DE1259858B - Process for the production of sulfates - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

COIb

German class: 12 i-17/96

Number:
File number:
Registration date:
Display day:

1259 858
A46032IVa / 12i
May 13, 1964
1st February 1968

In the manufacture of sulphates it is usually very difficult to obtain chlorides of both the same cation how to separate that of the sulphate to be produced as well as other contaminating accompanying elements. Around To meet the purity requirements of DAB 6, for example, sulphates must also, among other things Zinc sulfate, have such a low chloride content that this can be increased by adding silver nitrate solution an aqueous solution of the sulfate no longer gives any visible turbidity.

The chloride content that meets this purity requirement, for example zinc sulfate heptahydrate, however, is below 0.0005%, based on the crystallized salt.

In order to achieve such a low chloride content, it is first necessary to use very pure To run out of raw materials. In the production of zinc sulfate in DAB-6 purity, one must be made from metal Zinc white (in the so-called indirect process) can be used as the zinc chloride as a result of its high volatility is present in practically all industrial oxides in such large quantities that at their use as a raw material for the production of these DAB-6 goods, the above-mentioned purity requirements cannot be met.

Despite the use of pure raw materials for the production of the sulfates, it is necessary to use the same the first crystallization one or more times to solve the required by recrystallization to achieve a low content of chloride in the finished product.

What has been described using the example of zinc fulfate also applies to other metal sulphates that are to be presented in pure form, because chlorine or chloride ion is present in practically all technical processes and thus as an impurity ends up in raw materials normally used for the production of sulphates. To thus To get to the desired chloride-free sulfates, one is forced to start from pure metals or from starting from these oxides produced and the process for the production of sulphates

Applicant:

Grillo-Werke Aktiengesellschaft,

4100 Duisburg-Hamborn, Weseler Str. 1

Named as inventor:

Dr. Norbert Lowicki,

Helmut Niess, 4100 Duisburg-Hamborn

initially obtained crude product repeatedly (three to seven times) to recrystallize until the required Tolerance values can be achieved. Such a way of working forces you to accept high material and Manufacturing costs and the use of relatively extensive and expensive equipment.

Surprisingly, it has now been found that the chlorides of a number of heavy metals in pure acetone or in acetone-water mixtures of different compositions much easier are soluble than the corresponding sulfates of the cations in question.

The table below shows the solubilities of some chlorides and sulfates in pure acetone and in Acetone-water mixtures with 30 and 50% water content compiled as they are from experiments revealed.

I. Solubility of chlorides (each gram of salt per 100 ml of solvent) in

1. Pure acetone 16.3 g
0.039 g
0.74 g
2.80 g
56.83 g
0.011 g 2. Acetone-water mixture
70:30 3. Acetone-water mixture
50:50 ZnCl ₂ 89.7 g
1.04 g
35.3 g
2.1g
48.2 g
3.44 g 90.4 g
2.33 g
48.63 g
3.12 g
40.25 g
17.1g CuCl CuCl ₂ -2 H ₂ O.. FeCl ₂ FeCl ₃ 6 H ₂ O ... NaCl

709 747/526

π.

1. Pure acetone 0.012 g
0.004 g
0.027 g
0.37 g
0.012 g 2. Acetone-water mixture
70:30 3. Acetone-water mixture
50:50 ZnSO ₄ · _{7H 2} O
CuSO ₄ -5H ₂ O
FeSO ₄ · _{7H 2} O
Fe ₂ (SO ₄ ) ,,
Na ₂ SO ₄ · 1 OH ₂ O 0.052 g
0.010 g
0.060 g
1.61 g
0.076 g 0.269 g
0.061 g
0.062 g
6.79 g
0.362 g

It is clear from the values given above shows that it is due to the large differences in solubility between chloride and sulfate in acetone or acetone-water mixtures is possible, chloride contents as impurities in sulfate solutions are available to extract from these.

It is now known that undesirable admixtures or impurities from saline solutions

Example 1 zinc sulfate

1 m ^{3 of} a zinc sulfate solution with 150 to 170 g / l Zn and 0.7 to 2.0 g / l Cl is ^{mixed with 0.5 m 3 of} acetone and stirred for about 10 minutes. Another cubic meter of acetone is then allowed to run in over the course of a further 10 minutes while stirring continuously. It is

gene can be removed by liquid-liquid extraction. 20 possible, but not required, to do this beforehand The peculiarity of the extractant acetone allows extraction of the used acetone from the aqueous

it does, however, remove more easily soluble contaminants to be coupled with a second process step. After performing the liquid-liquid extraction to remove the chloride impurities from the sulfate solution you can namely by simple addition of further amounts of acetone the now pure, d. H. chloride-free sulfate from its solution fail directly.

It is known that salts can be precipitated from their solutions by adding a second liquid can. The prerequisite is that these salts are not soluble in the second added liquid, on the other hand, however, the added second liquid with the

Separate phase. Precipitation is over about 1 minute later. Salt and supernatant solution separate from each other almost immediately after stopping stirring and can be decanted or filtration can be easily and quickly separated from one another. The precipitated zinc sulfate heptahydrate contains less than 0.0001% Cl.

Example2

Copper sulfate

1 m ^{3 of} a copper sulfate solution with 80 to 100 g / l Cu and 0.5 to 1.0 g / l is mixed ^{with 0.5 m 3 acetone}

Solvent of the salt be infinitely miscible 35 and stirred for about 15 minutes. Then one leaves under got to. For this purpose, a further 500 liters of acetone have hitherto been run in and only continuous stirring

proceed as in example 1. The precipitated copper sulfate pentahydrate also contains less than

Alcohol used.

The procedure according to the invention for the preservation of sulfates, especially those with extremely low levels Chlorine content consists in using an aqueous sulfate solution, optionally containing chloride ions added once or several times with acetone and mixed with this intimately. By adding a a certain amount of acetone is first a liquid

0.001% Cl.

Example 3 Sodium Sulphate

1 m ³ sodium sulfate solution with about 100 g / l Na and 0.2 to 0.5 g / l Cl is in two portions of 0.5 m ^{3 each}

Liquid extraction carried out, in which the chloride added 45 acetone. It is as indicated in Example 2 ions in the acetone water phase, which proceed by addition. The precipitated sodium sulfate decahydrate forms the first portion of the acetone, pass over. also contains less than 0.001% Cl.
After this first process step has been carried out, it is clear that this work according to the invention

if a further amount of acetone is added to the mixture, which is essential for the production of sulfates whereby the sulfate from the now forming 50 advantages over the previously usual production concentrated Acetone-water mixture precipitates. The processes provides. In addition to the possibility now Purity of the sulphate to be recovered, d. H. its normal freedom from chloride, which can be obtained from technical processes of chloride ions can be processed by adjusting the oxides they contain, one can now in Concentration of the aqueous acetone solution in two simple, immediately successive arwissem Scope can be influenced arbitrarily. A pure chloride-free sulphate is obtained in 55 steps, it possible, for example, zinc chloride of zinc sulfate Another advantage of the above

at a final concentration of the acetone-water mixture of 70:30 to be separated off so largely that the final content of the chloride in the zinc sulfate heptahydrate obtained is about 0.00005. One Increasing the acetone concentration to 50% has only a very slight, analytically hardly detectable Effect. In contrast, when separating copper chloride from the corresponding sulfate penta-

Invention now also consists in the fact that the sulfates are not only used with their maximum water of crystallization can win, but also with a lower. Without the purity of what is produced The final chloride content of the sulfate can be compromised by increasing the temperature the sulfate solution and by increasing the sulfate content dissolved in the aqueous phase, for example

hydrate necessary to work towards a concentration of 50% zinc sulphate as trihydrate and copper sulphate as acetone water in order to gain a 1 ^ hydrate in this way. This way of working can produce a similarly good effect as in production
of zinc sulfate.

certain limits are set by the volatility of acetone. It is therefore only possible to use the

To increase temperature of the sulfate solution to about 40 to 45 ⁰ C. However, this temperature and, as already mentioned, the increased amount of sulfate in the aqueous phase is sufficient to achieve the effects described.

With the combined use of acetone in the extraction and precipitation of sulfates the sulfates of some trivalent ions remain dissolved in the acetone-water mixture, while the sulfates other trivalent ions as well as the bivalent and monovalent ions fail. As from the table of the Obviously, the solubilities of the Fen differ from those of the fine sulphate by two Powers of ten. It is therefore possible through the aforementioned use of acetone, for example the To separate sulphates of divalent iron from that of trivalent iron. The same is true for Manganese too.

In addition to the advantages of the method according to the invention that have already been described, there is another very important one Added energy savings. Usually sulphate solutions have to be evaporated to such an extent that their cooling, the salt to be obtained can be crystallized and separated. One uses this normally centrifuges and washes remaining residues of the mother liquor from the centrifuged Salt down by covering it with fresh water. This is inevitable a certain amount of the salt recovered in solution again. It thus remains in the circuit to evaporate - crystallize - spin out. To evaporate the sulphate solutions one uses to the Increase the evaporation rate as much as possible and prevent incrustations on the evaporator heating surfaces Avoid using vacuum or thin-film evaporators whenever possible. The amount of energy required to evaporate of water remains the same in principle and is theoretically around 540 kcal / kg of water.

In contrast, it is only necessary in the process according to the invention to separate the acetone-water mixture by a simple distillation process and to recover the acetone in the required concentration of about 97 ⁰ I _0. However, only 131 kcal / kg is required to vaporize 1 kg of acetone. In addition, the laborious separation work for the crystallized salt from the crystal slurry obtained after evaporation and cooling is no longer necessary. As already stated in Example 1, the precipitated sulfate and the acetone-water mixture separate easily and completely from one another. It is practically only necessary to spread the still moist salt on a porous surface and to let the residues of the solution drip off. The acetone still adhering to the salt can be removed quickly and completely by passing a stream of heated air over the spread salt. All acetone vapors produced during the process according to the invention are passed in a known manner through activated carbon filters, where they can be adsorbed and subsequently recovered. The process according to the invention differs from the previously known manufacturing processes not only in the combination of a liquid-liquid extraction process with subsequent precipitation of the sulfate to be obtained with the aid of one and the same solvent, i.e. acetone, but also in a whole series of simplifications that make the Facilitate the entire way of working and by eliminating previously necessary operations avoid the possibility of renewed contamination of the salt to be extracted during the same. Reference should also be made to the considerably increased economic efficiency of the process according to the invention as a result of the possibility of using cheaper technical raw materials and the saving of expensive equipment, energy and labor costs.

Claims (1)

Claim: Process for the production of sulphates, especially those with extremely low chlorine levels, characterized in that the aqueous, optionally chloride-containing solution of the sulfate in question once or Acetone is added several times and intimately mixed with it. Considered publications:
Swiss patent specification No. 355 773. 709 747/526 1.68 © Bundesdruckerei Berlin