Papers by Keyword: Vanadium

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Authors: Xin Hui Zhang, Le Ning Hu, Ai Hui Liang
Abstract: A new catalytic kinetic method for the determination of vanadium (V) was proposed, based on the V (V) catalyze the slow reaction between KClO3 and phenylgycollic acid (PA) in 0.6 mol/L H2SO4 solution at 100 °C. The reduction product of ClO3-, Cl-, reacts with Ag+ to form (AgCl)n nanoparticles. The nanoparticles exhibit a max resonance scattering spectral peak at 470 nm and a strongest fluorescence peak at 470 nm. The resonance scattering intensity at 470 nm is linear to the V concentration in the range of 2.0×10-9 mol/L to 4.0×10-8 mol/L. The influence factors on the catalytic resonance scattering determination of trace vanadium were examined. This catalytic resonance scattering spectral method has been applied to the analysis of vanadium in real samples, with satisfactory results.
Authors: G. Tchangbédji, E.P. Prouzet, G. Ouvrard
Authors: Lan Jie Li, Shi Li Zheng, Dong Hui Chen, Shao Na Wang, Hao Du, Ming Lei Gao, Yi Zhang
Abstract: Leaching of an extracted vanadium residue in sodium sub-molten salt medium was investigated. The significant effects of reaction temperature, particle size of residue, reaction time and NaOH-to-residue mass ratio on vanadium extraction were studied. By the orthogonal experiment study, it can be concluded that the impact order of factors is Tr> t>R according to the significance to the leaching process. Under conditions of reaction temperature 170°C, NaOH-to-residue 4:1, stirring speed 700 rpm, particle size -74 µm and reaction time around 180 min, leaching efficiency of vanadium obtained is higher than 90%. And, the leaching process of vanadium, with activation energy 27.69 kJ•mol-1, is controlled by the chemical reaction-controlled as the following rate equation. ln(1-x)=-kt
Authors: I.I. Parfenova, E.I. Yuryeva, Sergey A. Reshanov, V.P. Rastegaev, A.L. Ivanovskii
Authors: Xing Bin Li, Chang Wei, Zhi Gan Deng, Min Ting Li, Cun Xiong Li, Hong Sheng Xu
Abstract: A process has been developed at the laboratory scale for leaching of vanadium from a vanadium residue using mixed hydrofluoric and sulfuric acid solutions, and NaClO as an oxidant. The extraction studies were carried out using various acid concentrations, liquid/solid ratios, addition of oxidant, reaction temperatures and leaching times. The optimum leaching conditions were then determined. Characterization of the leach residues was carried out by SEM and EDS analysis. Results indicate that the silicates can be effectively destroyed by HF, and the vanadium contained in the vanadium-iron spinel can be leached by the mixed acid solutions. The addition of NaClO enhanced the leaching process by the oxidation of V3+(s) to V4+ and V5+. The leaching efficiency was also improved by raising the leaching temperature, prolonging the reaction rime and using a higher liquid/solid ratio. A vanadium recovery of 81.8% was obtained by the direct acid leaching process
Authors: Tohru Takahashi, Na Liu, Yusuke Yazawa, Takuya Nunome
Abstract: Compression and compressive creep behavior was studied on Al-Ti-V ternary alloys containing gamma+beta dual phase microstructures; the gamma phase was based on an L10 face centered tetragonal lattice and the beta phase on a disordered body centered cubic lattice. Yield strength and its temperature dependence have been compared with those in the gamma and/or beta single phase materials. The ternary alloy compositions were located on one assumed conjugate line across the gamma+beta dula phase field: the terminal compositions for the gamma and beta phase constituents were Al51Ti40V9 and Al35Ti20V45, respectively (numbers in atomic %). Three other alloys were prepared that contained different fractions of the constituent gamma and beta phases. The Al47Ti35V18, Al43Ti30V27, and Al39Ti25V36 alloys contained beta phase by about 22, 57, and 76 % in their area fractions. All these alloys showed limited deformability at temperature below 900K. The 0.2% proof stresses of the alloys were described in a similar way as a combination law at the room temperature; the 0.2% proof stress increased from about 500 to 1000 MPa with increasing the vanadium content. The high strength of the alloys containing high level of vanadium retained up to 900K, but the proof stress drastically diminished as the temperature was raised above 900K. Under compressive creep tests performed at temperatures ranging from 1100 to 1200 K, the minimum creep rates were smaller in the alloys containing less vanadium, and this could be ascribed to the fact that the beta phase was much softer than the gamma phase at higher temperatures than about 1000K.
Authors: Zhi Xin Shi, Jin Yan Liu, Xiao Wen Cai, Tian Yu Yuan
Abstract: Through the scanning electron microscope and energy spectrum analysis of vanadium slag after calcination at different temperatures of Panzhihua Iron and steel in industrial production, analyzed the change of morphology and composition of the various main phase, Focuses on the change process of two main vanadium containing phase which are vanadium spinels and calcium vanadate. The vanadium spinels into calcium vanadate optimal temperature range is 800 ~ 900 °C, and provides a theoretical basis for the extraction process of vanadium, which can further improve the industrial production of vanadium.
Authors: G. Pasold, N. Achtziger, Joachim Grillenberger, W. Witthuhn
Authors: Jie Yang, Yan Guo Teng, Dan Zhang
Abstract: A greenhouse experiment was performed to investigate the vanadium bioavailability of alfalfa grown in vanadium-cadmium contaminated soil. The results show bioavailable and total vanadium concentration in rhizosphere soil is higher than it in non-rhizosphere soil. With increasing vanadium addition, its speciation in soil is transformed to AC, RE, and OX fraction, especially to RE fraction. Alfalfa has high vanadium accumulation (up to 1221.86 mg/kg), and 70% of root samples belonged to strong absorption to vanadium. Both bioavailable and total vanadium in rhizosphere and non-rhizosphere soil have direct correlation with its content in alfalfa root. The increasing cadmium addition may inhibit vanadium absorption in alfalfa roots.
Authors: Li Zheng, Ying Zhang
Abstract: A catalytic voltammetric method for the determination of vanadium(V) at a multi-wall carbon nanotube paste electrode (MWCNT-PE) in a 4-(2-pyridylazo)-resorcinol(PAR)-bromate system is proposed. The voltammetric response of V(V)-PAR complex at MWCNT-PE was significantly enhanced because of a catalytic cycle consisting of electrochemical reduction of V(V) ion in the complex and subsequent chemical oxidation of the reduction product of V(V) by bromate. In pH 2.70 H2SO4 solution containing 5.0×10-6 mol•L-1 PAR and 3.0×10-2 mol•L-1 KBrO3 without any preconcentration, the linear sweep voltammetric peak current of the catalytic wave was proportional to the vanadium concentration in the range of 8.0×10-9 to 3.0×10-6 mol•L-1. The detection limit was 2.5×10-9 mol•L-1. Using the proposed method, the vanadium concentration in crude oil was evaluated and the results were compared with those of atomic absorption spectrometry.
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