Method for removing potassium ions from ammonium perrhenate(VII)

Abstract

The subject of the application is a method for removing potassium ions from ammonium rhenate (VII) using recrystallization carried out with the addition of ammonium salts, which is characterized in that the salt to be purified is ammonium rhenate (VII) with an initial potassium content of <60 ppm, which is dissolved in water at a temperature of 45°C to 80°C, obtaining a solution of ammonium rhenate (VII) salt with a concentration of 3.0 to 6.8% by weight, to which one of the highly soluble ammonium salts is added, such as: ammonium nitrate (V) or ammonium chloride or ammonium sulfate (VI) in such an amount that in the obtained solution the ratio of the number of moles of ammonium ions originating from ammonium rhenate (VII) to the number of moles of ammonium ions from the introduced ammonium salt is in the range of 0.02 to 0.2, then the solution is hot filtered at a temperature in the range of 5°C — 20°C higher than the salt dissolution temperature, and the undissolved residue is directed to the recovery of rhenium and ammonium potassium salt by known methods,next, the mixture is cooled to a temperature in the range of 10°C to 30°C, at a constant speed in the range of 0.25°C to 0.75°C per minute with continuous stirring, the precipitated crystals are separated from the post-crystallization liquor by filtration, the post-crystallization liquor is combined with the undissolved residue and together directed to the recovery of rhenium and the ammonium potassium salt by known methods, the precipitate is washed on the filter in two stages, first with demineralized water cooled to a temperature of 0.5°C to 5°C in the amount of 10 to 50 cm3 for every 10 g of precipitated ammonium rhenate(VII), and then in the second stage with a mixture of isopropyl and ethyl alcohols at ambient temperature in a volume ratio of 1:10 to 10:1, using a mixture of alcohols in the amount of 10 to 50 cm3 for every 10 g of precipitated ammonium rhenate, where the aqueous washings are directed to the operation of dissolving the next portion of ammonium rhenate with demineralized water,and the alcohol washings are returned to the second stage of washing the crystalline product in the next purification cycle, the washed product is first dried for 2 to 5 hours at a temperature below or equal to 60°C, then the drying temperature is raised to 70°C and held for 12 to 18 hours, and finally the drying temperature is raised to 110°C and held for 3 to 5 hours.,