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Influence of Morphology of Electrodeposited Copper on the Electrochemical Regeneration of Nicotinamide Adenine Dinucleotide (1,4-NADH)
No full textThis study investigates how copper electrode morphology influences the electrochemical regeneration of 1,4-NADH. Bioelectrochemical systems that couple enzymatic catalysis with electrochemical redox reactions are emerging as promising platforms for developing sustainable industrial processes, and efficient NADH regeneration is central to their performance. Electrochemical deposition (ED) offers a low-cost, rapid, and environmentally friendly route to fabricate metal electrodes with tailored surface morphologies. By adjusting deposition parameters—current density or overpotential, temperature, time, electrolyte type and composition, additives (levelers/brighteners), and agitation—as well as employing constant or periodically pulsed deposition regimes, the morphology of deposited copper can be precisely tuned. We show that the resulting copper morphologies markedly impact the efficiency and selectivity of 1,4-NADH electroregeneration, identifying copper as a promising electrocatalyst for bioelectrochemical applications
Optimizing alginate immobilization of food-derived C-phycocyanin: structural and functional characterization
No full textC-phycocyanin (C-PC) represents a significant component of the
cyanobacteria Arthrospira platensis (Spirulina) biomass. Beyond its nutritional
value, this protein exhibits numerous beneficial biological activities. A
covalently attached chromophore, phycocyanobilin, gives C-PC a blue color,
enabling its use as a natural food colorant. Additionally, phycocyanobilin
exhibits various bioactive properties, including metal-binding activities. A key
drawback to the broader industrial application of C-PC is its poor stability.
Alternative food formulations using natural polymers as carriers and active
components have recently gained considerable scientific attention. This paper
describes optimized conditions for C-PC immobilization using alginate. The
structural stabilization of immobilized C-PC was analyzed under high
temperature (60°C) and high pressure (450 MPa). The storage stability of
immobilized C-PC in dried alginate beads was tested by keeping the samples at
4°C for one month. The potential application of immobilized C-PC for the
removal of mercury ions was also investigated. Alginate immobilization proved
effective in stabilizing C-PC, significantly preserving its structure during
prolonged storage, thermal treatment, and high-pressure exposure. Under the
tested conditions, 97% of Hg2+ ions were removed by immobilized C-PC.
Overall, this study optimized the procedure for enhancing C-PC stability through
alginate immobilization and broadened its potential applications in food and
bioremediation industries
Zeolite fixed-bed system enhanced with recirculation for improved copper ion removal from wastewater: Kinetic models and comparison with batch system
No full textThis research investigates the feasibility of a novel approach involving a fixed-bed column system with recirculation for copper ion removal from wastewater. Adsorption kinetics of zeolites were examined using a well-established batch system and compared to a fixed-bed column recirculation system, a configuration for which only limited investigations exist. Zeolite was chosen as the adsorbent due to its efficiency, affordability, availability, and eco-friendliness. The recirculation system was designed for comparative analysis with the batch system, assessing adsorption kinetics, reaction rate constants, and orders under various initial copper concentrations (100, 300, and 500 mg dm−3). Zeolite particles (2–3 mm) were used in the recirculation system, while finer particles (63 µm) were employed in the batch system. Experimental conditions, such as adsorbent dosage and initial pH, were kept constant to ensure the comparability of the two systems. Copper concentrations in the filtrate were measured using an atomic absorption spectrophotometer (AAS). Three experimental kinetic models were developed to describe the adsorption processes. The results indicate that the adsorption processes correlate best with Ho’s pseudo-second-order (PSO) kinetic model. Results revealed superior removal efficiency (9.77 mg g−1) with the recirculation system using coarser particles compared to the batch system (7.82 mg g−1) with finer particles, highlighting enhanced adsorption driving forces in the recirculation configuration. The fixed-bed column system with recirculation demonstrates superior efficiency over batch systems and reduced processing time compared to conventional fixed-bed configurations
Evaluation of Adhesion Properties of Electrodeposited Copper Thin Films: Theoretical and Experimental Approach
No full textThe adhesion of copper thin films galvanostatically electrodeposited on Cu cathodes from electrolytes without or with the addition of various additives, such as chloride ions, polyethylene glycol 6000 (PEG 6000), and 3–mercapto–1–propanesulfonic acid, has been investigated. Morphological and structural analyses of synthesized films were performed using the SEM, AFM, and XRD methods, while the adhesion of the films was examined by applying the theoretical Chen–Gao (C–G) composite hardness model using results from Vickers microindentation, a bidirectional bending test, and a scratch-tape adhesion test. The morphologies of the films were either very smooth, with mirror-like brightness, obtained from the electrolyte containing all three additives, or microcrystalline, with different grain sizes, obtained from other electrolytes. The best adhesion was observed in the fine-grained film with numerous boundaries among grains, obtained with the addition of chloride ions and PEG 6000, while the mirror-bright film obtained with a combination of all three additives showed the worst adhesion. The boundaries among grains represented barriers that decreased the depth of penetration during microindentation and, consequently, increased the hardness and enhanced the adhesion of the film. The size of the grains—and hence, the number of grain boundaries—was regulated by the composition of the electrolytes achieved by the addition of additives. Good agreement was observed among the various methods used for the estimation of the adhesion properties of Cu films
Microwave Ir oxide-encapsulated spray pyrolitic microspheres of rare earth oxides as an electrocatalyst for oxygen evolution
No full textWater electrolysis, powered by sustainable energy sources, represents a key technology for a green hydrogen production, offering a clean and renewable energy solution. However, the efficiency of this process is primarily constrained by the sluggish kinetics of the oxygen evolution reaction (OER), which significantly increases the overall energy demands. To overcome this limitation, highly active and stable OER catalysts are required to enhance reaction efficiency and reduce energy losses. Among the known OER catalysts, iridium(IV) oxide (IrO2) is considered the most effective due to its exceptional activity and durability in acidic environments. Nevertheless, given the high cost and scarcity of iridium, optimizing its utilization and catalytic efficiency is crucial. This can be achieved through the development of advanced synthesis strategies and the incorporation of interactive supporting materials that enhance catalytic performance while minimizing Ir consumption. This study presents an innovative synthesis approach that combines ultrasonic spray pyrolysis (USP) for the preparation of rare-earth-based oxide as catalyst carrier with their subsequent microwave hydrothermal encapsulation by IrO2. Ce/Y (∑M) oxide supports were synthesized using a one-step USP process in which precursor aqueous solutions of CeCl3 and Y(NO3)3 were mixed in mole ratios of Ce:Y = 4:1 and Ce:Y = 1:4. The conversion temperature during spray pyrolysis was regulated using a thermostated furnace, ensuring uniform particle formation and phase composition. The nebulization and aerosol formation process was carried out in an oxygen atmosphere, with a controlled carrier gas (oxygen) flow rate of 2 dm3 min⁻1, while the synthesis temperature was maintained at 800 °C to promote the formation of CeO2/Y2O3 composite structures with the desired crystallinity and morphology. Following the synthesis of oxide USP powders, the materials were further processed via microwave hydrothermal treatment in the presence of IrCl3 under constant temperature conditions, leading to the formation of composite materials with varying IrO2 mole ratios (projected to ∑M:Ir = 3:7 and ∑M:Ir = 7:3). The resulting composites of IrO2-shelled CeO2/Y2O3 microspheres were systematically characterized to assess their electrochemical properties and catalytic activity for OER. Particular emphasis was placed on evaluating the synergistic effects of CeO2 and Y2O3 within the composite structures, as well as their role in enhancing the catalytic performance of IrO2. The study provides insight into how the interaction between these oxide catalyst carriers and IrO2 influences overall OER efficiency, shedding light on potential strategies for improving the sustainability and cost-effectiveness of high-performance water-splitting catalysts
Green extraction of critical metals: chemical leaching and electrochemical recovery from coal
No full textThis study investigates the selective recovery of critical metals from coal through chemical
leaching and electrochemical processes, with a focus on copper (Cu) recovery. Chemical
leaching was performed using 15 vol.% HNO₃ at 60 °C for 30 minutes per cycle. After each
leaching step, a new coal sample was introduced, while the used acid was replenished
with concentrated HNO₃ to maintain a consistent 15 vol.% concentration. This process
was repeated for six cycles, leading to the progressive accumulation of leached metal ions
in the solution.
The composition of the leachate, analyzed via ICP-OES, revealed increasing
concentrations of metals, with Fe and Zn being predominant. Electrochemical studies,
including cyclic voltammetry (CV) and linear sweep voltammetry (LSV), were conducted to
evaluate the feasibility of Cu recovery and the influence of co-leached metals, particularly
Pb and Fe. LSV results demonstrated that Pb did not significantly hinder Cu recovery, as
indicated by distinct Cu redox peaks. Selective Cu deposition was achieved by controlling
the applied potential, with reduction occurring at -0.70 V. Furthermore, Cu was
successfully deposited by holding the potential at -0.10 V and subsequently oxidized at
approximately 0.15 V during the anodic sweep, confirming its electrochemical
recoverability.
These findings highlight the potential of chemical leaching combined with
electrochemical recovery as a sustainable strategy for extracting critical metals from coal.
This approach supports circular economy principles by minimizing waste, reducing the
need for virgin raw materials and valorizing coal as a secondary resource for metal
recovery
Silica matrix-driven modulation of ferrite nanoparticles: Insights into synthesis, coercivity and magnetization
No full textThis study introduces a thermal decomposition synthesis method to synthesize bare and embedded cobalt ferrite nanoparticles in a silica matrix, enabling a direct comparison between them to examine agglomeration and particle size effects on magnetic properties. XRPD confirmed the cubic spinel structure, with reduced crystallinity in the composite due to the amorphous silica. FTIR analysis verified CoFe2O4 incorporation into silica, showing metal–oxygen (560–410 cm−1) and Si–O–Si (1030 cm−1) bonds. TEM revealed agglomerated particles (≈30 nm) in bare CoFe2O4, whereas the composite exhibited smaller (≈20 nm), dispersed nanoparticles within the silica. The XPS spectra confirm that the Fe and Co ions in both samples exhibit oxidation states of Fe3+ and Co2+. Magnetic characterization showed contrasting behaviors: bare CoFe2O4 exhibited higher coercivity at 300 K (1509 Oe) but lower at 5 K (7172 Oe) compared to the composite (1073 Oe and 8407 Oe, respectively). These trends were linked to particle size distributions, with the silica matrix promoting smaller superparamagnetic nanoparticles and reduced inter-particle interactions. These behaviors are driven by the interplay between superparamagnetic and ferrimagnetic nanoparticle populations. The silica plays a key role in controlling particle size, agglomeration and magnetic properties, offering insights into tailoring nanocomposites for data storage, biomedicine, and catalysis. Future work should optimize cobalt ferrite weight percentages in the silica matrix to achieve control over particle size and agglomeration.Accepted version: [https://cer.ihtm.bg.ac.rs/handle/123456789/8300
On the tumor cell growth limiting potential of newly synthesized acridine-1,8-dione derivatives
No full textA series of acridine derivatives, namely 10-(4-substituted benzyl)-9-(4-hydroxyphenyl)-3,3,6,6-tetramethyl-3,4,6,7,9,10-tetrahydroacridine-1,8(2H,5H)-diones, was synthesized via the Hantzsch-type multicomponent reaction between dimedone, 4-hydroxybenzaldehyde and 4-substituted benzylamine. The cytotoxic potential of these compounds was evaluated against human ovarian (A2780), melanoma (A375), colon (HCT 116) and breast cancer (MCF-7) cell lines, as well as normal human lung fibroblasts (MRC-5) and keratinocytes (HaCaT). Tested cell lines displayed different but moderate sensitivity to the investigated compounds, with the exception of compounds with a methyl (2) and a bromo group on the benzyl ring (6). These two compounds were almost equally effective against all cancer cell lines tested, suggesting that their activity is more general and less dependent on cell-specific characteristics. Compound 2 showed satisfying solubility, thus appeared to be the most acceptable for further examination and the A375 cell line was selected as the platform for evaluating the compound as the most sensitive to the applied treatment. This compound was shown to induce cell cycle arrest in G2/M phase, accelerating aging manifested through development of differentiated as well as senescent-like phenotype and subsequent fragmentation of genetic material. All aforementioned effects were accompanied with strong increment in production of reactive oxygen/nitrogen species (ROS/RNS). Docking studies against topoisomerase IIβ, hypoxia-inducible factor (HIF) 2α and mitogen-activated extracellular signal-regulated kinase (MEK) 1 revealed that treatment with tested compound might interfere with key signaling pathways involved in cell proliferation, and metabolic features of crucial importance for tumor progression. The obtained results contribute to the expansion of biologically relevant chemical space, thus providing guidelines for the assessment of new candidates for anticancer drugs
GMA/Ag composite as antimicrobial agent
No full textSilver, a precious metal used across various industries, can be released into the environment as a byproduct of industrial activities, potentially leading to environmental pollution. Consequently, removing silver from wastewater is crucial for enhancing environmental quality. Porous synthetic polymers (composites), with their high specific surface area and unique physico-chemical properties, have garnered interest as effective sorbents in environmental protection. Glycidyl methacrylate (GMA)-based composites are widely used in various applications such as sorbents (of metals, organic compounds, etc.), enzyme supports, and in biomedicine. The main objectives of this study were the synthesis, characterization, and investigation of the antimicrobial activity
of a novel GMA/Ag composite. For the synthesis of the composite, GMA as the monomer, and the crosslinker trimethylolpropane trimethacrylate (TMPTMA) were used, followed by functionalization with diethylenetriamine (DETA). Silver was incorporated into the composite by sorption from 0.1 M AgNO3 solution at pH 5, and 25°C, for 24h. The synthesized composite was characterized using Fourier-transform infrared spectroscopy (FTIR), and Scanning Electron Microscopy (SEM). The antimicrobial activity of the GMA/Ag composite was assessed using the agar-well diffusion method
against different microorganisms, including representatives of Gram-negative (Escherichia coli) and Gram-positive bacteria (Staphylococcus aureus), yeast (Candida albicans), and fungi (Aspergillus niger). The results of antimicrobial tests indicated that the GMA/Ag composite displayed good antimicrobial activity against the analyzed microbes, and it can potentially be used for biomedical applications, in the food and pharmaceutical industries , in the treatment of wastewater, etc
Aroma Profiling and Sensory Association of Six Raspberry Cultivars Using HS-SPME/GC-MS and OPLS-HDA
No full textIn this study, six club raspberry varieties were examined for their aromatic profiles and sensory qualities, and statistical approaches were used to determine how aroma components affect consumer impressions. Analysis of the aroma’s chemical composition was performed utilizing headspace SPME and GC-MS. MS-DIAL -v5.5.250627 software was used to identify components from commercial libraries, after 10 repetitions for each variety, followed by manual verification. A sensory evaluation of fresh fruits, with 55 volunteers, was statistically analyzed and linked to chemical composition using multivariate analysis and the OPLS-HDA classification method, which was employed for the first time. Tula Magic was scored the highest in the sensory evaluation compared to Adelita, Himbo Top, Glen Dee, San Rafael, and Cascade Harvest. 2-Heptanol (fresh, lemongrass-like, herbal, floral, fruity, green), heptanal (fresh, aldehydic, fatty, green, herbal), and 2-methyl-6-hepten-1-ol (oily-green, herbaceous-citrusy) separated Tula Magic from the other varieties assessed. The same components were recognized in OPLS as positive contributors to the flavor score, while terpenoids like trans-β-ionone, α-ionone, and α,β-dihydro-β-ionone, as well as 2-heptanone, scored slightly lower. This suggests that a fine balance between the individual components is key to the overall aroma sensation