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Citric acid functionalized chitosan hydrogel beads for enhanced Cr(VI) removal: Experimental assessment and COMSOL modelling of adsorption in a fixed-bed system
No full textChitosan hydrogel beads (CHB) and cross-linked CHB functionalized with tricarboxylic citric acid (CA-GLA-CHB) were synthesized and used for the removal of Cr(VI) from aqueous solutions in batch and dynamic adsorption systems. Applicability of COMSOL Multiphysics software as a tool for predictive modelling of column dynamics using a minimum set of experimental parameters was tested and compared with experimental results. Batch experiments demonstrated that CA-GLA-CHB showed almost 20% higher adsorption capacity and wider operational pH range compared to non-functionalized CHB. In a dynamic system, CA-GLA-CHB was used as column packing material and the column dynamics was investigated at different conditions. The breakthrough and exhaustion time of the column increased with an increase in bed height and a decrease in feed flow rate and initial Cr(VI) concentration. Computational modeling by COMSOL software with implemented Advection-Dispersion-Reaction (ADR) equation was used to simulate breakthrough curves for the applied dynamic system in order to validate the possibility of its application for process design in the scaled-up fixed-bed column systems for wastewater treatment. The simulated breakthrough curves of Cr(VI) adsorption matched well with the experimental, thus proving that COMSOL Multiphysics software can be used for scaling-up fixed-bed column systems packed with low-cost and effective CA-GLA-CHB bioadsorbent
Influence of the high absorbing nonilluminated surface of the sample on the photothermally induced thermoelastic bending
No full textThis paper presents a model for the thermoelastic component of the photoacoustic response for the sample that consists of an unilluminated high absorption protective layer (ideal surface optical absorber), with the material of interest positioned at the front side. Analytical expressions for the amplitude and phase of this component were derived. The study examined the effect of the optical absorption coefficient on the thermoelastic component across different sample thicknesses, noting a behavioral change at an optical absorbance value of 1.5. Additionally, the sensitivity of the thermoelastic component to optical absorbance and the influence of the optical absorption coefficient on surface temperature variations were analyzed to clarify this behavior. Our findings demonstrate that the optical absorption coefficient in samples with an optically opaque back-side layer significantly affects the thermoelastic component of the photoacoustic signal. This implies that the gas microphone photoacoustics can effectively evaluate the optical properties of semi-transparent samples. © 2025 Elsevier Masson SA
Enhanced Adsorption–Photocatalytic Degradation of the Congo Red Dye in the Presence of the MOF/Activated Carbon Composite Catalysts
No full textThe extensive application of synthetic dyes in various industries and potential accidental uncontrolled discharge into natural water bodies have led to significant environmental challenges and a need for effective treatment. In this study, UiO-66 metal–organic framework/activated carbon (MOF/AC) composites were used to evaluate the photocatalytic degradation of Congo Red dye (CR) in aqueous solution under natural solar irradiation. The degradation efficiency of CR was determined using UV-Vis spectroscopy, while material characterization and additional insight into the reaction mechanism were obtained by XRD, FTIR, and Raman analysis. For a 50 ppm CR solution, within a 2 h reaction time, pure MOF achieved 57.2% and 26.3% degradation under solar irradiation and dark conditions, respectively, while the 75/25 MOF/AC composite reached 74% and 38.3% under the same conditions. These results confirm the synergistic interaction between MOF and AC, where AC acts as an electron sink, preventing charge recombination and enhancing photocatalytic activity. Chemisorption occurred simultaneously with photocatalytic degradation on the MOF surface. Reusability tests showed that pure MOF retained the highest stability over repeated cycles. Overall, the combination of MOF and AC enhances catalytic performance, which represents a sustainable approach for treating dye-contaminated wastewater under natural solar conditions
Synthesis and Characterization of Eco-Engineered Hollow Fe2O3/Carbon Nanocomposite Spheres: Evaluating Structural, Optical, Antibacterial, and Lead Adsorption Properties
No full textThis work presents a facile mechano-thermal route for the synthesis of carbon-decorated, hollow, mesoporous α-Fe2O3 microspheres. Comprehensive characterization (XRD, XPS, FT-IR, SEM/EDX, TGA, zeta-potential) confirmed the formation of phase-pure hematite with nanoscale crystallites (~19 nm), substantial residual surface carbon (~40 wt%) consistent with Fe–O–C linkages, and a positive surface charge (+15.9 mV). The hierarchical hollow/mesoporous architecture enables fast ion transport and provides extensive interior binding sites, resulting in rapid Pb(II) uptake that reaches 92% removal in ≈15 min at pH 5.0. The adsorption follows a Langmuir isotherm (qmax ≈ 70.6 mg/g) and pseudo-second-order kinetics, indicative of chemisorption coupled to efficient mass transfer into internal sites. The composite also exhibits antibacterial activity against Escherichia coli and Staphylococcus aureus, demonstrating its potential for simultaneous mitigation of heavy metal contaminants and pathogens
Double magnetization reversal in Er3Fe5O12garnet nanocrystals
No full textEr3Fe5O12 nanoparticles were synthesized via the sol-gel method, yielding an Ia3d garnet structure, as confirmed by XRD, HRTEM, EDX, and Raman spectroscopy. Magnetic measurements showed that the temperature of magnetic compensation is 75 K (Tcomp1), and that the coercive field exhibits a single peak near Tcomp1. Above Tcomp1, the coercive field was found to be proportional to the susceptibility of the Er3+paraprocess. Zero-field-cooled (ZFC) and field-cooled (FC) measurements were performed, including both cooling (FCC) and warming (FCW) cycles. FCC measurements revealed double magnetization reversal, with two compensation temperatures, observed for the first time in Er3Fe5O12. At Tcomp1, the magnetization switches from positive to negative, whereas at the lower Tcomp2, it switches from negative to positive. Tcomp2 depends on the applied field and increases with increasing field, and for fields above 1000 Oe, the magnetization reversal no longer occurs. In contrast, these magnetization reversals are completely absent in the FCW regime. Additionally, Er3Fe5O12 nanoparticles exhibit magnetization switching, where the magnetization orientation can be reversed by changing only the magnitude of the applied field while keeping its direction fixed. The observed double magnetization reversal is attributed to a strong magnetocrystalline anisotropy opposing the Zeeman-driven realignment of magnetization
Efficient radionuclide capture using thermally processed materials
No full textGenerating electricity using fission nuclear reactors is a potential method to reduce carbon dioxide emissions. Additionally, nuclear reactors are regarded as reliable production systems. However, apart from the high costs associated with building and maintaining nuclear power plants, the treatment of liquid radioactive waste poses a significant challenge. There is extensive research on the concentration of radionuclides, such as unstable isotopes of copper, lead, nickel, strontium, cesium, etc. from liquid phases onto solid matrices. While commercial ion-exchange resins are commonly used as solid matrices, any material that can bind these isotopes—which are primarily found in ionic form in liquid waste—can be utilized. Materials with notable sorption properties often include those that have been subjected to thermal treatment. For instance, the heat treatment of materials high in carbon can produce either ash or biochar, depending on the conditions of the process. Biochar, in particular, is known for its large specific surface area, which is essential for their effectiveness as sorbents. In addition to the transformation of organic matter due to high temperatures, the thermal treatment of inorganic materials also enhances their sorption properties. Research has shown that changes in structure positively impact the sorption capacity of minerals like bentonite, as well as waste inorganic materials such as red mud. This paper summarizes previous research on the sorption performance of thermally treated materials that can be used in the treatment of liquid radioactive waste.International conference on radiation applications in Physics, Chemistry, Biology, Medical Sciences, Engineering and Environmental Sciences : May 26-30, Crete, Greece
Propagation and Stability of Compact Localized Modes in 2D Photonic Flat-band Lattices
No full textPhotonic lattices with flat bands, characterized by the absence of dispersion and slow group velocity, support compact localized modes (CLMs) known as compactons. Light propagation can be controlled by tuning parameters such as waveguide spacing and wave profile. When the light intensity is sufficient, modulation instabilities can emerge, inducing a nonlinear response that alters propagation. Special attention is given to the Aharonov–Bohm effect and the influence of phase shifts and inhomogeneities on light dynamics and mode formation. The propagation of light through photonic lattices can be modeled by a system of coupled differencedifferential equations under the strong coupling approximation, with each waveguide interacting with its nearest neighbors. Assuming ideal conditions (no losses and infinite waveguides), and incorporating Kerr-type nonlinearity while neglecting diffraction and diffusion, this system reduces to a set of discrete nonlinear Schrödinger equations. Unit cells in photonic lattices are defined analogously to those in solid-state systems, enabling simplification of the governing equations. We examined the existence and stability of both linear and nonlinear localized modes in 2D photonic lattices using three models: octagonal-diamond [1,2], dice [3], and plus-type [4,5]. The sixth-order Runge-Kutta method was applied to solve the governing equations. Analytical solutions were used to obtain eigenvalues of the Hamiltonian and the structure of CLMs. Linear stability analysis (LSA) provided equations for small perturbations, which were numerically solved to evaluate the stability of specific modes. By using analytical and numerical tools we confirmed the existence and behavior of both linear and nonlinear CLMs. While LSA offered useful insight into the stability spectrum of stationary solutions, it proved insufficient for capturing all features of compact modes, particularly in the presence of inhomogeneities. In such cases, direct numerical simulations were essential for verifying stability. These simulations revealed that the presence or absence of an external magnetic flux significantly affects the behavior and robustness of the observed modes.X International School and Conference on Photonics : PHOTONICA2023 : book of abstracts; 25 - 29 August 2025 Belgrade, Serbia
Modified urea-formaldehyde resins as dye adsorbents
No full textThirteenth International Conference on Radiation Natural Sciences, Medicine, Engineering, Technology and Ecology : June 16-20, 2025, Herceg Novi, Montenegro
The electrolyte effects on the kinetics of hydrogen and oxygen evolution reaction on polycrystalline nickel in alkaline media
No full textUnderstanding and controlling electrolyte effects is essential for improving the efficiency and reliability of alkaline water electrolysis. In this study, we systematically investigate the influence of alkali cation identity (Li+, Na+, K+) and concentration, as well as surface oxidation, on the kinetics of hydrogen and oxygen evolution reactions (HER and OER) on polycrystalline nickel. HER performance was found to be optimal in 0.1 mol dm−3 NaOH, while OER activity improved with increasing KOH concentration (1.0 mol dm−3 vs. 0.1 mol dm−3). In contrast, lithium-containing electrolytes consistently suppressed both reactions, likely due to the strong hydration of cations hindering interfacial charge transfer. Controlled anodic oxidation enhanced HER through the formation of β-Ni(OH)2 and Ni|Ni(OH)2 interfaces. In contrast, more extensive oxidation leading to NiOOH formation suppressed HER but had a more nuanced impact on OER. These results reveal a strong interplay between surface chemistry and electrolyte composition, with significant implications for both fundamental mechanistic understanding and practical catalyst optimization. The findings also highlight the importance of carefully defining electrolyte identity and electrode pre-treatment when benchmarking HER activity on nickel-based materials
Chemometric modeling for blood–brain-barrier permeability prediction of protein kinase inhibitors
No full textLimited passage through the blood-brain barrier (BBB) poses a major challenge in developing therapeutics for the central nervous system (CNS), especially for protein kinase inhibitors, which have high potential for treating different neurological disorders and malignancies. This study investigates the passive permeability of 34 diverse compounds, comprising both approved protein kinase inhibitors and experimental compounds, using the parallel artificial membrane permeability assay (PAMPA-BBB). Quantitative structure-property relationship (QSPR) models were developed utilizing Multiple Linear Regression (MLR), Support Vector Machine Regression (SVM), and Artificial Neural Networks (ANN). These models employed molecular descriptors of the compounds to create predictive models for assessing the permeability of other compounds. The study found that among the molecular descriptors, CATS2D_04_AA had the strongest positive correlation with logPe, indicating enhanced BBB permeability, while CATS2D_09_DA negatively impacted permeability. Both linear (MLR) and nonlinear (ANN and SVM) models confirmed these relationships, with the SVM model showing better performance due to capturing nonlinear dependencies, particularly for descriptors like CATS2D_04_AA and F07[C-N]. Optimizing structural features, including reducing hydrogen bond donors, was proposed to improve BBB permeability, thus offering guidance for the design of kinase inhibitors with improved CNS delivery potential. The integration of PAMPA-BBB assays with robust QSAR modeling provides a reliable framework for optimizing CNS-targeted drug candidates.ICCBIKG 2025 : 3rd International Conference on Chemo and Bioinformatics, September 25-26, 2025; Kragujevac, Serbia