Water Leaching Research Articles

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.

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

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

Decoupling of sulfation reactions to enhance zinc extraction from electric arc furnace dust: Unveiling the significance of O2 activation and mechanistic insights

Electric arc furnace dust (EAFD) is a hazardous solid waste generated during steelmaking, boasting significant concentrations of zinc and iron. Currently, a large amount of EAFD is disposed of in landfills, causing severe environmental pollution and resource wastage. To address this issue, the sulfation roasting followed by water leaching process was proposed, offering efficient zinc extraction, iron separation, low cost, and environmental friendliness advantages. This study presented a novel experimental design that decoupled the sulfation process for EAFD into gas–solid and solid–solid processes to uncover the sulfation mechanisms. During these processes, Zn-bearing phases were successfully converted into zinc sulfate (ZnSO4), while Fe-bearing phases transformed into iron oxide (Fe2O3). The resulting compounds were then separated using a water leaching process, achieving a high zinc extraction rate of 97.21% and a low iron residue of 0.61%, respectively, for the gas–solid sulfation process, and 98.76% and 0.81% for the solid–solid sulfation process. Comprehensive characterizations, in situ diffusion Fourier transform infrared spectroscopy (DRIFTS) experiments, and density functional theory (DFT) calculations provide a deeper understanding of the sulfation restructuring mechanisms in gas–solid and solid–solid roasting processes, highlighting the significant role of O2 activation. In the solid–solid sulfation process, Fe2(SO4)3, derived from the oxidation of FeSO4 by O2, was identified as the predominant compound responsible for sulfation. In the gas–solid sulfation process, sulfite species (SO32-) played a critical role as intermediates, eventually transforming into sulfate species (SO42-) with the assistance of O2. Moreover, adsorbed SO2 underwent oxidation and activation by adsorbed O2, forming the sulfate functional group. Migration of this functional group to the adjacent Zn atom through a transition state, established a Zn-SO4 bond, disrupting the Zn-O bond on ZnFe2O4 and completing the sulfation of ZnFe2O4. This study provides a fresh perspective on the application of sulfation roasting for the extraction of valuable metals, contributing to resource sustainability and effective management of zinc-bearing resources.

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.

Effect of Plow Pan on the Redistribution Dynamics of Water and Nutrient Transport in Soils

Plow pans are an essential part of the agricultural soil structure. By adjusting the soil bulk density and plow pan height, the water and nutrient transport are dynamically redistributed. Plow pans play a crucial role in promoting crop growth, increasing yields, and supporting sustainable land management. In this study, a column experiment was conducted to investigate the effects of plow pan height (10 cm and 15 cm) and bulk density (1.2, 1.4, and 1.6 g cm⁻3) on soil nutrient and water leaching under high-volume (HV) and low-volume (LV) fertilizer applications. The results reveal that the leachate volume decreased by 61.9% at a plow pan height of 10 cm and by 96.2% at a plow pan height of 15 cm when the bulk density was increased from 1.2 to 1.4 g cm⁻3 under HV conditions. There was no leachate when the plow pan bulk density was 1.6 g cm−3. The reserved concentration of alkali-hydrolyzable N in the plow pan soils was the highest when the plow pan had a bulk density of 1.4 g cm−3 and a height of 15 cm. However, when the plow pan height was 15 cm, the available P content in the plow pan soils decreased by 27.0% and 21.0% at bulk densities of 1.4 g cm⁻3 and 1.6 g cm⁻3, respectively, when compared with 1.2 g cm⁻3. Furthermore, the available P concentrations in the plow pan and subsoil layers decreased with an increase in the plow pan height. The available K concentrations in the topsoil decreased by 26.8% and 24.0% when the plow pan bulk density was increased from 1.2 to 1.4 g cm−3 at heights of 10 and 15 cm, respectively. Thus, the optimal plow pan height and bulk density are closely related to the types of soil nutrients. However, it is clear that excessively high bulk densities (e.g., 1.6 g cm−3) negatively impact soil properties. For different nutrient requirements, a bulk density of 1.2 or 1.4 g cm−3 can be chosen, with each providing suitable options based on the specific nutrient needs. This research offers practical insights into changes in nutrient adsorption and fixation in agricultural production associated with alterations in plow pan bulk density.

Recovery of samarium and cobalt/iron oxide from SmCo magnets through acid baking and water leaching

AbstractRare earth elements (REEs) and cobalt (Co) are listed as critical raw materials because of their importance in global industrial production growth, high supply risk, and economic significance. The recovery of Co and REEs from secondary resources is therefore proposed as a key countermeasure to address this concern. In this study, a straightforward process that integrates acid baking and water leaching is proposed for the recovery of samarium (Sm) and Co from scrap SmCo magnets. Firstly, the chemical composition of SmCo magnets is revealed by ICP-OES and XRF. The Taguchi experimental design technique is employed to optimize nitric acid baking and water leaching. Based on the thermal decomposition behavior of Co, Fe, and Sm, the acid baking temperature is studied for the conversion of metal nitrates, excluding REEs nitrates, into metal oxides. The optimal conditions for acid baking and water leaching are identified, and a reactor for the pilot-scale acid baking process is proposed. The optimum parameters are tested with the proposed reactor.

Characteristics of middle-deep reservoirs and the genesis of pore development in the southern slope of the Nanpu sag in the Bohai Bay Basin, China

To clarify the distribution of favorable reservoirs in the middle and deep layers of the southern slope of the Nanpu sag and identify relatively high-quality reservoir sections, the characteristics of the reservoirs in the middle and deep layers of the southern slope of the Nanpu sag were studied by means of core analysis, thin section casting, scanning electron microscopy, and analytical tests. Research shows that the middle and deep reservoirs on the southern slope of the Nanpu sag are mainly lithic feldspathic sandstone and that the debris is mainly magmatic rock. The diagenesis processes are mainly compaction, cementation, and dissolution. The deformation of plastic particles, brittle microcracks on the surface of rigid clastic particles, calcareous cementation, quartz overgrowth, and feldspar dissolution are common. The pores are co-developed by primary pores and secondary pores, in which the primary pores are more common in the third member of the Dongying Formation and the first member of the Shahejie Formation, whereas the secondary pores are more common in the first member of the Shahejie Formation. The genesis of pore development is discussed. It is considered that the anticompaction components, chlorite film, and hydrocarbon filling play major roles in the formation of primary pores, whereas atmospheric water leaching, diagenetic evolution, thermal evolution of organic matter, and clay mineral transformation play major roles in the formation of secondary pores.

Selective lithium recovery from waste lithium-ion batteries by H2SO4 roasting focused on process intensification and conversion mechanism

The purpose of this study is to prove the feasibility, efficiency and selectivity of lithium recovery from waste lithium-ion batteries (LIB) via sulfuric acid roasting-water leaching by thermodynamic analysis and experimental verification. The feasibility was proved by Gibbs free energy calculations and experiments. Then, the effects of H2SO4 concentration, roasting temperature and roasting time were assessed on the leaching rate of valuable metals. The results indicate that the leaching efficiency of lithium increases firstly and then decreases with the increase of H2SO4 concentration, roasting temperature and roasting time, more than 91 % lithium are leached under optimized experimental conditions: 50 wt% H2SO4, roasting temperature of 650°C, and roasting time of 2 h. Meanwhile, the selectivity of lithium is up to 88 % which means overwhelming majority lithium have been separated completely. In addition, the factors which cause sintering phenomenon such as high temperature and longtime roasting will change the microstructure of roasted product extremely, which is inconducive to the subsequent water leaching. The investigations of the phase conversion mechanism by thermodynamic simulation and instrumental characterization indicated that the leaching behaviors of valuable metals might be influenced by the different reaction pathways of the compounds while changing roasting conditions. The recovery process can be divided into two stages: the partial structure of LiNixCoyMnzO2 was destroyed to form metal sulfates at ambient temperature and the solid phase reaction between unreacted LiNixCoyMnzO2 which contained Li+ in the unstable layered structure with transition metal sulfates at high temperature. The fully reduced low-valence states are mainly (NiO)0.75(MnO)0.25 and CoO, and basically all Li within the crystalline LiNixCoyMnzO2 was de-intercalated and transformed to soluble Li2SO4. These results further confirm the advantages of H2SO4 roasting on selective Li recovery, and provide a better understanding of conversion mechanism by combining theory and experiments.

CO2 sequestration by indirect mineral carbonation of serpentine with (NH4)2SO4 as a recyclable extractant

Mineral carbonation with serpentine can offer a sustainable and safe process option for simultaneous CO2 emission reduction and utilization of nature mineral. In this study, a sustainable process for CO2 mineral sequestration was proposed by using serpentine and ammonium sulfate as feedstocks. The mixture of feedstocks was subjected to roasting with temperature ranging from 390°C to 480°C, converting magnesium into the corresponding sulfate. Then, water leaching was employed to dissolve the magnesium sulfate from the roasted samples. Finally, through a mineralization reaction, the corresponding magnesium bicarbonate was generated after sequestrating CO2. Under the optimal roasting-leaching conditions, i.e. roasting temperature of 420ºC, roasting time of 2 hours, and mass ratio of ammonium sulfate/serpentine of 3; leaching temperature of 80ºC, leaching time of 1 hour, and a liquid-to-solid ratio of 1, the magnesium extraction efficiency reached 76 %. Thermodynamics and experimental results demonstrated that during the sulfation roasting process, the products generated during roasting, magnesium sulfate and silicon dioxide, adhered to the surface of the serpentine, thus inhibiting the mass transfer process and impeding the progress of the reaction. However, the liquid-solid reaction facilitated by molten ammonium sulfate and the gas-solid reaction provided by the decomposition of ammonium salts into SO2 played a promoting role in the sulfation roasting reaction. The carbonation of sulfated serpentine results indicated that the optimal CO2 storage capacity can reach 204 kg/t serpentine.

Seasonal nitrogen removal in an outdoor microalgal polyculture at Nordic conditions.

Microalgal solutions to clean waste streams and produce biomass were evaluated in Nordic conditions during winter, spring, and autumn in Southeast Sweden. The study investigated nitrogen (N) removal, biomass quality, and safety by treating industrial leachate water with a polyculture of local microalgae and bacteria in open raceway ponds, supplied with industrial CO2 effluent. Total N (TN) removal was higher in spring (1.5 g-2d-1), due to beneficial light conditions compared to winter and autumn (0.1 and 0.09 g-2d-1). Light, TN, and N species influenced the microalgal community (dominated by Chlorophyta), while the bacterial community remained stable throughout seasons with a large proportion of cyanobacteria. Winter conditions promoted biomass protein (19.6-26.7%) whereas lipids and carbohydrates were highest during spring (11.4-18.4 and 15.4-19.8%). Biomass toxin and metal content were below safety levels for fodder, but due to the potential presence of toxic strains, biofuels or fertilizer could be suitable applications for the algal biomass. PRACTITIONER POINTS: Microalgal removal of nitrogen from leachate water was evaluated in Nordic conditions during winter, spring, and autumn. Total nitrogen removal was highest in spring (1.5 g-2d-1), due to beneficial light conditions for autotrophic growth. Use of local polyculture made the cultivation more stable on a seasonal (light) and short-term (N-species changes) scale. Toxic elements in produced algal biomass were below legal thresholds for upcycling.

Effects of hot desert weathering on highly siderophile elements in ordinary chondrites

AbstractOver 20,000 meteorites have been recovered from hot deserts. The effects of hot desert weathering upon highly siderophile elements (HSE) have been little studied. We have investigated the effects of neutral to mildly acidic leaching of three L6‐type ordinary chondrites of different weathering grades on HSE concentrations and Re‐Os isotopic systematics. We have characterized the bulk sample HSE patterns of these meteorites and conducted leaching experiments with progressively longer leaching times to determine the possible effects of long‐term residence in a desert. The most weathered sample (NWA 14239) displayed greater HSE concentration homogeneity than the other samples and released lower quantities of HSEs during leaching. Water leaching was milder than acetic acid and did not significantly modify the Re‐Os isotopic systematics of the residue relative to the bulk sample of NWA 869. Short‐term leachates of the less weathered samples (Viñales and NWA 869) were characterized by low 187Os/188Os ratios, indicating the preferential dissolution of early solar system–formed phases such as non‐magnetic chondrules and matrix with low Re/Os that are no longer intact in the most weathered sample. Of the HSE, Pd is most resistant to both water and acetic acid leaching, with a maximum removal of ~5% Pd, while Re, Os, and Ir are most mobile with up to 40% removal.

Energy-Efficient Geopolymer Composites Containing Phase-Change Materials-Comparison of Different Contents and Types.

The purpose of this study was to analyze the effects of phase-change components on the properties of geopolymer foams. Geopolymer foams are lightweight foamed geopolymers that are characterized by a high degree of porosity. Phase change materials, on the other hand, are compounds that, when added to a material, allow it to absorb, store, and then release large amounts of energy. Three types of PCMs, i.e., MikroCaps, GR42, and PX25, were introduced at 15% by weight. Geopolymer materials were produced based on silica fly ash, and hydrogen peroxide H2O2 was used to foam the geopolymer structure. The PCM geopolymer composites were cured at 60 °C. The produced materials were tested for physical, chemical, and thermal properties. The tests included oxide and mineral composition analysis of the base material, PCM particle size analysis, apparent density and porosity tests on the foams, water leachability tests, thermal tests (λ, Cv, Cp, α), and structural and textural analysis. The most relevant tests to confirm the performance of the phase-change materials were thermal tests. With the introduction of PCMs, volumetric heat capacity increased by as much as 41% and specific heat by 45%, and thermal diffusivity decreased by 23%. The results confirm the great potential of geopolymer composites as modern insulation materials for buildings and structures.

Chloridizing roasting studies of spent NdFeB magnets for recovery of rare earth values

The increased demand for rare earth elements in advanced technological applications and supply shortages call for metal recovery from secondary sources. Permanent magnet (Nd2Fe14B or NdFeB) may serve as a potential secondary source due to its high rare earth (Nd+Pr+Dy: ∼30 %) content and its vast application. The present study utilizes a chloridizing roasting (CaCl2.2 H2O) pre-treatment process followed by water leaching, acid leaching (0.5 M HCl, S/L =1/10 g/ml, 90 °C, 3 h), oxalic acid precipitation and calcination (850 °C, 2 h) to obtain mixed rare earth oxides. The process was optimized based on temperature (400–700 °C), dosage (CaCl2.2H2O: NdFeB=0.5:1–2.5:1), and time (30–120 min) on the rare earth dissolution. The theoretical activation energy for the chloridizing roasting process is estimated as 22.3 (OFW) and 16.7 kJ/mol (KAS), while the experimental activation energy for Nd and Dy dissolution was determined to ∼29.3 and ∼17.7 kJ/mol, respectively depicting product layer diffusion-controlled kinetics. Higher dosages of CaCl2.2H2O (1.5:1 and 2:1) favored NdOCl formation, thereby, higher dissolution; however, further higher dosage (2.5:1) leads to reduced Nd dissolution due to higher CaO formation and acid consumption by Ca during leaching. Incomplete oxidation at lower temperatures (400 °C) and iron dissolution impair the Nd dissolution and selectivity. Excessive oxidation at >700 °C favors the formation of NdFeO3, decreasing Nd dissolution. The maximum dissolution of Nd was ∼89 %, while for Dy, it was ∼88 % at optimum conditions of 600 °C, 90 min, 2:1. Water leaching post-roasting leads to ∼87 % Ca removal and the precipitation efficiency of rare earth oxalates was 99 %. The overall extraction for rare earth elements was ∼89 %, and 1 kg of NdFeB powder can yield ∼285 g of rare earth oxides (∼239 g Nd2O3, ∼14 g Dy2O3) with 96 % purity. Further, this study demonstrates that using CaCl2.2 H2O as a solid chlorinating agent in chlorination roasting enhances recovery rates of mixed rare earth oxides while providing a safer and more environment-friendly alternative for industrial applications.

Pollution source characterization and evaluation of groundwater quality utilizing an integrated approach of Water Quality Index, GIS and multivariate statistical analysis

ABSTRACT The Mid-Gangetic Plain, a vital farmland in India, faces increasing groundwater quality deterioration due to anthropogenic activities. This study aimed to assess groundwater quality and contamination sources in the region utilizing statistical methods. A total of 78 groundwater samples were collected and analyzed using standard methods. The hydrochemistry analysis of samples revealed that several parameters such as Ca2+, Mg2+, HCO3−, NO3−, F− and PO43− surpassed the limits prescribed by the Bureau of Indian Standards (BIS). The principal component analysis yielded three significant factors, explaining 68.96% variation, highlighting geogenic and anthropogenic influences on groundwater chemistry. Hierarchical cluster analysis categorized groundwater into three clusters based on the parameters with similar trends of variation. Furthermore, Discriminant analysis identified four significant variables (Mg2+, F−, Cl− and NO3−) responsible for creating the distinction among the identified clusters. Hydrogeochemical categorization and multivariate statistical analyses indicated that rock–water interaction, weathering, leaching and anthropogenic activities collectively influenced groundwater quality throughout the studied region. The Water Quality Index reveals that 59% of samples have good water quality, while 41% exhibit poor quality predominantly concentrated in the south-western, south-eastern and central regions. This study demonstrates the efficacy of statistical techniques to interpret complex datasets and grasp water quality dynamics, enhancing groundwater management.

Highly efficient recovery of lithium from spent ternary NCM cathode materials via a selective chlorination method

The recovery of lithium from spent lithium-ion batteries (LIBs) is an important approach to solve the global shortage of lithium resource. Considering the difference in stability of various metal element chlorides in Ni-Co-Mn ternary (NCM) cathode materials, lithium element was selectively and high-efficiently extracted from spent ternary NCM cathode material by ammonium chloride roasting in oxygen atmosphere followed by water leaching. The effects of roasting temperature, roasting time, and NH4Cl dosage on lithium leaching efficiency and selectivity were systematically investigated. In addition, the conversion mechanism during chloride roasting was discussed in detail in conjunction with thermodynamic analysis as well as structural and compositional characterizations. After roasting with NH4Cl in oxygen atmosphere at 600°C, the spent NCM cathode material was thoroughly decomposed and converted into mixture of LiCl, NiO, and MnCo2O4. Due to the high aqueous solubility of LiCl, more than 95 % of the lithium in the mixture was leached in ∼30 minutes at room temperature, and Li2CO3 with a purity of 99.40 % can be obtained in the subsequent recovery process. This simple and efficient method can be generally useful for the recovery of a wide range of spent cathode materials and provide inspiration for the lithium recovery process of spent LIBs.