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.
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•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.
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•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.
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•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.
As flowing film gravity concentrators, spiral separators are extensively used in the processing of numerous minerals. Appropriate design of their cross-sectional geometries has been known as an ...effective method to improve the performance of spiral separators. However, limited work has been published on the impact of cross-sectional geometry on flow field characteristics in spiral separators. In this study, the effects of cross-sectional geometries with various parabolic profiles (|x|=m|y|
n
) of a spiral separator on the flow film thickness, flow pattern and flow regime were investigated by numerical simulation. The validity of the simulation approach was confirmed by the reasonably good agreement between the predicted and measured flow film thickness in the own laboratory spiral separator. Results have shown that the flow film thickness and the mean primary velocity in the inner and middle troughs are reduced by decreasing downward bevel angle or increasing parabolic index. The dominant region of the secondary flow can be expended inward by increasing the downward bevel angle and decreasing the parabolic index. As the radial position extends inward, a larger downward bevel angle is more conducive to improving the intensity of secondary flow. A wider laminar flow region can be obtained with a smaller downward bevel angle or a larger parabolic index. The flow film thickness has a significant positive correlation with the trough slope in the inner and middle troughs. It is recommended that the matching relationship between material properties and flow field characteristics should be fully considered when selecting the cross-sectional geometry. Thus, this study aids the structural design of the cross-sectional geometries of spiral separators.
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•TiO2/clinoptilolite composite photocatalysts were successfully synthesized by a hydrothermal method.•TiO2/clinoptilolite composites exhibited excellent synergistic effect of ...adsorption and degradation.•Anatase TiO2 nanoparticles with a size of about 20 nm were coated on the surface of clinoptilolite and well-dispersed.•Complete degradation of xanthates can be achieved and over 90% of SIPX could be removed within 30 min.•The possible degradation pathway and degradation mechanism were proposed.
Acid leaching clinoptilolite-based composite photocatalyst coated with TiO2 nanoparticles was prepared by a hydrothermal method. Photocatalytic properties of the obtained TiO2/clinoptilolite were evaluated through the degradation of sodium isopropyl xanthate (SIPX) under UV light irradiation. The as-prepared samples were characterized by XRD, SEM, TEM, TG-DSC, N2 adsorption-desorption, XPS, FTIR, and UV–vis DRS in detail. Compared with pure TiO2, TiO2/clinoptilolite significantly enhanced the photodegradation efficiency of SIPX due to the synergistic effect of the composite. Over 90% of SIPX could be removed within 30 min with a TiO2/clinoptilolite dosage of 1.0 g/L under neutral condition. The influences of some parameters such as the TiO2 loading amount, H2O2 dosage, calcination temperature, and initial SIPX concentration on removal efficiency were investigated systematically. The results indicated that all the photocatalytic degradation process of SIPX followed a pseudo-first-order reaction kinetic model. Moreover, the stability and applicability of TiO2/clinoptilolite were also studied. The possible degradation pathway and mechanism of improved photocatalytic activity were proposed. It showed that the novel catalyst would have a promising application prospect in the field of flotation effluent treatment.
•Flotation-magnetic process is developed to beneficiate bastnaesite dominated RE ore.•Bastnaesite agglomeration occurs in the flotation process.•FM process has been applied in industrial production ...with stable and good index.
As rare earth metal prices fall, the low-cost beneficiation of their minerals has become essential. Flotation-magnetic (FM) separation is a newly-developed technology for the economic recovery of rare earth elements from the Dalucao ore. The FM process selectively agglomerates the rare earth particles while separating them from gangue minerals by bubble flotation. The agglomeration of fine bastnaesite particles has been observed by optical microscope and SEM combined with EDS which approves that the collector is selective for the fine mineral of bastnaesite. The quality of the flotation products are further improved by magnetic separation. The FM process has been successfully applied in the industrial production of the Dalucao rare earth ore located in Sichuan, China. The average rare earth oxide (REO) grade of the obtained rare earth concentrate was 65% in the latest 12-month production run with an average recovery of 55%.
•Chitosan was used as a selective depressant in copper–molybdenum sulfides flotation.•The results showed the selective adsorption of chitosan on chalcopyrite.•The depression mechanism of chitosan ...was studied by adsorption, FTIR spectra and ToF-SIMS.
Chitosan, a natural biodegradable polymer, was studied as a selective depressant in copper–molybdenum sulfide separation by flotation. Although chitosan depressed both molybdenite and chalcopyrite in single mineral flotation, selective flotation was achieved during the flotation of molybdenum-bearing copper sulfide concentrate at pH 6; the recovery of molybdenum in the froth product was over 70% while the recovery of copper was less than 24%. Adsorption measurements showed that chitosan had a higher adsorption density on chalcopyrite than on molybdenite. FTIR and ToF-SIMS measurements were carried out to confirm the different degrees of interaction of chitosan with molybdenite and chalcopyrite and the results showed that chitosan mostly adsorbed on chalcopyrite via amide groups when both molybdenite and chalcopyrite were present in the suspension.
The particle motion behavior in hydrocyclones has received increasing attention, but the particle circulation flow has received relatively limited attention. In this paper, the particle circulation ...flow is regulated by changing the secondary-cylindrical section diameter to optimize the separation effect. The effects of secondary-cylindrical section diameters on flow field characteristics and separation performance are explored using the two-fluid model (TFM). The findings demonstrate that particle circulation flows are ubiquitous in the secondary-cylindrical hydrocyclone and are induced by the axial velocity wave zone. The increase in the secondary-cylindrical section diameter intensifies the coarse particle circulation and aggrandizes the coarse particle’s aggregation degree and aggregation region, leading to an increment in cut size. The circulation flow component can be regulated by adjusting the secondary-cylindrical section, thus improving the classification effect. An appropriate diameter of the secondary-cylindrical section facilitates improved particle circulation, strengthening the separation sharpness.
The high reactivity of the acetylene group enables the formation of strong chemical bonds with active sites on mineral surfaces, thereby improving the flotation performance of gold minerals. This ...study utilized density functional theory (DFT) to analyze the quantum chemical parameters of structure, Mulliken population, and the frontier orbitals of a thioester collector containing an acetylene group, PDEC (prop-2-yn-1-yl diethylcarbamodithioate). PDEC was compared with analogous thioester collectors Z-200 and Al-DECDT. The interaction mechanism of PDEC on the Au(1 1 1) surface was simulated, followed by empirical validation through adsorption experiments. The findings indicate that the S atom of PDEC in the carbon–sulfur group exhibits shorter covalent bond lengths, and has reduced carbon–sulfur double bonds and Mulliken population, resulting in enhanced electron localization. This confers greater selectivity to PDEC during its adsorption on mineral surfaces. Frontier orbital analysis shows that the electrons of the acetylene group possess a notable electron-accepting capacity, significantly influencing the frontier orbital energy of PDEC and playing a pivotal role in the bonding interaction with mineral surfaces. Both the S atom in the carbon–sulfur group and its acetylene group establish stable adsorption structures with the A(111) surface in a single coordination mode. The adsorption energy sequence is PDEC > Al-DECDT > Z-200. Partial density of states demonstrates that the S 3p orbit of the carbon–sulfur group hybridizes with the Au 5d orbit, while the C 2p orbit of the acetylene group engages in weaker back-donation bonding with the Au 5d orbit. This is corroborated by the electron density difference and post-adsorption Mulliken population analyses, revealing that the S atom of the carbon–sulfur group in PDEC donates electrons to the Au atom, forming dominant positive coordination bonds, whereas the acetylene group accepts partial electrons from the Au atom, resulting in weaker back-donation bonds. The adsorption experiments align with the DFT adsorption energy results.
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.
