Search Results (1,095)

In this study, the characteristics of sulfide minerals during the acidic double reverse flotation of phosphate ore and the adsorption mechanisms of sodium oleate (NaOL) and dodecyl trimethyl ammonium bromide (DTAB) were investigated. Micro-flotation test results indicated that NaOL effectively collected galena, sphalerite, and pyrite at a concentration of 1 × 10⁻³ mol/L and pH 4–5.5, whereas DTAB exhibited selectivity for galena at 1 × 10⁻⁴ mol/L. Mixed mineral flotation revealed that NaOL induced a non-selective bulk flotation of sulfides with dolomite, resulting in a high froth yield of 93.23%, while the DTAB system showed superior selectivity with a froth yield of 54.91%. Surface analyses (Zeta potential, FTIR, and XPS) confirmed that NaOL chemisorbs onto sulfide surfaces via metal-oleate complexes, whereas DTAB adsorption is dominated by electrostatic attraction. Bench-scale tests validated the “double-rejection” flowsheet, significantly upgrading the P₂O₅ grade from 23.38% to 31.47% by sequentially partitioning Pb, Zn and Fe into the froth tailings. Size-by-assay analysis indicated that the sulfide separation was primarily controlled by the extent of mineral liberation. These findings provide a robust theoretical framework and practical guidance for the simultaneous management of sulfide minerals during phosphate beneficiation. Full article

Activated carbons are usually prepared from natural precursors (e.g., fruit stones or nutshells) by carbonization and activation processes carried out at 400–1000 °C. They exhibit well-developed porosity, and chemical activation introduces hydrophilic functional groups on their surface, providing excellent sorption properties. However, the high temperatures required during thermal treatment increase production costs. In this work, cost-reducing methods for preparing carbon sorbents are proposed. Carbonization of H₃PO₄ activated waste pistachio nutshells was performed using classical pyrolysis (500 or 550 °C, 30 min, N₂ atmosphere) and microwave treatment (power 1000 W, 20 min). The properties of the synthesized carbons were characterized using thermogravimetry and spectroscopic techniques including infrared (ATR), Raman, photoelectron (XPS) spectroscopies, and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS). Porous structure parameters were determined using nitrogen adsorption experiments. The efficiency of Pb²⁺ removal from spiked ultrapure, tap and river water was evaluated by batch sorption experiments and inductively coupled plasma–mass spectrometry. The most porous carbons were those prepared at 500 and 550 °C, with specific surface areas of 910 and 256 m²/g, respectively. Surface phosphates increased the Pb²⁺ sorption efficiency to 99% from ultrapure water, at an initial concentration of 300 µg Pb²⁺/L. The material obtained with the microwave method was not fully carbonized and remained nonporous, but it also exhibited 99% Pb²⁺ uptake from ultrapure water due to the presence of oxygen-containing surface groups. The Pb²⁺ removal from spiked tap and river water reached up to 84% and 94%, respectively, at the spiking level of 300 µg Pb²⁺/L. Full article

The large quantities of agri-food waste produced worldwide by the tomato processing industry require recovery. This study evaluated the efficiency of the by-product resulting from tomato juice preparation as an innovative biomaterial for removing lead from water. The pomace was dried and tested in two forms: raw (RT) and after extraction of soluble compounds (ET). The extracts obtained from the preparation of ET, could be reintroduced into the food industry (as colorants, etc.) according to the “zero waste” principle, but further studies are needed. No other chemical pre-treatment was applied to improve the lead-adsorption capacity. The pH influence, biosorbent dosage, kinetics and equilibrium were evaluated. Analytical methods, such as atomic absorption spectrometry, elemental chemical analysis, FTIR, scanning electron microscopy, and predictive models, were applied. The outcomes demonstrated a lead-adsorption efficiency of 99.22% for ET and 89.83% for RT, an optimum pH of 4.0 ± 0.5, and an initial solution containing 20 mg Pb²⁺/L. The Langmuir model predicted high removal capacities: 142.18 mg/g for ET and 90.91 mg/g for RT. Both forms of tomato pomace were efficient for sustainable and cost-effective water remediation, but an improvement was noticed after the extraction of soluble components that could be valorized in other products within the circular economy. Full article

Understanding the accumulation, ecological risk, and source interactions of potentially toxic elements (PTEs) in reservoir sediments is essential for protecting drinking water safety, yet such processes remain insufficiently understood in karst tea-plantation watersheds influenced by mixed anthropogenic activities. In this study, sediment cores collected from four sites (CY-1 to CY-4) during 2022–2024 were analyzed, and an integrated framework combining the Potential Ecological Risk Index (RI), Spearman correlation analysis, Principal Component Analysis (PCA), and Positive Matrix Factorization (PMF) was applied to evaluate contamination characteristics and quantify source contributions. The results revealed significant spatial–vertical heterogeneity of PTEs, with Zn (up to 153 mg/kg) and Cr (up to 64.6 mg/kg) showing the greatest variability, and strong co-enrichment among Cu, Zn, Pb, and Ni (r > 0.85, p < 0.01). Although the overall ecological risk was low (RI = 83.15–106.69), As contributed the highest proportion of risk (28–35%). PCA indicated distinct grouping patterns among elements, while PMF resolved three major sources: domestic sewage and agricultural runoff, agricultural and coal-combustion inputs, and industrial–traffic emissions. Notably, physicochemical parameters (TP, TN, and COD) played important roles in regulating the mobility and partitioning of PTEs by influencing nutrient-associated adsorption processes, organic matter complexation, and redox-related transformations. These findings highlight the multi-source-driven accumulation mechanisms of PTEs in karst reservoirs and provide a scientific basis for targeted pollution control and watershed management in agriculturally impacted regions. Full article

Two-dimensional materials have broad application prospects in the field of optoelectronic devices. As a next-generation power electronic device, AlN materials have obvious advantages in power processing, and their monolayer structure has excellent optoelectronic properties, which is of great significance for the study of 2D AlN monolayers. Properties such as electronic and optical properties of metal-adsorbed AlN (M-AlN) systems have been systematically investigated using density functional theory from first principles. The results of the energy bands of the M-AlN system indicate that the adsorption of Al, Li, Ag, Au, Bi, Cr, Mn, Na, Pb, Sn, Ti, and K metals makes the monolayer AlN magnetic, the incorporation of two metals, Al and Li, is the transition of the monolayer AlN from a semiconductor to a semi-metal, and the introduction of K metal makes the monolayer AlN transition from a semiconductor to a metal. The work function of the M-AlN system shows that the introduction of the metal reduces the work function of the monolayer AlN, especially for K-AlN, which is reduced by 56.12% compared to the monolayer AlN. In addition, the results of the optical absorption spectra of the M-AlN system revealed that the introduction of the metals made the monolayer AlN exhibit high absorption peaks in the visible and near-infrared regions; in particular, the intensity of the absorption peaks of the Ti-AlN system at 557.8 nm reached 7.4 × 10⁴ cm⁻¹ and the intensity of the absorption peaks of the K-AlN system at 1109.3 nm reached 1.01 × 10⁵ cm⁻¹. This indicates that the introduction of Ti and K metal atoms enhances the absorption properties of monolayer AlN in the visible and near-infrared regions. Finally, the time-domain finite difference using spherical metal nanoparticles is used to excite the localized surface plasmon resonance, and the results show a small area of strong electric field around the electric field hotspot of Cr and Li particles, and a good concentration of the electric field strength in the x and y directions. In summary, the system of metal atoms adsorbed on AlN will be favorable for the design of spintronics, field-emitting devices and solar photovoltaic devices. Full article

Hexagonally ordered mesoporous carbon was ozonized, and the oxidized carbonaceous material was modified with L-arginine. The ozonized and L-arginine-modified carbons were extensively characterized and tested as Pb(II) ion adsorbents, with optimization of Pb(II) solution pH, exposure time, Pb(II) ion concentration and the presence of concurrent ions. Pb(II) adsorption equilibrium was achieved within 5 min at optimal pH = 2.6 or 5.3 for the oxidized and L-arginine-modified carbonaceous materials, respectively. The adsorption kinetics of both investigated materials were best described by the pseudo-first-order model. The maximum adsorption capacity for Pb(II) ions was determined to be 16 mg g⁻¹ (ozonized material) or 45 mg g⁻¹ (L-arginine-modified material). The Langmuir model provided the best fit for the adsorption isotherm data. Fe(III) ions mostly hindered the Pb(II) adsorption (up to 60%) on the L-arginine-modified carbon material. L-arginine-modified carbon was used to enrich Pb(II) from simulated urban roof runoff and its determination using the slurry sampling high-resolution continuum-source graphite furnace atomic absorption spectrometry technique. The developed analytical procedure was characterized by a limit of quantification of 2.63 µg L⁻¹, an enrichment factor of 50, and a recovery rate of 94.8%. Full article

In this work, iron–phosphorus-based composite biochar (FPBC) was prepared by modification with the leachate of spent LiFePO₄ batteries. The effects of solution pH, dosage, adsorption time, initial concentration, and temperature on the adsorption performance of FPBC were investigated by batch adsorption experiments with Pb(II) and Sb(III) as the target pollutants, and the adsorption mechanism was explored using SEM, BET, XPS, FTIR and XRD characterization. The results indicated that as the initial pH of the solution increased, the removal efficiency of FPBC for Pb(II) gradually increased, while the removal efficiency for Sb(III) remained largely unchanged. The removal of Pb(II) and Sb(III) by FPBC fitted the pseudo-second-order kinetic model and the three-step intraparticle diffusion model, indicating that their removal was primarily controlled by chemical adsorption. Isothermal adsorption studies revealed that FPBC adsorption of Pb(II) better fitted the Langmuir and D-R models, suggesting a monolayer-dominated adsorption process. In contrast, adsorption of Sb(III) fitted the Langmuir, Freundlich, and Temkin models, suggesting a combination of monolayer and multilayer adsorption characteristics. The maximum adsorption capacities of FPBC for Pb(II) and Sb(III) were 312.54 mg·g⁻¹ and 219.20 mg·g⁻¹ at 30 °C, which were approximately 12.85 and 3.37 times those of commercial corn stalk biochar (BC). Thermodynamic analysis confirmed that the removal of Pb(II) and Sb(III) by FPBC was a spontaneous and endothermic process. In addition, FPBC demonstrated strong selective adsorption of Pb(II) in the binary co-adsorption system of Pb(II) and Sb(III). Mechanism studies indicated that Pb(II) removal primarily occurred through co-precipitation, complexation, ion exchange, and electrostatic adsorption, while Sb(III) was mainly adsorbed by FPBC via redox reactions and complexation. Therefore, this work not only provides a low-cost, high-performance adsorbent for the remediation of water contaminated with Pb(II) and Sb(III), but also opens up new avenues for the resource recovery of the leachate of spent LiFePO₄ batteries. Full article

The long-term accumulation of phosphogypsum (PG) stacks has caused combined pollution of total phosphorus (TP), fluoride (F⁻), metals and metalloids (MMs), posing a severe threat to regional ecological security. To clarify the migration characteristics of pollutants in PG stacks, water leaching experiments and environmental risk assessment were conducted in 21 typical PG stacks in Southwest China. The spatial differentiation and vertical migration characteristics of pollutants under various coverage measures (high-density polyethylene (HDPE) film covering, soil covering, a composite of film–soil covering, and open-air storage) at different pH conditions were systematically analyzed. Results indicated that under open-air stockpiling conditions, the surface accumulation of TP and F⁻ was the most significant among all covering measures, corresponding to the highest environmental risk. In contrast, the membrane–soil composite covering exhibited the optimal inhibitory effect on the surface diffusion of TP and F⁻, but was less effective for metal and metalloid enrichment. Under acidic conditions (pH < 6), the vertical migration capacity of TP, F⁻, and MMs (Cu, Cd, Cr, Pb, and Zn) increased, leading to enrichment in the deep layers of the stack. With the increase in pH, the calcium-mediated precipitation–adsorption effect created a “geochemical barrier”, facilitating the solid-phase fixation of pollutants. A significant positive correlation among pollutants indicates synergistic release and fixation behaviors. In addition, a pH-controlled P-F-MM source-to-sink conceptual model was established, outlining the dissolution, precipitation, adsorption, fixation and re-enrichment pathway from fresh stock to leachate. This work provides insights for optimizing cover designs and pollution control strategies. Full article

The accumulation of microplastics (MPs) in agricultural soils and atrazine in agricultural soils creates compound pollution that severely threatens soil health. The present study aimed to evaluate the effect of polyethylene (PE), polyvinyl chloride (PVC), and polybutylene succinate (PBS) on the adsorption and degradation of atrazine in yellow-brown and black soil. Batch adsorption kinetic and isotherm experiments were conducted in two distinct soils amended with MPs. A 90-day degradation experiment was performed to monitor atrazine persistence and the activities of key soil enzymes. The adsorption process was best described by the pseudo-second-order model and the Freundlich isotherm model, suggesting dominant chemisorption and multilayer adsorption on heterogeneous surfaces of the soil–MP composites. All MPs significantly enhanced the adsorption capacity for atrazine (6.80–39.93 mg kg⁻¹), with the order PBS > PE > PVC. Furthermore, the degradation of atrazine was impeded by all MPs, with PVC exhibiting the strongest inhibitory effect. The half-life of atrazine ranges from 22.97 to 81.76 days in two soils. The presence of MPs also influenced soil enzyme activities and the effects varied by MP type and soil property. These results demonstrate that MPs can modify the adsorption and persistence of atrazine in soil, thereby increasing its environmental risk. This study provides valuable insights for the long-term ecological risk assessment of co-existing MPs and pesticide pollution in terrestrial environments. Full article

In recent decades, ion-adsorption-type rare earth element (iREE) deposits have been widely documented in the weathering crusts of granitic and volcanic rocks and their geological characteristics and genetic mechanisms extensively studied. Ion-adsorption-type REE mineralization was documented for the first time in the weathered crust overlying the epimetamorphic rocks in Ningdu County, China. In contrast to well-documented granite-derived weathering profiles, investigations of epimetamorphic rocks as protoliths for such REE deposits remain limited, particularly regarding the mineralogy of REE-bearing phases and the geochronology and geochemistry of their parent rocks. To address this gap, the present study combines comprehensive petrographic and mineralogical analyses of REE-mineralized Shenshan Formation phyllites with the U–Pb dating of zircon and apatite and trace element geochemical investigations. U–Pb zircon and apatite geochronology yields a protolith age of ca. 785 Ma for Shenshan Formation metamorphic rocks, consistent with mid-Neoproterozoic magmatism. REE-bearing minerals in the Shenshan Formation phyllites comprise allanite-(Ce), apatite, cerianite-(Ce), monazite-(Ce), rhabdophane-(La), rutile, Y-bearing thorianite and xenotime-(Y). Among these, apatite is the most abundant and likely the principal source of ionic REEs in the deposit. Ti-in-zircon thermometry indicates crystallization temperatures of 641–749 °C (mean ~704 °C), reflecting a prolonged magmatic–hydrothermal evolution. This extended history chiefly controlled the differentiation and redistribution of rare earth elements (REEs), thus governing their availability for subsequent supergene enrichment. Zircon-based oxygen fugacity (fO₂) estimates a range from −31.4 to −9.9 (mean −17.9), consistent with reduced magmatic conditions. Trace element correlation diagrams for zircon and apatite indicate that the intrusion underwent an extensive fractional crystallization of accessory phases (zircon, monazite, apatite, titanite, rutile) and plagioclase. The distribution patterns of trace elements further suggest that the Shenshan Formation protolith formed in a continental margin arc or arc-related orogenic belt setting, with geochemical signatures characteristic of an S-type granite. The Shenshan Formation phyllites in southern Jiangxi exhibit high REE abundances and host a labile assemblage of weatherable REE-bearing minerals, providing an optimal material framework for ion-adsorption-type REE deposits and indicating substantial mineralization potential. Full article

Immobilized microorganism technology offers a promising approach for remediating heavy metal-contaminated soils. This study developed a novel bio-mineral composite (B-AM) by coupling acid-modified maifanite (AM) with Bacillus mucilaginosus to enhance lead (Pb) immobilization. Comparative experiments demonstrated that B-AM outperformed conventional amendments, including oyster shell, pristine maifanite, AM and B. mucilaginosus in Pb immobilization. The B-AM treatment optimized soil pH, improved soil fertility with increases in available potassium (1.06-fold) and available phosphorus (1.28-fold). Additionally, B-AM transformed Pb into more stable fractions, reducing labile Pb fractions by 52.52% while increasing the residual fraction by 88.36%. These improvements resulted in an 83.24% reduction in Pb accumulation and a 63.95% increase in the fresh root weight of radish. Mechanistic insights revealed that the enhanced remediation performance stems from both the individual contributions of AM (adsorption capacity) and B. mucilaginosus (biosorption and biomineralization) and their synergistic interaction. Specifically, AM acts as a carrier and pH buffer, promoting microbial proliferation and reducing Pb remobilization from cell lysis. The resulting sustained microbial activity further leads to the formation of stable Pb minerals. Collectively, our results establish a theoretical and practical basis for using B-AM to remediate Pb-contaminated soils. Full article

In this study, a novel material was obtained by functionalizing shredded maize stalk (MS) with Alizarine Red S (ArS), a complexing agent that contains −OH and −C=O groups in its structure (MS-ArS). The obtained MS-ArS was employed in adsorption studies for Mn²⁺, Pb²⁺, Cu²⁺, Cr³⁺, Zn²⁺, and Fe³⁺ (Mⁿ⁺) removal from mixed aqueous matrices. Initially, complex formation between (Mⁿ⁺) and ArS in buffer solution at pH 4 and 10 was investigated using the UV-Vis spectrometric method. Continuous, the functionalization process of MS with ArS was tested at several pH values (2, 4, 6, 8, and 10) using a batch technique. It was observed that the best functionalization of MS with ArS was obtained at pH = 2. Subsequently, Mⁿ⁺ adsorption onto the MS-ArS mass was tested separately at pH 4 and 10. The study achieved that Mⁿ⁺ adsorption proved to be pH dependent. The results confirmed that at pH = 10, Mⁿ⁺ adsorption was increased, compared with pH = 4. MS-ArS has affinity for Mⁿ⁺ in the following order Fe³⁺ > Cu²⁺ > Zn²⁺ > Mn²⁺ > Pb²⁺ > Cr³⁺. Experimental data revealed remarkable desorption rates when 0.5 M HCl was used. After five adsorption/desorption cycles of Mⁿ⁺, the removal capability of MS-ArS was preserved. Overall, the potential of MS-ArS for effective Mⁿ⁺ removal/reuse makes it a sustainable polymer for wastewater treatment applications. Full article

Landfill leachate, a byproduct of municipal solid waste treatment, typically contains hazardous substances such as toxic metals (e.g., lead) and eutrophication agents (e.g., phosphate). This study addresses the pressing challenge of polishing complex wastewater, such as landfill leachate, through the development of a novel ternary layered double hydroxide (LDH). As CaFe-LDHs are known to have an affinity for anions, and CoFe-LDHs have shown an affinity for toxic metal cations, CoCaFe-LDH was proposed to integrate both functionalities. The LDH was anchored on activated biochar to synthetize the novel composite adsorbent CoCaFe-LAB. Key operational parameters (including initial pH, adsorbent dosage, contact time, initial adsorbate concentration, presence of coexisting ions, and regeneration capability) were systematically evaluated. Kinetic and equilibrium analyses revealed that Elovich and Sips models, respectively, best described the adsorption behavior of Pb²⁺ and PO₄³⁻, indicating a heterogeneous adsorption system. Maximum adsorption capacities in synthetic solutions reached 140.81 mg Pb²⁺ g⁻¹ and 25.19 mg PO₄³⁻ g⁻¹ at 45 °C. The CoCaFe-LAB composite proved highly effective, particularly for lead removal. In real effluent tests, the adsorbent achieved complete phosphate removal (100%) from electro-oxidized landfill leachate at a dosage of 2.0 g L⁻¹, confirming its practical applicability and efficiency. Full article

Magnetic nanomaterials (MNMs) have been adopted as effective platforms for water remediation owing to their excellent surface-area-to-volume ratios, tunable surface chemistry, and magnetic separability. This review highlights the recent progress made in the synthesis, properties, and environmental applications in the removal of organic and inorganic contaminants using magnetic nanoparticles (MNPs) and one-dimensional magnetic nanofibers. Demonstrated removal rates of organic contaminants such as dyes, pharmaceuticals, and pesticides are often up to 85–100% under laboratory conditions, with adsorption capacities of 580 mg·g⁻¹ for melanoidin, 397.43 mg·g⁻¹ for Congo Red, and 392.64 mg·g⁻¹ for tetracycline. For heavy metals such as As(V), Cd(II), Cr(VI) and Pb(II), efficiencies are generally between 90–99% with maximum adsorption capacities of 909.1 mg·g⁻¹ for Pb(II). In particular, the review compares major synthesis routes such as coprecipitation, hydrothermal, solvothermal, thermal decomposition, sol–gel, microwave, and green methods by evaluating their effect on particle size (6–50 nm), magnetic properties (saturation magnetization up to ~101 emu·g⁻¹), and removal performance. The four principal mechanisms are described in this paper—adsorption, filtration, transformation, and photocatalysis—giving special emphasis to the advantages of magnetic recovery and advanced oxidation processes. Although most studies remain at the laboratory scale, MNMs demonstrate strong potential for scalable wastewater treatment, provided that toxicity, life-cycle impacts, and matrix effects are carefully evaluated. Full article