A method for producing cadmium yellow from cadmium fume

Abstract

The present application relates to a kind of method for producing cadmium yellow of cadmium fume, belong to the field of cadmium recovery.The technical scheme of the present application includes four main steps of leaching, neutralization and precipitation, acid dissolution and impurity removal and production of cadmium yellow.In the neutralization, by adding cadmium fume leaching solution to the reverse neutralization operation of lye, the amount of precipitate into the precipitate of cadmium hydroxide chloride is effectively reduced;After the acid dissolution of cadmium hydroxide, the acid solution is oxidized to improve the valence of impurities such as arsenic and iron, and then alkaline material is added to precipitate high-valence impurities, remove impurities such as arsenic and iron, and purify cadmium solution.By adding sulfidation agent to the filtrate after impurity removal, cadmium yellow product can be prepared, and the cadmium yellow product meets the procurement standards of enamel, glass, ceramic, plastic and other industries.

Description

Technical Field

[0001] This invention belongs to the field of cadmium recovery, and in particular relates to the recovery and utilization of cadmium from cadmium flue dust. Background Technology

[0002] During lead smelting, over 90% of the cadmium in the furnace feed material is enriched in the flue dust. Other impurities such as fluorine and chlorine also accumulate in the flue dust. When cadmium enrichment in the flue dust reaches 15% or higher, the flue dust rate increases, increasing the load on the dust collection system, affecting the efficiency of electrostatic precipitators, and reducing the effective production load of the crude lead system, thus impacting economic benefits. Open-circuit treatment of lead flue dust can reduce the impact of cadmium enrichment on the smelting process. The cadmium in the open-circuit flue dust usually needs to be recovered.

[0003] Cadmium yellow (CdS) is usually prepared by adding a sulfiding agent to a cadmium-containing solution. However, because cadmium-containing dust contains impurities such as Cl, Fe, As, and Tl that are difficult to remove, the cadmium-containing solution prepared by leaching and removing impurities from the cadmium dust still contains impurities such as Cl, Fe, As, and Tl. During the preparation of cadmium yellow, chloride ions and impurity ions such as Fe, As, and Tl will affect the quality of cadmium yellow, resulting in substandard cadmium yellow products. Summary of the Invention

[0004] In order to overcome the problems existing in the background technology, the present invention provides a method for producing cadmium yellow from cadmium dust. By neutralizing and precipitating the cadmium dust leachate, acid dissolving and removing impurities, the impurities such as Cl, Fe, As, and Tl in the cadmium dust leachate are effectively removed, and qualified cadmium yellow is finally prepared.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: (1) The cadmium in the cadmium fume is leached out by water immersion or acid immersion, and after liquid-solid separation, filtrate 1 and filter residue 1 are obtained; (2) Reverse neutralization is used to precipitate cadmium in solution 1 to prevent the formation of basic cadmium chloride. After liquid-solid separation, filtrate 2 and cadmium hydroxide are obtained. (3) Add acidic solution to dissolve cadmium hydroxide; the acid-dissolved slurry is purified by oxidation and neutralization, and after liquid-solid separation, filtrate 3 and filter residue 2 are obtained; (4) To produce cadmium yellow, add a sulfiding agent to the filtrate 3 to produce cadmium yellow product.

[0006] Furthermore, the reverse neutralization involves adding the filtrate 1 from step (1) to the neutralizing agent.

[0007] Furthermore, the neutralizing agent is a sodium hydroxide solution or a sodium carbonate solution.

[0008] Furthermore, the neutralization precipitation conditions were room temperature, time 0.5-1.0 h, and endpoint pH value 10.5-11.0.

[0009] Furthermore, the acid dissolution technique conditions are as follows: temperature 50-70℃, time 1.0-2.0h, and final pH value 2.0-3.0.

[0010] Furthermore, the acidic solution used in step (3) is dilute sulfuric acid.

[0011] Furthermore, the oxidation and neutralization process described in step (3) involves first adding an oxidant to oxidize the low-valence ions that are harmful to cadmium yellow production into high-valence ions, and then adding alkaline materials to neutralize the high-valence ions before adding them into the slag.

[0012] Furthermore, the oxidation and neutralization purification techniques in step (3) are as follows: 0.4-0.8 g / L of oxidant and 0.4-0.8 g / L of hydrated lime powder are added sequentially. The oxidation and neutralization purification temperature is 70-85℃, and the time is 0.5-1.0 h.

[0013] Furthermore, the oxidant mentioned in step (3) is potassium permanganate.

[0014] Furthermore, the sulfiding agent in step (4) is a purified sodium sulfide aqueous solution.

[0015] Furthermore, the filter residue 1 and filter residue 2 produced in the leaching step are returned to lead smelting.

[0016] Furthermore, the filtrate 2 from step (2) is returned to the leaching step (1). Beneficial effects

[0017] This invention reduces the chlorine content (as Cl) in cadmium hydroxide from 0.8-1.2% to 0.04-0.06% by employing reverse neutralization, thereby avoiding the impact of Cl on the quality of cadmium yellow products. Through oxidation and neutralization after acid dissolution, impurities such as Fe, As, and Tl in the cadmium solution are removed, thus avoiding the impact of Fe, As, and Tl on the quality of cadmium yellow products. The prepared cadmium yellow products meet the procurement standards of the enamel, glass, ceramics, and plastics industries. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are all within the scope of protection of this invention.

[0020] The method for producing cadmium yellow from cadmium dust includes the following steps: (1) Leaching Cadmium in the cadmium-containing dust was leached using conventional methods, namely water leaching or acid leaching. After solid-liquid separation of the leached slurry, filtrate 1 and filter residue 1 were obtained. Filter residue 1 was returned to lead smelting, and filtrate 1 entered step (2).

[0021] (2) Reverse neutralization precipitation The reverse neutralization involves adding the filtrate 1 from step (1) to the neutralizing agent, with the slurry pH value decreasing from high to low; the conventional neutralization involves adding the neutralizing agent to the filtrate 1, with the slurry pH value increasing from low to high.

[0022] Cl-containing filtrate - When neutralizing cadmium hydroxide using conventional methods with a neutralizing agent, the pH value increases gradually from low to high. Within the pH range of 7.2-10.5, basic cadmium chloride (CdOHCl) precipitate will form and enter the cadmium hydroxide, resulting in cadmium hydroxide containing Cl. - High chlorine content (0.8-1.2%) will affect the production of cadmium yellow. This invention employs reverse neutralization, with the final pH controlled at 10.5-11.0. Because the pH of the neutralized slurry decreases from high to low, it avoids the formation range of basic cadmium chloride, thus reducing the chloride content of cadmium hydroxide. - Decreased to Cl 0.04-0.06%.

[0023] Reverse neutralization precipitation conditions: temperature at room temperature, time 0.5-1.0 h, final pH value 10.5-11.0. The neutralized slurry is separated into liquid and solid, yielding filtrate 2 and filter residue. Filtrate 2 is returned to step (1) for leaching cadmium, and the filter residue is cadmium hydroxide, which is then introduced into step (3).

[0024] The neutralizing agent is a sodium hydroxide or sodium carbonate solution.

[0025] (3) Acid dissolution and impurity removal Add an acidic solution to dissolve the cadmium hydroxide from step (3). The acidic solution is dilute sulfuric acid. The acid dissolution conditions are: temperature 50-70℃, time 1.0-2.0h, and final pH value 2.0-3.0.

[0026] In the filtrate 1 obtained in step (1), in addition to F and Cl, there are also harmful impurities such as Fe, Tl and As that affect the quality of cadmium yellow. During the neutralization and precipitation in step (2), harmful impurities such as Fe, Tl and As will enter cadmium hydroxide. During acid dissolution, the above-mentioned harmful impurities will dissolve along with cadmium and must be removed in order not to affect the quality of cadmium yellow products.

[0027] By adding an oxidizing agent, the impurities that dissolve together with the acid during dissolution are oxidized into high-valence ions. Then, quicklime powder is added to hydrolyze the impurity ions and precipitate them into the slag.

[0028] Impurity removal technical conditions: Add 0.4-0.8 g / L of oxidant and 0.4-0.8 g / L of quicklime powder respectively; the impurity removal temperature is 70-85℃; the time is 0.5-1.0 h. The slurry is separated into liquid and solid, yielding filter residue 2 and filtrate 3. Filter residue 2 is sent to lead smelting, and filtrate 3 enters step (4). The oxidant used is potassium permanganate.

[0029] After acid dissolution, the slurry does not require liquid-solid separation and can be directly purified.

[0030] (4) Cadmium Yellow Production The sulfiding agent used is sodium sulfide. Before use, sodium sulfide is purified to prevent impurities in the sodium sulfide from being introduced into the cadmium yellow product.

[0031] The purified sodium sulfide was added to filtrate 3. After liquid-solid separation, filter residue and filtrate 4 were obtained. The filter residue was dried and calcined to obtain cadmium yellow product, and filtrate 4 was sent to wastewater treatment.

[0032] To illustrate the present invention more clearly, the following embodiments will be described in detail. Example 1

[0033] The cadmium-containing dust composition (%wt) used in this embodiment is as follows: Pb 48.27, Cd 10.35, As 0.56, F 0.22, Cl 0.82, Tl 0.21.

[0034] Cadmium-containing fumes were added to waste electrolyte for acidic leaching. After liquid-solid separation, filtrate 1 and filter residue 1 were obtained. The composition of filtrate 1 (Cd g / L, other components mg / L) was: Cd 25.6g, F 300, Cl 200, Tl 360, As 236. Filter residue 1 was returned to lead smelting.

[0035] Filtrate 1 was neutralized in sodium hydroxide solution under the following conditions: room temperature, 0.5 h, and final pH of 10.5. The neutralized slurry was then subjected to liquid-solid separation to obtain filtrate 2 and filter residue. Filtrate 2 was returned to the acid leaching process for cadmium-containing flue dust, and the filter residue was cadmium hydroxide. The composition of cadmium hydroxide (%) was: Cd 74.26, F 0.032, Cl 0.043.

[0036] Cadmium hydroxide was dissolved using dilute sulfuric acid under the following conditions: temperature 50℃, time 1.0 h, final pH 2.0. The solution composition after acid dissolution (Cd g / L, other components mg / L) was: Cd 160.85, F 68, Cl 96, Tl 58, Fe 190. After acid dissolution, impurities were removed directly by oxidation without liquid-solid separation. The impurity removal conditions were: potassium permanganate 0.8 g / L and quicklime powder 0.4 g / L were added sequentially. Oxidation was performed at 70℃ for 1.0 h, followed by liquid-solid separation to obtain filter residue 2 and filtrate 3. Filter residue 2 was sent to lead smelting. The composition of filtrate 3 (Cd g / L, other components mg / L) was: Cd 160.06, F 8.93, Cl 194, Tl 5.31, Fe 1.32. The quality of filtrate 3 met the requirements for cadmium yellow production.

[0037] Sodium sulfide is added to filtrate 3 to generate CdS. Before use, sodium sulfide is purified and then added to filtrate 3. After liquid-solid separation, the filter residue is dried and calcined to obtain cadmium yellow product. The quality of cadmium yellow product meets the procurement standards of industries such as enamel, glass, ceramics and plastics. Filtrate 4 is sent to wastewater treatment. Example 2

[0038] The cadmium-containing dust composition (%wt) used in this embodiment is: Pb 33.27, Cd 30.35, As 1.86, F 0.42, Cl 1.08, Tl 0.33.

[0039] The cadmium-containing flue dust was leached in water, and after liquid-solid separation, filtrate 1 and filter residue 1 were obtained. The composition of filtrate 1 (Cd g / L, other components mg / L): Cd 72.30, F 450, Cl 2500, Tl 340. Filter residue 1 was returned to lead smelting.

[0040] Filtrate 1 was added to a sodium carbonate solution under the following conditions: room temperature, 1.0 h, and final pH of 11.0. The neutralized slurry was then subjected to liquid-solid separation to obtain filtrate 2 and filter residue. Filtrate 2 was returned to the cadmium-containing flue gas for water leaching, and the filter residue was cadmium hydroxide. The composition of cadmium hydroxide (%) was: Cd 75.06, F 0.048, Cl 0.052.

[0041] Cadmium hydroxide was dissolved using dilute sulfuric acid. The acid dissolution conditions were: temperature 70℃, time 2.0 h, final pH 3.0. The composition of the solution after acid dissolution (Cd g / L, other components mg / L) was: Cd 170.45, F 90.26, Cl 120.01, Tl 60.33, Fe 170. After acid dissolution, impurities were removed directly by oxidation without liquid-solid separation. The impurity removal conditions were: potassium permanganate 0.4 g / L and quicklime powder 0.8 g / L were added sequentially at 85℃ for 0.5 h. The slurry was then separated into liquid and solid components, yielding filter residue 2 and filtrate 3. Filter residue 2 was sent to lead smelting. The composition of filtrate 3 (Cd g / L, other components mg / L) was: Cd 1670.85, F 10.93, Cl 100.30, Tl 5.21, Fe 1.36. The quality of filtrate 3 met the requirements for cadmium yellow production.

[0042] Sodium sulfide is added to filtrate 3 to generate CdS. Before use, the sodium sulfide is purified and then added to filtrate 3. After liquid-solid separation, filtrate 4 and filter residue are obtained. The filter residue is dried and calcined to obtain cadmium yellow product. The product quality meets the procurement standards of the enamel, glass, ceramics, and plastics industries. Filtrate 4 is sent to wastewater treatment.

[0043] Note: Unless otherwise specified, all percentage contents mentioned in this invention are mass percentage contents.

[0044] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A method for producing cadmium yellow from cadmium dust, characterized in that, Includes the following steps: (1) The cadmium in the cadmium fume is leached out by water immersion or acid immersion, and after liquid-solid separation, filtrate 1 and filter residue 1 are obtained; (2) Reverse neutralization is used to precipitate cadmium in solution 1 to prevent the formation of basic cadmium chloride. After liquid-solid separation, filtrate 2 and cadmium hydroxide are obtained. The reverse neutralization is to add filtrate 1 from step (1) to the neutralizing agent. The pH value at the end of the reverse neutralization is 10.5-11.

0. (3) Add acidic solution to dissolve cadmium hydroxide; oxidize and neutralize the acid-dissolved slurry to remove impurities, and after liquid-solid separation, obtain filtrate 3 and filter residue 2; (4) Add a sulfiding agent to the filtrate 3 to produce cadmium yellow.

2. The method according to claim 1, characterized in that, The neutralizing agent is a sodium hydroxide solution or a sodium carbonate solution.

3. The method according to any one of claims 1-2, characterized in that, The neutralization and precipitation conditions were room temperature and 0.5-1.0 h.

4. The method according to claim 1, characterized in that, The acid dissolution conditions for step (3) are: temperature 50-70℃, time 1.0-2.0h, and final pH value 2.0-3.

0.

5. The method according to claim 1, characterized in that, The acidic solution used in step (3) is dilute sulfuric acid.

6. The method according to claim 1, characterized in that, The oxidation and neutralization process described in step (3) involves first adding an oxidant to oxidize the low-valence ions that are harmful to cadmium yellow production into high-valence ions, and then adding alkaline materials to neutralize the high-valence ions before adding them into the slag.

7. The method according to claim 1 or 6, characterized in that, Oxidation and neutralization impurity removal technical conditions: Add 0.4-0.8 g / L of oxidant and 0.4-0.8 g / L of quicklime powder in sequence; oxidation and neutralization temperature: 70-85℃; time: 0.5-1.0 h.

8. The method according to claim 7, characterized in that, The oxidant mentioned in step (3) is potassium permanganate; the sulfiding agent in step (4) is purified sodium sulfide aqueous solution.

9. The method according to claim 1, characterized in that, The filter residue 1 and filter residue 2 produced in the leaching step are returned to lead smelting.

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