Search

[Display omitted] • Novel collector (DODHA) was used in fluorite/calcite/barite flotation separation. • Effective enrichment of fluorite in the absence of depressant can be achieved. • DODHA is lattice matched with fluorite surface favors the adsorption of DODHA. • Steric hindrance also plays a key part in determining the selectivity of DODHA. During fluorite flotation, the separation efficiency of fluorite from barite and calcite was low owing to their similar surface properties, therefore, developing highly selective flotation collector for fluorite is urgently needed. In this study, a novel surfactant, dioctyl di-hydroxamic acid (DODHA), was found as an effective collector for flotation separation of fluorite, calcite, and barite. Results from flotation tests suggested that the effective enrichment of fluorite from calcite and barite could be realized without the addition of depressants. FTIR, ζ potential, and XPS results indicated that the interaction between DODHA and fluorite was strong, whereas the adsorption of DODHA on calcite and barite was negligible. The DFT calculation, surface property, and molecular structure analysis results indicated that the steric hindrance and lattice matching between DODHA and mineral surface determined the superior selectivity of DODHA. [ABSTRACT FROM AUTHOR]

• The flow field evolution in a spiral separator is numerically studied. • The characterization methods for the stability of flow field are put forward. • The evolution process of the flow field in the first turn is investigated in detail. • A comparative analysis of the flow field at the end of each turn is performed. The liquid film in a spiral separator undergoes an evolution from unsteady to steady flow with increasing trough length. Understanding the process of the flow field evolution is a prerequisite for revealing the mechanism of particle segregation. In this study, a numerical investigation of the flow field evolution in a spiral separator with the cross-sectional profile of cubic parabola is conducted. The distribution profiles of the liquid film thickness, surface tangential velocity, and net radial flux along the trough length are used to characterize the stability of the liquid film shape, primary flow, and secondary flow, respectively. The results indicate that the flow field characteristics at the inner and middle troughs will reach a stable state earlier than that of the outer trough with the increase in trough length. Before reaching a fully developed steady state, the instability of the flow field characteristics at the outer trough exhibits damped oscillations. The instability of the flow field in the first turn is mainly caused by the collision between the fluid and the outer trough sidewall, which leads to large fluctuations in the flow field characteristics at the outer trough. Moreover, the unbalanced inward and outward flows generated from the collision may be the primary reason for the formation of the secondary flow. After the first turn, the flow field characteristics have approximately stabilized, but a certain transitional trough length is still required to reach a fully developed steady state. The secondary flow shows poorer stability compared with the liquid film shape and primary flow. These observations provide insight into the physics of the fluid flow in a spiral separator. [ABSTRACT FROM AUTHOR]

[Display omitted] • A jointed Dreiding-ClayFF force field is used to study adsorption mechanism of amine surfactants on quartz. • The solvated quartz and surfactant systems are built in a range of pH values. • Two amine surfactants, DDA and LAO, have different adsorption properties in various pH environments. • The simulation results are closely consistent with flotation tests. In this study, ClayFF and Dreiding force fields are jointed to model the adsorption of amine surfactants or their hydrolysate species on the solvated quartz surface under a wide range of pH values. As two case studies, cationic surfactant DDA (dodecylamine) and amphoteric surfactant LAO (N,N-Dimethylaminopropyldodecylamide oxide) are respectively selected as typical surfactants in molecular dynamic simulations. The simulation results demonstrate that DDA and LAO have excellent adsorption under natural conditions, but they have different adsorption mechanisms owing to their different polar groups. The polar group (-RN+H 3) of hydrolysis DDA can penetrate the first hydration layer and perpendicularly adsorb on the quartz surface via strong electrostatic attraction and hydrogen bonds. Compared with DDA, the hydrolysis LAO has a larger polar group consisting of R 2 N+→OH and -C(=O)NH– and its polar group lay horizontally around the first hydration layer rather than penetrate it. Besides, the adsorption of amine surfactants on quartz is inferred as multilayer based on the partial density distributions (PDD) analysis results. Subsequently, we determined the adsorption amounts, adsorption configurations and interaction energy that agreed with the quartz recovery in flotation test with a wide range of pH values. [ABSTRACT FROM AUTHOR]

Au-functionalized CuO nanorods based gas sensor was fabricated for room-temperature NO 2 sensing with good selectivity and reproducibility. • The Au-CNRs were prepared by a facile one-pot hydrothermal route. • The room-temperature NO 2 sensing of CNRs was realized by Au functionalization. • Fast response and recovery times towards NO 2 could also be achieved. • The changing of energy band gap and activation energy were the main reasons. In this work, a room-temperature NO 2 gas sensor based on Au-functionalized CuO nanorods (Au-CNRs) via a facile one-pot hydrothermal route was fabricated. The material characterizations were studied by XRD, SEM, TEM, XPS, and FTIR, respectively. The diameter and length of the pristine CuO nanorods (CNRs) were 30–60 nm and 150–200 nm, respectively. The CNRs structure was not significantly affected by Au functionalization. Au nanoparticles with the diameters of less than 20 nm were uniformly distributed on the surface of 2 mol% Au-CNRs. The gas sensing test result showed that room-temperature NO 2 sensing can be achieved by Au-functionalized CuO nanorods, especially the 2 mol% Au-CNRs, which exhibited the response of 3 towards 20 ppm NO 2 with the response and recovery times of 8 s and 176 s at room temperature (25 °C). This sample also showed good selectivity and reproducibility to NO 2. The related sensing mechanism of the CNRs based materials to NO 2 was investigated by the changing of energy band gap and activation energy with Au functionalization, respectively. [ABSTRACT FROM AUTHOR]

WO 3 ·0.33H 2 O microshuttles (WMSs) self-assembled by numerous nanorods along the same direction were prepared based on a cheap tungsten-containing metallurgical raw material by combination processes of NaOH leaching and one-step hydrothermal method. The microstructures and gas sensing properties of various concentrations (0, 0.7, 1.0, and 1.3 mol%) of Pt-doped WMSs were investigated to improve their performance. The microstructural characterizations demonstrated that the WMSs assembled by one-dimensional WO 3 ·0.33H 2 O nanorods were approximately 0.8–1.9 μm in diameter. Such nanorods exhibited a single hexagonal structure with their diameters ranging from 17 to 62 nm. The gas sensing properties indicated that Pt-doped WMSs showed superior gas sensing performance in terms of the sensor response and NH 3 selectivity in the operating temperature range of 25−225 °C as compared with pure one, and simultaneously Pt doping could significantly reduce the detection limit of NH 3. Especially, 1.0 mol% Pt-doped WMSs exhibited the highest response of 28.2–1000 ppm NH 3 at 175 °C, which was 4 times higher than pure one at 50 °C, indicating that it is a potential candidate material for the detection of NH 3 gas. • Pure and Pt-doped WO 3 ·0.33H 2 O microshuttles were synthesized from a tungsten-containing metallurgical raw material. • The WO 3 ·0.33H 2 O microshuttles were assembled by many one-dimensional nanorods with a single hexagonal structure. • Pt-doped WO 3 ·0.33H 2 O microshuttles exhibited overall enhanced NH 3 sensing performance compared with pure one. • The enhanced sensing mechanism of the Pt-doped WO 3 ·0.33H 2 O microshuttles was discussed. [ABSTRACT FROM AUTHOR]

• The correlation between stability constants of Zn(II) complexes and bonding strength of ligands is established. • The stability analysis of Zn(II)-polar group complex is investigated by DFT computational method. • The synergistic effect mechanism of different groups was investigated. • Flotation performances of hemimorphite with DGL and LSA are compared. • The polar groups of LSA bond with Zn site on the hemimorphite surface formation of the seven-membered structure. Based on the bond valence model and density functional theory (DFT), the correlation between the bonding strengths of groups and complex stability constants is established and adopted to design flotation collectors. Lauric acid (LA), N-laurylaminoacetic acid (LAA), N-Dodecanoylglycine (DGL), and N-Lauroylsarcosine (LSA) were used to verify the feasibility of design approach. Micro-flotation tests show that LAA and LSA exhibit better flotation ability than LA and DGL toward hemimorphite. However, the quartz can be collected by LAA due to the highly reactive imine groups, which means it can adsorb on the mineral surface through physical adsorption rather than the chemisorption. Fourier transform IR spectroscopy (FTIR) analysis shows that DGL and LSA can adsorb on hemimorphite surface through chemisorption. X-ray photoelectron spectroscopy (XPS) analysis reveals that the reaction is generated between carboxyl and amide groups and Zn site on the hemimorphite surface, forming seven-membered structure as the DFT simulation shown. [ABSTRACT FROM AUTHOR]

Based on the surface difference of hematite and quartz in solution, a hydroxyl-containing polyamine cationic surfactant was designed and screened with the assistant of computer simulation (molecular dynamics (MD) simulation and density functional theory (DFT) calculation) to enhance the separation efficiency in the reverse flotation system of hematite ore. And then N , N -dimethyl- N ′-(2-hydroxyethyl)- N ′-dodecyl-1.3-propanediamine (DMPDA) was synthesized in the laboratory. The computer simulation showed that the collecting ability of DMPDA would be comparable with that of N -dodecyl-1,3-propanediamine (NDEA) and N , N -Dimethyl- N ′-dodecyl-1,3-propanediamine (DPDA), while a better selectivity than that of DPDA and dodecylamine (DDA) could be obtained. The flotation performance and mechanism were studied by flotation tests, zeta potential measurements, Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The results of the flotation tests showed that DMPDA had a higher selectivity than DDA, which was in agreement with the theoretical prediction. The results of zeta potential, FTIR spectra, and XPS showed that DMPDA was adsorbed on the mineral surface mainly by electrostatic and hydrogen bonding. The introduction of the hydroxyl group could enhance the surface activity of the collector and the selective adsorption on the desired mineral surface. Based on this, a promising method for designing and screening the novel high-efficiency cation collector was proposed, which could accelerate the research and development of the cationic collectors. Unlabelled Image • The surface difference of minerals was used to design the novel surfactant. • The novel surfactant was screened by MD simulation. • DMPDA exhibited superior collector ability and selectivity than DDA. • Insertion of hydroxypropyl group could enhance the ability of cationic collector. • Better performance was achieved by weaker charges and larger sizes of polar groups. [ABSTRACT FROM AUTHOR]

Co 3 O 4 /SnO 2 flower-like structures were prepared via an one-step hydrothermal technique. Pure SnO 2 and Co 3 O 4 were used as reference, which were synthesized in the same condition by the hydrothermal technique. The products were characterized by field emission scanning electron microscopy (FESEM), X-ray diffractometer (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) nitrogen adsorption-desorption. It is revealed that p–n heterojunctions was formed. The TMA gas sensing measurement were investigated. The sensor made of 5 mol% Co 3 O 4 /SnO 2 flower-like structures exhibited response value of 9.3 to 5 ppm TMA at 175 °C, which is about 2.9 times higher than pure SnO 2 sensor and 7.2 times higher than pure Co 3 O 4 sensor at same temperature, respectively. In addition, this sensor also showed rapid response and recovery times to 5 ppm TMA (19 s and 29 s, respectively), good reproducibility and stability, lower detecting limit level (1 ppm), and good selectivity at 175 °C. The improved TMA sensing performance might be attributed to forming p–n heterojunctions at interface and Co 3 O 4 catalytic actions. Our works offer a synthesis method for fabricating Co 3 O 4 /SnO 2 flower-like structures. Moreover, the hierarchical Co 3 O 4 /SnO 2 p–n heterojunctions could be a promising candidate for TMA gas detection in the future. • Co 3 O 4 /SnO 2 flower-like structures self-assembled with porous nanosheets were synthesized by one-step hydrothermal method. • Co 3 O 4 /SnO 2 flower-like structures exhibited good sensing properties to TMA gas at a relatively low temperature of 175 °C. • The sensing enhancement mechanism of the Co 3 O 4 /SnO 2 flower-like structures was discussed. [ABSTRACT FROM AUTHOR]

Abstract: Large-scale synthesis of In2O3 nanoparticles, nanowires and nanorods were realized by improved chemical vapor deposition method on Au-coated silicon substrate. Field emission scanning electron microscopy revealed that the flow of carrier argon gas has profound effect on the shape and morphology of In2O3 nanostructures. Detailed structural analysis showed that the In2O3 nanostructures are single crystalline with a cubic crystal structure. Room temperature PL spectrum showed broad and intense blue emission at 375nm. The In2O3 nanowires sensor can successfully detect hydrogen gas with response time as low as 50s at 250°C. [Copyright &y& Elsevier]

Gas sensors require the construction of composites with high reactivity to reduce the detection limit, but this can lead to a broad-spectrum response between the adsorbed oxygen and the target gas, making it difficult to improve selectivity. In this study, the phenomenon of electron polar transport properties of the two-dimensional heterojunction material is first discovered in gas sensing and utilized to greatly improve the selectivity of butanone sensors. Ultra-thin porous ZnO nanosheets modified with SnO 2 /NiO heterogeneous particles are synthesized to achieve 20 ppb detection limits for butanone with a response of 328 to 100 ppm butanone, which is the lowest known detection limit. The combination of reaction kinetics and liquid chromatography-mass spectrometry reveals a good synergistic catalytic effect of SnO 2 /NiO heterogeneous particles, which may contribute to the high response and low detection limit of butanone. Finally, the possible mechanism for the generation of electron polar transport phenomenon is analyzed in the two-dimensional heterojunction material. This work provides a novel perspective for achieving both selectivity and detection limits in gas sensors, with universal applicability and application potential.

One-dimensional Zn-doped α-Fe 2 O 3 nanowires have been controllably synthesized by using the pure pyrite as the source of Fe element through a two-step synthesis route, including the preparation of Fe source solution by a leaching process and the thermal conversion of the precursor solution into α-Fe 2 O 3 nanowires by the hydrothermal and calcination process. The microstructure, morphology, and surface composition of the obtained products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. It was found that the formation process of α-Fe 2 O 3 is significantly influenced by the introduction of Zn 2+ . The gas sensing measurements indicated that the sensor based on 1% Zn-doped α-Fe 2 O 3 nanowires showed excellent H 2 S sensing properties at the optimum operating temperature of 175 °C. Notably, the sensor showed a low H 2 S detection limit of 50 ppb with a sensor response of 1.5. Such high-performance sensing would be ascribed to the one-dimensional structure and high specific surface area of the prepared 1% Zn-doped α-Fe 2 O 3 nanowires, which can not only provide a large number of surface active sites for the adsorption and reaction of the oxygen and H 2 S molecules, but also facilitate the diffusion of the gas molecules towards the entire sensing materials.

Nanostructured tungsten trioxide porous films were prepared by a non-hydrolytic sol⁻gel method following the inorganic route in which ethanol and PEG were used as the oxygen-donor and structure-directing reagent, respectively. The effects of aging time of the precursor solution, PEG content, and calcination temperature on the structure, morphology, and NO₂ sensing properties of WO₃ films were systematically investigated by using the techniques of X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and gas sensing measurements. The results demonstrated that a series of WO₃ films with different microstructures could be obtained by manipulating the synthesis parameters. Furthermore, a suitable synthesis condition of WO₃ films for NO₂ sensing application was determined.