, with particle size mainly distributed in the range of 0~10 μm and an average particle size of 1.98 μm. The magnetization roasting results shows that prolonging roasting time and temperature both promote the directional conversion of hematite into magnetite in the tailing. Under the roasting temperature of 600°C and roasting time of ≥40 min, the dominant phase in the product is magnetite. At a grinding fineness of D(90) = 16.36 μm and a magnetic field intensity of 1 000 Gs, a concentrate with yield of 57.99%, iron grade of 52.57% and iron recovery of 70.69% was obtained, which increased the resource utilization ratio of high-iron red mud from 55% to 80%. The incomplete recovery of magnetite is attributed to the agglomeration of fine particles during grinding, which hinders the efficient separation of magnetite from aluminosilicate minerals. In subsequent work, the introduction of a dispersant during grinding is being considered to further improve the iron recovery in the magnetic concentrate.

Abstract:When using liquid-liquid solvent extraction to directly separate low-concentration rare earth ions from leachate, there are problems such as high organic phase dissolution loss and easy emulsification, resulting in a large amount of oily wastewater. In this study, the surfactant Span 80 was added as an interfacial stabilizer in the P507-kerosene extraction system, and the effects of aqueous Er³⁺ concentration, impurity ion (Mg²⁺/Al³⁺) concentration, operating temperature, and the number of organic phase recycling times on Er³⁺ extraction performance and oil content in the raffinate were systematically analyzed. The results show that under optimal conditions, the Er³⁺ extraction rate reached 99.77%, and the oil content in the raffinate was as low as 1.14 mg/L. After three cycles of organic phase reuse, the extraction rate was still above 98%, indicating that this stabilizer significantly improves the reusability and stability of the organic phase. AFM, FTIR and DFT analyses revealed that Span 80 can optimize the molecular arrangement at the interface and enhance the interfacial film strength, thereby effectively suppressing emulsification and reducing organic phase loss. Increasing the Er³⁺ concentration or introducing an appropriate amount of salting-out agent Mg²⁺ can reduce the oil content in the raffinate, whereas Al³⁺, due to hydrolysis to form polynuclear hydroxy complexes, can destroy the interface, resulting in decreased extraction rate and increased oil content.

Abstract:Black shale stands as a strategically vital mineral resource across China, distinguished by vast reserves and extensive geographical distribution. These geological formations encapsulate critical rare metals—vanadium, nickel, and molybdenum—yet remain substantially untapped due to subeconomic grades and complex metallogenic characteristics. Bioleaching emerges as a transformative extraction technology, wherein heap bioleaching processes demonstrate compelling advantages for shale resource development through operational scalability, minimized energy expenditure, and reduced ecological impact. In this study, three groups of bioleaching bacteria with distinct temperature adaptabilities (mesophilic mixed bacteria, moderate thermophilic mixed bacteria and thermophilic mixed bacteria) were selected to conduct systematic bioleaching experiments for vanadium, nickel and molybdenum from black shale. The primary conclusions are summarized as follows. All consortia exhibited pronounced efficacy in extracting vanadium (57%~74%) and nickel (83%~88%) from black shale matrices. The leaching percentage of molybdenum is relatively low: while the thermophilic consortium achieved merely 1%~5% extraction, mesophilic and moderate thermophilic variants attained 10%~20%. Subsequent designation of the mesophilic consortium as the optimized biological extractor enabled high-throughput genomic analysis, revealing functional dominance by Leptospirillum ferriphilum and Acidithiobacillus spp. , after domestication, the proportion of Acidithiobacillus spp. increased. These taxa demonstrated synergistic roles in iron/sulfur oxidation critical to metal solubilization. At present, the metal leaching efficiencies of black shale via bioleaching remain lower than those of other technologies, and the leaching performance of molybdenum is unsatisfactory. Further research should focus on the synergistic effects among microorganisms, the coupling relationship between temperature-adapted microorganisms and the temperature field in heap leaching, as well as the bioleaching mechanism. This work is expected to provide theoretical basis and technical support for the efficient and green bio-extraction of vanadium, nickel and molybdenum from black shale.

Abstract:To address the high cost of single-factor process experiments and Design-Expert software, this study investigates the sulfuric acid leaching of high-clay copper oxide ore. A central composite design (CCD) was employed to conduct 20 sets of acid leaching experiments. With sulfuric acid concentration, liquid-to-solid ratio, and leaching time as independent variables, and copper leaching rate as the response value, a quadratic regression model was established using Excel. Analysis of variance (ANOVA) and response surface optimization were performed to determine the optimal solution. The results show that the model is highly significant (F = 91. 14, R2 = 0. 988). The influence of factors on the leaching rate follows the order: sulfuric acid concentration > leaching time > liquid-to-solid ratio. The interaction between sulfuric acid concentration and liquid-to-solid ratio exhibits a significant negative effect. The optimal process conditions obtained from the response surface optimization are: sulfuric acid concentration of 96. 16 g/L, liquid-to-solid ratio of 3. 26 mL/g, and leaching time of 4. 32 h, with a predicted leaching rate of 83. 39%. A verification experiment yielded a leaching rate of 84. 15%, showing good agreement with the prediction, indicating the predictive accuracy of the model and the reliability of the optimization results. By replacing professional statistical software with Excel, this method not only provides an efficient parameter optimization strategy for the sulfuric acid leaching process of high-clay copper oxide ore but also offers a cost-effective and easy-to-operate solution for process optimization in mineral processing and other related fields.

Abstract:Rare earth doping and deep cryogenic treatment are both advanced methods for improving material performance. In this study, a novel AZ91D-0.1Ti-1.5Sm magnesium alloy was successfully fabricated by introducing Ti and Sm alloying elements into the AZ91D magnesium alloy matrix via an alloying approach. The alloy was subjected to cryogenic treatment in liquid nitrogen at -196℃ for durations of 6 h, 12 h, 18 h, and 24 h, respectively. A comprehensive combination of characterization methods including optical microscopy, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), mechanical property testing, and electrochemical corrosion measurements was employed to systematically investigate the influence and underlying mechanisms of cryogenic treatment time on the microstructure, mechanical properties, and corrosion resistance of the alloy. The results demonstrate that cryogenic treatment refines the α-Mg matrix grains and significantly increases the volume fraction of the β-Mg₁₇Al₁₂ phase and Al₂Sm rare-earth phase with a more dispersed distribution. However, as the treatment time extends to 24 h, the β-Mg₁₇Al₁₂ phase gradually transforms from dispersed particles into a continuous network-like morphology, accompanied by coarsening and agglomeration of the Al₂Sm phase. Regarding mechanical properties, optimal comprehensive performance is achieved at 12 h of cryogenic treatment, with microhardness increasing from 69.54 HV (untreated sample) to 72.38 HV, tensile strength from 189 MPa to 196 MPa, and elongation from 4.90% to 5.13%. Nevertheless, after 24 h of treatment, the mechanical properties deteriorate significantly, with microhardness dropping to 67.12 HV, tensile strength to 176 MPa, and elongation to 4.36%. In terms of corrosion performance, the 12 h cryogenically treated sample exhibits the best corrosion resistance, with corrosion current density decreasing from 15.8 μA·cm^-2 (as-cast) to 10.2 μA·cm^-2, and corrosion potential shifting positively from -0.79 V to -0.69 V. After 24 h, the corrosion resistance deteriorates, with corrosion current density increasing to 43.6 μA·cm^-2. Controlled cryogenic treatment duration (with 12 h identified as the optimal processing window) can effectively enhance both the mechanical properties and corrosion resistance of this magnesium alloy.

Abstract:With the rapid development of renewable energy and portable electronic devices, the development of new energy storage materials with high energy density, high power density, and long cycle life is the key to breaking through the current bottlenecks in energy storage technology. In response to the issues of low electronic conductivity and insufficient cycling stability of the single ZnCo?O? electrode material, this study aimed to construct a heterostructure by introducing V?O?. Using a two-step hydrothermal method-in situ growth process, a ZnCo?O?/V?O? heterostructure nanosheet array was successfully fabricated on the foam nickel substrate, and systematic electrochemical tests and cycling stability tests were conducted on it. The following main conclusions were drawn. This composite material exhibits a double redox peak, and the analysis of the storage mechanism shows that the b value ranges from 0.82 to 0.84, indicating a mixed storage mechanism dominated by surface capacitance behavior. The charge transfer resistance is as low as 0.80 Ω, demonstrating excellent reaction kinetics characteristics. The composite material has a specific capacity of 850 C·g?1 at a current density of 1 A·g?1, a capacity retention rate of 70.6% at a high current density of 10 A·g?1, a capacity retention rate of 91.7% after 1 000 cycles at 5 A·g?1, and an energy density retention rate of 89.6%. The comprehensive electrochemical performance of this composite material is significantly superior to that of pure ZnCo?O? and pure V?O? electrodes. The tight hetero-interface of this material belongs to an in situ growth without binder construction, which optimizes the electron transmission path and shortens the ion diffusion distance, and collaboratively achieves a unified high specific capacity, excellent rate performance, and long cycling stability. This provides a new idea for the development of high-performance supercapacitor electrode materials. The long-term cycling stability test results show that after 1 000 cycles at a high current density of 5 A·g?1, the specific capacity of the ZnCo?O?/V?O? electrode stabilizes at 660.0 C·g?1 from the initial 720.0 C·g?1, with a capacity retention rate of 91.7%, an energy density retention rate of 89.6%, and a power density retention rate of 97.8%, which is significantly better than that of pure ZnCo?O? and pure V?O? electrodes. The ZnCo?O?/V?O? composite material prepared in this study not only provides a high initial capacity but also exhibits slow capacity decay, good reversibility, and stable performance during long-term cycling, and has good market application potential. Further research is needed to characterize and analyze the microscopic morphology, element distribution, and structural evolution after cycling of this material, in order to further reveal the fine structure and stability mechanism of the hetero-interface.

Abstract:The accurate determination of lead in tungsten ores is of great significance for resource evaluation and beneficiation-metallurgy process control. However, the analysis of high-content lead in high-tungsten matrices has long been challenged by the occlusion of Pb^{2 +} during tungstic acid precipitation and serious interferences from coexisting ions such as Fe³⁺ and Al³⁺. Existing standard analytical methods are mainly suitable for samples with low tungsten or low lead contents and cannot meet the demand for rapid and accurate determination of medium-to-high lead ( >5%) in high-tungsten ores. To address this issue, based on the principle of coordination chemistry, a synergistic tungsten-control system using a tartaric acid-sodium citrate dual masking agent was constructed, and a rapid EDTA titration method was established for the determination of lead in high-tungsten ores. Tartaric acid preferentially complexes W(VI) to form soluble [WO₂(C₄H₄O₆)]^2-, effectively inhibiting the formation of tungstic acid precipitate with an inhibition rate greater than 98%. Sodium citrate selectively chelates Fe³⁺/Al³⁺, eliminating the influence of their hydrolysis on the titration endpoint. The optimal synergistic effect is achieved at a 1:1 ratio of the two masking agents. The optimized determination conditions are as follows: tartaric acid to sodium citrate ratio of 1:1 (total concentration 50 g·L^-1), pH range 5.5-6.0, and masking time 90 s. Under these conditions, spiked recovery experiments showed recoveries of 97.8%-100. 2% (average 99.1%) with a relative standard deviation (RSD) not exceeding 2.1%. Tungsten content interference experiments confirmed that when the WO₃ content is ≤ 200 g·L^-1, the recovery remains above 99. 5% with RSD ≤1. 8%; even when WO₃ reaches 300 g·L^-1, the recovery is still 97.8% (RSD 2.1%), markedly superior to the <95% of traditional methods. Interference test results demonstrate that the relative error is far below 2% under single-element interference of Fe³⁺ or Al³⁺, and it remains below 2% under multi-element synergistic interference (coexistence of Fe^{3 +}, Al^{3 +}, and WO₃). For special interfering elements such as Sb³⁺ and Bi³⁺, complete masking can be achieved by adding only 0.2 g of thiourea, with the relative error decreasing from 0.9% to 0.2%. Six replicate determinations of actual high-tungsten ore samples yielded a standard deviation of 0.02%~0.04% and RSD≤1.3%, and the method exhibited good applicability to samples with varying tungsten contents. This method fills the technical gap in current standards for the determination of high-content lead, effectively solves the problem of Pb²⁺ occlusion in H₂WO₄ precipitate in traditional methods, and provides a new technical solution for the rapid and accurate determination of high-content lead in tungsten ores.

Abstract:The wastewater from synthetic dye industries contains substantial amounts of Congo Red (CR) and Amaranth (AM), which pose significant toxic threats to ecosystems. Consequently, magnesium-based adsorbents have been widely applied for the treatment of such dye-containing wastewater. Approximately 50% of magnesite ore is converted into tailings during mining and processing. These tailings, which contain about 40 wt% MgO, are mainly disposed of by landfilling. In this study, magnesite tailings were employed as a precursor to synthesize a structurally stable MgO-based adsorbent through electrochemical deposition. CR and AM were chosen as representative anionic dyes to assess the adsorption performance of the adsorbent. The main conclusions are summarized as follows. The primary crystalline phase of the product obtained under optimized electrolysis conditions was MgO, with a trace amount of S₂₄Mg₁₆Ca₁₂O₉₆, which facilitated the adsorption process. The product exhibited a flocculent morphology with uniformly dispersed particles, which could be attributed to the enhanced steric hindrance induced by Ca and S co-doping. The prepared adsorbent exhibited a specific surface area of 74. 43 m2/g, an average pore diameter of 22. 66 nm, and a pore volume of 0. 0027 cm3/g, and the pore-size distribution was centered at approximately 20 nm, confirming its mesoporous nature. Under optimal conditions (adsorbent dosage = 10 mg, initial CR and AM concentrations = 500 mg/L, pH = 7-11, and contact time = 50 min), the maximum adsorption capacities for CR and AM reached 995. 66 mg/g and 759. 56 mg/g, respectively. Coexisting ions such as Cl?、SO₄^2- 和 NO₃^- showed minimal influence on adsorption efficiency, while HCO₃^- and humic acid (HA) exhibited only minor effects. The adsorption process was dominated by multilayer adsorption, with the kinetic data fitting well to the pseudo-second-order model. The adsorbent showed excellent regeneration performance, retaining CR and AM removal efficiencies above 95% and 68.5% after five successive cycles. The adsorption of CR and AM onto MgO was mainly governed by electrostatic interactions and hydrogen bonding. Meanwhile, the incorporation of S₂₄Mg₁₆Ca₁₂O₉₆ further enhanced the structural stability and surface reactivity of the adsorbent, thereby improving its overall adsorption performance compared with pristine MgO. The magnesium-based adsorbent prepared via this method exhibited high adsorption capacity, fast adsorption rate, and excellent reusability. Moreover, its synthesis did not require high-purity precursors, templates, or additives, providing a promising strategy for the resource utilization of magnesite tailings.

Abstract:The safe treatment of low and intermediate level radioactive waste remains an unresolved challenge in nuclear energy development, particularly in the case of radioactive strontium, which is readily absorbed by living organisms and accumulates in bone tissue, posing a serious threat to human health. In this study, experiments were conducted using a plasma high-temperature melting engineering prototype for low-level waste, developed by the Southwestern Institute of Physics, to investigate the application of plasma vitrification technology in treating radioactive waste from nuclear power plants, with a specific focus on the stabilization of radioactive strontium (Sr). Experimental results indicate that the prototype system has a processing capacity of approximately 50 kg/h and operates stably under continuous conditions. The temperatures of the primary and secondary combustion chambers were maintained at approximately 727.7℃ and 919.3℃, respectively. Fluctuations in temperature following the introduction of simulated waste were minor and had negligible impact on process stability. In the solidified products, over 60% of Sr was incorporated within the glass matrix, demonstrating effective stabilization. Trace amounts of Sr were detected in the emergency cooling tower wastewater and in the ash collected from the baghouse filter, while particulate matter in the flue gas contained only minimal levels of Sr. Additionally, XPS analysis revealed that Sr within the vitrified product primarily exists in the form of strontium oxide and undecomposed strontium carbonate. These findings provide direct guidance for the practical engineering application of plasma high-temperature melting technology for the treatment of radioactive waste and hold significant scientific and innovative value. With further optimization of process parameters and equipment design, this technology is expected to become one of the effective solutions for treating low- and medium-level radioactive waste.

Abstract:In the boiling chlorination process of high titanium slag, segregation behavior of high titanium slag and petroleum coke is prone to occur, affecting the mass and heat transfer of the boiling chlorination process and the reaction rate. To address this issue, this study uses high titanium slag and petroleum coke as raw materials, with chlorine gas as the fluidization medium. The Grace formula and Gupta formula are employed to calculate the initial fluidization velocity and the complete fluidization velocity, respectively. Based on the Eulerian two-fluid model and the drag force model, numerical simulations are performed, and the velocity contours under different correction factors for the complete fluidization velocity, the volume fraction distribution of particles at different heights, and the dynamic characteristics of bubbles are analyzed. The following main conclusions are obtained. The calculated complete fluidization velocity is 0.157 m/s. The simulation results indicate that at this velocity, only a stable bubble phase is initially formed above the distributor plate within the bed, making it difficult to generate significant particle disturbance effects. A uniform mixing can be achieved at a gas velocity corresponding to a correction factor of 1.6 times. Radial analysis of the bed shows that as the fluidization time (1.0~3.0 s) increases, the gradient of particle volume fraction gradually weakens, and the lateral distribution tends to become uniform, confirming that turbulent mixing has an inhibitory effect on segregation. Bubble behavior is the root cause of segregation. During the rise of bubbles, petroleum coke is entrained and carried to the bed surface, leading to the segregation of high titanium slag towards the bottom and petroleum coke towards the top during the boiling chlorination process. The results of this study can provide a theoretical basis and technical reference for improving the reaction rate and operational stability of the boiling chlorination process of high titanium slag.

Abstract:A combined approach of CFD simulation and heat transfer experiments was employed to investigate the heat transfer performance of a double-layer rotary variable-pitch three-bladed impeller within a stirred tank equipped with a spiral coil heater, using a 0.75% mass fraction CMC solution (a pseudoplastic non-newtonian fluid) as the medium. The findings indicate that the temperature distribution within the reactor follows a descending order: lower section>middle section>upper section, with the overall temperature difference maintained within 3.5 K. The strong axial flow generated by the rotary variable-speed three-bladed impeller effectively mitigates temperature variations at the reactor's top and bottom, keeping the maximum temperature difference below 2.5 K. Increasing the rotational speed enhances the kinetic energy of the flow field and heat transfer efficiency. When the rotational speed N=180 r/min, the small vortices at the bottom of the reactor disappear, and symmetrical circulating vortices form in the flow field, enhancing axial flow and overall mixing; Properly setting the paddle spacing is crucial for maintaining efficient axial circulation within the reactor. When the paddle spacing C₂=175 mm, the Nu reaches its peak, resulting in optimal heat transfer performance; The average temperature boundary layer thickness on the XY plane outside the spiral coil was 2.44 mm. The minimum discrepancy between experimental and simulated Nu values for the Nusselt number Nu on the coil's exterior was 2.62%, with a maximum error of 5.78%, validating the numerical simulation's accuracy. These findings provide reference for practical engineering applications of the rotary variable three-bladed impeller.