خيارات البحث
النتائج 2671 - 2680 من 4,896
Untapped Sepia Shell–Based Composite for the Sorption of Cationic and Anionic Dyes
2019
Elgarahy, A. M. | Elwakeel, K. Z. | Elshoubaky, G. A. | Mohammad, S. H.
The current research reports an efficient methodology of new sorbent (SSBC) synthesis based on neglected sepia shells for the sequestration of cationic dye (Methylene blue, MB) and an anionic dye (Reactive black 5, RB5) from aqueous solutions. The as-synthesized SSBC was produced by reaction of sepia shell powder with urea in the presence of formaldehyde. In the first part of the work, the sorbent was scrutinized by using scanning electron microscopy, energy-dispersive X-ray analysis, Fourier transform infrared spectrometry, and titration (for determining pHPZC). In the second step, the influence of several parameters including pH effect, sorbent dosage, temperature, and ionic strength on the two dyes’ sorption effectiveness was examined. The sorption isotherms and uptake kinetics were analyzed at the optimum pH. Outlined results showed that the dynamic experimental obtained data followed the Langmuir isotherm profile, while the kinetic profile fitted well to the pseudo-second-order rate equation. Maximum sorption capacities reach up to 0.794 mmol g⁻¹ (254.05 mg g⁻¹) for MB and 0.271 mmol g⁻¹ (269.18 mg g⁻¹) for RB5, at pH 10.5 and 2.3, respectively. By comparing the sorption properties at different temperatures, the endothermic nature of the sorption process was revealed. Sorption processing under microwave irradiation (microwave-enforced sorption, MES) enhanced mass transfer, and a contact time as low as 1 min is sufficient under optimized conditions (exposure time and power) reaching equilibrium, while 2–3 h was necessary for a “simple” sorption. Dye desorption was successfully tested using 0.5 M solutions of NaOH and HCl for the removal of RB5 and MB, respectively. The as-prepared sorbent can be reused for a minimum of 4 cycles of sorption/desorption. Finally, the sorbent was successfully tested on spiked tap water and real industrial wastewater.
اظهر المزيد [+] اقل [-]Activation of endoplasmic reticulum stress in rat brain following low-intensity microwave exposure
2019
Ranjeet Kumar, | Deshmukh, Pravin S. | Sharma, Sonal | Banerjee, BasuDev
The present study was designed to explore the effects of low-intensity microwave radiation on endoplasmic reticulum stress and unfolded protein response. Experiments were performed on male Wistar rats exposed to microwave radiation for 30 days at 900 MHz, 1800 MHz, and 2450 MHz frequencies on four groups of animal: sham-exposed group, 900 MHz exposed (SAR 5.84 × 10⁻⁴ W/kg), 1800 MHz exposed (SAR 5.94 × 10⁻⁴ W/kg), and 2450 MHz exposed (SAR 6.7 × 10⁻⁴ W/kg) groups. Expressions of mRNA were estimated at the end of exposure in rat brain by real-time quantitative PCR. Microwave exposure at 900, 1800, and 2450 MHz with respective SAR values as mentioned above significantly (< 0.05) altered mRNA expression of transcription factors ATF4, CHOP, and XBP1 in accordance with increasing microwave frequency. The result of the present study reveals that low-intensity microwave exposure at frequencies 900, 1800, and 2450 MHz induces endoplasmic reticulum stress and unfolded protein response.
اظهر المزيد [+] اقل [-]Population susceptibility differences and effects of air pollution on cardiovascular mortality: epidemiological evidence from a time-series study
2019
Liu, Mengyao | Xue, Xiaoxia | Zhou, Baosen | Zhang, Yawei | Sun, Baijun | Chen, Jianping | Li, Xuelian
There is insufficient evidence on the relationship between air pollution and mortality from cardiovascular disease (CVD) in northeast China. Here, we explored the short-term effects of air pollution on CVD mortality and preliminarily investigated differences in population susceptibility to air pollution in Shenyang, China. CVD mortality, air pollution, and meteorological data during 2013–2016 were obtained. Time-series analysis was applied to evaluate the association between air pollution and daily CVD mortality with different lag structures. In the single-pollutant model, each 10 μg/m³ increase in PM₂.₅, PM₁₀, SO₂, NO₂, and O₃ concentrations and 1 mg/m³ increase in CO concentrations at lag0 (same day) was significantly associated with an increase of 0.40% (95% confidence interval, 0.22–0.59%), 0.26% (0.12–0.40%), 0.43% (0.16–0.70%), 0.90% (0.14–1.67%), 0.76% (0.21–1.32%), and 3.33% (0.97–5.75%), respectively, in overall CVD mortality. Susceptibility to air pollutants was higher among females, elderly people, and ischemic heart disease patients. Furthermore, air pollution effects on CVD mortality were 2–8 times greater during the non-heating period. In conclusion, the air pollutants PM₂.₅, PM₁₀, SO₂, NO₂, O₃, and CO showed significant positive effects on CVD mortality in Shenyang, China. These findings highlight the adverse effects of air pollution and suggest the need for personal protective equipment and reduction of air pollution sources.
اظهر المزيد [+] اقل [-]The role of the estuarine zone on the river particulate toxicity
2019
Marefat, Ali | Karbassi, Abdolreza | Nasrabadi, Touraj
Annually, a great volume of sediment and suspended particulate matters (SPMs) enters into the seas through estuaries. In the estuarine zone, metals present in SPMs may undergo conservative or non-conservative changes. In the present study, oxidation-reduction potential (ORP) as the most complex chemical parameter of open sea water and its relationship with the behavior of t metals in the estuarine area were investigated. Dissolved oxygen was used as a strong oxidant to increase the ORP. According to the absorption and desorption experiment, Mn and Cu are desorbed from SPMs during estuarine mixing. However, Zn and Pb are absorbed into the SPMs. In addition, the analysis results were indicative of the conservative behavior of Ni. The results of the three-step chemical partitioning of the SPMs revealed that Mn and Cu are desorbed from the SPMs physically, whereas Zn is absorbed into the SPMs chemically. Also, results showed that Pb is physically desorbed from the SPMs, while it is absorbed into SPMs chemically. All metals, except for Ni and Zn, whose reactions with the SPMs are not affected by an increase in the ORP, are affected by the escalation of this parameter.
اظهر المزيد [+] اقل [-]Equilibrium and Kinetic Study of Ammonium Sorption by Raphia farinifera
2019
Staroń, Paweł | Sorys, Paulina | Chwastowski, Jarosław
The study investigated the sorption capacity of biosorbent-raphia sp. against ammonia. Raphia fibers were used without and with the modification of its surface with NaCl, NaNO₃, and K₂SO₄. The data was analyzed in the state of equilibrium using four isotherm models such as Langmuir, Freudlich, Temkin, and Dubinin-Radushkevich. The equilibrium of ammonia sorption for all studied systems was best described by the Freudlich isotherm model. On its basis, it can be assumed that the studied process is of chemical nature, which results from the value of the coefficient 1/n < 1. In order to confirm the sorption mechanism, analysis of the kinetics of the ammonia sorption process on raphia fibers was performed. Four kinetic models of sorption were calculated: pseudo-first-order model, pseudo-second-order model, Elovich model, and Webber-Morris intermolecular diffusion model. The sorption kinetics of the modeled ammonia waste were carried out using unmodified palm fibers and all kinds of surface modification. This process was best described by the pseudo-second-order sorption model, which can be considered as a confirmation of the chemical nature of ammonia sorption on raphia sp. fibers.
اظهر المزيد [+] اقل [-]NDMA formation from 4,4′-hexamethylenebis (HDMS) during ozonation: influencing factors and mechanisms
2019
Shen, Linlu | Liao, Xiaobin | Qi, Huan | Zhao, Lei | Li, Fei | Yuan, Baoling
N-nitrosodimethylamine (NDMA), a toxic disinfection byproduct commonly associated with chloramination, has recently been found to form from an anti-yellowing agent (4,4′-hexamethylenebis (1,1-dimethylsemicarbazide) (HDMS)) during ozonation but the mechanisms are unclear. In this paper, the potential roles of molecular ozone (O₃) and hydroxyl radical (∙OH) on NDMA formation from HDMS were investigated under various oxidation conditions (ozone dosages, pH) and different components in water (bromide ion (Br⁻), bicarbonate ion (HCO₃⁻), sulfate ion (SO₄²⁻), and humic acid (HA), as well as natural organic matter (NOM) from a lake). Moreover, HDMS transformation pathways by ozonation were determined. The results indicated that the formation of NDMA was enhanced through the combined effect of O₃ and ∙OH compared to that by O₃ alone (addition of tert-butyl alcohol (tBA) as ∙OH scavenger). ∙OH itself cannot generate NDMA directly; however, it can transform HDMS to intermediates with higher NDMA yield than parent compound. The NDMA generation was affected (small dosages promoted but high dosages inhibited) by HA or Br⁻ no matter with or without tBA. The presence of SO₄²⁻ and HCO₃⁻ ions lowered NDMA formation through ∙OH scavenging effect. Increasing pH not only increased degradation rate constant by enhancing ∙OH generation but also affected HDMS dissociation ratio, reaching the maximum NDMA formation at pH 7–8. Natural constituents in selected water matrix inhibited NDMA formation. Impacts of these influencing factors on NDMA formation by only O₃ however were significantly less pronounced over that by the joint roles of O₃ and ∙OH. Based on the result of Q-TOF, LC/MS/MS, and GC/MS, the possible transformation pathways of HDMS by ozonation were proposed. The NDMA enhancement mechanism by the combined effect of O₃ and ∙OH can be attributed to greater amounts of intermediates with higher NDMA yield (such as unsymmetrical dimethylhydrazine (UDMH)) produced. These findings provide new understanding of NDMA formation upon ozonation of typical amine-based compounds.
اظهر المزيد [+] اقل [-]Co-culturing of oleaginous microalgae and yeast: paradigm shift towards enhanced lipid productivity
2019
Arora, Neha | Patel, Alok | Mehtani, Juhi | Pruthi, Parul A | Pruthi, Vikas | Poluri, Krishna Mohan
Oleaginous microalgae and yeast are the two major propitious factories which are sustainable sources for biodiesel production, as they can accumulate high quantities of lipids inside their bodies. To date, various microalgal and yeast species have been exploited singly for biodiesel production. However, despite the ongoing efforts, their low lipid productivity and the high cost of cultivation are still the major bottlenecks hindering their large-scale deployment. Co-culturing of microalgae and yeast has the potential to increase the overall lipid productivity by minimizing its production cost as both these organisms can utilize each other’s by-products. Microalgae act as an O₂ generator for yeast while consuming the CO₂ and organic acids released by the yeast cells. Further, yeast can break complex sugars in the medium, which can then be utilized by microalgae thereby opening new options for copious and low-cost feedstocks such as agricultural residues. The current review provides a historical and technical overview of the existing studies on co-culturing of yeast and microalgae and elucidates the crucial factors that affect the symbiotic relationship between these two organisms. Furthermore, the review also highlighted the advantages and the future perspectives for paving a path towards a sustainable biodiesel product.
اظهر المزيد [+] اقل [-]Study on new artificial floating island removing pollutants
2019
Kong, Lingwei | Wang, Lu | Wang, Qirui | Mei, Rongwu | Yang, Yifan
In this study, two types of artificial floating islands (AFIs), group A (consists of 1# and 2# traditional AFIs with plant and soil) and group B (consists of 4# and 5# new-type AFIs with plant, substrate, and with luffa sponge and corncob hanging at the bottom), were constructed, respectively. The removal effects and degradation mechanisms of luffa sponge and corncob in group B were compared and investigated. Plant height, root growth, and packing degradation of the two types of AFIs were studied. Temperature, dissolved oxygen (DO), and pH on the decontamination effects of AFI were discussed. The results showed that group A and group B AFIs showed great significant differences in removal of CODCᵣ, TN, NO₃⁻−N, NH₄⁺−N, and TP (p < 0.05). The TP removal of group B was 92.8 ± 0.6%, and the TN removal and NO₃⁻−N removal were significantly higher than that of group A, which was 90.3 ± 0.8% and 96.0 ± 2.2%, respectively; The addition of luffa sponge and corncob could enhance the biodegradability of sewage and the nitrogen and phosphorus removal efficiency of group B. The plant growth height of group B planted with Lythrum salicaria was 2.36 times higher than that of group A. The effect of temperature on TP was significantly greater than that of TN, and both groups of AFIs presented continuous improvement capacities of TN and TP removal when the temperature was above 15 °C. Group B was observed with a lower pH range of 6.69~7.12, which was more suitable for denitrification than group A. The release of carbon source of 5#-corncob AFI was 2.51 times higher than 4#-luffa sponge AFI at the end of the experiment.
اظهر المزيد [+] اقل [-]3D Simulation Model of Tidal, Internal Mixing and Turbulent Kinetic Energy of Palu Bay
2019
Sabhan, Alan Frendy Koropitan, Mulia Purba and Widodo Setiyo Pranowo
The tidal simulation models and internal mixing were constructed using finite volume method to simulate diurnal tide (K1) constituent and semidiurnal tide (M2) constituent, the mixing level model using General Ocean Turbulence Model (GOTM). Tidal elevation amplitude of the model K1 ranges from 19.27 to 19.31 cm, high tidal amplitude at the point near the mouth of the Palu River, low tidal amplitude at the open boundary of the model that leads to the Makassar Strait. The amplitude range by M2 tidal constituents is 55.55-55.75 cm, high tidal amplitude at the mouth of Palu Bay and the end of Palu Bay and the slope area. The tidal current of the K1 constituent strengthens at the open boundary of the model and weakens into Palu Bay, which then undergoes strengthening near the mouth of the Palu River which experiences extreme siltation, tidal currents strengthen in the mouth area of Palu Bay and the tip of Palu Bay is caused by the tidal constituent propagation M2 and also the slope of the area along the coast of Palu Bay. Bottom Ekman layer which is caused by K1 constituent can reach 11 meters while the M2 constituent reaches 7 meters. In the slope area, are also found the buoyancy frequency with the order of 10-5 which is at a depth of 75-150 m. Kinetic energy in Palu Bay stands at O (10-5-10-3) with high kinetic energy around rough topography in the order of 10-3 around the mouth of Palu Bay.
اظهر المزيد [+] اقل [-]Impacts of Human Disturbances on Riparian Herbaceous Communities in a Chinese Karst River
2019
Yuan Ren, Dongmei Wang and Xiaochen Li
Riparian zones suffer from increased human disturbances and the plant communities change unpredictably in response to altered conditions. It is important to understand the effects of human activities on plant communities for rational tourism development and ecological protection programs. We sampled 14 and 27 sites in nearly natural and human-influenced landscapes along the Lijiang River in southwest China, respectively, to detect human impacts on the ecosystem. We set three survey lines, based on a submersion gradient, at each site to determine whether herbaceous species richness increased with distance from the river, and we examined the effects of disturbance on herbaceous distribution. The landscapes shared 101 common species, and unique species in the human-influenced landscape were partly synanthropic. The species richness and diversity indices of the nearly natural landscape were significantly higher than those of the human-influenced landscape (P < 0.01). Species richness increased with distance from the river in the nearly natural landscape, and a significant difference was detected among the variances of survey lines (P < 0.05) in the human-influenced landscape. In the nearly natural landscape, species richness increased with fewer hydrological effects, and a stable community was maintained. However, human disturbances led to community variability and fragmented riparian habitats, resulting in species extinction and ecological degradation. We suggest that appropriate dam and reservoir regulations, prohibition of soil destructions, and a long-term research program for ecosystem protection may help in improving the monitoring of human influences and sustainable management in riparian zones of tourist rivers.
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