Search Results (441)

The proposed work assesses the potential of Paulownia leaf-derived materials as sustainable adsorbents for the efficient removal of Pb(II) from aqueous solutions. Raw Paulownia leaf biomass (PL), biochar obtained by pyrolysis at 400 °C (BC), and (3-aminopropyltriethoxysilane)-functionalized oxidized biochar (APTES-OBC) were prepared. Their physicochemical properties were characterized using SEM/EDS and FTIR, and their Pb(II) adsorption performances were comprehensively investigated through pH-dependent, adsorbent dosage, kinetic, isotherm, thermodynamic, and ion-exchange studies and compared. The obtained results showed that APTES functionalization significantly improved Pb(II) adsorption performance, with adsorption capacities following the order APTES-OBC (291.86 mg/g) > BC (121.82 mg/g) > PL (104.29 mg/g). The Sips isotherm best described Pb(II) adsorption on the carbonized adsorbents, indicating heterogeneous adsorption, whereas the Redlich-Peterson isotherm model showed the best agreement with Pb(II) adsorption on the PL. The adsorption kinetics were most accurately represented by the pseudo-second-order model, indicating that chemisorption-related interactions played a dominant role during Pb(II) uptake. Diffusion studies revealed a three-stage adsorption mechanism. Ion-exchange experiments confirmed the release of Ca²⁺, K⁺, Mg²⁺, and Na⁺ ions, indicating that ion exchange contributes to the Pb(II) adsorption mechanism. However, the lower release of these ions from APTES-OBC, despite its superior adsorption capacity, indicates that Pb(II) removal is predominantly governed by surface complexation and coordination with amino-functionalized silane groups following APTES functionalization. Overall, the findings highlight a sustainable approach for the valorization of Paulownia leaf waste into efficient and environmentally safe adsorbents for heavy metal elimination from water systems. Full article

A new method is described for the determination of vanadium using adsorptive stripping voltammetry of V(V) complexed with cupferron at a CNTs/SGC electrode modified with a lead film. The CNTs/SGC electrode is based on carbon nanomaterials such as carbon nanotubes and spherical glassy carbon, which form the foundation of modern sensor technology. Optimal conditions of adsorptive voltammetric measurement were found to be modification/accumulation potential and time of −1.6 V and 60 s, respectively, and supporting electrolyte of 0.2 mol/L NaAc–HAc buffer (pH 5.3) containing 0.3 mmol/L cupferron and 0.15 mmol/L Pb(II). The response of the system was found to be linear in a range of V(V) concentrations from 0.25 nmol/L to 10 nmol/L. The detection limit was found to be 0.08 nmol/L. The selectivity of the procedure was determined by analysing the effect of other interfering ions on the vanadium analytical signal. The method was successfully validated by analysing natural environmental waters. Full article

Lead (Pb²⁺) and cadmium (Cd²⁺) are among the most hazardous heavy metal pollutants in wastewater owing to their high toxicity, environmental persistence, and detrimental impacts on human health and aquatic ecosystems. In this study, a novel ternary magnetic composite, SnFe₂O₄/activated carbon/polypyrrole (SnFe₂O₄/AC/PPy), was effectively synthesized and tested as an effective adsorbent in the removal of Pb²⁺ and Cd²⁺ from aqueous water. The composite was prepared by depositing spinel SnFe₂O₄ nanoparticles on activated carbon, followed by in situ polymerization of polypyrrole to enhance surface functionality and adsorption affinity. The successful fabrication of the porous SnFe₂O₄/AC/PPy hybrid composite was confirmed through FTIR, XRD, SEM–EDS, BET, XPS, and VSM characterization. The composite demonstrated a relatively high surface area (352.3 m²/g) and adequate magnetic responsiveness (12.33 emu/g), ensuring facile magnetic separation following wastewater treatment. Batch adsorption experiments showed great removal efficiency of 95.02 and 92.48% for Pb²⁺ and Cd²⁺ ions, respectively, at optimum conditions. The adsorption equilibrium data followed the Langmuir isotherm model with maximum adsorption capacities of 187.07 mg/g for Pb²⁺ and 96.45 mg/g for Cd²⁺ ions, which were attributed to monolayer adsorption on homogenous active sites. The kinetic and isothermal model indicated that the adsorption process was controlled by the combination of physical and chemical interactions. Thermodynamic parameters showed negative Gibbs free energy and enthalpy changes (ΔH° = −49.74 kJ/mol for Pb²⁺ and −38.82 kJ/mol for Cd²⁺ ions), confirming the spontaneous and exothermic nature of adsorption. Furthermore, the increasingly negative ΔG° values at lower temperatures indicated that the adsorption was thermodynamically more favorable under cooler conditions. According to the regeneration studies, the composite maintained a high removal efficiency after five consecutive cycles. In general, SnFe₂O₄/AC/PPy composite has good potential as a stable, reusable, and high-performance adsorbent to treat heavy metal wastewater. Full article

In this work, we report an example of tuning the photophysical properties of a polypyridine ruthenium(II) complex via the coordination of a second cation. A new ruthenium(II) complex contains a thiacrown-ether fragment that allows selective binding of additional metal cations (Ba²⁺, Cd²⁺, Pb²⁺), leading to pronounced changes in the optical and electronic properties of the bimetallic system. Spectroscopic and electrochemical studies reveal that the monoruthenium precursor displays dual excitation pathways involving either intraligand charge transfer (ILCT) or triplet metal-to-ligand charge transfer (³MLCT) excited states. Upon coordination of a second metal ion, the ILCT channel is suppressed, and only the ³MLCT state remains emissive, resulting in a significant increase in phosphorescence quantum yields (up to 22.6% in degassed solutions) for the bimetallic derivative. Time-resolved emission studies confirm the conversion from biexponential to monoexponential luminescence decay upon complexation. Electrochemical analysis and density functional theory (DFT) calculations support the hypothesis that cation binding alters the electron density distribution within the chromophore, stabilizing the MLCT pathway. These results demonstrate that incorporation of a second cation provides an effective strategy to control excited-state dynamics in ruthenium complexes, offering opportunities for the rational design of photosensitizers and photofunctional materials. Full article

The P(IA-HBP-AA-AM)/MMT composite was successfully synthesized via in situ polymerization and characterized using FTIR, XRD, TGA, and other techniques. The material was then applied as an adsorbent for the removal of heavy metals from simulated mining-contaminated water (prepared based on the typical ionic composition of real mining wastewater). Static adsorption experiments revealed that P(IA-HBP-AA-AM)/MMT composite could efficiently remove Pb(II) from contaminated water, and the adsorption behavior was well described by the pseudo-second-order kinetic model and the Langmuir isotherm model. Thermodynamic analysis indicated that the adsorption of Pb(II) onto the P(IA-HBP-AA-AM)/MMT composite was an endothermic and spontaneous process. At pH = 4.5 and T = 45 °C, the maximum adsorption capacity obtained from model fitting was 249.38 mg/g. The material exhibited strong selectivity for Pb(II), even in the presence of competing metal ions such as Cd(II), Zn(II), Al(III), Fe(III), K(I), and Na(I). Moreover, after five adsorption–desorption cycles, it still retained approximately 90% of its Pb(II) removal efficiency. Furthermore, dynamic adsorption experiments showed that the saturation adsorption capacity of Pb(II) reached 178.7 mg/g, with a column utilization efficiency of approximately 41%. These findings demonstrate the promising potential of P(IA-HBP-AA-AM)/MMT composite for the removal of Pb(II) from mining-contaminated water. Full article

The sustainable recovery of high-value metals from wastewater has garnered significant attention in light of the circular economy and environmental preservation. Because of its appealing characteristics, membrane separation technology is essential for the sustainable and effective recovery of valuable metals from wastewater, in contrast to conventional methods, which are chemical- or energy-intensive. In this study, a rational design approach was utilized to synthesize a metal–organic framework (MOF) using a deep eutectic solvent (DES) as a mediating medium to control the reaction of framework formation and particle properties. While DESs have been widely used for the physical modification of materials, their role as a chemically modifying medium during MOF synthesis for structural tailoring remains less explored. This synthesized MOF (DM-Zn-PDC@MOF) was further introduced as filler in polysulfone (PSf)-based mixed matrix membranes (MMMs). The performance of DM-Zn-PDC@MOF within the polymer matrix was examined. Several characterization techniques were used to thoroughly analyze the morphological, chemical, and physical characteristics of the MMMs and DM-Zn-PDC@MOF. The addition of the filler material significantly enhanced the membrane characteristics, including pure water flux, hydrophilicity, porosity, surface roughness, pore size, and heavy metal resource recovery in comparison with the pristine membrane. Stable incorporation of the filler within the membrane matrix was indicated by much less filler leaching (<5%) at all concentrations. With DM-Zn-PDC@MOF loading, the pure water flux increasedmore than nine times from 102.8 L/m²h (M-0) to 971.5 L/m²h (M-4). The functionalized membranes showed better flux retention in high-value heavy metal resource recovery using simulated wastewater: 871.8 L/m²h when filtering a Pb(II) ion solution (compared to M-0 with flux 120.6 L/m²h) and 526.8 L/m²h when filtering a Cr(III) ion solution (compared to M-0 with flux 97.1 L/m²h). These values represented approximately 7-fold and 5-fold improvements, respectively. Overall, Pb⁺² > Cr⁺³, but the rejection of Cr(III) ions was also improved, when compared with M-0. The high flux of the membrane makes it easier to process large volumes and concentrate metals in the retentate, turning diluted contaminated streams into a concentrated feedstock for subsequent recovery procedures. Full article

With the increasing levels of toxic heavy metals such as Pb(II) and Cd(II), their discharge poses serious threats to environmental safety and human health, necessitating efficient remediation technologies. Biochar has emerged as a promising eco-friendly adsorbent; however, its adsorption performance is constrained by interactions among material properties, environmental conditions, and ion specificity. Conventional machine learning (ML) models are typically built on single-metal-ion datasets, limiting their ability to leverage shared information across related adsorption scenarios. To address this limitation, this study proposes a descriptor-based ML framework for Pb(II)–Cd(II) adsorption prediction, in which ion-related physicochemical descriptors, such as electronegativity and hydrated ionic radius, are incorporated in place of discrete ion labels to enable ion-specific modeling. An Optuna-optimized CatBoost model achieved high predictive accuracy (R² = 0.952, RMSE = 9.80) and demonstrated improved performance on both Pb and Cd subsets compared with single-ion models. SHAP analysis reveals the model is consistent with known adsorption-related factors. Uncertainty quantification was incorporated to constrain predictions and enhance robustness. Ultimately, this study provides a robust data-driven baseline for heavy metal adsorption modeling, offering mechanistic insights into biochar–metal interactions and demonstrating a physicochemical descriptor approach that supports future extensions to broader multi-ion systems. Full article

Metalloporphyrins play an important role in biomedicine, catalysis, and energy, among other fields, due to their structural complexity and functional diversity. In this study, GO was used as the precursor support and chitosan was employed to reduce and functionalize GO into chitosan-functionalized rGO. Furthermore, metalloporphyrins were covalently linked to the amino side chains of chitosan via an amide crosslinking method, and a series of metalloporphyrin–chitosan-functionalized rGO nanocomposites were designed and synthesized. A set of poly(metalloporphyrin–chitosan)-functionalized rGO working electrodes was constructed by drop-coating onto glassy carbon electrodes, and their electrocatalytic performance toward dopamine was investigated in PBS solution. Finally, zinc(II) porphyrin, with the best performance, was selected as the core catalytic unit to fabricate an enzyme-free dopamine sensor. Under optimal working conditions, the sensor exhibited a sensitivity of 0.30 mA mM⁻¹cm⁻², a linear detection range of 0.001~1.0 mM, and a low detection limit of 0.05 μM (S/N = 3). The sensor showed anti-interference ability against various interfering ions and electroactive substances, as well as good stability and repeatability. Full article

Heavy metal pollution in water threatens ecosystems and human health, necessitating efficient, low-cost, and sustainable remediation technologies. A manganese-modified bamboo biochar (Mn-BC) was synthesized via impregnation of raw biochar in KMnO₄ followed by pyrolysis at 500 °C, and its adsorption ability was systematically evaluated for Pb(II) and Cr(VI) removal through batch adsorption experiments investigating the effects of solution pH (2–9), adsorbent dosage (0.1–0.9 g in 20 mL), contact time (0–50 min), initial metal concentration (20–100 mg L⁻¹), and temperature (25–50 °C). SEM/TEM-EDS and XRD confirmed successful Mn incorporation as MnO_x phases, while textural analysis showed improved porosity after modification, with the BET surface area and total pore volume increasing from 77.28 m² g⁻¹ to 123.51 m² g⁻¹ and from 0.041 cm³ g⁻¹ to 0.063 cm³ g⁻¹, respectively. Batch adsorption experiments demonstrated strong pH dependence, with optimum removal at pH 8 for Pb(II) (91.87%) and pH 5 for Cr(VI) (88.2%). Adsorption was rapid within the first 30 min and reached equilibrium. A pseudo-second-order (PSO) model provided the best kinetic description (R² = 0.99) with calculated q_e values of 19.98 mg g⁻¹ for Pb(II) and 19.13 mg g⁻¹ for Cr(VI). Isotherm analysis yielded Langmuir monolayer capacities of 37.24 mg g⁻¹ (Pb(II)) and 16.39 mg g⁻¹ (Cr(VI)), with Pb(II) better described by Freundlich behavior and Cr(VI) closely fitting Langmuir assumptions. Thermodynamic results indicated endothermic adsorption (ΔH° = 41.98 and 29.67 kJ mol⁻¹ for Pb(II) and Cr(VI)) and increased interfacial randomness (ΔS°), with adsorption becoming more favorable at higher temperature (maximum removal at 50 °C: 93.21% Pb(II), 87.37% Cr(VI)). Mn-BC maintained >60% efficiency after five regeneration cycles. Mechanistically, Pb(II) removal was primarily governed by ion exchange and surface complexation, whereas Cr(VI) removal involved electrostatic attraction, partial reduction to Cr(III), and subsequent complexation on oxygenated and Mn–O sites. Overall, these findings demonstrate that Mn-BC is a practical, reusable, and competitive adsorbent for the efficient removal of Pb(II) and Cr(VI) from wastewater, supporting sustainable water treatment strategies. Full article

Graphitic carbon nitride (g-C₃N₄), an emerging metal-free semiconductor material, has attracted considerable attention in the field of photoelectrochemical (PEC) sensing due to its unique electronic structure, excellent chemical stability, and visible-light responsiveness. This article systematically reviews recent advances in research on g-C₃N₄-based PEC sensors applied to water environment monitoring. First, the fundamental physicochemical properties of g-C₃N₄ are introduced, along with its advantages and limitations in PEC sensing applications. Subsequently, four main performance enhancement strategies are outlined: heterojunction construction (including type II, Z-scheme, and S-scheme heterojunction), elemental doping and defect engineering, morphology control and nanostructure design, as well as various signal amplification approaches such as self-powered systems, dual-mode detection, and cyclic amplification. Furthermore, the current application status of these sensors in detecting typical water pollutants, including heavy metal ions (e.g., Pb²⁺, Cu²⁺, Cd²⁺, Hg²⁺), antibiotics (e.g., tobramycin, norfloxacin, kanamycin), pesticide residues (e.g., chlorpyrifos, atrazine, glyphosate), and pathogenic microorganisms (e.g., Salmonella, Candida albicans), is comprehensively reviewed, with particular emphasis on detection sensitivity, selectivity, and real-sample performance. Finally, the remaining challenges in terms of long-term stability, anti-interference capabilities in complex matrices, portability, and multifunctional integration are analyzed, and future development directions are proposed, including smartphone-based intelligent sensing, CRISPR/Cas12a-assisted signal amplification, and multi-target high-throughput detection. This review aims to provide a reference for the rational design and practical application of g-C₃N₄-based PEC sensors in the field of water environment monitoring. Full article

Gelatin–alginate composite hydrogels are some of the most prevalent bioinks used for extrusion-based three-dimensional (3D) bioprinting because of their combined bioactivity and ability to ionically crosslink. Ionically crosslinked gelatin–alginate constructs containing human bone marrow–derived mesenchymal stem cells (hBM-MSCs) were characterised over time under standardised in vitro conditions to assess physicochemical properties and resultant cell behaviour. Water uptake and degradation were quantified over time in phosphate-buffered saline (PBS) and collagenase type II media for up to 21 days. Cell viability and metabolic activity were quantified, and osteogenic gene expression (RUNX2, COL1A1, OCN) was assessed. Raman spectroscopy and compressive mechanical characterisation were performed. Collagen and glycosaminoglycan-related peaks were observed from extracellular matrix (ECM)-associated components, with an increased presence of protein-associated signatures later in culture. Hydrogels displayed nonlinear elastic behaviour with increased stress after longer incubation times, suggesting no degradation of mechanical integrity over the duration of the study. Hydrogels experienced rapid hydration followed by decreased swelling over time, with a maximum swelling ratio at 24 h. Degradation rates significantly increased over longer incubation times (p < 0.001) and in collagenase media compared to PBS (p < 0.001). Observed differences were likely due to both ion-exchange-mediated network disassembly and the dissolution of gelatin components. Cell metabolic activity decreased under osteogenic culture conditions, while changes in osteogenic marker expression were sequential, suggesting a transition from proliferation to early osteogenic commitment in this 3D system. This work provides both physicochemical and biological characterisation of a commonly utilised gelatin–alginate bioink system, to provide future optimisations within the field of extrusion-based bone tissue engineering, a reproducible baseline for future optimisation of bioink systems in extrusion-based bone tissue engineering. Full article

Agricultural byproducts cellulose-rich (~40%) sugarcane bagasse (SCB) and rice husk (RH) wastes may be used as fiber sources in biomaterials manufacturing. The hybrid biomass fibers are two kinds of fibers that should generate a biocomposite according to the functions and physical, chemical, and mechanical properties of materials. The biocomposite was synthesized using the solvothermal method. The FeCl₃.6H₂O was dissolved in C₂H₃NaO₂ and C₆H₆O₂ and later heated at 60 °C. The SCB and RH fiber (1:1) are added with HDMA into the mixture, then placed in a Teflon stainless steel autoclave at 200 °C for 6 h. The biocomposite was employed as a green adsorbent to treat wastewater through simultaneous adsorption. The biocomposite had 2.637 mmol g⁻¹ of amine groups, which makes smaller magnetic particles and a high surface area of up to 79%. The pseudo-second-order kinetic model followed the Cu(II) and Pb(II) ions adsorption for 4 h (240 min), and the maximum adsorption capacities were 35.042 mg g⁻¹ and 67.127 mg g⁻¹, respectively, at the pH of 5. The biocomposite not only got rid of metal ions, but it also worked well to get rid of dye, total suspended solids (TSSs), and chemical oxygen demand (COD) as pollutants in wastewater. The biocomposite still worked well after being used four times. Full article

With the rapid intensification of industrial and agricultural activities, water contamination by heavy metal ions has emerged as a critical global challenge, gravely imperiling ecosystem stability and public health. Among the various remediation technologies, adsorption has been widely adopted due to its high efficiency, low-cost water treatment, and simplicity of operation. However, conventional inorganic or synthetic adsorbents often exhibit poor degradability and pose a risk of secondary contamination, substantially limiting their sustainable application. Consequently, the development of environmentally benign and renewable adsorbent materials has become a central research focus in this field. Recently, cellulose-based composite hydrogels, derived from renewable resources and characterized by excellent eco-friendliness and highly tunable three-dimensional porous structures, have attracted considerable attention as promising green adsorption materials. These hydrogels demonstrate outstanding performance in the efficient sequestration of heavy metal contaminants from aqueous environments. This review systematically summarizes recent advances in cellulose-based composite hydrogels for heavy metal removal, to elucidate the structure–performance relationships linking material fabrication strategies, structural modulation, and adsorption efficiency. First, we outline the principal construction approaches, including physical crosslinking, chemical modification, and supramolecular self-assembly, and comprehensively analyze how different synthesis routes regulate pore architecture, mechanical properties, and the distribution of surface functional groups. Second, the underlying adsorption mechanisms, primarily coordination complexation, electrostatic interactions, and ion exchange, are discussed in detail. Finally, recent studies on the adsorption of cationic heavy metals (e.g., Pb(II), Cu(II), and Cd(II)) and anionic oxyanions (e.g., As(III) and Cr(VI)) are critically reviewed, with particular emphasis on the relationships between selective adsorption performance, material design principles, and specific recognition mechanisms. Overall, this review provides a theoretical foundation and practical guidance for the design and development of next-generation water treatment materials with high adsorption capacity, excellent selectivity, non-toxicity, and strong environmental compatibility, followed by future research recommendations. Full article

The safety of drinking water has a significant impact on human life and health, with the common presence of Pb (II) causing harm to human beings. The physical adsorption method is an effective means of removing Pb (II) from water. In this study, three types of biochar were produced through a one-step process using agricultural and forestry wastes (rape straw, bagasse, and walnut shell) as raw materials and KHCO₃ as a co-carbonization agent. The resulting biochar exhibited remarkable adsorption capacities for Pb (II). The biochar prepared via a single carbonization process demonstrates excellent adsorption performance towards Pb (II). The adsorption capacity of bagasse-derived biochar reaches 76.94 mg/g, which is 4.5-fold higher than that of the control. For walnut shell-derived biochar, the adsorption value attains 124.90 mg/g, representing a 7.5-fold enhancement. Notably, rape straw-derived biochar demonstrates the maximum adsorption capacity, up to 265.69 mg/g. Mechanistic analysis reveals that the adsorption of rape straw biochar is dominated by ion exchange, while also being influenced by physical adsorption, coprecipitation, and electrostatic attraction. Intriguingly, in this study, the sole use of KHCO₃ as a co-carbonization agent remarkably increases the specific surface area of the biochar and facilitates the formation of micropores. Without the need for pre-carbonization, this approach substantially boosts the Pb (II) adsorption capacity of the biochar. This one-step carbonization strategy exhibits distinct operational convenience and cost-effectiveness, providing promising materials for the low-cost removal of Pb (II) in natural water bodies and open environments, while also offering a viable technical route for the fabrication of high-performance biochar for heavy metal remediation. Full article

Urban stormwater runoff often contains toxic metals that threaten aquatic environments. Meanwhile, the large quantities of drinking water treatment residuals (DWTRs) generated worldwide offer opportunities for sustainable reuse as pollutant removal materials. In this study, a manganese sand-modified drinking water treatment residual particle (RDP-M) was prepared from DWTRs and manganese sand for Pb(II) removal from water. Characterization by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) showed that RDP-M had a rough surface morphology and abundant oxygen-containing functional groups, which provided adsorption sites. Batch experiments showed that the maximum Pb(II) adsorption capacity of RDP-M reached 2.79 mg g⁻¹ at 298 K and pH 7.0, which was about 48% higher than that of the unmodified particles (RDP). The adsorption process followed the pseudo-second-order kinetic model and the Langmuir isotherm model, indicating a chemisorption-dominated process. Thermodynamic analysis further showed that the process was spontaneous and exothermic. RDP-M maintained stable Pb(II) removal over a wide pH range, showed low sensitivity to coexisting ions, and retained high efficiency during repeated use. These results demonstrate that RDP-M has potential as a sustainable granular material for stormwater treatment and waste resource valorization. Full article