Water Oxygen Research Articles

Conceptual study on the intensification of gas–liquid mass transfer in trickle bed reactors by the application of strut-based and novel sheet-based periodic open cellular structures (POCS)

Rapid progress in the development of additive manufacturing technology enables the production of structured reactor internals of complex geometry. To address mass transport limitations structured internals can be used in trickle bed reactors (TBRs) as the most frequently used reactor for heterogeneously catalyzed multiphase reactions. However, reactions in TBRs are frequently limited by gas–liquid mass transfer.As periodic open cellular structures (POCS) as reactor internals were not addressed regarding g–l mass transfer yet, this contribution provides first data on gas–liquid mass transfer for different types of POCS. Therefore, desorption of dissolved oxygen in water with nitrogen gas and the two-phase pressure drop were measured. Strut-based Kelvin and diamond unit cell POCS were compared to a sphere random packed bed as a benchmark. A novel sheet-based unit cell was developed realizing meandering channels demonstrating a fivefold increase in volumetric mass transfer coefficient compared to the benchmark. To compare the performance of the setup with literature data, state of the art neural network correlations were used for comparison. This proof of concept highlights the potential of additively manufactured POCS for intensified processes in trickle bed reactors, and demonstrates their versatility in application.

Preparation of Oriented Nanoporous Magnetite Films by a Template-Free Solution Process from Iron Oxyhydroxide Films

Nanoporous oxide films composed of nanocrystal assemblies with an aligned crystallographic orientation are key nanostructures for efficient interfacial reactions. However, a simple, template-free method for their formation remains a challenge. Layered metal hydroxide (LMH) films are a promising precursor for spontaneous formation of nanoporous oxide films.[1-4] LMHs have a layered structure comprising 2D sheets of edge-shared octahedral hydroxide, i.e., brucite structure, with or without interlayer anions and water molecules. Calcination of LMH results in dehydration, anion elimination, and volume shrinkage, leading to the spontaneous formation of nanoporous oxides.In this study, we have prepared nanoporous and ferrimagnetic magnetite (Fe3O4) films by using layered iron hydroxides, namely, green rust (GR), as a precursor. Generally, GR has a brucite-type structure containing Fe2+ and Fe3+ ions, and is highly susceptible to oxidation by oxygen in water and air, leading to the formation of iron oxyhydroxides (FeOOH). Here, GR films were electrochemically deposited on FTO substrates in an aqueous solution containing Fe2+ and NO3 − ions at room temperature. Drying the GR films in air resulted in the formation of two-type FeOOH films, depending on the electrodeposition condition. Characterization using X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and FT-IR spectroscopy revealed that one is [010]-oriented γ-FeOOH films, and the other is [001]-oriented δ-FeOOH films. The obtained FeOOH films had a mille-feuille like morphology with 500–700 nm thickness. Heat treatment of these two-type FeOOH films under vacuum at 500 °C resulted in the formation of [110]- and [111]-oriented nanoporous Fe3O4 films. The obtained Fe3O4 films showed a ferrimagnetic behavior in VSM measurements and had a nanoporous structure comprising nanoparticles with 50–100 nm diameter.Finally, a possilble interpretation for the observed orientation relationships between the FeOOH and Fe3O4 was also discussed on the basis of pyrolysis intermediates of FeOOH and similarity in their atomic arrangements. References T. Shinagawa, M. Watanabe, T. Mori, J.-i. Tani, M. Chigane and M. Izaki, Inorg. Chem., 57, 13137 (2018).T. Shinagawa, M. Chigane and M. Izaki, ACS Omega, 6, 2312 (2021).T. Shinagawa, M. Chigane and M. Takahashi, Cryst. Growth Des., 22, 4122 (2022).T. Shinagawa, N. Kotobuki and A. Ohtaka, Nanoscale Adv., 5, 96 (2023). Figure 1

Fabrication of multifunctional ZnO@tannic acid nanoparticles embedded in chitosan and polyvinyl alcohol blend packaging film

The current study explores biodegradable packaging materials that have high food quality assurance, as food deterioration is mostly caused by UV degradation and oxidation, which can result in bad flavor and nutrition shortages. Thus, new multifunctional zinc oxide nanoparticles/tannic acid (ZnO@TA) with antioxidant and antibacterial activities were incorporated into polyvinyl alcohol/chitosan (PVA/CH) composite films with different ratios (1%, 3%, and 5% based on the total dry weight of the film) via a solution blending method in a neutral aqueous solution. Additionally, ZnO nanoparticles have unique antibacterial mechanisms through the generation of excessive reactive oxygen species (ROS) that may lead to intensify pathogen resistance to conventional antibacterial agents. Thus, minimizing the negative effects caused by excessive levels of ROS may be possible by developing unique, multifunctional ZnO nanoparticles with antioxidant potential via coordination bond between tannic acid and ZnO nanoparticles (ZnO@TA). ZnO@TA nanoparticles were examined using Fourier-transform infrared (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The effect of the incorporation of ZnO@TA nanoparticles on the barrier, mechanical, thermal, antioxidant, antimicrobial, and UV blocking characteristics of chitosan/polyvinyl alcohol (ZnO@TA@CH/PVA) films was investigated. The lowest water vapor and oxygen permeability and the maximum antioxidant capacity% are 31.98 ± 1.68 g mm/m2 kPa day, 0.144 ± 5.03 × 10–2 c.c/m2.day, and 69.35 ± 1.6%, respectively, which are related to ZnO@TA(50)@CH/PVA. Furthermore, ZnO@TA(50)@CH/PVA film exhibits the maximum UV shielding capacity of UVB (99.994). ZnO@TA(50) @PVA/CH films displayed better tensile strength and Young`s modulus of 48.72 ± 0.23 MPa and 2163.46 ± 61.4 MPa, respectively, than the other film formulations. However, elongation % at break exhibited the most reduced value of 19.62 ± 2.3%. ZnO@TA@CH/PVA film exhibits the largest inhibition zones of 11 ± 1.0, 12.3 ± 0.57, and 13.6 ± 0.57 mm against Staphylococcus aureus, Aspergillus flavus, and Candida albicans, respectively. In accordance with these results, ZnO@TA@CH/PVA films could be utilized for food preservation for the long-term.

Bilayer pH-sensitive colorimetric indicator films based on chitosan/purple carrot extract and gellan gum/Mg-carbon dots for visual monitoring of pork freshness

A pH-sensitive colorimetric bilayer film was constructed on the basis of layer-by-layer self-assembly, with chitosan (CS)-loaded purple carrot anthocyanin (PCA) as the inner indicator layer and gellan gum (GG)-loaded Mg-doped carbon dots (Mg-CDs) as the protective outer layer. X-ray diffraction and scanning electron microscopy analyses confirmed the successful preparation of the bilayer film and the incorporation of Mg-CDs. Fourier transform infrared spectroscopy indicated that the Mg-CDs formed hydrogen bonds with the film matrix. Thermogravimetric analysis revealed that the Mg-CDs improved the thermal stability of the double-layer films. Moreover, the addition of 7 wt% Mg-CDs increased the water vapor permeability, oxygen permeability, and tensile strength of the films by 0.94-, 0.79-, and 3.18-fold, respectively. The antioxidant and antimicrobial activities of the films were significantly enhanced by including Mg-CDs as the active agents. Illumination experiments revealed that the relative color change (S values) increased by only 2.76 % and 4.69 % after the addition of 7 wt% Mg-CDs to the GG -Mg-CDs layer after 21 days of visible light and 72 h of UV light exposure, respectively. These bilayer films containing PCA and Mg-CDs exhibit good pH color responsiveness and biosafety. The C-P/G-7 %CD film had the best overall performance and can effectively reflect pork freshness during storage. Therefore, this research has great potential for developing a double-layer film for monitoring meat quality changes in intelligent food packaging.

Spatial and seasonal variability in benthic impact of mussel farms: Predicting and mitigating impacts using ambient oxygen conditions

Environmental impacts are a cause for concern when developing and expanding aquaculture and to be sustainable potential negative effects need to be addressed. The intensity and extent of these impacts likely vary among sites and seasons, depending on multiple factors including the physical and biological setting and operational aspects. Using a combination of sampling techniques, we investigated the spatial variability in epibenthic impacts in eleven commercial mussel farms, on the Swedish west coast. We found increased levels of organic content, changes in epibenthic macrofauna and increased cover of Beggiatoa sp., a documented indicator of hypoxia. The extent of these impacts was generally limited to the extent of the farms. Because the cover of Beggiatoa sp. was particularly clear and because oxygen conditions in the sediment is of great importance to the structure and function of these habitats, we analysed spatial patterns using an index of the benthic footprint (BFI) accounting for both intensity and extent of impacts. In the summer, the BFI varied strongly among farm-sites and subsequent analyses showed that it highly correlated with ambient bottom oxygen concentration. Repeated sampling during early spring, however, showed that impacts were quickly reversible also in the most impacted sites. Thus, we conclude that in Swedish coastal waters the benthic footprint calculated on the % cover of Beggiatoa sp. is highly dependent on ambient oxygen concentration. We suggest that knowledge about spatial and temporal patterns of oxygen in the bottom water can be used to predict the severity of impacts and provide an important criterion in a site-selection process aimed at developing a sustainable food industry.

Shock-Layer Measurements in T5 Shock Tunnel Hypersonic Flows Around a Cylinder Model

We report on near-body measurements of temperature and nitric oxide (NO) concentration in the hypersonic flows around a cylindrical test article in the Caltech T5 reflected shock tunnel. Flow measurements were made at 50 kHz using tunable diode laser absorption spectroscopy, deploying six lasers to probe an array of quantum state-specific transitions. Laser beams were positioned both in the freestream and behind the bow shock at specific locations deemed pertinent to computational fluid dynamics comparison and kinetic model evaluation. The fractions of laser beam pathlengths behind the shock in different spatial regions were also discerned, thus providing a measurement of shock location. This study consists of six total experiments (“shots”) across two Mach ∼5 conditions, characterized by total enthalpies of 8 and 16 MJ/kg and freestream velocities of 3.5 and 5 km/s, respectively. Freestream measurements generally concur with prior works in the T5, but with some non-trivial differences. Shock-layer measurements span from 2000 to 6000 K and feature noteworthy and expected variety among different zones within the post-shock region. Thermal equilibrium is generally held throughout the flowfield, but chemical nonequilibrium is commonly observed. NO is the primary spectroscopic target, but measurements of carbon monoxide, carbon dioxide, water, and atomic oxygen provide supplementary insights.

Offshore windfarm construction elevates metabolic rate and increases predation vulnerability of a key marine invertebrate

A global increase in offshore windfarm development is critical to our renewable energy future. Yet, widespread construction plans have generated substantial concern for impacts to co-occurring organisms and the communities they form. Pile driving construction, prominent in offshore windfarm development, produces among the highest amplitude sounds in the ocean creating widespread concern for a diverse array of taxa. However, studies addressing ecologically key species are generally lacking and most research is disparate, failing to integrate across response types (e.g., behavior, physiology, and ecological interactions), particularly in situ. The lack of integrative field studies presents major challenges to understand or mitigate actual impacts of offshore wind development. Here, we examined critical behavioral, physiological, and antipredator impacts of actual pile driving construction on the giant sea scallop (Placopecten magellanicus). Benthic taxa including bivalves are of particular concern because they are sound-sensitive, cannot move appreciable distances away from the stressor, and support livelihoods as one of the world's most economically and socially important fisheries. Overall, pile driving sound impacted scallops across a series of behavioral and physiological assays. Sound-exposed scallops consistently reduced their valve opening (22%), resulting in lowered mantle water oxygen levels available to the gills. Repeated and rapid valve adductions led to a 56% increase in metabolic rates relative to pre-exposure baselines. Consequently, in response to predator stimuli, sound-exposed scallops displayed a suite of significantly weaker antipredator behaviors including fewer swimming events and shorter time-to-exhaustion. These results show aquatic construction activities can induce metabolic and ecologically relevant changes in a key benthic animal. As offshore windfarm construction accelerates globally, our field-based study highlights that spatial overlap with benthic taxa may cause substantial metabolic changes, alter important fisheries resources, and ultimately could lead to increased predation.

Characteristics and Distribution of Chemical-Biological Parameters in The Seawaters of Eastern Java Sea

The Java Sea is influenced by the west and east monsoons, which have an impact on hydrodynamic processes and chemical-biological water quality. Chemical-biological parameters play an important role in the food chain cycle that occurs in these waters. The quality of the eastern Java Sea waters is still limited by chemical-biological parameters, so the characteristics and distribution of these waters can be comprehensively known. chemical-biological. This study aimed to analyze the characteristics and distribution of nitrate, phosphate, oxygen, chlorophyll-A, and NPP parameters in the eastern Java Sea waters. This study used secondary data with daily temporal resolution from January to December 2020. Spatial analysis uses the climatological averaging method for 6 months as a statistical representative of the west monsoon and east monsoon. For each parameter, a vertical analysis was conducted to compare parameter values between the coastal waters of Tuban, Java Sea, and Banjarmasin Waters. Correlation analysis between parameters was conducted using the Pearson correlation method. Nitrate, phosphate, oxygen, chlorophyll-A, and NPP concentrations have temporal and spatial variability. Monsoon factors in Indonesia have a strong influence on the variability of nitrate, phosphate, oxygen, chlorophyll- A, and NPP concentrations. During the east monsoon, the concentration of chemical-biological parameters decreases, while in the west monsoon, the concentration increases and reaches its highest value. Generally, high concentrations occur in the northern and southern parts of the study site, around the coastal areas of Java and Kalimantan. Key Word: Chemical-Biological Parameters, Java Sea, Tuban Waters

Chitosan-casein blended with condensed tannin and carnauba wax for the fabrication of antibacterial and antioxidant food packing films

In this study, various chitosan-based films such as chitosan (C), chitosan-condensed tannin (CT), chitosan-casein (CC), and chitosan-casein-condensed tannin (CCT) films were prepared for the purpose of food packaging. In order to improve the hydrophobicity of these films, carnauba wax was blended into CCT to produce CCTW film. Properties such as morphology, UV resistance, water solubility, barrier performance, tensile strength, antioxidant, antibacterial and its performance as food packaging were evaluated. Compared with other chitosan-based films, CCTW films exhibited higher UV resistance, tensile strength, thermal stability and hydrophobicity. The addition of both condensed tannin and carnauba wax has significantly decreased the water vapor and oxygen permeability of the CCTW films. The CCTW films were proved capable of repelling most daily consuming liquids. Besides, CCTW films displayed outstanding free radical scavenging rate and antibacterial properties. Meanwhile, bananas wrapped with CCTW films remained fresh for seven days without any mold growth and outperformed other types of films. Apart from that, the CCTW films also showed biodegradable characteristics after exposure to Penicillium sp. These distinguished characteristics made the CCTW films a promising packaging material for long-term food storage.

High-barrier, flexible, hydrophobic, and biodegradable cellulose-based films prepared by ascorbic acid regeneration and low temperature plasma technologies

Regenerated cellulose (RC) films are considered a sustainable packaging material that can replace non-degradable petroleum-based plastics. However, their susceptibility to water vapor and oxygen can limit their effectiveness in protecting products. This study introduces a novel approach for enhancing RC films to create durable, flexible, hydrophobic, high-barrier, and biodegradable packaging materials. By exploring the impact of ascorbic acid coagulation bath treatment and plasma-enhanced chemical vapor deposition (PECVD) on the properties of RC films, we found that the coagulation bath treatment facilitated the organized reconfiguration of cellulose chains, while PECVD applied a dense SiOx coating on the film surface. The results demonstrated a significant enhancement in water vapor and oxygen barrier properties of the composite film, almost reaching the level of commercial barrier films. Moreover, the composite film displayed exceptional biodegradability, fully degrading in soil within 35 days. Additionally, it showcased impressive mechanical strength, hydrophobic characteristics, and freshness preservation, positioning it as a valuable option for bio-based high-barrier packaging applications.

Changes in the particulate organic carbon pump efficiency since the Last Glacial Maximum in the northwestern Philippine Sea

Changes in bottom and pore water oxygenation over glacial – interglacial cycles have influenced the ocean's capacity to store particulate organic carbon regardless of its source, either the marine primary productivity or the continent-to-ocean transfer of terrestrial organic matter. In the Philippine Sea, east off Taiwan, despite being currently oligotrophic, the enhanced East Asian Winter Monsoon during the Last Glacial Maximum and the Heinrich Stadial 1 might have altered the nutrient budget in surface waters by providing nutrients from the Eurasian loess dust and deepening the vertical mixing, bringing nutrients from the nutrient-enriched Kuroshio Current subsurface waters to the surface. During the deglaciation, previous studies also suggest an overall weakening of the marine biological pump during the Heinrich Stadial 1, and the rise in sea level is expected to have led to a global significant decline in the ability of continents to bury their particulate organic carbon in marine sediments. However, changes in the continent-ocean transfer of terrestrial organic matter and on the marine biological pump around Taiwan remain poorly constrained.In the present study, we have thus aimed to reconstruct bottom – pore water oxygenation, past marine primary productivity and continental-ocean transfer of terrestrial particulate organic carbon to the ocean since the end of the Last Glacial Maximum, in order to better constrain the ability of marine sediments to capture atmospheric carbon over the past 20,000 years. To this end, sediment core MD18-3523 has been recovered from a levee of Hoping Canyon, north-east of Taiwan, in the Ryukyu forearc basin. The reconstructions were made possible by the application of multivariate statistics and transfer functions on benthic foraminiferal assemblages, by the measurement of total organic carbon concentration and by the investigation of chemical element ratios obtained from X-ray fluorescence (XRF).We observed a transition across the Bølling–Allerød and the Younger Dryas from suboxic-dysoxic bottom – pore waters during Heinrich Stadial 1 to oxic-suboxic during the Holocene, and revealed an increase in marine primary productivity during Heinrich Stadial 1 in all probability due to intensified East Asian Winter Monsoon winds. We have also identified periods of enhanced terrestrial particulate organic carbon transfer to the ocean driven by short-lived extreme events, most likely typhoons, during the Bølling–Allerød, at the beginning of the Early Holocene and the end of the Late Holocene, when the typhoon dynamics affecting Taiwan were intensified. Overall, these findings suggest an enhanced marine biological pump during the Heinrich Stadial 1 and an efficient carbon turbidity pump during the Bølling–Allerød, the Early and Late Holocene, contrasting with the western coast of Taiwan.

Coconut Shells, Water Hyacinth and Rice Husks are Very Effective in Improving the Quality of Physical and Chemical Standards of Dug Well Water in Flood Areas

Introduction: Ensuring access to clean and safe drinking water is crucial, especially in flood-prone regions where the water quality in dug wells can deteriorate due to various physicochemical factors. This research was aimed to measure the effectiveness of natural materials in improving water quality based on physicochemical parameters and to compare water quality before and after treatment in Astambul Subdistrict of Banjar Regency, South Kalimantan Province. Methods: The study involved a survey of 192 private boreholes and dug wells across five villages in the Astambul Subdistrict, with 30 samples selected for detailed analysis. Key physicochemical parameters analyzed included total dissolved solids (TDS), dissolved oxygen (DO), turbidity, and total suspended solids (TSS). TDS, with a standard limit of 50 mg/L, served as a primary water quality indicator. DO, essential for gauging water oxygenation, and was measured as it results from photosynthesis and atmospheric absorption. Turbidity was assessed using a turbidimeter to determine water clarity, and a UV-vis Spectrophotometer 2008 was utilized to measure levels of iron (Fe) and mangasene (Mn). Results and Discussion: The findings demonstrated that coconut shells, husks, and water hyacinths improved water quality across physical and chemical parameters. Statistical analysis using t-tests showed improvements in these parameters after treatment. For example, DO levels increased in multiple villages, with the highest percentage in Kaliukan Village (59.2%) and decreases in turbidity and TSS. Conclusion: The study concluded that coconut shells, husks, and water hyacinths have potential to enhance physicochemical quality of water.

A synergistic influence of gallic acid/ZnO NPs to strengthen the multifunctional properties of methylcellulose: A conservative approach for tomato preservation

Biodegradable and sustainable food preservation materials have gained immense global importance to mitigate plastic pollution and environmental impact. Biopolymers like cellulose offer significant advantages for food preservation, including biodegradability and the ability to extend shelf life. Therefore, the present study aims to prepare gallic acid (GA) and zinc oxide nanoparticles (ZnO NPs) incorporated methylcellulose (MC) composite films by employing a solvent casting technique. The homogeneous SEM micrographs and FTIR spectra evidenced high compatibility among MC and GA/ZnO NPs. The UV barrier capacity, mechanical properties and surface hydrophobicity are remarkably enhanced by GA/ZnO NPs. However, the water vapour permeability and oxygen permeability of MGZ films were reduced by 49.19 % and 57.75 % respectively. Moreover, the MGZ films demonstrated exceptional antioxidant efficacy (∼94.48 %) and inhibition against food-borne pathogens such as B. subtilis, S. aureus (Gram-positive), E. coli, P. aeruginosa (Gram-negative), and C. albicans fungi. Furthermore, the GA/ZnO NPs extended the shelf life of MGZ coated tomato samples up to 27 days and exhibited controlled microbial growth after the preservation study. These results support the application of MGZ films as suitable and effective coating materials for food packaging applications.

Eco‐friendly enhancement of poly(lactic acid)/poly(butylene adipate‐co‐terephthalate) bridgeable composites using natural cotton stalk: A novel approach to improved mechanical, barrier properties, and compatibility

AbstractThis study investigates the potential of using natural cotton stalk (CS) to enhance the properties of poly(lactic acid) (PLA) and poly(butylene adipate‐co‐terephthalate) (PBAT) composite materials. Simple processed CS, used as a bio‐based filler, is integrated into the PLA/PBAT matrix with the objective of improving mechanical properties, barrier performance, and compatibility, while simultaneously reducing costs and environmental impact. The experiments conducted include tensile testing, scanning electron microscopy analysis, Fourier‐transform infrared spectroscopy (FTIR) analysis, X‐ray diffraction study, thermogravimetric analysis, contact angle measurement, water absorption tests, as well as water vapor and oxygen permeability tests. The results demonstrate that the inclusion of CS significantly enhances the mechanical properties and crystallinity of PLA/PBAT composites, along with increasing their water vapor and oxygen barrier capabilities. Compared to PLA/PBAT without CS, the addition of 2% CS to PLA/PBAT led to substantial improvements in tensile strength and elongation at break, with increases of 21.5%, 41.6%, and 74.4%, respectively. Additionally, scanning electron microscopy and Fourier‐transform infrared spectroscopy analyses indicate that the incorporation of CS promotes the compatibility and chemical interaction between PLA and PBAT, thereby enhancing various properties of the composite material. Image analysis revealed that the distribution area of CS fibers in the polymer matrix increased with content up to a peak at 2% but decreased at higher contents due to severe agglomeration, leading to uneven distribution and performance decline. This work proposes three possible reasons for the improvement in water vapor and oxygen permeability performance. Overall, the analysis suggests that an optimal amount of CS can effectively enhance multiple properties of PLA/PBAT composites, while excessive CS may lead to a decline in performance.Highlights Cotton stalk (CS) boosts polylactic acid/poly(butylene adipate‐co‐terephthalate) (PLA/PBAT) tensile strength by 21.5% and elongation by 41.6% at 2% inclusion. CS addition enhances water vapor and oxygen barrier properties of PLA/PBAT. Scanning electron microscopy and Fourier‐transform infrared spectroscopy show CS improves PLA/PBAT compatibility and strength. Optimal CS content at 2% identified for best mechanical and barrier performance. Study validates using agricultural waste as fillers in eco‐friendly composites.

Characterization of Composite Film Containing Polyvinyl Alcohol Cross‐Linked With Dialdehyde Cellulose Using Citric Acid as a Catalyst for Sustainable Packaging

ABSTRACTThis study is aimed at fabricating composite films by cross‐linking polyvinyl alcohol (PVA) and dialdehyde cellulose (DAC) in varying ratios using citric acid as a catalyst. The acetal formation between the two components was studied using FTIR. Characterizations of the physiochemical properties revealed that increasing the DAC ratio of the composite film improved the hydrophobicity, tensile strength and barrier properties (water vapour, UV and oxygen) of the films while reducing elongation at break (flexibility), swelling and solubility of the film in water. When the DAC ratio was elevated to 50%, the tensile strength was enhanced to 98 MPa. In comparison, flexibility diminished to 29%, the solubility of the film reduced to 10% and water vapour permeability was lower by two orders of magnitude than that of the control PVA film. The peroxide value of linoleic acid decreased from 21.2% ± 7.6 (packed with PVA film) to 9.9% ± 0.9 (packed with 50% DAC composite film) after 15 days. Furthermore, the composite films demonstrated effective absorption of UV radiation, with the order of effectiveness being UV‐C > UV‐B > UV‐A radiation. No significant difference in biodegradability was detected in the composite films with an increase in DAC ratio during indoor soil burial tests for 30 days. This study implies that the composite film could serve as an alternative sustainable packaging option, especially when transparency and high oxygen barrier properties are desired.

Facile Preparation of Chitosan/Carnauba Wax Emulsion‐Based Coatings for Hydrophobic and Oleophobic Cellulose‐Based Food Packaging

ABSTRACTStudies have shown that fluoridated reagents for oil and water resistance are harmful to the human bodies and the environment. Consequently, the developments of nontoxic, environmentally friendly, fluorine‐free and degradable materials have received increasing attentions. Here, we introduce a novel method for fabricating a hydrophobic and oleophobic paper‐based packaging material through the application of chitosan/carnauba wax emulsions. These emulsions were prepared via high‐shear homogenization, blending melted carnauba wax with chitosan in acetic acid aqueous solutions. The stable chitosan/carnauba wax emulsion with particle size of 430 nm was prepared at the chitosan concentration of 1.5 wt%, the carnauba wax concentration of 8 wt% and temperature of 85 °C. After 10 g/m2 of chitosan/carnauba wax emulsion was applied to the paper surface, the oil and water resistance of the paper was significantly improved. The experimental results of kit rating value, oil contact angle, Cobb60 value and water contact angle were 9.5 ± 0.6, 86.6 ± 2.1°, 8.90 ± 1.62 g/m2 and 123.5 ± 2.6°, respectively. The application of chitosan/carnauba wax emulsion coating on papers provided a significantly lower water vapour transmission rate (WVTR, 78.45 ± 18.92 g/m2·24 h) and oxygen transmission rate (OTR, 94.26 ± 20.21 g/m2·24 h) as compared to the original paper, which met the needs of strawberry packaging.

High-temperature corrosion testing of titanium beryllides in the presence of water vapor and oxygen

Beryllium-based intermetallics are promising materials for the blankets of future fusion reactors and have potential applications in other areas of the nuclear industry, such as fission reactor reflectors and space technology. Understanding the high-temperature corrosion behavior of these materials in a noble gas medium containing chemically active impurities is essential for evaluating their suitability and guiding their application.This study investigates the high-temperature corrosion of titanium beryllide Be12Ti in the form of plate and grinded samples, produced by JSC “Ulba Metallurgical Plant” (Ust-Kamenogorsk, Kazakhstan). The corrosion tests were conducted under non-isothermal vapor-gas mixture (Ar + D2O or Ar + H2O flowing atmospheres) purging conditions using thermogravimetric (TG) analysis, differential scanning calorimetry (DSC), and mass-spectrometry of the gas phase.As a result of the corrosion tests, new experimental data on thermal effects have been obtained, describing the corrosion processes of Be12Ti samples across a wide range of temperatures and various heating rates in the presence of water vapor in the purge gas. The dependencies of sample mass change under heating conditions have been determined, and the characterization results of the samples before and after high-temperature corrosion tests are presented.Corrosion of titanium beryllides, both for Be12Ti plate and grinded samples, follows similar mechanisms. At around 500 °C, the mass of the samples begins to increase, and hydrogen isotopes are released. The test results indicate that corrosion of titanium beryllides with varying surface inhomogeneities proceeds similarly within the temperature range of 500–900 °C, showing a linear dependence on temperature.The results revealed significant insights into the oxidation mechanisms and the formation of corrosion products, which are crucial for optimizing the material's performance in fusion reactor environments.

How Often Should Microbial Contamination Be Detected in Aircraft Fuel Systems? An Experimental Test of Aluminum Alloy Corrosion Induced by Sulfate-Reducing Bacteria.

Microbial contamination in aircraft fuel-containing systems poses significant threats to flight safety and operational integrity as a result of microbiologically influenced corrosion (MIC). Regular monitoring for microbial contamination in these fuel systems is essential for mitigating MIC risks. However, the frequency of monitoring remains a challenge due to the complex environmental conditions encountered in fuel systems. To investigate the impact of environmental variables such as water content, oxygen levels, and temperature on the MIC of aluminum alloy in aircraft fuel systems, orthogonal experiments with various combinations of these variables were conducted in the presence of sulfate-reducing bacteria. Among these variables, water content in the fuel oil demonstrated the most substantial influence on the corrosion rate of aluminum alloys, surpassing the effects of oxygen and temperature. Notably, the corrosion rate of aluminum alloys was the highest in an environment characterized by a 1:1 water/oil ratio, 0% oxygen, and a temperature of 35 °C. Within this challenging environment, conducive to accelerated corrosion, changes in the corrosion behavior of aluminum alloys over time were analyzed to identify the time point at which MIC intensified. Observations revealed a marked increase in the depth and width of corrosion pits, as well as in the corrosion weight-loss rate, starting from the 7th day. These findings offer valuable insights for determining the optimal frequency of microbial contamination detection in aircraft fuel systems.

The δ18O contrast between bulk goethite and water extracted from it does not reliably reveal goethite growth temperature

Goethite (α-FeOOH) contains two structurally-distinct oxygen sites that can potentially be independently interrogated for isotopic composition by analyzing bulk goethite δ18O (δ18Obulk) and the δ18O of water extracted from it (δ18Oextracted). The isotopic contrast between these two components may form the basis of a paleothermometer (Miller et al., 2020). We sought to better understand the behavior of goethite undergoing vacuum dehydroxylation, the key step in this potential paleothermometric technique. A refined method for making these measurements applied to a suite of natural and synthetic goethites revealed that δ18Oextracted is extremely sensitive to extraction temperature and to details of the vacuum environment in which the goethite is dehydroxylated. This sensitivity likely arises from the fundamental mechanism by which evolved water is removed from goethite in vacuum, via nm-wide pores penetrating nascent hematite surrounding dehydroxylating goethite. These pores may provide favorable conditions for back reaction that scrambles the oxygen isotopic composition, and also for kinetic mass fractionation. The character of these pores is known to vary with goethite composition, crystallinity, and extraction temperature. We identified additional sample-specific factors that affect δ18Oextracted. For example, some synthetic goethites undergo dehydroxylation at surprisingly low temperature (<90 °C) in vacuum, under conditions usually used to remove nonstoichiometric water. In addition, some of the synthetic goethites have spectroscopic characteristics suggesting a range of OH bonding environments that complicate the idea that goethite has just two structurally (and potentially isotopically) distinct oxygen sites. Instead, in fine grained or poorly crystalline goethite there may be a continuum of physisorbed water, chemisorbed water, and stoichiometric water that is simultaneously released during vacuum extraction. After investigating a wide range of extraction conditions, we determined that rapid heating to 255 ± 5 °C is optimal for achieving high degrees of water extraction with the least apparent back reaction. When applied to synthetic goethites grown between 5 °C and 70 °C, we found no compelling correlation between synthesis temperature and the contrast between δ18Obulk and δ18Oextracted. Analyses of two natural samples, known to have grown at ∼5 °C and ∼ 25 °C, revealed no significant difference in measured isotopic contrast. Together these observations suggest that goethite has no resolvable formation temperature information encoded in the bulk and extracted water oxygen isotope ratios as interrogated by the method we explored. If there is temperature-dependent isotopic contrast between the two oxygen sites in goethite, the use of the dehydroxylation method appears unable to reliably reveal it.

Development and Optimization of a Nanocomposite Gel Foam for Inhibiting Coal Spontaneous Combustion

ABSTRACT A nanocomposite gel foam inhibitor was made by grafting tea polyphenol onto sodium polyacrylate through the graft polymerization reaction, which was then combined with graphene oxide and a foaming agent. Response surface analysis was used to optimize the ratio to improve the water absorption of the inhibitor. The microstructure of the inhibitor was studied using X-ray diffraction and Fourier-transform infrared spectroscopy. The anti-spontaneous combustion performance of the nano-composite gel foam was tested through a leakage wind plugging experiment and a thermogravimetric experiment. The results show that the optimal additions of graphene, tea polyphenol, and potassium persulfate were 0.76%, 2.806%, and 0.727% of acrylic acid, respectively. The ultimate pressures of the gel foam before and after fully forming the gel were 0. 26 kPa and 0. 736 kPa, respectively, which satisfies the demand for leakage wind plugging in a coal mine. The critical temperature and dry cracking temperature of the gel foam were 112.4°C and 201.0°C, respectively, and the quality of the oxygen-absorbing and weight-gaining stage were almost unincreased. The gel foam showed good water retention, oxygen barrier, and antioxidant properties and can play a significant role in inhibiting the coal spontaneous combustion.