JPS6229361B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating nickel iodide and nickel sulfate in an aqueous solution containing both salts.
More specifically, the present invention relates to a method for separating nickel iodide and nickel sulfate that remain after hydrogen is generated by adding nickel metal to a mixed acid aqueous solution consisting of hydrogen iodide and sulfuric acid.

A method for producing hydrogen and oxygen by using nickel, iodine, and sulfur dioxide as circulating reactants and decomposing water at an overall reaction temperature of 1000°C or less is already known (Shimizu et al., JP-A-1988-1993). ―
78394). In these methods, a mixed salt of nickel iodide and nickel sulfate is heated from 350°C to 400°C.
Heat and dehydrate at ℃ to make anhydrous mixed salt, or
After heating at 100°C to 350°C to form a mixture of nickel iodide anhydride and nickel sulfate monohydrate, nickel iodide is extracted from the mixture using absolute alcohol or alcohol containing 30% by weight or less of water. Both salts are separated by extracting only the salt. Although these methods are viable, they allow for separation by distillation for the separation of the iodide salt from the alcoholic solution or for the regeneration of the solvent alcohol, for which energy must be supplied; Therefore, the thermal economy of the process as a whole is deteriorated.

As seen in the present invention, the discovery of a method for separating nickel iodide and nickel sulfate with a high degree of separation without using an organic solvent and at a low temperature of 100°C or less has led to the simplification of the process. It is expected that this will be useful for improving thermal economy.

The solubility of nickel iodide in water is 59.7g.
Anhydrous salt/100g solution (20℃) is 64.6 (60℃), and that of nickel sulfate is 24.6 (20℃) 36.1
(60℃) (Chemistry Handbook, Basic Edition, P.789 Maruzen, 1975). However, in many other mixed salt-water systems, when two salts that share a metal ion are simultaneously dissolved in water, the solubility of one salt is significantly lower than when dissolved alone. A similar phenomenon was observed in the case of nickel iodide and nickel sulfate. In other words, in the water-nickel iodide-nickel sulfate ternary system in the temperature range around room temperature, the solubility of nickel iodide is about the same as in the water-nickel iodide binary system, but the solubility of nickel sulfate is is significantly reduced to several percent of the value in the two-component system.
The value will be approximately. For example, in a three-component system prepared at a ratio of 20 moles of water to 1 mole of each anhydrous salt of nickel iodide and nickel sulfate, the solubility of nickel iodide and nickel sulfate at 20°C is 53.9 g of anhydrous salt, respectively. /100g solution, and 0.483g anhydrous salt/100g solution. In this case, the molar ratio of the dissolved amounts of both salts in the solution is NiI ₂ /NiSO ₄ =55.1, and the solid phase contains only a trace amount of nickel iodide. From this, it is possible to separate nickel iodide and nickel sulfate by taking advantage of the large difference in solubility in water.

Example Concentrated hydriodic acid containing 0.2 mol of hydrogen iodide (specific gravity
1.7) Concentrated sulfuric acid (specific gravity
1.84) 5.61ml was added to 34.2g of water to prepare a mixed acid solution of hydrogen iodide and sulfuric acid. This is HI and
This solution has a molar ratio of H ₂ SO ₄ and H ₂ O of 2:1:30. 200 with reflux condenser replaced with nitrogen gas
This mixed acid solution and 29.4 g of 0.5 mol of nickel metal were charged into a ml flask. The reaction was initially at room temperature and up to 60°C after most of the acid was consumed.

The generated hydrogen gas was collected on the water. The volume of hydrogen is 4.39 at room temperature and 1 atm, which is equivalent to 98.0% of the calculated amount. At the time when the generation of hydrogen was completed, some of the nickel sulfate had already crystallized, but in order to further promote crystallization, the reflux condenser was removed from the reaction vessel and the vessel was heated to remove water by evaporation. When 18.0 g of water had distilled out in this way, heating was stopped, and the reaction system was cooled to 20°C, and left to stand overnight to further crystallize nickel sulfate hydrate.

After the crystallization was completed, the solution phase and the crystallized material containing unreacted metal nickel were separated by filtration. The solution phase was heated and dehydrated at 150° C. in a nitrogen stream to obtain 30.5 g of solid.
According to chemical analysis, this solid contains 28.8 g of anhydrous nickel iodide and 1.5 g of unseparated anhydrous nickel sulfate. On the other hand, 100 g of water was added to the crystallized product containing nickel metal, and the resulting solution was filtered to separate the nickel metal. The solution was dehydrated by heating at 400° C. or lower to obtain 13.2 g of nickel sulfate anhydride.

As a result of the above, the molar ratio between the directly crystallized fraction, which contains almost no nickel iodide and consists of nickel sulfate, and
A residual liquid phase containing 9.5% nickel sulfate and the rest consisting of nickel iodide was separated.

Claims (1)

[Claims] 1. Nickel iodide is produced by adding nickel metal to a mixed acid aqueous solution consisting of hydrogen iodide and sulfuric acid to generate hydrogen, and then cooling an aqueous solution containing nickel iodide and nickel sulfate at 60°C or higher to room temperature. A method for separating nickel iodide and nickel sulfate by crystallization, which consists of separating nickel sulfate from a nickel iodide solution by utilizing the difference in solubility in water between nickel iodide and nickel sulfate.