Binder-free combination of graphene nanosheets with TiO<Subscript>2</Subscript> nanotube arrays for lithium ion battery anode

Binder-free combination of graphene nanosheets with oriented TiO₂ nanotube arrays was designed and achieved via one-step facile electrodeposition. The structure and morphology of as-prepared composite graphene nanosheets/TiO₂ nanotube arrays were studied in terms of SEM, FESEM, EDX, TEM, Raman and FTIR. Furthermore, the corresponding electrochemical performances were evaluated in terms of galvanostatic charge/discharge, cycle stability and AC impedance. As expected, the composite graphene nanosheets/TiO₂ nanotube arrays displayed higher discharge capacity, cycle stability and Li⁺ diffusion coefficient than bare TiO₂ nanotube arrays. High Li-storage activity, superior conductivity and large surface area of graphene nanosheets should be responsible for improved electrochemical performances.     

Mineralogy,physical characterization and magnetic separation performance of a raw ilmenite concentrate for its purification

Mineralogy, physical characterization and magnetic separation performance were investigated for purification of a raw ilmenite concentrate. With the aid of mineral liberation analyzer (MLA) and optical microscope, it was found that (1) most of heavy minerals were distributed in the narrow size fraction, (2) clays and Ti-bearing magnetite needed to be separated prior to magnetic separation, (3) harmful elements such as Ca, P, ²³²Th and except Mg would’t be enriched in ilmenite concentrate, but enrichment of Mg could’t affect the concentrate quality, (4) Monazite was the main carrier mineral of Th, Ca and P. In addition, the expected yield of rejection and theoretical magnetic inductions were determined by separation tests of heavy minerals and magnetic analysis, respectively. Both the wet and dry magnetic separations were performed focusing on the examination of magnetic induction and it was found that the dry separator has an excellent selectivity against radionuclide bearing minerals. Finally, the dry magnetic separation as a core process technology was proposed to purify the raw concentrate.     

Improving the Estimation Accuracy of Copper Oxide Leaching in an Ammonia–Ammonium System Using RSM and GA-BPNN

In this study, a response surface methodology (RSM) model was used to analyze and optimize the factors affecting copper leaching efficiency in a copper oxide ammonia-ammonium (AA) system based on the parameters of AA concentration (ammonium hydroxide and ammonium bicarbonate matched with 1: 1), leaching time, grinding fineness, liquid-solid ratio, and temperature. The RSM analysis showed that five individual variables had a significant influence and that the interaction between AA concentration and leaching time had the most significant influence on leaching efficiency. In order to improve the estimation accuracy of the copper leaching efficiency, a model consisting of a genetic algorithm and a back propagation neural network (GA-BPNN) was used to optimize the operation index. A back propagation feed forward neural network with 3 layers (5–10–1) was applied to predict copper leaching efficiency. The genetic algorithm was applied to analyze the optimal leaching conditions. The results revealed that the GA-BPNN model outperformed the RSM model for predicting and optimizing copper oxide AA leaching. The optimization results of the GA-BPNN resulted in an R² of 0.99827 and the highest predicted copper leaching efficiency of 79.49% was obtained under the conditions of an AA concentration of 4.78 mol/L, a leaching time of 157 min, a grinding fineness of 86.86% (–74 μm content account), a liquid-solid ratio of 2.87: 1, and a temperature of 313.17 K. A prediction and optimization method combining RSM and GA-BPNN, as used in this paper, can be further employed as a reliable and accurate method for ore leaching.     

Solid-State Metalized Reduction of Magnesium-Rich Low-Nickel Oxide Ores Using Coal as the Reductant Based on Thermodynamic Analysis

The solid-state metalized reduction of magnesium-rich low-nickel oxide ore using coal as a reductant was studied based on thermodynamic analysis. The major constituent minerals of the ore were silicates and goethite. The former was the main nickel-bearing mineral, and the latter was the main iron-bearing mineral. Single factor tests were conducted to investigate the effects of reduction temperature, duration, and coal dosage on the beneficiation of nickel and iron such that optimal conditions were achieved. Considering the low recoveries of nickel and iron (Ni, 13.9 pct; Fe, 30.3 pct) under the obtained optimal conditions, an improved process, adding CaF₂ before the reaction, was proposed to modify the solid-state metalized process. The results showed that the recoveries of nickel and iron reached to 96.5 and 73.4 pct, respectively, and that the grades of nickel and iron in the concentrate increased from 2.5 and 62.6 wt pct to 6.9 and 71.4 wt pct, respectively. Nickel and iron in the absence of CaF₂ were metalized; nevertheless, the size of ferronickel particles was only 1 μm. Furthermore, alloys in the presence of CaF₂ aggregated and exhibited bands with a length greater than 200 µm. These observations suggested that CaF₂ could effectively reduce the surface tension of the newly generated alloy interface and promote the migration and polymerization of the alloy particles, which improves the beneficiation of nickel and iron by magnetic separation.     

The removal of sodium dodecyl benzene sulfonate by activated carbon modified with quaternary ammonium from aqueous solution

Activated carbon (AC) was modified via grafting quaternary ammonium for the selective adsorption of sodium dodecyl benzene sulfonate (SDBS) from aqueous solution. The surface modification of AC was confirmed by FT-IR, XPS and Raman spectroscopy. The results showed that the modified AC selectively adsorbed the anionic SDBS. Adsorption kinetics could be well described by pseudo-second-order kinetic equation (or three-stage intraparticle diffusion mode), adsorption isotherms fitted well with Langmuir model. Quaternary ammonium on AC enhanced electropositivity and led to the selective adsorption of SDBS.     

Application of a Waste Carbon Material as the Carbonaceous Reductant During Silicon Production

It is important to study the application of alternative carbon reductants for industrial silicon smelting to reduce consumption of carbonaceous reducing agents, electricity, and CO₂ emissions during silicon production. In this study, an industrial experiment was carried out in an 8 MVA submerged arc furnace using waste carbon material in place of approximately 20% partial reducing agents. The system was analyzed for silicon yield, power consumption, overall energy efficiency, CO₂ emissions, and the utilization rate of carbonaceous materials. The system improved the efficiency of carbonaceous materials and decreased power consumption using alternative carbon reductants. The results have showed that use of waste carbon materials reduced carbon emissions per ton silicon by more than 19.14% and specific CO₂ emissions decreased to 0.865 t.     

基于先验信息的供水管网阻力系数识别

供水管网阻力系数识别是指通过调整管网水力模型中管道阻力系数，使模型计算值与监测值相符的过程。由于实际中监测点数量有限，管网阻力系数识别为欠定的优化问题。现行方法通常采用管道分组这一参数化方法将欠定问题转换为超定，应用遗传算法或其它随机搜索算法求解。提出了基于先验信息的供水管网阻力系数识别算法，所提出算法根据管道管材、管龄等先验信息对管道阻力系数进行估计，并将估计值作为伪观测值引入目标函数将欠定优化问题转换为超定，采用高斯-牛顿算法进行求解。与现有方法相比，所提出算法避免了管道分组不唯一的问题；再者，推导了供水管网阻力系数雅克比矩阵解析式用于搜索向量构造，提高了参数识别计算效率。采用小型管网阐明了雅克比矩阵计算及搜索向量构造，利用大型管网验证了算法的实用性。     

Synthesis of Na-X zeolite from low aluminum coal fly ash: Characterization and high efficient As(V) removal

Na-X zeolite was successfully prepared from low aluminum coal fly ash (LACFA) via fusion-hydrothermal treatment. The influence of various synthesis parameters was investigated, including aluminum additives (AlCl₃·6H₂O, Al(NO₃)₃·9H₂O, AlF₃·3H₂O and NaAlO₂), dosages of NaAlO₂, weight ratio of LACFA/NaOH, crystallization temperature and time. The results indicated that the addition of Al species played a key role in the synthesis process of purity Na-X zeolite, and the corresponding relative crystallinity of the obtained samples was in the order of Na-X zeolite_(Al)???Na-X zeolite_(Cl)?>?Na-X zeolite_(N)?>?Na-X zeolite_(F) (Here, “Al”, “Cl”, “N” and “F” represent NaAlO₂, AlCl₃·6H₂O, Al(NO₃)₃·9H₂O and AlF₃·3H₂O, respectively). And the optimal operating conditions were: the weight ratio of LACFA/NaOH?=?0.83, short crystallization time 360?min, low crystallization temperature 90?°C and 0.038?mol NaAlO₂. Additionally, X-ray fluorescence (XRF), X-ray powder diffraction (XRD), Fourier Transforms Infrared (FT-IR) and Scanning Electron Microscopy (SEM) were employed to determine the resultant samples. Based on the results of As(V) adsorption experiment, the experimental data was suitable fitted by Freundlich adsorption isotherm model, and the theoretical maximum adsorption capacity was 27.79?mg/g at pH?=?2.14. The kinetics studies suggested that “surface reaction” was the rate-determining step of adsorption process, and the thermodynamics studies indicated that the adsorption process was spontaneous and endothermic. These results deemed that the LACFA was suitable for preparing Na-X zeolite_(Al), and the obtained Na-X zeolite_(Al) was served as a promising adsorbent to remove As(V) from acid wastewater.     

Properties of Natural Fibers from the Abaxial Side of Fireweed (Gerbera delavayi) Leaf Blade for Manual Spinning

Natural plant fibers obtained from the abaxial side of fireweed (Gerbera delavayi) leaf blade were systematically studied. Fireweed fibers were manually dismantled from hot-bath-treated, refrigerated, or untreated leaves and evaluated for different properties. In terms of the collection method, treatment with hot bath exhibited the highest efficiency. As for chemical composition, that of raw (untreated) fireweed fibers was similar to that of cotton, except for wax content that was four times higher in fireweed fibers that in cotton fibers. Fireweed fiber generally exhibited low values of length (6.5 mm), fineness (0.5 dtex), tenacity (0.7 cN/dtex), density (0.9 g/cm³), and crystallinity (14.6%) but similar elongation at break and moisture regain to those of cotton. Furthermore, fireweed fibers showed a smooth surface, soft texture, and water impermeability. After hot-bath treatment, fibers showed 20% lower wax component but higher thermal stability than raw fibers. The small size hindered the fibers from achieving the desirable standard of spinning and weaving by modern machine, but these unique cellulose fibers can be used for manual textile application without any chemical treatment.