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Search Results (739)

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Keywords = high pressure synthesis

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12 pages, 2396 KiB  
Article
Helical Airflow Synthesis of Quinoxalines: A Continuous and Efficient Mechanochemical Approach
by Jiawei Zhang, Zeli Xiao, Qi Huang, Yang Zhao, Bo Jin and Rufang Peng
Chemistry 2025, 7(4), 121; https://doi.org/10.3390/chemistry7040121 - 29 Jul 2025
Viewed by 145
Abstract
In this work, we report a novel mechanochemical synthesis method for the synthesis of quinoxaline derivatives—a spiral gas–solid two-phase flow approach, which enables the efficient preparation of quinoxaline compounds. Compared to conventional synthetic methods, this approach eliminates the need for heating or solvents [...] Read more.
In this work, we report a novel mechanochemical synthesis method for the synthesis of quinoxaline derivatives—a spiral gas–solid two-phase flow approach, which enables the efficient preparation of quinoxaline compounds. Compared to conventional synthetic methods, this approach eliminates the need for heating or solvents while significantly reducing reaction time. The structures of the synthesized compounds were characterized using nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FT-IR), ultraviolet-visible (UV–Vis) absorption spectroscopy, powder X-ray diffraction (XRD), differential scanning calorimetry (DSC), and high-performance liquid chromatography (HPLC). Using the synthesis of 2,3-diphenylquinoxaline (1) as a model reaction, the synthetic process was investigated with UV–Vis spectroscopy. The results demonstrate that when the total feed amount was 2 g with a carrier gas pressure of 0.8 MPa, the reaction completed within 2 min, achieving a yield of 93%. Furthermore, kinetic analysis of the reaction mechanism was performed by monitoring the UV–Vis spectra of the products at different time intervals. The results indicate that the synthesis of 1 follows the A4 kinetic model, which describes a two-dimensional diffusion-controlled product growth process following decelerated nucleation. Full article
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33 pages, 3764 KiB  
Article
Cu2+ and Zn2+ Ions Affecting Biochemical Paths and DNA Methylation of Rye (Secale cereale L.) Anther Culture Influencing Plant Regeneration Efficiency
by Wioletta Monika Dynkowska, Renata Orłowska, Piotr Waligórski and Piotr Tomasz Bednarek
Cells 2025, 14(15), 1167; https://doi.org/10.3390/cells14151167 - 29 Jul 2025
Viewed by 90
Abstract
Rye regeneration in anther cultures is problematic and affected by albino plants. DNA methylation changes linked to Cu2+ ions in the induction medium affect reprogramming microspores from gametophytic to sporophytic path. Alternations in S-adenosyl-L-methionine (SAM), glutathione (GSH), or β-glucans and changes in [...] Read more.
Rye regeneration in anther cultures is problematic and affected by albino plants. DNA methylation changes linked to Cu2+ ions in the induction medium affect reprogramming microspores from gametophytic to sporophytic path. Alternations in S-adenosyl-L-methionine (SAM), glutathione (GSH), or β-glucans and changes in DNA methylation in regenerants obtained under different in vitro culture conditions suggest a crucial role of biochemical pathways. Thus, understanding epigenetic and biochemical changes arising from the action of Cu2+ and Zn2+ that participate in enzymatic complexes may stimulate progress in rye doubled haploid plant regeneration. The Methylation-Sensitive Amplified Fragment Length Polymorphism approach was implemented to identify markers related to DNA methylation and sequence changes following the quantification of variation types, including symmetric and asymmetric sequence contexts. Reverse-Phase High-Pressure Liquid Chromatography (RP-HPLC) connected with mass spectrometry was utilized to determine SAM, GSH, and glutathione disulfide, as well as phytohormones, and RP-HPLC with a fluorescence detector to study polyamines changes originating in rye regenerants due to Cu2+ or Zn2+ presence in the induction medium. Multivariate and regression analysis revealed that regenerants derived from two lines treated with Cu2+ and those treated with Zn2+ formed distinct groups based on DNA sequence and methylation markers. Zn2+ treated and control samples formed separate groups. Also, Cu2+ discriminated between controls and treated samples, but the separation was less apparent. Principal coordinate analysis explained 85% of the total variance based on sequence variation and 69% of the variance based on DNA methylation changes. Significant differences in DNA methylation characteristics were confirmed, with demethylation in the CG context explaining up to 89% of the variance across genotypes. Biochemical profiles also demonstrated differences between controls and treated samples. The changes had different effects on green and albino plant regeneration efficiency, with cadaverine (Cad) and SAM affecting regeneration parameters the most. Analyses of the enzymes depend on the Cu2+ or Zn2+ ions and are implemented in the synthesis of Cad, or SAM, which showed that some of them could be candidates for genome editing. Alternatively, manipulating SAM, GSH, and Cad may improve green plant regeneration efficiency in rye. Full article
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25 pages, 7428 KiB  
Article
Sialic Acid-Loaded Nanoliposomes with Enhanced Stability and Transdermal Delivery for Synergistic Anti-Aging, Skin Brightening, and Barrier Repair
by Fan Yang, Hua Wang, Dan Luo, Jun Deng, Yawen Hu, Zhi Liu and Wei Liu
Pharmaceutics 2025, 17(8), 956; https://doi.org/10.3390/pharmaceutics17080956 - 24 Jul 2025
Viewed by 238
Abstract
Objectives: Sialic acid (SA), a naturally occurring compound abundantly found in birds’ nests, holds immense promise for skincare applications owing to its remarkable biological properties. However, its low bioavailability, poor stability, and limited skin permeability have constrained its widespread application. Methods: [...] Read more.
Objectives: Sialic acid (SA), a naturally occurring compound abundantly found in birds’ nests, holds immense promise for skincare applications owing to its remarkable biological properties. However, its low bioavailability, poor stability, and limited skin permeability have constrained its widespread application. Methods: To overcome these challenges, SA was encapsulated within nanoliposomes (NLPs) by the high-pressure homogenization technique to develop an advanced and efficient transdermal drug delivery system. The skincare capabilities of this novel system were comprehensively evaluated across multiple experimental platforms, including in vitro cell assays, 3D skin models, in vivo zebrafish studies, and clinical human trials. Results: The SA-loaded NLPs (SA-NLPs) substantially improved the transdermal penetration and retention of SA, facilitating enhanced cellular uptake and cell proliferation. Compared to free SA, SA-NLPs demonstrated a 246.98% increase in skin retention and 1.8-fold greater cellular uptake in HDF cells. Moreover, SA-NLPs protected cells from oxidative stress-induced damage, stimulated collagen synthesis, and effectively suppressed the secretion of matrix metalloproteinases, tyrosinase activity, and melanin production. Additionally, zebrafish-based assays provided in vivo evidence of the skincare efficacy of SA-NLPs. Notably, clinical evaluations demonstrated that a 56-day application of the SA-NLPs-containing cream resulted in a 4.20% increase in L*, 7.87% decrease in b*, 8.45% decrease in TEWL, and 4.01% reduction in wrinkle length, indicating its superior brightening, barrier-repair, and anti-aging effects. Conclusions: This multi-level, systematic investigation strongly suggests that SA-NLPs represent a highly promising transdermal delivery strategy, capable of significantly enhancing the anti-aging, barrier-repair, and skin-brightening properties of SA, thus opening new avenues for its application in the fields of dermatology and cosmeceuticals. Full article
(This article belongs to the Special Issue Lipid/Polymer-Based Drug Delivery Systems)
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15 pages, 1275 KiB  
Systematic Review
A Systematic Review of Closed-Incision Negative-Pressure Wound Therapy for Hepato-Pancreato-Biliary Surgery: Updated Evidence, Context, and Clinical Implications
by Catalin Vladut Ionut Feier, Vasile Gaborean, Ionut Flaviu Faur, Razvan Constantin Vonica, Alaviana Monique Faur, Vladut Iosif Rus, Beniamin Sorin Dragan and Calin Muntean
J. Clin. Med. 2025, 14(15), 5191; https://doi.org/10.3390/jcm14155191 - 22 Jul 2025
Viewed by 296
Abstract
Background and Objectives: Postoperative pancreatic fistula and post-hepatectomy liver failure remain significant complications after HPB surgery; however, superficial surgical site infection (SSI) is the most frequent wound-related complication. Closed-incision negative-pressure wound therapy (ciNPWT) has been proposed to reduce superficial contamination, yet no [...] Read more.
Background and Objectives: Postoperative pancreatic fistula and post-hepatectomy liver failure remain significant complications after HPB surgery; however, superficial surgical site infection (SSI) is the most frequent wound-related complication. Closed-incision negative-pressure wound therapy (ciNPWT) has been proposed to reduce superficial contamination, yet no liver-focused quantitative synthesis exists. We aimed to evaluate the effectiveness and safety of prophylactic ciNPWT after hepatopancreatobiliary (HPB) surgery. Methods: MEDLINE, Embase, and PubMed were searched from inception to 30 April 2025. Randomized and comparative observational studies that compared ciNPWT with conventional dressings after elective liver transplantation, hepatectomy, pancreatoduodenectomy, and liver resections were eligible. Two reviewers independently screened, extracted data, and assessed risk of bias (RoB-2/ROBINS-I). A random-effects Mantel–Haenszel model generated pooled risk ratios (RRs) for superficial SSI; secondary outcomes were reported descriptively. Results: Twelve studies (seven RCTs, five cohorts) encompassing 15,212 patients (3561 ciNPWT; 11,651 control) met the inclusion criteria. Device application lasted three to seven days in all trials. The pooled analysis demonstrated a 29% relative reduction in superficial SSI with ciNPWT (RR 0.71, 95% CI 0.63–0.79; p < 0.001) with negligible heterogeneity (I2 0%). Absolute risk reduction ranged from 0% to 13%, correlating positively with the baseline control-group SSI rate. Deep/organ-space SSI (RR 0.93, 95% CI 0.79–1.09) and 90-day mortality (RR 0.94, 95% CI 0.69–1.28) were unaffected. Seven studies documented a 1- to 3-day shorter median length of stay; only two reached statistical significance. Device-related adverse events were rare (one seroma, no skin necrosis). Conclusions: Prophylactic ciNPWT safely reduces superficial SSI after high-risk HPB surgery, with the greatest absolute benefit when baseline SSI risk exceeds ≈10%. Its influence on deep infection and mortality is negligible. Full article
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40 pages, 1777 KiB  
Review
Nanomaterials for Direct Air Capture of CO2: Current State of the Art, Challenges and Future Perspectives
by Cataldo Simari
Molecules 2025, 30(14), 3048; https://doi.org/10.3390/molecules30143048 - 21 Jul 2025
Viewed by 295
Abstract
Direct Air Capture (DAC) is emerging as a critical climate change mitigation strategy, offering a pathway to actively remove atmospheric CO2. This comprehensive review synthesizes advancements in DAC technologies, with a particular emphasis on the pivotal role of nanostructured solid sorbent [...] Read more.
Direct Air Capture (DAC) is emerging as a critical climate change mitigation strategy, offering a pathway to actively remove atmospheric CO2. This comprehensive review synthesizes advancements in DAC technologies, with a particular emphasis on the pivotal role of nanostructured solid sorbent materials. The work critically evaluates the characteristics, performance, and limitations of key nanomaterial classes, including metal–organic frameworks (MOFs), covalent organic frameworks (COFs), zeolites, amine-functionalized polymers, porous carbons, and layered double hydroxides (LDHs), alongside solid-supported ionic liquids, highlighting their varied CO2 uptake capacities, regeneration energy requirements, and crucial water sensitivities. Beyond traditional temperature/pressure swing adsorption, the review delves into innovative DAC methodologies such as Moisture Swing Adsorption (MSA), Electro Swing Adsorption (ESA), Passive DAC, and CO2-Binding Organic Liquids (CO2 BOLs), detailing their unique mechanisms and potential for reduced energy footprints. Despite significant progress, the widespread deployment of DAC faces formidable challenges, notably high capital and operational costs (currently USD 300–USD 1000/tCO2), substantial energy demands (1500–2400 kWh/tCO2), water interference, scalability hurdles, and sorbent degradation. Furthermore, this review comprehensively examines the burgeoning global DAC market, its diverse applications, and the critical socio-economic barriers to adoption, particularly in developing countries. A comparative analysis of DAC within the broader carbon removal landscape (e.g., CCS, BECCS, afforestation) is also provided, alongside an address to the essential, often overlooked, environmental considerations for the sustainable production, regeneration, and disposal of spent nanomaterials, including insights from Life Cycle Assessments. The nuanced techno-economic landscape has been thoroughly summarized, highlighting that commercial viability is a multi-faceted challenge involving material performance, synthesis cost, regeneration energy, scalability, and long-term stability. It has been reiterated that no single ‘best’ material exists, but rather a portfolio of technologies will be necessary, with the ultimate success dependent on system-level integration and the availability of low-carbon energy. The review paper contributes to a holistic understanding of cutting-edge DAC technologies, bridging material science innovations with real-world implementation challenges and opportunities, thereby identifying critical knowledge gaps and pathways toward a net-zero carbon future. Full article
(This article belongs to the Special Issue Porous Carbon Materials: Preparation and Application)
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21 pages, 3490 KiB  
Article
Energy-Efficient CO2 Conversion for Carbon Utilization Using a Gliding Arc/Glow Discharge with Magnetic Field Acceleration—Optimization and Characterization
by Svetlana Lazarova, Snejana Iordanova, Stanimir Kolev, Veselin Vasilev and Tsvetelina Paunska
Energies 2025, 18(14), 3816; https://doi.org/10.3390/en18143816 - 17 Jul 2025
Viewed by 289
Abstract
The dry conversion of CO2 into CO and O2 provides an attractive path for CO2 utilization which allows for the use of the CO produced for the synthesis of valuable hydrocarbons. In the following work, the CO2 conversion is [...] Read more.
The dry conversion of CO2 into CO and O2 provides an attractive path for CO2 utilization which allows for the use of the CO produced for the synthesis of valuable hydrocarbons. In the following work, the CO2 conversion is driven by an arc discharge at atmospheric pressure, producing hot plasma. This study presents a series of experiments aiming to optimize the process. The results obtained include the energy efficiency and the conversion rate of the process, as well as the electrical parameters of the discharge (current and voltage signals). In addition, optical emission spectroscopy diagnostics based on an analysis of C2’s Swan bands are used to determine the gas temperature in the discharge. The data is analyzed according to several aspects—an analysis of the arc’s motion based on the electrical signals; an analysis of the effect of the gas flow and the discharge current on the discharge performance for CO2 conversion; and an analysis of the vibrational and rotational temperatures of the arc channel. The results show significant improvements over previous studies. Relatively high gas conversion and energy efficiency are achieved due to the arc acceleration caused by the Lorentz force. The rotational (gas) temperatures are in the order of 5500–6000 K. Full article
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21 pages, 4609 KiB  
Review
Covalent Organic Framework Membranes for Ion Separation: A Review
by Yutong Lou, Zhanyong Wang, Wanbei Yang, Shuchen Lang, Jiaxing Fan, Qiaomei Ke, Rui Wang, Zhen Zhang, Wentao Chen and Jian Xue
Membranes 2025, 15(7), 211; https://doi.org/10.3390/membranes15070211 - 15 Jul 2025
Viewed by 573
Abstract
Covalent organic framework (COF) membranes have garnered significant attention in ion separation due to their high surface area, tunable pore size, excellent stability, and diverse functional groups. Over the past decade, various synthesis methods, such as solvothermal synthesis, interfacial synthesis, microwave-assisted solvothermal synthesis, [...] Read more.
Covalent organic framework (COF) membranes have garnered significant attention in ion separation due to their high surface area, tunable pore size, excellent stability, and diverse functional groups. Over the past decade, various synthesis methods, such as solvothermal synthesis, interfacial synthesis, microwave-assisted solvothermal synthesis, and in situ growth, have been developed to fabricate COF membranes. COF membranes have demonstrated remarkable ion separation performance in different separation processes driven by pressure, electric field, and vapor pressure difference, showing great potential in a wide range of applications. Nevertheless, challenges in the synthesis and application of COF membranes still remain, requiring further research to fully realize their potential in ion separation. This review critically examines the development of COF membranes, from synthesis methods to ion separation applications. We evaluate the advantages and limitations of various synthesis techniques and systematically summarize COF membrane performance based on separation driving forces. Finally, we present a critical analysis of current challenges and offer perspectives on promising future research directions for advancing COF membrane technology in separation. Full article
(This article belongs to the Section Membrane Applications for Water Treatment)
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20 pages, 3537 KiB  
Article
A New Sulfur-Containing Copolymer Created Through the Thermally Induced Radical Copolymerization of Elemental Sulfur with N2,N2-Diallylmelamine Comonomer for Potential CO2 Capture
by Dharrinesh Narendiran, Nurul Hazirah Sumadi, Ali Shaan Manzoor Ghumman, Noor Ashikin Mohamad, Mohamed Mahmoud Nasef, Amin Abbasi and Rashid Shamsuddin
J. Compos. Sci. 2025, 9(7), 362; https://doi.org/10.3390/jcs9070362 - 11 Jul 2025
Viewed by 391
Abstract
Sulfur-containing polymers are unique sustainable materials with promise for the development of various adsorbents for environmental remediation. However, they have not been explored for CO2 capture despite reports on its ability to decontaminate various aqueous pollutants. This study reports on the single-step [...] Read more.
Sulfur-containing polymers are unique sustainable materials with promise for the development of various adsorbents for environmental remediation. However, they have not been explored for CO2 capture despite reports on its ability to decontaminate various aqueous pollutants. This study reports on the single-step synthesis of a diamine-functionalized sulfur-containing copolymer by the thermally induced radical copolymerization of N2,N2-Diallylmelamine (NDAM), a difunctional monomer, with sulfur and explores its use for CO2 capture. The influence of reaction parameters such as the weight ratios of sulfur to NDAM, reaction temperature, time, and the addition of a porogen on the properties of aminated copolymer was investigated. The resulting copolymers were characterized using FTIR, TGA, DSC, SEM, XRD, and BET surface area analyses. The incorporation of NDAM directly imparted amine functionality while stabilizing the polysulfide chains by crosslinking, leading to a thermoset copolymer with an amorphous structure. The addition of a NaCl particle porogen to the S/NDAM mixture generated a mesoporous structure, enabling the resulting copolymer to be tested for CO2 adsorption under varying pressures, leading to an adsorption capacity as high as 517 mg/g at 25 bar. This work not only promotes sustainable hybrid materials that advance green chemistry while aiding CO2 mitigation efforts but also adds value to the abundant amount of sulfur by-products from petroleum refineries. Full article
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16 pages, 3015 KiB  
Article
Energy Efficiency Analysis of Hydraulic Excavators’ Swing Drive Transmission
by Vesna Jovanović, Dragoslav Janošević, Dragan Marinković, Nikola Petrović and Boban Nikolić
Machines 2025, 13(7), 596; https://doi.org/10.3390/machines13070596 - 10 Jul 2025
Viewed by 251
Abstract
The paper provides an analysis of the energy efficiency of the swing drive system of hydraulic excavators, which integrally includes a hydraulic motor and a planetary reducer. The indicator of the drive’s energy efficiency is determined based on the efficiency of the hydraulic [...] Read more.
The paper provides an analysis of the energy efficiency of the swing drive system of hydraulic excavators, which integrally includes a hydraulic motor and a planetary reducer. The indicator of the drive’s energy efficiency is determined based on the efficiency of the hydraulic motor and the planetary reducer. The efficiency of the hydraulic motor is defined as a function of the specific flow, pressure, and the number of revolutions of the hydraulic motor. The efficiency of the reducer is determined using structural analysis of planetary gearboxes and the moment method. As an example, the results of a comparative analysis of the energy efficiency of the swing drive of a tracked hydraulic excavator, weighing 16,000 kg and having a bucket volume of 0.6 m3, are presented. From the set of possible generated variant solutions of the drive, obtained through the synthesis process based on the required torque and platform rotation speed, two extreme drive variants were selected for the analysis. In the first configuration, a hydraulic motor characterized by a low specific flow is combined with a three-stage reduction gear featuring a higher overall transmission ratio, whereas the second configuration integrates a high-specific-flow hydraulic motor with a two-stage reduction gear of a lower transmission ratio. The obtained results of the comparative analysis of the drive’s energy efficiency are presented depending on the change in the required torque and the rotational speed of the platform. Full article
(This article belongs to the Special Issue Components of Hydrostatic Drive Systems)
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23 pages, 2710 KiB  
Review
Recent Advances in Chemical Vapor Deposition of Hexagonal Boron Nitride on Insulating Substrates
by Hua Xu, Kai Li, Zuoquan Tan, Jiaqi Jia, Le Wang and Shanshan Chen
Nanomaterials 2025, 15(14), 1059; https://doi.org/10.3390/nano15141059 - 8 Jul 2025
Viewed by 567
Abstract
Direct chemical vapor deposition (CVD) growth of hexagonal boron nitride (h-BN) on insulating substrates offers a promising pathway to circumvent transfer-induced defects and enhance device integration. This comprehensive review systematically evaluates recent advances in CVD techniques for h-BN synthesis on insulating substrates, including [...] Read more.
Direct chemical vapor deposition (CVD) growth of hexagonal boron nitride (h-BN) on insulating substrates offers a promising pathway to circumvent transfer-induced defects and enhance device integration. This comprehensive review systematically evaluates recent advances in CVD techniques for h-BN synthesis on insulating substrates, including metal–organic CVD (MOCVD), low-pressure CVD (LPCVD), atmospheric-pressure CVD (APCVD), and plasma-enhanced CVD (PECVD). Key challenges, including precursor selection, high-temperature processing, achieving single-crystalline films, and maintaining phase purity, are critically analyzed. Special emphasis is placed on comparative performance metrics across different growth methodologies. Furthermore, crucial research directions for future development in this field are outlined. This review aims to serve as a reference for advancing h-BN synthesis toward practical applications in next-generation electronic and optoelectronic devices. Full article
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22 pages, 2989 KiB  
Article
Preparation and Screening of Ni-Based Catalysts for the Olive Oil Mill Wastewater Steam Reforming Process
by Cláudio Rocha, Miguel A. Soria and Luís M. Madeira
Catalysts 2025, 15(7), 654; https://doi.org/10.3390/catal15070654 - 4 Jul 2025
Viewed by 356
Abstract
Olive mill wastewater (OMW) is a highly polluting effluent rich in organic pollutant compounds derived from olive oil production. In this work, the steam reforming reaction of OMW (OMWSR) was performed in a traditional reactor at 400 °C and different pressures (1–4 bar) [...] Read more.
Olive mill wastewater (OMW) is a highly polluting effluent rich in organic pollutant compounds derived from olive oil production. In this work, the steam reforming reaction of OMW (OMWSR) was performed in a traditional reactor at 400 °C and different pressures (1–4 bar) to treat and valorize this effluent. A commercial catalyst (Rh/Al2O3) was used as a reference sample and several new catalysts were prepared (Ni-Ru/Ce-SiO2) using different preparation methods to study their effect on the activity and stability. The best-performing catalysts were also subjected to long-term operation experimental tests (24 h). It was observed that the preparation method used for the catalysts synthesis influenced the catalytic performance of the samples. In addition, temperature-programmed oxidation (TPO) analysis of the used catalyst showed the presence of carbon deposits: the results showed that periodic oxidative regeneration improved the catalyst stability and sustained H2 production. Finally, it was verified that the Ni-Ru/Ce3 catalyst stood out during the experimental tests, exhibiting high catalytic activity along the stability test at 400 °C and 1 bar: H2 yield always over 7 molH2·molOMW−1 and total organic carbon (TOC) conversion always higher than 94%. Despite these promising results, further research is needed to assess the economic feasibility of scaling up the process. Additionally, future work could explore the development of catalysts with enhanced resistance to deactivation by carbon deposition. Full article
(This article belongs to the Special Issue Green Chemistry and Catalysis)
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22 pages, 3063 KiB  
Article
High-Temperature Methane Sensors Based on ZnGa2O4:Er Ceramics for Combustion Monitoring
by Aleksei V. Almaev, Zhakyp T. Karipbayev, Askhat B. Kakimov, Nikita N. Yakovlev, Olzhas I. Kukenov, Alexandr O. Korchemagin, Gulzhanat A. Akmetova-Abdik, Kuat K. Kumarbekov, Amangeldy M. Zhunusbekov, Leonid A. Mochalov, Ekaterina A. Slapovskaya, Petr M. Korusenko, Aleksandra V. Koroleva, Evgeniy V. Zhizhin and Anatoli I. Popov
Technologies 2025, 13(7), 286; https://doi.org/10.3390/technologies13070286 - 4 Jul 2025
Viewed by 342
Abstract
The use of CH4 as an energy source is increasing every day. To increase the efficiency of CH4 combustion and ensure that the equipment meets ecological requirements, it is necessary to measure the CH4 concentration in the exhaust gases of [...] Read more.
The use of CH4 as an energy source is increasing every day. To increase the efficiency of CH4 combustion and ensure that the equipment meets ecological requirements, it is necessary to measure the CH4 concentration in the exhaust gases of combustion systems. To this end, sensors are required that can withstand extreme operating conditions, including temperatures of at least 600 °C, as well as high pressure and gas flow rate. ZnGa2O4, being an ultra-wide bandgap semiconductor with high chemical and thermal stability, is a promising material for such sensors. The synthesis and investigation of the structural and CH4 sensing properties of ceramic pellets made from pure and Er-doped ZnGa2O4 were conducted. Doping with Er leads to the formation of a secondary Er3Ga5O12 phase and an increase in the active surface area. This structural change significantly enhanced the CH4 response, demonstrating an 11.1-fold improvement at a concentration of 104 ppm. At the optimal response temperature of 650 °C, the Er-doped ZnGa2O4 exhibited responses of 2.91 a.u. and 20.74 a.u. to 100 ppm and 104 ppm of CH4, respectively. The Er-doped material is notable for its broad dynamic range for CH4 concentrations (from 100 to 20,000 ppm), low sensitivity to humidity variations within the 30–70% relative humidity range, and robust stability under cyclic gas exposure. In addition to CH4, the sensitivity of Er-doped ZnGa2O4 to other gases at a temperature of 650 °C was investigated. The samples showed strong responses to C2H4, C3H8, C4H10, NO2, and H2, which, at gas concentrations of 100 ppm, were higher than the response to CH4 by a factor of 2.41, 2.75, 3.09, 1.16, and 1.64, respectively. The study proposes a plausible mechanism explaining the sensing effect of Er-doped ZnGa2O4 and discusses its potential for developing high-temperature CH4 sensors for applications such as combustion monitoring systems and determining the ideal fuel/air mixture. Full article
(This article belongs to the Section Innovations in Materials Science and Materials Processing)
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26 pages, 1964 KiB  
Review
Food Waste Anaerobic Digestion Under High Organic Loading Rate: Inhibiting Factors, Mechanisms, and Mitigation Strategies
by Hong-Ming Wu, Xiang Li, Jia-Ning Chen, Yi-Juan Yan, Takuro Kobayashi, Yong Hu and Xueying Zhang
Processes 2025, 13(7), 2090; https://doi.org/10.3390/pr13072090 - 1 Jul 2025
Viewed by 404
Abstract
Anaerobic digestion (AD) for food waste (FW) treatment has faced many challenges, especially ammonia nitrogen, acid, and salinity inhibition at a high organic loading rate (OLR). Therefore, a systematic understanding of the issues arising during the FW AD process is a necessity under [...] Read more.
Anaerobic digestion (AD) for food waste (FW) treatment has faced many challenges, especially ammonia nitrogen, acid, and salinity inhibition at a high organic loading rate (OLR). Therefore, a systematic understanding of the issues arising during the FW AD process is a necessity under a high OLR (over 3 g-VS/L d). Primarily, in terms of ammonia nitrogen inhibition, ammonia ions inhibit methane synthesis enzymes, and free ammonia (FAN) contributes to the imbalance of microbial protons. Regulation strategies include substrate C/N ratio regulation, microbial domestication, and ammonia nitrogen removal. In addition, with regard to acid inhibition, including volatile fatty acid (VFA) and long-chain fatty acid (LCFA) accumulation, the elevated acid concentration can contribute to reactive oxygen species stress, and a solution to this includes the addition of alkaline agents and trace elements or the use of microbial electrochemical and biofortification technology and micro-aeration-based AD technology. Furthermore, in terms of salinity inhibition, high salinity can result in a rapid increase in cell osmotic pressure, which can cause cell rupture, and water washing and bio-electrochemical AD are defined as solutions. Future research directions are proposed, mainly in terms of avoiding the introduction of novel containments into these regulation strategies and applying them in large-scale AD plants under a high OLR. Full article
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16 pages, 1733 KiB  
Article
Comprehensive Analysis of Formation Water Microorganisms for Their Biosurfactant Potential in MEOR Applications
by Gulzhan Kaiyrmanova, Ulzhan Shaimerdenova, Alisher Assylbek, Almira Amirgaliyeva, Arailym Yerzhan and Aliya Yernazarova
Fermentation 2025, 11(7), 367; https://doi.org/10.3390/fermentation11070367 - 26 Jun 2025
Viewed by 482
Abstract
The study is devoted to the analysis of the physicochemical parameters of formation waters, the metagenomic composition of the microbial community and the characteristics of bacterial isolates from the oil fields of Western Kazakhstan to assess their potential in microbial-enhanced oil recovery (MEOR) [...] Read more.
The study is devoted to the analysis of the physicochemical parameters of formation waters, the metagenomic composition of the microbial community and the characteristics of bacterial isolates from the oil fields of Western Kazakhstan to assess their potential in microbial-enhanced oil recovery (MEOR) technologies. Analyses revealed an adaptation of local microorganisms to extreme conditions of high salinity, temperature and pressure, with the dominant presence of Proteobacteria, including the genus Marinobacter. Screening isolates for biosurfactant synthesis showed a high activity of strains M22-7, M93-8C and M142-2, capable of reducing surface tension to 28.81 ± 0.6 mN/m and forming emulsions. Genetic analysis confirmed the presence of key genes (srfAA, srfp) responsible for surfactin synthesis, but the absence of lchAA and rhlAA indicates that the synthesis of other types of biosurfactants is limited. The results highlight the promise of developing microbial consortia and using biosurfactants in high-salinity environments to enhance oil recovery. Full article
(This article belongs to the Section Industrial Fermentation)
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12 pages, 5865 KiB  
Article
Recovery of Titanium and Aluminum from Secondary Waste Solutions via Ultrasonic Spray Pyrolysis
by Srećko Stopić, Duško Kostić, Vladimir Damjanović, Mitar Perušić, Radislav Filipović, Nenad Nikolić and Bernd Friedrich
Metals 2025, 15(7), 701; https://doi.org/10.3390/met15070701 - 24 Jun 2025
Viewed by 306
Abstract
The synthesis of oxide nanopowders through ultrasonic spray pyrolysis (USP) represents a sustainable method for producing high-purity, spherical particles tailored for advanced material applications. Recent developments in USP synthesis leverage the continuous transport of aerosols from an ultrasonic generator to a high-temperature furnace, [...] Read more.
The synthesis of oxide nanopowders through ultrasonic spray pyrolysis (USP) represents a sustainable method for producing high-purity, spherical particles tailored for advanced material applications. Recent developments in USP synthesis leverage the continuous transport of aerosols from an ultrasonic generator to a high-temperature furnace, with nanopowders collected efficiently using an electrostatic precipitator. This study explored the use of USP for titanium oxysulfate and aluminum nitrate solutions derived from the aluminum industry, focusing on resource recovery and waste reduction. Titanium oxysulfate was synthesized by leaching slag, generated during the reduction of red mud, with sulfuric acid under oxidizing, high-pressure conditions. After purification, the titanium oxysulfate solution was processed using USP in a hydrogen reduction atmosphere to yield spherical titanium dioxide (TiO2) nanopowders. The hydrogen atmosphere enabled precise control over the nanoparticles’ morphology and crystallinity, enhancing their suitability for use in applications such as photocatalysis, pigments, and advanced coatings. In parallel, both synthetic and laboratory solutions of aluminum nitrate [Al(NO3)3] were prepared. The laboratory solution was prepared by leaching aluminum hydroxide oxide (AlOOH) with hydrochloric acid to form aluminum chloride (AlCl3), followed by a conversion to aluminum nitrate through the addition of nitric acid. The resulting aluminum nitrate solution was subjected to USP, producing highly uniform, spherical alumina (Al2O3) nanopowders with a narrow size distribution. The resulting nanopowders, characterized by their controlled properties and potential applicability, represent an advancement in oxide powder synthesis and resource-efficient manufacturing techniques. Full article
(This article belongs to the Special Issue Advances in Recycling of Valuable Metals—2nd Edition)
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