Abstract: The invention is directed to ammonium paratungstate decahydrate containing at least 75% of crystals having a length of at least 200 ?m and having a ratio of length to width of less than 4.5:1.

Abstract: A method for preparing ammonium heptamolybdate with the steps of: i) adding a molybdenum-containing organic phase to a liquid-liquid reextraction apparatus or to a desorption apparatus, and ii) directly cold-crystallization ammonium heptamolybdate by cooling the resulting reextraction or desorption solution.

Abstract: The invention is directed to ammonium paratungstate decahydrate containing at least 75% of crystals having a length of at least 200 ?m and having a ratio of length to width of less than 4.5:1.

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 process for the continuous preparation of ammonium paratungstate hydrate by back reextraction of a tungsten-laden organic phase with an ammonia-containing aqueous solution in a mixer-settler apparatus. The reextraction is carried out at an NH3:W molar ratio of from 0.83 to 1.30, and a volume feed ratio of the tungsten-laden organic phase to the ammonia-containing aqueous solution of from 5 to 25. The above crystalline is in high purity and in high yield. The production method can 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 process for the continuous preparation of ammonium paratungstate hydrate by back reextraction of a tungsten-laden organic phase with an ammonia-containing aqueous solution in a mixer-settler apparatus. The reextraction is carried out at an NH3:W molar ratio of from 0.83 to 1.30, and a volume feed ratio of the tungsten-laden organic phase to the ammonia-containing aqueous solution of from 5 to 25. The above crystalline is in high purity and in high yield. The production method can 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: A method for preparing ammonium heptamolybdate with the steps of: i) adding a molybdenum-containing organic phase to a liquid-liquid reextraction apparatus or to a desorption apparatus and adding an ammonia-containing aqueous solution to this reextraction or desorption apparatus, and ii) directly cold-crystallizing ammonium heptamolybdate by cooling the resulting reextraction or desorption solution.

Abstract: The invention relates to a process for recovering valuable metals from a superalloy which has the steps of digesting the superalloy in a salt melt. The salt melt contains 60-95% by weight of NaOH and 5-40% by weight of Na2SO4.

Abstract: A process for preparing nickel hydroxide by alkaline precipitation from nickel salt solutions in the presence of complexing agents, in which the precipitation is carried out at at least two different locations in the same mother liquor with different precipitation kinetics at the different locations and the mother liquor is mixed prior to agglomeration of the precipitated primary crystals, is described.

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: A process for reducing the content of alkali metal impurities (e.g., potassium) in ammonium metallate solutions is described. The process involves subjecting a feed solution containing ammonium metallate and alkali metal impurities to membrane filtration. The membrane filtration results in the formation of a retentate having a reduced level alkali metal relative to the feed solution, and a permeate containing substantially the balance of alkali metal. The permeate may also be further treated, to remove alkali metal there from, by passage through a cation exchange column, thereby forming a cation exchange treated permeate that may be combined with the retentate of the membrane filtration step.

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 relates to a method for producing metal hydroxides or alkaline metal carbonates by anode dissolution of the corresponding metals and precipitation of the hydroxides or alkaline carbonates in an aqueous medium. The anode dissolution of the metal components is carried out in the anode compartment of a three-compartment electrolytic cell. An aqueous auxiliary salt solution is fed to an intermediate compartment that is disposed between the anode compartment and the cathode compartment and that is separated therefrom by a porous membrane. An at least not alkaline metal salt solution is continuously taken from the anode compartment while an alkaline auxiliary salt solution is continuously taken from the cathode compartment. The at least not alkaline metal salt solution and the alkaline auxiliary salt solution are combined outside the electrolytic cell for the purpose of precipitating metal hydroxides or alkaline metal carbonates.

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: A process for reducing the content of alkali metal impurities (e.g., potassium) in ammonium metallate solutions is described. The process involves subjecting a feed solution containing ammonium metallate and alkali metal impurities to membrane filtration. The membrane filtration results in the formation of a retentate having a reduced level alkali metal relative to the feed solution, and a permeate containing substantially the balance of alkali metal. The permeate may also be further treated, to remove alkali metal there from, by passage through a cation exchange column, thereby forming a cation exchange treated permeate that may be combined with the retentate of the membrane filtration step.