SU712450A1 - Method of zinc oxide hydrometallurgical production - Google Patents

Description

METHOD OF HYDROMETALLURGICAL

(54) ZINC OXIDE

OBTAINING

The invention relates to the field of non-ferrous metallurgy, in particular to the field of processing zinc-containing intermediate products to produce pure zinc oxide.

The closest to the proposed method is a hydrometallurgical production of zinc oxide, which includes leaching zinc-containing materials with caustic soda, cleaning the solution and decomposing it with zinc oxide, separating zinc oxide and drying it 1.

According to a known method, the zinc-containing raw material is leached with a strong solution of sodium hydroxide, the resulting pulp is diluted with water, the zinc solution is purified from sodium silicate with aluminum hydroxide, the zinc solution is decomposed with zinc oxide, the mother solution is evaporated and the zinc oxide is dried at 150-200 ° C. In this method, the solvent is recyclable and is used repeatedly, without the need for regeneration.

The disadvantage of this method is the low extraction of zinc oxide in the final product, which is 84-88% instead of 96-97% theoretically possible; This is because in order to achieve optimal

indicators of the process of decomposition of the solution (the degree of decomposition of 50-52%) is necessary pre-deep desiliconization of zincate solution. However, during deep desilicration, the solution begins to decompose spontaneously, which leads to a decrease in zinc oxide recovery. In addition, zinc oxide is contaminated with aluminum hydroxide, since the process

Desiliconization is carried out by bonding silica to poorly soluble compounds of sodium hydroaluminosilicate. In this case, it is necessary to add an excess amount of aluminum hydroxide with respect to silicon dioxide. As a result, a part of the dissolved aluminum after the drying of the silicon remains in the solution, and the decomposition of the aluminum precipitates due to zinc oxide contamination.

The aim of the invention is to increase the recovery and quality of zinc oxide.

This is achieved by cleaning the solution in two stages, with the decomposition of the zincate solution in the first stage.

carried out by calcium oxide.

The essence of the invention is as follows.

The zinc-containing raw material is leached with a strong alkaline solution containing 240-300 g / l of sodium oxide. The resulting slurry is diluted with water and the solution is separated from the leached residue. Silicon dioxide, peredshedshchy in solution in the process of leaching of raw materials, stabilizes it, and the solution does not decompose even in the presence of large amounts of zinc oxide seed. The solution is subjected to a decomposition-desiliconization operation using calcium oxide additive. The addition of calcium oxide contributes to the simultaneous deep decomposition and desiliconization of the supersaturated zincate solution, converting silica into a poorly soluble compound. The degree of decomposition - 62-55%. The precipitate is separated from the solution and leached again with a strong alkaline solution. In this case, only zinc oxide passes into the solution, and the bulk of the silica remains in the sediment.

The purified solution is diluted, separated from the precipitate by filtration, and subjected to repeated decomposition with a zinc oxide seed. Such a solution decomposes quickly and deeply enough, by 50-53%. Then the zinc oxide is separated from the solution and it is solid.

The method has been tested in laboratory conditions.

To obtain zinc oxide, a wet gas cleaning sludge from blast furnaces of the following composition is used,%: zinc oxide 13.81; silica 8.87; alumina 3.84; calcium oxide 6.06; iron 20.95; carbon 23.00.

Leaching of this sludge is carried out with a circulating alkaline zincate solution containing 250 g / l of sodium oxide, 60 g / l of zinc oxide at a temperature of 96 ° C for 45 minutes at a density of slurry G: T 3.5. After leaching, the pulp is diluted with water to a concentration of 110 g / l sodium oxide and the solution is separated from the slurry by filtration. The resulting solution contains 46 g / l of zinc oxide and 0.72 g / l of silica. Calcium oxide is added to it based on the calculation of the concentration of CaO active 25 g / l and stirred for 1 hour at 70 ° C. The silica content in the solution is reduced to 0.12 g / l and the precipitate is released from a solution of 52% zinc oxide.

The precipitate, consisting of zinc oxide, calcium oxide and silicon dioxide, is separated from the solution by filtration and sent to re-leaching with a circulating alkaline solution containing 250 g / l Azo, 60 g / l zinc oxide.

Leaching is carried out for 0.5 h at 70 ° C and pulp density G: T 12. After dilution and filtration, the solution contains 106 g / l of sodium oxide, 52 g / l of zinc oxide and 0.16 g / l of silica. This solution is decomposed with zinc oxide seed. The temperature is 90 ° C, the duration is 4 hours, the seed ratio is 1. The decomposition degree of the solution is 52.7%. Next, zinc oxide is separated from the mother liquor, washed and dried.

The results of comparative tests of the proposed and known methods are given in the table.

Claims (1)

Claim Obtaining a hydrometallurgical method ⁴⁵ Nia comprising leaching zinc-containing materials with sodium hydroxide, zinc oxide, and decomposition of the solution purification of zinc oxide it, separating zinc oxide and drying it, characterized in that, to improve the quality and recovery of zinc oxide, lead cleaning solution into two stage, with the first stage, the decomposition of the zincate solution is carried out with calcium oxide.