RU2365641C2 - Method of purification of sulphate solutions of non-ferrous metals from iron - Google Patents

Abstract

FIELD: metallurgy. ^ SUBSTANCE: invention relates to hydrometallurgy of non-ferrous metals, in particular to purification of sulphate solutions containing non-ferrous metals from iron. The method involves neutralisation of the acid with limestone or lime which is followed by oxidation and hydrolytic precipitations of iron by means of oxyhydrolysis in the autoclave at elevated temperatures and pressure of oxygen. At the same time the pulp obtained after neutralisation is subjected to oxyhydrolysis. This pulp contains crystals of gypsumserving as solidification centers and ensuring precipitation of iron as macrocrystalline well filtered sediment. The neutralisation is performed from the solution containing 15-20 g/l of sulfuric acid minimum till pH 0.5-2.5. The oxyhydrolysis is performed at the temperature of 160-200C and the oxygen partial pressure of 0.3-1.0 MPa (3-10 atm). ^ EFFECT: minimum amount of the filter equipment and better extraction of the non-ferrous metals with iron-containing sediment because of the iron extracted as well filtered sediment. ^ 3 cl, 1 tbl, 1 ex

Description

The invention relates to the metallurgy of non-ferrous metals, in particular to the hydrometallurgical processing of copper-zinc intermediate products, and can be used for purification of iron sulfate solutions containing non-ferrous metals (zinc, copper, etc.).

A known method of hydrolytic cleaning of solutions from iron by oxidation of iron (II) with oxygen and precipitation of iron (III) with increasing pH to 3-4 (V.Ya. Zaitsev, E.V. Margulis. Metallurgy of lead and zinc. M: Metallurgy , 1963). This method, the so-called goeth process, is widely used in hydrometallurgy. Its advantage is that cleaning is carried out at temperatures below the boiling point of the solution and atmospheric air pressure. However, this method is not applicable to solutions with a high iron content, since the resulting iron deposits are poorly filtered and capture many non-ferrous metals.

A known method of cleaning solutions from iron by precipitation in the form of jarosite, the so-called jarosite process (V.Ya. Zaitsev, E.V. Margulis. Metallurgy of lead and zinc. M: Metallurgy, 1963). The solution to be cleaned is neutralized to a pH slightly lower than the precipitation of jarosite (0.8-1) and filtered if necessary. In the resulting solution, iron (II) is oxidized with atmospheric oxygen to iron (III) in the presence of potassium, sodium or ammonium compounds. The pH (~ 1.5) required for the formation of jarosite is maintained by the addition of a neutralizing agent, such as alkali or zinc cinder, until iron is completely precipitated. Compared with the previous method, the jarosite process gives a much better filtering precipitation, however, it requires the use of expensive jarosite-forming additives (potassium, sodium, ammonium compounds). Therefore, for solutions with a high iron content and a low zinc content, this method is unprofitable. In addition, during prolonged storage of jarosite-containing sediments, they partially decompose with the formation of acidic effluents, which requires the use of special measures when dumping such sediments into the tailings dump.

The closest is the method of precipitation of iron from a solution in the form of hematite according to the patent "Method for the separation of zinc and iron from zinc and iron-containing material (options)" (RU 2117057 C1, IPC C22B 19/00, 08/10/1998). In accordance with this method, the solution is neutralized to pH ~ 1 by adding limestone or lime to obtain a gypsum precipitate, the resulting solution is neutralized to pH ~ 4.5 by adding lime or limestone to remove impurities from it before iron removal and then the resulting solution is treated under oxidizing conditions under 170-200 ° C to remove iron from it in the form of hematite.

Unlike the jarosite process, this method does not require the use of special reagents and allows to obtain iron deposits with a lower content of non-ferrous metals, environmentally safe and suitable for discharge into the tailings pond. However, in this method, iron is precipitated in the form of precipitations that are not well filtered and absorb many non-ferrous metals.

An object of the present invention is to precipitate iron from solutions containing non-ferrous metals. The technical result is the release of iron in the form of well-filtered sediments with a low content of non-ferrous metals. Obtaining such precipitation allows you to reduce the amount of filtering equipment and reduce the loss of non-ferrous metals with ferrous cake.

The problem is solved in that an unclarified solution is supplied for oxyhydrolysis, as is the case in the prototype, and a pulp containing gypsum crystals that serve as oxyhydrolysis centers of crystallization of hematite and basic sulfate and formed at the previous stage when the solution was neutralized with limestone or lime. Due to the presence of crystallization centers in the solution, iron precipitation during oxyhydrolysis occurs in the form of a relatively coarse-grained, well-filtered precipitate having low adsorption ability with respect to non-ferrous metals.

In order to precipitate iron in the form of a well-filtered precipitate, pulp having a sufficiently high concentration of crystallization centers (gypsum crystals) must be supplied to the oxyhydrolysis operation. Studies have shown that such a concentration is ensured if a solution with a sulfuric acid concentration of at least 15-20 g / l enters the preliminary neutralization stage. The operation is carried out at a temperature of 20-80 ° C. The final pH should be in the range of about 1.0-2.5. At a higher pH value, partial precipitation of iron in the form of an amorphous hydroxide precipitate is possible, which leads to an increase in the zinc content in the final glandular cake. A lower pH value reduces the completeness of iron deposition during subsequent oxyhydrolysis.

Oxyhydrolysis is carried out in the temperature range 160-200 ° C and partial oxygen pressures of 0.3-1 MPa (3-10 atm), i.e. under the same conditions as the prototype. With these parameters, the duration of the process is 20-90 minutes.

The foregoing is confirmed by the following examples.

Experiments on the implementation of the prototype and the proposed method were carried out on solutions obtained by hydrometallurgical processing of sulfide copper-zinc intermediate product, allocated during flotation ore processing of one of the Ural deposits.

Preliminary neutralization was carried out in a glass beaker with a capacity of 1 liter at a temperature of 70 ° C and mechanical stirring. Limestone with a CaO content of 47% was used as a neutralizer. Oxyhydrolysis was carried out in a 1 L titanium autoclave. The resulting pulp was filtered, the content of iron, zinc and acid was determined in the filtrate, and the content of zinc in the washed glandular cake. In the experiments on the prototype, the experimental procedure was the same except that after the stage of preliminary neutralization, the gypsum precipitate was separated by filtration, and the obtained filtrate was subjected to oxyhydrolysis. The test results are shown in the table.

It can be seen that the proposed method (op.3-6) provides for the production of glandular cakes having significantly better filterability and having a lower zinc content compared to cakes obtained by the prototype (op.1, 2). The results of op.3-7 show that the optimal temperature range of oxyhydrolysis is 200-160 ° C, with a decrease in temperature to 140 ° C, the filterability of cake decreases, and the zinc content in it increases. An increase in temperature above 200 ° C and partial pressure is impractical, since it leads to an increase in the total pressure in the autoclave and requires a high steam flow rate for heating the pulp. It is also seen that the preliminary neutralization must be completed in the range of pH 0.5-2.5. At a higher pH, the zinc content in the cake increases (op. 8); at a lower pH, the depth of iron deposition during oxyhydrolysis decreases (op. 9).

Claims (3)

1. The method of purification of sulfate solutions of non-ferrous metals from iron, including the neutralization of the acid with limestone or lime, oxidation and hydrolytic deposition of iron by oxyhydrolysis in an autoclave at elevated temperature and oxygen pressure, characterized in that the pulp obtained after neutralization and containing gypsum crystals is used for oxyhydrolysis crystallization centers and contributing to the deposition of iron in the form of a coarse crystalline well-filtered precipitate. 2. The method according to claim 1, characterized in that the neutralization is carried out from a solution with a sulfuric acid content of at least 15-20 g / l to a pH of 0.5-2.5. 3. The method according to claim 1, characterized in that oxyhydrolysis is carried out at a temperature of 160-200 ° C and a partial oxygen pressure of 0.3-1.0 MPa (3-10 atm).