Search Results (154)

Selective Ni(II) recovery from polymetallic sulfate leachates is challenging because of competition from accompanying metal ions, particularly Mg(II). This study systematically evaluated selective Ni(II) recovery using commercial chelating ion-exchange resins and assessed their adsorption performance and regeneration behavior in the context of their integration into a conceptual flowsheet for oxidized nickel ore processing. The ore was characterized by XRF, XRD, and SEM–EDS, while Seplite LSC 495 (bispicolylamine) and Seplite LSC 773 (iminodiacetate) were evaluated using selectivity tests, kinetic and equilibrium studies, FTIR spectroscopy, and adsorption–desorption experiments. Both resins exhibited high selectivity for Ni(II) over Co(II) and Mg(II). Under the optimized conditions, Seplite LSC 773 achieved 99.36 ± 0.08% Ni(II) recovery from the model solution and 98.59 ± 0.36% from the actual leach solution, whereas Seplite LSC 495 achieved 94.62 ± 0.21% and 94.23 ± 0.21%, respectively. The equilibrium data exhibited a Giles S-type profile without reaching a distinct saturation plateau within the investigated concentration range, and the Freundlich model provided the most appropriate description of the data, consistent with adsorption on energetically heterogeneous binding sites. FTIR spectral changes indicated the involvement of the chelating functional groups in Ni(II) binding. Among the regeneration conditions investigated, 20 wt.% H₂SO₄ provided the highest Ni(II) desorption efficiency; however, desorption remained limited to approximately 42%, indicating that regeneration remains a major constraint on practical application. The experimental findings were incorporated into a conceptual flowsheet integrating sulfuric acid leaching, selective Ni recovery, subsequent Co separation, and MgSO₄·7H₂O production. Further work should focus on optimizing regeneration, extending cyclic testing, evaluating continuous-flow operation, and validating the integrated process at the pilot scale. Full article

Moxifloxacin-based Schiff-base ligands provide a useful platform for tuning the coordination and biological properties of fluoroquinolone derivatives. Here, a moxifloxacin–salicylaldehyde hydrazone ligand (MOX-S) was prepared and coordinated with cobalt(II), nickel(II), copper(II), oxovanadium(IV), and gadolinium(III) ions to obtain a series of metal complexes. Citrate-stabilized gold nanoparticles (AuNPs) were also prepared and functionalized with MOX-S and the Cu(II) complex to evaluate the effect of nanoformulation on biological performance. The compounds were characterized using complementary analytical, spectroscopic, magnetic, thermal, and microscopic techniques. The combined data support 1:2 metal-to-ligand formulations for the complexes and indicate coordination mainly through the azomethine nitrogen and oxygen donor sites of MOX-S. In antimicrobial screening, the activity was strongly metal- and organism-dependent. Cu–MOX-S and VO–MOX-S showed the most pronounced activity against Gram-positive bacteria, with inhibition zones of up to 30 mm, while Cu–MOX-S displayed MIC values of 19.53 and 39.06 µg mL⁻¹ against Bacillus subtilis and Staphylococcus aureus, respectively. Cytotoxicity assays showed that MOX-S was more active than moxifloxacin against MCF-7 and HepG2 cells, while Cu–MOX-S showed enhanced potency, particularly toward HepG2 cells, with an IC₅₀ of 0.98 µM and a selectivity index of 5.97. AuNP formulations further increased the apparent antiproliferative potency in the tested cancer cell lines, giving sub-micromolar IC₅₀ values. Computational analyses, including DFT-based electronic descriptors and molecular docking, provided qualitative support for the experimentally observed coordination and cytotoxicity trends. Overall, metal coordination and AuNP formulations provide complementary strategies for modulating the physicochemical and in vitro biological behavior of this moxifloxacin-derived hydrazone scaffold. Full article

Ion-imprinting technology based on biosorbents via sorption demonstrates potential for the selective removal of metal ions from water and wastewater. This offers both high sorption capacity and selectivity for specific metals. Current research trends are toward the development of sorbents with minimal environmental impact. Among the most rapidly evolving classes of sorbents are those derived from biopolymers, such as chitosan—a natural derivative of chitin that can be readily functionalized. Due to the growing interest in this topic, it is necessary to summarize the current knowledge. In this article, we provide a comprehensive overview of the latest advances in ion-imprinted chitosan-based materials designed for the purification of metal-contaminated aqueous systems. We conduct a bibliographic analysis and describe a variety of chitosan-based materials exhibiting selectivity toward heavy metals, including chromium Cr(III/VI), cobalt Co(II), nickel Ni(II), copper Cu(II), zinc Zn(II), arsenic As(III/V), cadmium Cd(II), mercury Hg(II), and lead Pb(II). Finally, we discuss future prospects and highlight current research gaps, aiming to guide further scientific exploration and innovation in this promising field. Full article

Hybrid material-derived adsorbents have demonstrated exceptional efficacy in a variety of fields, including environmental cleanup and manufacturing operations. In this study, zinc oxide nanoparticles modified with carbon (ZnO-C) as hybrid adsorbent materials were synthesized using both expired zinc chloride and corncob extract. Hybrid ZnO-C adsorbents were employed for the removal of heavy metals, Co(II), and Ni(II) ions, from wastewater via adsorption. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and energy dispersive spectroscopy (EDS) were among the methods used to fully characterize the structural and morphological properties. To maximize the adsorption process for every metal ion, kinetic and equilibrium studies were carried out. Results revealed that the ZnO-C material formed crystalline, spherical granules with nanoparticle sizes ranging from 25 nm, embedded within a carbon matrix. Additionally, these spherical zinc oxide particles tended to aggregate into clusters. FTIR analysis indicated that the surface of ZnO-C was rich in hydroxyl (OH) groups and zinc oxide, which play a crucial role in the adsorption mechanism. The capacity of ZnO/CC-NPs to adsorb cobalt and nickel ions from aqueous solutions was investigated, examining the influences of initial ion concentration, pH levels, contact duration, and temperature. The findings highlight the high efficiency of ZnO/CC-NPs as an adsorbent, promoting the reuse of waste materials and supporting environmental sustainability efforts. Full article

In the present study, the electrodeposition of thin Ni–Fe films obtained from aqueous electrolytes containing nickel (II) and iron (II) sulfates and chlorides is investigated. The study particularly emphasizes the influence of electrolyte additives—boric acid, chloride ions, and Na₂EDTA—on the electrochemical behavior, microstructure, and magnetic properties of the deposited layers. Cyclic voltammetry revealed a partial alignment of the reduction potentials of nickel and iron and the suppression of the hydrogen evolution side reaction up to −1 V. Electrodeposition in galvanostatic mode in the range of 0.5 to 1.0 A/dm² allows the formation of layers with iron contents between 20.5 wt. % to 41.4 wt. % and coating thickness from 1.3 to 3.0 µm. SEM and AFM observations demonstrated a pronounced dependence of the surface morphology on the current density, with higher current densities promoting the formation of dendritic structures. X-ray diffraction confirmed the dominance of a face-centered cubic (FCC) Ni-based solid solution, accompanied by minor contributions from non-stoichiometric Fe_1−xO. All the obtained Fe-Ni films have soft magnetic properties. Increasing the current density and the boric acid concentration causes the coercive force and isotropy of the layers to improve. The results demonstrate that thin Ni-Fe films with controlled structure and morphology, with favorable soft ferromagnetic properties suitable for functional applications, could be electrodeposited from complex chloride–sulfate electrolytes by adjusting the current density. Full article

Using plants to restore soils subjected to salinization and polychemic pollution can be an effective way to return agricultural land to circulation and obtain safe products. In this study, experiments were conducted with oats and lupine to evaluate their ability to purify soils contaminated with copper (II) and nickel (II) ions, carbonate and sulfate anions and oil and their combinations. The biological activity of the soil, phytotoxicity, and hydrocarbon content, as well as plant growth and biochemical parameters in polluted soil, were studied. The enzymes most sensitive to soil contamination were catalase, urease, and phosphatase. Copper ions inhibited oat root growth by 45.7% and lupine by 46.6%. Oil and its mixtures with other pollutants inhibited shoot growth by up to 50.3% in oats and up to 28.6% in lupine. The content of malonic dialdehyde increased in oats when exposed to copper, while in lupines, it increased 2.9-fold when exposed to oil. Flavonoids in oats increased with metal contamination (by 9–16.7%), while in lupines with oil (by 8.6%). Chlorophyll fluctuations were less pronounced in oats than in lupine. Despite the stress experienced by plants due to soil pollution, the degradation rate of petroleum hydrocarbons under oat and lupine crops was 33–46%. In general, oats and lupine are promising for the phytoremediation of complexly polluted and saline soils. Full article

The electrochemical stability of redox-active polymers based on Ni(II)–Salen complexes is of critical importance for their application as electrode materials for supercapacitors and lithium-ion batteries. This study presents a systematic analysis of the influence of fluoride, chloride, and bromide anions on the redox behavior of two polymeric films: poly[Ni(Salen)] and sterically protected poly[Ni(Saltmen)]. Using cyclic voltammetry (CV), electrochemical quartz crystal microbalance (EQCM), and X-ray photoelectron spectroscopy (XPS), we identify two distinct degradation mechanisms: (1) axial coordination of halide ions to the Ni(II) center followed by demetallation, which disrupts the conjugated system and reduces conductivity, and (2) oxidative halogenation of the ligand. In the presence of chloride ions, both poly[Ni(Salen)] and poly[Ni(Saltmen)] lose approximately 70% of their initial capacity over 50 cycles, indicating progressive electrochemical degradation. In contrast, both polymers demonstrate high electrochemical stability in bromide-containing electrolytes, retaining most of their capacity under identical conditions. Fluoride coordinates without compromising redox performance, serving as a model for electrochemically inert ligands. The results highlight the critical role of both electrolyte composition and ligand design in ensuring the long-term stability of nickel–Salen polymers in energy storage devices. Full article

Polymer films of nickel Schiff-base complexes were investigated to clarify degradation mechanisms induced by coordinating impurities—specifically, the protic solvents methanol and isopropanol. Films of poly[Ni(Salen)] and its sterically protected derivatives were electropolymerized in situ and subjected to cyclic voltammetry (CV) and electrochemical quartz crystal microbalance (EQCM) measurements in dry acetonitrile electrolyte with 1% vol. alcohol added. In situ monitoring of redox activity and mass changes revealed something. It was revealed that traces of alcohols act as axial ligands to the Ni center. This disrupts the conjugated π-system and conductivity of the polymer. The rate of electrochemical stability strongly depends on the complex structure. The unsubstituted poly[Ni(Salen)] film showed the fastest loss of capacity in both methanol and isopropanol, whereas complexes with methyl substituents in the diimine bridge (poly[Ni(Salpn-1,2)] and poly[Ni(Saltmen)]) exhibited significantly improved stability. EQCM measurements revealed irreversible changes in the mass of all polymer films upon exposure to alcohol-containing electrolytes. These observations are consistent with the axial coordination of alcohol molecules to the Ni centers and the concomitant ingress of solvent species into the polymer matrix. The results demonstrate that molecular design—specifically, introducing steric hindrance around the metal center—markedly enhances resistance to coordinating impurities. Full article

Nickel(II) and palladium(II) ions are capable of forming complexes with macrocyclic terapyrrole structures such as the porphyrin or corrin ring. Many different derivatives of these complexes are synthesized and studied because these compounds have potential numerous applications, including catalysis, various light-driven chemical reactions and processes related to intramolecular and intermolecular energy redistribution. Nickel porphyrins exhibit neither fluorescence nor phosphorescence when excited with light; however, palladium porphyrins, when excited to the singlet state, very quickly transform into the triplet state, and unlike nickel porphyrins, deactivation of the excited states occurs by phosphorescence. Palladium corrin has dual luminescent properties and exhibits both a weak fluorescence and strong phosphorescence. These photophysical differences are based on the complex energetic redistribution of singlet and triplet excited states interacting with each other in the intersystem crossing process. Based on the results of calculations at the DFT/TDDFT and CASSCF/NEVPT2 levels of theory, the structure of electronic excited states of model nickel(II) and palladium(II) complexes with corrin and porphyrin macro-rings was characterized and potential paths of photophysical processes leading to the occupancy of low-lying triplet states were described. In nickel complexes, very low-energy triplet states are the main cause of the rapid radiationless deactivation of excited states via triplet photophysical pathways. Full article

Metal ions exemplify one of the most harmful and environmentally detrimental contaminants of water systems. This work describes the creation of an innovative chelated carbon-doped nickel and titanium oxide (C-NiTiO₂) hybrid as an adsorbent for the effective elimination of metal ions. The dominance of the TiO₂ anatase phase with a ≈ 61 nm crystallite size was verified by XRD and Raman investigation. Morphology investigations exposed polygonal nanoparticles consisting of Ti, C, Ni, and O. The nanostructure exhibited a surface area of 17 m²·g⁻¹, a pore diameter of ≈1.5 nm, and a pore volume of 0.0315 cm³·g⁻¹. The nanostructure was evaluated for the elimination of Zn (II) ions from an aqueous solution. The metal ion adsorption onto the hybrid nanomaterial was described and comprehended using adsorption kinetics and equilibrium models. The adsorption data matched well with the pseudo-second-order kinetics and Langmuir adsorption models, indicating a monolayer chemisorption mechanism and achieving a maximum Zn (II) ion elimination of 369 mg·g⁻¹. Mechanistic investigation indicated film diffusion-controlled adsorption through inner-sphere complexation. The nanosorbent could be regenerated and reused for four rounds without appreciable activity loss, thus demonstrating its potential for water cleanup applications. Full article

Copper and nickel ions play pivotal, albeit distinct, roles as essential trace elements in living systems, and primarily serve as co-factors for a range of enzymes. However, as with all trace metal ions, excessive concentrations can exert adverse toxicological properties. Interestingly, the incorporation of these in cell culture media can establish novel chemical interactions, with their speciation status markedly influencing characteristics, including cell maturation, and cellular uptake mechanisms. Thus, the primary objective of this study was to investigate and determine the speciation status (i.e., complexation) of nickel(II) and copper(II) ions by biomolecules present in RPMI 1640 mammalian cell culture medium using virtually non-invasive high-resolution proton NMR analysis, an investigation of much relevance to now routine studies of their toxicological actions towards cultured cells. Samples of the above aqueous culture medium were ¹H NMR-titrated with increasing added concentrations of 71–670 µmol/L Ni(II)(aq.), and 0.71–6.7, 7.1–67 and 71–670 µmol/L Cu(II)(aq.), in duplicate or triplicate. ¹H NMR spectra were acquired on a JEOL ECZ-600 spectrometer at 298 K. Results demonstrated that addition of increasing concentrations of Ni(II) and Cu(II) ions to the culture medium led to the selective broadening of a series of biomolecule resonances, results demonstrating their complexation by these agents. The most important complexants for Ni(II) were histidine > glutamine > acetate ≈ methionine ≈ lysine ≈ threonine ≈ branched-chain amino acids (BCAAs) > asparagine ≈ aspartate > tyrosine ≈ tryptophan, whereas for Cu(II) they were found to be histidine > glutamine > phenylalanine ≈ tyrosine ≈ nearly all remaining aliphatic metabolites (particularly the wealth of amino acids detectable) > 4-hydroxyphenylacetate (trace culture medium contaminant), in these orders. However, Cu(II) had the ability to influence the linewidths of these signals at much lower added levels (≤7 µmol/L) than that of Ni(II), the broadening effects of the latter occurring at concentrations which were approximately 10-fold greater. Virtually all of these added metal ion-induced resonance modifications were, as expected, reversible on addition of equivalent or excess levels of the chelator EDTA. From this study, changes in the co-ordination sphere of metal ions in physiological environments can give rise to marked modifications in their physicochemical properties (e.g., redox potentials, electronic charges, the potential catalytic generation of reactive oxygen species (ROS), and cell membrane passages). Moreover, given that the above metabolites may also function as potent hydroxyl radical (^●OH) scavengers, these findings suggest that generation of this aggressively reactive oxidant directly from Cu(II) and Ni(II) ions in physiologically-relevant complexes may be scavenged in a ‘site-dependent’ manner. This study is of further relevance to trace metal ion research in general since it enhances our understanding of the nature of their interactions with culture medium biomolecules, and therefore provides valuable information regarding their overall chemical and biological activities, and toxicities. Full article

Lithium-ion batteries are essential to ensure electric mobility and reduce CO₂ emissions from transportation. One of the most commonly used chemistries is nickel–cobalt–manganese (NMC) batteries, which also have applications beyond the automotive sector. The recycling of these batteries requires the development of technologies to enable the selective separation and recovery of the metals present in the battery. One of these selective technologies involves the use of deep eutectic solvents (DESs). This research study investigates the different parameters that influence the recovery of Co(II) from hydrochloric acid medium using the deep eutectic solvent 3 Aliquat 336:7 L-Menthol. Firstly, using synthetic Co(II) solutions, the parameters influencing the cobalt extraction process are examined, and then these optimal conditions are applied to the recovery of cobalt from solutions obtained by dissolving NMC 622 battery black mass in 10 M HCl. The obtained results show that the DES used is highly selective for Co(II) recovery compared to other metals present in the solution (Ni, Li and Mn), achieving recoveries of up to 90% of the cobalt initially present in solution. Stripping with H₂SO₄ 0.5 M allows the recovery of cobalt as a crystalline monohydrate salt (CoSO₄.H₂O). The optimization of the Co/Cu separation conditions is carried out, achieving the separation of Cu(II) using Aliquat 336 in kerosene. Full article

This study investigates the adsorption behavior of natural sepiolite for the removal of cadmium (Cd²⁺), copper (Cu²⁺), and nickel (Ni²⁺) ions from aqueous solutions under batch conditions. The sepiolite was extensively characterized prior to adsorption experiments. Mineralogical analysis confirmed the presence of crystalline sepiolite, while DTG-TGA revealed thermal stability with distinct weight loss linked to surface and structural water. BET analysis indicated a high surface area of 194 m²/g and a mesoporous structure favorable for adsorption. Batch experiments evaluated the effects of contact time, pH, adsorbent dosage, and initial metal concentration. Adsorption was highly pH-dependent, with maximum removal near-neutral pH values. Higher adsorbent dosages reduced in a lower adsorption capacity per unit mass, primarily because the fixed amount of solute was distributed over a larger number of available sites, leading to unsaturation of the adsorbent surface and possible particle agglomeration. Isotherm modeling revealed that the Langmuir model provided the best fit, indicating monolayer adsorption with maximum adsorption capacities of 15.95 mg/g for Cd(II), 37.31 mg/g for Cu(II), and 17.83 mg/g for Ni(II). Langmuir constants indicated favorable interactions. Kinetics showed rapid adsorption within the first hour, reaching equilibrium at 240 min through surface adsorption and intraparticle diffusion. Cu(II) exhibited the fastest uptake, while Ni(II) adsorbed more slowly, suggesting differences in diffusion rates among the metal ions. Desorption using 0.1 N HCl achieved over 80% efficiency for all metals, confirming sepiolite reusability. Overall, raw sepiolite is an effective, low-cost adsorbent for removing potentially toxic elements from water. Full article

The growing demand for lithium-ion batteries (LIBs) requires efficient and sustainable recycling solutions. This study investigates bioleaching as an alternative to conventional hydrometallurgical methods, focusing on (i) organic acid-mediated leaching with Gluconobacter oxydans and (ii) sulfuric acid bioleaching with Acidithiobacillus thiooxidans. Experiments were conducted at 26 °C with leaching durations of one to three weeks, depending on the microbial system, at pH 1.35 for sulfuric acid treatments, and with liquid-to-solid ratios equivalent to 100 mL g⁻¹ (A. thiooxidans) or 100 mL g⁻¹ in culture medium (G. oxydans). Results show that indirect bioleaching with G. oxydans achieved high recovery rates for cobalt (96%), manganese (100%), nickel (65%), and lithium (68%), while the direct approach was less effective due to microbial inhibition by black mass components. Similarly, biologically produced sulfuric acid exhibited moderate leaching efficiencies, but chemically synthesized sulfuric acid outperformed it, particularly for nickel (93%) and lithium (76%) after one week of leaching. These findings suggest that bioleaching is a promising, eco-friendly alternative for LIB recycling but requires further process optimization to improve metal recovery and industrial scalability. Future research should explore hybrid approaches combining bioleaching with conventional leaching techniques. Full article

The removal of nickel from industrial wastewater necessitates efficient sorbent materials. This study investigates nanostructured potassium- and sodium-substituted aluminosilicate-based nanocomposites for this application. Materials were synthesized and characterized using SEM-EDS, XPS, XRD, FTIR, low temperature N₂ adsorption–desorption and Ni²⁺ adsorption experiments. SEM and XRD confirmed an X-ray amorphous structure attributable to fine crystallite size. The sodium-substituted material Na₂Al₂Si₂O₈ exhibited the lowest specific surface area (48.3 m²/g) among the tested composites. However, it demonstrated the highest Ni(II) sorption capacity (64.6 mg/g, 1.1 mmol/g) and the most favorable sorption kinetics, as indicated by a Morris-Weber coefficient of 0.067 ± 0.008 mmol/(g·min¹/²). Potassium-substituted analogs with higher Si/Al ratios showed increased surface area but reduced capacity. Analysis by XPS and SEM-EDS established that Ni(II) uptake occurs through a complex mechanism, involving ion exchange, surface complexation, and chemisorption resulting in the formation of new nickel-containing composite surface phases. The results indicate that optimal sorption performance for Ni(II) is achieved with sodium-based aluminosilicates at a low Si/Al ratio (Si/Al = 1). The functional characteristics of Na₂Al₂Si₂O₈ compare favorably with other silicate-based sorbents, suggesting its potential utility for wastewater treatment. Further investigation is needed to elucidate the precise local coordination environment of the adsorbed nickel. Full article