Abstract: The invention is directed to a method for the production of ammonium paratungstate tetrahydrate by thermal treatment of ammonium paratungstate decahydrate in an aqueous suspension. The ammonium paratungstate tetrahydrate can be produced with high purity and high yield. The production method may furthermore be carried out in a simple and energy-efficient manner.

Abstract: The invention is directed to a method for the production of ammonium paratungstate tetrahydrate by thermal treatment of ammonium paratungstate decahydrate in an aqueous suspension. The ammonium paratungstate tetrahydrate can be produced with high purity and high yield. The production method may furthermore be carried out in a simple and energy-efficient manner.

Abstract: The invention is directed to a method for the production of ammonium paratungstate tetrahydrate by thermal treatment of ammonium paratungstate decahydrate in an aqueous suspension. The ammonium paratungstate tetrahydrate can be produced with high purity and high yield. The production method may furthermore be carried out in a simple and energy-efficient manner.

Abstract: Process for the electrochemical decomposition of precursors in powder form by introducing a powder batch between two electrodes of an electrolysis cell, electrodes being designed to be liquid-permeable, and the electrolyte flowing through the powder batch perpendicularly to the electrode surfaces, and electrolysis cell suitable therefor, which is essentially characterized in that at least one electrode has a structure which consists of a supporting pierced plate (5), an electrode plate (3) provided with perforations, and a filter cloth (4) arranged between the supporting pierced plate (5) and the electrode plate (3), and in that the cathode (6) is shielded from the cell by means of a liquid-permeable separator (7).

Abstract: The invention is directed to a method for the production of ammonium paratungstate tetrahydrate by thermal treatment of ammonium paratungstate decahydrate in an aqueous suspension. The ammonium paratungstate tetrahydrate can be produced with high purity and high yield. The production method may furthermore be carried out in a simple and energy-efficient manner.

Abstract: A process for recovery of valuable metals from superalloys by electrochemical decomposition is described, both electrodes being formed by the superalloy and the polarity of the electrolysis current being reversed with a frequency of from 0.005 to 5 Hz.

Abstract: Process for the electrochemical decomposition of precursors in powder form by introducing a powder batch between two electrodes of an electrolysis cell, electrodes being designed to be liquid-permeable, and the electrolyte flowing through the powder batch perpendicularly to the electrode surfaces, and electrolysis cell suitable therefor, which is essentially characterized in that at least one electrode has a structure which consists of a supporting pierced plate (5), an electrode plate (3) provided with perforations, and a filter cloth (4) arranged between the supporting pierced plate (5) and the electrode plate (3), and in that the cathode (6) is shielded from the cell by means of a liquid-permeable separator (7).

Abstract: Process for the electrochemical decomposition of precursors in powder form by introducing a powder batch between two electrodes of an electrolysis cell, electrodes being designed to be liquid-permeable, and the electrolyte flowing through the powder batch perpendicularly to the electrode surfaces, and electrolysis cell suitable therefor, which is essentially characterized in that at least one electrode has a structure which consists of a supporting pierced plate (5), an electrode plate (3) provided with perforations, and a filter cloth (4) arranged between the supporting pierced plate (5) and the electrode plate (3), and in that the cathode (6) is shielded from the cell by means of a liquid-permeable separator (7).

Abstract: A process for elution of rhenium adsorbed on strongly basic ion-exchange resins by means of highly concentrated aqueous hydrochloric acid solution is described, in which the ion-exchange resin is treated with aqueous solution containing an oxidizing agent.

Abstract: The invention relates to a method of extracting anions based on metals of groups IV B to VIII of the periodic table from aqueous solutions thereof, wherein compounds of general formula are used as extractants, in which a maximum of two of the R1, R2, R3 and R4 substituents represent hydrogen atoms and the remaining substituents represent identical or different alkyl or aminoakyl groups, which are optionally branched and which contain on average at least 5 C atoms.

Abstract: Process for the electrochemical decomposition of precursors in powder form by introducing a powder batch between two electrodes of an electrolysis cell, electrodes being designed to be liquid-permeable, and the electrolyte flowing through the powder batch perpendicularly to the electrode surfaces, and electrolysis cell suitable therefor, which is essentially characterized in that at least one electrode has a structure which consists of a supporting pierced plate (5), an electrode plate (3) provided with perforations, and a filter cloth (4) arranged between the supporting pierced plate (5) and the electrode plate (3), and in that the cathode (6) is shielded from the cell by means of a liquid-permeable separator (7).

Abstract: A process for recovery of valuable metals from superalloys by electrochemical decomposition is described, both electrodes being formed by the superalloy and the polarity of the electrolysis current being reversed with a frequency of from 0.005 to 5 Hz.

Abstract: A process for elution of rhenium adsorbed on strongly basic ion-exchange resins by means of highly concentrated aqueous hydrochloric acid solution is described, in which the ion-exchange resin is treated with aqueous solution containing an oxidizing agent.

Abstract: Tungstate solutions are purified by a precipitation process followed by two anion exchange processes to reduce molybdenum and arsenic impurity content. The precipitation involves acidification of the original highly basic tungstate solution to pH of 7 to 10 without addition of precipitating agents and separates out the bulk of impurities other than Mo, As. The first anion exchange process removes As. Then a remaining filtrate from the latter process is treated with sulfides to form thiomolybdates from impurity Mo content and the thiomolybdates are then separated out from the tungstate solution in a second anion exchange process.

Abstract: The present invention relates to a process for the production of pure ammonium metallates of the metals W, Mo, V, Cr and Re, wherein alkaline metal salt solutions are adjusted to a pH value in the range from 5 to 9 by reaction with CO.sub.2, these metal salt solutions are passed through an anion exchanger in carbonate form, wherein, in addition to the alkali metal carbonate solution, the metallate form of the ion exchanger is formed, the ion exchanger is then washed until free of alkali and is then eluted by means of aqueous ammonia to form ammonium metallate solutions and the anion exchanger in the OH form, wherein the anion exchanger is converted into the carbonate form by means of CO.sub.2 treatment and is recycled.

Abstract: Process for the production of pure tungsten and/or molybdenum solutions from sources, such as alkaline decomposition solutions, which are contaminated with tantalum, niobium, titanium, aluminium, tin, arsenic, phosphorus and/or silicon, by application of a three stage purification process of pH reduction, anion exchange and membrane electrolysis.

Abstract: Potassium tantalum fluoride substantially free from compounds of silicon and niobium is prepared from a crude tantalum-niobium salt solution by use of aqueous hydrofluoric acid having a dissolved content of a silicon compound by mixing the salt solution with a water-insoluble organic solvent for said salts; extracting the organic phase with aqueous medium; mixing the organic phase with silicon-contaminated aqueous hydrofluoric acid; mixing the organic phase with a hot silicon-free solution of an ionizable potassium compound, and separating and cooling the aqueous phase thereby precipitating potassium tantalum fluoride. The phases are separated between steps.