CN116770105A - Method for separating and enriching thallium in zinc oxide soot - Google Patents

Abstract

The invention belongs to the field of hydrometallurgical zinc oxide soot recovery and discloses a method for separating and enriching thallium in zinc oxide soot. It includes the following steps: (1) Grind and mix zinc oxide soot and sodium hydroxide or potassium hydroxide in a mass ratio of 3 to 5:1, then roast them at a temperature of 200 to 350°C to obtain a roasted product; (2) ) Slurry the roasted product obtained in step (1) with water at a solid-liquid ratio of 1:3~1:6 and then immerse it in water at a temperature of 60~80°C and an end-point pH value of 11~12. Filter to obtain a water immersion liquid. and water leaching residue; (3) perform low-acid leaching of the water leaching residue obtained in step (2) at a temperature of 70~90°C and an end-point pH value of 3.5~4.5. Filter to obtain an acid leaching solution and an acid leaching solution enriched with thallium. Scum. The invention has a simple process and low cost, the thallium is not dispersed, and the separation and enrichment effects are good. It not only realizes the comprehensive utilization of resources, but also avoids the internal circulation of thallium and reduces the thallium removal pressure of the zinc system.

Description

A method for separating and enriching thallium in zinc oxide soot

Technical field

The invention belongs to the field of hydrometallurgical zinc oxide soot recovery field, and specifically relates to a method for separating and enriching thallium in zinc oxide soot.

Background technique

Zinc oxide soot from hydrometallurgical zinc smelting is mostly produced during the fluorine and chlorine removal process in multi-hearth furnaces. Some substances with lower volatilization temperatures are concentrated in zinc oxide soot. The main elements it contains are zinc, lead, cadmium, thallium, and fluorine. , chlorine, etc. The difficulty in recycling zinc oxide soot lies in the maximum separation of valuable metals such as fluorine, chlorine and zinc, as well as the separation and recovery of the highly toxic element thallium. Due to the complexity and high cost of recycling zinc oxide soot, most of the zinc oxide soot currently produced by zinc plants is exported or stored, and has not yet been reused, let alone the disposal of thallium. Taking a hydrometallurgical zinc smelting plant with an annual output of 300,000 tons as an example, the annual output of zinc oxide soot is 800 to 900 tons. There is great pressure on safety and environmental protection for export or storage, and there is a risk of leakage. As national environmental protection policies become increasingly tightened, the requirements for the disposal of thallium-containing zinc oxide soot will become more stringent.

At present, the conventional treatment process of zinc oxide soot is to first separate fluorine and chlorine by alkali washing, then acid leaching the alkali washing residue to recover zinc, cadmium and other metals, and use sulfide precipitation to remove thallium in the alkali washing solution. Thallium is enriched in Among sulfide slags, relatively stable sulfide slags are generally chosen for storage. However, the overall removal rate of fluorine and chlorine during the alkali washing process is low, only 50~60%. The alkali washing residue cannot meet the requirements for secondary utilization, and the recovery rate of thallium during the alkali washing process is limited. Part of the thallium will be dispersed in the alkali washing residue. In the process, as the alkali washing residue is leached and circulated in the wet zinc smelting system, it puts pressure on the stable operation of the system. At the same time, corresponding thallium removal processes must be assisted to reduce the thallium content of the zinc sulfate solution and increase operating costs.

Contents of the invention

In view of the above-mentioned problems existing in the prior art, the purpose of the present invention is to provide a method for separating and enriching thallium in zinc oxide soot. The method has a simple process and low cost, the thallium is not dispersed, and the separation and enrichment effect is good. .

In order to achieve the above objects, the technical solutions adopted by the present invention are:

A method for separating and enriching thallium in zinc oxide soot, including the following steps:

(1) Grind and mix zinc oxide soot and sodium hydroxide or potassium hydroxide in a mass ratio of 3 to 5:1, then roast them at a temperature of 200 to 350°C to obtain a roasted product;

(2) Slurry the roasted product obtained in step (1) with water at a solid-to-liquid ratio of 1:3~1:6 and then soak in water at a temperature of 60~80°C and an end-point pH of 11~12. Filter to obtain water. Liquor and water leaching residue;

(3) Perform low-acid leaching of the water leaching residue obtained in step (2) at a temperature of 70 to 90°C and an end-point pH value of 3.5 to 4.5. Filter to obtain an acid leaching liquid and an acid leaching residue enriched in thallium.

The present invention creatively uses sodium alkali roasting to solidify the thallium in zinc oxide soot so that it is not dispersed during the separation and enrichment process.

The reaction principle involved is that the physical phases of thallium in zinc oxide soot are thallium oxide and thallium chloride. The curves of the vapor pressure of thallium oxide and thallium chloride changing with temperature are shown in Figure 1.

When the temperature is below 350°C, the two thallium compounds have very little volatility and remain in the burned product. The following chemical reactions will occur when the sodium alkali roasting of the present invention is used:

TlCl+3NaOH=TlOH+NaCl (1)

2TlOH=Tl ₂ O+H ₂ O (2)

Tl ₂ O+O ₂ =Tl ₂ O ₃ (3)

When the present invention is water immersed, the pH value is controlled at 11 to 12. Thallium (thallium trioxide), zinc, lead, cadmium, etc. will not be leached, and fluorine and chlorine will be leached into the solution to the maximum extent, achieving the first level of thallium. Step separation and enrichment; during acid leaching, the pH value is controlled at 3.5~4.5. Thallium is hydrolyzed in the form of thallium hydroxide and coexists with lead sulfate in the acid leaching residue. Metals such as zinc and cadmium are leached into the solution, achieving thallium further separation and enrichment.

Preferably, in step (1), the temperature rise rate of roasting is 5~10°C/min; the heat preservation time is 60~120 min; and the heat preservation is completed and it is naturally cooled to room temperature.

Preferably, in step (2), the sintered blocks in the roasted product are crushed and ground before slurrying; the particle size of the roasted product after crushing and grinding is -200 mesh accounting for ≥80%.

Preferably, in step (2), the water soaking time is 1 to 3 hours.

Preferably, in step (2), the water immersion liquid is evaporated and crystallized to recover sodium chloride/potassium and sodium/potassium fluoride.

Preferably, in step (3), the water leaching residue is mixed with sulfuric acid or electrolytic waste liquid to perform low-acid leaching.

Preferably, in step (3), the solid-liquid ratio of low-acid leaching is 1:3~1:5; the starting acid is 60~80g/l.

Preferably, in step (3), the low acid leaching time is 1 to 3 hours.

Preferably, in step (3), the acid leaching liquid is sent to the wet zinc smelting system.

Compared with the prior art, the beneficial effects of the present invention are:

(1) The present invention uses low-temperature sodium-alkali roasting method to fix thallium in zinc oxide soot, so that it can form relatively stable thallium trioxide that is not easily leached by alkali, thereby achieving the goal of preventing thallium from being leached by alkali during the process of water-elution of fluorine and chlorine. dispersion.

(2) Through low-temperature roasting, the present invention increases the activity of fluorine and chlorine, and improves their removal rate during the water washing process. It can make the water washing residue contain 0.013% fluorine and 0.008% chlorine, and the fluorine removal rate is greater than 95 %, and the chlorine removal rate is greater than 99%, meeting the requirements for secondary utilization.

(3) The present invention uses low-temperature sodium-alkali roasting, water leaching, and low-acid leaching to remove fluorine, chlorine, zinc, and cadmium respectively, enriching thallium, greatly reducing the amount of thallium-containing materials, and facilitating storage and transshipment, as well as the next step of recycling and disposal of thallium.

(4) The process of the present invention is simple, low in cost, thallium is not dispersed, and its separation and enrichment effects are good. It not only achieves comprehensive utilization of resources, but also avoids the internal circulation of thallium, and reduces the thallium removal pressure of the zinc system.

Description of drawings

The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention. In the attached picture:

Figure 1 is a graph showing the changes in vapor pressure of thallium oxide and thallium chloride with temperature;

Figure 2 is a process flow diagram of the present invention.

Detailed ways

In order to facilitate understanding of the present invention, the present invention will be described more comprehensively and in detail below with reference to the accompanying drawings and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.

Unless otherwise defined, all technical terms used below have the same meanings as commonly understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of the present invention.

Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased in the market or prepared by existing methods.

Example 1

This embodiment discloses a method for separating and enriching thallium in zinc oxide soot, as shown in Figure 2, including the following steps:

(1) Sodium-alkali roasting: Grind and mix zinc oxide soot and sodium hydroxide in a mass ratio of 3:1, spread the mixture flat in a crucible, and roast at 200°C for 120 minutes to obtain a roasted product;

(2) Water immersion: Use a mortar to crush and grind the agglomerates in the roasted product. The crushed roasted product and water are slurried at a solid-to-liquid ratio of 1:3 and then immersed in water. The temperature is 80°C, the time is 3 hours, and the end point is pH=11, filter, and evaporate and crystallize the water immersion liquid to recover sodium chloride and sodium fluoride respectively. The calculated fluorine removal rate is 95.05%, and the chlorine removal rate is 99.14%;

(3) Low-acid leaching: Mix the water leaching residue with dilute sulfuric acid, control the initial acidity to 65g/L, and the liquid-to-solid ratio of 3:1 to perform low-acid leaching. The temperature is 70°C, the time is 3h, the end point pH is 4.5, and filtered. Valuable metals such as zinc enter the acid leaching solution. The calculated leaching rate of zinc is 98.52%, and thallium is enriched in the acid leaching residue.

Example 2

This embodiment discloses a method for separating and enriching thallium in zinc oxide soot, as shown in Figure 2, including the following steps:

(1) Sodium-alkali roasting: Grind and mix zinc oxide soot and potassium hydroxide in a mass ratio of 5:1, spread the mixture flat in a crucible, and roast at 300°C for 90 minutes to obtain a roasted product;

(2) Water immersion: Use a mortar to crush and grind the agglomerates in the roasted product. The crushed roasted product and water are slurried at a solid-to-liquid ratio of 1:4 and then immersed in water. The temperature is 75°C, the time is 2 hours, and the end point is pH=12, filter, evaporate and crystallize the water immersion liquid to recover sodium chloride and sodium fluoride respectively. The calculated fluorine removal rate is 95.89%, and the chlorine removal rate is 99.51%;

(3) Low-acid leaching: Mix the water leaching residue with dilute sulfuric acid, control the initial acidity to 70g/L, and the liquid-to-solid ratio of 4:1 to perform low-acid leaching. The temperature is 75°C, the time is 3h, the end point pH is 4.0, and filtered. Valuable metals such as zinc enter the acid leaching solution. The calculated leaching rate of zinc is 98.73%. Thallium is enriched in the acid leaching residue.

Example 3

This embodiment discloses a method for separating and enriching thallium in zinc oxide soot, as shown in Figure 2, including the following steps:

(1) Sodium-alkali roasting: Grind and mix zinc oxide soot and sodium hydroxide in a mass ratio of 4:1, spread the mixture flat in a crucible, and roast at 350°C for 70 minutes to obtain a roasted product;

(2) Water immersion: Use a mortar to crush and grind the agglomerates in the roasted product. The crushed roasted product and water are slurried at a solid-to-liquid ratio of 1:5 and then immersed in water. The temperature is 70°C, the time is 3 hours, and the end point is pH=12, filter, and evaporate and crystallize the water immersion liquid to recover sodium chloride and sodium fluoride respectively. The calculated fluorine removal rate is 95.37%, and the chlorine removal rate is 99.2%;

(3) Low-acid leaching: Mix the water leaching residue with the electrolytic waste liquid, control the initial acidity to 80g/L, and the liquid-to-solid ratio of 5:1 to perform low-acid leaching. The temperature is 90°C, the time is 3h, the end point pH is 3.5, and filtered , valuable metals such as zinc enter the acid leaching solution, the leaching rate of zinc is calculated to be 98.90%, and thallium is enriched in the acid leaching residue.

Comparative example 1

Compared with Example 1, in this comparative example, in step (1), the sodium alkali roasting temperature is 400°C, and other method steps are the same.

Comparative example 2

Compared with Example 2, in this comparative example, in step (2), the water immersion temperature is 40°C, and other method steps are the same.

Comparative example 3

Compared with Example 3, in this comparative example, in step (3), the end-point pH of the acid leaching is 2.5, and other method steps are the same.

The samples obtained in the above Examples 1-3 and Comparative Examples 1-3 were tested for the components of fluorine, chlorine, zinc, and thallium to calculate the removal rate of fluorine and chlorine, the leaching rate of zinc, and the retention rate of thallium. The results See Table 1.

Table 1

name Fluoride removal rate (%) Chlorine removal rate (%) Zinc leaching rate (%) Thallium retention rate (%) Example 1 95.05 99.14 98.52 99.58 Example 2 95.89 99.51 98.73 99.41 Example 3 95.37 99.2 98.90 99.35 Comparative example 1 95.71 99.32 98.46 95.29 Comparative example 2 90.15 94.82 98.57 97.64 Comparative example 3 95.33 99.17 98.65 82.29

As can be seen from the above table, the method adopted in the embodiment of the present invention can separate thallium from fluorine, chlorine, and zinc, and the thallium is enriched in the acid leaching residue, and all technical indicators are significantly better than those in the comparative example.

The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of the present invention.

Claims (9)

1. A method for separating and enriching thallium in zinc oxide soot, which is characterized by comprising the following steps:

(1) Zinc oxide ash and sodium hydroxide or potassium hydroxide are mixed according to the mass ratio of 3-5: 1 grinding and mixing uniformly, and roasting at 200-350 ℃ to obtain a roasting product;

(2) Mixing the roasting product obtained in the step (1) with water according to a solid-to-liquid ratio of 1: 3-1: 6, pulping, then leaching with water at 60-80 ℃ and an end-point pH value of 11-12, and filtering to obtain leaching liquid and leaching residues;

(3) And (3) leaching the water leaching slag obtained in the step (2) with low acid at 70-90 ℃ and an end point pH value of 3.5-4.5, and filtering to obtain acid leaching liquid and thallium-enriched acid leaching slag.

2. The method of claim 1, wherein in the step (1), the temperature rising rate of the roasting is 5-10 ℃/min; the heat preservation time is 60-120 min; and naturally cooling to room temperature after heat preservation.

3. The method of claim 1, wherein in step (2), the sintered cake in the calcined product is crushed and ground prior to pulping; the granularity of the crushed and ground roasting product is-200 meshes and the proportion is more than or equal to 80 percent.

4. The method according to claim 1 or 2, wherein in step (2), the water immersion time is 1 to 3 hours.

5. The method of claim 1, wherein in step (2), the aqueous solution is evaporated and crystallized to recover sodium chloride/potassium and sodium fluoride/potassium.

6. The method of claim 1, wherein in step (3), the water leaching residue is mixed with sulfuric acid or an electrolysis waste liquid for low-acid leaching.

7. The method of claim 1 or 6, wherein in step (3), the solid to liquid ratio of the low acid leach is 1: 3-1: 5, a step of; the content of the starting acid is 60-80 g/l.

8. The method of claim 1, wherein in step (3), the low acid leaching time is 1 to 3 hours.

9. The method of claim 1, wherein in step (3), the pickle liquor is sent to a zinc hydrometallurgy system.