Method for deep replacement of cadmium in low-cadmium solution by utilizing dielectric property difference reinforced zinc powder

Abstract

The invention discloses a method for deep replacement of cadmium in a low-cadmium solution by utilizing dielectric property difference reinforced zinc powder, and belongs to the technical field of hydrometallurgy. Heating the cadmium-containing solution to 60-70 DEG C, wherein the content of cadmium ions in the solution is less than or equal to 1200 mg / l; zinc fine powder is added according to 0.8-1.0 time of the theoretical addition amount, the proportion of particles with the particle size smaller than 75 microns is larger than 80%, and the content of Zn is larger than 95%. The reaction system is subjected to ultrasonic strengthening while being fully stirred, the ultrasonic power is 200 w, the ultrasonic frequency is 15-25 kHz, the ultrasonic intensity is 20-30%, and the ultrasonic treatment time is 20-25 min. And carrying out solid-liquid separation on the replaced solution, and returning the filter residue to a sponge cadmium acid dissolution section, wherein the content of cadmium ions in the filtrate is less than or equal to 25mg / l. According to the method, deep purification of cadmium can be achieved, and the cadmium ion content of the filtrate is remarkably reduced; the reaction time is shortened by half, and the problem of cadmium redissolution in the replacement process is avoided; the influence of excessive zinc powder on the quality of sponge cadmium is avoided; the resource recovery of the cadmium metal in the purification slag is realized; the original technological process is not changed, implementation is easy, and economic benefits are good.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrometallurgy, and particularly relates to a method for strengthening the deep replacement of cadmium in a low-cadmium solution by zinc powder by utilizing the difference in dielectric properties. Background Art

[0002] In the process of zinc hydrometallurgy, cadmium metal mainly follows the raw material zinc concentrate through roasting and leaching, and then sponge cadmium is produced through the replacement of zinc powder in the first-stage purification. However, at present, the removal of cadmium is not thorough, the cadmium content in the solution after cadmium removal is relatively low, containing 500-1000 mg / l of cadmium and 100-120 g / l of zinc. This low-cadmium solution is returned to the roasting ore leaching process as slurry-adjusting liquid, and this part of cadmium metal circulates in the processes of roasting ore leaching and first-stage purification, increasing the consumption of zinc powder in the purification process and affecting the purification efficiency. There are problems in the existing zinc powder replacement for removing cadmium from low-cadmium solutions: (1) The efficiency of zinc powder replacement for removing cadmium is low and the energy consumption is high; (2) Cadmium is easily redissolved during the replacement process, the replacement for removing cadmium is not thorough, the cadmium content in the post-liquid is greater than 500 mg / l, and cadmium metal circulates in the leaching-purification section, increasing the consumption of zinc powder and affecting the output of sponge cadmium.

[0003] Based on this, the present invention aims to provide a method for strengthening the deep replacement of cadmium in a low-cadmium solution by zinc powder by utilizing the difference in dielectric properties, so as to solve the technical problems of low efficiency of zinc powder replacement for cadmium in a low-cadmium solution, high energy consumption, incomplete replacement for removing cadmium, and increasing the treatment cost of the subsequent process. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for strengthening the deep replacement of cadmium in a low-cadmium solution by zinc powder by utilizing the difference in dielectric properties.

[0005] The purpose of the present invention is achieved as follows: The replacement method includes the following steps: Heat the cadmium-containing solution to 60-70 °C, and the cadmium-containing solution contains cadmium ions ≤ 1200 mg / l; Add zinc fine powder at 0.8-1.0 times the theoretical addition amount. The proportion of particles with a particle size < 75 μm in the zinc fine powder is > 80%, and the zinc fine powder contains Zn > 95%; While fully stirring the reaction system, perform ultrasonic strengthening on the reaction system. The ultrasonic power is 200 w, the ultrasonic frequency is 15-25 kHz, the ultrasonic intensity is 20-30%, and the ultrasonic treatment time is 20-25 min to obtain the post-replacement liquid; Perform solid-liquid separation on the post-replacement liquid. The cadmium ion content in the filtrate is ≤ 25 mg / l, and the filter residue is returned to the sponge cadmium acid dissolution section.

[0006] Compared with the prior art, the technical solution of the present invention has the following advantages: The technical solution of the present invention independently applies ultrasonic waves to the reaction of replacing cadmium with ultra-active zinc fine powder, optimizes various parameters of ultrasonic treatment, and no other medium (such as inert gas or metal ions) needs to be introduced, and the process flow is simple and efficient.

[0007] The addition amount and particle size ratio of ultra-active zinc fine powder are synergistically optimized. The particle size of the ultra-active zinc fine powder is limited to that the proportion of particles with a size less than 75 μm is greater than 80%, and the purity is greater than 95%. The higher specific surface area improves the accessibility of the reaction reagent, so that the addition amount is reduced to 0.8 - 1.0 times of the theoretical amount. The results show that this range can balance efficiency and cost.

[0008] The replacement method described in the present invention is applicable to the removal of cadmium from low-concentration cadmium solutions, especially applicable to the treatment of the secondary replacement solution after acid dissolution of sponge cadmium (Cd 2+ concentration 500 - 1200 mg / L, Zn 2+ ≥ 100 g / L, pH value 3.0 - 4.0). Through the synergistic action of heating (60 - 70 °C), stirring (400 r / min) and ultrasonic waves, deep cadmium removal is achieved by utilizing the difference in dielectric properties.

[0009] In summary, compared with the existing cadmium removal methods, the technical solution of the present invention: (1) ultrasonic waves strengthen the replacement of cadmium in low-cadmium solutions with zinc fine powder, realize deep purification of cadmium, significantly reduce the cadmium ion content in the filtrate, reduce the circulation of cadmium in the process, and reduce the consumption of zinc fine powder; (2) ultrasonic waves strengthen the improvement of the efficiency of cadmium removal by replacement, shorten the reaction time by half, avoid the problem of cadmium redissolution during the replacement process, and reduce production energy consumption; (3) adopt ultra-active zinc fine powder, with higher reaction efficiency and more thorough replacement, and avoid the influence of excessive zinc powder on the quality of sponge cadmium; (4) has good matching with production, realizes the resource recovery and utilization of cadmium metal in the purification slag; (5) does not change the original process flow, is easy to implement, and has good economic benefits. Detailed implementation mode

[0010] The present invention will be further described below, but it is not limited to the present invention in any way. Any transformation or replacement based on the teachings of the present invention belongs to the protection scope of the present invention.

[0011] The replacement method includes the following steps: Heat the cadmium-containing solution to 60 - 70 °C, and the cadmium-containing solution contains cadmium ions ≤ 1200 mg / l; Add zinc fine powder according to 0.8 - 1.0 times of the theoretical addition amount. The proportion of particles with a size less than 75 μm in the zinc fine powder is greater than 80%, and the zinc fine powder contains Zn > 95%; While fully stirring the reaction system, ultrasonic strengthening is carried out on the reaction system. The ultrasonic power is 200 w, the ultrasonic frequency is 15 - 25 kHz, the ultrasonic intensity is 20 - 30%, and the ultrasonic treatment time is 20 - 25 min to obtain the post-displacement solution. Perform solid-liquid separation on the post-displacement solution. The cadmium ion content in the filtrate is ≤25 mg / l, and the filter residue is returned to the sponge cadmium acid dissolution section.

[0012] The cadmium-containing solution is the post-displacement solution after secondary replacement of sponge cadmium acid dissolution. The cadmium-containing solution contains 500 - 1200 mg / l of cadmium ions (Cd exists in the form of Cd 2+ ), 100 - 120 g / l of zinc ions (Zn exists in the form of Zn 2+ ), and the pH value is 3.0 - 4.0.

[0013] The preferred heating temperature is 65°C.

[0014] The stirring speed is 400 r / min.

[0015] The preferred ultrasonic frequency is 20 kHz.

[0016] The preferred ultrasonic intensity is 20 - 25%.

[0017] The preferred ultrasonic treatment time is 24 - 25 min.

[0018] The solid-liquid separation is filtration.

[0019] Example 1

[0020] Take 500 ml of the post-displacement solution after secondary replacement of sponge cadmium acid dissolution in a 1000 ml beaker and heat it up to 65°C with a water bath; the solution contains Cd: 925 mg / l (Cd exists in the form of Cd 2+ ), Zn: 112 g / l (Zn exists in the form of Zn 2+ ), and the pH value is 3.5; Add 0.22 g of zinc fine powder (1 times the theoretical amount) to the solution. The proportion of particles with a particle size <75 μm in the zinc fine powder is 85%, and it contains 96% Zn.

[0021] Stir the reaction system fully at a speed of 400 r / min while performing ultrasonic strengthening. The ultrasonic power is 200 w, the ultrasonic frequency is 20 kHz, the ultrasonic intensity is 20%, and the ultrasonic treatment time is 23 min to obtain the post-displacement solution.

[0022] Filter the post-displacement solution. After detection and analysis, the filtrate contains Cd: 25 mg / l, Zn: 113 g / l, the cadmium removal rate is 97.30%, and the filter residue is returned to the sponge cadmium acid dissolution section.

[0023] Example 2

[0024] Take 500ml of the acid-dissolved secondary replacement solution of sponge cadmium in a 1000ml beaker and heat it to 60℃ in a water bath; the solution contains Cd: 1120mg / l (Cd is expressed as Cd 2+ Zn: 109 g / l (Zn exists in the form of Zn 2+ exists in the form of ), pH 3.0; 0.26 g of zinc fine powder (1 times the theoretical amount) was added to the solution. The zinc fine powder contained 91% particles with a particle size of less than 75 μm and contained 97% Zn.

[0025] The reaction system was fully stirred at a speed of 400 r / min, and ultrasonic strengthening was performed at the same time. The ultrasonic power was 200 w, the ultrasonic frequency was 25 kHz, the ultrasonic intensity was 30%, and the ultrasonic treatment time was 25 min to obtain a replaced liquid.

[0026] The replaced liquid was filtered and tested and analyzed. The filtrate contained Cd: 12 mg / l, Zn: 113 g / l, and the cadmium removal rate was 98.93%. The filter residue was returned to the sponge cadmium acid dissolution section.

[0027] Example 3

[0028] Take 500ml of the acid-dissolved secondary replacement solution of sponge cadmium in a 1000ml beaker and heat it to 70℃ in a water bath; the solution contains Cd: 1000mg / l (Cd is expressed as Cd 2+ in the form of Zn), Zn: 110g / l (Zn in the form of Zn 2+ exists in the form of ), pH 4.0; 0.20 g of zinc fine powder (0.8 times the theoretical amount) was added to the solution. The zinc fine powder contained 88% particles with a particle size of less than 75 μm and contained 96% Zn.

[0029] The reaction system was fully stirred at a speed of 400 r / min, and ultrasonic strengthening was performed at the same time. The ultrasonic power was 200 w, the ultrasonic frequency was 15 kHz, the ultrasonic intensity was 25%, and the ultrasonic treatment time was 24 min to obtain a replaced liquid.

[0030] The replaced liquid was filtered and tested and analyzed. The filtrate contained Cd: 18 mg / l, Zn: 108 g / l, and the cadmium removal rate was 98.47%. The filter residue was returned to the sponge cadmium acid dissolution section.

[0031] Example 4 A comparative experiment was conducted on the ultrasonic intensity, ultrasonic treatment time, and zinc powder particle size of the technical solution. Other experimental conditions were the same as in Example 1. The specific results are as follows: (1) Ultrasonic enhanced zinc powder replacement impurity removal intensity gradient test results: the pre-cadmium removal solution contains Cd: 890 mg / l, the ultrasonic time is 25 min, the amount of zinc powder added is 0.8 times the theoretical amount, the zinc powder particle size is 75 μm, the ultrasonic intensity is controlled at 5%, 10%, 20%, 30%, 40%, 50%, 70%, 100%, and the cadmium removal rates are 75.62%, 81.23%, 99.18%, 98.58%, 91.01%, 90.41%, 91%, 79.72%, respectively. The results show that when the ultrasonic intensity is 20%, the cadmium removal rate reaches 99.18%, which is the best control condition.

[0032] (2) Results of the time gradient test of ultrasonic enhanced zinc powder replacement and impurity removal: the pre-cadmium removal solution contained 890 mg / l of Cd, the ultrasonic intensity was controlled at 20%, the amount of zinc powder added was 0.8 times the theoretical amount, the zinc powder particle size was 75 μm, and the ultrasonic time was controlled at 15 min, 20 min, 25 min, 30 min, 35 min, and 40 min, respectively. The cadmium removal rates were 75.24%, 87.38%, 98.85%, 86.12%, 80.19%, and 74.55%, respectively. The results showed that when the ultrasonic time was 25 min, the cadmium removal rate reached 98.85%, which was the best control condition.

[0033] (3) Ultrasonic enhanced zinc powder replacement and impurity removal test results of zinc powder particle size: the pre-cadmium removal solution contains Cd: 890mg / l, the ultrasonic intensity is controlled at 20%, the ultrasonic time is 25min, the amount of zinc powder added is 0.8 times the theoretical amount, the zinc powder particle size is controlled at 185μm, 125μm, 75μm, 45μm, and the cadmium removal rates are 65.12%, 76.32%, 90.85%, and 96.66%, respectively. The results show that when the zinc powder is a fine powder with a particle size of less than 75μm, the cadmium removal rate reaches 96.66%, which is the best control condition.

[0034] Comparative Example 1 ——Cadmium removal effect of common replacement method Take 500ml of the acid-dissolved secondary replacement solution of sponge cadmium in a 1000ml beaker and heat it to 65℃ in a water bath; the solution contains Cd: 1025mg / l (Cd is expressed as Cd 2+ in the form of Zn), Zn: 116 g / l (Zn in the form of Zn 2+ exists in the form of ), pH 3.5; Add 0.22 g of ordinary zinc powder (1 times the theoretical amount) to the solution.

[0035] The reaction system was fully stirred at a speed of 400 r / min, and the reaction was terminated after 40 minutes to obtain a replaced liquid.

[0036] The replaced liquid was filtered and tested and analyzed. The filtrate contained Cd: 535 mg / l, Zn: 116 g / l, and the cadmium removal rate was 47.18%.

[0037] Comparative Example 2 ——Cadmium removal effect of common replacement method Take 500ml of the acid-dissolved secondary replacement solution of sponge cadmium into a 1000ml beaker and heat it to 65℃ in a water bath; the solution contains Cd: 890mg / l (Cd is expressed as Cd 2+ Zn: 121g / l (Zn exists in the form of Zn 2+ exists in the form of ), pH 3.5; Add 0.22 g of ordinary zinc powder (1 times the theoretical amount) to the solution.

[0038] The reaction system was fully stirred at a speed of 400 r / min, and the reaction was terminated after 40 minutes to obtain a replaced liquid.

[0039] The replaced liquid was filtered and tested and analyzed. The filtrate contained Cd: 416 mg / l, Zn: 121 g / l, and the cadmium removal rate was 53.26%.

[0040] Technical principle of the present invention: When ultrasonic waves propagate in a medium, they can cause the particles of the medium to vibrate in its propagation space, forming a radiation pressure that propagates in the direction of the sound wave, which has a strong destructive effect on the material, and can give the medium (superactive zinc fine powder) and the suspended liquid (cadmium sulfate solution) different accelerations, making the movement speed of the medium molecules much greater than the movement speed of the suspended liquid molecules, and generating friction between the two. This friction can make the zinc metal on the edge of the superactive zinc fine powder particles react with the cadmium sulfate in the solution more quickly, thereby strengthening the replacement reaction. Compared with the method without ultrasonic reinforcement, the method of deep replacement of cadmium in low-cadmium solution by using ultrasonic reinforcement zinc fine powder improves the reaction efficiency by more than 50% and shortens the replacement reaction time by half.

Claims

1. A method for enhancing the deep replacement of cadmium in a low-cadmium solution by zinc powder using the difference in dielectric properties, characterized in that It includes the following steps: Heat the cadmium-containing solution to 60 - 70 °C, where the cadmium-containing solution contains cadmium ions ≤ 1200 mg / l; Add zinc fine powder at 0.8 - 1.0 times the theoretical addition amount. In the zinc fine powder, the proportion of particles with a particle size < 75 μm is > 80%, and the zinc fine powder contains Zn > 95%; While fully stirring the reaction system, perform ultrasonic strengthening on the reaction system. The ultrasonic power is 200 w, the ultrasonic frequency is 15 - 25 kHz, the ultrasonic intensity is 20 - 30%, and the ultrasonic treatment time is 20 - 25 min to obtain the post-displacement solution; Perform solid-liquid separation on the post-displacement solution. The cadmium ion content in the filtrate is ≤ 25 mg / l, and the filter residue is returned to the sponge cadmium acid dissolution section.

2. The replacement method according to claim 1, characterized in that, The cadmium-containing solution is the post-displacement solution after the second replacement in the sponge cadmium acid dissolution.

3. The replacement method according to any one of claims 1 or 2, characterized in that, The cadmium-containing solution contains 500 - 1200 mg / l of cadmium ions, 100 - 120 g / l of zinc ions, and the pH value is 3.0 - 4.

0.

4. The replacement method according to claim 1, characterized in that, The heating temperature is 65 °C.

5. The replacement method according to claim 1, wherein The stirring speed is 400 r / min.

6. The replacement method according to claim 1, characterized in that The ultrasonic frequency is 20 kHz.

7. The replacement method according to claim 1, characterized in that, The ultrasonic intensity is 20 - 25%.

8. The replacement method according to claim 1, characterized in that, The ultrasonic treatment time is 24 - 25 min.

9. The replacement method according to claim 1, characterized in that, The solid-liquid separation is filtration.