Slag Components Research Articles

Enhance recovery mechanism of difficult to enrich copper oxide component in copper smelting slag: Sulfidization-xanthate flotation

Copper smelting slag (CS), which is often overlooked, is a valuable solid-waste resource for reclaiming copper. Flotation is the most cost-effective method for its recovery. While most of the copper fraction can be easily recovered utilizing xanthate collection. However, the recovery effect of copper oxide components is poor, resulting in the waste of a large amount of copper resources. The sulfidization-xanthate method has exhibited some efficacy in recovering CS, due to its high economic value. However, the mechanism of using this method to recover CuO from CS is still unclear. This study utilized CuO samples to explore the recovery mechanism of the copper oxide fraction in CS within the sulfidization-xanthate system. Density-functional theory (DFT) theory and X-ray photoelectron spectroscopy (XPS) elucidated the sulfidization mechanism on the CuO surface, revealing the S formation of a Cu-S chemical bond on the CuO surface via chemisorption. Cu(I)-S and Sn2−, are the key species in activating CuO. Thermogravimetry analysis (TGA) identified that the CuO sulfidized surface adsorption less water than CuO surface. Zeta potential, ultraviolet visible (UV) and fourier transform infrared (FT-IR) tests illustrated the adsorption of sodium butyl xanthate (SBX) collection, exhibiting increased xanthate adsorption after Na2S treatment. Molecular dynamics (MD) simulation indicated the relative concentration of water molecules on the surface of CuO sulfidized had decreased, while the SBX had increased. Flotation tests confirmed the recoverability of CuO using this method. The extended Derjaguin Landau Verwey Overbeek (EDLVO) theory illustrates that the adhesion between the CuO particles and bubbles is promoted. Overall, the sulfidization-xanthate method can enhance the recovery of CuO and provide theoretical guidance for practical production. It also lays the theoretical foundation for future studies.

Complex additive for improving the strength properties of heavy concrete based on industrial waste

The article presents the results of using a complex modified additive to improve concrete's physical and mechanical properties. The complex additive includes industrial production wastes: metallurgical slag and alcohol production wastes (post-alcohol bard). To stabilize the hydrogen index the alkali KON is included in the composition of the additive. A set of laboratory studies was carried out to measure the strength, absorption, and frost resistance of test specimens to assess the effect of the additive on the properties of concrete. A comparison of physical and mechanical properties was made for samples of different concentrations of slag. The ratio of slag components to cement was from 5 to 25% by the total mass of the binder, a multiple of 5%. The optimal composition of the mixture, with maximum strength values, corresponds to the percentage of slag 15%, post-alcohol bard 22.5 liters, and alkali 150 grams. In general, the results obtained from data points of the compared parameters showed consistent results with minimal variation in the data. The results obtained are of practical value related to the reduction of the cost of production of structural concrete with an increase in its strength indicators.

Valorization of Residue from Aluminum Industries: A Review.

Recycling and reusing industrial waste and by-products are topics of great importance across all industries, but they hold particular significance in the metal industry. Aluminum, the most widely used non-ferrous metal globally, generates considerable waste during production, including dross, salt slag, spent carbon cathode and bauxite residue. Extensive research has been conducted to recycle and re-extract the remaining aluminum from these wastes. Given their varied environmental impacts, recycling these materials to maximize residue utilization is crucial. The components of dross, salt slag, and bauxite residue include aluminum and various oxides. Through recycling, alumina can be extracted using processes such as pyrometallurgy and hydrometallurgy, which involve leaching, iron oxide separation, and the production of alumina salt. Initially, the paper will provide a brief introduction to the generation of aluminum residues-namely, dross, salt slag, and bauxite residue-including their environmental impacts, followed by an exploration of their potential applications in sectors such as environmental management, energy, and construction materials.

Application of waste gypsum as novel selective depressant in the flotation separation of apatite from dolomite

The accumulation of gypsum slag not only causes resource wastage, but also poses serious environmental hazards, therefore, utilizing the resources of the main components in gypsum slag is an imperative task. In this study, gypsum was used as an inorganic depressant for the flotation separation of apatite from dolomite through the selective adsorption of gypsum on the surface of dolomite. Micro-flotation experiments showed that sodium oleate exhibited a good ability to collect apatite and dolomite, but poor ability to collect gypsum. At pH 9.5, when 3.75 g/L gypsum was added to the slurry, the recovery of dolomite decreased from 76.77 % to 18.34 %, whereas that of apatite was 86.45 %. Atomic force microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy were employed to elucidate the adsorption characteristics of gypsum on the apatite and dolomite surfaces. The results showed that gypsum was selectively adsorbed on the raised particles on the dolomite surface and combined with the active sites of Ca and Mg metal ions. However, the adsorption of gypsum on the surface of apatite was weak and had little effect on the flotation performance. Density functional theory calculations showed that the O in gypsum reacted easily with Ca and Mg metal ions on the mineral surface. The adsorption energies of gypsum at the Ca and Mg sites on the dolomite surface were −81.97 and −86.18 kJ/mol, respectively, whereas the adsorption energy on the apatite surface was only −34.20 kJ/mol. Gypsum is the main component of gypsum slag, and this study provides a potential recycling method for gypsum slag resources.

Interphase migration and enrichment of lead and zinc during copper slag depletion

An interphase migration and enrichment model of lead and zinc during molten copper slag depletion was established. The occurrence of various components in copper slag was predicted using sulfur−oxygen potential calculations and confirmed through high-temperature experiments. The recovery rate of copper can reach 90.13% under the optimal conditions of 1200 °C, an iron to silicon mass ratio of 1.0, 3 wt.% ferrous sulfide, and a duration of 45 min. Lead (54.07 wt.%) and zinc (17.42 wt.%) are found in the flue dust as lead sulfate, lead sulfide, and zinc oxide, while copper matte contains lead (14.44 wt.%) and zinc sulfide (1.29 wt.%). The remaining lead and zinc are encapsulated as oxides within the fayalite phase.

Mineralogy of Zinc and Lead Metallurgical Slags in Terms of Their Impact on the Environment: A Review

This paper presents the results of a study of the mineralogical and chemical composition of zinc and lead metallurgical slags. These slags contain numerous elements, including toxic metals, which form conglomerates or multiphase intergrowths. The phase composition of slags is one of the main factors that determine their behaviour in weathering environments, that is, their ability to release metals when exposed to atmospheric factors. In this paper, the release of elements from slags and their mobility in a hypergenic environment is determined based on the results of leachability tests and on geochemical modelling, thus assessing the environmental impact of landfilled slags. The elements released from slags in the largest quantities are zinc and lead. Zn is leached out over a long period of time. It was found that after 12 years, the concentration of Zn in the eluate exceeds by 40 times the permissible value of 200 mg/kg for hazardous waste. The degree of leaching of lead from slags as a function of time (after 12 years), despite its significant solubility in water, is much lower than the degree of leaching of zinc. The most mobile phase components of slags in the studied hypergenic environment are the lead phases (anglesite and galena) and, to a lesser extent, the zinc phases (sphalerite and willemite). Anglesite and galena in almost the entire Eh-pH range, along with admixtures of elements, decompose into ionic forms: PbCl42−, Pb2+, and PbOH+. Sphalerite in the soil and water environment (oxidizing and acidic conditions) will decompose into the mobile ionic form Zn2+. Willemite, which is resistant to weathering, will undergo similar decomposition. It can therefore be assumed that the carriers of toxic metals are primarily lead sulphides and sulphates, zinc sulphides, and, less frequently, zinc, lead, and iron oxides.

Ground granulated blast furnace slag-modified magnesium phosphate cement used as grouting material: Workability, mechanical property and corrosion resistance optimization

Calcium oxide and alumina, which are significant components of ground granulated blast furnace slag (GGBS), can participate in the hydration reaction with phosphate. This study examines the effect of incorporating GGBS as a mineral admixture on the fresh, mechanical, and durability properties of two-component magnesium phosphate cement (MPC)-based grouting materials. The findings reveal that GGBS replacement not only reduces the setting time and the heat released during hydration but also optimizes the fluidity of the fresh slurry at the appropriate replacement level. The optimal content of 20 % GGBS replacement significantly improves the mechanical properties of MPC grouts, achieving up to 28.4 MPa at 28 days, and enhances their resistance against the corrosion of water, chloride, and sulfate ions. XRD results show that the incorporation of GGBS leads to the formation of amorphous phases and secondary hydration products. These findings are corroborated by SEM analysis, which reveals gel-like new hydration products in matrices containing GGBS. Additionally, the incorporation of GGBS reduces the appearance of microcracks and gaps, resulting in a denser microstructure of the MPC matrix.

Slag after Smelting of Anode Mud: Role of Sulphiding Sintering

The study object was slag from the Balkhash copper smelter, obtained by re-melting anode mud containing nonferrous metals. The process flow for processing these slags includes sintering with Na2SO4, Na2CO3, and coal, followed by soda-alkaline leaching of the sinter and extraction of metals from the solution into marketable products. Since sintering is the main operation providing high selectivity, the composition of the products of this process was studied. The main transformations during sintering were determined, and the optimal parameters were identified. The structures of slags and sintered materials obtained during the experiments were studied by electron-probe microanalysis. Sintering was performed at 600–800 °C. The best results for sulphidization of slag components were obtained at 800 °C; a further increase in temperature leads to the smelting of sinter particles and slows down sulphidization. The optimal quantities of additives, based on the weight of the slag, are Na2SO4—45%, Na2CO3—15%, and reducing agent—41%, with a sintering time of 2 h. These conditions enable the sulphidization of non-ferrous metals in the slag to the entire depth of the polymetallic globules. The distinct concentration of harmful impurities (Ni, As, and Sb) was observed in the fine structure of the polymetallic globules.

Preparation of porous materials by ultrasound-intensified acid leaching of high-carbon component in coal gasification fine slag

Coal gasification fine slag is one of the by-products from clean and efficient utilization of coal, and its resource utilization is extremely urgent. In this work, a high carbon fraction with a fixed carbon content higher than 60% was obtained by simple sieving of gasification fine slag, from which a porous material was prepared by ultrasonic acid leaching method. The adsorption performance of porous materials, being used as treatment of radioactive iodine in nuclear wastewater, is characterized by iodine adsorption value. The effects of ultrasound time, ultrasound power, acid concentration, and temperature on the iodine adsorption performance and compositional structure of the porous materials were systematically investigated by combining the results of SEM, BET, XRD, and FT-IR. The mechanisms of ultrasound-enhanced acid leaching on compositional structure of residual carbon and migration and transformation laws of the ash constituents were explored and summarized. The results show that the porous material prepared under conditions of acid concentration of 4 mol/L, acid immersion temperature of 50 °C, ultrasonic power of 210 W, and ultrasonic time of 1.5 h has the best iodine adsorption performance of 468.53 mg/g, with a specific surface area of 474.97 m2/g, and possesses a rich pore structure with predominant mesopores. The order of each factor on the iodine adsorption performance is: sonication time > acid concentration > sonication power > acid immersion temperature. The mechanism of ultrasonic enhanced acid leaching is that ultrasonic cavitation and mechanical wave action firstly enhance dissociation of carbon-ash adherent particles, thus making desorption of ash particles blocked in pore channels of the gasification slag to increase its connectivity; secondly, lead to generation of cracks on surface of the carbon and ash particles to enhance accessibility of inorganic components inside the carbon particles; and thirdly, enhance the acid leaching process by increasing mass transfer rate to strengthen leaching effect of inorganic components in the gasification slag.

Kinetic Investigation of the Deep Desulfurization of 5 wt% Si High-Silicon Austenitic Stainless Steel

Given the demand for extremely low sulfur content in 5 wt% Si high-silicon austenitic stainless steel (SS-5Si), smelting utilizes a slag composition of CaF2-CaO-Al2O3-MgO-SiO2 with a basicity of 1 to 3, Al2O3 content ranging from 2.04 to 9.61%, and CaF2 content between 20.8 and 31.62%. Experiments designed to investigate the sulfur content in molten steel at temperatures of 1773 K, 1823 K, and 1873 K over durations of 1, 5, 10, 15, and 30 min, under varying slag compositions, corroborated with a theoretically derived model hypothesizing a “rate-controlling” step in mass transfer, revealed that the mass transfer of sulfur within the molten steel was determined to be the rate-controlling step (RCS) in the (CaO) + [S] = (CaS) + [O] reaction kinetics, and the variability of the mass transfer coefficient of sulfur, kS,m, in the molten steel ranged from 1.04 × 10−5 m∙s−1 to 2.24 × 10−5 m∙s−1. Based on the temperature dependency of kS,m, the apparent activation energy for the desulfurization reaction was estimated to be 96.03 kJ/mol. Considering the slag components, the binary basicity, denoted as R, exerted an overriding influence on the process of desulfurization. At a basicity of 1, the sulfur content within the liquid steel was reduced, from 22 ppm to 11 ppm within a time span of 30 min. In contrast, an increase in the basicity to a value of 3 showed a significant consequence: over an identical temporal duration of 30 min, the sulfur content was drastically reduced to 2.2 ppm. By contrast, an initial surge in desulfurization rates is observed within the first five minutes, attributable to relatively lower concentrations of Al2O3 and higher levels of CaF2. Subsequently, these parameters exert no significant influence on the kinetics of the desulfurization process.

Observations and simulations for separation mechanism of vanadium and chromium: Progressive study based on oxides, spinels and vanadium-chromium slag

In this study, V2O3-CaO-Cr2O3 oxides system, Fe2VO4-CaO-FeCr2O4 spinels system and V-Cr slag-CaO system were established progressively to investigate the separation effect of vanadium and chromium components in vanadium-chromium slag (V-Cr slag). Then, the separation mechanism was proposed by XRD, SEM and leaching experiments. The results show that the reaction ability of vanadium with calcium is far stronger than that of chromium. In oxides and spinels systems, as CaO increases, CaV2O6, Ca2V2O7, and Ca3V2O8 are generated sequentially. In V-Cr slag-CaO system, additive CaO, along with manganese, magnesium and iron components in V-Cr slag reacts with vanadium, resulting in the complex composition of vanadate. As to chromium component, Cr2O3 in oxides system will be converted into CaCrO4 as n(CaO)/n(V2O3) is higher than 2. Iron in the spinels system reacts with chromium and form solid solution (FexCr1-x)2O3, resulting in less chromium reacting with calcium to produce CaCrO4. In V-Cr slag-CaO system, SiO2 generated by the decomposition of silicate phase combines with part of calcium expected to react with chromium, making CaCrO4 generation more difficult, promoting the separation of vanadium and chromium further. Consequently, during H2SO4 leaching, chromium leaching ratios are 98.75%, 45.77% and 5.91%, respectively, in oxides, spinels and V-Cr slag system when n(CaO)/n(V2O3) is 5. And when n(CaO)/n(V2O3) is 2, more than 90% of vanadium can be leached, however, the leaching ratios of chromium are 0.22%, 0.17% and 0.094% in these three systems. Furthermore, the variation regularities of chromium leaching ratios with CaO amount are described by regression equations. These findings would provide the theoretical support for the calcification roasting process with V-Cr slag.

Study on the carbonation properties of BOFS with γ-C2S blending

β-C2S is the main active mineral component in Basic Oxygen Furnace slag (BOFS), while the content of β-C2S in BOFS is usually limited and fluctuated, which hindered the improvement of CO2 capture during carbonation. To enhance the carbonation reactivity of BOFS products, different ratio of γ-C2S was blended with BOFS powder and carbonated, followed by hydration curing. XRD and TGA analysis were used to determine the mineral composition of each blending group after carbonation. SEM analysis was applied to observe the microstructure, and the MIP method was used to analyze the pore size structure. The results show that the carbonation degree and compressive strength of BOFS cubes were increased by the addition of γ-C2S. With 20 wt% blending of γ-C2S, the carbonated BOFS obtained the optimum increasement of carbonation degree and compressive strength, reaching 39.3% and 42.4 MPa, respectively. However, the subsequent hydration reactivity of BOFS was inhibited when blended with 20 wt% of γ-C2S. Despite this, the increased poorly crystalline CaCO3 filled the system and densified the matrix, contributing to a 17.9% increase in compressive strength of SH20 after 56 days of hydration curing.

Analysis of Hydration Mechanism of Steel Slag-Based Cementitious Materials under Saline–Alkaline-Coupled Excitation

In order to realize the resourceful, large-scale, and high-value utilization of steel slag, which is a bulk industrial solid waste, and to reduce the use of cement-based cementitious materials, this study adopted the coupled excitation effect of sodium carbonate–magnesium oxide–desulfurization gypsum to excite steel slag-based cementitious materials, and it preliminarily investigated the hydration process of the steel slag-based cementitious system by the analysis of the heat of hydration of the cementitious materials and the pH value of the pore solution. The hydration products and microscopic morphology of the steel slag-based gelling material were initially investigated by XRD and SEM technical means on the gelling system. The results showed that the hydrolysis of the exciter and the dissociation of the active components in the steel slag provided an alkaline environment and relevant ions for the gelling system, which promoted the generation of the AFt and hydrotalcite phases. Subsequently, the AFt provided ungenerated sites for C-S-H gels as well as calcites, and the hydrotalcite phase accelerated the transformation of the carbonate phase in the gelling system, which promoted the synergistic effect of the hydration of the steel slag and mineral slag. Eventually, a large number of C-S-H gels, calcites, and other hydration products were generated in the gelling system under the synergistic effect of the hydration of the steel slag and slag, which was manifested in the improvement in the mechanical properties at the macrolevel. In addition, this study also standardized 28 d steel slag-based gelling for carbonization maintenance, and the data show that a carbonization temperature of 70 °C, CO2 pressure of 0.7 MPa, and carbonization time of 30 min achieved the best results, with a strength of up to 51.22 MPa, illustrating that steel slag-based gelling materials are safe and can be used for the green storage of CO2.

Effects of dicalcium ferrite on hydration and microstructure of cementitious material

Dicalcium ferrite (C2F) is a key component in metallurgical slag, particularly steel slag. Nevertheless, its influence on cement hydration is unclear. This study investigated the composition and surface properties of synthesized C2F and its effects on the compressive strength, hydration heat, hydration degree, and microstructure of blended cement. The results indicated that C2F comprises small lamellar particles. Its incorporation into Portland cement reduces the hydration rate and cumulative hydration heat of blended cement. Despite its low hydration capacity, C2F actively engages in cement hydration, reacting with C-S-H, C4Ac0.5H12, and C4AcH11 to form C3(AF)S0.84H. Furthermore, the loose, lamellar structure of C2F reduces the compactness of the microstructure in blended cement paste. Consequently, C2F imposes a more substantial retarding effect on cement hydration than inert SiO2. This investigation contributes novel theories and insights into the retarding effect of steel slag on cement hydration.

A deep insight into the dynamic crystallization of coal slags and the correlation with melt microstructure

In liquid discharging furnace, crystallization can occur in slags during the cooling process. The presence of crystal changes the structure, flow, heat transfer, especially the viscosity with a sharp increase. A deep understanding of the crystal kinetics is significant to optimize the flow of liquid slag. Crystal kinetics varies significantly with different slags due to the complexity and variability of the multi components in slags. In this paper, a high-temperature microscopy with high-resolution is used to clearly observe the in situ precipitation of different crystals and the kinetic parameters of different crystals are analyzed. Microscopic structure analysis of both the melt and the precipitated crystal shows that the proportion of basic oxygen structure and the diffusion coefficient of the basic cation in the melt have a direct correlation with the growth of crystal. A structural parameter St of the melt is developed, which has a positive correlation with the crystal growth rate. This is a new discovery in bridging the gap between the melt and precipitated crystals and it provides a way to control the crystal growth during slag cooling.

Effects of the Chemical Composition of Synthetic Slags Compared to an Average Blast Furnace Slag

AbstractTo study the effect of the main oxides and the minor components in slags on their reactivity as SCM, various glasses were synthesized to stepwise imitate a commercial slag of average chemical composition. First, a glass was produced from the main oxides CaO, Al2O3 and SiO2. In a second step, the minor components MgO, Fe2O3, Na2O and K2O were added separately to the main oxide mix. A selection of two synthetic glasses was tested for their compressive strength contribution (up to 90 days) by substituting 20 wt.% of cement. After all testing times, the synthetic slags achieved a strength similar to that of the commercial product. The reactivities determined by heat flow calorimetry (R3 test) correlate with the calculation of NBO/T and the results of 29Si MAS NMR showing that a decreased degree of polymerization enhances the reactivity. Apart from that, FTIR spectroscopy and 27Al MAS NMR indicate a similar structure of the original and the synthetic slags.

A quantitative method to assess and predict the exothermic behavior of steel slag blended cement

Steel slag blended cement exhibits distinctive exothermic behaviors from cement or fly ash/blast furnace slag blended cement. However, quantitative assessment and prediction are difficult due to the complex interactions between steel slag and cement in time scale, especially at the time when it exceeds the measurement accuracy of isothermal calorimetry. In this study, a quantitative method was proposed to assess and predict the exothermic behavior of steel slag blended cement using both quantitative experiments and kinetic/thermodynamic simulations. Contributions of components in steel slag blended cement to the total exothermic behavior in time scale were quantitatively revealed, and exothermic behavior of steel slag blended cement was interpreted in-depth. Results show that heat release by C3S at 1 d decreases by approximately 40 % in steel slag blended cement. Compared with that on C3S, steel slag has small effects on the exothermic behaviors of other cement clinkers. Calculated results agree well with calorimetric results, and prediction of the exothermic behavior was achieved.

Desulfurization Behavior of FeNi-Based Expansion Alloy Melt Using CaO-SiO2-MgO-Al2O3-CaF2 Slag

The effects of slag components on the sulfur distribution ratio {(wt.%S)/[wt.%S]} were analyzed using thermodynamic calculations. On this basis, the effects of the slag with different binary basicities (wt.% CaO/wt.% SiO2 = 3.0, 5.0, 7.0, 9.0 and 11.0) and Al2O3 contents (wt.% Al2O3 = 12, 16, 20 and 24) on the desulfurization behavior were investigated. The results show that the binary basicity and Al2O3 content were the main factors that affected the desulfurization. And an increase in the binary basicity and a decrease in the content of Al2O3, increase the sulfide capacity of the slag. In the early stage of the smelting process, the desulfurization process was limited due to the high content of oxides, such as FeO and MnO in the slag, and the sulfur content in the alloy melt reached 35 ppm. After the final deoxidation of the Si-Ca alloy, the desulfurization rate was significantly increased, and the maximum desulfurization rate reached 44.12%. During the ladle standing, the sulfur content in the alloy melt changed little because of the limitation of kinetics. The rate-limiting step of the desulfurization process was the diffusion of sulfur in the alloy melt.

Research Progress of Desulfurization Refining Slag: A Review

The development of refining slag is the core of the ladle furnace (LF) refining processes and is essential for fast and effective desulfurization refining. Desulfurization reactions are mainly determined by slag–steel interactions, which are closely related to the physicochemical properties of slags. This study reviews the research progress of desulfurization refining slag for the LF process. First, the chemical composition of the refining slag is described, and then three theories of desulfurization and the concepts of sulfide capacity and sulfur partition ratio are introduced. Second, the effects of operating parameters and slag components on desulfurization are examined. Furthermore, the microscopic analysis of the desulfurization process is performed. The prediction models of slag properties related to desulfurization are summarized. Finally, a research direction for LF desulfurization refining is proposed. The question of how to ensure the uniformity of desulfurization remains open. The industrialization of the new refining slag developed by replacing CaO with BaO or Li2O and replacing CaF2 with B2O3 should be accelerated to solve the CaF2 slag volatilization problem. One of the most pressing issues that must be addressed is improving the accuracy of the existing slag performance forecast model.

Utilization of copper slag in the fabrication of silica refractory: Characteristics and performance evaluation

AbstractIt is urgently necessary for environmental resource utilization of copper slag with incremental quantities of stacked copper slag. In this paper, copper slag has been used as mineralizer and raw material to prepare silica refractory. The effect of copper slag on phase composition, microstructure, mechanical, and load deformation performance has been investigated. The results indicate that the components of copper slag as mineralizer promote the formation of tridymite. Simultaneously, copper slag promotes the densification of silica refractory and glass phase increases due to the mineralizer and impurities in copper slag. The increased glass phase promotes the cold crushing strength and cold modulus of rupture for silica refractory, while the hot modulus of rupture slightly decreases by 1.5 MPa for 6 wt% copper slag. In addition, the load softening temperature and high‐temperature creep attains 1632.6°C and ‐5.5%, respectively. It is estimated that the potential application of silica refractory with copper slag on upper part of copper stove (low‐temperature and low‐load region) is acceptable in consideration of environmental utilization of solid waste.