Water Leaching Research Articles

A sustainable approach for concurrent recovery of metals from H2 reduced bauxite residue (“red mud”): Process optimization

Bauxite residue (BR), a polymetallic waste, offers significant potential for valuable metal recovery. This study introduces a low temperature H2 reduction-alkaline (NaOH) roasting, followed by water leaching - wet magnetic separation, aimed at efficient recovery of Fe, Na, and Al, alongside non-magnetic tailings (Ca, Ti, and Si). To minimize H2 consumption, 5 vol % H2 + 95 vol % N2 with 200 L/kg was sufficient. Utilizing response surface methodology (RSM), the optimal H2 reduction process conditions were determined as a temperature of 600 °C and a time of 120 min with 20 wt% NaOH. Under these conditions, the maximum recoveries achieved were 74.4 % Fe (grade = 63.6 %), 84.6 % Al, and 91.6 % Na, with RSM model predicted Fe, Al, and Na recovery values at optimum conditions closely matching experimental results (<5 % deviation). The proposed sustainable process minimizes waste and offers a possible solution for BR processing.

Characterization of Physical and Chemical Properties of Multi-Source Metallurgical Dust and Analysis of Resource Utilization Pathways

Steel metallurgical dust, characterized by a substantial output, minute particle size, and intricate composition, poses a considerable risk of environmental contamination while simultaneously embodying an exceptionally high potential for recycling. To achieve its resource utilization, chemical analysis, particle size analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), Mössbauer spectroscopy, and water leaching methods were employed to investigate the chemical compositions, particle size distributions, phase compositions, and microscopic morphologies of blast furnace bag dust, sintering dust, converter fine dust, and electric arc furnace dust from steel plants. The results indicate that the four types of dust have extremely fine particle sizes, with the main distribution range of particle size being less than 100 μm. The main constituent element is Fe (19–56%), and it also contains Zn (1.4–33.5%), Pb, K, C, and other valuable elements. Alkali metals in blast furnace bag dust and sintering machine head dust existed mainly in the form of chloride. The zinc phases in sintering machine head dust and converter fine dust were ZnFe2O4, and the zinc phases in blast furnace bag dust were ZnCl2 and ZnFe2O4. Zinc in electric furnace dust was composed of ZnO and ZnFe2O4, accounting for 70.31% and 23.12%, respectively. There are significant differences in the types and contents of valuable elements among various dusts, making it difficult to achieve full-scale recovery through a single process. In view of this, a process of “in-plant recycling of harmless dusts—collaborative treatment of harmful dusts” has been proposed. Based on the characteristics of metallurgical dusts, multiple processes are used for collaborative treatment (using hydrometallurgical and pyrometallurgical methods), which can not only directly recover iron resources from dusts within the plant, but also avoid the waste of valuable elements such as Zn, Pb, K, Na, etc. It is hoped that the above work can provide a reference for steel enterprises to achieve full-scale and high value-added treatment of metallurgical dusts.

Application of selected indicators to assess contamination of municipal landfill leachate and its impact on groundwater

Leachate formation is one of the most important factors taken into account during the operation and long-term management of municipal waste landfills. Systematic assessment of groundwater and leachate contamination may be useful in selecting the appropriate method of leachate management or treatment processes. The use of indicators to quantify the contamination potential of leachate and groundwater in the vicinity of MSW could help landfill managers assess their quality. Therefore, the aim of the study was to assess the representativeness of selected indicator methods for analyzing the temporal variability of leachate and groundwater properties in the vicinity of two municipal waste landfills in a Central European country (Poland). The leachate pollution index (LPI), sub-LPI and adjusted leachate pollution index (r-LPI) were used to assess the quality of leachate water, while the landfill water pollution index (LWPI) was used to assess the variability of groundwater quality. The results confirmed that LWPI is an effective method for assessing the quality of groundwater in the vicinity of municipal waste landfills. The obtained results confirm the negative impact of landfills, despite the insulation used. LWPI showed poor quality of groundwater and visible impact of the landfill (landfill W, average LWPI - 2.34) and moderately polluted waters and minor impact of the landfill (landfill S, average LWPI - 1.37). In most cases, it was observed that two parameters, EC and TOC, are the main factors contributing to the deterioration of groundwater quality. The sub-LPI analysis showed that leachates from both landfills have a very low content of heavy metals, so they should not have a negative impact on the biological treatment process. The obtained r-LPI values were in all cases higher than the calculated LPI values. For landfill S, the average r-LPI was 26.3 (Z-1) and 25.7 (Z-2). However, the average LPI was 13.5 (Z-1) and 13.2 (Z-2). For landfill W, the average r-LPI was 14.6 and the average LPI was 11.4. Analysis conducted on multi-year leachate and groundwater data using specific indicators can help managers better understand the impact of MSW on surrounding areas and help avoid potential operational problems in the future.

The Assessment of the Ecological State of Leachate from the Largest landfill of Georgia and Its Impact on Climate Change

Over the past decade the municipal solid waste management status in Georgia remained at the stage of mixed waste collection and disposal in landfills having negative impacts on entire ecosystem. It results the formation of large amounts of leachate, methane gas, potential resource depletion and is potential to health hazards. Landfill leads to groundwater contamination, soil &amp; land pollution, harm to animals exposing to harmful materials &amp; foods. Landfills are vulnerable to accidental fires due to the methane produced by decomposing organic waste, financial costs that can be expensive for municipalities or city councils and taxpayers. The aim of this study is to assess the adversee impact of leachate management technology on water resources, as well as on climate change. For utilisation of leachate in this research, the technology of distributing the collected leachate over the surface of the landfill is used. The main objectives include, the study of physical-chemical and microbiological parameters of leachate and the calculation of GHG (methane) emissions from sedimentation systems/tanks/reservoirs of leachate. Physical-chemical and microbiological analysis of leachate water indicates that the concentrations of organic, biogenic and microbiological parameters in research samples exceed limits of discharge by ten times. In this study, for the first time an index of water pollution and greenhouse gas emissions was calculated for leachate of the biggest landfill in Georgia. Leachates belong to class VII according to water pollution index. Emission of methane from leachate for 2024-year estimated as 5% additionally to total methane emissions from the studied landfill.

Formation of placic horizons in soils of a temperate climate – The interplay of lithology and pedogenesis (Stołowe Mts, SW Poland)

A placic horizon is a thin soil layer that is cemented or indurated by Fe, Mn, and/or Al compounds as well as by organic matter. The placic horizon is a hard, continuous, and nearly impermeable and impenetrable horizon that retards the vertical leaching of water and inhibits the growth of roots. Placic horizons can develop under different climates and in various ways. However, we do not fully understand the interactions between lithology and pedogenesis that might promote placic horizon formation. Therefore, to shed light on the mechanisms of placic genesis, we used an applied multiproxy approach (electrical resistivity tomography – ERT, XRD, 57Fe Mössbauer spectroscopy, bulk geochemistry, soil micromorphology and 14C dating) for three soils developed from sandstone–mudstone parent materials in mountainous areas of SW Poland, to shed light on the mechanisms of placic horizon genesis. The ERT inversion models and soil survey data indicate lithic discontinuities in the profiles. Soil micromorphology data confirmed that a placic horizons formed slightly below the discontinuity. Radiocarbon ages of the placic horizon span from 2.2 to 4.8 ka and suggest that more humid conditions were favorable for the formation of a placic horizon, which aligns with our mineralogical results. Ferrihydrite is the major Fe oxyhydroxide in the placic horizon. Micromorphological data showed that after the formation of the placic horizon, a phase of clay migration might have occurred, while later, podzolisation took over as the main soil-forming process. This sequence shows that thin iron pans can develop independently of other processes and can exist (at least some of them) before the development of a spodic horizon. A placic horizon causes severe hydrological changes in the topsoil and subsurface horizons. Thus, water stagnation in the soil transforms it into a Stagnosol or Planosol and it’s responsible for the evolution of local plant communities and the ecosystem.

Enhanced phosphorus bioavailability and reduced water leachability in dairy manure through hydrothermal carbonization: effect of processing temperature and CaO additive

ABSTRACT Dairy manure, a significant source of phosphorus (P), can potentially cause environmental risk due to P runoff when dairy manure is directly applied to cropland. Thus, there is an increasing interest in mitigating P loss from manure prior to land applications. This study aimed to investigate the potential of hydrochar produced by hydrothermal carbonization (HTC) for P recycling from dairy manure with and without the addition of CaO, focusing on the plant bioavailability, stabilization, and transformation of P in the resultant hydrochar. Hydrochar was prepared under different temperatures (180–240°C). The effect of CaO addition (0–10% of raw manure on dry wt. basis) was also evaluated at 220°C. Results showed that water-soluble P (WSP), a key indicator of P runoff loss, was significantly reduced in hydrochar, particularly with CaO addition. In addition, the plant available P in hydrochar increased with HTC temperature increase till 220°C, which accounted for ∼90% of total P content, then decreased with temperatures higher than 220°C. The addition of CaO slightly reduced plant bioavailability when compared to hydrochar produced at 220°C without additive. The P fractionation and speciation analyses indicated the transformation of P into Ca-associated apatite P. Hydrochar produced at 220°C with 10% CaO addition resulted in a high P recovery (∼85%) and a reduced runoff risk by 97%. The results demonstrate the efficacy of P recycling through hydrochar produced from dairy manure through HTC, which offers a sustainable approach to managing dairy waste while mitigating the potential environmental risks of P runoff.

Selective extraction of scandium from bauxite residue (red mud) utilizing iron sulfate roasting followed by water leaching

Scandium (Sc) is the most commercially valuable rare earth element due to its unique superior properties and extensive application. Bauxite residue (red mud) is regarded as one of the industrial wastes with the potential to recover Sc. In this study, a two-step process via sulfation roasting with iron sulfate and water leaching was developed to selectively recover Sc from red mud. The results showed that the leaching efficiency of Sc depended on various factors including roasting temperature, the dosage of iron sulfate, and roasting atmosphere. The leaching efficiency of Sc reached 78.8 % with 5.1 % of Fe and 13.0 % of Al dissolved in the Sc-rich solution at the optimum conditions of the SO3-controlled roasting at 700 °C for 15 min with red mud and iron sulfate mass ratio of 1:1, followed by water leaching at room temperature for 180 min. It is demonstrated that the Sc-rich solution could be recycled for leaching clinkers to accumulate Sc concentrations to meet the requirements of solvent extraction. This study also provided new insights about the reaction mechanisms and phase transformations of the roasting and water leaching process. The findings provided a valorization route of red mud by recovery of Sc resource due to the relatively simple process, high selectivity, and low-cost reagents.

Micro-Topographic Controls on Rare Earth Element Accumulation and Fractionation in Weathering Profiles: Case Study of Ion-Adsorption Rare Earth Element Deposit in Hedi, Zhejiang Province, China

Ion-adsorption rare earth element (REE) deposits are a major source of REEs and are found mainly in China. The formation of such deposits is affected by a combination of endogenic and exogenic factors. This study investigated the effect of micro-topography on the REE distribution in four weathering profiles at different topographic sites on a knoll in Hedi, Zhejiang Province, China. The weathering profile and REE accumulation are both most developed at mid-slope positions of the knoll. The intensity of chemical weathering decreases in the order of mid-slope &gt; base &gt; summit. As weathering progressed, REE enrichment initially increased but later decreased, with a progressive increase in light/heavy REE fractionation. REE fractionation is more pronounced on the north-facing slope than on the south-facing slope. Weathering degrees and clay mineral characteristics are key factors influencing the varying REE distributions on the knoll. Water leaching and the evolution of clay minerals towards higher maturity reduce REE adsorption capacity. Clay minerals also play a significant role in REE fractionation; the abundance of these minerals and the presence of illite enable the retention of more HREEs with minimal desorption. Taking into account water content, it is inferred that hydrological conditions, modulated by the micro-topography, strongly affect the depth and extent of REE accumulation, as well as fractionation.

Green method for preparation NaVO2 from vanadium-chromium slag based on Na2CO3 roasting and water leaching

An effective and environment-friendly method for preparing NaVO2, which can be used as an energy storage material, from Na2CO3 roasted vanadium-chromium slag was proposed using water as the leaching medium. Vanadium-chromium slag with 30 % Na2CO3 was heated in air and argon atmospheres from 30 °C to 1000 °C, respectively. The results show that vanadium compounds converted to NaVO3 while chromium compounds to Na2CrO4 under air. NaVO3 and Na2CrO4 were water-soluble making the separation of vanadium and chromium complicated. NaVO3 and Na2CrO4 were water-soluble making the separation of vanadium and chromium complicated. Heating vanadium-chromium slag in an argon atmosphere caused Fe2VO4 to react with Na2CO3, forming NaVO2 and NaFeO2 below 1000 °C. However, chromium compounds unreacted in argon. NaFeO2 was insoluble, while NaVO2 was water-soluble with a leaching efficiency exceeding 70 %. Notably, the characteristic peak of V(III) in NaVO2 was first found to be −532.00 ppm by the liquid 51V NMR spectrum. This method represents a novel, green strategy for the resource utilization of vanadium-chromium slag, involving Na2CO3 roasting in an argon atmosphere to produce NaVO2. It offers a promising approach to reduce the cost of NaVO2 battery production and support its commercialization.

Efficient removal of chromium from electroplating sludge by a novel combined process of alkaline oxidizing roasting, water leaching and on-line adsorption

Chromium-bearing electroplating sludge (ES) is a typical hazardous waste that poses significant environmental risks due to the toxic and carcinogenic nature of chromium. In this study, Cr extraction is performed by roasting with Na2CO3 and water leaching from ES, and finally recovered by an on-line adsorption process by using an eco-friendly material. Under Na2CO3 roasting and water leaching, 82.1 % of Cr was leached out, with conditions of 800 ℃, Na2CO3 dosage amount at 30 %, and a residence time of 2 h for the roasting step, and solid-liquid ratio of 1:2 for the water leaching step. The results of the column adsorption tests indicated that FH/ SCB exhibited superior adsorption performances toward Cr (VI) with a maximum adsorption capacity of 20.5 mg/g, and its adsorption isotherm was matched with the Laugmuir model. About 97.4 % of Cr was recycled from the ES under the dynamic on-line adsorption process, furthermore, the total content of Cr in the final effluent was lower than wastewater discharge standards of 0.5 mg/L. In conclusion, this combined method presents an alternative approach for the eliminating, detoxifying, and reusing of chromium-bearing ES.

Microplastic Contamination in Landfill Leachate and Surface Water: Assessment of Wastewater Treatment Efficiency at the Nonthaburi Waste Management Center, Thailand

Microplastics (MPs), plastic particles smaller than 5 mm, have emerged as a significant environmental concern, particularly as contaminants originating from landfills. Landfills can serve as a major source of MPs, potentially releasing them into surface water through leachate. This study aims to investigate the contamination of MPs in leachate and surface water, as well as to evaluate the efficiency of landfill wastewater treatment in removing these particles. The research was conducted at the Waste Management Center of the Nonthaburi Provincial Administrative Organization, Thailand, with samples collected in June 2023. Sampling included two leachate sources, influent and effluent from the treatment system and surface water. The abundance and characteristics of MPs in each sample were analyzed. Results indicated a significant presence of MPs in leachate, with an average concentration of 173.98 pieces/L, while concentrations in influent, effluent and surface water were 38.40 pieces/L, 10.80 pieces/L and 11.33 pieces/L, respectively. MPs in all samples were predominantly in the size range of 16-100 µm, corresponding to 71.28-93.75% of the total particles. Polypropylene was the dominant polymer in leachate (69.66%) and effluent (48.94%), whereas acrylate copolymer (96.53%) and polytetrafluoroethylene (44.12%) were the major types found in influent and surface water, respectively. The wastewater treatment system of the landfill demonstrated an overall removal efficiency of 71.88% for MPs in leachate. These findings highlight the extent of MP contamination in landfill environments and the importance of improving treatment processes to mitigate their release into surrounding ecosystems.

Influence of Self-Heating on Landfill Leachate Migration

The hydrodynamic processes of landfill leachate migration in the base of a solid waste landfill can have a critical impact on the natural environment. In the case of improper operation of municipal solid waste placement facilities, highly contaminated leachate may penetrate into groundwater and subsequently into surface water. This work addresses fundamental issues of multicomponent fluid propagation in a multilayer porous medium, taking into account temperature inhomogeneities caused by waste decomposition with heat release. The regimes of diffusion and convection of leachate water penetrating into soil layers in the base of municipal solid waste facilities are numerically studied. Archival data from a set of field and laboratory measurements in the area of the operating landfill are used to model the features of pollutant propagation and determine migration parameters. The process of pollutant propagation and migration is described by quantitative values of dry residue content in leachate. Factors that have a significant impact on the migration of leachate are considered. The main ones are convective transfer, diffusion, and properties of the geological composition of the landfill base, which are taken into account in the mathematical formulation of the problem. The calculations show that leachate self-heating can substantially intensify leachate filtration and has to be taken into account in the assessment of leachate migration rate.

Selective Leaching of Lithium and Beyond: Sustainable Eggshell-Mediated Recovery from Spent Li-Ion Batteries

This study introduces an innovative strategy for the selective leaching of lithium from spent Li-ion batteries. Based on thermodynamic assessments and exploiting waste eggshells as a source of calcium carbonate, an impressive 38% of lithium was dissolved selectively through mechanical milling and water leaching, outperforming conventional thermochemical methods. Afterwards, a hydrogen peroxide-assisted sulfuric acid leaching was also implemented to solubilize targeted elements (Mn, Co, Ni, and Li), with an exceptional 99% efficiency in Mn removal from the leachate using potassium permanganate and a pH range of 1.5 to 3.5. Selective separations of Co and Ni were then facilitated utilizing CYANEX 272 and n-heptane. This comprehensive study presents a promising and sustainable avenue for the effective recovery of Li and associated co-elements from spent lithium batteries.

Towards realism in hazard assessment of plastic and rubber leachates – Methodological considerations

While plastic chemicals are key drivers of observed effects to aquatic species, there remains a lack of standardized and fit-for-purpose approaches for experimentally deconvoluting the effects of plastic chemicals from particle effects. This study investigated differences in chemical composition determined using two different organic solvents for extractions (dichloromethane-ethyl acetate, methanol) and by thermal desorption applied to 51 thermoplastic and elastomer products. The composition of natural water leachates of four select elastomers was also investigated. The number of chemical features in each material varied according to the extraction method, with solvent extracts exhibiting the most chemicals, and only 19 compounds commonly identified by all three methods. The number of chemical features in leachates was generally similar to the corresponding chemical extracts, but strong differences in relative composition were detected. While turbulence had minimal impact on leachate composition, particle loading strongly influenced leachate composition, temperature and salinity influenced the leachate concentration for some chemicals, and leaching time depended upon chemical mobility. Leachate composition cannot be readily predicted from particle characterization and multiple parameters are drivers of compositional variance in aquatic leachates. Recommendations for performing leaching studies that are relevant for hazard characterization in a realistic aquatic environment risk assessment scenario are suggested, with a particular focus on particle loading.

A method and mechanism for extracting Cu, Co, and Zn from limonite tailings

The development of green methods to process and use iron tailings is crucial due to the accumulation of tailings, which poses significant environmental and human health risks. In this study, a scheme of extracting Cu, Co and Zn from limonite tailings by sulfuric roasting with ammonium sulfate and then water leaching was proposed. Most of the Fe is converted to jarosite and enriched in the leaching residue. Ferric iron is present in the leaching residue in the form of jarosite and can be reused as an adsorbent. The impact of various factors, including roasting temperature, time, ammonium sulfate dosage, leaching temperature, and liquid-to-solid ratio, on the metal leaching rate was investigated. The findings indicated that when the roasting temperature was set at 400°C, the roasting time was 120 minutes, the quantity of ammonium sulfate was 1.5 times the original amount, the leaching temperature was 70°C, and the liquid-to-solid ratio was 10:1, the leaching rate of Fe was as low as 34.20 %, and the leaching rates of Cu, Co, and Zn were 81.25 %, 91.35 %, and 89.35 %, respectively. A mechanistic analysis indicates that during the calcination process, the phase transitions of Fe are (NH₄)₃Fe(SO₄)₃, NH₄Fe(SO₄)₂, and Fe₂(SO₄)₃, and the phase transformations of Cu, Co, and Zn are in accordance with these changes. A higher leaching temperature makes it easier for iron to form jarosite, which reduces the leaching rate of iron. This study has a simple, efficient, and environmentally friendly method for extracting valuable metals from limonite tailings.

Recovery of valuable elements from copper slag through low-temperature sulfuric acid curing and water leaching

Recovery of valuable elements from copper slag through low-temperature sulfuric acid curing and water leaching

Smectite-rich horizons in Inceptisols trigger shallow landslides in tropical granitic terranes

Puerto Rico was affected by >70,000 landslides in the wake of 2017 Hurricane Maria, and landslide prevalence was especially high in the Utuado region in the Cordillera Central. Landslide density was highest where soil parent material is granodiorite; landslide slip surfaces tended to be shallow (<60 cm), and often were mobilized rapidly and with long runout distances. This study combines field observations with soil mineralogy (bulk and clay fractions), soil geochemistry (bulk fraction), and soil strength as determined by field cone penetrometer testing (CPT) to test the hypothesis that clay-rich subsoil horizons function as slip planes when water-logged. Soil pits were excavated to depths of ~200 cm in Ultisols on an undulating plateau and to ~100 cm in Inceptisols on steep slopes (36-43o) that flank the plateau and cone penetrometer tests (CPT) were done within 2 m of the soil pit. Six pits were located adjacent to scarps from previous landslides, enabling analysis of soil profiles downward through extrapolated slip surfaces. Results from X-ray diffraction (XRD), X-ray fluorescence (XRF) and thermogravimetric analysis (TGA) indicate that soils are heterogeneous, often with subsoil horizons enriched in clay minerals and immobile elements (Al, Fe, Ti). Inceptisols on steep slopes often contain smectite-rich horizons at 30–60 cm depth that appear to function as slip surfaces; in other Inceptisols, such horizons are not present and landslide susceptibility is potentially lower. In Ultisols, soil mineralogy is dominated by kaolinite with minor halloysite, and increased kaolinite content at soil depths ≥80 cm at some sites suggests potential slip surfaces enhancing probability of landslides. The origin of clay-rich horizons appears to be (1) fractures in granodiorite that facilitate water flow and leaching, accelerating mineral dissolution during early weathering stages, and (2) smectite-rich buried soils under permeable colluvium likely deposited by a prior mass wasting event. Where clay-rich layers occur beneath more-permeable horizons, rapid infiltration then absorption of water in clay-rich subsoil horizons causes decreased shear strength and increased landslide susceptibility.

Physicochemical and toxicological characteristics of leachates and water quality around dumpsites in Lagos Nigeria

Improper waste management leading to contamination of groundwater resources is a global environmental issue. This study examined the physicochemical and toxicological characteristics of leachates and their effect on water quality around the dumpsite in Alimosho Lagos, Nigeria. Samples of water and leachates were collected from boreholes around the dumpsite. Physiochemical and toxicological characterization of water around the dumpsite was based on American Public Health Association standards. Seventeen physiochemical and heavy metals of leachate and borehole water samples were analysed. The result of the study shows that the temperature, odour, appearance and turbidity of the water in the study area were within the limits set by WHO. However, the pH was below the WHO limits indicative of the acidity of the groundwater. The presence of Pb, Cr, and Cd confirmed leachate pollution. The contemporary effects confirmed the insignificant effect of the dumpsite operations at the groundwater source. Without a properly designed leachate series system, uncontrolled accumulation of leachates at the bottom of the dumpsite poses capacity infection dangers to groundwater resources. It is recommended that proper disposal of waste, in addition to implementing a higher sustainable environmental sanitation practice, is needed to ensure the safety of groundwater within the locality.

A low-temperature process for lithium extraction from lithium-bearing mineral: Conversion behavior and mechanisms

Lithium extraction from lithium-bearing clay mineral (LiBC) has received significant attention due to the increasing demand of lithium for the advanced renewable energy industry. However, the low contents of valuable elements and stable physiochemical properties of LiBC result in high energy consumption and low efficiency in extracting lithium from LiBC. This study demonstrates a low-temperature strategy using (NH4)2SO4 as an additive to effectively extract lithium from LiBC. In details, the thermodynamic analysis verifies that Li, Al, and Fe can be converted to sulfates at 250–450 °C during thermal treatment, indicating the possibility for extraction of Li under low-temperature conditions. Subsequently, the leaching behavior of lithium under different roasting temperatures and water leaching conditions was investigated. The results show that 83.43 % of Li can be extracted under optimized conditions. The mechanism study was carried out through a number of characterization techniques including 3D microscope, TG-DSC, XRD, FTIR, and SEM. It reveals that formation of liquidus phase of molten salt is the key to achieve low-temperature roasting and transfer and reactions at the interface of molten salt and LiBC can be significantly enhanced that can easily breakdown the interlayer structures. Consequently, it offers distinct advantages, since the roasting temperature can be significantly decreased with minor impurity ions being leached into the solutions. This research therefore provides an efficient and environmentally friendly method for lithium extraction from minerals.

A Comparison Study on the Recovery of REEs from Red Mud by Sulfation Roasting–Water Leaching and Citric Acid Leaching

In this study, the recovery of rare earth elements (REEs) from red mud (bauxite residue) was explored through a combination of citric acid leaching and sulfation roasting–water leaching processes, introducing an innovative approach to the field. The research uniquely investigates the influence of citric acid on the leaching behavior of REEs and impurities in both untreated red mud and red mud subjected to sulfation roasting, providing a direct comparison of these methodologies. A novel aspect of this study is the evaluation of solvent extraction efficiency using DEHPA, highlighting the selective recovery of REEs over impurities from both citric acid and water-leaching solutions. Furthermore, a comprehensive phase analysis using X-ray diffraction (XRD) was conducted to track the transformations of minerals during the sulfation roasting process, an original contribution to the literature. The findings revealed that over 85% of REEs and major elements such as Fe, Al, Ca, and Ti dissolved in water after sulfation at 105 °C, while iron and titanium dissolution significantly decreased following roasting at 725 °C. Importantly, terbium, neodymium, and gadolinium extraction efficiencies were notably affected by roasting temperature. Citric acid leaching results demonstrated that the direct leaching of red mud leads to higher leaching efficiency than leaching it after the roasting process. Solvent extraction demonstrated lower terbium and neodymium recovery from citric acid solutions compared to water leaching solution. Finally, stripping experiments illustrated that 6M H2SO4 solution is capable of stripping more than 80% of rare earth elements, except terbium.