Crystallization method of ammonium paratungstate

Abstract

The invention discloses a crystallization method of ammonium paratungstate and relates to a production method of ammonium tungstate by adopting hydrometallurgy. The method is characterized in that the invention has a crystallization process that ammonium paratungstate crystal seeds are added into ammonium tungstate solution when the solution is evaporated and concentrated to appear microcrystalline particles for isothermal crystallization under the solution temperature of 90-95 DEG C for 20-40mins; the solution is then heated up to boil and added with weak aqua ammonia to adjust the pH value of the ammonium tungstate solution to 8.0-8.5 and then treated with feeding and filtering when the density of mother liquor reaches 10.8 to 1.10 g / cm <3>; the solution is again washed with the weak aqua ammonia and deionized water and dried to obtain the ammonium paratungstate crystals with large particle size and uniform distribution. The method of the invention effectively controls the crystallization of the ammonium paratungstate through the measures of removing fine crystals through the weak aqua ammonia, adding the crystal seeds, controlling the evaporation speed, etc.; in addition, the produced ammonium paratungstate crystals with large and controllable particle size are uniform and smooth; and the technology is simple and easy to be operated.

Description

technical field [0001] A method for crystallizing ammonium paratungstate relates to a method for producing ammonium tungstate by adopting a hydrometallurgical method. Background technique [0002] With the continuous development of new types of cemented carbide and tungsten wire for lamps, more and more stringent requirements are put forward for the chemical composition, Fischer particle size, particle size distribution and crystal morphology of ammonium paratungstate as raw material. Some users require The particles are fine, reaching the micron or even nanometer level; some users require coarse particles and perfect crystal morphology, and this patent mainly solves the latter problem. [0003] At present, the production methods of ammonium paratungstate mainly include neutralization method, evaporation method, ion exchange and extraction method. Evaporation method is often used in industrial production, but when preparing ammonium paratungstate by evaporation method, it is...

AI Technical Summary

Problems solved by technology

Scholars at home and abroad have used adding seeds or ammonium tungstate solution (NH 4 ) 2 WO 4 Methods Some experiments were carried out: by adding seed crystal method, large particles of ammonium paratungstate could be obtained, but the distribution was uneven and the crystal morphology was poor; adding ammonium tungstate solution (NH 4 ) 2 WO 4 The method can modify the crystal form, but cannot obtain large particles of ammonium paratungstate

At present, there is no research and report on the use of seed crystals and dilute ammonia water to control the crystallization of ammonium paratungstate