Tungsten Resource Distribution
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- Category: Tungsten Information
- Published on Thursday, 07 January 2016 11:49
Tungsten ore is a rock from which the element tungsten can be economically extracted. The ore minerals of tungsten include wolframite, scheelite, and ferberite. Tungsten is used for making many alloys.Tungsten ore deposits are predominantly magmatic or hydrothermal in origin and are associated with felsic igneous intrusions.
Tungsten ore resources distribution in the world
The world's tungsten resources are mainly distributed in China, Canada, Russia, the United States and Bolivia, these five countries accounted for 87% of the world's total basic reserves. Countries with significant resource potential as well as Australia, Austria, Brazil, Myanmar, Kazakhstan, Korea, Portugal, Spain, Turkey, Tajikistan, Uzbekistan, Turkmenistan and Thailand.
Tungsten ore resources distribution in China
Tungsten is China's advantages of mineral resources, more than 80% of tungsten resources are distributed in the South China tungsten-tin metallogenetic belt. China’s tungsten ore is across 29 provinces, municipalities and autonomous regions. In 2008, in the provinces, autonomous regions, municipalities with identified reserves of tungsten ore, Hunan, Jiangxi, Henan, Gansu, Guangdong, Guangxi, Fujian, Yunnan, this eight provinces and autonomous regions accounted for 89.54% of total reserves of China.
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Removing Tin From Ammonium Paratungstate
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- Category: Tungsten Information
- Published on Wednesday, 06 January 2016 20:29
Tin is a harmful impurity for tungsten, has a serious impact on the quality of tungsten products. To control the content of tin directly related the prosperity of tungsten products. Then, how to control the content of tin in tungsten metallurgy process? We are required to consider the quality of mineral and APT, using reasonable method to make sure the highest quality of APT at the lowest cost. We analyze from the following 6 aspects:
1. Source control, select fewer impurities like tin to reduce the subsequent tin removal process. However, due to the reducing of tungsten concentrate, the quality of ammonium (APT) can not be guaranteed;
2. Control of the reaction temperature, Sn leaching rate increased with the increase of temperature in the alkali decomposition. So control temperature in a proper range will make the Sn leaching remained at a low level, thus to ensure the quality of the APT;
3. Introduce additives，sodium phosphate is commonly used as an additive for tungsten concentrate;
4. Adjust the pH value. Tin will precipitate in alkaline environment. So control the pH value in an appropriate range will keep leaching rate of tin in a low level to achieve the goal of impurity removal;
5. Ion exchange adsorption. Trying to improve the exchange capacity of resin column, and increase the reaction time, then the removal rate of tin improved;
6. Reasonable solution of suction to cutting, to ensure the purity of ammonium tungstate solution.
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Macroporous Resin Treating High Concentration Sodium Tungstate
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- Category: Tungsten Information
- Published on Wednesday, 06 January 2016 19:41
Macroporous resin has discontinuous and discrete hole. It does not show the swelling in aqueous solution and is not transparent or milky when wet. Macroporous resin synthetic process: firstly add aromatic hydrocarbon, fatty hydrocarbon, alcohol and other organic solvents known as the pore. When resin polymerization, remove the solvent. Many big holes in the resin are formed. Macroporous resin plays the role of adsorption and filtering in water treatment, and can remove organic material, humus acid, lignin sulfonic acid. It can also remove iron, color, and protect ion exchange resin from pollution to prolong the service life of the exchange resin.
In the traditional tungsten smelting of ion exchange process, there’s a series of problems because of the large water consumption. How to improve the tungsten trioxide concentration of exchange liquid is a very important problem. Compared with the traditional gel type resin, adsorption effect of macroporous resin on high concentration sodium tungstate solution is best and beneficial to reduce the dilution water, improve the equipment capacity and reduce wastewater emissions.
Reaction with different types of resin and a certain amount of sodium tungstate solution under different conditions, through timing sampling analysis we can get the following results:
1. Under weak alkali conditions, different macroporous weakly alkali resin has good adsorption effect on high concentration sodium tungstate solution. The D301 resin adsorption speed is faster than the others. And it is relatively optimal in mechanical strength, wear resistance, resistance to swell-shrink.
2. D301 resin adsorption capacity decreases with the increase of particle size, but the trend is moderate. This illustrate that its chemical structure has no significant impact on the polymerization ion diffusion rate.
3. With the reduction of pH, D301 resin adsorption capacity firstly increases and then reduces. In the range of pH value 4 ~ 6, D301 resin shows higher adsorption capacity.
4. When the concentration of tungsten trioxide in range of 150 g/L and 455 g/L, the resin adsorption capacity can reach 850 mg/g dry resin. But because of high concentration, solution stability is poorer. Therefore, tungsten trioxide concentration control is advisably less than 350 g/L.
5. The D301 resin adsorbing polymerization ion process is less affected by temperature. The resin will be greatly influenced by the high temperature of solution. Therefore, it is most favorable to conduct high concentration of ion exchange under the environment temperature less than 30℃. .
6. The influence of stir speed on D301 resin adsorption capacity is not obvious. The influence of the high intensity mixing effect on the ion exchange process of the high concentration sodium tungstate solution is not big.
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Sodium Metatungstate Application in Soil Science
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- Category: Tungsten Information
- Published on Wednesday, 06 January 2016 19:37
Soil is natural subject composed of layers of different thickness of mineral composition. It includes the weathering of rocks minerals, plants, animals, microorganism decomposing organic matter, soil organisms, water and air. It is the survival foundation of most life on earth. Since ancient times, a large number of scientists have made the separation and study for larger particles contained in the soil, organic matter, humus acid and minerals. In various separation and purification ways, sodium metatungstate gravity separation method has some advantages such as simple process, no side effect and stable effect.
Sodium metatungstate is also called hexasodium tungstate hydrate. It is a kind of white crystal. Molecular weight is 2968.01. The density is 3.1 g/ml and the refractive index is 1.5555. Under atmospheric pressure, sodium metatungstate is stable. But avoid contacting with the material and the oxide. High density of sodium metatungstate, with non-toxic, easy preparation and recycled, are widely used in many fields.
Application in the field of soil science is mainly manifested in the following three aspects:
1. Separation of soil aggregation big particles: Jastrow adopted the sodium metatungstate gravity separation method to dry and separate samples and studied on he link between soil aggregate, micro particle natural body, and minerals organic matter. Yi Yang used sodium metatungstate as density separation medium and combined with the density separation method to study adsorption effect of soil carbon in river floodplains on polycyclic aromatic hydrocarbons.
2. Separation of soil C and N organic matter: Kramer studied the partial high content of C and N in sodium metatungstate impacting on the chemical properties of soil density separation. Roviro used different levels of density separation method to prepare three sodium metatungstate solutions and studied the calcium content in a certain amount of soil organic matter of Mediterranean forest area.
3. Separation of soil humus acid: Shindo used sodium metatungstate density separation method to isolate Japanese 24 charred debris in volcanic ash soil samples. It is concluded that they are important components of the ash black humus acid in soil. Sodium metatungstate has been used for separating fossil plants and minerals from the rich soil. Georgiadis used sodium metatungstate density fractionation to extract amorphous silica from soil.
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Sodium Tungstate and Mixed System Improving Down Fiber Flame-Retardant Properties
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- Category: Tungsten Information
- Published on Wednesday, 06 January 2016 19:22
Down fiber is the villus growing in the stomach of goose and duck. The surface of down fiber is a layer of membrane. Membrane layer is protein composing a major component of down fiber. Down fiber is densely covered thousands of tiny pores which change with the temperature to expansion and contraction. It has the temperature adjustment function and can absorb the flow of heat of human body sending out to isolate from the outside cold air invasion. Analysis from the volume testing, down fiber is higher than silk, cotton and heat preservation material. So down fiber simply as a heat preservation material, its economic value is much higher than other heat preservation material.
Scientists have studied the wettability, fluffy and stability of down fiber, but the study on the flame-retardant properties of down fiber is very little. With the continuous development of science and technology, countries around the world are increasingly demanding on the flame-retardant properties of textiles. Therefore, modification of down fiber flame-retardant is imperative. Sodium tungstate, potassium floutitanate and their mixed system has achieved good effect of improving the flame- retardant properties of down fiber. The experiment can be divided into the following steps:
1. Firstly start the down fiber flame-retardant treatment: Take proper drying of down fiber to scatter in distilled water. Adding suitable amount of citric acid to adjust pH value, add flame retardant. Reaction should be in a certain temperature of water bath. After the reaction completed, wash, filter, and dry until fluffy.
2. Use the limit oxygen index apparatus to measure the scope of limit oxygen index.
3. According to thermo-gravimetric curve of thermal weightlessness rate and the fastest thermal weight loss rate to analyze thermal stability. The thermal degradation process of down fiber is divided into three stages: the first stage is the dehydration reaction of down fiber. The second stage is a series of pure chemical reaction. The third stage is exothermic process.
4. Using whiteness instrument to test the whiteness of down fiber to show and process the yellowing degree of down fiber.
Following conclusions can be drawn through experiments: From the thermo-gravimetric curve, sodium tungstate mainly reduces the second stage weightlessness and potassium floutitanate mainly reduces the third stage weightlessness. They can respectively reduce the fastest thermal weight loss rate to increase down fiber thermal stability. Rate of residual carbon increases and hinders its burning. Sodium tungstate and potassium floutitanate can improve the flame- retardant properties of down fiber of different levels, but their mixed system has a better flame-retardant effect.
There’s not big influence on surface structure and whiteness of the down fiber.
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Chromium Behavior in Ammonium Paratungstate Crystallization Process 2/2
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- Category: Tungsten Information
- Published on Wednesday, 06 January 2016 18:54
2. Concentration of WO3 will affect the precipitation rate of chromium in the crystallization process of APT
Set the crystallization conditions like follows: the concentration of NH4OH is 2.76mol/L,195 g / L, 238 g / L, 258 g / L, 295 g / L; adding chromium acetate by the mass ratio of Cr/WO3=0.5%; stirring speed for 300rad/min; temperature of 100℃; ending point pH crystallization equals to7.0. Making the figure that effect of Cr-doped content on chromium concentration in APT powder as below:
Remark: The horizontal coordinate is precipitation rate of chromium (%), and the vertical coordinate is initial concentration of WO3(mol/L).
On the picture we can see that the initial concentration of WO3 increased from 170g/L to 295 g/L, and the precipitation rate of Cr decreased from 81% to 59%. Therefore, we can get that with the initial concentration of WO3 increased, the precipitation rate of Cr decreased. Furthermore, （NH4）2WO4 will promote the dissolution of Cr(OH)3, the balance of precipitation—dissolution of chromium in the higher concentration of WO3, the higher Cr ion concentration, the lower rate of chromium precipitation.
3. Effect of stirring speed on precipitation rate of chromium is shown as following:
Remark: The horizontal coordinate is stirring speed (rad/min), and the vertical coordinate is precipitation rate of chromium (%).
The speed increases from100rad/min to 500rad/min, the precipitation rate of chromium decreased from 84.3% to 37.9%. We will draw that increasing the speed of stirring leads chromium precipitation rate decreased. While stirring is conducive to the precipitation of chromium and promote formation and growth of Cr(OH)3 crystal, but precipitation rate of chromium reduce significantly. Because in the process temperature reaching to 100℃, ammonia volatilizing rapidly with the temperature increasing, and the concentration of pH and OH- has been greatly decreased.
Based on the analysis above, adding chromium in the crystallization of ammonium paratungstate can prepare apt powder containing chromium. Chromium in APT mainly exist in the form of Cr(OH)3, and without saturation. Increasing the initial concentration of WO3 and stirring speed will lead to rate of precipitation of chromium decreased.
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Chromium Behavior in Ammonium Paratungstate Crystallization Process 1/2
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- Category: Tungsten Information
- Published on Wednesday, 06 January 2016 18:39
Tungsten carbide made by doped grains is widely used in modern tools, wear resistance, high temperature resistance and corrosion resistance materials depending on the properties of high melting point, hardness and strength. There are many inhibitors to control the growth of tungsten carbide grains, among them Cr3C2 and VC are commonly used, but Cr3C2 has the better inhibition effect. In the present, carbide powder is mixed with tungsten powder and carbon to prepare WC powder containing the inhibitors. However, because inhibitors are not uniform, it leads part of WC grains non - expected growth, thus affects properties of cemented carbide. In this paper, a new way to dope chromium in the crystallization of ammonium paratungstate is put off, and the performance of Cr was analyzed.
Adding chromium acetate(CH3COO)3Cr into ammonium tungstate(pH≥9), crystallization to get ammonium paratungstate (APT) with chromium. The reactions are as follows
(CH3COO)3Cr=(CH3COO)3 3-+Cr3-
Cr3-+3OH-=Cr(OH)3↓
Ksp=6.3*10-33(25℃) Ksp is the concentration multiplication of Cr(OH)3
pH value of initial and total precipitation on different initial concentration of Cr is shown as below:
Chromium doped in APT crystallization, it has varieties of behavior, and we analyze the following three points:
1. Different content chromium affects it in APT powder, with the amount of chromium increasing, chromium in APT powder increases linearly. Cr(OH)3 with unsaturation is the main precipitation of chromium in APT. Controlling the content of chromium in the crystallization can produce APT with different content chromium.
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Tungsten Trioxide Doped Films Preparation
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- Category: Tungsten Information
- Published on Wednesday, 06 January 2016 17:49
Tungsten trioxide (WO3) doped film is an excellent hydrogen sensitive material, it has been widely studied and applied because of its good electrochromic and gas electrochromic, photochromic, electrochemical properties, especially in the gas photochromic properties of gas sensors. In the catalytic precious metals platinum (Pt) palladium (Pd), etc., WO3film has good gasochromic effect to H2 at room temperature, which shows it is an important functional material.
The temperature of tungsten trioxide film prepared by sol-gel method and the Combination of DC magnetron sputtering doped with Pd (or Pt) crystallization is higher than that of pure tungsten trioxide film. There are small amount of crystalline structure at 460 ℃ annealing treatment. The spectrophotometer test of results shows that: pure WO3 gel film has a high light transmittance (> 90%), but mixed with palladium or platinum thin film doped transmittance decreased significantly; and in the same condition of temperature, palladium-doped film doped is higher than the transmittance of the film . The transmittance of platinum-doped film sample increases by the annealing temperature at 100 ℃, 200 ℃, 300 ℃, 400 ℃, 500 ℃ .The film transmittance is gradually decreased, which is consistent with doped tungsten trioxide films.
The preparation of tungsten trioxide doped Pt (Pd) film based on the sol-gel method and the DC magnetron sputtering method, in the preparation of tungsten acid sol was added H2O2, ethanol can enhance the stability of the acid sol. When the molar ratio of H2O2 and tungsten acid is 1: 2, ethanol and acid volume ratio of 1: 2, the sol keeps long time, and the film plays a preservation effect. Tungsten trioxide surface becomes relatively flat after 100 ℃ annealing process, its molecules are tetrahedral structure. Tungsten trioxide surface becomes relatively flat after 400 ℃ annealing process, its molecules becomes cube structure too.
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Nano Tungsten Trioxide Hydrothermal Method
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- Category: Tungsten Information
- Published on Wednesday, 06 January 2016 17:36
The methods of Hydrothermal and Water Bath belong to the solution method for preparing tungsten trioxide (WO3), it’s characterized by small experimental cost, low energy consumption, materials, degree of crystallinity and purity, which becomes the first choice for the preparation of WO3.The application of modern nano materials science and technology enhances the performance of the material, or shows some unexpected properties. The preparation of nano tungsten trioxide is based on the hydrothermal method for the experimental approach, nano and tungsten trioxide materials.
The preparation of cubic monoclinic nano particulate WO3, WO3 • H2Oand layered massive flower-like WO3 • H2O based on Na2WO4•2H2O as raw materials, CTAB and oxalic acid supplement aids, by hydrothermal method and the preparation of the water bath method. After the sintering process,WO3 • H2O changes WO3, and it keeps the original block and flower-like morphology. Three samples of the morphology of gas sensing tests show that the optimum operating temperature is 300 ℃, and flower-like structure shows the highest sensitivity, which shows the factors affecting the course of the reaction, mainly attributable to obtaining WO3 • H2O which is not easy to reunite and lay porous three-dimensional structure.
Research Indicates:
(1) Taking Na2WO4•2H2O as raw materials, CTAB and oxalic acid supplement aids in favor of changing the reaction rate, the reaction time decreases from more than 24h shortened to less than 8h.
(2) Alkaline hydrothermal method is also capable of producing nanometer tungsten trioxide product, the need to expand the pH ranges from 3.5 to 8.9.
(3) The obtained nano-tungsten trioxide has a difficult reunion and layered porous, the average particle size of the particles is about 1μm.
(4) Tungsten trioxide as additives products has better dispersion, and WO3 in gas sensing, electrochromic, chemical catalysis and electrochemical aspects show excellent performance.
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Harms of As,F in Ammonium Paratungstate Wastewater
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- Category: Tungsten Information
- Published on Wednesday, 06 January 2016 17:28
Ammonium paratungstate (or APT) is a white crystalline salt of ammonium and tungsten, with the chemical formula (NH4)10(H2W12O42)·4H2O.
Ammonium paratungstate is produced by separating tungsten from its ore. Once the ammonium paratungstate is prepared, it is heated to its decomposition temperature, 600 °C. Left over is WO3, tungsten(VI) oxide. From there, the oxide is heated in an atmosphere of hydrogen, reducing the tungsten to elemental powder, leaving behind water vapor. From there, the tungsten powder can be fused into any number of things, from wire to bars to other shapes.
With the continuous development of China's tungsten industry, tungsten resources get fewer and fewer. As, F and other elements were exploited, associated with the main elements of W, of which the posterior segment of the treatment process, resulting in arsenic fluorine wastewater. As exists mainly as the form of arsenate and arsenite ions. As compounds are carcinogens, trivalent arsenic is the most toxic , such as arsenic (As2O3). Chronic arsenic poisoning goes into the digestive system mainly through the diet , making people lose appetite, diarrhea and constipation alternately, indigestion, hepatomegaly, or even cirrhosis. F is one of the essential trace elements, the appropriate amount of F is beneficial to human health, but too much can cause fluorosis, such as dental fluorosis and skeletal fluorosis and other ailments, and even induce tumors.
An ammonium paratungstate (APT) production line with an annual output of 3 000 t has been built in Yunnan, which was put into production in 2009. Currently, production of 1 t of ammonium paratungstate products produced 4 t ~ 5 t of wastewater, therefore process of ammonium paratungstate wastewater treatment must be explored to meet current production needs.
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