Search Results (786)

The preparation and use of iron oxide magnetic nanoparticles for water remediation is a widely investigated research field. To improve the efficacy of such nanomaterials, different synthetic processes and functionalization methods have been developed in the framework of green chemistry to exploit their magnetic properties and adsorption capacity in a sustainable way. In this work, iron oxide magnetic nanoparticles embedded in cross-linked sodium alginate beads designed to clean water from metal ions were magnetically characterized. In particular, the effect of copper adsorption on their magnetic properties was investigated. The magnetic characterization in a DC field of the beads before adsorption showed the presence of a superparamagnetic state at 300 K—a state that was also preserved after copper adsorption. The main differences in terms of magnetic properties before and after Cu²⁺ adsorption were the reduction of the magnetic signal (observed by comparing the saturation magnetization) and a different shape of the blocking temperature distribution obtained by magnetization versus temperature measurements. The evaluation of the reduction in magnetization can be important from the application perspective since it can affect the efficiency of the beads’ removal from the water medium after treatment. Full article

Accelerated industrialization and surging energy demands have led to continuously rising atmospheric CO₂ concentrations. Developing sustainable methods to reduce atmospheric CO₂ levels is crucial for achieving carbon neutrality. Concurrently, the rapid development of new energy vehicles has driven a significant increase in demand for lithium-ion batteries (LIBs), which are now approaching an end-of-life peak. Efficient recycling of valuable metals from spent LIBs represents a critical challenge. This study employs conventional hydrometallurgical processing to recover valuable metals from spent LIBs. Subsequently, Ni-doped Co₃O₄ (Ni:Co₃O₄) supported on the natural mineral attapulgite (ATP) was synthesized via a sol–gel method. The incorporation of a small amount of Ni into the Co₃O₄ lattice generates oxygen vacancies, inducing a localized surface plasmon resonance (LSPR) effect, which significantly enhances charge carrier transport and separation efficiency. During the photocatalytic reduction of CO₂, the primary product CO generated by the Ni:Co₃O₄/ATP composite achieved a high production rate of 30.1 μmol·g⁻¹·h⁻¹. Furthermore, the composite maintains robust catalytic activity even after five consecutive reaction cycles. Full article

Molasses, a by-product of raw sugar production, is widely used as a cost-effective carbon and nutrient source for industrial fermentations, including the production of baker’s yeast (Saccharomyces cerevisiae). Due to the cost and limited availability of molasses, efforts have been made to replace molasses with cheaper and more readily available substrates such as corn syrup. However, the quality of dry yeast drops following the replacement of molasses with corn syrup, despite the same amount of total sugar being provided. Our understanding of how molasses replacement affects yeast physiology, especially during the dehydration step, is limited. Here, we examined changes in gene expression of a strain of baker’s yeast during fermentation with increasing corn syrup to molasses ratios at the transcriptomic level. Our findings revealed that the limited availability of the key metal ions copper, iron, and zinc, as well as sulfur from corn syrup (i) reduced their intracellular storage, (ii) impaired the synthesis of unsaturated fatty acids and ergosterol, as evidenced by the decreasing proportions of these important membrane components with higher proportions of corn syrup, and (iii) inactivated oxidative stress response enzymes. Taken together, the molecular and metabolic changes observed suggest a potential reduction in nutrient reserves for fermentation and a possible compromise in cell viability during the drying process, which may ultimately impact the quality of the final dry yeast product. These findings emphasize the importance of precise nutrient supplementation when substituting molasses with cheaper substrates. Full article

An anion exchange-assisted technique was used for the synthesis of platinum-decorated SnO₂ supports, providing nanocatalysts with enhanced activity for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). In this study, a series of SnO₂ supports, namely SnA (synthesized almost at room temperature), SnB (hydrothermally treated at 180 °C), and SnC (annealed at 600 °C), are systematically investigated, all loaded with 1 mol% Pt from H₂PtCl₆ under identical mild conditions. The chloride ions from the SnCl₄ precursors were efficiently removed via a strong-base anion exchange reaction, resulting in highly dispersed, crystalline ~5 nm cassiterite SnO₂ particles. All Pt/SnO₂ composites displayed mesoporous structures with type IVa isotherms and H₂-type hysteresis, with SP1a (Pt on SnA) exhibiting the largest surface area (122.6 m²/g) and the smallest pores (~3.5 nm). STEM-HAADF imaging revealed well-dispersed PtOx domains (~0.85 nm), while XPS confirmed the dominant Pt⁴⁺ and Pt²⁺ species, with ~25% Pt⁰ likely resulting from photoreduction and/or interactions with Sn–OH surface groups. Raman spectroscopy revealed three new bands (260–360 cm⁻¹) that were clearly visible in the sample with 10 mol% Pt and were due to the vibrational modes of the PtOx species and Pt-Cl bonds introduced due the addition and hydrolysis of H₂PtCl₆ precursor. TGA/DSC analysis revealed the highest mass loss for SP1a (~7.3%), confirming the strong hydration of the PtOx domains. Despite the predominance of oxidized PtOx species, SP1a exhibited the highest catalytic activity (k_app = 1.27 × 10⁻² s⁻¹) and retained 84.5% activity for the reduction of 4-NP to 4-AP after 10 cycles. This chloride-free low-temperature synthesis route offers a promising and generalizable strategy for the preparation of noble metal-based nanocatalysts on oxide supports with high catalytic activity and reusability. Full article

The treatment of contaminants from road infrastructure poses significant challenges due to their variable composition and the high concentrations of chloride ions, heavy metals, and oil-derived substances. Traditional methods for protecting groundwater environments are often insufficient. A promising alternative is permeable reactive barrier (PRB) technology, which utilizes recycled materials and construction waste as reactive components within the treatment zone of the ground. This paper delves into the potential of employing a composite (MIX) consisting of modified construction aggregate (as recycled material) and activated carbon (example of reactive material) to address environmental contamination from a mixture of heavy metals and chloride. The research involved chemical modifications of the road aggregate, activated carbon, and their composite, followed by laboratory tests in glass reactors and non-flow batch tests to evaluate the kinetics and chemical equilibrium of the reactions. The adsorption process was stable and conformed to the pseudo-second-order kinetics and Langmuir, Toth, and Redlich–Peterson isotherm models. Studies using MIX from a heavy metal model solution showed that monolayer adsorption was a key mechanism for removing heavy metals, with strong fits to the Langmuir (R² > 0.80) and Freundlich models, and optimal efficiencies for Cd and Ni (R² > 0.90). The best fit, at Cd, Cu, Ni = 0.96, however, was with the Redlich–Peterson isotherm, indicating a mix of physical and chemical adsorption on heterogeneous surfaces. The Toth model was significant for all analytes, fitting Cl and Cd well and Pb and Zn moderately. The modifications made to the composite significantly enhanced its effectiveness in removing the contaminant mixture. The test results demonstrated an average reduction of chloride by 85%, along with substantial removals of heavy metals: lead (Pb) by 90%, cadmium (Cd) by 86%, nickel (Ni) by 85%, copper (Cu) by 81%, and zinc (Zn) by 79%. Further research should focus on the removal of other contaminants and the optimization of magnesium oxide (MgO) dosage. Full article

The efficient electrochemical reduction of carbon dioxide to formate under mild conditions is a promising approach to mitigate the energy crisis, but requires the use of high-performance catalysts. The selectivity and activity of catalysts can be enhanced through multi-metal doping, further advancing the electrochemical reduction of CO₂ to formate. This study demonstrates a co-electrodeposition strategy for synthesizing SnBi electrocatalysts on pretreated copper foam substrates, systematically evaluating how the Sn²⁺/Bi³⁺ molar ratio in the electrodeposition solution and the applied current density affect the catalytic performance for CO₂-to-formate conversion. Optimal performance was achieved with a molar ratio of Sn²⁺ to Bi³⁺ of 1:0.5 and a deposition current density of 3 mA cm⁻², resulting in a formate Faradaic efficiency (FE_formate) of 97.80% at −1.12 V (vs. RHE) and a formate current density of 26.9 mA·cm⁻². Furthermore, the Sn₁Bi_0.50-3 mA·cm⁻² electrode demonstrated stable operation at the specified potential for 9 h, maintaining a FE_formate above 90%. Compared to previously reported metal catalysts, the SnBi catalytic electrode exhibits superior performance for the electrochemical reduction of CO₂ to HCOOH. The study highlights the significant impact of the metal ion molar ratio and deposition current density in the electrodeposition process on the characteristics and catalytic performance of the electrode. Full article

To ensure the sustainable use of limited resources, it is essential to establish selective and efficient recycling technologies for platinum group metals (PGMs). This study focused on the selective precipitation-based separation of Pt(IV) from hydrochloric acid (HCl) solutions in the presence of various metal ions, using trans-1,4-bis(aminomethyl)cyclohexane (BACT) as a precipitating agent. By using BACT, we succeeded in the selective separation of Pt(IV) by precipitation from HCl solutions containing Pd(II) and Rh(III). Notably, selective and efficient recovery of Pt(IV) was accomplished across various HCl concentrations, with a small amount of BACT and within a short shaking time. To evaluate the practical applicability of the method, Pt(IV) was recovered and purified from the HCl leachate of spent automotive exhaust gas purification catalysts using BACT. As a result, a high Pt recovery of 95.6% and a high purity of 99.3% were achieved. Although Pt(IV) was recovered as a precipitate containing BACT, it was found that Pt black could be readily obtained by dissolving the precipitate in HCl solution followed by reduction with sodium borohydride. Detailed structural analysis of the Pt(IV)-containing precipitate revealed that it is an ionic crystal composed of [PtCl₆]²⁻ and protonated BACT. The selective formation of this ionic crystal in HCl solution, along with its stability under such conditions, is the key to the selective recovery of Pt(IV) using BACT. Full article

Numerous studies have been conducted employing various techniques to remove pollutants from water bodies. Among these techniques, adsorption a surface phenomenon that utilises adsorbents derived from agricultural residues has shown considerable potential for the removal of contaminants such as heavy metals. However, most of these investigations have been carried out at the laboratory scale, with limited efforts directed towards predicting the performance of these systems at an industrial level. Accordingly, the present study aims to model a packed bed column at industrial scale for the removal of Pb(II) and Ni(II) ions from aqueous solutions, employing biomass derived from oil palm residues as the adsorbent material. To achieve this, Aspen Adsorption was used as a modelling and simulation tool to evaluate the impact of bed height, inlet flow rate, and initial concentration through a parametric assessment. This evaluation incorporated the Freundlich, Langmuir, and Langmuir–Freundlich isotherm models in conjunction with the Linear Driving Force (LDF) kinetic model. The results indicated that the optimal operating parameters included a column height of 5 m, a flow rate of 250 m³/day, and an initial metal concentration of 5000 mg/L. Moreover, all models demonstrated removal efficiencies of up to 94.6% for both Pb(II) and Ni(II). An increase in bed height resulted in longer breakthrough and saturation times but led to a reduction in adsorption efficiency. Conversely, higher flow rates shortened these times yet enhanced efficiency. These findings underscore the potential of computational modelling tools as predictive instruments for evaluating the performance of adsorption systems at an industrial scale. Full article

The conventional spent lithium-ion batteries (LIBs) recycling method suffers from complex processes and excessive chemical consumption. Hence, this study proposes an electrochemical strategy for achieving reductant-free leaching of high-valence transition metals and efficient separation of valuable components from spent cathode sheets (CSs). An innovatively designed sandwich-structured electrochemical reactor achieved efficient reductive dissolution of cathode materials (CMs) while maintaining the structural integrity of aluminum (Al) foils in a dilute sulfuric acid system. Optimized current enabled leaching efficiencies exceeding 93% for lithium (Li), cobalt (Co), manganese (Mn), and nickel (Ni), with 88% metallic Al foil recovery via cathodic protection. Multi-scale characterization systematically elucidated metal valence evolution and interfacial reaction mechanisms, validating the technology’s tripartite innovation: simultaneous high metal extraction efficiency, high value-added Al foil recovery, and organic removal through single-step electrochemical treatment. The process synergized the dissolution of CM particles and hydrogen bubble-induced physical liberation to achieve clean separation of polyvinylidene difluoride (PVDF) and carbon black (CB) layers from Al foil substrates. This method eliminates crushing pretreatment, high-temperature reduction, and any other reductant consumption, establishing an environmentally friendly and efficient method of comprehensive recycling of battery materials. Full article

Metal–organic frameworks (MOFs) are a novel type of porous crystalline materials assembled from metal ions and organic linkers. Their derivatives can inherit characteristics such as high specific surface area, tunable porosity, and unique topological structures, which make MOF-derived metal oxides ideal catalysts for the selective catalytic reduction (SCR) of NO_x. This review focuses on the synthetic strategies of MOF-derived metal oxides and the latest progress of oxides derived from various typical MOFs materials (including MILs, ZIFs, UiO, BTC series, MOF-74, MOF-5, and Prussian blue analogs, etc.) in the catalytic reduction in NO_x, and analyzes the mechanisms for the enhanced catalytic performance. In addition, the challenges and prospects of MOF derivatives in catalytic applications are discussed. It is hoped that this review will help researchers understand the latest research progress of MOF-derived metal oxide materials in the catalytic removal of NO_x pollution. Full article

Pyrometallurgical recycling of lithium-ion batteries presents distinct advantages including streamlined processing, simplified pretreatment requirements, and high throughput capacity. However, its industrial implementation faces challenges associated with high energy demands and lithium loss into slag phases. This investigation develops an integrated reduction smelting–chloridizing volatilization process for the comprehensive recovery of strategic metals (Li, Mn, Cu, Co, Ni) from spent ternary lithium-ion batteries; calcium chloride was selected as the chlorinating agent for this purpose. Thermodynamic analysis was performed to understand the phase evolution during reduction smelting and to design an appropriate slag composition. Preliminary experiments compared carbon and aluminum powder as reducing agents to identify optimal operational parameters: a smelting temperature of 1450 °C, 2.5 times theoretical CaCl₂ dosage, and duration of 120 min. The process achieved effective element partitioning with lithium and manganese volatilizing as chloride species, while transition metals (Cu, Ni, Co) were concentrated into an alloy phase. Process validation in an induction furnace with N₂-O₂ top blowing demonstrated enhanced recovery efficiency through optimized oxygen supplementation (four times the theoretical oxygen requirement). The recovery rates of Li, Mn, Cu, Co, and Ni reached 94.1%, 93.5%, 97.6%, 94.4%, and 96.4%, respectively. This synergistic approach establishes an energy-efficient pathway for simultaneous multi-metal recovery, demonstrating industrial viability for large-scale lithium-ion battery recycling through minimized processing steps and maximized resource utilization. Full article

Electroless silver (Ag) plating has emerged as a simple yet effective surface modification technique, garnering significant attention in consumer electronics and composite materials. This study systematically investigates the influence of glucose dosage on the microstructural refinement of Ag coatings deposited from silver–ammonia solutions onto iron (Fe) particles while also evaluating the oxidation resistance of Ag-plated particles through thermogravimetric analysis. Optimal results were achieved at a silver nitrate concentration of 0.02 mol/L and a glucose concentration of 0.05 mol/L, producing Fe particles with a uniform and dense silver coating featuring an average Ag grain size of 76 nm. The moderate excess glucose played a dual role: facilitating Ag⁺ ion reduction while simultaneously inhibiting the growth of Ag atomic clusters, thereby ensuring microstructural refinement of the silver layer. Notably, the Ag-plated particles demonstrated superior oxidation resistance compared to their uncoated counterparts. These findings highlight the significance of fine-grained electroless Ag plating in developing high-temperature conductive metal particles and optimizing interfacial structures in composite materials. Full article

Background: Dithiolopyrrolones (DTPs), such as holomycin and thiolutin, exhibit potent antibacterial activities. DTPs contain a disulfide within a unique bicyclic scaffold, which may chelate metal ions and disrupt metal-dependent cellular processes once the disulfide is reductively transformed to thiols. However, the contribution of the intrinsic redox mechanism of DTPs to their antibacterial activity remains unclear. Herein we used pyrroloformamide (Pyf) A, a DTP with a unique formyl substituent, as a prototype to study the antibacterial potential and mechanism against ESKAPE pathogens, in particular carbapenem-resistant Klebsiella pneumoniae (CRKP). Methods: The antibacterial and anti-biofilm activities of Pyf A were mainly assessed against clinical CRKP isolates. Propidium iodide staining, scanning electron microscopy, glutathione (GSH) quantification, and reactive oxygen species (ROS) analysis were utilized to infer its anti-CRKP mechanism. The synergistic antibacterial effects of Pyf A and AgNO₃ were evaluated through checkerboard and time-kill assays, as well as in vivo murine wound and catheter biofilm infection models. Results: Pyf A exhibited broad-spectrum antibacterial activity against ESKAPE pathogens with minimum inhibitory concentrations ranging from 0.25 to 4 μg/mL. It also showed potent anti-biofilm effects against CRKP. Pyf A disrupted the cell membranes of CRKP and markedly depleted intracellular GSH without triggering ROS accumulation. Pyf A and AgNO₃ showed synergistic anti-CRKP activities in vitro and in vivo, by disrupting both GSH- and thioredoxin-mediated redox homeostasis. Conclusions: Pyf A acts as a GSH-depleting agent and, when combined with AgNO₃, achieves dual-targeted disruption of bacterial thiol redox systems. This dual-targeting strategy enhances antibacterial efficacy of Pyf A and represents a promising therapeutic approach to combat CRKP infections. Full article

The selective catalytic reduction of NO_x with CH₄ (CH₄-SCR) holds the potential to simultaneously abate harmful NO_x and CH₄ greenhouse gases. In this study, a series of bimetallic M-In/H-SSZ-39 catalysts (where M represents Cr, Co, Ce, and Fe) were prepared via an ion exchange method and subsequently evaluated for their CH₄-SCR activity. The influences of the preparation parameters, including the metal ion concentration and calcination temperature, as well as the operating conditions, such as the CH₄/NO ratio, O₂ concentration, water vapor content, and gas hourly space velocity (GHSV), on the catalytic activity of the optimal Cr-In/H-SSZ-39 catalyst were meticulously examined. The results revealed that the Cr-In/H-SSZ-39 catalyst exhibited peak CH₄-SCR catalytic performance when the Cr(NO₃)₃ concentration was 0.0075 M, the In(NO₃)₃ concentration was 0.066 M, and the calcination temperature was 500 °C. Under optimal operating conditions, namely GHSV of 10,000 h⁻¹, 400 ppm NO, 800 ppm CH₄, 15 vol% O₂, and 6 vol% H₂O, the NO_x conversion rate reached 93.4%. To shed light on the excellent performance of Cr-In/H-SSZ-39 under humid conditions, a comparative analysis of the crystalline phase, chemical composition, pore structure, surface chemical state, surface acidity, and redox properties of Cr-In/H-SSZ-39 and In/H-SSZ-39 was conducted. The characterization results indicated that the incorporation of Cr into In/H-SSZ-39 enhanced its acidity and also facilitated the generation of InO⁺ active species, which promoted the oxidation of NO and the activation of CH₄, respectively. A synergistic effect was observed between Cr and In species, which significantly improved the redox properties of the catalyst. Consequently, the activated CH₄ could further interact with InO⁺ to produce carbon-containing intermediates such as HCOO⁻, which ultimately reacted with nitrate-based intermediates to yield N₂, CO₂, and H₂O. Full article

The imidazo[4,5-b]pyridine scaffold, a versatile heterocyclic system, is renowned for its biological and chemical significance, yet its coordination chemistry with biologically relevant metal dications remains underexplored. This study investigates the proton and metal dication affinities of twelve tetracyclic organic molecules based on the imidazo[4,5-b]pyridine core, focusing on their interactions with Ca(II), Mg(II), Zn(II), and Cu(II). Employing a dual approach of electrospray ionization mass spectrometry (ESI-MS) and density functional theory (DFT) calculations, we characterized the formation, stability, and structural features of metal–ligand complexes. ESI-MS revealed distinct binding behaviors, with Cu(II) and Zn(II) forming stable mono- and dinuclear complexes, often accompanied by reduction processes (e.g., Cu(II) to Cu(I)), while Ca(II) and Mg(II) exhibited lower affinities. DFT analysis elucidated the electronic structures and thermodynamic stabilities, highlighting the imidazole nitrogen as the primary binding site and the influence of regioisomeric variations on affinity. Substituent effects were found to modulate binding strength, with electron-donating groups enhancing basicity and metal coordination. These findings provide a comprehensive understanding of the coordination chemistry of imidazo[4,5-b]pyridine derivatives, offering insights into their potential applications in metalloenzyme modulation, metal-ion sensing, and therapeutic chelation. Full article