Search Results (99)

Rouaite (Cu₂(OH)₃NO₃) long hexagonal multilayered nanoplates with high purity and high crystallinity were prepared from acidic reaction solution (pH = 4.4–4.8) with the assistance of ZnO. The ZnO-assisted strategy is remarkably different from the conventional synthetic protocol that was regularly carried out in alkaline solution (pH > 11). The rouaite multilayer nanoplates displayed exceptionally high catalytic activity in the catalytic wet peroxide oxidation (CWPO) of Congo red (CR). The catalytic efficiency for CR decolorization achieved an impressive 96.3% in 50 min under near-neutral (pH = 6.76) and ambient conditions (T = 20 °C, p = 1 atm), without increasing the temperature and/or decreasing the pH value to acidic region (pH = 2–3) as is commonly employed in CWPO process for improved degradation efficiency. Full article

Five requeijão samples, classified as Brazilian cream cheeses, were developed: one control (without guabiroba pulp (Campomanesia xanthocarpa O. Berg) and four with 5, 10, 15, and 20% (m/m) guabiroba pulp. They were evaluated for pH, water activity (aw), color, texture, multi-mineral composition, carotenoid content, and microstructure. The addition of guabiroba pulp reduced pH and maintained Aw. The samples with 5%, 10%, 15%, and 20% guabiroba pulp presented a yellow–reddish coloration. The formulation with 5% had the lowest values of firmness, resilience, texture, and spreadability. From 10% onwards, an increase in cohesiveness and a reduction in creaminess were observed. The sample with 15% presented better spreadability, while the 20% sample had adhesiveness similar to the control. No traces of Al, As, Cd, Co, Cr, Cu, Fe, Mn, Pb, or Se were detected. The detected elements, in descending order, were Na, Ca, P, S, K, Mg, Sr, and Zn. β-carotene was predominant, with guabiroba pulp enhancing α-carotene, β-carotene, β-cryptoxanthin, and λ-carotene levels, especially at 20% pulp. Microstructure analysis by scanning electron microscopy (SEM) showed no significant differences. These findings highlight the potential of guabiroba pulp as a functional ingredient in requeijão, enhancing its carotenoid profile while maintaining desirable textural and physicochemical properties. Full article

Hydrogel-based adsorbents have gained increasing recognition in recent years due to their promising potential for pollutant removal. However, conventional hydrogels often suffer from low mechanical strength over prolonged use. Therefore, this study explores the incorporation of silica extracted from bamboo culm (Dendrocalamus asper) to enhance the mechanical stability of hydrogel beads composed from carboxymethyl cellulose (CMC), chitosan (CS), and magnetite ferrofluid (Fe₃O₄), through cross-linking. We hypothesize that silica enhances the mechanical properties of magnetite hydrogel beads without compromising their adsorption capacity. The extracted silica was confirmed with FTIR and EDS analysis. The synthesized CMC-CS-Fe₃O₄-Si hydrogel beads were characterized using FTIR and SEM. Its stability was assessed through dry weight loss measurements, while its adsorption efficiency was evaluated using batch adsorption experiments. The silica-incorporated hydrogel exhibited enhanced mechanical and thermal stability under various pH and temperature conditions, without negatively affecting its adsorption performance, achieving maximum adsorption capacities of 53.00 mg/g for Cr (VI) and 85.06 mg/g for Cu (II). Desorption and regeneration studies confirmed the reusability of the hydrogel for more than four cycles. Overall, the interaction between the hydrogel and silica resulted in excellent adsorption performance, improved mechanical properties, and long-term reusability, making this a promising hydrogel adsorbent for wastewater remediation. Full article

Copper oxide nanoparticles (CuO-NPs) induce neurological diseases, including neurobehavioral defects and neurodegenerative diseases. Direct evidence indicates that CuO-NPs induce inflammation in the central nervous system and cause severe neurotoxicity. However, the mechanism of CuO-NP-induced damage to the nervous system has rarely been studied, and the toxicity of different CuO-NP particle sizes and their copper ion (Cu²⁺) precipitation in microglia (BV2 cells) is worth exploring. Therefore, this study investigated CuO-NPs with different particle sizes (small particle size: S-CuO-NPs; large particle size: L-CuO-NPs), Cu²⁺ with equal molar mass (replaced by CuCl₂ [Equ group]), and Cu²⁺ precipitated in a cell culture solution with CuO-NPs (replaced by CuCl₂ [Pre group]), and examined the mechanism of action of each on BV2 microglia after co-culture for 12 h and 24 h. The activity of BV2 cells decreased, the morphology was damaged, and the apoptosis rate increased in all the exposed groups. Toxicity increased time- and dose-dependently, and was highest in the Equ group, followed by the S-CuO-NPs, L-CuO-NPs, and Pre groups, respectively. Subsequently, we investigated the mechanism of S-CuO-NP-induced cell injury, and revealed that S-CuO-NPs induced oxidative stress and inflammatory response and increased the membrane permeability of BV2 cells. Moreover, S-CuO-NPs reduced the ratio of p-CSF-1R/CSF-1R, p-PLCγ2/PLCγ2, p-extracellular signal-regulated kinase (ERK)/ERK, p-Nrf2/Nrf2, and Bcl-2/Bax protein expression in microglia, and elevated cleaved caspase-3 expression. The CSF-1R/PLCγ2/ERK/Nrf2 apoptotic pathway was activated. The downregulation of CX3CR1, CSF-1R, brain-derived neurotrophic factor (BDNF), and IGF-1 protein expression indicates impairment of the repair and protection functions of microglia in the nervous system. In summary, our results reveal that CuO-NPs promote an increase in inflammatory molecules in BV2 microglia through oxidative stress, activate the CSF-1R/PLCγ2/ERK/Nrf2 pathway, cause apoptosis, and ultimately result in neurofunctional damage to microglia. Full article

The circular economy practice of using waste to fertilize plants should be more widespread. It is a means to manage natural resources sustainably in agriculture. This approach is in line with organic and sustainable farming strategies, reducing the cultivation costs. Organic waste dumped into a landfill decomposes and emits greenhouse gases. This can be reduced through its application to energy crops, which not only has a positive impact on the environment but also improves the soil quality and increases yields. However, organic waste with increased content of heavy metals, when applied to the soil, can also pose a threat. Using Miscanthus × giganteus M 19 as a test plant, an experiment with a randomized block design was established in four replications in Central–Eastern Poland in 2018. Various combinations of organic waste (municipal sewage sludge and spent mushroom substrate) were applied, with each dose containing 170 kg N ha⁻¹. After three years (in 2020), the soil content of total nitrogen (N_t) and carbon (C_t) was determined by elemental analysis, with the total content of P, K, Ca, Mg, S, Na, Fe, Mn, Mo, Zn, Ni, Pb, Cr, Cd, and Cu determined by optical emission spectrometry, after wet mineralization with aqua regia. For the available forms of P and K, the Egner–Riehm method was used, and the Schachtschabel method was used for the available forms of Mg. The total content of bacteria, actinomycetes, and fungi was also measured. The application of municipal sewage sludge (SS) alone and together with spent mushroom substrate (SMS) improved the microbiological composition of the soil and increased the content of N_t and C_t and the available forms of P₂O₅ and Mg more than the application of SMS alone. SMS did not contaminate the soil with heavy metals. In the third year, their content was higher after SS than after SMS application, namely for Cd by 12.2%, Pb by 18.7%, Cr by 25.3%, Zn by 16.9%, and Ni by 14.7%. Full article

This study deals with the reconstruction of the paleoenvironment and the paleoclimate situation of the middle–upper Eocene sediments in the northwest Fayum area. The reconstruction is based on comprehensive stratigraphical and geochemical analyses of major oxides and trace elements for selected sediment samples from the Gehannam Formation (Bartonian–Priabonian), the Birket Qarun and the Qasr El Sagha formations (Priabonian). The sedimentological features coupled with paleo-redox trace elemental ratios (Ni/Co, V/Cr, U/Th, V/(V + Ni), and Cu/Zn), paleosalinity (Sr/Ba, Mg/Al ×100, Ca/Al), and paleowater depth (Fe/Mn) proxies, indicate that deposition took place in a shallow marine agitated environment with high oxygen levels. Paleoclimate indicators (Sr/Cu, Rb/Sr, K₂O₃/Al₂O₃, Ga/Rb, C-value, CIA, and CIW) suggest warm and prevailing arid climatic conditions, with minor humid periods at some intervals. The observed low values of the total organic carbon (TOC) are attributed to significant high sediment influx, predominant oxygenated conditions, and poor primary productivity, which is further confirmed by low values of paleoprimary productivity proxies (P, Ni/Al, Cu/Al, P/Al and P/Ti, and Ba_bio ratios). These findings enhance our understanding of the Eocene environments and provide insights into sedimentation processes during this period. Full article

The multielement pyrochlore of the composition Bi_1.57Mn_1/3Cr_1/3Cu_1/3Nb₂O_9−Δ (sp. gr. Fd-3m:2, 10.4724 Å) containing transition element atoms—chromium, manganese and copper in equimolar amounts—was synthesized for the first time using the solid-phase reaction method. The microstructure of the ceramics is grainless and has low porosity. The sample is characterized by reflection in the red (705 nm) color region. The band gap for the direct allowed transition in the sample is 1.68 eV. The parameters of the Bi5d, Nb3d, Сr2p, Mn2p, and Cu2p X-ray photoelectron spectroscopy (XPS) spectra for the mixed pyrochlore are compared with the parameters of transition element oxides. For the complex pyrochlore, a characteristic shift in the Bi4f and Nb3d spectra to the region of lower energies by 0.15 and 0.60 eV, respectively, is observed. According to the XPS Cu2p and Mn2p spectra of pyrochlore, copper, and manganese cations are in a mixed charge state; they mainly have an effective charge of +2/+3, and the Cr2p spectrum is a superposition of the spectra of chromium ions in the charge state of +3, +4, +6. At 24 °С, the permittivity of the sample in the frequency range (10⁴–10⁶ Hz) weakly depends on the frequency and is equal to ~100, the dielectric loss tangent is 0.017. The activation energy of conductivity is equal to 0.41 eV. The specific electrical conductivity of Bi_1.57Cr_1/3Cu_1/3Mn_1/3Nb₂O_9−Δ increases with the temperature increasing from 1.8 × 10⁻⁵ Ohm⁻¹·m⁻¹ (24 °С) to 0.1 Ohm⁻¹·m⁻¹ (330 °С). Nyquist curves for the sample are modeled by equivalent electrical circuits. Full article

The development of photoelectrochemical tandem cells for water splitting with electrodes entirely based on metal oxides is hindered by the scarcity of stable p-type oxides and the poor stability of oxides in strongly alkaline and, particularly, strongly acidic electrolytes. As a novelty in the context of transition metal oxide photoelectrochemistry, a bias-free tandem cell driven by simulated sunlight and based on a CuCrO₂ photocathode and a WO₃ photoanode, both unprotected and free of co-catalysts, is demonstrated to split water while working with strongly acidic electrolytes. Importantly, the Faradaic efficiency for H₂ evolution for the CuCrO₂ electrode is found to be about 90%, among the highest for oxide photoelectrodes in the absence of co-catalysts. The tandem cell shows no apparent degradation in short-to-medium-term experiments. The prospects of using a practical cell based on this configuration are discussed, with an emphasis on the importance of modifying the materials for enhancing light absorption. Full article

Doping engineering is crucial for both fundamental science and emerging applications. While transition metal (TM) dopants exhibit considerable advantages in the tuning of magnetism and conductivity in bulk Ga₂O₃, investigations on TM-doped two-dimensional (2D) Ga₂O₃ are scarce, both theoretically and experimentally. In this study, the detailed variations in impurity levels within 3d TM-doped 2D Ga₂O₃ systems have been explored via first-principles calculations using the generalized gradient approximation (GGA) +U method. Our results show that the Co impurity tends to incorporate on the tetrahedral GaII site, while the other dopants favor square pyramidal GaI sites in 2D Ga₂O₃. Moreover, Sc³⁺, Ti⁴⁺, V⁴⁺, Cr³⁺, Mn³⁺, Fe³⁺, Co³⁺, Ni³⁺, Cu²⁺, and Zn²⁺ are the energetically favorable charge states. Importantly, a transition from n-type to p-type conductivity occurs at the threshold Cu element as determined by the defect formation energies and partial density of states (PDOS), which can be ascribed to the shift from electron doping to hole doping with respect to the increase in the atomic number in the 3d TM group. Moreover, the spin configurations in the presence of the square pyramidal and tetrahedral coordinated crystal field effects are investigated in detail, and a transition from high-spin to low-spin arrangement is observed. As the atomic number of the 3d TM dopant increases, the percentage contribution of O ions to the total magnetic moment significantly increases due to the electronegativity effect. Additionally, the formed 3d bands for most TM dopants are located near the Fermi level, which can be of significant benefit to the transformation of the absorbing region from ultraviolet to visible/infrared light. Our results provide theoretical guidance for designing 2D Ga₂O₃ towards optoelectronic and spintronic applications. Full article

Cu-based ternary oxides with delafossite structure have received considerable attention in recent years for their versatility in a wide range of applications, among which is the possibility to use them in heterostructure solar cells as hole transport layers, due to their promising behavior as p-type conducting oxides. Ab initio calculations have been performed with density functional theory to investigate the role of the trivalent metal within the CuMO₂ structure and the dependence of structural and electronic properties with the species (M = Al, Ga, In, Fe, Cr, Co, Sc, Y) occupying the site of the metal. Generalized Gradient Approximation also including a Hubbard term and nonlocal Heyd–Scuseria–Enzerhof screened hybrid functional schemes were tested and their results were compared. Excellent agreement with experimental lattice parameters and measured gaps have been found. The use of hybrid functionals in HSE approximation considerably improves the bandgaps when compared with the experimental results but takes considerable time to converge, hence the need to explore less demanding methodologies. Trends in the geometry as well as in the electronic properties are discussed, and the effect of mixing different metals (CuM_xN_1−xO₂, M, N being the aforementioned elements) in the geometry and electronic properties of these delafossite materials is investigated. Due to the high cost of HSE calculations, especially when supercells are needed to model several x concentrations, statistical models and techniques based on machine learning have also been explored to predict HSE bandgap values from GGA and structural information. Full article

As long-living apex predators, sharks tend to bioaccumulate trace metals through their diet. The distribution of Al, As, Cd, Co, Cr, Cs, Cu, Fe, Mn, Ni, Pb, V, Zn and Hg in different tissues (muscle, liver, heart, gills and gonads) of large-size (58–390 cm) sharks, some of which rare, of the eastern Mediterranean Sea was studied. Trace metals analyses in samples originating from ten different Chondrichthyes species were performed by inductively coupled plasma–mass spectrometry (ICP-MS) and Cold Vapor Atomic Absorption Spectrometry (CVAAS) for Hg. Data on trace metal levels are for the first time reported herewith for the species O. ferox and H. nakamurai. Higher median concentrations of trace metals were generally determined in the liver. The concentrations of Hg, Cs and As in the muscle increased proportionally with body length. Statistically significant differences between sexes were recorded for Hg, Cr, Ni and As (p = 0.015) in the muscle tissues of P. glauca. Muscle tissue Hg concentrations exceeded the EU maximum limit (1 μg g⁻¹ wet weight) in 67% of the individuals sampled, with the highest concentrations detected in O. ferox and S. zygaena, whereas regarding Pb (limit 0.30 μg g⁻¹ ww), the corresponding percentage was 15%. Arsenic concentrations were also of concern in almost all shark tissues examined. Full article

The Upper Silesian Coal Basin (USCB), located in southern Poland, is the major coal basin in Poland, and all technological types of hard coal, including coking coal, are exploited. It is also an area of high potential for coal-bed methane (CBM). Despite the increasing availability of alternative energy sources globally, it is a fact that the use of fossil fuels will remain necessary for the next few decades. Therefore, research on coal-bearing formations using modern research methods is still very important. The application of geochemistry and chemostratigraphy in reservoir characterization has become increasingly common in recent years. This paper presents the possibility of applying chemostratigraphic techniques to the study of the Carboniferous coal-bearing succession of the Upper Silesian Coal Basin. The material studied comes from 121 core samples (depth 481–1298 m), representing the Mudstone Series (Westphalian A, B). Major oxide concentrations of Al₂O₃, SiO₂, Fe₂O₃, P₂O₅, K₂O, MgO, CaO, Na₂O, K₂O, MnO, TiO₂, and Cr₂O₃ were obtained using X-ray fluorescence (XRF) spectrometry. Trace elements were analyzed using inductively coupled plasma mass spectrometry (ICP/MS). The geochemical record from the Mudstone Series shows changes in the concentration of major elements and selected trace elements, leading to the identification of four chemostratigraphic units. These units differ primarily in the content of Fe, Ca, Mg, Mn, and P as well as the concentration of Zr, Hf, Nb, Ta, and Ti. The study also discusses quartz origin (based on SiO₂ and TiO₂), sediment provenance and source-area rock compositions (based on Al₂O₃/ TiO₂, TiO₂/Zr, and La/Th), and paleoredox conditions (based on V/Cr, Ni/Co, U/Th, (Cu+Mo)/Zn, and Sr/Ba) for the chemostratigraphic units. Chemostratigraphy was used for the first time in the study of the Carboniferous coal-bearing series of the USCB, concluding that it can be used as an effective stratigraphic tool and provide new information on the possibility of correlating barren sequences of the coal-bearing succession. Full article

In the present investigation of copper ferrite, a CuFe₂O₄ nanocomposite adsorbent was synthesized using the sol–gel method, and its relevance in the adsorptive elimination of the toxic Congo red (CR) aqueous phase was examined. A variety of structural methods were used to analyze the CuFe₂O₄ nanocomposite; the as-synthesized nanocomposite had agglomerated clusters with a porous, irregular, rough surface that could be seen using FE-SEM, and it also contained carbon (23.47%), oxygen (44.31%), copper (10.21%), and iron (22.01%) in its elemental composition by weight. Experiments were designed to achieve the most optimized system through the utilization of a central composite design (CCD). The highest uptake of CR dye at equilibrium occurred when the initial pH value was 5.5, the adsorbate concentration was 125 mg/L, and the adsorbent dosage was 3.5 g/L. Kinetic studies were conducted, and they showed that the adsorption process followed a pseudo-second-order (PSO) model (regression coefficient, R² = 0.9998), suggesting a chemisorption mechanism, and the overall reaction rate was governed by both the film and pore diffusion of adsorbate molecules. The process through which dye molecules were taken up onto the particle surface revealed interactions involving electrostatic forces, hydrogen bonding, and pore filling. According to isotherm studies, the equilibrium data exhibited strong agreement with the Langmuir model (R² = 0.9989), demonstrating a maximum monolayer adsorption capacity (q_max) of 64.72 mg/g at pH 6 and 302 K. Considering the obtained negative ΔG and positive ΔH_ads and ΔS_ads values across all tested temperatures in the thermodynamic investigations, it was confirmed that the adsorption process was characterized as endothermic, spontaneous, and feasible, with an increased level of randomness. The CuFe₂O₄ adsorbent developed in this study is anticipated to find extensive application in effluent treatment, owing to its excellent reusability and remarkable capability to effectively remove CR in comparison to other adsorbents. Full article

This study assesses the water quality of the Sušanecké Ponds in the Czech Republic post-mining area. Four monitoring profiles were chosen: the Sušanka River inflow into the Sušanecké Ponds, two ponds and the outflow of the Sušanecké Ponds to the Sušanka River. The sampling took place in a 14-day interval from March to October 2022. The monitored parameters were temperature, O₂, pH, electrical conductivity, turbidity, nitrate nitrogen, ammoniacal nitrogen, total phosphorus, chlorophyll-a, COD_Cr, BOD₅ and metals—Fe, Mn, Cu, Zn, Ni, Pb, Co, Cd, Cr. The results were evaluated in accordance with the Czech standard ČSN 75 7221 and Government Regulation No. 401/2015 Coll. Based on the evaluation data, it was found that the area of the Sušanecké Ponds does not meet the limits of the government regulation for three out of the twenty parameters. According to the standard, Sušanecké Ponds are mainly classified as highly polluted waters. Full article

Superparamagnetic magnetic nanoparticles (MNPs, Fe₃O₄) were first synthesized based on a chemical co–precipitation method, and the core–shell magnetic silica nanoparticles (MSNPs, Fe₃O₄@SiO₂) were obtained via hydrolysis and the condensation of tetraethyl orthosilicate onto Fe₃O₄ seed using a sol–gel process. Following that, MSNPs were immobilized using a three–step grafting strategy, where 8-hloroacetyl–aminoquinoline (CAAQ) was employed as a metal ion affinity ligand for trapping specific heavy metal ions, and a macromolecular polymer (polyethylenimine (PEI)) was selected as a bridge between the surface hydroxyl group and CAAQ to fabricate a network of organic networks onto the MSNPs’ surface. The as–synthesized MSNPs–CAAQ nanocomposites possessed abundant active functional groups and thus contained excellent removal features for heavy metal ions. Specifically, the maximum adsorption capacities at room temperature and without adjusting pH were 324.7, 306.8, and 293.3 mg/g for Fe³⁺, Cu²⁺, and Cr³⁺ ions, respectively, according to Langmuir linear fitting. The adsorption–desorption experiment results indicated that Na₂EDTA proved to be more suitable as a desorbing agent for Cr³⁺ desorption on the MSNPs–CAAQ surface than HCl and HNO₃. MSNPs–CAAQ exhibited a satisfactory adsorption capacity toward Cr³⁺ ions even after six consecutive adsorption–desorption cycles; the adsorption efficiency for Cr³⁺ ions was still 88.8% with 0.1 mol/L Na₂EDTA as the desorbing agent. Furthermore, the MSNPs–CAAQ nanosorbent displayed a strong magnetic response with a saturated magnetization of 24.0 emu/g, and they could be easily separated from the aqueous medium under the attraction of a magnet, which could facilitate the sustainable removal of Cr³⁺ ions in practical applications. Full article