DE2219251B2 - METHOD FOR PRODUCING VANADIUM PENTOXIDE - Google Patents

Description

Vanadium-containing slags or vanadium-containing ores (e.g. magnetites) are preferably used as raw materials for the production of vanadium pentoxide. Acid and alkaline processes have been developed to extract the vanadium. The preferred procedure, particularly in the recovery from ores, the pyrogenalkalische digestion with alkali salts at 800-1300 ⁰ C. The disadvantage of this method is the simultaneous disruption of existing in the starting product SiCVVerbindungen to water-soluble alkali metal silicates. During the aqueous extraction of the roasted product, these go into solution together with the soluble alkali vanadates to a considerable extent.

To produce a low-alkali vanadium pentoxide, the vanadium is precipitated from these Solutions in the form of ammonium compounds are made in a neutral to slightly alkaline pH range. The silicic acid in the solution precipitates out almost completely and contaminates it Ammonium vanadate or the vanadium pentoxide obtained from it by decomposition, its value with it is greatly reduced. For example, a titanium magnetite is obtained in the pyrogenic-alkaline digestion following analysis:

V ₂ O ₃ = 1.3% Fe ₃ O ₄ = 78.5% TiO ₂ = 13.0% Al ₂ O ₃ = 4.0% SiO ₂ = 2.8%

JO

35

40

45

50

55

above 900 ⁰ C a sintering, the silica-rich during the extraction with water Vanadatlaugen with an SiO ₂ content of about 2 g /! supplies. The ammonium vanadate precipitated from it has the following analysis:

Na ₂ O

SiO ₂

= 41.5%
= 0.7%
= 2.8%

This purity does not meet today's requirements for many areas of application. With a good V ₂ O5 quality, the SiO ₂ and Na _{2 O content are below 0.5%.}

65 The aim of the invention is the removal of silica from vanadium-containing liquors before the Ainmoniumvanadatfällurg. This is achieved in that the silica dissolved in the aqueous extraction of the pyrogenic alkaline sinter is converted to insoluble alkali, in particular sodium aluminum silicate, and this is replaced by z. B. Separation by filtration.

Surprisingly, it was found that practically complete separation of the silica from vanadate liquors via sodium aluminum silicate compounds can be carried out even at room temperatures and in the neutral to weakly alkaline pH range. All water-soluble aluminum compounds, especially alkali aluminates, aluminum sulfate, aluminum and aluminum chloride, are suitable as precipitation reagents. For practically complete SiO ₂ deposition, it is expedient to maintain the Al: Si molar ratio of at least 1: 1 (FIG. 1).

The production of sodium aluminate is by adding aluminum hydroxide or oxide in the form of Bauxite or the pure compounds in the pyrogenic alkaline digestion of the vanadium ore or the Vanadium slag possible.

Application examples

The following examples show the dependence of the silica deposition on the reaction time Reaction temperature, the concentration of the precipitant and the pH of the lye to be decilified emerged.

example 1

1 l each of a weakly alkaline sodium vanadate solution with

18 g / l V
1.28g / SiO ₂
pH 9.8

was treated with varying amounts of solid sodium aluminate and stirred at 7O ⁰ C for 15 minutes. After decanting, the clarified liquor was _{examined for SiO 2} and V. Table 1 shows the values found.

Table 1

Original eye
De-descaled lye

Na aluminate g / l

0.67

1.1

1.54

4.4

MV Al: Si

0 _; 3: l

0.5: 1

0.7: 1

1: 1

1.5: 1

2: 1

pH

9.8

9.9 9.9 9.9 9.9 9.9 9.9

g'l

18th

18th
18th
18th
18th
18th
18th

SiO ₂

g / l

V / SiOi Mod; l

1.28

0.55

0.29

0.17

<0.03

<0.03

<0.03

14th

33
62
105
600
600
600

Degree of precipitation

> 98

> 98

> 98

In Example 2 1 1 of an alkaline Na vanadate liquor was used with each

17 g / l V
0.44 g / l SiO ₂
PH 9.9

adjusted to pH 7.5 by means of sulfuric acid. At room temperature, varying amounts of a 10%,

Table 2

acidic aluminum sulfate solution added. The pH of the lye to be decilified fell as a result down to 6.5. After a reaction time of 15 minutes, the precipitate which precipitated out quickly became through Decant separately from the excess liquor.

In Table 2 are the desilification results reproduced.

Ah (SOi) S- Molver- Solution ratio

10% Al: Si (cm3)

PH

g / l

S1O2

g / i

V / SiO2 module

Degree of precipitation%

Original eye
Silicified alkalis

100

4: 1

1.6: 1

8: 1

0.8: 1

0.4: 1

7.5

6.8 7.0 6.5 7.3 7.5 17

16.2
16.7
15.4

17th
17th

0.44

0.03
0.03
0.03
0.04
0.09

39

600
600
600
400
200

95
95
95
90
80

In Example 3 1 1 of a lye was used with each

20 g / l V
1.7 g / l SiO ₂
pH 10.5

heated to 70 ° C. and stirred in 3 g of solid sodium aluminate corresponding to the molar ratio Al: Si = 1: 1. The reaction time was varied between 3 and 30 minutes. After the precipitate had been separated off by centrifugation, SiO ₂ and V were determined in the clear liquor.

The results are shown in FIG. It is For example, it can be seen that the desilification is complete after about 15 minutes

Table 3

45

50 In Example 4, various aluminum salts were tested as precipitants. A lye was used

17.4 g / l V
1.13 g / l SiO ₂
pH 9.9

The amount of precipitant was set to a molar ratio of Al: Si = 1.2: 1. 90 ^° C. was selected as the reaction temperature and 15 minutes as the reaction time. After the reaction, concentrated H ₂ SO .; adjusted to pH 7, centrifuged and SiO ₂ and V determined.
The results are compared in table 3:

additive V g / l

S1O2

g / l

V / S1O2 module

Degree of precipitation

Original eye
Silicified alkalis

NaA102

Al2 (SO4) 3

AICI3 potassium alum 17.4

1.13

-15

17.1 0.04 430 96.5 16.7 0.06 280 95 16.7 0.06 280 95 16.8 0.06 280 95

In example 5, the silica removal was practiced on an industrial scale. This experiment shows at the same time one of the ways to technically carry out the decilification according to the invention.

Titanium magnetite was used as the starting material according to the analysis on page 1 of the present description. The ore was made on a grain <90μηι ball-milled and after mixing with 10%

finely ground sodium sulphate pelletized. The resulting pellets were then roasted at about 1200 ° C subject.

The solid sintered spheres obtained were leached with water. In Fig. 3, curve 1, is the solubility dependency of the silica - expressed as modulus = quotient of V and S1O2 - of the leaching temperature reproduced. It can be seen that the SiCh solubility increases with increasing leaching temperature. These alkalis are for the production of pure Ammonium vanadate not suitable. The invention is applied in such a way that sodium aluminate powder is poured between the pellets during the leaching process. The incoming water takes the Precipitant particles with, so that when the sodium vanadate and sodium silicate are extracted, the latter is separated Immediately reacted with dissolved sodium aluminate to form insoluble sodium aluminum silicate. After the leaching, neutralized, pressure filtered and the solid sodium aluminum silicate separated. The clear liquor is

practically SiCV-free and can be used immediately for the separation of: Vanadium can be used as ammonium vanadate (Fig. 3, curve 2).

Table 4 shows the difference in quality before ammonium vanadate with and without silica removal remove.

With the proposed method, it is only possible to use ores for vanadium extraction 2: u do the processing of which was previously uneconomical due to an increased S'iiCh content.

Table 4

S1O2

Na ₂ O

Ammonium vanadate

from silica containing 41.5 2.8 0.7

Lye
from de-silicified lye 42.5 0.2 0.3

1 sheet of drawings

Claims (4)

Patent claims: 1. Process for the production of vanadium pentoxide by pyrogenic digestion of ores or slags containing silicic acid-containing vanadium compounds with alkali salts at 800-1300 ⁰ C, aqueous extraction of the digested material and subsequent precipitation of the vanadium in the form of ammonium-vanadium compounds, ι ο and conversion of the same into the pentoxide, characterized in that the silicic acid which went into solution during the digestion from the vanadium-containing liquor is converted into insoluble alkali, in particular sodium-aluminum silicate, before ammonium vanadate precipitation. B. Filtration is separated. 2. The method according to claim 1, characterized in that the precipitation of the silica in neutral to slightly alkaline pH range is carried out. 3. Process according to claims 1 and 2, characterized in that the precipitation reagents water-soluble aluminum compounds, especially alkali aluminates, aluminum sulfate, or alums Aluminum chloride is used. 4. The method according to claims 1-3, characterized in that the precipitation reagent, for. B. Alkali aluminate, by adding aluminum hydroxide, aluminum oxide and / or bauxite in the case of pyrogenic alkaline Digestion of the ores or slags containing vanadium compounds are generated directly will.