Search Results (4,215)

This study aimed to determine the presence and characteristics of microplastics (MPs) in six commercially important fish species in Samsun city of, the Middle Black Sea Region: rainbow trout–Turkish salmon (Oncorhynchus mykiss), European seabass (Dicentrarchus labrax), gilthead seabream (Sparus aurata), red mullet (Mullus barbatus), horse mackerel (Trachurus mediterraneus), and whiting (Merlangius merlangus). The digestive systems of each species were examined, and MPs were classified according to their morphology, size, color, and polymer type. The analysis revealed that the number of MPs per individual ranged from 4.73 ± 1.13 to 9.26 ± 2.18, with the highest value found in rainbow trout and the lowest in whiting. MPs smaller than 100 µm were dominant (48.9%), and fiber (45.7%) and fragment (36.5%) types were the most common morphologies observed. Black and white/transparent colors were prominent in terms of color distribution, and ATR-FTIR analysis showed a dominance of widely used consumer plastics, such as polypropylene (PP, 31.3%) and polyethylene (PE, 23.9%). Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDS) results confirmed the presence of irregular, fibrous, and fragmented structures at microscopic scale, consistent with microplastic morphology. These findings indicate a potential risk of microplastic pollution in the region for both marine biota and human consumption. The study fills a significant data gap regarding the Middle Black Sea ecosystem and provides a foundation for future monitoring and risk assessment research. Full article

Urbanization generates large quantities of arsenic-contaminated excavated soils that pose environmental risks due to arsenic volatilization during high-temperature sintering processes. While these soils have potential for recycling into construction materials, their reuse is hindered by arsenic release. This study demonstrated calcium hydroxide (Ca(OH)₂) as a highly effective additive for suppressing arsenic volatilization during soil sintering, while simultaneously improving material properties. Through comprehensive characterization using inductively coupled plasma-mass spectrometry (ICP-MS), scanning electron microscopy (SEM) and X-ray microtomography (μCT), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), results demonstrated that Ca(OH)₂ addition (0.5–2 wt.%) reduces arsenic volatilization by 57% through formation of thermally stable calcium arsenate (Ca₃(AsO₄)₂). Ca(OH)₂ acted via two mechanisms: (a) chemical immobilization through Ca-As-O compound formation, (b) physical encapsulation in a calcium-aluminosilicate matrix during liquid-phase sintering, and (c) pH buffering that maintains arsenic in less volatile forms. Optimal performance was achieved at 0.5% Ca(OH)₂, yielding 9.14 MPa compressive strength (29% increase) with minimal arsenic leaching (<110 ppb). Microstructural analysis showed Ca(OH)₂ promoted densification while higher doses increased porosity. This work provides a practical solution for safe reuse of arsenic-contaminated soils, addressing both environmental concerns and material performance requirements for construction applications. Full article

Growing interest in sustainable hydrogen production has brought renewed attention to photoelectrochemical (PEC) water splitting as a promising route for direct solar-to-chemical energy conversion. This study explores how integrating hematite (α-Fe₂O₃) and cupric oxide (CuO) photoelectrodes with a series of nickel-based co-catalysts can improve photoelectrochemical activity. Photoanodic (NiO_x, NiFeO_x, NiWO₄) and photocathodic (Ni, NiCu, NiMo) co-catalysts were synthesized via co-precipitation and mechanochemical methods and characterized through X-ray Diffraction (XRD), X-ray Fluorescence (XRF), Transmission Electron Microscopy–Energy Dispersive X-ray Spectroscopy (TEM-EDX), Scanning Electron Microscopy–Energy Dispersive X-ray Spectroscopy (SEM-EDX), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) gas-adsorption analyses to clarify their crystallographic, morphological, and compositional properties, as well as their surface chemistry and textural properties (surface area and porosity). Electrochemical tests under 1 SUN illumination showed that NiO_x significantly improves the photocurrent of hematite photoanodes. Among the cathodic co-catalysts, NiMo demonstrated the best performance when combined with CuO photocathodes. For both photoelectrodes, an optimal co-catalyst loading was identified, beyond which performance declined due to potential charge transfer limitations and light attenuation. These findings highlight the critical role of co-catalyst composition and loading in optimizing the efficiency of PEC systems based on earth-abundant materials, offering a pathway toward scalable and cost-effective hydrogen production. Full article

Microbiologically Influenced Corrosion (MIC) significantly endangers steel infrastructure, particularly in marine and buried environments, causing considerable economic and environmental damage. Sulphate-reducing bacteria (SRB) are primary supporters of MIC, accelerating iron corrosion through hydrogen sulfide production. Conventional mitigation strategies, including protective coatings and cathodic protection, often face challenges such as limited effectiveness against SRB and the aggressiveness of saltwater corrosion. This study explores a novel approach by directly introducing zinc oxide (ZnO) nanoparticles into the microbial medium to inhibit SRB activity and reduce MIC. Iron metal coupons were immersed in seawater under three conditions: control (seawater only), seawater with SRB, and SRB with ZnO nanoparticles. These coupons were used as electrodes in microbial fuel cells to obtain real-time voltage readings. At the same time, corrosion was evaluated using cyclic voltammetry (CV), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), mass loss, and pH measurements. Results demonstrate that ZnO nanoparticles significantly inhibited SRB growth, as confirmed by the antibiotic susceptibility test (ABST). It was revealed that the corrosion rate increased by 21.3% in the presence of SRB compared to the control, whereas the ZnO-added electrode showed a 21.7% reduction in corrosion rate relative to the control. SEM showed prominent corrosive products on SRB-exposed coupons. ZnO-added coupons exhibited a protective layer with grass-like whisker structures, and EDX results confirmed reduced sulfur and iron sulfide deposits, indicating suppressed SRB metabolic activity. ABST confirmed ZnO’s antimicrobial properties by producing clear inhibition zones. ZnO nanoparticles offer the dual benefits of antimicrobial activity and corrosion resistance by forming protective self-coatings and inhibiting microbial growth, making them a scalable and eco-friendly alternative to traditional corrosion inhibitors. This application can significantly extend the lifespan of iron structures, particularly in environments prone to microbial corrosion, demonstrating the potential of nanomaterials in combating microbiologically influenced corrosion (MIC). Full article

In concentrated solar power (CSP) systems, structural materials face severe corrosion challenges induced by molten chlorides, with the corrosion severity being highly dependent on the salt composition. This study systematically compares the corrosion behavior of two representative superalloys, Inconel 625 and SS321, in binary NaCl–KCl and ternary MgCl₂–NaCl–KCl molten salts at 700 °C. The corrosion products and microstructural features were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD), in combination with static exposure tests to elucidate the underlying mechanisms. The results show that in NaCl–KCl molten salts, both alloys primarily form Cr₂O₃ as the protective product. However, the corrosion scale of SS321 is porous, whereas Inconel 625 develops a dense NiCr₂O₄ inner layer, exhibiting superior corrosion resistance. In the MgCl₂–NaCl–KCl molten salt system, Cr₂O₃ is replaced by a dense MgO layer forms on Inconel 625, coupled with Mo surface enrichment, which significantly inhibits Cr depletion and leads to a notably reduced corrosion rate relative to the binary salt. In contrast, the transformation of Cr₂O₃ on SS321 into porous MgCr₂O₄ exacerbates intergranular corrosion, resulting in a substantial degradation of corrosion resistance. This study elucidates the distinct corrosion pathways and mechanisms of different alloys in binary and ternary chloride salts, providing important guidance for the selection of molten salt compositions and corrosion-resistant structural materials in CSP applications. Full article

The growing accumulation of non-biodegradable petrochemical plastics and increasing food waste present urgent environmental and public health challenges. This study addresses both issues by developing biodegradable food packaging films from agar and starch, enhanced with antimicrobial properties by incorporating silver nanoparticles. The innovation of this work is the synthesis of novel agar–starch–silver nanoparticle coatings, where the contained nanoparticles were produced via green methods using two agro-industrial by-products of Greek olive oil production—olive stone extract and olive mill wastewater—as reducing agents. The morphology of the novel coatings was confirmed using transmission electron microscopy combined with energy-dispersive X-ray spectroscopy, revealing nanoscale particles with variable sizes. Additional film characterization was performed through Fourier-transform infrared spectroscopy, scanning electron microscopy coupled with energy-dispersive spectroscopy, and surface profilometry. Infrared spectroscopy analysis suggested the presence of functional groups responsible for nanoparticle stabilization, while energy-dispersive X-ray spectroscopy revealed silver aggregation in both olive stone extract and olive mill wastewater-derived films. Profilometry showed that films with olive mill wastewater-based nanoparticles had a rougher surface than those synthesized from olive stone extract. Antibacterial efficacy was tested against Escherichia coli (Gram-negative) and Staphylococcus epidermidis (Gram-positive) using a spot-on-film assay with high (10⁶ CFU/film) and low (10³ CFU/film) bacterial loads. After 72 h of incubation at 4 °C, both film types showed strong antibacterial activity at high bacterial concentrations, demonstrating their potential for active food packaging. These findings highlight a promising approach to sustainable food packaging within the circular economy, utilizing agricultural waste to create biodegradable materials with effective antimicrobial functionality. Full article

We investigated the application of an adsorbent fabricated from satsuma mandarin peel biomass using coating with poly(glycidyl methacrylate) followed by sequential treatment with hydroxylamine and hydrochloric acid for the remediation of hexavalent chromium-polluted water. The adsorbent was characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). Batch adsorption experiments were conducted wherein initial solution pH, initial chromium concentration, contact time, and temperature were varied. The adsorption equilibrium experimental data were well simulated by the Langmuir and Jovanovic models, pointing toward the formation of a monolayer of adsorbed chromium ions. The total chromium adsorption capacity of the functionalized satsuma mandarin peel adsorbent reached 219.28 mg g⁻¹ at initial pH 1.4 and 60 °C, markedly higher than 110.23 mg g⁻¹ at 30 °C. Where Cr(VI) was the sole chromium oxidation state in the initial solutions synthesized from potassium dichromate, the presence of Cr(III) ions in the final solutions confirmed Cr(VI) reduction. The results of this study show that the functionalized satsuma mandarin peel biomass is a potential candidate for use in the removal of hexavalent chromium from aqueous solution through reduction-coupled adsorption. Full article

In this study, TiC_xO_y was produced by sintering in an argon atmosphere using carbon–thermal reduction with TiO₂ and graphite powder as the initial materials. The sintered TiC_xO_y was analyzed using X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. As the oxygen content increased, the grain color of the sintered TiC_xO_y gradually shifted from gray to reddish-brown. The structure of TiC_xO_y resembles that of a coral, with a uniform distribution of Ti, C, and O throughout the sample. Analysis using X-ray photoelectron spectroscopy reveals the presence of bivalent, trivalent, and tetravalent titanium. Utilizing General Structure Analysis System software (GSAS-II), the X-ray Diffraction data obtained were refined, revealing a gradual decrease in lattice parameters as the oxygen atom content increased. Furthermore, the conductivity and density of the single phase, determined through the four-probe method and the Archimedes method, respectively, exhibited an increase in tandem with the rise in C content. Full article

Gypsum mortar is widely used in structures of architectural heritage. However, due to the high solubility of gypsum in water, it is easily destroyed by water erosion in outdoor environments, leading to the instability or even failure of the ancient buildings constructed with it. To improve the water erosion resistance of gypsum mortar, the alcoholic solution of barium hydroxide was explored as the protective agent in this study. The method involves treating the gypsum mortar with the alcoholic solution of barium hydroxide and water in sequence. The mechanism of its action and protective properties were studied by infrared spectroscopy, X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, conductivity meter, colorimeter, etc., and conclusions were made that the alcoholic solution of barium hydroxide has high permeability and its subsequent conversion to insoluble barium sulfate and calcium carbonate helps to increase the water erosion resistance of the solution. Additionally, the positive results such as the increase in mechanical strength from 20.80 HD to 60.94 HD, the reduction in water absorption from 18.37% to 15.75%, and a total color difference (ΔE*) of less than 3.0 indicated the application prospects of the proposed method in the conservation of the historical buildings made from gypsum mortar. Full article

Accelerated artificial aging of zinc oxide (ZnO)-based acrylic artists’ paint, filled with calcium carbonate (CaCO₃) as an extender, was carried out for a total of 1963 h (~8 × 10⁷ lux·h), with assessments at specific intervals. The total color difference ΔE* was <2 (CIELab-76 system) over 1725 h of aging, while the human eye notices color change at ΔE* > 2. Oxidative degradation of organic components in the paint to form volatile products was revealed by attenuated total reflectance–Fourier transform infrared (ATR-FTIR) spectroscopy, micro-Raman spectroscopy, and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS). It appears that deep oxidation of organic intermediates and volatilization of organic matter may be responsible for the relatively small value of ΔE* color difference during aging of the samples. To elucidate the degradation pathways, principal component analysis (PCA) was applied to the spectral data, revealing: (1) the catalytic role of ZnO in accelerating photodegradation, (2) the Kolbe photoreaction, (3) the decomposition of the binder to form volatile degradation products, and (4) the relative photoinactivity of CaCO₃ compared with ZnO, showing slower degradation in areas with a higher CaCO₃ content compared with those dominated by ZnO. These results provide fundamental insights into formulation-specific degradation processes, offering practical guidance for the development of more durable artist paints and conservation strategies for acrylic artworks. Full article

This study examines the pigments and materials used in Girolamo Romanino’s Musicians fresco (1537–1538), located in the Duomo Vecchio in Brescia, with the aim of identifying and analyzing the artist’s colour palette. Ten samples of the pictorial layer and mortar were collected from two frescoes and characterized using microscopic and spectroscopic techniques. Confocal laser scanning microscopy (CLSM) was used to define the best positions where single-point, spectroscopic techniques could be applied. Raman spectroscopy and micro-Fourier transform Infrared spectroscopy (micro-FTIR) were used to detect pigments and organic binders, respectively. X-ray powder diffraction (XRPD) provided additional insights into the mineral composition of the pigmenting layers, in combination with environmental scanning electron microscopy equipped with energy-dispersive spectroscopy (ESEM-EDS). The analysis revealed the use of traditional fresco pigments, including calcite, carbon black, ochres, and copper-based pigments. Smalt, manganese earths, and gold were also identified, reflecting Romanino’s approach to colour and material selection. Additionally, the detection of modern pigments such as titanium white and baryte points to restoration interventions, shedding light on the fresco’s conservation history. This research provides one of the most comprehensive analyses of pigments in Romanino’s works, contributing to a deeper understanding of his artistic practices and contemporary fresco techniques. Full article

This article presents studies of surface layers produced by electro-spark deposition (ESD) on cast iron using a W-Ni-Co sintered electrode. To minimize the number of required experiments, a two-factor, five-level Hartley experimental design was chosen. The assessment involved observing the effect of voltage and capacitor capacity during the ESD process (on layer thickness and wear of the sample and counter-sample under technically dry friction conditions). Microscopic and tomographic observations were performed to analyze the thickness and structure of the layers. Image analysis methods were employed to examine the cross-section of the layers. ESD diffusion analyses were performed on the produced layer. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were performed to characterize the microstructure and composition of the coating. In addition, in order to evaluate the performance properties of tungsten coatings, the tribological tests were also conducted on a TRB³ Ball-on-Disc testing device. Hardness tests confirm an increase in the hardness of cast iron with a tungsten layer by over 400 µHV. The tests showed that higher voltages during the ESD process result in thicker layers and reduced wear of the sample with a tungsten layer at the expense of increased wear of the counter-sample (ball). Full article

Humidity sensing elements based on sodium-doped titanium dioxide (Na-doped TiO₂) were prepared using a sol–gel method in the presence of cerium ions and sintered at 400 °C and 800 °C. Titanium (IV) n-butoxide and a saturated solution of diammonium hexanitratocerate in isobutanol served as starting materials. Sodium hydroxide and sodium tert-butoxide were used as inorganic and organometallic sodium sources, respectively. The influence of sodium additives on the properties of the humidity sensing elements was systematically investigated. The surface morphologies of the obtained layers were examined by scanning electron microscopy (SEM). Elemental mapping was conducted by energy-dispersive X-ray (EDX) spectroscopy, and structural characterization was performed using X-ray diffractometry (XRD). Electrical properties were studied for samples sintered at different temperatures over a relative humidity range of 15% to 95% at 20 Hz and 25 °C. Experimental results indicate that sodium doping enhances humidity sensitivity compared to undoped reference samples. Incorporation of sodium additives increases the resistance variation range of the sensing elements, reaching over five orders of magnitude for samples sintered at 400 °C and four orders of magnitude for those sintered at 800 °C. Full article

Titanium and its alloys are widely used in biomedical implants due to their favorable mechanical properties and corrosion resistance; however, their natural surface lacks sufficient bioactivity and antibacterial performance. Micro-arc oxidation is a promising approach to producing bioactive coatings, and the incorporation of nanoparticles such as TiO₂ may further improve their functionality. This study aimed to determine the optimal TiO₂ nanoparticle concentration in the micro-arc oxidation electrolyte that ensures coating stability and biological safety. Calcium–phosphate coatings were fabricated on commercially pure titanium using micro-arc oxidation with two TiO₂ concentrations: 0.5 wt.% (MAO 1) and 1 wt.% (MAO 2). Surface morphology, porosity, and phase composition were analyzed by scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction. Corrosion resistance was evaluated via potentiodynamic polarization in NaCl and Ringer’s solutions, while biocompatibility was assessed in vitro using HOS human osteosarcoma cells and MTT assays. Increasing the TiO₂ content to 1% decreased coating porosity (13.7% vs. 26.3% for MAO 1), enhanced corrosion protection, and reduced the friction coefficient compared to bare titanium. However, MAO 2 exhibited high cytotoxicity (81% cell death) and partial structural degradation in the biological medium. MAO 1 maintained integrity and showed no toxic effects (3% cell death). These results suggest that 0.5% TiO₂ is the optimal concentration, providing a balance between corrosion resistance, mechanical stability, and biocompatibility, supporting the development of safer implant coatings. Full article

In this work, the removal of Cu(II) ions from an aqueous effluent was studied using an Mg/Fe layered double hydroxide (LDH) as the adsorbent. The material was synthesized and characterized before and after the adsorption process to identify structural and morphological changes induced by copper uptake. Techniques such as X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), ultraviolet-visible spectroscopy (UV-Vis), Raman spectroscopy, and nitrogen physisorption (BET) were employed to confirm the interaction between the metal ions and the LDH surface. The LDH-Mg/Fe exhibited a high maximum adsorption capacity of 526 mg/g, and the adsorption kinetics followed a pseudo-second-order model, achieving over 90% removal of Cu(II) within 2.5 h. The Cu(II)-loaded material was subsequently evaluated as a sustainable catalyst in two applications: (i) an organic synthesis via “click” chemistry, reaching yields of up to 85%, and (ii) the decoloration of Congo Red via a Fenton-like process, achieving a decoloration efficiency of at least 84%. These dual uses demonstrate the potential of Cu(II)-loaded LDH as a cost-effective and environmentally friendly approach to simultaneous pollutant removal and catalytic valorization. Full article