SU1659359A1 - Method of separating chromium from aluminate solution - Google Patents

Abstract

The invention relates to the field of non-ferrous metallurgy and can be used in the production of alumina. The purpose of the invention is to reduce the loss of alumina and the consumption of aluminum. For this, the aluminate solution is treated with aluminum at 80-100 ° C to a ratio of: Cr + 0 (1.5-2.0) .1.0, the aluminate solution is separated from the precipitate, the last solution in acid. Alumina hydroxide is separated from the aluminate solution. The mother liquor after separation of the aluminum hydroxide is mixed with the solution after the precipitate has dissolved, and at a temperature of 80-100 ° C and pH 7.0-8.5 the precipitate is separated — basic chromate chromate. This method reduces the loss of alumina from 1, 5-4.1% to 0 009-0.015%, the consumption of aluminum is 3-4 times, to obtain a by-product with a chromium content of at least 60% Cg203. 4 tab. (Ls

Description

The invention relates to non-ferrous metallurgy and can be used in the production of alumina.

The purpose of the invention is to reduce the loss of alumina and the consumption of aluminum.,

Example. 1 l aluminate solution with the content, g / l: №200бщ 12 0.4; No. 98.35; AlaOa 102.1; CO2 1.0, is placed in the reactor and 1.0 g of metallic aluminum is added in the form of chips up to 3 mm in size. The reaction mixture is thermostated at 85-100 ° C for 1 hour in a hermetically sealed reactor, in which the following chemical reaction takes place:

 + AI + 4H20

 Cr (OH) 3J + AI (OH) 4 + OH. (one)

The ratio of trivalent chromium, isolated as Cr (OH) 3, and hexavalent, remaining in the aluminate solution in the form of CrO, is 1.70: 1. Chromium hydroxide, the amount of which is 0.85 g, after separation from the solution, is washed from impurities with water and treated with 10% sulfuric acid in a ratio: per g Cr (OH) g - 14.2 ml HaSOi - to form soluble sulfate chromium Cr2 (504) s-1 8H20

The filtered aluminate solution is fed to the release of alumina, and the mother liquor, usually soda-bicarbonate solution, is fed to the second stage. Chrome Purification Mother Solution with

Os

ate you ate

content, g / l. 112.6 Mak200bsch. 46.8 Ma20kb; 0.02 0.37 Cr203 - fed to the reactor and soluble chromium sulfate is introduced. The prepared solution with a pH of 7.5 is stirred in a tightly closed reactor, rotating inside a thermostat, for 2 hours at 90 ° C. The process of separating chromium from the mother liquor is accompanied by the following chemical reaction.

Cr (OH) +2 + NSgO 4 COHONMSHA (2)

As a result of this reaction, 1.33 g of insoluble brown precipitate is formed - the main chromium (III) chromate, which, after washing with water and drying at 105-120 ° C, contains, in wt.%: 74.3 Cr 203; 24.5 H20 and 1.2 (Na20 + + C02 + S03). The degree of purification of the alumina production solution from chromium is 98.0%, the chromium-containing product can be used in the chemical industry,

In tab. 1-3 shows the results of studies on the purification of alumina production solutions from chromium according to the proposed method.

According to the data given in table. 1, given the degree of purification of the solution from chromium at a consumption of aluminum equal to 0.7-1.5 g per 1 g of Cg and the ratio of Cr (lll): Cr (VI) - 1.5-2.0: 1.0.

In tab. 2 shows the dependence of the degree of purification of the solution from chromium by the proposed method on the temperature. As can be seen from this table, the temperature limit, equal to 80-100 ° C, is justified by a decrease in the degree of purification of aluminate solutions from chromium when it exceeds the limits of this limit,

According to the data of Table 3, the degree of purification of the solution from chromium, equal to 95-98%, can be achieved if the pH value of the mother liquor is maintained at

0

five

0

The second stage of the purification process is in the range of 7.0-8.5.

In tab. 4 shows the loss of alumina with slag in this method.

Alumina loss is determined by quality. The final product of purification of the sediment is Cg (OH) 2 NSGSm. If we consider that the degree of purification of technological solutions from chromium by the proposed method is, depending on the consumption of aluminum, 95- 98%, and the content in the final purification product is 0.6-0.9%, then the loss of alumina with sediment Cg (CH) 2 NSGSm is not more than 0.009-0.015%. Under industrial conditions, the loss of alumina due to incomplete separation of the precipitates and poor-quality conversion of the Cg (OH) 3 precipitate into the soluble form may increase to 0.015-0.025%, which is incomparably lower than in the known method.

This method allows reducing alumina losses from 1.5-4.1% to 0.009-0.015%, reducing aluminum consumption by 3-4 times, to obtain a by-product with a chromium content of at least 60% Cr203.

Claims (1)

Invention Formula The method of purifying the aluminate solution from chromium, including treating the solution with metallic aluminum, characterized in that, in order to reduce the loss of alumina and the consumption of aluminum, the 5th solution is treated with aluminum at 80-100 ° C to a Cr + 3: Cr + g ratio (1, 5-2.0) 1.0. the aluminate solution is separated from the precipitate, the latter is dissolved in acid, and aluminum hydroxide is separated from the eluate solution, the mother liquor after separation of aluminum hydroxide is mixed with the solution after dissolving the precipitate and at a temperature of 80-100 ° C and pH 7.0- 8.5 precipitate — basic chromate chromate. five 0 0 five Table 1 table 2 Table 3 Table 4