Search Results (71)

The disposal of low-level and intermediate-level radioactive solid waste has aroused widespread concern. In this work, the pyrolysis characterizations of simulated radioactive solid waste, cotton gloves (CG), stain removal cloths (SRC), plastic bags (PB), shoe covers (SC), and ion exchange resins (IER), were analyzed using thermogravimetric analysis, Thermogravimetric–Fourier Transform Infrared Spectrometry–Mass Spectrometry (TG-FTIR-MS) and Pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS). The main mass loss stages of CG, SRC, PB, SC, and IER were 240–500 °C, 210–500 °C, 400–550 °C, 180–610 °C, and 25–700 °C, respectively. The average activation energies calculated by three iso-conversional methods were 184.09–211.46 kJ/mol, 172.33–180.85 kJ/mol, 264.63–268.01 kJ/mol, 150.49–184.36 kJ/mol, and 150.72–151.66 kJ/mol, respectively. Pyrolysis of CG and SRC mainly produced CO₂ and oxygenated compounds. SC generated large amounts of HCl during pyrolysis. Combined with rapid pyrolysis analysis, it was shown that CG and SRC mainly produced carbohydrates, aliphatic hydrocarbons, and aromatics. The pyrolysis products of SC mainly consisted of aliphatic hydrocarbons, aromatics, and acids. The pyrolysis products of PB were mainly olefins and alcohols. IER produced large amounts of aromatics during rapid pyrolysis. Specifically, the pyrolysis of IER generated some SO₂. This work provides a theoretical basis and data support for the treatment of mixed combustible radioactive waste. Full article

Understanding the dynamics of sorption and desorption is essential for assessing the persistence and mobility of pesticides. These processes continue to influence ecological outcomes even after pesticide use has ended, as demonstrated by our study on dimethoate behavior in distinct soil samples from Croatia, including coastal, lowland, and mountainous regions. This study focuses on the sorption/desorption behavior of dimethoate in soil, explores the relationship between its molecular structure and the properties of soil organic and inorganic matter, and evaluates the mechanisms of the sorption/desorption process. The behavior of dimethoate was analyzed using a batch method, and the results were modeled using nonlinear equilibrium models: Freundlich, Langmuir, and Temkin models. Soils with a higher organic matter content, especially total organic carbon (TOC), showed a better sorption capacity compared to soils with a lower TOC. This is probably due to the less flexible structures in the glassy phase, which, unlike the rubbery phase in high TOC soils, do not allow dynamic and flexible binding of dimethoate within the organic matter. The differences between the H/C and O/C ratios indicate that in high TOC soils, flexible aliphatic compounds, typical of a rubbery phase, retain dimethoate more effectively, whereas a higher content of oxygen-containing functional groups in low TOC soils provides strong association. The lettered soils showed stronger retention of dimethoate through interactions with clay minerals and metal cations such as Mg²⁺, suggesting that clay plays a significantly more important role in enhancing dimethoate sorption than organic matter. These results highlight the importance of organic matter, clay, and metal ions in the retention of dimethoate in soil, indicating the need for remediation methods for those pesticides that, although banned, have had a long history of use. Full article

Humic acids (HAs) possess diverse functionalities, endowing them with multiple applications as bioactive compounds in agriculture. Alkaline extraction is key to obtaining HAs from their source material. The presence of oxygen during extraction can lead to oxidative changes in the humic structure. The extent of HA transformation depending on their origin remains poorly understood, and the effect of alkaline extraction on the HA biological activities is yet to be estimated. Here, we compare the physicochemical properties of HAs extracted from fresh organic material, compost, in air (HA-O₂) and under nitrogen (HA-N₂). We also assess the antioxidant properties of HAs-O₂ and HAs-N₂ from compost (HAC), Retisol (HAR), and Chernozem (HACh) and relate them to the HA biological activities. Changes in the HAC properties were analyzed using the following techniques: elemental composition, ultraviolet–visible and infrared spectroscopy, ¹³C nuclear magnetic resonance (¹³C-NMR), electron paramagnetic resonance (EPR), gel filtration using Sephadex G-75 gel, and potentiometric titration. The HA antioxidant properties were explored using the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) assay (antiradical activity) and phosphomolybdenum assay (total antioxidant capacity). The HA biological activity was estimated by priming radish and wheat seeds (0.5 g L⁻¹ HAs, 25 °C, 5 h for radish and 14 h for wheat), followed by germination tests. Alkaline extraction of HAC in air vs. nitrogen resulted in a 1.2-fold increase in the O/C ratio and optical density at E₄₆₅, oxidation of aliphatic fragments, a 2-fold increase in the contents of functional groups, and a 1.2-fold increase in the number of paramagnetic centers. All HA-O₂ preparations have demonstrated an enhanced antiradical activity (1.3–1.6 times) and total antioxidant capacity (1.1–1.3 times) compared to HA-N₂. The Vigor Index of seeds primed with HA-O₂ was 1.1-to-1.8-fold higher than those treated with HA-N₂, depending on the HA origin. We demonstrate that alkaline treatment in air benefits the antiradical and biological activities of HAs, making such preparations more attractive for use as natural antioxidants and priming agents. This opens up new perspectives for using O₂-modified HAs as innovative plant stimulants in agriculture. Full article

The Konduyak gold–quartz–sulfide deposit is one of the most promising gold mines in the Ayakhta gold ore cluster on the Yenisei ridge. This article is devoted to the study of the composition of the volatile compounds in the ore-forming fluid, since this is one of the key aspects in understanding the conditions of deposit formation. The compositions of the fluids that formed quartz and pyrite in the deposit ore zone were determined using Raman spectroscopy and pyrolysis-free gas chromatography–mass spectrometry. The study of the fluid inclusions in the minerals showed that complex C-H-O-S-N multi-component fluids formed the quartz–sulfide ore zones. A range of 232 to 302 various volatile compounds were found in the fluids. The mineralizing fluids mainly consist of H₂O (14.25–96.02 rel. %) and CO₂ (2.07–54.44 rel. %). A high SO₂ content (14.60–44.95 rel. %) is typical of fluids trapped by pyrites. Moreover, a wide range of hydrocarbons (oxygen-free aliphatic, cyclic, heterocyclic, and oxygenated) and nitrogenated and sulfur compounds were found among the volatiles in the fluid. The variable H/(H + O) ratios, from 0.51 to 0.81, and CO₂/(CO₂ + H₂O) ratios, from 0.02 to 0.56, indicate changes in the redox conditions during ore formation. Full article

N-containing carbon-based materials have been employed with claimed improved performance as an adsorbent of acidic molecules, volatile organic compounds (VOC), and metallic ions; catalyst; electrocatalyst; and supercapacitor. In this context, the present work provides valuable insights into the preparation of N-doped activated carbons (ACs) by thermal treatment in NH₃ atmosphere (ammonization). A commercial AC was submitted to two kinds of pretreatment: (i) reflux with dilute HNO₃; (ii) thermal treatment up to 800 °C in inert atmosphere. The original and modified ACs were subjected to ammonization up to different temperatures. ACs with N content up to ~8% were achieved. Nevertheless, the amount and type of inserted nitrogen depended on ammonization temperature and surface composition of the starting material. Remarkably, oxygenated acidic groups on the surface of the starting material favored nitrogen insertion at low temperatures, with formation of mostly aliphatic (amines, imides, and lactams), pyridinic, and pyrrolic nitrogens. In turn, high temperatures provoked the decomposition of labile aliphatic functions. Therefore, the AC prepared from the sample pre-treated with HNO₃, which had the highest content of oxygenated acidic groups among the materials submitted to ammonization, presented the highest N content after ammonization up to 400 °C but the lowest content after ammonization up to 800 °C. Full article

Soluble organics (SBC-L) from Santanghu bituminous coal (SBC) were obtained by extracting the coal with a mixed solvent of CS₂ and acetone (v/v′ = 1:1). Catalytic hydrogenation of SBC-L was carried out using isopropanol as the solvent and prepared bimetallic material (Ni-Mo/γ-Al₂O₃) as the catalyst, and the hydrogenation product (SBC-L_IP320) was obtained. Gas chromatography-mass spectrometry (GC-MS) was used to compare the difference in the composition and distribution of SBC-L and SBC-L_IP320; thus, the effect of the used catalyst on the hydrogenation performance and heteroatom removal of SBC-L can be investigated. Results showed that the organic compounds in SBC-L and SBC-L_IP320 could be classified into aliphatic hydrocarbons (AHS), arenes, oxygen-containing organic compounds (OCOCs), nitrogen-containing organics (NCOCs), and compounds containing other heteroatoms (OHACOCs). The relative contents of AHS and arenes detected in SBC-L_IP320 were higher than those of SBC-L, while the contents of OCOCs, NCOCs, and OHACOCs decreased, and no S-containing compounds could be detected in SBC-L_IP320. It can be concluded that the prepared catalyst presents good de-oxygenation, de-sulfurization, de-nitrogenation, and hydrocracking performance. Full article

ROS (i.e., reactive oxygen species) scavenging is a key function of various Mn-based enzymes, including superoxide dismutases (SODs) and catalases, which are actively linked to oxidative stress-related diseases. In this study, we synthesized and characterized two novel Mn(III)-based synzymes (i.e., synthetic enzymes), designated C1 ([MnL1Cl(H₂O)]Cl·3H₂O) and C2 ([MnL2Cl₂]·2H₂O), which differ in the presence of a bridging aliphatic or aromatic group in the chelator. Using a range of analytical techniques, we found that the aromatic C2 bridge significantly influences the Mn(III) center’s cis-β configuration, unlike C1, which adopts a trans configuration. We then thoroughly evaluated the oxidation-reduction properties of C1 and C2, including their redox potentials (by cyclic voltammetry) and capacity to consume various ROS species (using DPPH, hydroxyl radical, hydrogen peroxide, and superoxide UV–visible spectrophotometric assays). The specific kinetics of the H₂O₂ dismutation process, as measured by a Clark-type electrode and time-resolved ESI-MS, revealed that both synzymes possess catalytic activity. Toxicological experiments using the Galleria mellonella larval model demonstrated the compounds’ innocuous nature towards higher eukaryotic organisms, while cytotoxicity assays confirmed their selective efficacy against lung cancer cells. Additional cytological assays, such as the thiobarbituric acid reactive substances assay and caspase-3 activity and p53 expression analysis, reported that C1 and C2 induce cytotoxicity against cancer cells via apoptosis rather than necrosis and behave very differently towards redox substances and ROS-regulating enzymes in vivo. These findings suggest that the structural differences between C1 and C2 lead to distinct redox properties and biological activities, highlighting the potential of these novel Mn(III)-based synzymes as therapeutic agents for the treatment of oxidative stress-related diseases, particularly lung cancer. Further studies are warranted to elucidate the underlying mechanisms of action and explore their clinical applications. Full article

As a common necessity, masks have been used a lot in recent years, and the comprehensive utilization of waste masks has become a research priority in the post-COVID-19 pandemic era. However, traditional disposal methods suffer from a range of problems, including poor utilization and insecurity. To explore new solution ideas and efficiently utilize waste resources, waste masks and biomass wastes were used as raw materials to prepare mask-based biochar (WMB), bio-oil, and pyrolytic gas via oxygen-limited co-pyrolysis in this study. The obtained solid–liquid–gas product was systematically characterized to analyze the physicochemical properties, and the adsorption properties and mechanisms of WMB on the environmental endocrine bisphenol A (BPA) were investigated. The co-pyrolysis mechanisms were also studied in depth. Furthermore, the strengths and weaknesses of products prepared by co-pyrolysis and co-hydrothermal synthesis were discussed in comparison. The results indicated that the waste masks could shape the microsphere structure, leading to richer surface functional groups and stable mesoporous of WMB. Here, the risk of leaching of secondary pollutants was not detected. The theoretical maximum adsorption of BPA by WMB was 28.73 mg·g⁻¹. The Langmuir and Pseudo-second-order models optimally simulated the isothermal and kinetic adsorption processes, which are a composite of physicochemical adsorption. Simultaneous pyrolysis of mask polymers with biomass polymers produces bio-oil and pyrolytic gas, which is rich in high-quality aliphatic and aromatic compounds. This could have potential as an energy source or chemical feedstock. The co-pyrolysis mechanisms may involve the depolymerization of waste masks to produce hydrocarbons and H radicals, which in turn undergo multi-step cleavage and oligomerization reactions with biomass derivatives. It is recommended to use the co-pyrolysis method to dispose of waste masks, as the products obtained are significantly better than those obtained by the co-hydrothermal method. This work provides a new contribution to the resourcing of waste masks into high-quality products. Full article

The chemical composition of Sedum ewersii Ledeb., a plant indigenous to Kazakhstan and traditionally utilized in folk medicine, was comprehensively investigated, with a focus on its various plant parts. Fresh samples collected in May 2023 from the Almaty region underwent hydrodistillation to extract volatile components, followed by analysis using gas chromatography coupled with mass spectrometric detection, which identified a total of 71 compounds across different plant parts, including the root (underground part), root (aerial part), leaf, stem, and flowering aerial part. The predominant biologically active compound identified across all plant parts was Ethyl α-D-glucopyranoside. Monoterpenes, recognized as primary secondary metabolites, were notably abundant in each plant part, with varying compositions: the root (underground part) contained 28.58% aliphatic monoterpenes, 54.41% oxygenated monoterpenoids, 1.42% diterpenoids, and 15.59% other compounds; the root (aerial part) exhibited 1.34% aliphatic monoterpenes, 31.28% oxygenated monoterpenoids, 6.16% diterpenoids, and 61.22% other compounds; the stem and leaves showed 3.06% aliphatic monoterpenes, 21.49% oxygenated monoterpenoids, 17.99% diterpenoids, and 57.46% other compounds; and the flowering aerial part displayed 8.20% aliphatic monoterpenes, 53.18% oxygenated monoterpenoids, 23.75% diterpenoids, and 14.87% other compounds. Diterpenes, particularly Phytol, were prominently present in the leaf, stem, and flowering aerial parts. Additionally, a diverse array of organic acids, ketones, and phenolic compounds were identified across the plant parts, each potentially offering distinct pharmacological benefits. The presence of exclusive compounds in specific plant parts, such as Dihydroxyacetone in the root (aerial part), underscored the pharmacological diversity of S. ewersii. This study provides valuable insights into the chemical diversity and pharmacological potential of S. ewersii, suggesting promising applications in pharmaceutical and medicinal fields. Further research aimed at elucidating the individual and synergistic pharmacological effects of these compounds is crucial to fully harness the therapeutic benefits of this plant. Full article

CO₂ geological sequestration in coal seams can be carried out to achieve the dual objectives of CO₂ emission reduction and enhanced coalbed methane production, making it a highly promising carbon capture and storage technology. However, the injection of CO₂ into coal reservoirs in the form of supercritical fluid (ScCO₂) leads to complex physicochemical reactions with the coal seam, altering the properties of the coal reservoir and impacting the effectiveness of CO₂ sequestration and methane production enhancement. In this paper, theoretical calculations based on ReaxFF-MD were conducted to study the interaction mechanism between ScCO₂ and the macromolecular structures of both low-rank and high-rank coal, to address the limitations of experimental methods. The reaction of ScCO₂ with low-rank coal and high-rank coal exhibited significant differences. At the swelling stage, the low-rank coal experienced a decrease in aromatic structure and aliphatic structure, and high-rank coal showed an increase in aromatic structure and a decrease in aliphatic structure, while the swelling phenomenon was more pronounced in high-rank coal. At the dissolution stage, low-rank coal was initially decomposed into two secondary molecular fragments, and then these recombined to form a new molecular structure; the aromatic structure increased and the aliphatic structure decreased. In contrast, high-rank coal showed the occurrence of stretches–breakage–movement–reconnection, a reduction in aromatic structure, and an increase in aliphatic structure. The primary reasons for these variations lie in the distinct molecular structure compositions and the properties of ScCO₂, leading to different reaction pathways of the functional group and aromatic structure. The reaction pathways of functional groups and aromatic structures in coal can be summarized as follows: the breakage of the O–H bond in hydroxyl groups, the breakage of the C–OH bond in carboxyl groups, the transformation of aliphatic structures into smaller hydrocarbon compounds or the formation of long-chain alkenes, and various pathways involving the breakage, rearrangement, and recombination of aromatic structures. In low-rank coal, there is a higher abundance of oxygen-containing functional groups and aliphatic structures. The breakage of O–H and C–OH chemical bonds results in the formation of free radical ions, while some aliphatic structures detach to produce hydrocarbons. Additionally, some of these aliphatic structures combine with carbonyl groups and free radical ions to generate new aromatic structures. Conversely, in high-rank coal, a lower content of oxygen-containing functional groups and aliphatic structures, along with stronger intramolecular forces, results in fewer chemical bond breakages and makes it less conducive to the formation of new aromatic structures. These results elucidate the specific deformations of different chemical groups, offering a molecular-level understanding of the interaction between CO₂ and coal. Full article

The search for practical solutions to alleviate the destructive impact of petroleum hydrocarbons in marine environments is contributing to the implementation of prospecting strategies for indigenous microorganisms with biodegradative and bioremediation potential. The levels of petroleum contamination entering the marine environment each year have been estimated at around 1.3 million tonnes, a figure that is expected to increase by 1.9% annually over the next decade. The recent interest in decarbonizing our energy system and accelerating the clean energy transition has created a demand for greener technologies and strategies to find innovative, sustainable, and cost-effective treatments for the marine environment. Diatoms (Bacillariophyta) are one of the most diverse and successful taxa in coastal–marine environments and are a relatively untapped pool of biodiversity for biotechnological applications. Recent reports have revealed the significant presence of diatoms associated with oil spills and petroleum hydrocarbon degradation. Most diatoms can secrete substantial amounts of exopolysaccharides (EPSs) into their environment, which can act as biosurfactants that, in addition to oxygen and other enzymes produced by diatoms, create suitable conditions to enhance hydrocarbon solubility and degradation into less toxic compounds in seawater. Recent reports on the biodegradation of aliphatic and aromatic hydrocarbons by diatoms are indicative of the potential of these taxa to achieve success in the bioremediation of hydrocarbons in marine environments. This review highlights the main attributes and roles that diatoms could play in integrated strategies for biodegradation and bioremediation of petroleum hydrocarbon pollutants and as such represent a green, eco-friendly, and sustainable contribution to mitigate damage to biodiversity and value chains of marine ecosystems. Full article

DFT-D3 calculations based on structural X-ray diffraction data obtained for 3-oxo-camphorsulfonyl imine (1), camphorsulfonyl chloride (2) and seven camphor sulfonimines (O₂SNC₁₀H₁₃NR, L¹−L⁷), from which L² (R=4-OHC₆H₄), L⁴ (R=4-ClC₆H₄) and L⁶ (R=3,5-(CH₃)₂C₆H₃) are synthesized and characterized in this work, provide information into the intra- and inter-molecular interactions with concomitant elucidation of the supramolecular arrangement of the compounds. The DFT-D3 calculations performed in small clusters of two or three molecular units reproduce the interactions observed via X-ray analyses, showing that, as a general trend, the structural arrangement of the molecules is driven by electronic rather than by packing parameters. In all compounds, the self-assembly of 3D structures involves the sulfonyl imine group (-NSO₂) either to establish hydrogen bonds through oxygen atoms or non-classic oxygen–aliphatic hydrogen or non-bonding interactions (NBIs), which also involve sulfonyl oxygen atoms. Interestingly, the camphor sulfonimine compounds (L², L³), having protic groups (R=C₆H₄X:X=OH, L² or X=NH₂, L³) at the aromatic imine substituents (=NR), present an extra π-π stacking, which is absent in the other compounds’ aromatic derivatives. The X-ray analysis shows that all the reported camphor sulfonimine compounds display the E configuration with respect to the imine substituent (R). The study of the redox behavior of the compounds by cyclic voltammetry enables insight into the solution properties of the compounds and the rationalization of the molecular interactions that stand in the solid and solution states. Camphor sulfonimine compounds (L) display appropriate binding atoms to coordinate transition metals. The results herein show that monodentate coordination through the nitrogen atom of the sulfonimine five-membered ring to the {Ag(NO₃)} metal center is favored. When this imine nitrogen atom is not itself involved in the organic framework, DFT-D3 calculations show that the complexation does not affect the non-covalent interactions that are reproduced in the MOF structure. Full article

Easily soluble organic components in Santanghu long flame coal (SLFC) from Hami (Xinjiang, China) were separated by CS₂ and acetone mixed solvent (v/v = 1:1) under ultrasonic condition, and the extract residue was stratified by carbon tetrachloride to obtain the light raffinate component (SLFC-L). The effect of solvent treatment on the composition and structure of the coal and its rapid pyrolysis products was analyzed. Solvent treatment can reduce the moisture content in coal from 9.48% to 6.45% and increase the volatile matter from 26.59% to 28.78%, while the macromolecular structure of the coal changed slightly, demonstrating the stability of coal’s complex organic structure. Compared with raw coal, the relative contents of oxygen-containing functional groups and aromatic groups in SLFC-L are higher, and the weight loss rates of both SLFC and SLFC-L reached the maximum at about 450 °C. In contrast, the loss rate of SLFC-L is more obvious, being 33.62% higher than that of SLFC. Pyrolysis products from SLFC at 450 °C by Py-GC/MS are mainly aliphatic hydrocarbons and oxygenated compounds, and the relative contents of aliphatic hydrocarbons decreased from 48.48% to 36.13%, while the contents of oxygenates increased from 39.07% to 44.95%. Overall, the composition and functional group in the coal sample were changed after solvent treatment, resulting in a difference in the composition and distribution of its pyrolysis products. Full article

The leaves of Nectandra laurel Klotzsch ex Nees, belonging to the family, Lauraceae, were collected in the province of Loja (Ecuador), dried, and analytically steam-distilled. An unprecedented essential oil was obtained, with a 0.03% yield by weight of dry plant material. The volatile fraction was submitted to qualitative (GC-MS) and quantitative (GC-FID) chemical analysis, on two orthogonal stationary phases. Seventy-eight compounds were detected and quantified on at least one column. The essential oil was dominated by sesquiterpene hydrocarbons (53.0–53.8% on the non-polar and polar stationary phase, respectively), followed by oxygenated sesquiterpenoids (18.9–19.0%). A third group was constituted by metabolites of other origins, mainly aliphatic compounds, apparently derived from the acetate pathway (11.7–8.5%). The major components of the EO (≥3.0% with at least one column) were δ-selinene (30.5–28.8%), δ-cadinene (5.4–6.4%), epi-α-cadinol (4.9–5.2%), an undetermined compound with a molecular weight of 204 (3.4–4.2%), α-pinene (3.3–2.9%), and α-cadinol (2.9–3.0%). Finally, the essential oil was submitted to enantioselective analysis, on two β-cyclodextrin-based chiral selectors, determining the enantiomeric distribution of seven chiral terpenes. Among them, (1R,5R)-(+)-α-pinene, (1R,5R)-(+)-β-pinene, and (R)-(−)-α-phellandrene were enantiomerically pure, whereas camphene, borneol, α-copaene, and α-terpineol were present as scalemic mixtures. Full article