Regular one-dimensional ZnO nanorods were synthesized by a complex-surfactant-assisted hydrothermal method for high-performance ethanol gas sensor using the mixture of sodium dodecyl sulfate (SDS) ...and polyethylene glycol 400 (PEG400) with a molar ratio of 1:1 as the complex surfactant.
Display omitted
•Regular one-dimensional (1D) ZnO nanorods (ZNRs) with large aspect ratio were synthesized by a complex-surfactant-assisted hydrothermal method using a mixture of sodium dodecyl sulfate (SDS) and polyethylene glycol 400 (PEG400) as the complex surfactant.•1D ZNRs with a single crystal hexagonal wurtzite structure were 120 − 180 nm in diameter and 2.4 − 4.5 μm in length.•The surfactants of both SDS and PEG400 played a significant role in the formation of 1D ZNRs, and a possible growth mechanism was proposed.•1D ZNRs showed high response, fast response/recovery time, good selectivity, and reversibility to ethanol gas.•The excellent ethanol sensing performance of 1D ZNRs is ascribed to the large length-to-diameter, the one-dimensional structure, and the numerous crystal defects of the oxygen vacancies existed in the surface region of 1D ZNRs.
One-dimensional (1D) ZnO nanorods (ZNRs) were synthesized by a facile and effective hydrothermal method using the mixture of sodium dodecyl sulfate (SDS) and polyethylene glycol 400 (PEG400) with a molar ratio of 1:1 as the complex surfactant. The microstructure and morphology were characterized using of X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The results demonstrated that the ZNRs are of a single crystal hexagonal wurtzite structure, having a larger length-to-diameter ratio with more regular surface morphology compared with the ZnO products obtained in the presence of only SDS or PEG400. A possible growth mechanism was proposed based the mediation reaction of the complex surfactant. Gas sensing measurements indicated that the ZNRs assisted by the complex surfactant demonstrated excellent ethanol sensing properties at an optimal operating temperature of 300 °C, which could be ascribed to their large length-to-diameter ratio, one-dimensional structure, and numerous surface defects of oxygen vacancies.
CuO-ZnO p-n junction nanowires were synthesized by a simple two-steps route for ethanol sensing application.
Display omitted
•Nanosized p-n junctions of CuO nanoparticles and ZnO nanowires were ...constructed.•CuO nanoparticles and ZnO nanowires were well-crystallized with the average diameter of around 30 nm.•Gas sensors based on CuO-ZnO p-n junction nanowires were fabricated and their gas sensing properties were compared.•Ethanol sensing performance of pure ZnO nanowires were effectively improved by the p-n junction construction.
CuO-ZnO p-n junctions were constructed by precipitating CuO nanoparticles on the surface of ZnO nanowires followed by an annealing process. The molar ratio of Cu to Zn in the final composites was controlled by regulating Cu content in the precursor solution. XRD, SEM, TEM, EDS, and XPS were used for the structural characterization of the prepared samples. The results confirmed that the monoclinic CuO nanoparticles were closely and uniformly attached on the surface of the hexagonal ZnO nanowires to form the p-n junctions. Notably, the one-dimensional structure of the host ZnO nanowires was well-maintained during the p-n junction construction process. Five sensors based on CuO-ZnO p-n junction nanowires with different Cu/Zn ratios as well as the pure ZnO nanowires were fabricated and their gas sensing performance was systematically compared. The formation of CuO-ZnO p-n junction effectively enhanced the ethanol sensing properties of the host pure ZnO nanowires. And 5%CuO-ZnO exhibited the highest ethanol response at the operating temperature of 300 °C, which was about 4 times higher than that of the pure ZnO. Several factors and considerations were then discussed for the explanation of the distinct sensing behaviors of these sensors.
Display omitted
•Copper ions severely deteriorate the floatability of chalcopyrite and molybdenite.•The adsorption of CuOH+ and Cu(OH)2 provide more reaction sites for depressants.•Cu2S is identified ...as the primary product during the inhibition process.•The similar floatability makes it difficult to achieve Cu-Mo flotation separation.•An inhibition model among mineral surface, copper ions and sulfide ions is proposed.
Copper ions are unavoidable in the process of copper-molybdenum flotation separation. The flotation response of chalcopyrite and molybdenite in the presence of copper ions was investigated through single mineral flotation tests and flotation separation tests. The influence mechanism was studied by adsorption experiments, zeta-potential measurements, and X-ray photoelectron spectroscopy (XPS) analysis. Flotation results indicated that copper ions dramatically reduced the recoveries of copper and molybdenum, and increased the inhibition effect of sodium sulfide; that is, the flotation separation of chalcopyrite and molybdenite was seriously hindered by copper ions. The adsorption experiments demonstrated that copper ions were adsorbed on molybdenite and chalcopyrite, and the adsorption amounts increased in the presence of sodium sulfide. The results of zeta-potential measurements confirmed that the floatability of the minerals was deteriorated by the adsorption of copper hydroxides (Cu(OH)+ and Cu(OH)2) and the subsequent adsorption of hydrosulfide ions (HS−). Moreover, XPS analysis verified that the adsorbed copper hydroxides reacted with hydrosulfide ions, producing Cu(I)-S species on the surface of chalcopyrite and molybdenite. The adsorbed Cu(I) ions provided additional reaction sites and promoted the formation of a hydrophilic layer by the attachment of excessive hydrosulfide ions. Based on these analyses, a possible inhibition model for the interactions among the mineral surface, copper ions, and sulfide ions is proposed.
Display omitted
Layered bimetallic hydroxide (LDHs) nanomaterials have shown excellent potential in the field of recovery of pollutants from wastewater through anion exchange and surface ...electrostatic interaction. In this paper, three new ternary ZnCrNi-LDHs with the different graded porous were successfully prepared by controlling the morphology of the layer stacking using triethanolamine as the soft-template, and characterized by SEM, TEM, XPS, TG, BET and XRD. The ZnCrNi-LDHs exhibited higher adsorption capacity for pollutants such as methyl orange, sunset yellow and their mixed solutions. The results showed that there was a good synergistic adsorption effect in the adsorption process of mixed solutions. The maximum adsorption amounts of single methyl orange, sunset yellow, and mixed solutions of methyl orange and sunset yellow were 1834.63 mg·g−1, 1259.79 mg·g−1, 3270.59 mg·g−1 and 3294.38 mg·g−1, which shows that the adsorption amounts about synergistic adsorption effect for mixed solutions is much higher than those of single methyl orange and sunset yellow; Meanwhile, the maximum adsorption capacity is higher than most adsorbents. The pseudo-second-order kinetic model fitted the kinetic data of adsorption, while the equilibrium adsorption isotherm data followed the Freundlich model. The adsorption process contains both surface adsorption and interlayer anion exchange as determined by SEM, XRD, IR and zeta potential analysis. The research not only demonstrates that three ZnCrNi-LDHs materials showed excellent adsorption performance and practical interest as an efficient adsorbent for the removal of methyl orange, sunset yellow, and mixed solutions but also provides a strategy for the removal of mixed dye solutions.
Layered double hydroxides (LDHs) have attracted increasing attention as promising candidates by anion exchanges and selective adsorption in the fluoride treatment field. In this study, three new ...ternary Zn-Co-Cr-LDHs were synthesized by primarily a one-step TEA-assisted hydrothermal process at various times. They were characterized by X-ray powder diffraction, thermogravimetric analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, N2 gas adsorption and desorption curves and zeta potential. The effects of dosage amount, reaction duration, initial solution pH, temperature, and co-existing ions were evaluated systematically for the Zn-Co-Cr-LDHs in fluoride removal process. Compared to Zn-LDHs and Zn-Co-LDHs, three Zn-Co-Cr-LDHs showed excellent adsorption performance for F- with maximum adsorption amounts of 108.87 mg/g, 97.27 mg/g, and 97.62 mg/g, respectively. The coexisting anions have less effect on the adsorption of F-. The introduction Cr3+ ion modulation in the Zn-Co-LDHs greatly improved the adsorption of fluoride ions. The kinetic process of fluoride ion adsorption is in accordance with the quasi-secondary kinetic model and the Elovich model, and the adsorption isotherm is in accordance with the Langmuir model. The quasi-secondary kinetic and Elovich models suggest that the process is chemisorption-controlled ion exchange adsorption. Zn-Co-Cr-LDHs are expected to have potential applications in fluoride removal process.
OCT-angiography is a non-invasive visualization imaging technology with high resolution that can more clearly image tiny blood vessels. Certain ophthalmic diseases can be diagnosed by the ...morphological changes of retinal blood vessels, and the automatic segmentation of blood vessel will definitely reduce workload of ophthalmologists. Current segmentation methods result in the loss of important detailed features and the segmenting failure of tiny blood vessels. We propose a joint 2D attention gate and channel-spatial attention network for the retinal vessel segmentation of OCT-angiography images to improve accuracy and reduce error rate. The improved 2D attention gate introduces attention coefficients to increase the weight of the blood vessel area, which preserves the branch structure and edge information of tiny blood vessels to a greater extent by combining context feature information of different levels of units. The channel-spatial attention block is used to enhance channel and spatial channel information, respectively. To enhance the credibility, our network was tested on two public data sets. Compared with channel and spatial attention network, U-Net with residual block and U-Net, the important indicator of accuracy is increased by 1.97%, 2.18% and 3.04%, respectively, in data set I and increased by 0.18%, 0.19% and 0.62%, respectively, in data set II.
The Euler-Euler model is less effective in capturing the free surface of flow film in the spiral separator, and thus a Eulerian multi-fluid volume of fluid (VOF) model was first proposed to describe ...the particulate flow in spiral separators. In order to improve the applicability of the model in the high solid concentration system, the Bagnold effect was incorporated into the modelling framework. The capability of the proposed model in terms of predicting the flow film shape in a LD9 spiral separator was evaluated via comparison with measured flow film thicknesses reported in literature. Results showed that sharp air–water and air-pulp interfaces can be obtained using the proposed model, and the shapes of the predicted flow films before and after particle addition were reasonably consistent with the observations reported in literature. Furthermore, the experimental and numerical simulation of the separation of quartz and hematite were performed in a laboratory-scale spiral separator. When the Bagnold lift force model was considered, predictions of the grade of iron and solid concentration by mass for different trough lengths were more consistent with experimental data. In the initial development stage, the quartz particles at the bottom of the flow layer were more possible to be lifted due to the Bagnold force. Thus, a better predicted vertical stratification between quartz and hematite particles was obtained, which provided favorable conditions for subsequent radial segregation.
There are many factors that affect the separation performance of the hydrocyclone, including the structure of the feed body, but the mechanism of influence of the internal flow field of the ...hydrocyclone on the Axial Velocity Wave Zone (AVWZ) is not yet clear. Based on the numerical test method, this paper analyzes the influence of the feed body structure on the internal flow field and the particle distribution characteristics of the AVWZ and its internal relationship with its separation performance. The results show that the influence mechanism of the structural parameters of the inlet structure on its separation performance is extremely complex, but all of them are reflected in the AVWZ’s characteristics, including the flow field characteristics, spatial distribution characteristics, and internal particle distribution. The changes on the inlet diameter will also influence the flow field, centrifugal strength, turbulence strength, and particle distribution, while the inlet aspect ratio is altered largely by changing the settling distance of particles. Finally, effects of inlet structure on the separation performance of the hydrocyclone can be explained from the AVWZ, which provides the basis for designing the inlet structure to improve separation performance.
TeO2 nanowires were synthesized by thermal evaporation of Te powders in air at ambient pressure. The crystal structure, morphology, and alcohol sensing properties of TeO2 nanowires were investigated. ...Structural characterizations showed that TeO2 nanowires with a tetragonal structure were approximately 70–200 nm in diameter and several hundreds of micrometers to 2 mm in length. No Au nanoparticles were observed at any ends of TeO2 nanowires, revealing that the growth process was dominated by the vapour-solid growth mechanism. Gas sensing measurements indicated that TeO2 nanowires with an n-type conduction showed a quick and reversible response to ethanol gas at room temperature. The response increased in the order of methanol > ethanol > propanol under the same conditions as well as with increasing alcohol gas concentration. The results demonstrate the feasibility of using TeO2 nanowires for sensing alcohol gases.
•The obtained TeO2 nanowires show a large surface-to-volume ratio.•Growth process of TeO2 nanowires is dominated by vapour-solid growth mechanism.•Sensitive and selective room temperature alcohol TeO2 nanowires gas sensor is demonstrated.
The degradation of DDTC in beneficiation wastewater has become an increasingly concerned issue due to the serious effects on the environment. In this study, the degradation characteristics of DDTC in ...artificially prepared beneficiation wastewater were investigated by adding sodium hypochlorite as an oxidant, and the influences of different degradation conditions on removal efficiency of DDTC were analyzed systematically. The results indicated that the degradation rate of DDTC without sodium hypochlorite added can reach 88.4% in a stewing time of 6 h. When the dosage of sodium hypochlorite was 400 mg·L−1, the degradation rate of DDTC can reach 91.28% for 1 min reaction time under the natural condition of pH value 5.98 and reaction temperature 25°C. The DDTC in the wastewater was firstly degraded into carbon disulfide and diethylamine, and then carbon disulfide was further degraded into CO2, S, or SO42−, while diethylamine was degraded into N2 and CO2. The research results can provide a technical basis for the treatment of beneficiation wastewater containing DDTC.
PDF