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Extraction and characterization of extracellular polymeric substances from a mixed fungal culture during the adaptation process with waste printed circuit boards Full text
2019
Xia, Mingchen | Bao, Peng | Zhang, Shishi | Liu, Ajuan | Shen, Li | Yu, Runlan | Liu, Yuandong | Chen, Miao | Li, Jiaokun | Wu, Xueling | Qiu, Guanzhou | Zeng, Weimin
Extracellular polymeric substances (EPSs) extracted from fungal mycelium by four chemical methods (NaOH, H₂SO₄, formaldehyde-NaOH, glutaraldehyde-NaOH), three physical methods (heating, ultrasound, vibration), and a control method (centrifugation alone) were investigated. Results indicated formaldehyde-NaOH outperformed other methods with 186.6 ± 8.0 mg/g of polysaccharides and 23.2 ± 4.6 mg/g of protein extracted and ensured little contamination by intracellular substances. Thereafter, this method was applied in extracting EPS from a mixed fungal culture in the adaptation process with 0.5% (w/v) waste printed circuit boards (PCBs). With the four adaptation stages continuing, the culture tended to become more sensitive to respond to the external toxic environment characterized by secreting EPS more easily and quickly. The maximum amount of polysaccharides and protein could be achieved in only 3 days both at the 3rd and 4th adaptation stage. Three-dimensional excitation-emission matrix fluorescence spectrum indicated the peaks obtained for EPS were mainly associated to soluble microbial by-product-like and aromatic protein-like compounds. Transmission electron microscopic observation illustrated that although metal ions penetrated into hypha cells, parts of them could be absorbed by EPS, implying that EPS secretion may be a primary protective strategy adopted by the culture.
Show more [+] Less [-]Correction to: One-step synthesis of versatile magnetic nanoparticles for efficiently removing emulsified oil droplets and cationic and anionic heavy metal ions from the aqueous environment Full text
2019
Lu, Ting | Qi, Dongming | Zhang, Dong | Zhang, Chuan | Zhao, Hongting
On page 6156, “Regeneration of the MNPs for Cu(II) and Cr(VI) adsorption was conducted by using 0.1 mol/L HCl solution and NaOH solution as eluents, respectively” should read “Regeneration of the MNPs for Cu(II) and Cr(VI) adsorption was conducted by using 1.0 mol/L HCl solution and NaOH solution as eluents, respectively”.
Show more [+] Less [-]Induction of nuclear abnormalities in herring (Clupea harengus membras), flounder (Platichthys flesus), and Atlantic cod (Gadus morhua) collected from the southern part of the Gotland Basin—the Baltic Sea (2010–2017) Full text
2019
Eight nuclear abnormalities of genotoxicity and cytotoxicity were studied in peripheral blood erythrocytes of herring (Clupea harengus membras), flounder (Platichthys flesus), and Atlantic cod (Gadus morhua) sampled (2010–2017) from the Polish and the Lithuanian Exclusive Economic Zones (EEZ) in the Baltic Sea. At all study stations, total genotoxicity (∑Gentox) was found to be higher than total cytotoxicity (∑Cytox). A significant time-related decrease in genotoxicity was detected in the Lithuanian EEZ (2015–2017), while in the Polish EEZ (2014–2016), the opposite tendency was revealed. The highest ∑Gentox and ∑Cytox values recorded in fish sampled at the study stations located relatively close to each other clearly indicate an increased environmental genotoxicity and cytotoxicity pressure for fish in these areas. Exceptionally high and high-level genotoxicity risks to herring followed by those to flounder and cod were determined at a higher percentage of the stations studied.
Show more [+] Less [-]Impacts of climate change on cereal farming in Tunisia: a panel ARDL–PMG approach Full text
2019
We used an autoregressive distributed lag (ARDL) modeling to investigate the short- and long-term effects of climate change on Tunisian cereal farming. The Pooled Mean Group (PMG) estimation as well as Granger causality tests conducted on a regional panel of the country, covering a time horizon from 1975 to 2014, showed that climate change issues still persist in Tunisia, affecting negatively and increasingly the cereal output. This study proves that negative effects of climate are rather felt when there is a shortage of rainfall, whereas the current temperature levels are still in favor of cereal crop. The findings indicate that cereal farming requires a continuous technology pack deployment and a favorable climate. However, an unanticipated long-run relationship has been observed between cereal production and labor. As a result of this research, recommendations were built around two major strategies, namely yield improvement and farmers’ income stabilization to mitigate the unpredictable effects of climate change and hazardous events. The implementation of a production and regional specialization map and the adoption of an anti-drought insurance system in addition to compensation payment would be a suitable adaptation policy to climate change effects and for the sustainability of Tunisian agriculture.
Show more [+] Less [-]The detoxification of heavy metals from aqueous environment using nano-photocatalysis approach: a review Full text
2019
Heavy metals are discharged into aquatic environment and causes serious problems to the environment, human’s health, and other organisms. The industrial effluents contain high concentration of heavy metals that should be treated by different technologies. Numerous technologies have been widely used for the remediation of heavy metals such as chemical precipitation, ion exchange, membrane filtration, adsorption, coagulation-flocculation, floatation, electrochemical treatment, bioremediation, and photocatalysis. Among these technologies, photocatalysis has gained much attention due to chemical, physical, and electrical properties of heterogeneous semiconductor nano-photocatalysis. Bismuth vanadate is an n-type semiconductor photocatalyst having 2.4 eV band gap that was widely used from several decades having three monoclinic, tetragonal, and tetragonal zircon structures, but it also have some limitation that can be overcome by modification with metals or non-metals to gain high removal efficiency of heavy metals. This modification can tune its photocatalytic properties like band gap, absorption capacity, and surface area resulting in high photocatalytic performance towards heavy metals detoxification.
Show more [+] Less [-]Adsorption characteristics of Cu(II) and Zn(II) by nano-alumina material synthesized by the sol-gel method in batch mode Full text
2019
This study mainly focuses on the preparation, characterization, and sorption performance for Cu(II) and Zn(II) by using nano-alumina material (NA) synthesized through the sol-gel method. The SEM, EDS, FT-IR, and XRD analysis methods were implemented to identify the micromorphology and crystal structure of the synthesized NA absorbent and its structure after the adsorbing procedure. The effect of effective variables including various absorbent dose, contact time, initial ion concentration, and temperature on the removal of Cu(II) and Zn(II) from aqueous solution by using NA was investigated through a single factor experiment. Kinetic studies indicated that adsorption of copper and zinc ions by NA was chemical adsorption. The adsorption isotherm data were fitted by Langmuir (R²: 0.919, 0.914), Freundlich (R²: 0.983, 0.993), and Temkin (R²: 0.876, 0.863) isotherms, indicating that copper and zinc ions were easily adsorbed by NA with maximum adsorption capacities of 87.7 and 77.5 mg/g for Cu²⁺ and Zn²⁺, respectively. Thermodynamic parameters indicated that the adsorption of Cu²⁺ was spontaneous(G<0) and the adsorption of Zn²⁺ might not be spontaneous (G > 0) by NA. Graphical abstract ᅟ
Show more [+] Less [-]Preparation and flocculation properties of modified alginate amphiphilic polymeric nano-flocculants Full text
2019
The novel nano-flocculants were synthesized through a conjugation of dodecylamine with partly oxidized sodium alginate. The structures of the flocculants were characterized by FTIR, ¹HNMR, TGA, and EA. The flocculants possessed amphiphilic structures and formed nano-micelles through self-assembly in water. The nano-micelles showed rod-like shapes about 100 nm. Removal rates of the flocculants for Pb²⁺ and bisphenol A were determined under different conditions, showing the removal rates as high as 97.20% and 88.66% for Pb²⁺ and bisphenol A, respectively. The flocculation mechanisms were revealed by X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM), respectively. Isotherm adsorption studies indicated that the flocculation for Pb²⁺ accorded with the Langmuir single-layer adsorption model, and for bisphenol A accorded with the Freundlich multi-layer adsorption model. The quasi-second-order kinetic model was suitable for describing the adsorption kinetics. The new nano-flocculant was a promising agent for removing both heavy metal ions and organic pollutants of wastewater.
Show more [+] Less [-]Efficient removal of p-nitrophenol from water using montmorillonite clay: insights into the adsorption mechanism, process optimization, and regeneration Full text
2019
The present research highlights the use of a montmorillonite clay to remove p-nitrophenol (PNP) from aqueous solution. The montmorillonite clay was characterized using powder X-ray diffraction, Fourier-transformed infrared spectroscopy, scanning electron microscopy, X-ray fluorescence, Brunauer-Emmett-Teller analyses, and zero point charge in order to establish the adsorption behavior-properties relationship. The physiochemical parameters like pH, initial PNP concentration, and adsorbent dose as well as their binary interaction effects on the PNP adsorption yield were statistically optimized using response surface methodology. As a result, 99.5% removal of PNP was obtained under the optimal conditions of pH 2, adsorbent dose of 2 g/l, and PNP concentration of 20 mg/l. The interaction between adsorbent dose and initial concentration was the most influencing interaction on the PNP removal efficiency. The mass transfer of PNP at the solution/adsorbent interface was described using pseudo-first-order and intraparticle diffusion. Langmuir isotherm well fitted the experimental equilibrium data with a satisfactory maximum adsorption capacity of 122.09 mg/g. The PNP adsorption process was thermodynamically spontaneous and endothermic. The regeneration study showed that the montmorillonite clay exhibited an excellent recycling capability. Overall, the montmorillonite clay is very attractive as an efficient, low-cost, eco-friendly, and recyclable adsorbent for the remediation of hazardous phenolic compounds in industrial effluents.
Show more [+] Less [-]Suitable habitat prediction of Sichuan snub-nosed monkeys (Rhinopithecus roxellana) and its implications for conservation in Baihe Nature Reserve, Sichuan, China Full text
2019
As an endemic primate species with one of the highest priorities in wildlife conservation in China, Sichuan snub-nosed monkeys (Rhinopithecus roxellana) have undergone a sharp decline and range reduction in recent centuries. Here, we used maximum entropy modelling (MaxEnt) integrated with four types of environmental variables, including three biological climate variables (Bio17, precipitation of the driest quarter; Bio6, min. temperature of the coldest month; and Bio2, mean diurnal range), three topographic variables (altitude, slope, and aspect), two anthropogenic variables (Human Footprint Index and human disturbance), and three vegetation-related variables (enhanced vegetation index, normalized difference vegetation index, and Wet Index) to identify the spatial distribution of suitable habitats for Sichuan snub-nosed monkeys in Baihe Nature Reserve (BNR), which is located in the Minshan Mountains. The average training AUC of our model performance is 0.929 ± 0.003. The model predicted 9.6 km² of high suitability habitats and 14.1 km² of moderate suitability habitats for Sichuan snub-nosed monkeys, adding up to only 11.7% of the total area of concern for the study in the BNR. The top four variables ranked in the model (altitude, Human Footprint Index, human disturbance, and Bio17) accounted for relative gain contributions of 23.3%, 19.3%, 14.2%, and 13.4%, respectively. The predicted suitable habitats were confined to an altitude range of 1971–3198 m, Human Footprint Index of mainly 3–5 values, low human disturbance (mainly livestock), and precipitation of the driest (or coldest) quarter of 9–22 mm. Additionally, the suitable habitats were mainly distributed in the core zone (36.1%), buffer zone (26.8%), and experimental zone (29.5%). The remaining habitats (7.6%) were distributed in the 0.5-km buffer zone of the reserve border. The predicted suitable habitats indicated limited suitable habitat space for the Sichuan snub-nosed monkeys, with most of the suitable habitat distributed outside the core zone in the BNR. Our findings highlighted that human activities in all three functional zones could be the most negative factor on suitable habitat distribution of Sichuan snub-nosed monkeys in the BNR.
Show more [+] Less [-]Experimental characterization of multi-nozzle atomization interference for dust reduction between hydraulic supports at a fully mechanized coal mining face Full text
2019
To analyze the distribution pattern concerning multi-nozzle interference spray particle granularity between hydraulic supports, the present study conducts atomization interference experimental characterization for three types of nozzles used in coal mines based on a Doppler laser interference spray dust suppression simulation experimental system. The results indicate that for single-nozzle atomization, the impact of spray pressure on spray droplet size is gradually subdued, and a spray pressure of 8 MPa yields the best result; compared with single-nozzle spray, the multi-nozzle atomization interference effect can downsize the spray field overlapping zone, leading to an improved uniformity of overall spray particle distribution. As the spray field overlapping coefficient k increases, the particle size of the interference spray field decreases first and then increases. As the spray field overlapping coefficient reaches 0.4, the distribution of spray droplet size is most concentrated, corresponding to the optimal atomized dust suppression effect. Practical testing indicates that the optimal spray field overlapping coefficient measured at a fully mechanized mining face agrees well with the experimental result. Under the optimal parameters, the average total dust and respirable dust suppression rates measured at various measuring points on the downwind side during support relocation reach 78.93% and 80.53%, respectively.
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