CS275701B6 - Process for producing ammonium paratungstate - Google Patents

Abstract

The essence of the solution is that it supplements the traditional processing of tungstic acid by ammonia leaching with a process of removing impurities from mother liquors, which arise during the subsequent crystallization of ammonium paratungstate. In the production unit upstream of the actual ammonia leaching, impurities concentrated in the mother liquors are precipitated by adding 25% ammonia water. These impurities are then not dissolved in the subsequent leaching and are removed from the process together with the unleached residues of raw tungstic acid.

Description

The subject of the invention is a technology for the production of ammonium paratungstate from crude tungstic acid, obtained by acid leaching of sintered carbide flakes and other tungsten-containing raw materials.

Previously established technologies for processing such tungstic acid use ammonia leaching at temperatures up to 100 ‘c and ammonia concentration up to 110 g / l to separate tungsten from other fractions, followed by separation of the undissolved residue. The obtained leachate is refined by the addition of activated carbon, or refined from arsenic by the addition of Mg salts. The extract thus obtained is then subjected to evaporative crystallization and, after cooling, the crystalline product - ammonium paratungstate - is separated from the concentrated residue. However, since the refined leachate is not completely pure, it contains tungsten hetero compounds with As, Si, Nb, Ta, Al, Fe ions, concentrating these impurities in the mother liquor and making it difficult to reuse it in the production cycle, which is economically necessary.

In the case of the commonly used circulation of mother liquors to the evaporative crystallization node, the impurities present are concentrated to such an extent that they degrade the crystals of the product. When it returns to the beginning of the process, to the acid leaching of tungsten raw materials, both the NH 2 ions and the soluble tungsten heterocomponents are contaminated in the wastewater.

These shortcomings are overcome by the crude tungstic acid processing technology of the present invention.

The present invention relates to a process for the production of ammonium paratungstate using ammoniacal leaching of crude tungstic acid and evaporation of the extracts obtained, characterized in that the mother liquor is mixed with 25% aqueous ammonia solution at the refining unit and the impurities are removed. min. After stirring for half an hour, crude tungstic acid is added to the resulting suspension, the ammonia content is adjusted to a value of min. 100 g NH 4 / l and the resulting mixture is leached at a temperature of min. 100 ‘C for min. 1 hour, then the mixture is cooled, the insoluble residues are separated off, the extract is subjected to evaporation and, after cooling, the paratungstate crystals are separated off, the remaining mother liquors being returned to their refining node.

Optimal conditions for leaching of crude tungstic acid are:

- temperature 110 C,

- reaction time 4 hours,

ammonium ion concentration 115 to 125 g / l, it being advantageous to adjust the ammonium ion concentration in the reaction mixture only after the addition of crude tungstic acid by adding the final fractions of evaporation vapor condensate, supplemented with water after washing the crystalline production or with demineralized water.

The optimal dosage of the individual components for the preparation of the leaching mixture is 160 parts by weight of 25% ammonia water and 80 parts by weight of mother liquors to exclude 100 parts by weight of crude tungstic acid.

By pre-lining the leaching mixture before the actual ammoniacal leaching of crude tungstic acid, precipitation of all impurities from the mother liquors returned to the production process is achieved. Under the described ammonia leaching conditions, the already precipitated impurities are then not redissolved and discharged together with the undissolved portions of crude tungstic acid out of the production process.

In addition, the increased temperature of ammonia leaching prevents the formation of less stable chemical bonds between tungstate ions in solution with impurity ions (especially Si, Nb, Ta, Al, Fe ...). This also partially limits the formation of heteropolysulphon compounds.

The production process according to the invention then results in ammonium paratungstate crystals of high chemical purity and at the same time of higher yield than the technology used hitherto.

Example

000 kg of roasts from waste sintered carbides containing 810 kg of WO 2, 90 kg of Co, 40 kg of Ti and 2 kg of Fe were acid leached in dilute sulfuric acid. The acid filtrate contained 0.1 kg WO 2, 85 kg Co and 2 kg Fe. 875 kg of washed crude tungstic acid was fed to an ammoniacal leachate, which was 30 min. pre-presented suspension prepared by mixing 700 kg of mother liquor from the evaporation of the previous batch and 1400 kg of 25% ammonia water. After 4 hours of leaching at 110 DEG C., the ammonia concentration was adjusted to 110 g / l before closing the autoclave, the contents were cooled, 139 kg of undissolved residue containing 49.5 kg of WO50, 5 kg of Co and 40 kg of Ti were filtered off and the tungsten solution after purification on activated carbon, the ammonium ammonium was evaporated to a residue of 700 kg of mother liquor. The obtained 858 kg of ammonium paratungstate containing 760.4 kg of WO 2 was washed with 100 kg of demineralized water, and this water was used in the preparation of the alkaline leaching leach bath of the following batch of crude tungstic acid. The obtained ammonium paratungstate crystals contained less than 300 ppm Mo, less than 50 ppm Si and S and less than 20 ppm Na. The content of all other monitored impurities (As, Ca, Al, Cu, Ti, Mg, Sn, Pb, P) was less than 10 ppm.

Claims (3)

PATENTS 1. A process for the production of ammonium paratungstate using ammoniacal leaching of crude tungstic acid and evaporation of the obtained extracts, characterized in that the mother liquor is mixed with a 25% aqueous ammonia solution at the refining unit after the paratungstate is crystallized, removing impurities and . After stirring for half an hour, crude tungstic acid is added to the resulting suspension, the ammonia content is adjusted to a value of min. 100 g NH _3/1 and the mixture is leached at a temperature of min. 100 ° C for min. 1 hour, then the mixture is cooled, the insoluble residues are separated off, the extract is subjected to evaporation and, after cooling, the paratungstate crystals are separated off, the remaining mother liquors being returned to the refining node. 2. The process according to claim 1, characterized in that the leaching temperature is 110 DEG C., the reaction time is 4 hours and the ammonium ion concentration is 115 to 125 g / l, the ammonium ion concentration being adjusted only after the crude tungstic acid has been metered in, and this by adding end portions of the vapor condensate from the evaporation, supplemented by washing water of the crystals or demineralized water. 3. The process according to claim 1, characterized in that 160 parts, parts of 25% ammonia water and 80 parts, parts of leaching mother liquors of 100 parts, parts of crude tungstic acid are used in the dosing of the individual components for the preparation of the leach mixture, provided that: by evaporation, the extract is concentrated so that the remainder of the mother liquors again corresponds to 80 parts by weight.