Sequential Extraction Method Research Articles

PHYTOCHEMICAL SCREENING, ANTIMICROBIAL, AND ANTIOXIDANT ANALYSIS OF BERBERIS LYCIUM ROYLE CRUDE ROOT EXTRACTS

Objective: This particular study was designed to evaluate the qualitative, quantitative, anti-oxidant, and antimicrobial potential of Berberis lycium root extracts. Methods: The plant root extracts were prepared using a sequential extraction method using different solvents with increasing polarity. Further extracts were evaluated qualitatively for the presence of different phytochemicals and quantitatively for the presence of total phenols and flavonoid, antioxidant potential using DPPH, ferric reducing anti-oxidant power, and H2O2 radical scavenging assay. Biological potential of these extracts was established for antibacterial effect against different Gram-negative and Gram-positive bacteria and antifungal potential against fungal strains. Results: Qualitative analysis of the root extracts showed the presence of phytochemicals such as saponins, tannins, phenols, and flavonoids. Among all the evaluated extracts in quantitative analysis, methanolic extracts showed the highest content of phenolic with 39.75 mg gallic acid equivalence/g and flavanoid with 456 mg QE/g, highest antioxidant potential with half-maximal inhibitory concentration (IC50) value of 10.96 μg/mL in DPPH assay. Similarly, the highest antibacterial effect against Bacillus cereus (20±0.86 mm) and antifungal against Aspergillus niger (IC50 399.64 μg/mL) was observed. Conclusion: The plant root extracts of B. lycium have shown substantial content of phytochemicals with appreciable antioxidant and antimicrobial activities comparable to the currently prescribed modern drugs tested. Accordingly, further studies on clinical efficacy trial, safety, and toxicity analyses have to be instigated promptly, so as to head to the final step to synthesize precursor molecules for new effective antimicrobials.

Molecular-level carbon traits of fine roots: unveiling adaptation and decomposition under flooded conditions

Abstract. Fine roots are vital for plant development and carbon biogeochemical cycling in terrestrial ecosystems. Flooding is known to regulate the physiology and morphology in plant roots; however, its impact on molecular-level characteristics of carbon compounds (carbon traits) in fine roots remains largely unexplored, which limits our understanding of root adaptation and decomposition under changing environments. Here, we used a sequential extraction method, starting from nonpolar to polar solvents, in order to obtain dichloromethane- and methanol-extractable (FDcMe) fractions, base-hydrolyzable (FKOHhy) fractions, and CuO-oxidizable (FCuOox) fractions from fine roots of Dysoxylum binectariferum, which is naturally grown in soil and water. Subsequently, we characterized them using targeted gas chromatography–mass spectrometry and nontargeted Fourier transform ion cyclotron resonance mass spectrometry. Also, decomposition experiments were conducted on soil- and water-grown roots under aerobic and anoxic conditions. Results showed a consistent increase in the unsaturation degree and aromaticity of the analytes from FDcMe to FCuOox fractions. Both analyses were sufficiently sensitive to show that, compared to soil-grown roots, the water-grown roots developed more polyphenolics with a high unsaturation degree and aromaticity and had more nonstructural compositions. Furthermore, although flooding provided an anoxic condition that slowed down root decomposition, the adaptive strategy of developing more nonstructural labile components in water-grown roots accelerated root decomposition, thereby counteracting the effects of anoxia. This advances our understanding of biogeochemical processes in response to global environmental change.

Adapted Sequential Extraction Protocol to Study Mercury Speciation in Gold Mining Tailings: Implications for Environmental Contamination in the Amazon.

Artisanal small-scale gold mining (ASGM), an increasingly prevalent activity in South America, generates mercury-contaminated tailings that are often disposed of in the environment, leading to the introduction of mercury into ecosystems and the food web, where it bioaccumulates. Therefore, studying the geochemical processes involved in the desorption and dissolution of mercury in these tailings is essential for critical risk evaluations in the short and long term. For this purpose, sequential extraction procedures (SEPs) can be useful because they help to identify the phases to which Hg is associated, although they also have limitations such as a lack of selectivity and specificity. In this work, we propose a modified four-step SEP: exchangeable mercury (F1), oxidizable mercury (F2), mercury bound to Fe oxides (F3), and strongly bound mercury (F4). To test this adapted sequential extraction method, we evaluated the Hg contamination in mercury-contaminated tailings of the Amazon basin. The results revealed a total mercury concentration of 103 ± 16 mg·kg-1 in the tailings, with a significant portion in F1 (28% of the total), where Hg was bioavailable. The large Hg concentration in F3 (36%) suggested that Fe oxides likely contribute to mercury retention. Together, the SEP results emphasize the urgent need for improved surveillance of gold mining activities and responsible tailings management practices to mitigate environmental contamination and safeguard the health of the Amazon ecosystem.

Bioleaching ion-unexchangeable rare earth in ion-adsorption type rare earth waste tailing

Ion-adsorption type rare earth ores (IREO) in China serve as the primary source of medium and heavy rare earth globally. With the rapidly growing demand for rare earth elements (REEs) and the dwindling supply of premium IREO, enhancing the recovery of REEs, especially the ion-unexchangeable REEs with ultra-low content and ambiguous speciation from IREO or its tailing, has become a critical trend and challenge. This study identified the occurrences of ion-unexchangeable REEs, primarily detected in Fe-enriched minerals, xenotime, and monazite of IREO using TESCAN integrated mineral analyzer (TIMA) and laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS) analysis. To extract these elusive REEs, a bioleaching technique utilizing Aspergillus niger (A. niger) metabolites was proposed, achieving a leaching yield of 31.4 wt%. Complementary sequential chemical extraction methods (SCEM), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations further elucidate the underlying mechanism, involving the carboxylic acid produced by the metabolic process of microbes that dissolves goethite by disrupting FeO bonds and liberating REEs, which complexed with carboxylate (RCOO), to promote further dissolution. This work offers insight into enhancing the recovery of ion-unexchangeable REEs from IREO or its tailing, paving the way for sustainable and efficient rare earth mining practices.

Coffee industrial residue: sequential high pressure extraction and conventional methods

Coffee industrial residue: sequential high pressure extraction and conventional methods

Valorization of cell wall polysaccharides extracted from Liubao brick tea residues: chemical, structural, and hypoglycemic properties.

Tea dregs, typically generated during the production of instant tea or tea beverages, have conventionally been regarded as waste material and routinely discarded. Nevertheless, contemporary research endeavors are concentrating on discovering efficient methods for utilizing the potential of this discarded resource. In this study, we employed a sequential extraction method using chemical chelating agents to extract and isolate four distinct cell wall polysaccharides, designated as CWTPS-1 through CWTPS-4, from the tea dregs of Liubao brick tea. A comprehensive investigation into their physicochemical, structural, and hypoglycemic properties was conducted. The analysis of chemical composition and physicochemical characteristics revealed that all four CWTPSs were characterized as acidic polysaccharides, albeit with varying chemical compositions and physicochemical attributes. Specifically, the xyloglucan fractions, CWTPS-3 and CWTPS-4, were found to be rich in glucose and xylose, displaying a more uniform molecular weight distribution, greater structural stability, and a more irregular surface compared to the others. Moreover, they exhibited a higher diversity of monosaccharide residues. Importantly, our research unveiled that all four CWTPSs exhibited the capacity to modulate key glucose-regulated and antioxidant enzyme activities within HepG2 cells via the IRS-1-PI3K/AKT signaling pathway, thereby ameliorating cellular insulin resistance. Furthermore, our correlation analysis highlighted significant associations between monosaccharide composition and neutral sugar content with the observed hypoglycemic activity of CWTPSs. This study highlights the potential of utilizing tea dregs as a valuable resource, making a significant contribution to the advancement of the tea industry. Furthermore, CWTPS-4 exhibits promising prospects for further development as a functional food ingredient or additive. © 2024 Society of Chemical Industry.

Mitigation of arsenic and zinc toxicity in municipal sewage sludge through co-pyrolysis with zero-valent iron: A promising approach for toxicity reduction of sewage sludge

Abstract The co-pyrolysis (at 300°C and 600°C) of municipal sewage sludge (SS) with zero-valent iron (Fe0: 1.5% and 3%) was investigated to reduce the toxicity of arsenic (As) and zinc (Zn) in SS. The BCR sequential extraction method, desorption kinetic analysis, and material characterization techniques (Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, X-ray diffraction) were used to evaluate the effects of the treatments on Zn and As behavior. The results showed that co-pyrolysis significantly reduced the acid-soluble fraction (18–43% for Zn; 83–95% for As) and mobility factor (45–85% for Zn; 86–96% for As) of Zn and As compared to untreated SS. Desorption experiments indicated a significant reduction in Zn and As release in treated samples, particularly in the co-pyrolysis sample at 600°C and Fe0 3% (67% for Zn; 88% for As) in comparison with untreated SS. Co-pyrolysis of Fe0 and SS led to the formation of new functional groups (Si–O, aromatic), a more porous surface morphology, and highly stable chemical crystals (ferric arsenate, zinc arsenide), which played a crucial role in Zn and As stabilization. The findings of this study suggest that co-pyrolysis is a promising approach for mitigating As and Zn toxicity in SS. However, additional field testing with plant-based systems is necessary for confirmation.

Quarry soil and quarry stream water baseline level parameters around Chestedi Quarry, F.A.U.C. Golden Ltd Quarry, Fakunle Quarry and River Oyanmi in Igarra, Akoko Edo

The primary objective of this research was to investigate the initial levels of chemical parameters surrounding quarry operations in Igarra, Akoko-Edo, Edo State. Specifically, three prominent quarries (Chestedi, F.A.U.C. Golden Ltd, and Fakunle) were examined, along with the water of River Onyami flowing through these quarries from the Ojirami dam. Each quarry site yielded four soil samples collected at a various depth (between 0 – 15 cm) and different geographical coordinates, while four water samples were obtained from River Onyami. These samples underwent analysis for their physicochemical properties and the chemical speciation of Fe, Zn, Cu, Pb, Cr, and Mn. As Tessier et al. (1978) described, a sequential extraction method was employed to partition the heavy metals into five different fractions. Total concentrations of heavy metals in both soil and water samples were determined. The distribution of heavy metals in the soil exhibited the following order of accumulation: Fe > Zn > Mn > Cu > Pb > Cr, whereas in water samples, the order was Fe > Zn > Cu > Mn > Pb > Cr. Iron and zinc emerged as the predominant heavy metals in the soil, with iron within permissible limits but zinc, copper, manganese, lead, and chromium exceeding their respective limits. In the stream water, iron and lead surpassed their permissible limits, while Zn, Cu, Cr, and Mn remained below theirs. Comparative analysis against WHO, NIS DPR, and CCME maximum contamination/permissible limits was conducted for heavy metal concentrations and physicochemical properties in both soil and water samples. Mobility Factors (MF), Environmental Risk Factors (ERF), Contamination Factors (CF), Pollution Load Index (PLI), and Geoaccumulation Index (GI) were computed. Results from this study indicate that the soil is conducive to supporting growth and is nutrient-rich for various applications, while the water is suitable for irrigation and other domestic purposes.

Study on the characterization and thermal conversion behavior of sequential extraction products from medium temperature coal pitch

To achieve the high value-added clean utilization of medium temperature coal pitch (MTP), five fractions were separated from MTP by the sequential extraction method using n-heptane, n-butanol, toluene, tetrahydrofuran and quinoline as solvents. Briefly, the extracts were analysed using proximate analysis, elemental analysis, fourier infrared spectrum (FTIR), ultraviolet visible spectrum (UV–vis), fluorescence spectrum, and thermogravimetric analysis (TGA) to investigate their structural parameters, aromatic condensation degree and pyrolysis properties. Meanwhile, Raman spectrum, X-ray diffraction (XRD), and polarizing microscope were used to quantitatively analyze the microstructures of thermal conversion products of the extracts. This allowed for investigation of the thermal conversion mechanism and determination of the thermal conversion behavior. In fact, the chain index (CH3/CH2), aromatic index (Iar), aromatic condensation degree and thermal stability of the extracts increase gradually with deeper extraction. Extracts with high aromatic condensation degree are more favorable for the formation of mesocarbon microbeads (MCMBs). However, overly aromatic condensation degree will lead to excessive coalescence of MCMBs. The ideal carbon microcrystalline content increases with higher temperatures during the thermal conversion of the same fraction. But the change of amorphous carbon content has no obvious regularity. The results of this work will provide theoretical and experimental support for the selection of precursors for carbon/graphite materials.

Abstract 5054: Optimization and evaluation of an FFPE dual extraction protocol for next-generation sequencing applications

Abstract Formalin-fixed paraffin-embedded (FFPE) biopsies are highly valuable and widely used tissue specimens for clinical diagnostics. However, obtaining sufficient and high-quality nucleic acid material from limited FFPE samples presents a challenge for downstream molecular analysis, such as next-generation sequencing (NGS). We present an optimized sequential extraction method that generates high-quality DNA and RNA from a single set of input tissues that is automatable and operation-friendly. This workflow performs well with reduced FFPE tissue input and efficiently supports various high-throughput clinical NGS applications. The DNA/RNA yield, quality, purity, and impacts on NGS assay performances were on par or better than an existing validated comparator extraction method. With comparable FFPE input, the new method demonstrated a superior extraction performance with significantly higher yield, quality, and purity. For DNA, NGS libraries were made with two different library preparation methods: a TA-ligation-based method and a single-strand-based method, followed by hybrid capturing and sequencing. The DNA from the new extraction method demonstrated a superior library conversion rate and improved target enrichment uniformity with both chemistries. This provides the potential of reduced input requirements, allowing very limited tissue, such as fine needle aspirate or core needle biopsy, for clinical NGS testing. The sequencing results were highly concordant between the existing and new extraction methods when the extracted DNA was subjected to a validated comprehensive genomic profiling (CGP) clinical test, demonstrating the quality and robustness of the extraction. For RNA, NGS libraries were made following the validated CGP clinical test with hybrid capturing, and the results were comparable between the two extraction methods. In conclusion, an FFPE extraction method was optimized to allow more clinical biopsy samples to be tested with different NGS workflows, providing a better diagnostic value for patient care. Citation Format: Rebecca Hong, Jieying Chu, Steven Hsiao, Daniel Whang, Steven P. Rivera, Heng Xie, Jiannan Guo. Optimization and evaluation of an FFPE dual extraction protocol for next-generation sequencing applications [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5054.

Characteristics and Release Risk of Phosphorus from Sediments in a Karst Canyon Reservoir, China

With the continuous improvement of surface water environmental quality in China, sediment has gradually become the focus of research on internal pollution in reservoirs. To investigate the forms, distribution, and migration patterns of phosphorus in karst canyon reservoir sediments, we employed an improved sequential graded extraction method to determine phosphorus content in the sediments of the Wanfeng Reservoir. We studied the spatial distribution characteristics and release risk of phosphorus form in the sediments. The results showed that the total phosphorus (TP) content ranged from 79.37 to 438.04 mg·kg−1, while inorganic phosphorus (IP) content ranged from 77.32 to 424.64 mg·kg−1. Iron–aluminum-bound inorganic phosphorus (Fe/Al-Pi) accounted for 36.41% and was found to be the dominant form of IP. Organic phosphorus (OP) content ranged from 1.84 to 13.59 mg·kg−1, with weakly adsorbed organic phosphorus (H2O-Po) being the dominant form of OP. Potentially active inorganic phosphorus (NaHCO3-Pi) showed a highly significant positive correlation (p < 0.01) with Fe/Al-Pi, residual phosphorus (Res-P), and TP. This indicates that potentially active phosphorus (NaHCO3-P) is a significant potential source of phosphorus (P) in the reservoir. Biologically active phosphorus (BAP) content ranged from 66.97 to 201.46 mg·kg−1, with BAP/TP ratios ranging from 55.6% to 59.6%. The risk of phosphorus release from Wanfeng Reservoir sediments is high. The release of various forms of phosphorus from sediments is one of the important factors leading to the deterioration of water quality in the reservoir area in the future. To effectively manage water ecology in karst canyon reservoirs, it is essential to reduce the risk of endogenous phosphorus release.

Comparative study of chemical speciation and leaching feature of typical heavy metals in coarse and fine slags from the entrained-flow coal gasification

ABSTRACT The dissimilarity in chemical speciation and release properties of heavy metals will result in varying levels of environmental hazards and potential applications of coal gasification coarse and fine slags. The distribution, chemical speciation, leaching features, and potential environmental risks of heavy metals (Cr, Cu, Cd, Zn, Pb, and Mn) in coarse and fine slags from different coal gasification processes were revealed and compared by the sequential chemical extraction method, Horizontal vibration method, and pH-dependent leaching experiments. The results show that Cr (516.78 mg/kg) in coarse slag, Zn (348.50 mg/kg) and Pb (214.78 mg/kg) in fine slag are highly enriched and the content exceeds the screening value, indicating the need for better management during stockpiling and landfilling. The distribution of Cr, Cu, Pb, and Mn in residual state, Zn in Fe-Mn oxide bound state, and Cd in unstable bound state is the highest in both coarse slag and fine slag. The leaching toxicity of heavy metals (HMs) does not exceed the standard, but the leachate is classified as Level V surface water or groundwater quality due to the leaching concentration of Pb exceeding 0.1 mg/L. Furthermore, leaching of Cr, Zn, Cd, and Pb in fine slag is much more dependent on pH compared to coarse slag, and the concentrations of Zn and Pb exceed emission standards at pH < 3.0. The high concentration of heavy metals caught on the surface of fine slag is more harmful to the environment. The properties of HMs in the slags and pH of the application environment must be comprehensively considered before coal gasification slag disposal, especially fine slag.

Antibacterial potentials of extracts from Gryllotalpa gryllotalpa, Pentodon algerinum grubs, and Gypsonoma euphraticana larva frass

Objectives: The overuse and abuse of antibiotics have accelerated antibiotic resistance, and to solve this problem, it has been found that many insect species have potential antimicrobial properties against a wide range of resistant pathogens. Our study tests the antibacterial activity of microbial defensive compounds included in body extract of insects inhabiting contaminated environments and frass of phytophagous insects. Materials and Methods: Through sequential extraction method by acidic methanol, chloroform, and hexane solvents, insect body extract of Gryllotalpa gryllotalpa, grubs of Pentodon algerinum besides feces of Gypsonoma euphraticana larvae were tested against Gram-positives Bacillus cereus, Bacillus coagulans, Staphylococcus aureus, and Salmonella typhi, Escherichia coli, and Klebsiella pneumoniae. The antibiotics ceftriaxone (CRO) and ampicillin (AM) were used as standard drugs. The antibacterial growth inhibition was estimated by well diffusion methods. Results: High significant antibacterial activity against the tested bacteria by acidic methanol then chloroform extracts, while hexane extract of all the three insect species only produced significant growth inhibition of S. aureus. In addition, growth inhibition 20.0 mm or more was induced by: MeOH extracts of G. gryllotalpa and P. algerinum for S. typhi and E. coli, besides chloroform G. gryllotalpa extract for S. typhi. The tested bacteria S. aureus, S. typhi, and K. pneumoniae were AM-resistant, while E. coli was both AM and CRO-resistant. Conclusion: Acidic meOH and chloroform body extract of G. gryllotalpa and P. algerinum and larvae G. euphraticana feces extract possess bioactive compounds with promising antibacterial properties, for overcoming antibiotic resistance.

SOLID-PHASE FRACTIONATION OF HEAVY METAL IONS IN SOILS FROM MUNICIPAL WASTE DUMPSITE IN PORT HARCOURT, NIGERIA

In many cities across the developing countries solid wastes are disposed indiscriminately without recourse to the human health risk. Heavy metals found in solid wastes may likely be released into the environment via flood runoff. To assess whether the contaminants can affect the groundwater, soil samples were collected for analysis in two seasons – dry and wet seasons. To determine level of the metals in the soil matrix, the samples were subjected to acid digestion followed by atomic absorption spectroscopy analysis. The different solid-phases associated with heavy metals were evaluated from the soil samples by using sequential extraction method. The geo-accumulation index and mobility factor were considered to assess the level of contamination and migration of the metals present in the soil. The soil metal contents strongly correlated with the soil pH and organic matter. The exchangeable fraction has Cr &gt; Pb &gt; Co in the order of its mobility in the soil, whilst in the residual fraction suggesting the most immobile species with Pb &gt; Co &gt; Cr &gt; Ni present in the soil. The geo-accumulation index showed that the degree of pollution of the dumpsite during the dry and wet seasons was mostly unpolluted. The study indicates that the metals of interest may not likely pose environmental risk due to their relatively low concentrations and the chemical species in which they exist in soil.

Risk and mechanisms of phosphorus release at the sediment-water interface of lakes in cold and arid regions during non-frozen seasons.

In recent years, the eutrophication of lakes has accelerated in cold arid regions; the release of nutrients from sediments is an important contributor. The sequential extraction method, high-resolution peeper (HR-Peeper), and diffusive gradients in thin films (DGT) techniques were used to study the occurrence characteristics, release risk, and release mechanism of phosphorus (P) at the sediment-water interface (SWI) of Ulanor Wetland in the Hulun Lake Basin, Inner Mongolia, China. The mean total P concentration in overlying water was lower in August than that in May. Dissolved organic P (DOP) or particulate P (PP) was the main form of P in the overlying water. PP dominates in May and DOP in August. Refractory P was the main form of P in sediments. The concentrations of soluble reactive P and DGT-active P in the pore water of the sediment column were higher than those in the overlying water, and the concentrations were higher in August than those in May. Release of P in the wetland sediments occurred during the non-frozen seasons, with a higher risk in August than in May. The good linear correlation between dissolved P, Fe, and Mn in the DGT profiles verified their co-release due to the anaerobic reduction of Fe/Mn oxides. Moreover, alkaline sediments are also conducive to the release of sediment P. This study can provide data and theoretical support for eutrophication control in Ulanor Wetland and other similar water bodies in cold and arid regions.

Microwave-assisted extraction of pectin from onion and garlic waste under organic, inorganic and dual acid mixtures

This study aims to investigate pectin extraction from garlic (GW) and onion waste (OW) by microwave-assisted (MAE) and sequential microwave assisted-hot acid extraction (MAHE) methods. All extractions were performed under three different media including organic acids [citric (CA) and acetic (AA)], inorganic acids [sulfuric (H2SO4) and hydrochloric (HCl)] and their mixtures. GW provided more pectin yields compared with OW. While the highest pectin yields from GW and OW by MAE in H2SO4 were respectively 24.62 ± 0.65 and 24.93 ± 0.59%, these yields under MAHE were 27.99 ± 0.36 and 28.43 ± 0.42%, respectively. Higher pectin yields and galacturonic acid (Gal-A) contents were mostly achieved in inorganic acids. However, degree of esterification (DE), methoxyl content (MeO) and equivalent weight (EW) values were higher for the pectins extracted under organic acids. Extraction of pectin from GW and OW was also accomplished in dual acidic media by MAE. Addition of inorganic acids to the organic acid solutions resulted in increasing pectin yields. The highest pectin yields from GW and OW under dual acid solutions were respectively 23.36 ± 0.66 and 21.88 ± 0.52%, and achieved in 1/3 HCl-H2SO4 and 1/3 CA-H2SO4 mixtures by MAE. While increasing inorganic acid contents in dual acid solutions resulted in enhanced Gal-A contents, increasing organic acid volume also generated higher DE and MeO values of the pectins. Obtained successful outcomes indicate that MAHE method could be used as an efficient extraction technique for the higher pectin yields, and utilization of organic-inorganic dual acid mixtures during MAE provides enhanced yields and controlled physicochemical properties of pectin.Graphical abstract

Development of a 3–step sequential extraction method to investigate the fraction and affecting factors of 21 antibiotics in soils

Antibiotic exist in various states after entering agricultural soil through the application of manure, including the aqueous state (I), which can be directly absorbed by plants, and the auxiliary organic extraction state (III), which is closely associated with the pseudo-permanence of antibiotics. However, effective analytical methods for extracting and affecting factors on fractions of different antibiotic states remain unclear. In this study, KCl, acetonitrile/Na2EDTA-McIlvaine buffer, and acetonitrile/water were successively used to extract states I, II, and III of 21 antibiotics in soil, and the recovery efficiency met the quantitative requirements. Random forest classification and variance partitioning analysis revealed that dissolved organic matter, pH, and organic matter were important factors affecting the recovery efficiency of antibiotic in states I, II, and III, respectively. Additionally, 65-day spiked soil experiments combined with Mantel test analysis suggested that pH, organic acids, heavy metals, and noncrystalline minerals differentially affected antibiotic type and state. Importantly, a structural equation model indicated that organic acids play a crucial role in the fraction of antibiotic states. Overall, this study reveals the factors influencing the fraction of different antibiotic states in soil, which is helpful for accurately assessing their ecological risk.

Assessment of the ecological risk and mobility of arsenic and heavy metals in soils and mine tailings from the Carmina mine site (Asturias, NW Spain)

An evaluation of the pollution, distribution, and mobility of arsenic and heavy metals in spoil heaps and soils surrounding the abandoned Carmina lead–zinc mine (Asturias, northern Spain) was carried out. Fractionation of arsenic was performed by an arsenic-specific sequential extraction method; while, heavy metal fractionations was carried out using the protocol of the Bureau Community of Reference (BCR) (now renamed Standards, Measurements and Testing Programme). Arsenic appeared predominantly associated with amorphous iron oxyhydroxides. Among the heavy metals, lead and zinc showed high availability since significant amounts were extracted in the nonresidual fractions; whereas, chromium, copper and nickel showed very low availability, indicating their lithogenic origins. The results showed that the extractability of heavy metals in soils is influenced mainly by the presence of iron and manganese oxides as well as by pH and Eh. Multiple pollution indices, including the enrichment factor (EF), geoaccumulation index (Igeo), ecological risk index (Er) and potential ecological risk index (PERI), were used to assess the degree of soil pollution in the mine area. All results showed that lead was the key factor causing the pollution and ecological risk in the studied area, and copper, zinc and arsenic also had significant contributions. Notably, the sites at higher risk coincided with those with high availability of arsenic and heavy metals. This study provides an integrative approach that serves as a powerful tool to evaluate the metal pollution status and potential threats to the local environment of abandoned mining areas, and the results are useful for making management decisions in these areas.

Lithium in Greek Coal Fly Ashes: Contents and Characterization by Sequential Extraction

Lithium belongs to the critical elements and is used in a variety of high-tech applications. In the context of the circular economy, demand has arisen for technologies that are able to recover high-tech metals from wastes and byproducts. To achieve efficient recovery, apart from assessing metal enrichment, extensive knowledge of metal binding and leaching characteristics is required. The aim of the present study is to investigate the Li contents and mode of occurrence in Greek coal fly ashes. Eight coal fly ashes from different power plants in Greece were collected, and their major constituents were analyzed by X-ray fluorescence spectroscopy (XRF); their mineralogy was studied by X-ray powder diffraction (XRD), and their Li content was determined by ICP–MS. To identify Li binding and leaching characteristics, two sequential extraction methods (Tessier and BCR) were employed. The results showed that the Li content in the samples studied was between 95 and 256 μg/g and could be mainly attributed to the amorphous material encountered in the samples. The sequential extraction experiments revealed that 70–90% of Li is included in the residual fraction, indicating that it is strongly bound to the fly ash matrix.

Extraction of valuable critical metals from coal gangue by roasting activation-sulfuric acid leaching

ABSTRACT Coal gangue is a bulk industrial solid waste produced in the process of coal mining and washing, with the dual attributes of resourcefulness and hazardousness. It can be used as a reserve resource for valuable critical metals such as aluminum (Al), lithium (Li), gallium (Ga), and rare earth elements (REEs). In this paper, the occurrence modes of Li, Ga, and REEs in coal gangue were studied by sequential chemical extraction method. The extraction of valuable critical metals from the coal gangue was systematically studied by roasting activation-sulfuric acid leaching process, and the activation mechanism was elucidated. The results showed that roasting can destroy the inert kaolinite structure in coal gangue and significantly improve the leaching rate of valuable critical metals. Under the optimum conditions, the leaching rates of Al, Li, Ga, and REEs reached 86.51%, 74.46%, 95.45%, and 77.14%, respectively, and the leaching behaviors of Al, Li, and Ga were highly similar. In addition, the characterization of the leaching residue revealed 83.96% silicon oxide content with a loose and porous surface, which could be used to prepare silicon-based products. This study provides the theoretical basis and technical support for the utilization of valuable metals in coal gangue.