8639 research outputs found
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ASSESSMENT OF GROUNDWATER QUALITY AND ITS SUITABILITY FOR DRINKING PURPOSES IN WESTERN SERBIA
No full textPodzemne vode predstavljaju ključni resurs za snabdevanje vodom za piće, međutim održivo korišćenje podzemnih voda suočava se sa sve većim izazovima usled industrijalizacije i urbanizacije. Da bi se procenio kvalitet i pogodnost vode za piće i druge namene, u radu su analizirani uzorci podzemne vode iz hidrogeološke bušotine koja doseže dubinu > 400 m. Pored poznatih hidrogeoloških karakteristika akvifera i litološkog profila bušotine, sprovedena su fizičko-hemijska, mikrobiološka, biološka, parazitološka i radiološka ispitivanja vode. Rezultati analiza pokazali su da ispitivani parametri zadovoljavaju kriterijume propisane normativom, osim sa aspekta povišene koncentracije Fe, Mn, B, i blago snižene pH vrednosti.Groundwater is a vital resource for drinking water supply; however, its sustainable use is increasingly threatened by industrialization and urbanization. To assess suitability for drinking and other purposes, this study analyzes the quality of groundwater samples obtained from a hydrogeological borehole reaching depths > 400 m. In addition to the known hydrogeological characteristics of the aquifer, and the lithological profile of the borehole, and physicochemical, microbiological, biological, parasitological, and radiological analyses of the water were conducted. The results showed that the examined parameters met the regulatory standards, except for elevated concentrations of Fe, Mn, B, and a slightly decreased pH value
Development of a Chestnut Shell Bio-Adsorbent for Cationic Pollutants: Encapsulation in an Alginate Carrier for Application in a Flow System
No full textMelanin-based biosorbents (MiCS), derived from chestnut shells, were encapsulated in sodium alginate to obtain MiCS@Alg, useful in a column adsorption study. MiCS contains various acidic surface groups able to participate in the removal of cationic pollutants from aqueous solutions. The MiCS and MiCS@Alg were characterized by Fourier-transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Dynamic Light Scattering (DLS), while zeta potential and particle size analyses were performed to gain deeper insight into surface charge behavior. Batch adsorption experiments were carried out at three different temperatures, demonstrating that the adsorption kinetics followed a pseudo-second-order (PSO) model and that the Freundlich model best described the equilibrium data. The process was found to be endothermic and spontaneous, with maximum adsorption capacities of 300.2 mg g−1 (BR2), 201.5 mg g−1 (BY28) and 73.08 mg g−1 (NH3) on MiCS, and 189.3 mg g−1 (BR2), 117.1 mg g−1 (BY28) and 50.06 mg g−1 (NH3) on MiCS@Alg at 45 °C and compared with the unmodified chestnut shell. The MiCS and MiCS@Alg exhibited good adsorption performance, improved environmental compatibility, and greater reusability. Overall, these results highlight MiCS@Alg as a cost-effective, sustainable, and highly promising novel biosorbent for the removal of cationic pollutants (BR2, BY28, and NH3) from water
Enhanced Arsenic Removal Using an Iron-Modified Sandy Clay and Biochar
No full textThis study presents the development of a novel composite adsorbent based on natural
sandy clay, iron(III)-modified, and dry-mixed with a walnut shell-derived biochar, aimed to achieve
arsenic removal from aqueous solutions. The synergistic combination of high porosity and
functionality of biochar, with the strong affinity of Fe(III) toward arsenic species, resulted in
significantly enhanced adsorption properties. Experimental investigations demonstrated that the
incorporation of Fe(III) notably increases the number of active sites, leading to a higher overall
adsorption capacity, even in the presence of competing ions commonly found in real water matrices.
The predominant adsorption mechanism involves surface complexation of arsenic ions with Fe(III)
centers, supplemented by physisorption and interactions with biochar-derived functional groups.
These findings emphasize the high potential of a cost-effective and eco-friendly adsorbent for largescale applications in arsenic-contaminated waters, particularly in regions lacking access to
advanced remediation technologies. This work contributes to the growing body of research focused
on the valorization of agricultural waste and natural resources for sustainable environmental
solutions
Development of coatings for the protection of metals structures based on pyrophyllite, zeolite and talc
No full textThe goal of this work is the development of two types of protective coatings based on pyrophyllite and talc and coatings based on pyrophyllite and zeolite. For two types of coatings, a mixture of 80% pyrophyllite, grain size 20 μm and 20% talc, grain size 15 μm, i.e. 80 % pyrophyllite, grain size 20 μm and 20% zeolite, grain size 15 μm, was used as a filler, respectively. In the composition of the coating, the total amount of refractory filler was 85%, binder based on epoxy resin 7-10%, 1-2% organic additives and solvent based on water. Pyrophyllite contributed to the improvement of thermos stability and mechanical resistance of the coating, talc improved the ability to adhere and coat filler grains, while zeolite contributed to the improvement of microporous adsorption of active phases, gases, heat, toxins, heavy metals. The manufacturing technologiesof these coatings are ecologically clean. The characterization of the obtained coatings was carried out using the XRD, SEM and ultrasonic vibration method with a stationary sample according to the ASTM G32 standard. Research has shown that the obtained coatings increase the anti-corrosive and thermal protection of metal substrates, and in particular, the resistance to wear and cavitation erosion is increased. This provides wide possibilities of application of these coatings in industry, construction, energy, military industry
g-C3N4/SiO2 composites obtained by the microemulsion-assisted sol-gel method for the photocatalytic reduction of Cr(VI)
No full textGraphitic carbon nitride (g-C₃N₄) has demonstrated considerable potential for sustainable photocatalytic reduction of toxic hexavalent chromium (Cr(VI)) due to its suitable band gap for visible light absorption, an appropriate conduction band edge potential, and stability [1]. However, the industrial application of g-C3N4 is restricted due to its low specific surface area (SSA) and the rapid recombination of photogenerated electrons (e-) and holes (h+). In order to overcome these drawbacks, g-C3N4 is frequently combined with other materials to form heterojunctions for efficient e-/h+ separation, thereby promoting pore development to increase SSA. The incorporation of g-C3N4 in nanostructured mesoporous silica has been shown as a favorable strategy for increasing the SSA and enhancing the separation efficiency e-/h+ [2].
In this work, the microemulsion-assisted sol-gel method combined with a cationic surfactant [3] was used to synthesize spherical mesoporous silica particles (MSP) of high SSA, which were further impregnated with urea as a precursor for g-C₃N₄. The impregnation process was carried out using as-synthesized or calcined MSP, so the g-C3N4/SiO2 composites were obtained by a one-step or two-step solid-state calcination procedure, respectively. For the comparison, bare g-C3N4 was synthesized by urea thermal treatment at the same temperature. The properties of synthesized samples were studied by FESEM, FTIR, XRD, BET, DRS, and DTA/TGA analyses, as well as by determination of the point of zero charge. The photocatalytic reduction of Cr(VI) was examined under constant concentration (10 mg/l), at pH 3, under simulated visible radiation, and in the presence of citric acid as a hole scavenger.
A comparison of the composites with the bare g-C₃N₄ and pure MSP was conducted to investigate the factors contributing to the enhanced photocatalytic activity of the composites. The analysis revealed that the reduced aggregation of g-C₃N₄ was a primary factor, though the calcination procedure and surface properties were also found to play a significant role in activity levels
Controlled release of ADSC-derived EVs from 3D-Printed PMMA-gelatin scaffolds for bone regeneration
No full textBone tissue engineering aims to develop advanced biomaterials that support regeneration and enable targeted delivery of bioactive molecules. Extracellular vesicles (EVs), secreted by mesenchymal stem/stromal cells (MSCs), emerge as potent mediators of tissue repair. This study explores a novel 3D-printed scaffold system for the controlled release of EVs derived from rat adipose-derived stem cells (ADSCs). EVs circumvent many of the challenges associated with cell-based therapies, offering a safer, more stable, and easily controllable alternative for clinical applications. Their incorporation into structurally supportive and biodegradable scaffolds can enhance local retention, protect bioactivity, and improve regenerative efficacy at the defect site. Polymethyl methacrylate (PMMA)-gelatin scaffolds were fabricated using the mask-stereolithography 3D printing method and characterized in terms of printability, swelling behavior, mechanical properties and microstructure. The scaffolds were subsequently coated with a collagen-based hydrogel pre-loaded with ADSC-derived EVs. EV release kinetics were assessed in phosphate-buffered saline (PBS) at 37 °C over a 14-day period, with fluorescently labeled EVs quantified via nanoparticle tracking analysis (NTA).The results show that the composite system enables controlled and sustained EV release, supported by the hydrogel’s retention capacity and scaffold’s structural integrity. This dual-phase platform offers a promising approach for localized delivery of therapeutic EVs in bone tissue engineering applications
Changes in dimensional, mechanical and comfort properties in cotton and wool double weft knitted fabrics caused by washing
No full textThis study examines the dimensional, mechanical (bursting strength, ball traverse elongation, compressibility, and compressive resilience), and comfort-related properties (air permeability, water vapor resistance, volume electrical resistivity, and water retention) of double-weft knitted fabrics made from cotton and wool, using 1 × 1 rib and Milano rib structure, that develop during the washing process. The results reveal that yarn composition, knit structure, and washing conditions have a significant influence on the fabric’s performance after washing, particularly in terms of dimensional stability and structural integrity. Cotton fabrics exhibited greater dimensional changes after washing compared to wool fabrics. Isotropic shrinkage was observed in cotton Milano rib and wool 1 × 1 rib fabrics, while anisotropic dimensional changes occurred in cotton 1 × 1 rib and wool Milano rib fabrics. Wool fabrics had shorter initial stitch lengths and a higher mass per unit area, indicating coarser yarns and denser knit structures. Cotton fabrics, particularly those with a 1 × 1 rib structure, experienced notable reductions in bursting strength, compressibility, and air permeability. In contrast, wool fabrics, especially with a 1 × 1 rib structure, showed improved mechanical properties after washing. Across all samples, comfort-related properties declined after washing, with cotton fabrics experiencing more significant deterioration, likely due to increased sensitivity to conducted washing stresses. Overall performance rankings indicated that wool fabrics in the 1 × 1 rib structure maintained the greatest stability after washing, whereas cotton fabrics in the same knit structure exhibited the most substantial deterioration in performance. These findings provide valuable guidance for selecting yarn composition and knit structure type to enhance the dimensional stability, and functional performance of knitted products. The influence of yarn process and structure has not been taken into consideration
Two-dimensional Monte Carlo simulation coupled with multilinear regression modeling of source-specific health risks from groundwater
No full textEffective protection of groundwater requires an accurate health risk assessment of contaminants; however, the diversity of pollution sources, variability, and uncertainties in exposure parameters present significant challenges in this assessment. In this study, groundwater risk estimates associated with NO3-, and F-, along with fourteen heavy metal(loid)s (V, Cr, Mn, Fe, Ni, Cu, As, Co, Cd, Se, Pb, Hg, Zn, and Al) in an agricultural area were optimized by implementing positive matrix factorization (PMF), multilinear regression, and two-dimensional Monte Carlo simulations to characterize source-specific health risks. Groundwater pollution was analyzed considering regional variations, including differences in elevation, land use and land cover, and soil types. Three pollution sources were identified: agricultural practices, traffic, and natural processes. Moreover, the results revealed NO3- from an agricultural source as the primary control contaminant. Additionally, both adults and children in the study area face significant non-carcinogenic health risks. To mitigate these risks, this study recommends maximum consumption levels of 1.44 L/day for adults and 0.35 L/day for children. Furthermore, adults weighing > 68.1 kg and children weighing > 15.9 kg are likely to be at reduced risk of experiencing adverse health effects. Compared to deterministic health risk assessment and one-dimensional Monte Carlo simulation of health risks, two-dimensional Monte Carlo simulation showed improved performance, providing better accuracy and higher precision in health risk assessment results. Thus, this research is expected to enhance the understanding of health risk assessment related to groundwater and to provide valuable guidance for managing groundwater pollution
Synthesis and properties of in situ prepared polyurethane/PEG-MXene nanocomposites
No full textThe efficiency of flexible electronic devices based on MXene/polymer composites can be enhanced by careful design of MXenes and polymers and tailored polymer composition for enhanced electrical conductivity, thermal, and mechanical properties. This study describes the production and analysis of novel 2-[methoxy(polyethyleneoxy)6-9propyl]trimethoxysilane (PEG)-silane functionalized MXene and novel polyurethane (PU) nanocomposites with a range of soft segment contents from 30 to 60 wt%. The functionalization of titanium carbide MXene with (PEG) to produce a material with a layered structure was confirmed by Fourier-transform infrared (FTIR) analysis, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), while transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis showed increased MXene nanosheet interlayer spacing after functionalization. After functionalization, the measured mean MXene nanosheet interlayer spacing was 1.57 μm. A series of polyurethane nanocomposites with the addition of 1 wt% PEG-MXene was synthesized in situ using a two-step polyaddition polymerization method. The prepared nanocomposites with intercalated structure had better thermal properties (Tg from 48 to 62 °C and degradation temperature from 278 to 297 °C), mechanical properties (Young's modulus from 8 to 84 MPa and tensile strength from 2 to 11 MPa), and suitable surface characteristics (low roughness coefficient, from 11 to 87 nm and similar to high water contact angle, from 73 to 109°) as compared to pure PU. The addition of PEG-MXene enhanced microphase separation (degree of phase separation from 16.9 to 50.1 %) and strengthened hydrogen bonding (hydrogen bonding index from 38.4 to 66.1 %) in the urethane structure. TEM revealed a 17 nm spacing between PEG-MXene and the PU matrix, and XPS verified the presence of PEG-MXene in PU. Among the novel materials, the nanocomposite with 50 wt% of soft segment content had the most desirable properties with regards to use in flexible electronic devices, i.e., this material had the best thermal, mechanical, and surface characteristics, including the lowest surface roughness (11 nm) and distinct microphase separation.Contains correction: [https://technorep.tmf.bg.ac.rs/handle/123456789/8200]Contains correction: [https://doi.org/10.1016/j.porgcoat.2025.109235
Modified Z-scheme heterojunction of TiO2/polypyrrole recyclable photocatalyst
No full textA straightforward physical mixing method was used to prepare the highly efficient TiO2/polypyrrole (PPy) photocatalysts of hydrothermally prepared TiO2 and PPy, obtained by the chemical oxidative polymerization, with different amounts of PPy (0, 0.5, 1, 1.5, 3, and 5 wt.%). Synthesized composites were characterized by XRPD, FTIR, FESEM, EDS, BET, and UV–Vis methods, while their photocatalytic activity was estimated towards the degradation of toxic dye Reactive Orange 16 (RO16) based on UV–Vis and TOC. XRPD showed that the TiO2 was obtained as nanoanatase with crystallites of 26 nm. Band gap energies of the nanocomposites decreased with the PPy content increase from 3.11(3) to 2.94(3) eV. The TiO2/1%PPy demonstrated the highest photocatalytic activity by completely degrading RO16 for 120 min under simulated solar light with degradation described by the pseudo-first reaction order with the rate constant of 0.056(5) min−1. It was established that 73% of the total reactive oxidative species were h+ and that the photodegradation mechanism followed a slightly modified direct Z-scheme in which PPy played an active and irreplaceable role by opening a new reaction path. Besides extremely high photocatalytic efficiency, the recyclability of TiO2/1%PPy was confirmed since no decrease in efficiency was found after several runs of photocatalysis