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Accurate Quantitative Analysis of Valuable Components in Zinc Leaching Residue Based on XRF and RBF Neural Network
No full textZinc smelting leaching slag is the solid smelting waste produced by the hydro-zinc smelting process, accounting for more than 75% of the total output of zinc smelting solid waste. Because it contains Zn, Cu, Pb, Ag, Cd, As and other valuable metals elements, it has great potential in resource utilization. However, due to its unstable composition content and insufficient detection accuracy, it is not easy to guarantee the resource conversion efficiency of key elements. Therefore, accurate quantitative analysis of the key resource components of the leaching residue is of great significance in the green development of zinc smelting. In this paper, five target elements of Zn, Cu, Pb, Cd, and As are the analysis objects, the method of XRF working curve and the method of XRF combined with RBF neural network model used to quantitatively analyze the target elements of the leaching residue. The relative error and Relative standard deviation are used as evaluation indicators of the two methods to compare the performance of the two methods. First, the concentration gradient samples of zinc leaching residue collected in the industrial field were prepared by standard addition method, used as standard sample and detected by ICP-OES. Then the detection result of ICP-OES is used as the reference value for the quantitative analysis of the target element, the concentration gradient sample is detected by X-ray fluorescence spectroscopy (XRF) to establish the working curve of target elements, the working curve is used to analyze each target element quantitatively. At the same time, the XRF spectrum data is used to construct the input matrix, the target element concentration of the sample is used to construct an output matrix, and the RBF neural network is trained to construct the multi-element calibration model of the target element in the leaching residue. This model is used to realize the target element prediction of the leaching residue sample. Compared with the ICP-OES reference value, the average relative error and standard deviation of the working curve method are 8. 5% and 4. 0%, respectively; Compared with the ICP-OES benchmark value, the average relative error and standard deviation of the RBF neural network are 0. 18% and 0. 58%, respectively. The results show that both methods can achieve the quantitative analysis of target elements of the leach residue samples, but XRF combined with RBF neural network can achieve the accurate quantitative analysis and matrix correction of the leach residue samples. The accuracy and precision of the analysis results are better than the traditional working curve analysis methods
Circadian humidity fluctuation induced capillary flow for sustainable mobile energy
No full textCircadian humidity fluctuation is an important factor that affects human life all over the world. Here we show that spherical cap-shaped ionic liquid drops sitting on nanowire array are able to continuously output electricity when exposed to outdoor air, which we attribute to the daily humidity fluctuation induced directional capillary flow. Specifically, ionic liquid drops could absorb/desorb water around the liquid/vapor interface and swell/shrink depending on air humidity fluctuation. While pinning of the drop by nanowire array suppresses advancing/receding of triple-phase contact line. To maintain the surface tension-regulated spherical cap profile, inward/outward flow arises for removing excess fluid from the edge or filling the perimeter with fluid from center. This moisture absorption/desorption-caused capillary flow is confirmed by in-situ microscope imaging. We conduct further research to reveal how environmental humidity affects flow rate and power generation performance. To further illustrate feasibility of our strategy, we combine the generators to light up a red diode and LCD screen. All these results present the great potential of tiny humidity fluctuation as an easily accessible anytime-and-anywhere small-scale green energy resource.
Droplet generators convert mechanical movements of droplets into small-scale electricity. Here, Tang et al. report a humidity-driven power generator by utilizing daily humidity fluctuation in atmosphere enabling continuous generation of electricity upon moisture absorption and desorption cycles
DEM-VOF simulations on the drawdown mechanisms of floating particles at free surface in turbulent stirred tanks
No full textThe drawdown of floating particles in turbulent stirred tanks is widely encountered in industrial processes. However, the data oriented drawdown mechanisms and the dependence of particle dispersion on particle properties and stirred tank structures are lacking. Especially in the simulation works, the effect of the free liquid surface on the drawdown of particles is commonly ignored. In this work, discrete element model coupled with volume of fluid method (DEM-VOF) is used to investigate the influence of particle properties and stirred tank structures on the drawdown processes with an orthogonal experimental design (OED). Both up-pumping and down-pumping of a 45 pitched blade (PBTU and PBTD) in the flat-bottomed stirred tank are studied. The method has been verified and validated with the invasive image-based experiments. Here, it is shown that the drawdown processes of PBTU and PBTD are different. The drawdown process is divided into pull-down stage, dispersion stage and cycle stage. Particle-particle collision, the total force, the coupling force and the turbulent kinetic energy of the free liquid surface are the main drawdown mechanisms. Baffles and the impeller clearance are key factors. The optimal combinations of factors level for the most uniform distribution and the least power consumption are obtained by OED, which provides reference for further industrial applications
Enhancement of Hg-0 adsorption performance at high temperature using Cu-Zn bimetallic sulfide with elevated thermal stability
No full textIn this work, a series of Cu-Zn bimetallic sulfides were synthesized to improve the mercury adsorption performance at high temperatures. Results showed that the adsorption performance of Cu-Zn bimetallic sulfides are much better than CuS and ZnS at high temperature. Compared with the pure CuS, the mercury adsorption efficiency greatly increased from 40% to 88% at 220?degrees C for the optimal Cu0.95Zn0.05S. XRD results showed that Zn can enter into the lattice structure of CuS, which significantly promoted the thermal stability of CuS. TG analysis indicated that the weight loss for the Cu-Zn bimetallic sulfides was only 14%-19%, while the weight loss for CuS is as high as 42%. Moreover, the adding of Zn can significantly inhibit the formation of inactive SO(4)(2-)during the synthesis process, enabling more Sx and S(2)(2-)sites exposed on the surface. Raman spectra indicated that the Sx sites mainly existed in the form of long-chain Sx (L-Sx) or ring Sx on the pure CuS, while existed as short-chain Sx (S-Sx) on Cu0.95Zn0.05S. The S-Sx sites are more active in mercury adsorption, resulting in the better performance of Cu-Zn bimetallic sulfides
Highly dispersed Ru anchored on nanosheet N-doped carbon for efficient and chemoselective hydrogenation of nitroaromatics to aromatic amines under mild conditions
No full textAn efficient catalyst for chemoselective hydrogenation of nitroaromatics to produce aromatic amines under mild conditions is highly desirable. In this work, a series of N-doped carbon (NC-x) with high nitrogen contents were firstly synthesized by pyrolysis of 1-butyl-3-vinylimidazolium bromide-co-acrylonitrile with a template of g-C3N4. Furthermore, Ru/NC-x catalysts were successfully prepared by ultrasonic-assisted impregnation method. The catalysts were characterized by various methods in detail, e.g.X-ray diffraction, N-2 physical adsorption-desorption, Transmission electron microscopy, Raman spectra, Scanning electron microscopy and H-2 temperature programmed reduction. Characterization results revealed that N-doping on carbon contributed to the high dispersion of Ru nanoparticles and resulted in the forming of the electron-deficient of Ru species. Nanosheet Ru/NC-2 with high N-doping content of 28 wt% exhibited superior performance under room temperature, i.e., nitrobenzene conversion > 99.0% and aniline selectivity 98.4%. Kinetic study indicated that the hydrogenation of nitrobenzene over Ru/NC-2 was the first-order kinetics with an intrinsic activation energy of 43.7 kJ/mol. Density functional theory calculation results suggested that Ru-N-x species, especially, Ru-pyrrolic-N facilitated nitrobenzene adsorption and H-2 dissociation, resulting in enhanced catalytic performance. In addition, the excellent stability of Ru/NC-2 made it essentially reserved for 410 h in the fixed-bed reactor. Moreover, Ru/NC-2 exhibited superior performance for the hydrogenation of various nitroaromatics to corresponding aromatic amines. This work could provide meaningful guidance on designing effective and stable catalyst for chemo-selective hydrogenation of nitroaromatics to aromatic amines under mild conditions
Transfer of molecular oxygen and electrons improved by the regulation of C-N/C = O for highly efficient 2e-ORR
No full textIn situ hydrogen peroxide (H2O2) production by two-electron oxygen reduction reaction (2e-ORR) is limited by sluggish dynamics which are divided into molecule transfer and reaction kinetics. Ordered matrix and disordered edge is synthesized to regulate molecules and electrons transfer. Interface Atomic Domains (IAD) are used to regulate the dynamics of 2e-ORR, which are a local chemical environment composed of C/N/O atoms (C-N, C = O). IAD are synthesized by biomass tar through pyrolysis, oxidation and doping. Sparse pyridine-N are constructed by the formation of C = O groups and the placeholder of pyrrole-N. Results indicate that surface pyridine-N improves interface electrons transfer, while sparse pyridine-N increases 2e-ORR selectivity. Meanwhile, the surface C = O groups provide strong chemical adsorption for O2 molecules. The collaboration of pyridine-N/C = O groups realized the high activity and selectivity of 2e-ORR. As a result, the synthetic material with N, O-functional groups possesses over 90% selectivity for 2e-ORR during a wide potential range