Search Results (668)

As one of the world’s most widely used packaging materials, paper obtains its properties from its major component: wood. Variations in the species of wood result in variations in the paper’s mechanical properties. The pulp and paper production industry is known to be a polluting industry and a consumer of a large amount of energy but remains an essential heavy industry globally. Paper production, based largely on the kraft process, is mainly intended for the food packaging sector and, thus, is associated with contamination risks. The lack of standardized regulations and the different analytical techniques used make information on the subject complex, particularly for inorganic elements where little information is available in the literature. Most research in this field is based on sample preparation using mineralization via acid digestion to obtain a liquid and homogeneous matrix, mainly with a HNO₃/H₂O₂ mixture. The most commonly used techniques are Atomic Absorption Spectrometry (AAS), Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES), and Inductively Coupled Plasma Mass Spectrometry (ICP-MS), each with its advantages and disadvantages, which complicates the use of these tech-niques for routine analyses on an industrial site. In the same field of inorganic compound analysis, Microwave Plasma Atomic Emission Spectrometry (MP-AES) has become a real alternative to techniques such as AAS or ICP-AES. This technique has been used in several studies in the food and environmental fields. This publication aims to examine, for the first time, the state of the art regarding the analysis of inorganic elements in food packaging and different matrices using MP-AES. The entire manufacturing process is studied to identify possible sources of inorganic contaminants. Various analytical techniques used in the field are also presented, as well as research conducted with MP-AES to highlight the potential benefits of this technique in the field. Full article

SARS-CoV-2 variants have demonstrated distinct epidemiological patterns and clinical presentations throughout the COVID-19 pandemic. Understanding variant-specific differences at the respiratory epithelium is crucial for understanding their pathogenesis. Here, we utilized human nasal organoid air–liquid interface (HNO-ALI) cell cultures to compare the viral replication kinetics, innate immune response, and epithelial damage of six different strains of SARS-CoV-2 (B.1.2, WA, Alpha, Beta, Delta, and Omicron). All variants replicated efficiently in HNO-ALIs, but with distinct replication kinetic patterns. The Delta variant exhibited delayed replication kinetics, achieving a steady state at 6 days post-infection compared to 3 days for other variants. Cytokine analysis revealed robust pro-inflammatory and chemoattractant responses (IL-6, IL-8, IP-10, CXCL9, and CXCL11) in WA1, Alpha, Beta, and Omicron infections, while Delta significantly dampened the innate immune response, with no significant induction of IL-6, IP-10, CXCL9, or CXCL11. Immunofluorescence and H&E analysis showed that all variants caused significant ciliary damage, though WA1 and Delta demonstrated less destruction at early time points (3 days post-infection). Together, these data show that, in our HNO-ALI model, the Delta variant employs a distinct “stealth” strategy characterized by delayed replication kinetics and epithelial cell innate immune evasion when compared to other variants of SARS-CoV-2, potentially explaining a mechanism that the Delta variant can use for its enhanced transmissibility and virulence observed clinically. Our findings demonstrate that variant-specific differences at the respiratory epithelium could explain some of the distinct clinical presentations and highlight the utility of the HNO-ALI system for the rapid assessment of emerging variants. Full article

Catalytic methane decomposition (CMD) is an environmentally friendly method of hydrogen production that, unlike other conventional processes, such as steam methane reforming, partial oxidation of methane, and dry reforming of methane, can convert methane into hydrogen with a simultaneous generation of solid carbon without CO₂ emissions. This study mainly focused on the application of carbon-based catalysts derived from biomass and biowaste for the CMD process. For this purpose, eight catalysts were produced from three carbon materials (wood, sewage sludge, and digestate) through the subsequent processes of pyrolysis, leaching, and physical activation. The comparison of catalysts prepared from the slow pyrolysis of biowaste and wood indicated that carbon materials with a lower ash content achieved a higher initial methane conversion (wood char > digestate char > sewage sludge char). For feedstocks with a high initial ash content, such as digestate and sewage sludge chars, an improvement in the catalytic activity was observed after ash removal through the leaching process with HNO₃. In addition, physical activation through CO₂ fluxing led to an enhancement in the BET surface area of these catalysts, and consequently to a growth in methane conversion. The initial methane conversion was assessed for all chars under operating conditions of 900 °C, a gas hourly space velocity (GHSV) of 3 L/g/h, and a CH₄:N₂ ratio of 1:9, and it was 65.9, 59.1, and 42.6% v/v, respectively, for chars derived from wood, sewage sludge, and digestate; these values increased to almost 80% v/v when these chars were upgraded by chemical leaching and physical activation. Full article

Rare earth elements (REEs) have significant application value in the quality control of nuclear materials and in traceability research in nuclear forensics. Methods were developed for the determination of REEs in uranium-bearing nuclear materials. The digestion parameters for uranium oxides and uranium ores, such as the digestion acid, digestion temperature, and digestion time, were optimized and reported. The optimized digestion parameters for uranium oxides were 2 mL HNO₃ at 160 °C for 3 h, and those for uranium ores were 7 mL mixed acid (HNO₃–HClO₄–HF = 5:5:3) at 180 °C for 36 h. Two digestion methods were demonstrated to be effective for the quantitative recovery of REEs. The suitable system and specifications for different resin columns were investigated to achieve a high decontamination factor of U (10⁵) by UTEVA resin. The corresponding loading system was 10 mL 4 M HNO₃, and the elution system was 6 mL 4 M HNO₃. Additionally, the analysis of ultra-trace REEs in high-uranium matrices was accomplished using two UTEVA resins. The developed methods were subjected to the Cochran test and the Grubbs test, and the relative standard deviation (RSD) for all REEs was below 6%. In uranium oxide samples with different spiked amounts, the recovery of REEs exceeded 80% in all cases, and the RSDs were all less than 10%. The method’s detection limits were below 10 ppt for all REEs (except for Ce), ensuring the accurate measurement of REEs in uranium-bearing nuclear materials. Full article

The stress corrosion cracking (SCC) susceptibility of 2195-T8 Al-Li alloy in N₂O₄ medium was evaluated using slow strain rate testing (SSRT). The electrochemical corrosion behavior and morphological evolution of the alloy under different conditions were further examined through potentiodynamic polarization measurements. The results indicate that with the increase in electrochemical corrosion rate, the corrosion morphology of the alloy extends from localized pitting and intergranular corrosion to severe exfoliation corrosion. In the N₂O₄ medium, the alloy exhibits significant susceptibility to SCC at tensile rates of ε ≥ 5 × 10⁻⁶ s⁻¹. However, when strained at ε = 10⁻⁶ s⁻¹, a sudden increase in I_SCC is observed accompanied by a transition to brittle intergranular fracture mediated by anodic dissolution. At the same stretch rate (ε = 10⁻⁶ s⁻¹), the susceptibility to SCC of the alloy in N₂O₄ medium increased with higher water content ω(H₂O). This trend is attributed to enhanced generation of HNO₃ and HNO₂, as well as increased diffusion of hydrogen—produced by the cathodic reaction—to the crack tip. The synergistic interaction between anodic dissolution and hydrogen embrittlement ultimately promotes the initiation and propagation of SCC in the alloy. Full article

The selective removal of impurities from molybdenite concentrates is crucial for producing high-purity molybdenum products. In this study, the purification of molybdenite concentrate was investigated using nitric acid as both a leaching medium and oxidizing agent. Leaching experiments were carried out under various conditions of temperature (22–78 °C) and nitric acid concentration (0.12–0.48 M). The results demonstrated that while molybdenite remained mostly undissolved, copper and iron were effectively leached, with near-complete removal at 78 °C in 0.24 M HNO₃ after 6 h. Compared with other acid systems, nitric acid leaching experiments in this study demonstrated higher efficiency and selectivity under relatively moderate conditions of concentration and temperature. Kinetic analyses were performed based on the shrinking core model (SCM) and extended by developing a comprehensive rate equation that incorporates both nitric acid concentration and reactive surface effects. Fitting the developed model to experimental data revealed distinct kinetic regimes below and above 50 °C, suggesting a mechanism shift from surface chemical reaction control to diffusion through an ash layer. The purified molybdenite was characterized by SEM-EDS and ICP-OES, confirming almost complete elimination of Cu and Fe impurities. This work highlights nitric acid as a promising and efficient medium for selective leaching of molybdenite concentrates and provides a comprehensive kinetic model applicable across different leaching conditions. Full article

To reduce energy consumption in buildings and to maintain comfortable conditions, lighting equipment that includes light-emitting diode (LED) lamps and lighting management equipment is utilised. In this study, integrated circuits detached from lighting equipment were characterised for the presence of precious metals (silver, gold, palladium, and platinum). Their digestion was carried out with HNO₃ and aqua regia solution on a hot plate and characterised using inductively coupled plasma optical emission spectroscopy (ICP-OES). The concentration of each element as a function of the type and origin of the integrated circuits varied as follows: silver, 652–3876 mg/kg; gold, 0–993 mg/kg; palladium, 0–74 mg/kg; and platinum was detected at a concentration below the quantification limit. These results indicate the need for selective removal and separate recycling processes for integrated circuits from the lighting equipment. Full article

Natural clinoptilolite from the Shankhanai deposit (Kazakhstan) was modified via acid and thermal treatments to improve its physicochemical and catalytic properties. The zeolite was activated using 10% nitric acid alone, nitric acid followed by thermal treatment (600 °C), and a mixed acid solution (10% HNO₃ + 5% CH₃COOH) followed by mild thermal treatment (280 °C). Structural, textural, and thermal changes were characterized by XRD, FTIR, BET, TGA, SEM, and EDX. Nitric acid treatment increased the BET surface area from 4.95 to 59.9 m²/g but reduced crystallinity, whereas the dual-acid approach enhanced porosity and acidity while preserving framework integrity. Preliminary catalytic testing in thiophene hydrodesulfurization (HDS) revealed improved conversion (up to 20.7%) in the absence of active metals, confirming the potential of modified clinoptilolite as a catalyst support. The dual-acid method presents a promising, eco-friendly pathway for producing thermally stable and catalytically active zeolitic materials, suitable for selective hydrodesulfurization of thiophene. Full article

This study investigates the atmospheric formation and sinks of HONO and HNO₃ and their contribution to secondary PM_2.5 formation in Daejeon (urban) and Iksan (suburban), South Korea. Continuous observations revealed distinct concentration patterns: Iksan exhibited elevated ammonia and nitrate levels associated with agricultural activities and biomass burning, while Daejeon showed higher NOx concentrations driven by traffic and industrial sources. Positive Matrix Factorization (PMF) analysis indicated that secondary formation was the dominant contributor to PM_2.5 at both sites, with biomass burning exerting an additional influence in Iksan. Among observed precursors, HNO₃ showed the highest conversion to aerosol nitrate, highlighting aerosol-phase reactions as its primary sink, followed by dry deposition. Seasonal analysis demonstrated that HONO loss was largely controlled by photolysis in summer. Externally transported aerosols contributed more than locally formed particles at both sites, emphasizing the role of regional background pollution. These findings provide a scientific basis for region-specific air quality strategies that combine local precursor control with the management of long-range transport. Full article

Biochars were prepared from rice husk at different pyrolysis temperatures (300, 400, and 500 °C) and then modified by nitric acid (HNO₃) and potassium hydroxide (KOH). The chemical and physical properties were characterized, and the adsorption ability of biochars for the removal of Cd (II) and Pb (II) was investigated. The results showed that with increasing pyrolysis temperature, the aromaticity of rice husk biochar increased while its polarity decreased and both specific surface area and total pore volume significantly increased. Both HNO₃ and KOH modification significantly changed the oxygen-containing functional groups in biochar, especially biochars prepared at lower pyrolysis temperatures. HNO₃ modification introduced nitro and carboxyl groups on the surface of HNO₃-BC300, increasing the ether bond functional groups, while KOH modification increased the content of hydroxyl groups on KOH-BC300 and reduced the ether bond groups. At the same time, the modification of rice husk-derived biochar greatly enhanced the ability to absorb Cd (II) and Pb (II) from aqueous solution. Notably, KOH-BC300 exhibited the highest adsorption capacities, reaching 72.14 mg·g⁻¹ for Cd (II) and 170.84 mg·g⁻¹ for Pb (II). These results demonstrate that KOH modification was more effective than HNO₃ modification at enhancing the adsorption of Cd (II) and Pb (II) onto rice husk-derived biochar. In addition, the specific surface area and total pore volume of biochar increased significantly after HNO₃ and KOH modification. It was concluded that biochar’s adsorption performance might be greatly improved by increasing its oxygen-containing functional groups and specific surface area, but the effect of oxygen-containing functional groups was greater than that of specific surface area. Thus, KOH-modified biochar (KOH-BC300) can be used as an effective sorbent for heavy metal removal from wastewater. Full article

The synergistic effect of using D2EHPA and TOPO together to enhance the extraction of samarium(III) from aqueous media via emulsion liquid membrane (ELM) technology was explored. D2EHPA in binary mixtures with TBP and in ternary mixtures with TOPO and TBP was also tested. Among the tested extractants, a binary mixture of 0.1% (w/w) D2EHPA and 0.025% (w/w) TOPO achieved 100% samarium(III) extraction at a low loading. This mixture outperformed D2EHPA-TBP and other systems because D2EHPA strongly binds to Sm(III) ions, while TOPO increases the solubility and transport efficiency of metal complexes. Additionally, process factors that optimize performance and minimize emulsion breakage were examined. Key insights for successfully implementing the process include the following: 5 min emulsification with 0.75% Span 80 in kerosene at pH 6.7 (natural), 250 rpm stirring, a 1:1 internal/membrane phase volume ratio, a 20:200 treatment ratio, and a 0.2 N HNO₃ stripping agent. These insights produced stable, fine droplets, enabling complete recovery and rapid carrier regeneration without emulsion breakdown. Extraction kinetics accelerate with temperature up to 35 °C but declined above this limit due to emulsion rupture. The activation energy was calculated to be 33.13 kJ/mol using pseudo-first-order rate constants. This suggests that the process is diffusion-controlled rather than chemically controlled. Performance decreases with Sm(III) feed concentrations greater than 200 mg/L and in high-salt matrices (Na₂SO₄ > NaCl > KNO₃). Integrating these parameters yields a scalable, low-loading ELM framework capable of achieving complete Sm(III) separation with minimal breakage. Full article

This study reports an investigation of the synergistic extraction of dysprosium (Dy(III)) from aqueous media using a low-concentration, binary carrier mixture of Cyanex 272 and D2EHPA within an emulsion liquid membrane (ELM). Within the tested formulations, the one containing 0.42% (w/w) Cyanex 272 and 0.28% (w/w) D2EHPA yielded the best results. The impact of process factors that maximize recovery efficiency and minimize emulsion breakdown was also examined. A Span 80 loading of 0.75% (w/w) achieved 97.5% extraction with minimal breakage (less than 2.1%). An external phase pH of 5.8 achieves an optimal balance of high-throughput Dy(III) recovery and membrane stability; 0.2 N HNO₃ as the stripping phase strikes the optimal balance, providing strong initial uptake with minimal emulsion degradation. As the initial Dy(III) loading increases, extraction efficiency decreases. Increasing the temperature from 15 to 45 °C accelerates mass transfer, achieving near-complete extraction in under 15 min. However, above 45 °C, emulsion breakage spikes, causing a collapse in efficiency. Similarly, increasing NaCl levels suppresses Dy(III) uptake and promotes coalescence. This reduces recovery from seawater to just over 70%. Nevertheless, the balanced mineral content of Zamzam water preserves emulsion integrity and enables 100% extraction. The activation energy was found to be 26.16 kJ/mol, suggesting that mass transfer, rather than the chemical reaction at the interface, controls the process. The results of this study highlight the synergistic efficiency advantage of the ELM system at lower carrier concentrations, even in complex water sources. Full article

In this study, 10% nitric acid was employed to remove the aluminum coating on the cobalt-based superalloy K6509, with a focus on elucidating the corrosion mechanism and evaluating the effect of ultrasonic on the removal process. The results shows that ultrasonic treatment (40 kHz) significantly improves coating removal efficiency, increasing the maximum corrosion rate by 46.49% from 2.5413 × 10⁻⁷ g·s⁻¹·mm⁻² to 4.7488 × 10⁻⁷ g·s⁻¹·mm⁻² and reducing removal time from 10 min to 6 min. This enhancement is attributed to cavitation effect of ultrasonic bubbles and the shockwave-accelerated ion diffusion, which together facilitate more efficient coating degradation and results in a smoother surface. In terms of corrosion behavior, the difference in phase composition between the outer layer and the interdiffusion zone (IDZ) plays a decisive role. The outer layer is primarily composed of β-(Co,Ni)Al phase, which is thermodynamically less stable in acidic environments and thus readily dissolves in 10% HNO₃. In contrast, the IDZ mainly consists of Cr₂₃C₆, which exhibit high chemical stability and a strong tendency to passivate. These characteristics render the IDZ highly resistant to nitric acid attack, thereby forming a protective barrier that limits acid penetration and helps maintain the integrity of the substrate. Full article

Terbium-161 (¹⁶¹Tb) is an emerging β⁻-emitting radionuclide of high interest for targeted radionuclide therapy. However, its reactor-based production presents significant challenges in the efficient separation of ¹⁶¹Tb from target ¹⁶⁰Gd and co-produced ¹⁶¹Dy. In this study, the separation of ¹⁶¹Tb by a solvent-impregnated resin P350@resin has been evaluated. A combination of static adsorption and dynamic column experiments was conducted to investigate the separation behavior of Gd³⁺, Tb³⁺, and Dy³⁺. Optimal separation performance was achieved at 0.4–0.6 mol/L HNO₃, using a column bed height of 20–28 cm and flow rates of 0.5–1.0 mL/min. A two-step elution protocol enabled near-baseline resolution between Tb and Gd, Dy within 3 h, ensuring high-purity and fast product recovery. Comprehensive characterization using SEM-EDS, FT-IR, and XPS confirmed that metal ion uptake occurs via coordination with phosphoryl groups on the resin. The P350@resin thus enables a simple and selective separation platform for the production of no-carrier-added ¹⁶¹Tb, with high potential for clinical radiopharmaceutical manufacturing. Full article

A new approach to the synthesis of a nanosized and hierarchical titanosilicate, TS-1, is presented. Instead of using specific solid or additional mesoporous templates or individual additives to slow down the hydrolysis of titanium alkoxides, it is proposed that the titanosilicate TS-1 can be obtained from gels synthesized with hydrolysis catalysts (HNO₃ and tetrapropylammonium hydroxide). When nitric acid catalyzes tetraethyl orthosilicate (TEOS) hydrolysis, the resulting crystalline TS-1 that can be obtained has uniform particle sizes (150–180 nm), is anatase-free, and contains up to 46–67% of mesopores. When a base catalyst is applied, the obtained material’s features are opposite. Moreover, acid-promoted TS-1 samples catalyze cyclohexene H₂O₂-oxidation via a heterolytic route to the cyclohexane epoxide with 67% selectivity, which is non-typical. Full article