Уточнить поиск
Результаты 3861-3870 из 6,535
3D Hierarchical Porous Activated Carbon Derived from Bamboo and Its Application for Textile Dye Removal: Kinetics, Isotherms, and Thermodynamic Studies
2020
Liu, Huan | Xu, Chao | Wei, Xueling | Ren, Yiming | Tang, Dingxing | Zhang, Cuige | Zhang, Rongli | Li, Fang | Huo, Chaofei
In this study, activated carbons were prepared from bamboo via carbonization and successive KOH activation by tuning the post-treatment procedure. The resultant carbons possessed high surface area, high oxygen doping, and 3D hierarchical porous structure with interconnected micro-, meso- and macropores. These features resulted in ultra-excellent adsorption capacity for rhodamine B (> 1200 mg/g). Furthermore, the kinetic and isotherm experimental data were best described by pseudo-second kinetic model and Langmuir isotherm model, respectively. The adsorption of RhB onto the as-synthesized carbons was a spontaneous endothermic process. The π–π stacking, hydrogen bond, and acid-base interaction were proposed to account for the adsorption mechanism. Moreover, SiO₂ in bamboo-based carbon functioned as frameworks and its removal via alkali treatment led to the collapse of porous structure, decreasing surface area, pore volume, and O heteroatom doping, consequently dropping the adsorption performance. Overall, bamboo as an abundant and renewable biomass could be considered as a potential precursor for the production of excellent adsorbent for wastewater purification.
Показать больше [+] Меньше [-]Polymerization and Carbonization Behaviors of 2-Methylnaphthalene in Contaminated Soil During Thermal Desorption
2020
He, Liao | Sang, Yimin | Yu, Wang | Li, Wanxin | Jiao, Yuhai | Ma, Fujun | Li, Fasheng | Liu, Yuqin | Gu, Qingbao
Despite the important niche and broad applicability of thermal remediation (TD), little work has been done to discuss chemical reactions of methylnaphthalene contaminated soil. The 2-methylnaphthalene desorption amount (MDA) of TD is studied here under different conditions, and the carbonation (chemically polymerized or condensed) behavior of 2-methylnaphthalene is explained by analyzing the changes of soil organic carbons (SOCs), off-gas products, and surface chemical properties. It indicates that the influence sequence of MDA from high to low is heating time, heating temperatures, and flow rates of carrier gas. MDA increases steadily with the increase of temperatures (200–300 °C) but decreases slightly after 300 °C; the reason may be the chemical conversion of 2-methylnaphthalene. GC-MS analysis of off-gas confirms that partial 2-methylnaphthalene is polymerized to form 2-methylbenzo[b]thiophene and 2,4-di-tert-butylpheno at 400 °C, which is the first step of carbonization process. The x-ray photoelectron spectroscopy results of soil indicate that the C content decreases, but C–(C, H) chemical structure increases, indicating that new carbonaceous substances are generated. A layer of “char” is seen by scanning electron microscope to be left on the surface of the soil particles. As the temperature increases (200–400 °C), the SOCs generally decreases from 1.14 to 0.82%, which is the result of the equilibrium between SOCs pyrolysis and 2-methylnaphthalene carbonization. Therefore, partial 2-methylnaphthalene turns into smaller organic molecules in desorption gas of TD, meanwhile is accompanied by its chemical conversion to non-volatile products, which are attached to remediated soils and then improve soil properties and increase their fertility. Graphical Abstract
Показать больше [+] Меньше [-]Identification of irrigation potential areas, using multi-criteria analysis in Khyber District, Pakistan
2020
Waleed, Muhammad | Ahmad, Sajid Rashid | Javed, Muhammad Asif | Samiullah, Saifullah
This study explores the opportunities for irrigated agriculture in Khyber District of Former Federally Administered Tribal Area (FATA). Agriculture continues to be most important economic activity in Pakistan and former FATA is no exception. However, agriculture in the semi-arid Khyber District continues to suffer a decline due to excessive reliance on rainfall, which is drastically insufficient. Khyber District have large expanses of fertile land; however, farmers depend on unpredictable rain-fed agriculture, which has low productivity and food insecurity. There are a number of rivers in the region where great prospects exist for irrigated farming. Geographical information systems (GIS)-based multi-criteria analysis can be used to map areas with irrigation potential. The current study focused on different variables including soil texture, perennial rivers, land cover, topography, and dams. For this study, data was collected from diverse sources which include Google earth images, top sheets, land use land cover, soil texture map of FATA, and SRTM 30 Meter. The collected data was analyzed by using multi-criteria analysis in Arc GIS 10.2.2 by using MIF technique. The results of this research indicate that there is great potential for irrigated farming in the study area. Potential land for this purpose were divided into three categories, i.e., highly suitable which consisted of 678 km², or 26% of the total area; 1044 km² representing 40% were moderately suitable to irrigation; while the remaining 698 km² representing 27% were considered least suitable for irrigation. Likewise, 204 km² representing 7% were deemed unsuitable for irrigated agriculture mostly consisting of barren rocks. The results also illustrate how GIS as a tool can be used in the exploration of water resources in a scientific approach, thus making decision-making easier and more accurate.
Показать больше [+] Меньше [-]Assessment of the effect of sodium hydrogen sulfide (hydrogen sulfide donor) on cisplatin-induced testicular toxicity in rats
2020
Azarbarz, Nastaran | Shafiei Seifabadi, Zeinab | Moaiedi, Maasoumeh Zare | Mansouri, Esrafil
Cisplatin (CIS) is an antineoplastic drug able to produce free radicals that are capable to induce various side effects in different tissues. Hydrogen sulfide (H₂S) has notable antioxidant, anti-apoptotic, and anti-inflammatory effects in different systems but its role in male reproductive system is not fully understood. In the present research, the effect of sodium hydrosulfide (NaHS) on cisplatin-induced testicular toxicity in male rats was studied. Thirty-two Sprague–Dawley rats were equally divided into 4 groups. The control group was treated with normal saline by intraperitoneal injection. The NaHS group received NaHS (200 μg/kg/day) intraperitoneally for 15 days. The CIS group received single dose of cisplatin (5 mg/kg) intraperitoneally, while the combination of CIS and NaHS was given to the CIS+ NaHS group. At the end of the study, body and testicular weights, plasma testosterone level, histological and morphometrical alterations, inflammation via IL-1β protein, lipid peroxidation, and activity of antioxidant enzymes (including glutathione peroxidase, superoxide dismutase, and catalase) of testicular tissue were evaluated. CIS injection revealed a significant decrease (p < 0.01) in body and testis weights, plasma testosterone concentration, diameter of seminiferous tubules, germinal epithelium thickness, the number of Sertoli cells, spermatogonia and spermatocyte, Johnsen’s testicular score, and testicular antioxidant enzymes, whereas it caused a significant increase (p < 0.01) in lumen diameter of the seminiferous tubules, level of lipid peroxidation, and IL-1β protein expression when compared with the control group. NaHS administration to CIS-treated rats provided marked improvement (p < 0.05) in all biochemical, histological, and morphometrical changes induced by CIS. The beneficial effects of NaHS were mediated, at least partly, by its antioxidant and anti-inflammatory properties.
Показать больше [+] Меньше [-]Chemotype variations among lichen ecotypes of Umbilicaria aprina as revealed by LC-ESI-MS/MS: a survey of antioxidant phenolics
2020
Norouzi, Hooman | Azizi, Ali | Gholami, Mansour | Sohrabi, Mohammad | Boustie, Joel
In the present study, we characterized the phytochemical properties, which were specifically associated with phenolic compounds and antioxidant activities in six distinct ecotypes of Umbilicaria aprina Nyl. from Iran (including Kivarestan, Mishan, Takht-e Nader, Tochal, Sabalan, and Sahand) to detect diversities within the species. Total phenolic concentration (TPC) and radical scavenging capacities of U. aprina ecotypes were evaluated. Moreover, qualitative differences between chemical profiles were surveyed using liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). Relatively moderate TPCs (Kivarestan = 36.12 ± 2.1, Mishan = 41.59 ± 2.2, Takht-e Nader = 31.85 ± 1.3, Tochal = 37.55 ± 2.3, Sabalan = 28.91 ± 2.5, and Sahand = 31.59 ± 2.2) were observed for ecotypes, but a very strong correlation (r = −0/842) was obtained between TPCs and IC₅₀ values. Based on the results of LC-ESI-MS/MS, the following chemical substances were identified: orsellinic acid (1), lecanoric acid (2), evernic acid (3), gyrophoric acid (4), umbilicaric acid (5), hiascic acid (6), stictic acid (7) methyl hiascic acid (8), and an unknown substance (9). The MS/MS fragmentation scheme for each substance was determined and proposed. Wide discrepancies were observed in the chemical profiles of lichen ecotypes, which may corroborate the influence of ecological locality conditions, for example, altitude and slope aspects on secondary metabolism of lichen species U. aprina. The north-facing and east-facing ecotypes (Sabalan and Mishan, respectively) lacked depsidones (stictic acid) mainly because they receive the least direct radiation. Mishan ecotype, as the only east-facing ecotype, showed the most different chemical profile.
Показать больше [+] Меньше [-]Exposure to fine particulate matter induces self-recovery and susceptibility of oxidative stress and inflammation in rat lungs
2020
Ren, Huiqing | Lu, Jianjiang | Ning, Jianying | Su, Xianghui | Tong, Yanbin | Chen, Jiadeng | Ding, Yanzhou
PM₂.₅ induces pulmonary inflammation via oxidative stress, and this role in the lungs is widely accepted, but studies on whether oxidative stress and inflammation can self-recover and be fully restored are limited. In this study, the oxidative stress and inflammation in the lungs of rats, which were first exposed to different PM₂.₅ dosages (0, 0.5, 3.0, and 15.0 mg/kg body weight) and different recovery days (0, 15, and 30 days) and then were exposed to the same PM₂.₅ dosages (30 mg/kg b.w.) after 30 days of recovery, were investigated. Results showed that the activity of superoxide dismutase (SOD) was significantly inhibited, and the levels of malondialdehyde (MDA), inducible nitric oxide synthase (iNOS), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β) significantly increased. These changes were accompanied with damage to the pathological structure of the rat lungs. After stopping PM₂.₅ exposure, the difference between the PM₂.₅ group and the control group gradually decreased with the extension of recovery time. However, when the rats were again exposed to the same dose of PM₂.₅, the levels of IL-6, IL-1β, TNF-α, MDA, and iNOS were significantly increased, and the activities of SOD and GSH-Px were significantly inhibited in the high-dose group. And the high-dose group was accompanied by more severe lung pathological structural damage. Results showed that PM₂.₅ could induce oxidative stress and inflammatory damage in the lungs of rats, and these damages gradually recovered as exposure ceased, but increased lung susceptibility in rats.
Показать больше [+] Меньше [-]Application of waste cotton yarn as adsorbent of heavy metal ions from single and mixed solutions
2020
Mihajlović, Snežana | Vukčević, Marija | Pejić, Biljana | Grujić, Aleksandra Perić | Ristic, Mirjana
In this study, waste cotton yarn was used for the removal of Pb (II), Cd (II), Cr (III), and As (V) from aqueous solution. Adsorption of heavy metal ions was tested from single ion solutions, while competitive studies were performed using two- and four-ion mixtures. In order to change the structure of the material, cotton yarn was modified by sodium hydroxide solution. The surface of raw and modified cotton yarn were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, and streaming potential method for determination of an isoelectric point. Sorption studies were performed on the basis of pH, kinetics, isotherms, and desorption results. It has been shown that waste cotton yarn modification, typically, does not improve the sorption capacity of the material and that the unmodified material could be used for the removal of examined heavy metal ions. Selectivity was in order Pb > Cd > Cr > As. Desorption studies have indicated to the possible reusability of the sorbent only in the case of Pb removal. A potential application of spent waste sorbent for the soil quality improvement has been considered.
Показать больше [+] Меньше [-]Effects of Support on Performance of Methanol Oxidation over Palladium-Only Catalysts
2020
Zhang, xueqiao | Chen, Xingyi | Liu, Yu | Guo, Mengyuan
Two kinds of palladium-only catalysts loaded mesoporous beta zeolite (Pd/beta) and alumina (Pd/Al₂O₃) have been successfully prepared by the impregnation method and characterized using nitrogen adsorption–desorption, XRD, TEM, H₂-TPR, CO₂-TPD, and XPS. Catalytic activities of the catalysts for methanol oxidation were investigated with CO coexisting. The results showed that the different support determines the metal-support interaction, thus affecting the catalytic behavior. For Pd/beta, the strong basicity and better reductive ability are beneficial for improving the reaction rate of catalytic oxidation for methanol. And the palladium species with a higher oxidation state is responsible for excellent catalytic conversion of methanol and CO resistance. Compared to Pd/Al₂O₃, the T50, T90, and ΔT on Pd/beta catalyst are 145 °C, 160 °C, and 15 °C, respectively, in the case of CO present, which decreased by 45 °C, 91 °C, and 46 °C. So beta zeolite, as a new type of catalyst support material, has a good application prospect to meet the practical needs for emission purification of methanol-gasoline vehicles. Graphical Abstract
Показать больше [+] Меньше [-]Acute exposure to the fungicide penconazole affects some biochemical parameters in the crayfish (Astacus leptodactylus Eschscholtz, 1823)
2020
Alkan Uçkun, Aysel | Barım Öz, Özden
Penconazole is one of the most widely used fungicides all over the world, and since it spreads to large environments, its toxic effects on non-target organisms are of great concern. The toxic effects of penconazole on crayfish (Astacus leptodactylus), which is a bioindicator in freshwater ecosystems and consumed economically, are not known. Therefore, in this study, the purpose was to contribute to the literature on the potential harmful effects of penconazole on a non-target species, Astacus leptodactylus. For this aim, the acute toxicity (96 h) of penconazole was examined. The 96-h LC₅₀ value of penconazole was detected as 18.7 mg L⁻¹. Four concentrations of penconazole (18.7 mg L⁻¹, 9.35 mg L⁻¹, 4.68 mg L⁻¹, 2.34 mg L⁻¹) were applied to crayfish for 96 h. The results showed that penconazole had destructive effects on esterase mechanisms by inhibiting acetylcholinesterase (AChE) and carboxylesterase (CaE) activities. Significant increases were observed in all antioxidant parameters (superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), reduced glutathione (GSH), malondialdehyde (MDA)) in all doses except the lowest concentration (2.34 mg L⁻¹). All adenosine triphosphatase (ATPase) activities (Na⁺/K⁺-ATPase, Mg²⁺-ATPase, Ca²⁺-ATPase, total ATPase) had significant dose-related inhibition in both gill and muscle tissues. In summary, our findings show that acute penconazole administration to crayfish causes significant toxic effects on esterase, antioxidative parameters, and metabolic enzymes.
Показать больше [+] Меньше [-]Hexabromocyclododecane in riverine and estuarine sediments from Osaka, Japan: spatial distribution and concentration variability within identical samples
2020
Ichihara, Makiko | Yamamoto, Atsushi | Kakutani, Naoya | Funasaka, Kunihiro | Sudo, Miki
In this study, hexabromocyclododecane (HBCD) in riverine and estuarine sediments was investigated in Osaka, Japan. The mean total HBCD concentration detected in sediments ranged from < 0.50 to 130 ng g⁻¹ dry weight. This exceeded the ubiquitous HBCD contamination level found globally but was lower than that in areas affected by point sources, such as textile industries and expanded polystyrene plants. Sewage effluent was one of the suspected point sources of HBCD in the study area. The HBCD concentrations in sediments were highly dependent on certain factors, such as the location of the sampling site (proximity to possible emission sources), sediment properties (silt or sand), and organic substance content. The range of the diastereomer composition of α- and γ-HBCD was wider than that in other studies. Repeatability tests (n = 3) were conducted for all samples to assess the variability in the HBCD concentrations within identical sediment samples. Some variations were observed in the HBCD concentrations and diastereomer compositions within the repeatability test results at some sampling sites; nevertheless, the same samples were extracted and analyzed in triplicate. The bromine contents of the extracts of these samples were analyzed by X-ray fluorescence, and the results agreed well with those estimated from the LC-MS/MS results. From these results, it was confirmed that several sediment samples contained heterogeneously distributed HBCD. The risk characterization ratios (predicted environmental concentration/predicted no-effect concentration) of sites with high HBCD concentrations ranged from 0.1 to 1; thus, further information is required, and the sediment HBCD levels in this region should be continuously studied.
Показать больше [+] Меньше [-]