SU1321682A1 - Method of producing chromate dihydroxochromium (iii) - Google Patents

Abstract

The invention relates to the preparation of chromichromates, which are used, for example, in compositions for coating molds, in the preparation of high-base chromium (III) hydroxyl salts, to adjust the composition of acid chromate baths. The aim of the invention is to accelerate the process by increasing the filtration rate and increasing the yield of the target product. To achieve the goal, a solution of hydroxochrome (III) dichromate (CrONSg O) is used, which is heated to 50-70 ° C and a solution of sodium hydroxide is added to it with stirring to a final pH of 3.9-4.2. The resulting precipitate is separated by filtration, washed with water to colorless wash water, dried and analyzed. The duration of the process decreases from 2.5 days according to the prototype to 2 hours, the filtration rate increases from 0.04-0.10 to 0.65-0.8 hours, the yield of the product increases from 90% to 99%. 1 hp f-ly, 2 ill., 2 tab. (L

Description

The invention relates to the preparation of chromichromates, which are used, for example, in pjin formulations for coating molds, in the preparation of highly basic chromium (III) hydroxyl salts for the correction of the composition of acid chromatizing baths.

The aim of the invention is to accelerate the process by increasing the filtration rate and increasing the yield of the target product.

Example 1. 1.5 dm solution of hydroxochrome (111) dichromate with a content of 42.8 dm CrCOOSOCO is heated to 50 ° C, sodium hydroxide with a content of 60 s / dM NaOH is added over 20 minutes to a final pH value of 4.2 . The resulting suspension is kept at 50 ° C for 1 hour. The precipitate of the desired product, after separation for 10 minutes from the filtrate containing 0.08 g / cm Cg (III), is washed with water for 20 minutes to colorless industrial water and dried with obtaining of 39.3 g of the target product composition,%; Cr (III) 29.6; Cr (VI) 14.9; HgO 18.0 Filtration rate 0.8. The yield of Cr (III) in the product is 99%. The duration of the process is 2 hours.

The filtration rate according to the known method 0.04-0.12, you

3.9 1.9 2.0 2.0 2.0 2.1 2.3

4.2

1.9

2.0 2.0 2.0 2.2

2.5

pH

3.3 3.8 3.9

Cr (III) Cr (VI)

, 9 2.0 2.0 2.0 2.0 2.1 2.2

As can be seen from the table. I and 2 predla- In FIG. Figures 1 and 2 show the curves of the fueled product obtained at a 50-degree dependence on the yield of 70 ° C and pH 3.9-4.2, which is not inferior in dependence on Cr (III) to the product and the filtration rate of ions of dihydroxochrome (111) chromium .

mate, obtained by a known method

 so, i.e. the ratio of ions is consistent. As can be seen from FIG. 1 and 2, the optimum is stoichiometry and is equal to two. For the process, the temperature is

the course of chromium (III) in the target product is 90%, the duration of the conversion process is 2 days. The ratio of trivalent - / a to hexavalent in the product obtained by the known and proposed methods is equal to two, which corresponds to stoichiometry.

Example 2. A 1.5 dm solution of hydroxochrome (III) dichromate with a content of 42.8 g / dm CR (OH) Cr., Or is heated to 70 ° C, sodium hydroxide is added with a content of 60 g / dm NaOH over 20 minutes to a final pH of 3.9. The suspension obtained is held at 70 ° C for 40 minutes. The precipitate of the target product after separation for 12 min from the filtrate containing 0.07 d / m Cg (III), rinsed with water for 20 min to colorless industrial water - and dried to obtain 41.1 g of the target product composition,%: Cr (III) 28.4; Cr (VI) 14.1; H ,, 0 2.1,5. Filtration rate of 0.67. The output of Cg (III) in the product is 99%. The process takes 2 hours.

In tab. 1 and 2 show the dependence of the ratio of trivalent chromium to hexavalent in the resulting product on the precipitation temperature and on the pH value (at 60 ° C).

Table D

2.0 2.0 2.0 2.2

2.5

Table 2

4.0 4.1 4.2 j 4.3 5.0

pa 50-70 ° C for high yield and high filtration rate.

Claims (2)

1. A method of producing dihydroxo chromium (111) chromate, which includes precipitating the target product from a solution containing three- and hexavalent chromium ions, separating it from the mother liquor by filtration and drying, characterized in that. t- se five In order to speed up the process and increase the filtration rate and increase the yield of the target product, a solution of hydroxochrome (111) dichromate is used as the initial solution and precipitation is carried out with a solution of sodium hydroxide at 50-70 ° C. 2. The method according to claim 1, about tl and h and u and with the fact that, in order to ensure the purity of the target product, precipitation is carried out to a pH of 3.9-4.2. -ih 40 50 60 70 80 90 TI # 1 I g ABOUT 40 50 t; c 60 to 70 in FIG. 2 t.c Compiled by V. Totrov Editor N. Gunko Tehred A. Kravchuk Order 2716/15 Circulation 455 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, st. Project 4 Proofreader L. Patay