Process for producing an aqueous solution containing a source of chromium (iii)

Abstract

In a method for manufacturing an aqueous solution containing a source of chromium (III) according to the present invention, an aqueous solution containing trivalent chromium is added to an aqueous solution of an inorganic alkali under the condition of a reaction liquid temperature of 0° C. or more and less than 50° C., so that the amount of the trivalent chromium is not locally excessive with respect to the amount of the alkali, to produce chromium hydroxide, and then the chromium hydroxide is dissolved in an aqueous solution of an acid to obtain an aqueous solution containing a source of chromium (III). Preferably, after production of the chromium hydroxide, filtration is performed, and the chromium hydroxide is washed with water until the conductivity of the filtrate is 5 mS/cm or less.

1 . A method for manufacturing an aqueous solution comprising a source of chromium (III), characterized by adding an aqueous solution comprising trivalent chromium to an aqueous solution of an inorganic alkali under the condition of a reaction liquid temperature of 0° C. or more and less than 50° C. so that the amount of the trivalent chromium is not locally excessive with respect to the amount of the alkali, to produce chromium hydroxide, and then dissolving the chromium hydroxide in an aqueous solution of an acid. 
     
     
         2 . The manufacturing method according to  claim 1 , wherein the aqueous solution of an acid is an aqueous solution in which an organic acid or an inorganic acid is dissolved. 
     
     
         3 . The manufacturing method according to  claim 1 , wherein the aqueous solution of an acid is an aqueous solution in which two or more acids are dissolved. 
     
     
         4 . The manufacturing method according to  claim 1 , wherein after production of the chromium hydroxide, filtration is performed, and the chromium hydroxide is washed with water until the conductivity of a filtrate is 5 mS/cm or less. 
     
     
         5 . The manufacturing method of  claim 1 , wherein the chromium hydroxide has a degree of aggregation of 10 or more and less than 70, and an average particle diameter D of 40 to 200 nm, the degree of aggregation being represented by the ratio MV/D of a volume average particle diameter MV measured by a particle size distribution measurement apparatus to an average particle diameter D measured from a scanning electron microscope image. 
     
     
         6 . The manufacturing method of  claim 1 , wherein the chromium hydroxide to be dissolved in the aqueous solution of an acid is in a state of a slurry of the chromium hydroxide suspended in water, and wherein the slurry comprises substantially no impurity ion. 
     
     
         7 . An aqueous solution comprising a source of chromium (III) obtained by a manufacturing method of  claim 1 , used for metal surface treatment or trivalent chromium chemical conversion treatment. 
     
     
         8 . An aqueous solution comprising a source of chromium (III) obtained by a manufacturing method of  claim 2 , used for metal surface treatment or trivalent chromium chemical conversion treatment. 
     
     
         9 . An aqueous solution comprising a source of chromium (III) obtained by a manufacturing method of  claim 3 , used for metal surface treatment or trivalent chromium chemical conversion treatment. 
     
     
         10 . An aqueous solution comprising a source of chromium (III) obtained by a manufacturing method of  claim 4 , used for metal surface treatment or trivalent chromium chemical conversion treatment. 
     
     
         11 . An aqueous solution comprising a source of chromium (III) obtained by a manufacturing method of  claim 5 , used for metal surface treatment or trivalent chromium chemical conversion treatment. 
     
     
         12 . An aqueous solution comprising a source of chromium (III) obtained by a manufacturing method of  claim 6 , used for metal surface treatment or trivalent chromium chemical conversion treatment. 
     
     
         13 . The manufacturing method of  claim 2 , wherein the chromium hydroxide has a degree of aggregation of 10 or more and less than 70, and an average particle diameter D of 40 to 200 nm, the degree of aggregation being represented by the ratio MV/D of a volume average particle diameter MV measured by a particle size distribution measurement apparatus to an average particle diameter D measured from a scanning electron microscope image. 
     
     
         14 . The manufacturing method of  claim 3 , wherein the chromium hydroxide has a degree of aggregation of 10 or more and less than 70, and an average particle diameter D of 40 to 200 nm, the degree of aggregation being represented by the ratio MV/D of a volume average particle diameter MV measured by a particle size distribution measurement apparatus to an average particle diameter D measured from a scanning electron microscope image. 
     
     
         15 . The manufacturing method of  claim 4 , wherein the chromium hydroxide has a degree of aggregation of 10 or more and less than 70, and an average particle diameter D of 40 to 200 nm, the degree of aggregation being represented by the ratio MV/D of a volume average particle diameter MV measured by a particle size distribution measurement apparatus to an average particle diameter D measured from a scanning electron microscope image. 
     
     
         16 . The manufacturing method of  claim 2 , wherein the chromium hydroxide to be dissolved in the aqueous solution of an acid is in a state of a slurry of the chromium hydroxide suspended in water, and wherein the slurry comprises substantially no impurity ion. 
     
     
         17 . The manufacturing method of  claim 3 , wherein the chromium hydroxide to be dissolved in the aqueous solution of an acid is in a state of a slurry of the chromium hydroxide suspended in water, and wherein the slurry comprises substantially no impurity ion. 
     
     
         18 . The manufacturing method of  claim 4 , wherein the chromium hydroxide to be dissolved in the aqueous solution of an acid is in a state of a slurry of the chromium hydroxide suspended in water, and wherein the slurry comprises substantially no impurity ion. 
     
     
         19 . The manufacturing method of  claim 5 , wherein the chromium hydroxide to be dissolved in the aqueous solution of an acid is in a state of a slurry of the chromium hydroxide suspended in water, and wherein the slurry comprises substantially no impurity ion.