China Nonferrous Metallurgy

Abstract:Superalloys have been widely used in aerospace, aviation, energy and other high-end manufacturing industries. A large amount of waste superalloys are produced every year. The purification and regeneration technology of waste superalloys is of great significance to promote the healthy development of Chinas high-tech industry. Research indicates that inclusions insuperalloys alloys primarily originate from chemical reactions during the melting process, elemental contamination from service environments, and foreign impurities introduced during processing and storage. These inclusions can be categorized into various types such as oxides, sulfides, and nitrides based on their composition and morphology. The presence of these inclusions significantly degrades the mechanical performance, corrosion resistance, and fatigue life of materials, potentially leading to failure in critical components.In response to this issue, this paper focuses on a comparative analysis of the advantages and disadvantages of six mainstream purification processes, including mechanical grinding, electroslag remelting, vacuum induction melting, foam ceramic filtration, electron beam melting, and bottom-blown bubble flotation technology. Among these methods, mechanical grinding is suitable for the removal of surface inclusions; it is cost-effective but has limited processing depth. Electroslag remelting can effectively eliminate large-sized inclusions; however, it poses challenges due to high energy consumption. Vacuum induction melting significantly reduces oxygen and nitrogen content but generally shows moderate effectiveness in removing already formed inclusions. Foam ceramic filtration demonstrates excellent interception capabilities for micron-sized inclusions but is classified as a consumable process. Electron beam melting offers outstanding purification results yet involves complex equipment and substantial energy requirements. Lastly, bottom-blown bubble flotation exhibits high efficiency in removing small-sized inclusions; nevertheless, its process stability requires further improvement. In the future, the research on the recovery of waste superalloys should focus on the development of new composite purification processes with high efficiency and low consumption, improve the continuity and automation level of the process, and suggest the establishment of a sound waste recovery system.

Abstract:Waste circuit boards (WPCB) contains a large number of valuable metals and organic matter and glass fiber, of which the copper content accounts for a relatively high proportion of copper recovery in WPCB can not only alleviate the problem of shortage of copper resources, but also solve the problem of environmental pollution of WPCB. Currently, most of the research focuses on the recovery of valuable metal resources in WPCB, and less attention is paid to the organic matter in the non-metallic part. Brominated flame retardants in non-metallic components are dangerous carcinogens, and it is especially necessary to immobilize or recycle bromine in the metal recycling process.The treatment methods of WPCB include pyro-metallurgical process, mechanical treatment, hydrometallurgical process, pyrolysis, microwave treatment technology and biological treatment technology. Among them, although the pyrometallurgical process is the most widely used, the recycling process will produce toxic and hazardous substances, and the process needs to be improved; the separation effect of the mechanical treatment method is not ideal, and it is often used in the pre-treatment of WPCBs; the hydrometallurgical process produces more wastewater, and it needs to be equipped with the corresponding wastewater treatment system; the pyrolysis method can recycle the organic matter and energy, and the recovery of valuable metal resources is high, and it is simple, and it can suppress the production of harmful substances, such as dioxin, and the application prospect is more promising. and other harmful substances, the application prospect is better; microwave treatment technology and biological treatment technology is still in the laboratory stage, need to be in the process parameters, leaching mechanism research, engineering application of in-depth research, to promote the industrialization of the application. In the future, improving the recycling value of non-metallic substances, simplifying the process, reducing the pollutants generated in the recycling process, and studying the migration mechanism of bromine are the research directions for the recycling of WPCB.

Abstract:The patent technology of selenium purification and preparation is an important path to understanding the research progress of purification technology for selenium. This article conducts a statistical analysis of patents related to selenium purification and high-purity selenium preparation, summarizes domestic and foreign selenium purification and high-purity selenium preparation technologies, and the advantages and disadvantages of purification processes were discussed. Globally, China and Japan are the main countries for patent applications in selenium purification and high-purity selenium preparation technology, and the patent application units in this field in China are mainly concentrated in Yunnan Province and Guangdong Province. The hydrometallurgical purification process, combined pyrometallurgical and hydrometallurgical processes, and vacuum distillation process are suitable for purifying selenium containing materials to prepare selenium products with a selenium grade of ＜99.9%. Among them, the combination of vacuum distillation with oxidation to remove tellurium, melting and slagging processes can achieve good separation of selenium and tellurium, which has industrial application prospects for it's simple equipment and low cost ; The oxidation volatilization process is suitable for purifying and preparing 4N and above selenium products, which has a high recovery rate, but the adaptability for raw materials is poor, and the degree of automation of the volatilization equipment is low, automation and environmental improvement are the improvement direction in future. The regional melting process is suitable for preparing 5N and above high-purity selenium, but it has high equipment requirements, small processing scale, low adaptability to raw materials, and limited patent applications and research. In the future, a single purification technology will be difficult to preparing of high-purity selenium, and the combination of multiple purification processes will be the development direction for preparation technology of high-purity selenium. In addition, equipment automation and intelligence will also be the focus of research and development in the fields of selenium purification and high-purity selenium preparation.

Abstract:Solid oxide fuel cell (SOFC) electrolyte, a crucial channel for ion transport, plays a key role in reducing operating temperature and improving electrochemical efficiency of SOFC. According to the operating temperature of SOFC, the electrolyte materials are divided into high temperature electrolyte (＞850℃), medium temperature electrolyte (650~850℃) and low temperature electrolyte (＜650℃). Yttria-stabilized zirconia (YSZ) is the most widely used ion-conducting electrolyte in high-temperature electrolytes. Due to its limited oxygen-ion conductivity, the cell experiences rapid degradation at elevated temperatures. Both scandium stabilized zirconia (ScSZ) and LaGaO3-based electrolytes are suitable for intermediate temperature SOFC. The commercial viability of ScSZ electrolytes is constrained by prohibitively expensive raw materials. LaGaO3-based electrolyte is synthesized by various elements,which tends to form impurity phases, raising the materials internal resistance. Cerium oxide-based (GeO2) materials and bismuth oxide (δ-Bi2O3) materials with cubic fluorite structure have stable ionic conductivity at low temperature. However, both materials undergo reduction in redox conditions, causing electronic leakage and cell short-circuiting. BaCeO3-based proton conductors remain at an early development stage, with complex doping mechanisms requiring further optimization. Future electrolyte research must simultaneously address four critical challenges: temperature reduction, phase stabilization, conductivity enhancement, and production cost minimization.

Abstract:Aiming at the problems of high acid consumption and high energy consumption in the current process of recycling waste lithium ion batteries, this paper conducted a nickel cobalt manganese leaching test with waste 523 nickel cobalt manganese cathode material after electrolysis as raw material and sulfuric acid + hydroxylamine hydrochloride as the leaching agent. The influence of each process condition on the leaching rate was investigated, and the positive electrode material before and after leaching was characterized and analyzed. The kinetics analysis of the leaching process was also carried out, and the following main conclusions were obtained. The optimal leaching conditions of the system were as follows: hydroxylamine hydrochloride concentration 1.5mol/L, sulfuric acid concentration 1mol/L, leaching temperature 75℃, liquid-solid ratio 25mL/g, leaching time 60min. The leaching rates of nickel, cobalt and manganese were 96.84%, 99.87% and 97.35%, respectively. XRD analysis shows that there is almost no peak after leaching, and only weak peak shift of NiO and MnO2. SEM analysis shows that the positive electrode material presents small pieces of broken powder after leaching, indicating that the valuable metal in it has been leached. The study of leaching kinetics showed that the leaching process in this experiment was suitable for fitting by Avrami equation. The activation energies of nickel, cobalt and manganese were 8.3779kJ/mol, 4.6836kJ/mol and 4.9614kJ/mol, respectively. The leaching temperature had little effect on the reaction rate constant, and the leaching process was controlled by diffusion conditions. The results of this study provide an effective wet leaching process for the recovery of waste lithium-ion batteries, and provide a reference for theoretical research and application in related fields.

Abstract:The desalted aluminum ash produced by the wet aluminum process is used as experimental raw materials. Alkaline roasting technology is used to treat the desalted aluminum ash to produce raw materials for electrolytic aluminum, improving the recycling value of the desalted aluminum ash, and realising the recycling of aluminum in the aluminum industry. Firstly, the theoretical feasibility of roasting treatment technology was analyzed from the perspective of thermodynamics, and the change of Gibbs free energy of α-Al₂O₃, MgAl₂O₄ and Na₂CO₃ reactions under different temperature conditions was investigated to determine whether chemical reactions occurred and the conditions of occurrence. The theoretical analysis results were verified experimentally by X-ray powder diffraction technology. On this basis, the effects of Na2CO3 dosage, roasting temperature and roasting time on aluminum recovery were studied. The results show that α-Al₂O₃ MgAl₂O₄ and Na₂CO₃ in desalted aluminum ash can react with Na₂CO₃ to produce sodium aluminate above 1000℃. Under the experimental conditions of roasting temperature at 1000℃, mass ratio of Al∶Na₂CO₃ at 1∶2 and roasting time at 3.5h, the highest recovery rate of aluminum can reach 97.08%. It is feasible to recover aluminum from desalted aluminum ash by alkaline roasting, which is an effective way to recycle aluminum ash.

Abstract:Some zinc leaching residues used for silver flotation concentrates have high zinc content (Zn 18%-20%), which is not conducive to subsequent silver extraction. To solve this problem, this study first used a carbon-added microwave roasting process to pretreat the residues, aiming to increase zinc ferrite decomposition. Then, it used selective leaching under low-acid conditions, as oxidized zinc dissolves more easily than oxidized iron. This aimed to maximize zinc leaching and minimize iron leaching. Under the optimal carbon-added microwave roasting conditions of 1.2kW microwave power, 8% carbon addition, 700℃ roasting temperature, -150 mesh ore particle size, and 60-minute roasting time, the soluble zinc rate in the product reached 88.72%. Under the optimal selective leaching conditions pH 2 for the leaching solution, 5∶1 liquid-to-solid ratio, 70℃ temperature, and 90 minutes leaching time, zinc and iron leaching rates reached 88.53% and 41.68%, respectively. After microwave reduction roasting and low-acid leaching, about 93.5% silver in the raw material was enriched in the leaching residue, increasing its grade by approximately 2.3 times. The insoluble zinc in the material is mainly the undecomposed zinc ferrite, which is wrapped in the larger lead sulfate and calcium sulfate particles during the microwave roasting process and is difficult to leach.

Abstract:The residual organic phase in the tungsten-molybdenum stripping solution not only causes the loss of the organic phase but also reduces the recovery rate of tungsten and molybdenum. Macroporous resins have a porous network structure, large specific surface area, and hydrophobic oleophilic properties, which provide good adsorption for the organic phase. In this study, the SD300 macroporous resin was selected to conduct adsorption, desorption, and regeneration cycle experiments on the residual organic phase in the tungsten-molybdenum alkaline extraction stripping solution. The following main conclusions were obtained. Under the adsorption temperature of 20~40℃ and adsorption flow rate of 2~3BV/h, the resin organic phase breakthrough adsorption capacity was greater than 0.85g/mL, and the TOC removal rate was above 98.5%. Under the desorption temperature of 20~40℃ and desorption flow rate of 1BV/h, the ethanol dosage was less than 2.5BV, and the desorption rate was greater than 99%. After regeneration, the resin organic phase breakthrough adsorption capacity was greater than 0.85g/mL. After 10 adsorption-regeneration cycles, the resin organic phase breakthrough adsorption capacity was 0.850g/mL, and the TOC removal rate was 98.51%, with a decrease of 5.09% and 0.41% compared to the first cycle, respectively. The resin regeneration performance was good. When the ratio of the resin desorption liquid to the blank organic phase of the alkaline extraction was 1/100, the tungsten content in the loaded organic phase was 35.06g/L, and the molybdenum content was 3.53g/L. This method is suitable for high-salt solutions with high tungsten and molybdenum content, and it has a large processing capacity, high adsorption efficiency, simple desorption operation, low energy consumption, and the resin can be recycled. It fundamentally solves the problem of insoluble oily sludge in the tungsten-molybdenum extraction process and improves the recovery rate of valuable ions such as tungsten and molybdenum.

Abstract:In the aluminum electrolysis production process, the addition amount of aluminum fluoride plays a key role in maintaining the efficiency and stability of electrolysis. At present, it is mostly determined by experience. In fact, it has a complex nonlinear relationship with many factors such as alumina test data, aluminum level and electrolys temperature, showing dynamic changes, and it is difficult to make accurate decisions based on experience alone. This study addresses the challenges posed by the nonlinear, large time-delay, and strong coupling characteristics of the aluminum electrolysis process by integrating a soft attention mechanism into a BiLSTM network to construct a high-precision prediction model for aluminum fluoride dosage. Extensive data training, testing, and validation were conducted to ensure model reliability. The experimental results demonstrate that the proposed algorithm achieves exceptional prediction accuracy in estimating aluminum fluoride dosage. By leveraging the XGBoost algorithm to extract local features, the model enhances both prediction accuracy and operational efficiency. Furthermore, the integration of bidirectional LSTM enables the model to consider both forward and backward data dependencies, while the attention mechanism dynamically adjusts feature weights, further improving prediction performance. The XGBoost-BiLSTM-Attention model achieves an average error of 0.014, an average percentage error of 2.64%, and a linear fitting degree of 0.963, surpassing the overall performance of existing models. This prediction model provides significant decision-making support for precisely controlling aluminum fluoride dosage in aluminum electrolysis production, thereby enhancing production efficiency, reducing energy consumption, and achieving precise control.

Abstract:The emission levels of dust, nitrogen oxides (NO_x), and dioxins serve as critical indicators for evaluating flue gas purification efficiency in waste incineration power generation. By integrating the capabilities of a deNO_x catalyst and a dust collector, the pursuit of a multifunctional material that can simultaneously and efficiently eliminate dust, NOx, and dioxins can significantly streamline the flue gas purification process. Drawing upon the concept of composite structures, a novel composite functional filter material was developed, combining a VMo/CeTi-based low-temperature deNOx catalyst with a PTFE filter cloth. This study investigated the impact of the composite structure on the catalytic performance of low-temperature NH₃-SCR, the degradation of dioxin model compounds such as furan and 1,2-dichlorobenzene, and the efficiency of dust removal. Particular attention was given to the material's stability in the presence of moisture and sulfur compounds. The findings reveal that the composite functional filter material exhibits excellent performance in low-temperature NH₃-SCR and the degradation of dioxin model compounds, along with a strong tolerance to water vapor and SO₂. Upon conducting a series of characterization analyses, it was determined that the catalyst supported on the functional filter material with a composite structure exhibited excellent stability. The catalysts shedding rate was merely 0.2% following 500 injections, indicating a robust adherence to the substrate. Additionally, the catalyst powder was uniformly distributed, facilitating the exposure of more active sites. Consequently, the catalyst maintained its deNO_x performance and the degradation of dioxin model compounds. Simultaneously, the electron transfer, consumption, and regeneration of hydroxyl radical structures, along with the water generation resulting from the valence state cycling of active components during NH₃-SCR reactions, were found to enhance the hydrolysis and ring-opening of dioxin model compounds. This, in turn, achieved a synergistic elimination of NO_x and dioxins.The flexible PTFE filter cloth (PTFE fiber) matrix offers superior dispersion for catalyst powder while also leveraging its surface hydrophobicity to minimize the impact of water vapor on the catalyst. This reduction in turn decreases the production of toxic sulfites (sulfates), enhancing the water resistance of the composite structure functional filter media and extending the lifespan of the materials. Furthermore, experiments on SO₂ tolerance have demonstrated that the incorporation of Ce additives can effectively suppress the formation of nitrates and ammonium sulfates, exhibiting a high level of SO₂ tolerance. Hence, the development of advanced composite functional filter materials capable of removing dust, nitrates, and pollutants is crucial for advancing the market adoption of short-process flue gas purification technology.

Abstract:As a key precursor for preparing lithium manganate, a cathode material for lithium-ion batteries, battery-grade manganese dioxide holds an important position in the new energy battery industry due to its unique crystal structure and electrochemical performance. However, traditional preparation methods have the drawback of high production costs. In this study, using the acid leaching solution of rhodochrosite from Kebang Manganese Industry as the raw material, battery-grade manganese dioxide was prepared through a process of preliminary impurity removal-deep impurity removal-oxidation precipitation. The purification process of the rhodochrosite acid leaching solution was deeply studied, and the effects of various factors in the oxidation precipitation process of the manganese purification solution on the preparation of battery-grade manganese dioxide were investigated in detail. The results showed that during the preliminary impurity removal, the addition of ammonium bicarbonate-sulfuric acid solution for the precipitation and redissolution of Mn and Mg enriched the Mn concentration to 122.5g/L and reduced the Mg concentration to 91.5mg/L. The concentrations of Cl, Na, K, and Si were significantly reduced to 6.2mg/L, 16.8mg/L, 2.3mg/L, and 9.8mg/L, respectively. In the deep impurity removal process, the addition of 1.0g/L BaS and 4.2g/L MnF₂ to remove heavy metals and Ca, Mg reduced the concentrations of Mg and Ca to 21.3mg/L and 11.6mg/L, respectively. The concentration of Pb was reduced to 1.3mg/L, and the concentrations of Zn, Ni, Cd, and Cu were all reduced to less than 1mg/L. The process conditions for preparing battery-grade manganese dioxide by direct oxidation were as follows: at a Mn concentration of 1mol/L, with oxygen as the oxidant, 2% ammonia water as the neutralizer, and a reaction temperature of 70℃, the reaction time was 12hours. After washing the product with 2% ammonia water and drying, spherical battery-grade manganese dioxide with a Mn content of 71%, a specific surface area of 0.813m²/g, a tap density of 2.53g/cm³, and a median particle size of 12.5μm, and with impurity content lower than the national standard was obtained.

Abstract:This study systematically investigates the electrochemical behavior of Co²⁺ in a choline chloride-ethylene glycol system and its impact mechanism on the preparation of Ni-Co alloy. Analysis via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV) revealed that increasing Co²⁺ concentration significantly enhances its redox reaction activity. The charge transfer resistance (Rct) decreases in the negative potential region, confirming that a high-concentration system facilitates electron transfer and promotes Co²⁺ reduction. Fitting LSV data with the Levich equation demonstrated a positive correlation between the diffusion coefficient (D) and Co²⁺ concentration. Characterization and analysis of the electrochemically co-deposited Ni-Co alloy showed that scanning electron microscopy and transmission electron microscopy (SEM/TEM) analyses indicated an increase in the nickel-to-cobalt ratio of the coating with rising Ni/Co concentration ratio in the electrolyte. X-ray diffraction (XRD) analysis confirmed that the Ni-Co alloy possesses a single-phase solid-solution structure, with Co atoms occupying Ni lattice sites in a substitutional manner without forming intermetallic compound phases.

Abstract:Iron fluoride (FeF₃) has emerged as a promising cathode material for lithium-ion batteries due to its high voltage, high capacity, and low cost. However, its highly insulating nature severely limits the effective utilization of its lithium storage capabilities. Nanostructuring can shorten lithium-ion diffusion pathways and effectively enhance the electrochemical activity of iron-based fluorides. Nevertheless, current synthesis methods rely on complex liquid-phase reactions and high-temperature treatments, making industrial-scale production challenging. This study employed constant potential electrolysis in an ammonium hydrogen fluoride (NH₄HF₂) solution to directly synthesize nanostructured iron fluoride cathode material. The electrochemical oxidation pathway of metallic iron in the NH4HF2 solution was elucidated using polarization curves and cyclic voltammetry techniques. The main conclusions are as follows: Polarization curves and cyclic voltammetry tests revealed characteristic oxidation potential peaks at -0.58V (Fe-2e→Fe²⁺) and 0.01V (Fe²⁺-e→Fe³⁺). Controlling the anode potential at 0.01V for 1 hour of constant potential electrolysis at 25℃ successfully synthesized iron fluoride material. The primary particles of the synthesized material exhibited granular and needle-like morphologies, with particle sizes below 100nm. This material delivered an initial discharge specific capacity of 220.2mAh/g at 0.1C within the voltage range of 2.0~4.5V. It demonstrated a capacity retention rate of 91.5% after 100 cycles, reaching a performance level comparable to carbon-coated materials.

Abstract:The size of alumina inclusions significantly affects the properties of steel, and the properties of steel can be enhanced by refining or eliminating the inclusions. The modification process of inclusions was simulated through adding different proportions of rare earth oxides La₂O₃/CeO₂ and Al₂O₃ at 1200℃ and 1600℃. The modification processes of La, Ce and Al oxides were characterized via X-ray diffraction and Raman spectroscopy. The half-height and width data of XRD peaks were calculated by using Jade 6 and Halder-Wagner (H-W) model to calculate the average grain size after sintering. The results indicate that under the conditions of Al₂O₃:(Al₂O₃+La₂O₃) being 0.4 and a sintering temperature of 1600℃, La shows the best modification effect on alumina inclusions. The characteristic peaks of the product AlLaO₃ are significantly enhanced, with no characteristic peaks of La₂O₃ observed, and the characteristic peaks of Al₂O₃ are noticeably weakened. The minimum grain size of the sintered product is 0.1347μm. Under the conditions of Al2O3:(Al₂O₃+CeO₂) being 0.4 and a sintering temperature of 1600℃, Ce demonstrates the best modification effect on alumina inclusions. The main sintering products are CeAlO₃, CeO₂ and Al₂O₃ and the characteristic peaks of the product CeAlO₃ are also significantly enhanced. The minimum grain size 0.5261μm. Both La and Ce can effectively improve alumina inclusions, undergoing processes of encapsulation, gradual substitution, and phase transition, ultimately transforming irregular, angular Al₂O₃ into nearly spherical, oval, or block-shaped rare earth aluminates. La exhibits a better modification effect on alumina inclusions compared to Ce.

Abstract:To analyze the root cause of the great difference between the synthetic slag (slag prepared by chemical reagent) and premelted slag (molten slag in enterprise smelting) for physicochemical properties of PbO-Fe_xO-CaO-SiO₂-ZnO, the loss law of slag volatile for premelted slag and synthetic slag with the same composition with the 61.3% PbO are determined by FactSage and thermogravimetry, further, the volatile mechanism of lead slag is analyzed through combinate XRD and SEM-EDS analyze the final slag. The results shown that the volatilization of synthetic slag is more severe than that of premelted slag, synthetic lead slag had volatilized 12.7% before melting, and the main phase is Spinel of high melting point after volatilizing. But leads in premelted slag exists in the silicate is limited by the three-dimensional diffusion of silicate, which lead to a small amount of volatilization reaching the melting temperature. The mechanism function of weight loss process at high temperature of premelted slag and synthetic slag respectively are controlled by three-dimensional diffusion spherical symmetry Jander equation and Z-L-T equation, and the average apparent activation energies are 478.6kJ·mol^-1 and 352.9kJ·mol^-1.

Abstract:Adsorption methods are widely used in the treatment of uranium-containing wastewater, and biochar is used to make adsorbents due to its advantages of low cost, no secondary pollution, good stability, and large specific surface area. Several scholars have used walnut shells to prepare biochar for removing pollutants from water bodies. However, due to limited binding sites and slow adsorption rates, the adsorption capacity of raw biochar for radionuclides is limited. Therefore, composite material technology is required to enhance the adsorption capacity of biochar. This study utilized zero-valent manganese (nZVMn) with strong reducing properties to modify walnut shell biochar, preparing biochar-loaded nano-zero-valent manganese composite material (nZVMn-WBC). The uranium removal capacity of the composite material was investigated through experimental conditions. The uranium removal mechanism of the composite material was explored using adsorption kinetics, reduction kinetics, isothermal adsorption models, and modern characterization techniques such as SEM, XPS, and XRD, leading to the following main conclusions. Under optimal experimental conditions of pH 5.5, material dosage of 0.01g, adsorption time of 90 min, initial uranium concentration of 300mg·L^-1, and room temperature, the maximum adsorption capacity of nZVMn-WBC reached 473.48mg·g^-1, indicating its promising application prospects for the efficient removal of U(Ⅵ）. Stability tests show that nZVMn-WBC has excellent anti-interference performance. The first four uranium removal performances are good, but the fifth uranium removal performance decreases, possibly due to material loss during the test and the destruction of surface functional groups by the resolving agent. In practical applications, this effect can be compensated for by increasing the dosage. The changes in the physical and chemical properties of nZVMn-WBC before and after uranium adsorption were analyzed, and it was concluded that the uranium removal process mainly relied on chemical adsorption, which was a surface monolayer adsorption method accompanied by a reduction process, as well as electrostatic adsorption and surface complexation between Mn-OH and U(Ⅵ）.

Abstract:Some studies suggest that TiO₂ can reduce the viscosity of the liquid phase and stabilize the β-C₂S phase during the calcination of cement clinker. Currently, there is a large amount of titanium-containing blast furnace slag stockpiled in China, which contains a significant amount of TiO₂ and cement raw material components. In this study, titanium-containing blast furnace slag and cement raw materials were taken as raw materials to preparebelite cement clinker with excellent dry shrinkage and chemical resistance properties, which was composed of largeamount β-C₂S and a small amount of C₃S. The study investigated the influence of titanium-containing blast furnace slag addition on the phase composition, microstructure, and hydration characteristics of the clinker, and conducted an in-depth study on the distribution pattern of Ti⁴⁺ in the clinker, leading to the following main conclusions. The addition of blast furnace slag enhanced the hydration activity of the clinker and increased compressive strength. The compressive strengths of blank cement mortar specimens cured for 3 days, 7 days, 28 days, and 90 days were 20.3MPa, 27.2MPa, 42.3MPa, and 53.8MPa, respectively. When 4% blast furnace slag was added, the compressive strengths increased to 34.6MPa, 40.5MPa, 57.6MPa, and 68.3MPa, respectively. The mechanism by which blast furnace slag enhanced the hydration activity of clinker was that the TiO₂ and MgO in the slag reduce and disrupt the silicon-oxygen network structure of the silica-rich liquid phase, thereby lowering the viscosity of the liquid phase. The results of the structural difference factor D and radius difference percentage C calculations indicated that, compared to other ions in the clinker, Ti⁴⁺ tends to replace Fe³⁺ and dissolve into the belite clinker phase, such as the intermediate phase C4AF. The solid solution of Ti⁴⁺ not only causes lattice distortion in the clinker phases, thereby enhancing hydration activity, but also inhibits the transformation of β-C₂S into γ-C₂S with no hydration activity, promoting the reaction between f-CaO and β-C₂S to form C₃S. This study provides a theoretical foundation for the efficient and clean utilization of titanium-containing blast furnace slag.

Abstract:Barium slag is widely used as a mineralizer for cement clinker. Numerous scholars have explored the influence of BaSO₄ on the structure and properties of cement clinker. However, as a hazardous waste, there is currently no literature investigating its impact on the mineral composition of clinker and the environmental safety of cement products. This study used barium slag as an additive to prepare ordinary Portland cement clinker, and analyzed the mechanism by which barium slag regulates the phase composition, microstructure, and hydration performance of cement clinker. It also explored the distribution form of Ba²⁺ in cement clinker and the mechanism of Ba²⁺ leaching from silicate cement clinker. The introduction of barium slag reduced the high-temperature viscosity of the liquid phase, promoting the formation of C3S, thereby promoting the formation of highly hydration-active 2BaO·SiO₂ (B2S), significantly improving the hydration performance of silicate cement clinker; Ba²⁺ replaces Ca²⁺ and dissolves in β-C₂S, stimulating its hydration activity and promoting the formation of highly hydration-active α-C₂S phases; the introduction of barium slag significantly enhances the compressive strength of cement mortar. After adding 4.5% barium slag, the compressive strengths of the specimens at 3 days, 28 days, and 90 days increased to 37.55MPa, 58.47MPa, and 73.55MPa, respectively; the cement mortar containing barium slag has a dense structure, which inhibits the penetration of acid solution into the sample interior through pores to leach out Ba²⁺, and BaO·SiO₂·H₂O and Ba(OH)₂ are physically encapsulated by hydrated calcium silicate gel, while hydrated calcium silicate can chemically bind Ba²⁺. The synergistic effect of these two mechanisms inhibits Ba²⁺ leaching, resulting in soluble Ba²⁺ levels in the mortar samples below the limit specified in the “Criteria for the Identification of Hazardous Wastes by Leaching Toxicity” (GB 5085.3—2007) (100mg·L-1). This study provides a basis for the clean and harmless utilization of barium slag.