Search Results (201)

The sustainable recovery of valuable metals such as Cu and Co from ores is a pressing need considering environmental and economic challenges. Therefore, this study evaluates the effectiveness of deep eutectic solvents (DESs) as alternative leaching agents for Cu and Co extraction. Four DESs were prepared using choline chloride (ChCl) as a hydrogen bond acceptor (HBA) and oxalic acid (OA), ethylene glycol (EG), urea (U) and thiourea (TU) as hydrogen bond donors (HBDs). Leaching experiments were conducted with DESs supplemented with 30 wt.% water at varying temperatures, various solid-to-liquid ratios, and time durations. The ChCl:OA DES demonstrated the highest leaching efficiencies among the DESs tested on pure CuO and CoO, achieving 89.2% for Cu and 92.4% for Co (60 °C, 400 rpm, 6 h, −75 + 53 µm particle size, and 1:10 solid-to-liquid ratio). In addition, the dissolution kinetics, analysed using the shrinking core model (SCM), showed that the leaching process was mainly controlled by surface chemical reactions. The activation energy values for Cu and Co leaching were 46.8 kJ mol⁻¹ and 51.4 kJ mol⁻¹, respectively, supporting a surface chemical control mechanism. The results highlight the potential of ChCl:OA as a sustainable alternative for metal recovery. Full article

Zirconium-89 (⁸⁹Zr) is a widely used radionuclide in immune-PET imaging due to its physical decay characteristics. Despite its importance, the production of ⁸⁹Zr radiopharmaceuticals remains largely manual, with limited cost-effective automation solutions available. To address this, we developed an automated system for the agile and reliable production of radiopharmaceuticals. The system performs transmutations, dissolution, and separation for a range of radioisotopes. Steps in the production of ⁸⁹Zr-oxalate are used as an exemplar to illustrate its use. Three-dimensional (3D) printing was exploited to design and manufacture a target holder able to include solid targets, in this case an ⁸⁹Y foil. Spot welding was used to attach ⁸⁹Y to a refractory tantalum (Ta) substrate. A commercially available CPU chiller was repurposed to efficiently cool the metal target. Furthermore, a commercial resin (ZR Resin) and compact peristaltic pumps were employed in a compact (10 × 10 × 10 cm³) chemical separation unit that operates automatically via computer-controlled software. Additionally, a standalone 3D-printed unit was designed with three automated functionalities: photolabelling, vortex mixing, and controlled heating. All components of the assembly, except for the target holder, are housed inside a commercially available hot cell, ensuring safe and efficient operation in a controlled environment. This paper details the design, construction, and modelling of the entire assembly, emphasising its innovative integration and operational efficiency for widespread radiopharmaceutical automation. Full article

This study focuses on the design and optimization of a monopolar electrode configuration for the hybrid electrochemical treatment of real washing machine wastewater. A combined electrocoagulation (EC) and electro-oxidation (EO) system was optimized to maximize pollutant removal efficiency while minimizing energy consumption. The monopolar setup employed mixed metal oxide (MMO) and aluminum anodes, along with a stainless steel cathode, operating under controlled conditions with sodium chloride as the supporting electrolyte. An applied current density of 15 mA cm⁻² achieved 90% chemical oxygen demand (COD) removal, 98% surfactant degradation, complete turbidity reduction within 120 min, and pH stabilization near 8. Additionally, electrochemical disinfection achieved <2 MPN/100 mL, with no detectable phenols and the presence of organic anions such as oxalate and acetate. These results demonstrate the effectiveness of an optimized monopolar EC–EO system as a cost-efficient and sustainable strategy for wastewater treatment and potential water reuse. Further studies should focus on refining energy consumption and monitoring reaction by-products to enhance large-scale applicability. Full article

A catalyst with the active component Cu loaded onto the carrier activated carbon was prepared, and metal Ca was introduced into the catalyst to modify it. This catalyst was used in the hydrogenation reaction of dimethyl oxalate, and the reaction kinetics was studied. The kinetic experiments were carried out in a fixed bed reactor with a reaction temperature varying from 483 K to 513 K, reaction pressure varying from 1.5 Mpa to 2.5 Mpa, and the weight hourly space velocity of dimethyl oxalate varying from 0.435 h⁻¹ to 0.726 h⁻¹. Eight possible dynamic models were proposed, the optimal model was selected, and the parameters of the optimal model were calculated using MATLAB. The results showed that dimethyl oxalate adsorbed on the active site by dissociation adsorption, and the dissociation adsorption of ester was the rate-controlling step. The parameters of the model were consistent with thermodynamics and statistical analysis, further proving that the model has good forecasting performance. Full article

In recent years, extensive attention has been paid to advanced oxidation processes (AOPs) with peracetic acid (PAA), a widely used disinfectant, using transition metal ions for the degradation of organic contaminants within water environments. Mn(II) has been widely used as an effective homogeneous transition metal catalyst for oxidant activation, but it has shown poor performances with PAA. Since the stability of manganese species can be enhanced through the addition of ligands, this study systematically investigated a novel AOP for the oxidation of carbamazepine (CBZ) using an Mn(II)/PAA system with several different ligands added. The reactive species were explored through UV-vis spectrometry, scavengers, and probe compounds. The results suggest that Mn(III)–ligand complexes and other high-valent Mn species (Mn(V)) were generated and contributed obviously toward efficient CBZ oxidation, while radicals like CH₃CO₂^• and CH₃CO₃^• were minor contributors. The oxidation efficiency of Mn(II)/PAA/ligands depended highly on ligand species, as ethylene diamine tetraacetic acid (EDTA) and oxalate (SO) could promote the oxidation of CBZ, while pyrophosphate (PPP) showed modest enhancement. The results obtained here might contribute to the removal of residue pharmaceuticals under manganese-rich waters and also shed light on PAA-based AOPs that could help broaden our present knowledge of manganese chemistry for decontamination in water treatment. Full article

Background/Objectives: Urolithiasis is a common disease in Western societies, affecting approximately 10% of the population, and more often men than women. The formation of renal calculi is a complex process, including various compounds and proteins. The aim of this study is to compare differences between the trace element concentrations in male and female renal calculi as well as differences between the trace element concentrations in different stone types. Material and Methods: Renal calculi specimens were obtained during elective nephrolithotripsy procedures. Crystallography of renal calculi was performed using X-ray diffraction; an elemental analysis was performed using Inductively Coupled Plasma–Optical Emission Spectrometry. Statistical analysis was performed to assess the differences in the metal element concentration between men and women. The second part of the analysis measured the differences in the metal element concentration between stones containing calcium phosphate (CaP) and pure calcium oxalate (CaOx) stones. Results: The renal calculi (n = 20) obtained from the male patients had a lower potassium concentration than the calculi (n = 24) from the female patients: 393.4 vs. 792.3 mg/kg, p = 0.007. A comparison of the CaP calculi and CaOx calculi showed a higher zinc concentration (p < 0.001) and potassium concentration (p < 0.001) in the stones containing calcium phosphate. Conclusions: The renal calculi from females had a significantly higher potassium content than those from males. This difference was not correlated with hyperkalemia or the blood potassium levels, suggesting a sex-dependent role of uromodulin in stone formation. The stones containing calcium phosphate exhibited higher zinc and potassium concentrations compared to the pure calcium oxalate stones. The increased presence of zinc and potassium in urine may accelerate the formation of calcium phosphate calculi. Full article

The detection of zinc ions plays an essential role in protecting public health and maintaining ecological balance. However, traditional fluorescent probes for Zn²⁺ are limited in their specificity, especially under complex environments, due to their single-mode optical signal and inadequate recognization capacities. Herein we report a dual-mode supramolecular sensing system constructed from a unique three-component assembly involving a terpyridine platinum (II) complex, oxalate, and Zn²⁺, enabling highly specific detection performance for Zn²⁺. The supramolecular sensing system exhibits excellent selectivity among various interfering substances, accompanied by ultra-low detection limit (0.199 μM) and fast response (<3 s). The high recognization capacity comes from tri-component-based supramolecular assembly, while the dual-mode response arises from the generation of intermelcular Pt-Pt and π-π interactions, which yields absorption and emission originating from low-energy metal–metal-to-ligand charge transfer (MMLCT) transitions. This work marks a pioneering demonstration for highly specific detection of Zn²⁺ and inspires an alternative strategy for designing cation probes. Full article

To address the challenges of environmental adaptability and passivation in nanoscale zero-valent iron (nFe⁰) systems, we developed oxalate-modified nFe⁰ (nFe_oxa) through a coordination-driven synthesis strategy, aiming to achieve high-efficiency Cr(VI) removal with improved stability and reusability. Structural characterization (STEM and FT-IR) confirmed the formation of a FeC₂O₄/nFe⁰ heterostructure, where oxalate coordinated with Fe(II) to construct a semiconductor interface that effectively inhibits anoxic passivation while enabling continuous electron supply, achieving 100% Cr(VI) removal efficiency within 20 min at an optimal oxalate/Fe molar ratio of 1/29. Mechanistic studies revealed that the oxalate ligand accelerates electron transfer from the Fe⁰ core to the surface via the FeC₂O₄-mediated pathway, as evidenced by EIS and LSV test analyses. This process dynamically regenerates surface Fe(II) active sites rather than relying on static-free Fe(II) adsorption. XPS and STEM further demonstrated that Cr(VI) was reduced to Cr(III) and uniformly co-precipitated with Fe(II/III)-oxalate complexes, effectively immobilizing chromium. The synergy between the protective semiconductor layer and the ligand-enhanced electron transfer endows nFe_oxa with superior reactivity. This work provides a ligand-engineering strategy to design robust nFe⁰-based materials for sustainable remediation of metal oxyanion-contaminated water. Full article

This study explored the selective recovery of Co, La, and Sr from end-of-life solid oxide cells (SOCs) using ultrasound-assisted leaching in HCl. HCl concentration (1, 5, and 10 M) and solid-to-liquid ratio (S/L, 100 and 200 g/L) were varied to optimize the efficiency and the selectivity of Co, La, and Sr leaching. Then, they were recovered as oxalates at pH 0.7, 1, and 4. Using 10 M HCl and an S/L ratio of 100 g/L on ball-milled samples achieved 96–99% leaching efficiency but led to Ni impurities from the underneath layers. Thermal pre-treatment at 800 °C decreased Ni leaching by 90% but decreased target metals’ recovery by 9%. Direct leaching (without pre-treatments) with 1 M HCl and an S/L ratio of 200 g/L achieved up to 91% leaching efficiency, recovering 42% of Co, 93% of La, and 33% of Sr with minimal Ni impurities. A preliminary economic analysis indicated that avoiding pre-treatments can cut expenses by 96%. An economic analysis indicated that direct leaching is the most cost effective, reducing expenses by up to 96% compared to thermal pre-treatment and high HCl concentrations. This study highlights the potential for an efficient and cost-effective method for recycling Co, La, and Sr from EoL SOCs. Full article

Structural rearrangements in metal–organic supramolecules constructed from the coordination of Cu(II) with m-xpt (m-xylylenebis(pyridyltriazole)) are investigated upon their interaction with 1,4-diazabicyclo[2.2.2]octane (dabco) and carbon dioxide-enriched air. The binuclear [Cu₂(m-xpt)₂]⁴⁺ complexes react with dabco to produce a carbonate-bridged trinuclear complex, [Cu₃(m-xpt)₃(µ-CO₃)]⁴⁺, and an oxalate-bridged binuclear complex, [Cu₂(m-xpt)₂(µ-C₂O₄)]²⁺, where carbonate and oxalate likely originate from CO₂ and dabco, respectively. The trinuclear complex reassembles the original dimer upon the removal of the carbonate ion. Similarly, polymeric [Cu(o-xpt)(PF₆)]_n, formed from Cu(I) and o-xpt (o-xylylenebis(pyridyltriazole)) coordination, undergoes oxidation in CO₂-enriched air to yield a tetranuclear Cu(II) complex, Cu₄(o-xpt)₃(μ₄-CO₃)(μ₂-OH)(μ₂-OCOCH₃)⁴⁺. The reaction progress is monitored by UV-Vis spectroscopy, and the major products are characterized by single-crystal X-ray diffraction. Full article

The present study aims to create porous materials through the acid activation of bentonites using 0.5 M oxalic acid at different pH values. Two types of bentonites (containing aluminum montmorillonite and ferruginous montmorillonite) were treated with oxalate solutions at pH 1 to 5. During acid activation at the three pH values, Al, Fe, Mg and Si kinetics were monitored; the porosity of the samples was modified; and the specific surface area increased, while the crystal structure did not completely collapse. The optimum conditions occurred at pH 1, where the highest metal leaching was obtained for both samples. For the sample with aluminum smectite, the specific surface increased from 28.1 m²/g to 149 m²/g and the pore volume quadrupled. In the case of samples with ferruginous smectite, the specific surface area rose from 63. 2 m²/g to 372 m²/g and the pore volume increased sixfold. The mechanism of smectite activation was investigated, revealing that at the optimum experimental conditions, which is ferruginous bentonite activation at pH 1, the products have the highest concentration of small 30 to 50 Å pores, which is attributed to the creation of an adequate number of active sites and the formation of aluminum complexes with the oxalate anions. The modified bentonites have elevated porosity; therefore, they could be used as adsorbents in industry. Full article

In this study, a millimeter-scale N/P-doped carbonaceous catalyst was synthesized via facile carbonization of the N/P-doped resin at 800 °C (NPCR-800). This work aimed to investigate the performance of the NPCR-800 catalyst in heterogeneous catalytic ozonation and the mechanism of reactive oxygen species (ROS) generation. The NPCR-800 achieved the highest oxalic acid (OA) degradation efficiency of 91% within 40 min. The first-order kinetics of OA degradation in the NPCR-800/O₃ system was approximately twelve and three times higher than that in the O₃ and O₃/GAC system, respectively. In addition to excellent catalytic ozonation performance, the NPCR catalyst also exhibited good reusability and salt tolerance. The dominant ROS were identified by the electronic spin response and free radical quantitative experiments, being responsible for oxalic acid degradation in NPCR-800/O₃ system. The effect of the doped N and P elements on enhancing the catalytic activity was understood, what was ascribed to the efficient reaction of the O₃ molecule with the active site of the graphitic N, defect site and carbonyl/carboxyl groups of NPCR to generate the hydroxyl radical and singlet oxygen. A type of metal-free catalytic ozonation strategy was developed in this work, which is promising in the practical treatment of the refractory organic pollutants. Full article

Three complexes of Cd(II), [Cd(NA)₂(NO₃)₂(H₂O)₂] (1), [Cd(NA)₂(NO₃)₂(H₂O)₂]·2NA (2), and [Cd(ox)(NA)(H₂O)]·H₂O (3) (NA = nicotinamide, ox = oxalate) were synthesized and characterized. Complexes (1) and (2) are mononuclear, while complex (3) is a bidimensional polymeric coordination compound, with oxalate anions bridging metal ions in two different ways: µ₂ bis-bidentate chelating manner and µ₄ bis-bidentate bis-monodentate manner. The stereochemistry of Cd(II) in compounds (1) and (3) is a distorted pentagonal bipyramid, while in compound (2) it is a regular octahedron. Complexes (1) and (2) demonstrated significant activity against Enterococcus faecalis and Escherichia coli, showcasing their potential as effective antibacterial agents and inhibitors of microbial adhesion. The complexes were characterized by means of single-crystal X-ray diffraction, elemental analysis, FTIR (all complexes), ¹H NMR, ¹³C NMR, fluorescence spectroscopy, and antimicrobial activity (complexes (1) and (2)). Full article

Soil fungi are significantly resistant to heavy metals, which allows them to be used in biotechnologies for environmental bioremediation. In order to clarify the prospects for using the fungi in Zn-detoxifying technologies, we investigated in vitro the effect of fungal metabolism on Zn minerals formation. The cultivation of fungi with different acid-producing activities (Aspergillus niger and Penicillium chrysogenum) was carried out in a liquid Czapek–Dox nutrient medium with Zn concentrations from 250 to 2000 µmol within 28 days. The quantitates of low-molecular-weight organic acids, phosphates, and hydrophosphates ions in the medium were determined through chromatography–mass spectrometry; analysis of biomineralization products was carried out through powder X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. It was found that Zn in concentrations 250–500 μmol acts as a physiologically essential element, activating the growth of fungal mycelium, while at high concentrations (1000–2000 μmol), Zn acts as a toxic heavy metal, inhibiting fungal growth. Zn also activates the formation of oxalic acid by both species of fungi. But A. niger strongly acidified the medium, while P. chrysogenum leaves the medium pH close to neutral or slightly alkaline. Oxalate and phosphate crystallization occur with the participation of both fungal species. The ratio of biogenic oxalates and phosphates is directly dependent on the acid-reducing capacity of fungi. The solid solutions of katsarosite–glushinskite of the isodimorphic series with the general formula (Zn,Mg)C₂O₄·2H₂O (Mg ions comes from Czapek–Dox medium) were detected at all Zn concentrations in a wide range of pH (from 2 to 9.0). The transition from monoclinic (α-modifications) to orthorhombic (β-modifications) occurs at the ratio Mg/Zn > 1. Fungal zinc phosphate hopeite Zn₃(PO₄)₂·4H₂O was formed at a near-neutral pH at high Zn concentrations (1000 and 2000 µmol/L). In the Zn example, it was shown that not only oxalate but also phosphate fungal biomineralization can be used for the environment detoxification of heavy metals. The application of phosphate biomineralization seems promising in the case of severe pollutions. To create a near-neutral medium favorable for the formation of phosphates, it is advisable to use soil fungi non-producing or weakly producing organic acids (for example, P. chrysogenum). Full article

Mine tailings are a byproduct of mineral extraction and often pose an environmental challenge due to the contamination of soil and water bodies with dissolved metals. However, this type of waste offers the opportunity for the recovery of valuable metals such as silver (Ag). In the present investigation, an integral analysis of a sample of tailings was carried out, addressing granulometry, elemental composition, neutralization potential (NP), and acid potential (AP), as well as mineralogy, for the dissolution of silver from this type of waste. For this purpose, thiourea (CH₄N₂S) was used as a leaching agent due to its low toxicity, and potassium oxalate (K₂C₂O₄) was used as an organic additive to improve the leaching of the silver phases (argentite and polybasite) present in the tailings. The effects of CH₄N₂S and K₂C₂O₄ concentrations, temperature, and pH on the leaching efficiency of silver (Ag), copper (Cu), iron (Fe), and arsenic (As) were systematically studied. The results revealed that the maximum silver dissolution rate reached 90.75% under optimal conditions: 0.2 M L⁻¹ of thiourea and 0.2 M L⁻¹ of potassium oxalate, at 35 °C and a pH of 2. Full article