Study on removing Mo from tungstate solution using coprecipitation adsorption method based on novel Mo sulphidation process

Abstract

A coprecipitation–adsorption method based on a novel Mo sulphidation process is proposed for deep removal of molybdenum from tungstate solutions. First, a new sulphur source, P₂S₅, is used to provide HS^? for the Mo sulphidation process. The MoO₄^2? can be thoroughly converted into MoS₄^2? while tungsten still exists as WO₄^2?. Next, in the sodium tungstate solution, 99·4% of MoS₄^2? is removed with precipitated ‘nascent’ CuS under 6 h reaction at 30°C when the molar ratio Cu/Mo is 3. Similarly, in a commercial (NH₄)₂WO₄ solution, by controlling the molar ratio Cu/Mo at 6, 98·4% of MoS₄^2? is removed after 1 h at 30°C. Subsequently, phosphorus introduced during Mo sulphidation is removed using the magnesium ammonium phosphate method allowing the ammonium paratungstate to reach the GB 10116-88 APT-0 standard.

On propose une méthode de co-précipitation et adsorption basée sur un nouveau procédé de sulfuration du Mo pour l’enlèvement en profondeur du molybdène de solutions de tungstate. Premièrement, on utilise une nouvelle source de soufre, P₂S₅, pour obtenir le HS^? pour le procédé de sulfuration du Mo. Le MoO₄^2? est entièrement converti en MoS₄^2? alors que le tungstène existe encore sous la forme de WO₄^2?. Ensuite, 99·4% du MoS₄^2? est enlevé de la solution de tungstate de sodium avec le CuS ‘naissant’ précipité, en moins de 6 heures de réaction à 30°C lorsque le rapport molaire de Cu/Mo est de 3. De façon similaire, 98·4% du MoS₄^2? est enlevé d’une solution commerciale de (NH₄)₂WO₄, après une heure à 30°C, en contrôlant à une valeur de 6 le rapport molaire de Cu/Mo. Subséquemment, le phosphore introduit lors de la sulfuration du Mo est enlevé en utilisant la méthode du phosphate ammoniaco-magnésien, permettant ainsi au paratungstate d’ammonium d’atteindre la norme GB de 10116-88 APT-0.     

The role of particle size distribution of suspended solids in defining the flow properties of milk chocolate

The flow characteristics of molten milk chocolate, like most dense suspensions, are a function of the maximum packing fraction ((_m) of the suspended solids. Milk chocolates were prepared from mixtures of two relatively narrow coarse (d_4,3 = 17 μm) and fine (d₄,₃ = 8.5 μm) size distributions of non‐fat solids to contain 0, 25, 50, 75, and 100% of the coarse component. Solids bed density (a measure of maximum packing fraction) correlated with the apparent viscosity of milk chocolates (r = ‐0.98). The highest value for solids bed density and lowest value for apparent viscosity were measured for size distributions with 75% of solids from the coarse fraction. Casson yield value correlated with d_4,3 (r = ‐0.98) and specific surface area (r = 0.93). The maximum packing fraction of binary mixtures of two distinct sizes of non‐fat chocolate solids attained a maximum value for a specific volume ratio of the components. The maximum in _m corresponded with the minimum viscosity in molten chocolate at a given solids volume concentration.     

Structural and electrochromic properties of tungsten oxide prepared by surfactant-assisted process

By virtue of gemini surfactant template, nanostructured tungsten oxides thin films were prepared from the modified tungsten hexachloride sol-gel techniques. Temperature was varied as it is an important factor for crystallization, surface morphology and microstructure of tungsten oxides, from the studies of X-ray diffractions, scanning electron microscopy and transmission electron microscopy. The mesoporous sample calcined at 300 °C has tri-dimensional vermicular mesopores with nanocrystallites embedded in the pore wall, while such uniform structure would be destroyed by higher calcination temperature of about 400 °C. X-ray photoelectron spectroscopy was used for analyzing the surface-binding states and the stoichiometry for the oxides. Electrochromic characterization was implemented by simultaneous voltametric and spectrophotometric measurements of tungsten oxides/indium tin oxide (ITO) electrodes. The investigation results showed that organized pore-wall nanostructure has strong effects on the electrochemical and chromogenic properties depending on the specific surface area and the impacts from the evolved crystallization.     

决策树中数值型属性分裂的研究

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碳化钨及复合催化剂研究进展

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Image diffusion and cross-talk in passive matrix electrochromic displays

A passive matrix electrochromic display (ECD) working in transparent or reflective mode is described. In this paper, we report the main reasons of image diffusion and cross-talk in passive matrix ECD and initial computer simulation results of the 7×7 matrix display. These suggest that the insulation of electrolyte under each pixel and threshold (nonlinearity) of coloration current can in practice completely eliminate the image diffusion and cross-talk. The matrix addressed ECD based on solid polymer electrolyte and two complementary electrodes, (WO₃+0.1TiO₂, TiO₂–0.25CeO₂), in which all pixels were insulated by negative photoresist material was elaborated. An additional protected thin film (0.2Li₂O–0.2CeO₂–0.6SiO₂) deposited on working electrode was used to provide the enhanced threshold effect. The ECD exhibited excellent memory effect and substantially free from image diffusion and cross talk effects.     

中国钨业在21世纪的战略调整研究

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具有较大纯滞后的多变量耦合过程控制系统

本文介绍该控制系统的设计、各通道动态特性的测试．并对提出的ＰＩ＋Ｄｅｌａｙ解耦控制器的设计方法进行了实验研究。结果表明，该系统基本满足设计要求。     

Preliminary studies of In surface diffusion on the W(1 1 0) surface

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