Chalcopyrite (CuFeS2), as one of the carrier minerals of gold, undergoes significant alterations in lattice and surface properties upon doping with gold impurities. These changes markedly influence its separation and purification techniques, especially flotation. Using Density Functional Theory (DFT) based on first-principles, we analyze the influence of gold impurities on the lattice defects and surface properties of chalcopyrite. We developed an adsorption model using prop-2-yn-1-yl diethylcarbamodithioate (PDEC), a sulfur ester collector with an ethynyl group, on gold-infused chalcopyrite to elucidate the adsorption mechanism. Our findings indicate that the Au atom primarily occupies interstitial sites within the chalcopyrite lattice, resulting in an expanded lattice structure. Despite the doping, the lattice remains a p-type semiconductor with increased conductivity, facilitated by Au 6 s orbitals contributing to impurity levels within the conduction band from 2 to 4 eV. Additionally, there is a marked rise in spin-up electrons, with Integrated |Spin Density| results showing greater electron localization in Cu15Fe16S32Au and Cu16Fe16S32Au compared to ideal chalcopyrite crystal (Cu16Fe16S32). The Au atom exhibits maximum stability when adsorbed onto the S-Fe bonds on chalcopyrite surfaces, primarily forming covalent bonds through electron acceptance from Fe 3d orbitals. The presence of gold impurities decreases the collector's adsorption energy on the chalcopyrite (112) surface. However, PDEC exhibits enhanced adsorption performance relative to Al-DECDT and Z-200, primarily due to the chelation between thiocarbonyl and ethynyl groups of PDEC and the gold-bearing chalcopyrite (112) surface. Electron donation from Fe 4p orbitals of surface to the S 3 s and 3p orbitals of collector forms a sigma bond, while the ethynyl group undergoes hybridization with the Au 5d orbitals from -5 to -2.5 eV, fostering stable electron transfer.

The difference in chalcopyrite's primary ore-hosting rocks (dolomite and carbonaceous slate) in the Democratic Republic of the Congo results in an extremely uneven grain size distribution. Additionally, the presence of 2.21% organic carbon in the gangue impacts flotation efficiency. To address these challenges, ore properties were analyzed using the Mineral Liberation Analyzer (MLA), X-Ray Diffractometer (XRD), and microscopy. Flotation process was modified to incorporate a "middlings regrinding" processing, utilizing PDEC (an alkyne-based thioester collector, prop-2-yn-1-yl diethylcarbamodithioate) as the collector for experimental studies. Density Functional Theory (DFT) calculations elucidated the interaction mechanism of PDEC on chalcopyrite's surface. The MLA analysis indicates that chalcopyrite is mainly found in medium to fine grains, with the presence of fine-grained copper minerals smaller than 0.04mm accounting for 16.29% of the sample. This implies that these minerals require fine grinding for effective separation. Despite interference from organic carbon, PDEC demonstrates remarkable selectivity and efficiency in chalcopyrite flotation. By employing the "middlings regrinding" flotation method, a concentrate with a Cu content of 26.79% and a recovery of 87.88% was achieved, representing an increase of 0.17% in Cu grade and 4.09% in recovery rate compared to the conventional flotation process. DFT analysis demonstrates that the S 3p orbitals in carbon-sulfur double bond of PDEC and the C 2p orbitals in its acetylene group significantly affect its collection efficiency, engaging in hybridization with the Fe 3d orbitals on the surface of chalcopyrite, thereby facilitating a robust bonding interaction.

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 particle radial settling distance is determined by the separation chamber diameter ratio of multistage hydrocyclones, affecting particle circulation flow and particle misplacement. The effect of the separation chamber diameter ratio on the flow field and separation performance is explored using numerical simulations and physical experiments. The findings indicate that a larger separation chamber diameter ratio increases the particle circulation flow ratio and coarse particle circulation flow proportion, intensifying the particle enrichment ratio. However, smaller separation chamber diameter ratios result in higher turbulence intensity and higher enrichment ratio of coarse particles in the primary separation chamber. Both oversize and undersize separation chamber diameter ratios exacerbate misplaced coarse particles. Physical test results indicate that misplaced fine particles and coarse particles diminish and eventually increase with increasing the separation chamber diameter ratio. The + 150 lm particle content in the overflow reaches the minimum value of 0.32 % in the separation chamber diameter ratio of 0.5. In comparison, the -23 lm particle content in the underflow reaches the minimum value of 3.7 % in the separation chamber diameter ratio of 0.6, and the classification efficiency of -74 lm reaches the maximum of 61.85 %. Consequently, both large and small separation chamber diameter ratios will aggravate particle misplacement and deteriorate classification performance by augmenting the coarse particle circulation flow. (c) 2024 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

BiOBr-TiO2 (BT) composite photocatalysts were synthesized by using a two-step method including hydrothermal synthesis and water-bath precipitation. The microstructural characterization analysis proved that high-crystallinity and high-purity binary BT materials were achieved without by-products. TiO2 nanoparticles with a diameter of approximately 15 nm were decorated on multi-layered BiOBr nanosheets. The results showed that BT had highly-improved adsorption capacity and photocatalytic efficiency in comparison to pristine BiOBr and TiO2. The reaction rate constant of the optimal BT-2 composite photocatalysts for the degradation of 20 mg/L sodium ethyl-xanthate could reach 0.06496 min-1, which was 2.7 and 40.3 times than pure BiOBr and TiO2, respectively. The free radical scavenger test demonstrated that photogenerated holes were the main active species in the photocatalytic degradation reaction process. A possible degradation pathway for SEX molecules was provided through the interaction of visible light and BT-2 photocatalyst. The as-prepared BT materials can be used as efficient photocatalysts to completely degrade various types of xanthates under visible light.

Cylindrical hydrocyclones have received considerable attention for the benefits of reducing misplaced fine particles, but less attention to the effect of separation space on separation performance. This paper investigates the effect of separation space on the flow field and separation performance of cylindrical hydrocyclone by integrating the cylindrical height and vortex finder depth as variables utilizing a TFM model. The numerical results suggested that the separation space affected the tangential and axial velocities of particles slightly, while a larger separation space implies an enlarged upward distance of particles moving with the internal swirling flow, increasing the probability of forming particle circulation flow. Accordingly, the coarse particle enrichment region moves toward the wall and bottom region by increasing separation space. The separation accuracy increases and the cut size decreases by increasing separation space, however, the separation effect deteriorates when the vortex finder depth is less than the inlet pipe height.

The cylindrical hydrocyclone has been increasingly used in coarse classification due to its reduced fine particle entrainment, but the loss of coarse particles to overflow remains an intractable problem. Based on the notion that the strong circulation flow caused by the flat bottom structure bears primary responsibility for the problem, this study designs eight unique bottom profiles to regulate the particle cir-culating flow and attempts to correlate particle circulation flow with classification performance. The effects of the bottom profile on flow field characteristics, particle spatial distribution, circulation flow rates, and grade efficiency are explored in detail using validated models in a U200 mm cylindrical hydro -cyclone. The findings suggest that bottom profiles have the greatest effect on the axial velocity near the bottom and the grade efficiency of intermediate and coarse particles, while all unique designs have the potential to lower turbulence intensity. An ascending segment near the wall or a descending segment near the axis can help to mitigate the misplacement of coarse particles by reducing particle circulation flow without affecting the entrainment of fines appreciably. Additionally, two circles are found on each side of the cut plane, which is conducive to releasing coarse particles from the circulation flow. Regulation of particle circulation flow by adjusting bottom profile parameters can improve separation performance.CO 2023 Society of Powder Technology Japan Published by Elsevier B.V. All rights reserved.

The cylindrical hydrocyclone is widely used for coarse particle classification to suppress the misplaced fine particles in the underflow. Nevertheless, the unique flat bottom structure generates particle circulation flow, causing the misplacement of coarse particles in the overflow. A multi-stage cylindrical hydrocyclone is designed to regulate the particle circulation flow by shortening the particle radial settling distance. The particle circulation flow and classification performance of the cylindrical hydrocyclone and multi-stage cylindrical hydrocyclone are investigated by numerical simulations and physical tests. The numerical test results demonstrate that the multistage cylindrical hydrocyclone strengthens the circulation flow of 59.5 pm particles and 89 pm particles, and limits the circulation flow of 150 pm particles, increasing the enrichment ratio of 59.5 pm particles and 89 pm particles, reducing the enrichment ratio of 150 pm particles. The experimental results indicate that the multi stage cylindrical hydrocyclone suppresses particle misplacement in the overflow and underflow with superior classification efficiency, sharper separation accuracy, smaller cut size, and higher solids yields.

GO was used as a substrate to controllable synthesize rGO-SnO2 nanocomposites for preparing high-performance NO2 gas sensors. However, no product was obtained in the absence of GO substrates in a strongly alkaline environment at pH of 13.12. GO makes up for the shortcomings of alkali resistance of ordinary substrates. The flower-like hierarchical rGO-SnO2 nanocomposites were self-assembled from French fries-like SnO2 nanorods and rGO nanosheets. And each flower was composed of several French fries-like SnO2 nanorods with a length of about 800 nm and a square-shaped side length of approximately 80 nm. These SnO2 nanorods exposed profusely {200} crystal faces with high surface energy. The rGO-SnO2 nanocomposites based sensor showed a high response of 1809-1 ppm NO2 with fast response/recovery times of 251 s/14 s at 125 degrees C as well as good selectivity, high reproducibility, and long-term stability. The fast recovery speed of the sensor is due to the stable heating-assisted recovery method. The use of alkali-resistant GO as a substrate for nanoscale SnO2 growth effectively solves the problem of preparing SnO2 in a strongly alkaline liquid phase environment, which also contributes to the application of GO. This work provides a basis for developing high-performance NO2 gas sensors.

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.

立德树人是教育的根本任务，而课程思政是落实根本任务的重要战略举措。工程流体力学课程是大部分工科专业的核心骨干课程，也蕴含着丰富的思政元素。深度挖掘课程中的思政元素，并在专业知识传授过程中实现价值引领，对提升学生的思想道德水平和综合素养具有积极的作用。然而，传统的灌输式教学方法难以将科学知识讲授与思政教育实现自然融合。因此，基于PBL教学法，将课堂教学与思政教育自然融合，构建以思政为引领的工程流体力学课程建设和教学新模式，对提升课程的整体教学效果具有重要作用。

螺旋溜槽首圈流场特性及其演变对矿物颗粒运动与分离结果具有决定性影响.针对实验室?300 mm螺旋溜槽,采用RNG k-ε湍流模型、VOF和Eulerian Multi-fluid VOF多相流模型,系统考察了入口流量对螺旋溜槽首圈流场演变及赤铁矿和石英颗粒分布的影响.结果表明,增加入口流量会延长外缘处流膜形态、主流及二次环流达到稳定时的历程;随着入口流量的增大,石英和赤铁矿的分层效果得到增强,赤铁矿分布范围相应变宽,而石英向外缘流膜中的迁移量增加;首圈的最大分离效率随入口流量的增大呈现先增大而后渐稳的趋势,适宜的最低入口流量为7 L/min,此时首圈的最大分离效率可达61.45％.

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.

Traditional metal oxide semiconductor gas sensors are facing significant challenges for portable devices and integration due to large power consumption caused by high working temperature. 2D nanomaterials with large specific surface areas, rich active sites, and tunable electrical properties are proved to be promising candidates for room‐temperature gas sensors. However, several disadvantages including weak response, sluggish response/recovery kinetics, and poor selectivity still need to be overcome for high‐performance gas sensors. Herein, SnO 2 quantum dots (QDs) with a diameter of ≈3 nm functionalized SnS 2 nanosheets with a thickness of ≈17 nm are synthesized via a two‐step solvothermal method, which exhibits a high response of 11.1 to 100 ppm NH 3 at room temperature of 25 °C with fast response speed and good repeatability, high selectivity, and long‐term stability. The sensing mechanism is mainly ascribed to 0D/2D heterostructure, synergistic effect, and n‐n heterojunction constructed across the interfaces between SnO 2 QDs and SnS 2 nanosheets. The as‐prepared nanomaterials may contribute to the reasonable design of heterostructure between 0D QDs and 2D nanomaterials, and offer a promising candidate for room‐temperature NH 3 detection.

ZnSnO3 nanocubes (ZSNCs) with various Pt concentrations (i.e., 1at%, 2at%, and 5at%) were synthesized by a simple one-pot hydrothermal method. The microstructures of pure and Pt-doped ZSNCs were characterized by X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. Results showed that the pure ZSNCs have a perovskite structure with a side length of approximately 600 nm; this length was reduced to 400 nm after Pt doping. Following doping, PtOx (PtO and PtO2) nanoparticles with a diameter of approximately 5 nm were uniformly coated on the surface of the ZSNCs. Systematic investigation of the gas-sensing abilities of the nanocubes showed that the Pt-doped ZSNCs have excellent sensing properties toward nitrogen dioxide (NO2) gas in the operating temperature range of 75–175°C. Among the sensors prepared, that based on 1at% Pt-doped ZSNCs exhibited the best response of 16.0 toward 500 ppb NO2 at 125°C; this response is over 11 times higher compared with that of pure ZSNCs. The enhanced NO2 sensing mechanism of the Pt-doped ZSNCs may be attributed to the synergistic effects of catalytic activity and chemical sensitization by Pt doping.

Particle flocculation in a stirred tank was numerically investigated by a coupled CFD-DEM approach, in which a microscopic test in a typical zone was first proposed instead of solving the full-scale particle field. The flocculation kinetics was described by the Johnson-Kendall-Roberts (JKR) theory, followed by calibration of surface energy parameter. A Volume of Fluid (VOF) model was employed to capture the interface between liquid and air. The two-way coupling of fluid and particle was achieved by resolving pressure gradient force and Gidaspow’s drag force in the momentum equations. Based upon the qualitative and quantitative validation tests in air-water interface pattern and fluid tangential velocity, respectively, the particle coordination number and flocs fractal properties (e.g. fractal dimension, voidage, effective density) were investigated considering the effect of impeller speed. Results show that the number of particles first increases with particle coordination number and then decreases, and is further positively correlated with the stirring intensity in lower coordination numbers (0−3) while negatively correlated in higher coordination numbers (≥5). The influences of turbulence dissipation rate on the average particle coordination number were also investigated in radial, tangential, and axial directions. The mean floc size decreases with impeller speed, however, the fractal dimension increases in a certain range. The voidage increases with the daughter-particle number in a floc while the effective density of flocs is inversely proportional to the floc size. It is recommended to adopt operations that facilitate the one-by-one attachment mode and syneresis for forming relatively large and compact flocs.

基于数值试验系统考察了进料体积分数对旋流分离柱分离性能及颗粒运动行为的影响.结果表明,随着进料体积分数的增加,各粒级在底流中的分配率降低,分离粒度增加,底流夹细现象减弱,但过高的进料体积分数则导致溢流跑粗现象.高的进料体积分数意味着旋流分离柱内颗粒聚集程度增加,随内旋流运动的颗粒量增加.在Z=-400 mm平面,颗粒轴向速度随着进料体积分数的增加而增大,向底流口运动的颗粒所需要穿过的内旋流区域增大,粗颗粒被内旋流裹挟的可能性增加.随着进料体积分数的增加颗粒切向速度降低,导致颗粒受到的离心力减小,向内迁移的可能性增大,进一步增加了颗粒在内旋流区域的聚集.