Lithium Slag Research Articles

Heavy metals immobilization of ternary geopolymer based on nickel slag, lithium slag and metakaolin

To solve heavy metals leaching problem in the utilization of various industrial solid wastes, this work investigated the heavy metals immobilization of ternary geopolymer prepared by nickel slag (NS), lithium slag (LS), and metakaolin (MK). Compressive strength was measured to determine the optimum and appropriate mix proportions. The leaching characteristics of typical heavy metals (Cu (Ⅱ), Pb (Ⅱ), and Cr (Ⅲ)) in acid, alkali, and salt environments were revealed by Inductively Coupled Plasma (ICP). The heavy metals immobilization mechanism was explored by Mercury Intrusion Porosimetry (MIP), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM) tests. The experimental results show that the group with a mass ratio of NS, LS and MK of 1:1:8 exhibits the highest compressive strength, which reaches 69.1 MPa at 28 d. The ternary geopolymer possesses a desirable capacity for immobilizing inherent heavy metals, where the immobilization rates of Cu and Pb reach 96.69 %, and that of Cr reaches 99.97 %. The leaching concentrations of Cr and Pb increase when the samples are exposed to acidic and alkaline environments. Cu and Pb are mainly physically encapsulated in geopolymer. Additionally, immobilization of Cr mainly involves physical encapsulation and chemical bonding.

Effects of composite admixture on the mechanical properties and microstructure of mortar

Based on the Fuller distribution theory, a composite admixture (CA2) with a ratio of lithium slag, water slag, and coal ash of 2: 0.5: 0.5 was prepared by adjusting the ratio of cement to composite admixture. CA2 was used to replace cement in different dosages, and the properties of mixed admixtures mortar (MAM) were verified by mechanical properties analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), mercury intrusion test, and hydration heat test. The results show that CA2 can effectively inhibit the early hydration heat, reduce the porosity of the matrix, optimize the microstructure morphology of cement hydration products, and ensure the later strength of mortar.

Insight into the kinetic behavior of microwave-assisted synthesis of NaX zeolite from lithium slag

Using microwave-assisted technology to shorten the synthesis time of NaX zeolite and proposing the reaction mechanism for synthesizing NaX zeolite from waste lithium slag.

Lithium slag-based geopolymer synthesized with hybrid solid activators

Lithium slag (LS) is a kind of solid waste in the lithium product industry. Nowadays, the amount of LS has increased sharply due to the popularity of lithium batteries; however, the recycling of LS is rare. In this research, LS was used to prepare the one-part geopolymer by three hybrid solid activators: NaOH + Na2SiO3, NaOH + Ca(OH)2, and NaOH + CaCO3. The effects of such hybrid activators on the workability, mechanical property, hydration process, microstructure, and pore structure of the formed one-part geopolymer samples were investigated. Experimental results showed that the LS-based geopolymers with 5 % of the hybrid activator could obtain moderate mechanical properties (The maximum 28d compressive strength can reach 35.6 MPa). Ca(OH)2 and CaCO3 had lower alkalinity than Na2SiO3, but they exhibited superior effects when combined with NaOH. Ca-based activators increased the reaction degree of the hardened paste, leading to generating more C-ASH gel. Besides, the pore structure of the formed geopolymers was also refined. Compared with Na2SiO3 and Ca(OH)2, CaCO3 is more suitable for preparing the NaOH activated LS-based geopolymer.

Mechanism and assessment of the pozzolanic activity of melting-quenching lithium slag modified with MgO

The current energy consumption and waste emission are mainly produced from the process of cement manufacturing. Lithium slag (LS), a solid waste from lithium smelting, has been utilized as concrete additives with a low rate of approximately 10 %, and the remaining nearly 90 % of LS are stored as industrial solid waste, which not only occupies large amounts of land, but also causes serious resource waste and environmental pollution. For the purpose of developing a kind of cleaner binders using LS to reduce cement consumption and environmental pollution, a novel activation method of “chemical modification-melting granulation-mechanical pulverization” was conducted in this present study. Alkali cations, such as Mg2+, Ca2+, etc., are beneficial to improve the pozzolanic activity of LS according to previous results. Thus, a chemical modification was first performed by preparing the melted-quenched mixtures of LS and MgO in different ratios, and coded as MGLS. The characterization results of MGLS demonstrate that MgO modification can enhance the pozzolanic activity of LS by accelerating the dissolution of the amorphous networks. Pastes of PPC and P-MGLS (70 % PPC + 30 % MGLS) were prepared for UCS tests (a maximum allowable rate of 30 % for LS as concrete additives, according to engineering experience), showing clear retardations of strength development for P-MGLS pastes due to the low extent of pozzolanic reaction in the early period of 3 ∼ 7 d. The 7 ∼ 90 d strengths significantly increase with the content of MgO for P-MGLS pastes, and the P-MGLS15 paste cured for 90 d gains the UCS value of 52.49 MPa, even higher than that of PPC paste at 90 d, due mainly to the enhanced pozzolanic reaction with large amounts of CSH/CAH gels formed by MgO modification, and a compact microstructure, as well as higher values of Ca/Si and Al/Si ratios are measured in the CSH/CAH gels of P-MGLS15 paste, indicating that more reactive constituents can be released to enhance the formation of pozzolanic products for the pastes richer in MgO. Results of the present study may provide a potential way for the applications such as construction building, backfill mining, etc., that can be developed using MGLS, which also promotes the sustainability for cement and environmental industries.

Investigation of sulfate on the migration/solidification mechanism and control of cadmium during sintering in lightweight aggregates

• The effect of sulfate on the migration of cadmium in LWAs was studied. • Sulfate contributes to the volatilization of cadmium in the form of Cd(g) and CdO(g). • The formation of CdFe 2 O 4 promotes the solidification rate of cadmium in LWAs up to 99.9%. • A reasonable heating rate and CdFe 2 O 4 production are conducive to the retention of cadmium. • An environmental risk assessment of cadmium leaching in LWAs was carried out. The effective solidification of cadmium is crucial for the clean production of lightweight aggregates (LWAs) from cadmium-contaminated soil (CCS), and the promotion of cadmium volatilization by sulfate is not negligible during sintering. This work methodically investigated the effect of CaSO 4 and Na 2 SO 4 with 0.5–2.5% sulfur content on the migration and solidification of cadmium in LWAs prepared from CCS and lithium slag (LS). The results showed that the two sulfates were irrelevant to the volatilization form of cadmium, including Cd(g) and CdO(g), in LWAs. The effect of Na 2 SO 4 was mainly reflected in the two aspects of generating CdO and lowering the formation temperature of CdO, while the role of CaSO 4 was just the latter. The cadmium retained in the LWAs was effectively solidified in the form of CdFe 2 O 4 , and its solidification rate was up to 99.99%. We found that the formation of CdO was reduced by rapid heating above 360 °C, which could achieve the long-term retention of cadmium. In addition, generating more CdFe 2 O 4 during sintering was beneficial for the solidification of cadmium. This study will help improve the understanding of the migration and solidification mechanism of cadmium in the presence of sulfur during the sintering process of LWAs and realize the clean production of LWAs and the harmless utilization of CCS and LS.

Corrosion behavior of concrete fabricated with lithium slag as corrosion inhibitor under simulated acid rain corrosion action

Concrete has great potential for local applications as a building material. Utilization of lithium slag in concrete can effectively and quickly solve its stacking problem. In this study, we used lithium slag to fabricate concrete and used a self-designed indoor dry-wet cycle spraying equipment to explore its acid rain corrosion resistance properties to promote its resource utilization because acid rain corrosion is very serious in Jiangxi Province. First, we investigated the fresh properties and the hardened properties of the concrete with lithium slag, and the mechanisms of acid rain corrosion resistance of concrete with lithium slag were studied. The study showed that lithium slag can accelerate the hydration reaction and improve the acid rain resistance of concrete, with better appearance integrity, and the lower decrease rate of compressive strength and mass loss of concrete. Unfortunately, lithium slag enhanced the neutralization depth of concrete. The compressive strength and mass loss of concrete with lithium slag are sensitive to the concentration of SO42−, and the neutralization depth is sensitive to the concentration of H+. Adding lithium slag can decrease the tendency for formation of CH crystals in the matrix, increase the hydration degree of cement, improve the microstructural compactness of concrete and decrease the Ca/Si of C–S–H gel. Therefore, lithium slag is beneficial for resisting the acid rain corrosion of concrete, and can be used as an acid rain corrosion inhibitor.

Microstructural investigation of lithium slag geopolymer pastes containing silica fume and fly ash as additive chemical modifiers

Lithium slag is an industrial by-product obtained after lithium extraction from spodumene ore. The higher concentration of sulfate ions (SO4−2) in the form of gypsum/anhydrite makes it a chemically unviable binder. This research investigates the dilution of the sulphatic component in pore solution by additive incorporation of silica fume and fly ash as chemical modifiers in the lithium slag geopolymer. The setting behavior, detailed microstructural properties, mineral phase quantitative analysis, and compressive strength of lithium slag geopolymer containing fly ash and silica fume were studied. The increasing silica to alumina ratios (Si/Al) by incorporating silica fume in sodium tetraborate added geopolymer resulted in the set retardation after the setting accelerated at Si/Al ratio of 3.5. Similarly, the set retardation was observed for all fly ash replaced lithium slag geopolymers marked by the lower dissolution of SO4−2 ions in pore solution. The fragmented and porous N-(C)-A-S-H gel in lithium slag geopolymer densified by additive incorporation of silica fume and fly ash due to suppressed formation of SO4−2 in pore solution, thus increasing the compressive strength. The main binding zeolite phases quantified in mineral and crystal phase analysis of fly ash replaced geopolymer were mordenite, anorthite, analcime, and calcium chabazite, whereas for silica fume incorporated geopolymer were mordenite, anorthite, analcime, and sodium clinoptilolite. Thus, the lithium slag can be a promising geopolymer precursor along with other supplementary cementitious materials. However, further research is suggested for its chemical viability as a sole geopolymer binder.

Effects of Lithium Slag on the Frost Resistance of Cement-Soil.

In this study, the effect of lithium slag (LS) on the frost resistance of cement-soil was evaluated. The results of freeze–thaw damage on the surface of the cement-soil, freeze–thaw mass loss, unconfined compression strength, triaxial shear strength, cohesion, and internal friction angle were tested at various freeze–thaw cycles after 90 days of curing when LS was incorporated into the cement-soil at different proportions (0%, 6%, 12%, and 18%). Combining nuclear magnetic resonance (NMR) T2 distribution and scanning electron microscopy (SEM) microscopic images, the mechanism of the effect of LS on the cement-soil was also analyzed. The experiment confirmed that the surface freeze–thaw damage degree and mass loss value of the cement-soil decreased after incorporating different LS contents, and that the unconfined compression strength, triaxial shear strength, cohesion, and internal friction angle also improved significantly compared with the specimens without LS. In this experiment, the optimization level of the cement-soil performance with different LS content was ranked as 12% > 18% > 6% > 0%. According to the NMR and SEM analysis results, the LS content of 12% can optimize the internal pore structure of the cement-soil and strengthen the bond between aggregate particles, hence inhibiting the extension of freeze-swelling cracks induced by freeze–thaw cycles. In conclusion, LS can effectively enhance the frost resistance of cement-soil, and the optimum content in this experiment is 12%.

Sustainable Use of Waste Oyster Shell Powders in a Ternary Supplementary Cementitious Material System for Green Concrete.

The increasing concern for decarbonization and sustainability in construction materials is calling for green binders to partially replace cement since its production is responsible for approximately 8% of global anthropogenic greenhouse gas emissions. Supplementary cementitious materials (SCMs), including fly ash, slag, silica fume, etc., can be used as a partial replacement for ordinary Portland cement (OPC) owing to reduced carbon dioxide emissions associated with OPC production. This study aims to investigate the sustainable use of waste oyster shell powder (OSP)-lithium slag (LS)-ground granulated blast furnace slag (GGBFS) ternary SCM system in green concrete. The effect of ternary SCMs to OPC ratio (0%, 10%, 20%, and 30%) on compressive strength and permeability of the green concrete were studied. The reaction products of the concrete containing OSP-LS-GGBFS SCM system were characterized by SEM and thermogravimetric analyses. The results obtained from this study revealed that the compressive strength of concrete mixed with ternary SCMs are improved compared with the reference specimens. The OSP-LS-GGBFS ternary SCMs-based mortars exhibited a lower porosity and permeability compared to the control specimens. However, when the substitution rate was 30%, the two parameters showed a decline. In addition, the samples incorporating ternary SCMs had a more refined pore structure and lower permeability than that of specimens adding OSP alone. This work expands the possibility of valorization of OSP for sustainable construction materials.

Microstructural investigation of thermo-mechanically processed lithium slag for geopolymer precursor using various characterization techniques

Lithium slag is an emerging industrial waste due to the increasing demand for lithium rechargeable batteries attributed to the recent boom in the automobile industry and space exploration. It is extracted as a powder residue in sedimentary tanks after the refining process of lithium extraction. In this study, the effect of thermo-mechanical processing on the chemical reactivity of lithium slag is assessed by TESCAN Integrated Mineral Analyzer (TIMA), X-ray Fluorescence (XRF), Rietveld quantitative refinement techniques. The chemical, mineral, and crystallographic phase composition of processed lithium slag specimens were assessed and compared by XRF, TIMA, and Rietveld quantitative refinement techniques, respectively. The results of thermo-mechanical processing indicated that the mineral and crystallographic transformation of Spodumene to feldspars (Anorthite, Muscovite, Albite) occurred by crystallite agglomeration. The chemical reactivity of lithium slag is gauged in terms of amorphous alumino-silicates present in feldspars and unidentified phases. Characterization of unidentified phase is evident that it majorly contains micro-nano sized alumino-silicate rich particles with similar spectral signatures to that of feldspar, some fraction of it is aggregated into other phases due to its reactivity. The concentration of the amorphous phase is proportionate with the thermo-mechanical processing energy. However, the thermo-mechanical processing energy is also optimized based on the generation of amorphous phase and reduction in particle size. Therefore, the G1C700 processed regime resulted in one of the maximum amounts of amorphous phase (52.60%). The mineral phase transformation of Spodumene to Anorthite (+10.46%) and unidentified phase (+8.24%) along with D50 value of 13.26 µm, consequently releasing 0.45 kg of carbon emissions upon thermo-mechanical processing. Hence, G1C700 lithium slag is recommended for its use as a geopolymer precursor.

Explore the synergic and coupling relationships of multiple industrial solid wastes in the preparation of alkali-activated materials under different curing regimes

Alkali-activated materials (AAMs) have become one of the most viable options in solving the issue of industrial solid wastes (ISWs). During the course, a series of blended AAMs using lithium slag as a major ingredient are prepared under different curing regimes to evaluate the setting behavior, compressive strength, microscopic characteristics as well as the synergic and coupling relationships between multi-ISWs in physics and chemistry during the geopolymerization. The results revealed that the multi-ISW design system and curing regime play a vital role in the setting time, compressive strength and geopolymerization process. Blended AAMs preparing with multi-ISW system of 50% lithium slag, 35% fly ash, 5% silica fume and 10% slag presents better compressive strength and desirable setting time. The synergic and coupling relationships among lithium slag, fly ash, silica fume and slag are complicated and variable, which can be inferred from the remarkable changes in reaction degree of precursors, microstructure of gels matrix and macro-performance. Moreover, reasonable synergic and coupling relationships between multi-ISWs may provide some guidance for the manufacture of green and low-carbon lithium slag-based AAMs with better application value.

Sustainable Utilization of Waste Oyster Shell Powders with Different Fineness Levels in a Ternary Supplementary Cementitious Material System

As cement manufacturing accounts for 8% of global CO2 emissions, there is an urgent need to tackle the environmental impacts of cement production and address the decarbonization of construction materials. Adopting supplementary cementitious materials (SCMs), including fly ash, slag, silica fume, etc., can be used as a partial replacement for ordinary Portland cement (OPC) to reduce CO2 emissions related to the OPC industry, while providing benefits for waste valorization. This study aims to explore the sustainable utilization of a waste oyster shell powder (OSP)–lithium slag (LS)–ground granulated blast furnace slag (GGBFS) ternary SCM system in green concrete. The effect of OSP fineness on compressive strength, hydration products, pore structure, and transport properties in ternary SCM-based mortars was studied using a wide array of experimental techniques, including thermogravimetric analysis (TGA), scanning electron microscopy (SEM) analysis, Mercury intrusion porosimetry (MIP), the water absorption test and the rapid chloride penetration test (RCPT). The results revealed that the concrete with the ternary SCMs showed equivalent compressive strength compared to reference specimens. The water absorption and chloride ion charge of the RCPT in the concrete containing the ternary SCMs decreased by up to 30% and 81.4%, respectively. It was observed that the specimens incorporating the OSP with a mesh size of 3000 exhibited the highest compressive strength and the most refined microstructure.

Volatilization control of CdCl2 and its solidification mechanism during lightweight aggregate production from Cd-contaminated soil

Lightweight aggregates (LWAs) have potential in the harmless resource utilization of Cd-contaminated soil due to their extraordinary ability to effectively solidify heavy metals, although the negative effects of chlorine in the soil are nonnegligible. This work methodically investigated the influence of KCl and MgCl2 with concentrations ranging from 1% to 5% on the volatilization, and solidification of cadmium in LWAs prepared with contaminated soil and lithium slag. The results indicated that cadmium was discharged out of the LWA in the form of CdCl2 driven by Cl−, and the remaining cadmium was completely solidified in the LWA in the form of CdFe2O4. It was found that the addition of chloride significantly increased the volatilization ratio of cadmium, and the distribution of the pore structure of the LWAs was more uniform. The effect of KCl on the volatilization ratio of cadmium and the physical properties of LWA is significantly better than that with MgCl2. It could mainly due to the differences in the release of chlorine free radicals and the content of metal oxides introduced by chlorides. This work could help to understand the migration and transformation mechanism of cadmium in LWAs and guide CdCl2 emission control technology. Ultimately, it is feasible to realize the resource utilization of Cd-contaminated soil and lithium slag with a cleaner approach.

The use of contaminated soil and lithium slag for the production of sustainable lightweight aggregate

The contaminated soil (CS) and lithium slag (LS) contain amounts of hazardous ingredients which may move into the ground water and local cropland. In order to prevent CS and LS from damaging the environment, an investigation on the utilization of CS and LS for the production of lightweight aggregate (LWA) was presented in this article. The basic properties of LWA were evaluated. Furthermore, the crystalline phases of the produced LWA were analyzed, and the microstructure of LWA was analyzed by X-ray micro-tomography. The experimental results showed that the LWA produced from the CS and LS had good performances with density of 0.5–1.5 g/cm3 and compressive strength of 1.0–8.7 MPa, which met the required standard of LWA. Meanwhile, it can be revealed that the LS can reduce the sintering temperature of LWA, thus exhibiting low energy consumption. The analysis of crystal phases indicated that the mineral compositions of LWA contained spinel phases, which provided a possibility for the solidification of heavy metals. In addition, the evaluation of environmental effect revealed the leaching concentrations of hazardous metals were much lower than the critical limits of nonhazardous materials. Finally, the economic benefits were analyzed in the entire production process of LWA, which indicated that using CS and LS to produce LWA can lower the raw material cost by 85–98%. This work will create a more eco-friendly and economical method for the management of solid wastes (CS and LS). Meanwhile, this study can provide theoretical basis for the sustainable production of LWA.

Characterization of Magnesium Potassium Phosphate Cement-Based Grouting Material Blended with High Volume Industrial Wastes

In the present research, industrial wastes, e.g., fly ash (FA), lithium slag (LS), ground granulated blast furnace slag (GGBS), and red mud (RM) were utilized to prepare the magnesium phosphate cement (MPC)-based grouting material by a two-component grouting method. Successive additions of GGBS within 40% (C1–C5) led to reduced fluidity, increased pH value, and shortened setting time. The compressive strength increased first and then decreased. The strength value reached the maximum at a 20% dosage (C3). Increasing the content of RM from 0% (C4) to 25% (C9) resulted in prolonged setting time and an increased pH value. The fluidity and compressive strength increased first and then decreased. The fluidity and strength value became the highest at a 15% additive ratio (C7). GGBS can significantly improve the strength and water resistance at 7 days and 28 days by the potential hydraulic property. RM has a smaller particle size than MP, making the microstructure denser by the pore-filling effect. Thus, the drying shrinkage was increased after adding GGBS, while it was decreased when incorporating RM. The MPC-based grouting material has a controllable short setting of 3–21 min, self-leveling fluidity above 200 mm, a near-neutral pH value, high early strength (1 day compressive strength of 5 MPa), minor drying shrinkage (one-tenth of OPC), and excellent water resistance (over 85%), which is much superior to traditional grouting materials.

Axial Compressive Behavior of Lithium Slag Recycled Coarse Aggregate Concrete-Filled Circular Steel Stub Columns

In order to study the axial compression performance of lithium slag recycled concrete short columns in circular steel tubes, eight short columns were designed and tested. The main influence parameters of the specimens are lithium slag replacement rate and recycled concrete replacement rate. The test process and failure mode of the specimens are observed, and the load-displacement curve is drawn. The influence of the replacement rate on the axial compression performance of the specimens is analyzed. The results show that recycled concrete replacing natural coarse aggregate will reduce the mechanical properties of specimens, but lithium slag mixed into recycled concrete can compensate for the lack of mechanical properties of recycled concrete, and the specimens mixed with lithium slag and recycled concrete have good stiffness and ductility.

Facile activation of lithium slag for the hydrothermal synthesis of zeolite A with commercial quality and high removal efficiency for the isotope of radioactive 90Sr

Zeolite A with commercial quality and high removal efficiency for Sr2+ was hydrothermally synthesized from lithium slag after mild and facile activation.

Characteristic and Mechanism of the Pozzolanic Activity of Melted-Quenched Lithium Slag Modified with Na2sio3

Characteristic and Mechanism of the Pozzolanic Activity of Melted-Quenched Lithium Slag Modified with Na2sio3

Mechanism and Assessment of the Pozzolanic Activity of Melting-Quenching Lithium Slag Modified with Mgo

Mechanism and Assessment of the Pozzolanic Activity of Melting-Quenching Lithium Slag Modified with Mgo