Spent cathode carbon (SCC) is the largest and most inevitable hazardous solid waste continuously discharged from the aluminum electrolysis industry. In this study, mechanical activation was used to assist alkali fusion treatment in dissociating toxic substances and recovering graphite carbon from SCC. The effect of mechanical activation (i.e., milling speed, ball-to-material mass ratio, and milling time) on the alkali fusion treatment was investigated. Its effect on the physicochemical properties of SCC-Na2CO3 mixtures was also analyzed through particle size distribution, Brunauer-Emmett-Teller surface area analysis, scanning electron microscopy, X-ray diffraction and thermogravimetric analysis-differential scanning calorimetry. Results showed that mechanical activation enhanced the alkali fusion treatment by improving the physical separation of fluoride, the mixing uniformity and reaction contact area of SCC and Na2CO3, and promoting the conversion of Na2CO3 to Na2O. The formation of agglomerates was the main reason that the carbon content of recovered graphite carbon and the fluoride ion leaching rate increased initially then decreased with the increment in mechanical activation conditions. Under optimal mechanical activation conditions, the carbon content of recovered graphite carbon and the fluoride ion leaching rate increased from 89.35% and 76.50% (non-activated sample) to 93.93% and 95.02%, respectively, indicating that mechanical activation assisted alkali fusion treatment effectively enhanced the separation efficiency of fluoride and graphite carbon. In addition, thermodynamic analysis of the alkali fusion treatment and characterization of recovered graphite carbon (under the optimal mechanical activation conditions) were performed. Results demonstrated that the simultaneous conversion of multiple fluorides (i.e., Na3AlF6 and CaF2) and oxidative decomposition of cyanide in SCC can be achieved via mechanical activation assisted alkali fusion treatment. These findings indicate that mechanical activation-assisted alkali fusion treatment is a promising method for the detoxification and utilization of SCC.

使用密度泛函理论计算,结合表面定量分子静电势分析,对全钒液流电池电解液中四价钒离子的水合离子形成过程进行了研究.结果表明结合5个水分子后形成的[VO(H2O)5]2+结构,表面静电势极大值点仅出现在水分子的H原子附近,说明[VO(H2O)5]2+结构即为四价钒离子的水合离子单壳层结构,与实验结果很好的吻合.所采用的理论计算方法有望应用于全钒液流电池电解液中其他价态钒离子组分的研究.

A large amount of lead paste, which is produced by waste lead-acid batteries, and zinc leaching residue are hazardous wastes that have not been effectively treated around the world. A cleaner production process (reducing-matting smelting) was first proposed to harmlessly co-treat lead-containing hazardous solid waste and zinc leaching residues. During reducing-matting smelting, iron-containing waste (zinc leaching residue) as sulfur-fixing agent to retain sulfur, which reduces sulfur dioxide generation and emissions. Thermodynamic analysis shows that reducing-matting process requires strong reduction atmosphere. Zinc leaching residue provides the iron, silicon and calcium required for the slagging. Lead-containing waste after roasting is mixed with zinc leaching residue for reducing-matting smelting. Under optimum smelting conditions (8 wt% coke, Ferrous oxide/Silicon dioxide = 1.8, Calcium oxide/Silicon dioxide = 0.6, smelting at 1350 degrees C for 1.5 h), 92.4% of lead is recovered and fixed in the crude lead, lead content of slag drops to 1.2%. A portion of iron reacted with sulfur to form ferrous sulfide, most of the iron was present in the slag. This cleaner production technique also provides an alternative reference method for co-treatment of other lead waste containing sulfur. (C) 2019 Elsevier Ltd. All rights reserved.

The hierarchical electronic and ionic mixed conducting networks build in graphite felt electrodes possess excellent electrocatalytic activity and faster electronic and ionic conduction, resulting in an enhanced energy efficiency of vanadium redox flow batteries with durable life for 1000 cycles and a high discharge capacity of 10.1 A h L-1 at a current density of 350 mA cm-2.

AbstractGraphite felt (GF) with numerous merits has been widely used as electrode in all-vanadium redox flow batteries (VRFB), but its further application is still hindered by its intrinsically poor electrocatalytic activity. Herein, we propose a three-dimensional (3D) conducting network constructed with reduced graphene oxide (rGO) in the GF electrode via a two-step method. The 3D conducting network with abundant oxygen-containing functional groups in the GF is conducive to the transport of electrons between GF fibers and the electrochemical charge transfer to vanadium ions in the composite electrode; it can enhance the electrocatalytic activity and conductivity of GF. The VRFB using 3D rGO modified GF (mGF) electrode exhibited outstanding energy efficiency of 73.4% at a current density of 100 mA·cm−2, which is much higher than that with pristine GF (pGF) (65.4%); and better rate capability. These first results reveal that GF with 3D conducting network shows promising opportunities for the VRFB and other electrochemical flow systems

Spent pot-lining from aluminum electrolysis and coal gangue are toxic and hazardous solid wastes with high recovery value and contents of valuable elements, such as carbon, silicon, aluminum and fluorine. Thus, harmless treatment and recycling of these materials are of considerable importance. For extracting valuable components, Spent pot-lining and coal gangue were co-treated by hydrothermal acid-leaching method in this study. Effect of adding spent pot-lining on impurities leaching rate of coal gangue was systematically studied, and results indicated that fluoride in spent pot-lining positively affected the decomposition of coal gangue. Moreover, effects of leaching temperature, initial acid concentration, time, and particle size, on the extraction efficiency of aluminum were investigated comprehensively. Optimum parameters obtained by single-factor test included reaction temperature of 200 degrees C, initial hydrochloric acid concentration of 10 mot/L, time of 10 h, liquid-solid ratio of 10:1, and particle size below 200 mesh. Under these conditions, leaching rate of aluminum reached to 92.47%. Acid-leaching residue was used in the preparation of silicon carbide powder by carbothermal reduction, and silicon carbide powder with small size (D-50, the median diameter, of 18.15 mu m) was obtained by firing the acid-leaching residue at temperature of 1600 degrees C for 5 h. This study provides an inspiring approach for recovering and reusing spent pot-lining and coal gangue. (C) 2018 Elsevier Ltd. All rights reserved.

Vanadium oxide Li3VO4 has attracted much attention as anode material for Li-ion batteries in recent years since it has a low and safe redox potential (vs. Li metal), high specific capacity and its cost is low. However, the poor electronic conductivity and initial low coulombic efficiency limit its practical application. In this mini-review, the state-of-the-art results associated with Li3VO4 are summarized including structure, lithium insertion mechanism, preparation, modification, and electrochemical properties. Finally, the challenges and prospects are also discussed.

In order to obtain a safe, reliable, long-lived battery system without use of flammable, volatile, and relatively unstable organic liquid-based electrolytes, lithium garnet oxides with formulas Li7-xLa3Zr2-xTa xO12 (x=0.2-1) were synthesized by the solid state reaction method. Single cubic phases were observed in the composition x range between 0.2 and 1. The lattice parameters decreased with the addition of Ta due to the smaller ionic radius of Ta5+ compared with that of Zr4+, following the Vegard’s law. The total conductivity of the x = 0.3 composition is 6.03×10-5 S·cm-1 at room temperature with an activation energy of 0.30 eV. These lithium garnet oxides exhibit lithium ionic transport that is relevant to lithium battery application.

Soluble starch-functionalized graphene oxide composite (GO-starch) was prepared by a facile esterification reaction. And the composite was used as a novel adsorbent for the removal of Cd(II) from aqueous solution. The chemical composition and morphology of the GO-starch was investigated by fourier transform infrared spectroscopy, scanning electron microscopy and Raman spectroscopy. To evaluate the effects of the adsorption of Cd(II) by GO-starch, batch adsorption studies were performed to optimize the major parameters such as contact time, pH, initial concentration and temperature. The maximum uptake capacity of Cd(II) was 43.20 mg/g under the optimal conditions. Furthermore, the adsorption kinetics, isotherms and thermodynamics of Cd(II) on GO-starch were also investigated. The experimental data indicated that the adsorption kinetics and adsorption isotherms of Cd(II) on GO-starch were well fitted by pseudo-second-order kinetic model and Langmuir isotherm model, respectively. The adsorption thermodynamic parameters were calculated as ΔG 0 < 0, ΔH 0 > 0 and ΔS 0 > 0, respectively. The thermodynamic parameters indicated that the adsorption process was endothermic, feasible and spontaneous. Due to its high adsorption capacity for Cd(II), the GO-starch might have considerable potential for the aqueous removal of metal ions.

In order to obtain a safe, reliable, long-lived battery system without use of flammable, volatile, and relatively unstable organic liquid-based electrolytes, lithium garnet oxides with formulas Li7-xLa3Zr2-xTa x O12 (x=0.2-1) were synthesized by the solid state reaction method. Single cubic phases were observed in the composition x range between 0.2 and 1. The lattice parameters decreased with the addition of Ta due to the smaller ionic radius of Ta5+ compared with that of Zr4+, following the Vegard’s law. The total conductivity of the x = 0.3 composition is 6.03×10-5 S·cm-1 at room temperature with an activation energy of 0.30 eV. These lithium garnet oxides exhibit lithium ionic transport that is relevant to lithium battery application.

首次使用原位水解的方法成功制备了聚丙烯/二氧化硅(PP/SiO2)纳滤膜,在PP膜表面形成了一层致密的SiO2纳米聚合层,同时在膜的截面形成了由SiO2连接而成的提供离子传输的通道;该膜制备成本低,制备工艺简单环保,相较于Nafion115膜具有非常优异的防水迁移性能和较好的离子选择透过性,具有较好的充放电循环性能,在50 mA/cm2电流密度下,充放电循环40圈后,库伦效率及能量效率分别保持在94.5％和75.4％.

In this paper, a flow frame with multi-distribution channels is designed. The electrolyte flow distribution in the graphite felt electrode is simulated to be uniform at some degree with the tool of a commercial computational fluid dynamics (CFD) package of Star-CCM+. A 5 kW-class vanadium redox flow battery (VRB) stack composed of 40 single cells is assembled. The electrochemical performance of the VRB stack is investigated. Under the applied current density of 60 mA cm−2 during the charge and discharge processes, the current and energy efficiencies are delivered to be 93.9 and 80.8 %, respectively. A higher average output power of 7.2 kW can be achieved at the current density of 80 mA cm−2 with a lower energy efficiency of 78.4 %. The studies of kW-class VRB stack can be beneficial to the development of large-scale energy storage.

制备并表征了棒状水钠锰矿Na0.7MnO2.05,研究了其在K2SO4水溶液中电化学性能和制作成电容器的性能.结果表明:在0.5 M K2SO4水溶液中具有优异的高功率性能和循环性能;其和活性炭组成的混合超级电容器在400 W/kg和2.18 kW/kg的功率密度下,能量密度分别高达18 Wh/kg和14.2 Wh/kg,具有较好的循环性能,在1A/g的电流密度下,5 000次循环后,电容量还保持有90％.

An ion exchange membrane (IEM) usually serves as a separator between the two half-cells and provides an ionic conduction path in redox flow batteries. The new vanadium solid-salt battery (VSSB) presents higher energy density than the traditional vanadium redox flow batteries (VRFBs). However, present IEMs are based on very expensive Nafion® membranes. In pursuit of lower cost, a membrane from sulfonated polystyrene (PE-01) is used for VSSB. In comparison with the traditional Nafion® 1135, PE-01 shows high energy efficiency with good cycling performance at current densities less than 10 mA cm−2. This suggests that sulfonated polystyrene membrane is a promising candidate as separator for VSSB.