Tungsten Oxide

Ammonium metatungstate (AMT) is an important compound product in the process of tungsten smelting. It is widely used. The preparation methods of ammonium acid are heat degradation and ion exchange, extraction, electrodialysis and neutralization. The neutralization method called ammonium tungstate acid, ammonium paratungstate production is one of the commonly used method, but this method can also be used for the preparation of ammonium metatungstate, it is used in acid solution and the crystallization of APT, by controlling the pH value of 3-4, heating, stirring and other means to strengthen the ammonium tungstate solution is gradually converted into ammonium metatungstate solution then, the precipitation of AMT crystals. Some scholars use ammonium paratungstate as raw material, adopt continuous solution conversion method,compare the effect of two kinds of acidizing agents, nitric acid and cationic resin on the basis of experiment. After that, nitric acid is selected as

Ammonium Metatungstate (AMT) is an important compound product in the process of tungsten smelting and it is widely used.  The common methods of preparing ammonium metatungstate include thermal degradation and ion exchange, extraction, electrodialysis and neutralization. Electrodialysis is the process of separating the electrolyte from the water by the selective conductivity of the ion exchange membrane under the action of the DC electric field. Under the action of the voltage, ammonium ion is used to form ammonium sulfate solution in the cathode solution of the circulation through anion exchange membrane. Electrodialysis method circulating pH = 9 ammonium metatungstate anode solution through the electrodialysis. Under the action of the voltage, the ammonium ion exchange membrane generates an ammonium sulfate solution through the anion in the circulating catholyte. The excess of ammonium ions in the anolyte begins to mass transfer, causing the pH to drop sharply due to the

The crystalization method of evaporation and extraction method in the preparation of APT will produce crystallization liquor, leaving about 5% -10% of the WO 3   and part of the S, P, As, Mo, K, Na and other impurities.  It resulting in it can not directly return to the process, in order to improve the recycle of metal, it is necessary to set up auxiliary processes to recycle WO 3  in the liquor. Artificial scheelite was the method of ammonium paratungstate crystallization liquor treatment, the main precipitant is CaCl 2 , the main purpose of the artificial scheelite method is to convert the WO 3  in the crystallization liquor into a very insoluble calcium tungstate (artificial scheelite), then return to the acid process or hot ball milling process. Artificial scheelite made in three directions: 1. CaCl 2  precipitated artificial scheelite → acid decomposition and partial molybdenum → crude tungstic acid → return to the main process; 2. Remove the molybdenum → precipi

Ion Exchange method is the process of preparing ammonium metatungstate.It is made from ammonium wolframate solution or ammonium paratungstate.  This method is also one of the main methods for preparing ammonium metatungstate  (AMT) at present. The main mechanism of ion exchange method is that use NH 4+  in H+ solution of strong acid or weak acid type H+ cation resin to process ion exchange. Under the condition of pH 3.5, H+ enters solution , cook for 5 hours at 98 °C. Converting ammonium tungstate into stable ammonium metatungstate solution. Then after evaporation and concentration, ammonium tungstate was converted to stable ammonium metatungstate solution. Again after evaporation and concentration, AMT crystals were prepared by freeze crystallization or spray drying. The resin saturated by NH 4+  is recycled after treatment with hydrochloric acid solution.  Because of the simple process and convenient control, the ion exchange method can avoid the formation of APT

Ammonium Metatungstate (AMT) is an important compound product in tungsten smelting process.It is widely used in areas.  The common methods of preparing ammonium metatungstate include thermal degradation and ion exchange, extraction, nanofiltration, electrodialysis and neutralization. Nanofiltration membrane is a new type of pressure driven separation membrane developed since 1980s. Nanofiltration method is a membrane separation technique, which is independent from reverse osmosis membrane technology. Filter membrane is the main focus of nanofiltration. The separation performance of nanofiltration membrane is between reverse osmosis and ultrafiltration membrane. It has a good removal effect on low molecular weight substances, high valence ions, low valence cations and anions. Therefore, some scholars used the nanofiltration method to prepare ammonium metatungstate (AMT) from the original solution of ammonium paratungstate (APT) crystallization. The separation of ch

The extraction method is a preparation process that use ammonium tungstate with ammonium tungstate solution as raw material.  This method is also one of the processes for preparing Ammonium Metatungstate (AMT) at presnt. The extraction principle of ammonium metatungstate (AMT) extraction method is similar to that of ammonium tungstate extraction method, which needs to experience four stages including extraction, water washing and stripping. The whole extraction process is carried out in a box-type mixer-settlers, the difference is that in the reverse extraction operation, the concentration and dosage of the extractant are different. In the process of production, using ammonium tungstate solution as raw material, ammonium metatungstate was extracted by solvent extraction, extraction of NH4+ ion from ammonium metatungstate solution by a cationic extractant, then, the solution of pH in the condition of 3~4, ammonium metatungstate solution was obtained by reverse extraction.