JPS6345458B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial field) The present invention processes zinc leaching residue generated during wet zinc smelting by combining a conventional high-temperature strong acid leaching method and a method for separating iron and zinc by sulfidation. , relates to a method for treating zinc leaching residue that effectively recovers copper, lead, cadmium and zinc and renders iron harmless. (Prior art and its problems) Various methods have been proposed and put into practice for treating zinc leaching residue. Dry methods include the Wertz method, retort humming method, electrothermal humming method, semi-blast furnace method, and electrothermal distillation method. These methods reduce and volatilize metals with high vapor pressure such as lead, zinc and cadmium contained in the residue and recover them in the form of metals or oxides. The low-quality metals become slag along with iron, so they can be reprocessed and recovered, but they have the following problems. (1) Fuel or electricity consumption is large. (2) Too much reducing agent is used. (3) Recovery of gold, silver, and copper is troublesome. (4) Batch operation method is common. On the other hand, wet methods include a sulfated roasting-diluted sulfuric acid leaching method, a dialosite method, a hematite method, and a goethite method. In the sulfation roasting method, silver is recovered by flotation of the acid leaching residue of oxidized roasted ore, and then iron sulfide concentrate is mixed and sulfated roasted to recover steel, zinc, and cadmium as soluble sulfates. Although it is eluted and recovered, there are the following problems. (1) A large amount of sulfuric acid is produced as a by-product. (2) Since iron sulfide is used as the sulfating agent, the amount of final residue is large due to the iron content. Furthermore, although copper, zinc, cadmium, etc. can be recovered using the gyroscope method, there are the following problems. (1) The Fe grade of the final residue is low and the amount of slag is large. (2) There is a risk of environmental pollution due to basic sulfate, and solidification is required. Furthermore, the hematite method allows complete recovery of valuable metals and has a small amount of final slag, making it an extremely excellent treatment method, but it has problems in that the process is complicated and equipment costs are high. (Purpose of the Invention) The present inventors have solved the problems of the above-mentioned conventional methods, and have made the waste harmless without producing sulfuric acid as a by-product, and can efficiently recover valuable metals while disposing of it as waste or landfill material. As a result of consideration to submit a possible method, we found that a high-temperature strong acid reduction leaching method and a sulfurization method were used.
The inventors have discovered that the above object can be achieved by a combination of selective separation of Zn and Fe, crystallization of iron sulfate, etc., and have arrived at the present invention. (Structure of the Invention) That is, according to the present invention, in a method for treating zinc leaching residue in which lead slag containing zinc and gold and silver is extracted and separated and recovered from the zinc leaching residue, (a) the zinc leaching residue is treated in a sulfur dioxide atmosphere.
Add 1.0 to 2.0 times more sulfuric acid by weight, treat at a solid-liquid ratio of 1:3 to 1:10, and at a liquid temperature of 80°C or higher to elute most of the zinc and iron from the zinc leaching residue. (b) Calcium carbonate is added to the zinc/iron solution obtained in the first step to adjust the pH value of the solution to between 0 and 2. At the same time, hydrogen sulfide gas is introduced to
a second step in which zinc in the iron solution is selectively crystallized as a zinc sulfide precipitate from the iron-containing solution and separated from the mother liquor; (c) a zinc electrolytic waste solution is added to the zinc sulfide precipitate obtained in the second step; is added to generate hydrogen sulfide gas, the hydrogen sulfide is recycled to the second step, the generated zinc solution containing calcium sulfate is passed through and separated into calcium sulfate and zinc solution, and the zinc solution is passed through the zinc electrolysis step. (d) adjusting the acidity of the iron-containing solution obtained in the second step to crystallize iron sulfate and separate it from the mother liquor;
A method for treating zinc leaching residue is obtained, which comprises a combination of a fourth step of recycling the separated mother liquor to the first step. The amount of sulfuric acid added in the first step is 1.0 of the zinc leaching residue.
~20 times the weight or more. If the amount of sulfuric acid is less than 1.0 times by weight, the leaching rate of Zn and Fe will be poor, and if it exceeds 2 times by weight, the amount of sulfuric acid will be too excessive and will be disadvantageous in terms of cost, so it is preferably 1.5 times by weight. The solid-liquid ratio ranges from 1:3 to 1:10. If the solid-liquid ratio is less than 1:3, the slurry concentration will be too high and stirring,
The operability of transfer etc. becomes worse and the leaching rate also decreases. In addition, when the ratio exceeds 1:10, the amount of slurry becomes too large, resulting in a large tank capacity, and therefore a large amount of heating charge, resulting in high equipment costs. The liquid temperature is 80℃ or higher. When the temperature is below 80℃
Zn, Fe leaching rate decreases, so preferably 80 ~
It is in the range of 100℃. The leaching time is preferably 4 hours or more. If the time is less than 4 hours, a sufficient leaching rate cannot be obtained. In the second step, the pH value of the zinc-iron solution is adjusted to a range of 0 to 2 in order to selectively sulfurize and precipitate only Zn, and for this purpose CaCO ₃ is added. Therefore, an excess amount of CaCO ₃ is required than in the following reaction formula. ZnSO ₄ +H ₂ S+CaCO ₃ =ZnS+CaSO ₄ +H ₂ O+CO ₂ ↑ Next, the present invention will be explained in detail with reference to a flow sheet of drawings. In the first step, the zinc leaching residue is treated by the so-called reduction leaching method, which combines the well-known high-temperature strong acid leaching method with reduction by sulfur dioxide gas, to dissolve sparingly soluble zinc ferrite and at the same time remove trivalent iron ions. is reduced to divalent ions to facilitate sulfurization in the second step. ZnS may be used as a reducing agent instead of SO ₂ gas. In this way, leachate and lead slag are obtained. The leachate or zinc solution contains zinc and 2
It is a sulfuric acid solution containing mainly valent iron ions. On the other hand, lead slag, which is a leaching residue, contains valuables such as lead, silver, and gold, so it is recovered through normal lead smelting. In the second step, using the relationship between PH and the stable region of zinc sulfide, Fe ⁺⁺ is left in solution while selecting a stable PH range for ZnS, that is, a range of 0 to 2, and reacting with H ₂ S gas. If so, ZnS and Fe ⁺⁺ can be separated. That is, in the second step, when calcium carbonate is added to the leachate and H ₂ S gas is blown into the leachate while stirring, zinc sulfide and gypsum are generated by the following reaction described above, so that the iron-containing liquid, zinc sulfide, and gypsum are Overseparate the mixture. ZnO ₄ + H ₂ S + CaCO ₃ = ZnS + CaSO ₄ + H ₂ O + CO ₂ ↑ In the third step, the zinc sulfide and gypsum mixture obtained in the second step is treated with zinc electrolytic waste solution, and H ₂ S gas is generated at the same time as zinc is dissolved. . This reaction is shown in the following equation. ZnS+H ₂ SO ₄ =ZnSO ₄ +H ₂ S The generated H ₂ S gas is used in the second sulfurization step. After separating the gypsum, the gypsum-containing zinc solution is supplied to a zinc electrolysis process to recover zinc. On the other hand, sulfuric acid is added to the iron-containing liquid from which the zinc and gypsum mixture was separated in the second step, and ferrous sulfate is crystallized using the relationship between sulfuric acid concentration and ferrous sulfate solubility. The solution from which the iron has been separated is reused as the leaching solution for the first step. In the fourth step, the ferrous sulfate crystals FeSO ₄゜7H ₂ O separated by crystallization are soluble, so they are mixed with calcium carbonate to naturally oxidize and become harmless, and are then disposed of in a landfill as artificial soil. Use as soil. The reaction is as follows. 2FeSO ₄・7H ₂ O+2CaCO ₃ +1/2O ₂ =2FeO(OH) CaSO ₄・2H ₂ O+9H ₂ O+2CO ₂ ↑ Next, the present invention will be specifically explained with reference to Examples. However, the scope of the present invention is not limited. Example 1 kg of zinc leaching residue containing 18.5% by weight of zinc, 25% by weight of iron, and 35% by weight of water was mixed with 100% by weight of sulfur dioxide gas using sulfuric acid 4 at a concentration of 250g/180%.
While blowing at a flow rate of ml/min, the reaction was carried out at a temperature of 95℃ for 6 hours, and zinc 42.3/(178g) and iron 56g/min.
A leachate 4.2 containing (235 g) was obtained. The leaching rates of zinc and iron were 96.2% and 94.0%, respectively (first step). Using leachate 4 from the first step, calcium carbonate
675 g was added to the leachate and a portion was suspended in a slurry state. Next, while blowing hydrogen sulfide gas at a flow rate of 330 ml/min, the mixture was reacted for 3 hours to obtain 1.46 kg of sulfurized precipitate having the composition shown in Table 1. In addition, Zn in Table 1 is 170g (sulfidation rate 100%) Fe
was 0.01g. (Second step).

[Table] Next, 1 kg of the sulfurized precipitate obtained in the second step was leached using solution 4 with a sulfuric acid concentration of 300 g for 30 minutes at a temperature of 106°C with the air removed.
Hydrogen sulfide gas 37.1 and zinc concentration 27.26g/
(115.5 g) and a leachate 4.09 containing iron concentration 1.63 g/(6.7 g) was obtained (third step). Fe98.15g/(98.15g) obtained in the second step
Concentrated sulfuric acid was added to the post-sulfurized solution 1 containing Zn0.92/(0.92g) to give an acid concentration of 25%, which was cooled to 10°C to crystallize FeSO ₄ 7H ₂ O, and then separated using a centrifuge. Iron sulfate is separated and the obtained iron sulfate is heptahydrate.
It was 361g. In this separated iron sulfate FeSO ₄ .7H ₂ O, the iron crystallization rate is about 70%, and the iron sulfate separated solution is
It had a concentration of Fe33.95g/ and Zn1.03g/. Further, 1.1 mol of calcium carbonate was mixed with 1 mol of the iron sulfate crystals, and the mixture was allowed to naturally oxidize in the atmosphere. After 26 hours, an elution test was conducted. As a result, the pH was 7.10, the amount of eluted iron was 0.02 mg/, and the amount of eluted calcium was 250 mg/. In addition, the iron form was oxidized to goethite (FeOOH), and the calcium was in the form of gypsum. (4th step). (Effects of the Invention) By adopting the above configuration, the present invention can achieve the following effects. (1) Sulfuric acid is not produced as a by-product, iron-containing waste is rendered harmless, and it can be used as artificial soil for landfill. (2) Do not dispose of valuable materials such as lead, gold, and silver, but treat them as recovered raw materials. (3) Can be processed with normal equipment.

[Brief explanation of the drawing]

The drawing is a flow sheet diagram of one embodiment of the present invention.

Claims (1)

[Scope of Claims] 1. A method for treating zinc leaching residue in which lead slag containing zinc and gold and silver is extracted and separated and recovered from the zinc leaching residue, comprising: (a) adding the zinc leaching residue to the zinc leaching residue in a sulfur dioxide gas atmosphere;
Add 1.0 to 2.0 times more sulfuric acid by weight, treat at a solid-liquid ratio of 1:3 to 1:10, and at a liquid temperature of 80°C or higher to elute most of the zinc and iron from the zinc leaching residue. (b) Calcium carbonate is added to the zinc/iron solution obtained in the first step to adjust the pH value of the solution to between 0 and 2. At the same time, hydrogen sulfide gas is introduced to
a second step in which zinc in the iron solution is selectively crystallized as a zinc sulfide precipitate from the iron-containing solution and separated from the mother liquor; (c) a zinc electrolytic waste solution is added to the zinc sulfide precipitate obtained in the second step; is added to generate hydrogen sulfide gas, the hydrogen sulfide is recycled to the second step, the generated zinc solution containing calcium sulfate is passed through and separated into calcium sulfate and zinc solution, and the zinc solution is passed through the zinc electrolysis step. (d) adjusting the acidity of the iron-containing solution obtained in the second step to crystallize iron sulfate and separate it from the mother liquor;
A method for treating zinc leaching residue, comprising a fourth step of recycling the separated mother liquor to the first step.