Ladle slag, a by-product of steelmaking, presents a valuable strategy for waste reduction and valorization in wastewater treatment. This work demonstrates the successful simultaneous removal of ...Al(III), B(III), Ba(II), Cr(III), Mg(II), Sr(II), Pb(II), and Zn(II), from electroplating wastewater by ladle slag. First, Cr(III) and Pb(II) removals were evaluated in single synthetic systems by analyzing the influence of pH, temperature, and ladle slag dosage. Competitive removal was observed in binary batch experiments of Cr(III) – Pb(II), achieving 88% and 96% removal, respectively, with fast kinetics following a pseudo-second-order model. The findings of XRD, SEM, EDX, and FTIR of the slag after removal helped to elucidate the synergic removal mechanism involving ladle slag dissolution, precipitation, ion exchange, and adsorption in a tight relationship with the solution pH. Lastly, ladle slag was tested in real electroplating wastewater with the aforementioned ions at concentrations ranging from <1 to 1700 mg/L. The removal was performed in two steps, the first attained the following efficiencies: 73% for Al(III), 88% for B(III), 98% for Ba(II), 80% for Cr(III), 82% for Mg(II), 99% for Pb(II), 88% for Sr(II), and 88% for Zn(II). Visual MINTEQ simulation was utilized to identify the different species of ions present during the removal process. Furthermore, the leaching tests indicated a minimal environmental risk of secondary pollution in its application. The results promote an effective and sustainable approach to wastewater treatment within the circular economy.
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•Sustainable utilization of ladle slag is evaluated in wastewater treatment.•Heavy metal removal from electroplating wastewater was successfully achieved.•Simultaneous removal of contaminants by ladle slag involves a synergic mechanism.•Removal efficiency exceeded 90% for Cr(III), Pb(II), Zn(II), and other ions.
In this study, four ecotoxicological tests on Vibrio fischeri bacteria, Sinapis alba L. (white mustard), Daphnia magna S. (daphnia's) and earthworms were performed for three types of aqueous slag ...(ladle, blast furnace and converter) leachates with two-grain sizes (<4 mm, <10 mm). Concentrations of toxic elements and concentrations of Cr(VI), Ca, Na, Al, and other ions were determined. The raw slags were analyzed using X-ray fluorescence spectroscopy (XRFS), and major substances were determined by X-ray powder diffraction (XRD). The aqueous slag leachates passed ecotoxicological tests and met the required criteria, showing no toxicity to Vibrio fischeri and complying with white mustard test criteria. According to the results of the ecotoxicity tests with daphnia, the blast furnace slag samples were not ecotoxic, while two other slag samples were found to be entirely compliant. Characterization of the slags showed that the effect of element/ion leachability and slag grain size is essential. Biplot principal component analysis (PCA) showed that grain size does not significantly affect the separation of individuals on the plane. A positive correlation on toxicity was found with pH, conductivity, calcium content, dissolved content, salinity and fluoride concentration, whereas a negative correlation was found with magnesium concentration, dissolved organic carbon and potassium concentration. The effective concentration at 50% inhibition (EC50) value for Vibrio fischeri correlated with the first dimension of bivariate assessment. In summary, it was found that the investigated slags can be effectively reused as they comply with regulations and do not endanger the environment.
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•Ecotests on mustard, daphnia, Vibrio fischeri bacteria were compared with EU norms.•The chemical composition of the leachates affects the results of ecotoxicity tests.•Toxic unit values for Vibrio fischeri bacteria were within norms and non-toxic.•Most of the effective concentration values for the daphnia test were acceptable.•Principal component analysis found grain size effect on two organisms.
Due to its low hydraulic reactivity, ladle slag is currently underutilized with nearly 80% of annual generation is either landfilled or dumped. This work investigates the joint activation of LS with ...Class F fly ash, and the impact of ladle slag on fly ash geopolymer with the focus on activation, hydrates assemblage, conversion process, and thermal behavior. Results reveal that the unique reaction process of ladle slag in alkali activation system shows a positive influence on fly ash geopolymers. Within an alkaline system rich in soluble Si, the initially hydrated CAH phases transform into C-A-S-H, which not only hinders the conversion and enhances the mechanical strength but also retains the geopolymerization. The hybrid geopolymer system exhibits superior thermal performance to pure fly ash geopolymers, especially under high temperature exposure. With increasing ladle slag substitution, more stable crystalline phases are formed at high temperatures. After 800 °C exposure, a high residual compressive strength of 64.7 MPa is achieved with 25 wt% ladle slag addition compared to 55.2 MPa in pure fly ash geopolymers.
The gel compatibility in calcium contained geopolymers remains a controversial topic. This work aims to clarify the role of Ca availability in determining the geopolymerization of alkali-activated ...ladle slag/Class F fly ash blends. The results show that the product layer wrapping around slag particles largely governs the Ca diffusion into the environment, enabling the development of two separated gels, namely C-(N)-A-(S)-H and N-(C)-A-S-H type gel. A dense matrix consisting of geopolymer gel and Ca-enriched gel is achieved with 8 % of Na2O while increasing Ms. intensifies the incompatibility between two gels, leading to microcrack formation and lowered mechanical strength. The competition between different reaction mechanisms of the two gels predominates the initial properties and thermal performance of the hybrid binder. A thermal degradation model of hybrid geopolymer co-existing geopolymeric gel and Ca-enriched gel is proposed to describe the influence of gel compatibility on the thermal behavior of Ca incorporated geopolymer.
Ladle slag is a by-product of secondary steel treatment. A typical management option for ladle slag is stockpiling in open yards. Given the massive production quantities of such material, this ...disposal mechanism has posed major environmental concerns over the years. The construction industry is a potential area that may recycle ladle slag as a sustainable replacement to cement binder, thereby reducing the consumption of cement, conserving natural resources, and alleviating greenhouse gas emissions. Accordingly, this paper provides a state-of-the-art review of the generation, characteristics, and reaction mechanisms of ladle slag. The effect of utilizing ladle slag on the fresh and hardened properties and microstructure of alkali-activated mortar and cement-based conventional and self-compacting concrete is also reviewed. Findings highlighted that utilizing ladle slag by the concrete industry is possible with favorable properties when certain preprocessing measurements, such as milling, sieving, and gypsum addition, are implemented. Furthermore, it is concluded that the degree of reaction and performance of alkali-activated mortar and concrete are dependent on the curing temperature and the type and components of the alkaline activator solution. Also, the replacement of 20% cement with ladle slag does not compromise the strength and durability aspects of cement-based concrete. From an environmental perspective, ladle slag is considered a non-hazardous material suitable for use in construction applications. The research gaps in the existing knowledge and future research directions are also identified.
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•Generation, characteristics, and reactivity of ladle slag are summarized.•Various utilization schemes for ladle slag as a construction material are reviewed.•Environmental impact of using ladle slag in mortar and concrete is discussed.•Research gaps in the existing knowledge and future research directions are highlighted.
The disposal of ladle furnace slag (ladle slag, LS) containing traces of heavy metals produced during steelmaking has become an environmental issue. The use of LS as a binding material in civil ...engineering is a potential solution. In this context, this study firstly attempted to activate LS with sodium hydroxide (NaOH), sodium sulfate (Na2SO4), and sodium metasilicate (Na2SiO3), and then blended it with ground granulated blast-furnace slag (GGBS) with different LS:GGBS ratios. The chemical-activated LS pastes and LS-GGBS pastes were cured for different ages, and then subjected to a compressive strength test. The results indicated NaOH, Na2SO4, and Na2SiO3 could not effectively activate this LS, with 28-day strength <2 MPa, whilst the LS-GGBS yielded much higher strength, up to 15.6 MPa at 28 days. Only a very low concentration of Pb leached out from the LS-GGBS at 14 days, and none of the possible heavy metals were detected at 56 days. This indicates that LS-GGBS can be potentially used as a binding material in civil engineering. The X-ray diffraction (XRD) revealed that the Ca(OH)2 in LS acted as the main activator for GGBS hydration; the MgO and CaCO3 in LS seemed to play similar roles as that of the Ca(OH)2. The XRD, thermogravimetric analysis (TGA), fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), and energy dispersive X-ray spectroscopy (EDX) indicated that the main hydration product of LS-GGBS was calcium silicate hydrates (CSH).
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•NaOH, Na2SO4, and Na2SiO3 are not effective to activate ladle slag.•LS activates ground granulated blast-furnace slag (GGBS) effectively.•Ca(OH)2 in LS accelerates strength development of GGBS.•Hydration products of LS-GGBS immobilize heavy metals in LS.
Global sustainable development faces challenges in greenhouse gas emissions, consumption of energy and non-renewable resources, environmental pollution, and waste landfilling. Current technologies ...for immobilization of heavy metals face similar challenges; for example, the use of cement, magnesia, lime, and other binders for immobilization of heavy metals is associated with carbon dioxide emission and consumption of limestone/magnesite and energy. In these contexts, this study introduced a novel and sustainable method for immobilization of lead (Pb) by using an industrial solid waste (ladle furnace slag, LFS) and a greenhouse gas (carbon dioxide). In this laboratory investigation, LFS was first mixed with the lead nitrate and then treated by conventional curing (without carbon dioxide) and carbonation curing (with carbon dioxide) for different periods. The treated LFS were then analyzed by various chemical analyses and microanalysis. The results showed that LFS with conventional curing is not effective in immobilization of lead, while LFS with carbonation curing can effectively immobilize lead. The leaching concentrations of Pb from carbonated LFS were four orders of magnitude lower than those with conventional curing. LFS can achieve carbon dioxide uptake of up to 8% of LFS mass. During the carbonation process, carbonates were produced and wrapped LFS particles to prevent the release of lead, lead nitrate was also carbonated into lead carbonate, and the pH of LFS was reduced to 9.36–9.58, close to the minimum solubility of lead carbonate; these are the main reasons for lead immobilization. In summary, the use of LFS with carbon dioxide for immobilization of lead can not only sequester carbon dioxide, but also reduce the cost of binders, non-renewable resource consumption, energy use, and LFS landfilling.
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•Lead (Pb) is immobilized by ladle furnace slag (LFS) and CO2.•CO2 is sequestered and stored.•Binder cost for Pb immobilization is reduced.•LFS landfilling is reduced.•Consumption of non-renewable resources and energy are reduced.
Fe-rich alkali activated materials (AAMs) require detailed understanding of their durability prior to their real-life application in the construction industry. Three mixes were formulated with ...fayalite slag (FS) as the main precursor. The effect of incorporation of ladle slag (LS) or blast furnace slag (BFS) on the shrinkage and exposure to physical and chemical attacks representing environmental conditions in cold and tropical regions (acidic solution at room temperature and in freeze-thaw, combined sodium sulfate and sodium chloride solution at room temperature and in freeze-thaw, freeze-thaw in water and dry-wet cycles) was investigated via visual observation, mass loss, compressive strength, X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), and scanning electron microscope coupled with energy dispersive X-ray spectroscopy (SEM-EDS). Experimental results show the considerable role of incorporated LS and BFS in modifying the gels formed and controlling material degradation of blended AAMs after exposure. In contrast, sole FS-based samples were completely degraded particularly those exposed to freeze-thaw in water, acid, and combined sodium sulfate and sodium chloride solution, indicating their vulnerability to frost and chemical attacks.
•Durability of Fe-rich alkali-activated materials (AAMs) exposed to different environmental conditions was elucidated.•Sole fayalite slag-based AAMs were completely degraded during exposure to freeze-thaw in water, acid and combined sodium sulfate and chloride•Incorporation of ladle slag (LS) or blast furnace slag (BFS) helps to control AAMs degradation during exposure to aggressive environments.•AAMs containing LS or BFS exhibited better mechanical, microstructural and durability properties after exposure.•Deterioration of AAMs was caused by water and chemical uptake in the pores.
•Taguchi L16 matrix was used to design the experiments with five factors and four levels.•TOPSIS method was used to optimize alkali-activated ladle slag mortar constituents.•Four quality ...characteristics were used in the multi-criteria optimization method.•Taguchi-TOPSIS integration can optimize alkali-activated ladle slag mortar mix design.•Optimum mix compressive strength, workability, and initial setting time were 17.9 MPa, 177.5 mm, and 13 min.
This study examines the effect of various parameters on the properties of alkali-activated composites made with unprocessed ladle furnace slag. Taguchi method was used to design the experiments. A total of five factors, each with four levels, were considered, including ladle slag content (LS), alkaline-activator solution-to-binder ratio (AAS/B), sodium silicate-to-sodium hydroxide ratio (SS/SH), sodium hydroxide molarity (M), and crushed sand replacement by dune sand (CSR). A total of 16 alkali-activated ladle slag mixtures were designed, cast, and tested. The performance responses were the workability, setting time, and compressive strength. To assess the influence of the factors on the responses, Taguchi analysis and ANOVA were employed while determining the signal-to-noise (S/N) ratios. Further, TOPSIS analysis was carried out to optimize the mixture proportions of alkali-activated ladle slag composites. The optimum mix entailed 650 kg/m3 of ladle slag, AAS/B ratio of 0.45, SS/SH of 2, and CSR of 25% to maximize strength and workability. Meanwhile, the optimum mix to maximize workability and setting time included 650 kg/m3 of ladle slag content, AAS/B ratio of 0.6, SS/SH of 2.5, and CSR of 50%. Anticipated results of the optimum mixes were experimentally verified. Microstructure analysis of the optimum mixes (isothermal calorimetry, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy) highlighted the accelerated rate of the activation reaction, the amorphous morphology, and the formation of calcium aluminosilicate hydrate gel.
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