Method for purifying waste electrolyte in zinc electrolysis process

Abstract

The invention relates to a method for purifying waste electrolyte in a zinc electrolysis process, and belongs to the technical field of metallurgical engineering. The method comprises the following steps: (1) introducing compressed air into a closed gas storage container, and when the pressure in the gas storage container reaches 2-3 kg / cm < 2 >, introducing waste electrolyte for gas dissolving treatment; (2) introducing the waste electrolyte subjected to the gas dissolving treatment into a closed ultrasonic oil removal tank for air floatation treatment for a period of time, wherein the pressure in the ultrasonic oil removal tank is not lower than 0.3 Mpa in the air floatation treatment process; an ultrasonic generator is arranged in the ultrasonic oil removal tank; and (3) standing and aging the waste electrolyte subjected to air flotation treatment for a period of time, and starting an ultrasonic generator in the ultrasonic oil removal tank to perform ultrasonic treatment on the waste electrolyte. By means of the method, efficient treatment of the waste electrolyte is achieved. The main component content (g / L) of the treated waste electrolyte is 158 g / L, Zn is 38.29 g / L, Mg is 28.43 g / L, Mn is 6.10 g / L, the impurity element content (mg / L) is 0.16 g / L, Cd is 0.09 g / L, Co is 0.37 g / L, Ge is 0.022 g / L, Pb is 0.46 g / L, Sr is 8.10 g / L, TOC is 38.60 g / L, and the turbidity is 1750 NTU.

Description

Technical Field

[0001] The present application relates to the field of metallurgical engineering technology, and in particular to a method for purifying waste electrolyte in a zinc electrolysis process. Background Art

[0002] During the zinc electrolysis process, zinc ions are deposited as metallic zinc at the cathode, and oxygen is released by electrolyzing water at the anode. Because the reduction potential of zinc is -0.763V, before zinc is precipitated at the cathode, elements with higher reduction potentials such as copper, lead, and tin in the solution will preferentially deposit on the cathode plate, affecting the quality of zinc. Therefore, the zinc sulfate solution needs to be deeply purified and impurities removed before entering the electrolysis to control the impurity elements within a certain range: Co<0.5mg / L, Cd<0.5mg / L, Cu<0.2mg / L, As<0.01mg / L, Sb<0.01mg / L, Ge<0.05mg / L, Fe<10mg / L. As major zinc smelters have increasingly strict control over the quality of new liquid, the yield of No. 0 zinc has also increased significantly to more than 90%, but it is very difficult to make further breakthroughs. Of the solution entering the zinc electrolytic cell, only about 10% is new solution, and the remaining 90% is recycled waste electrolyte. Research has found that in order to further improve the quality of the output zinc, in addition to maintaining strict control of the quality of the new solution, the waste electrolyte added to the zinc electrolytic cell needs to be purified and cleaned.

[0003] Furthermore, gelatin is added during zinc electrolysis to improve the apparent morphology of the precipitated zinc flakes. Some of it will be oxidized and broken at the anode during zinc electrolysis, and some will remain in the electrolyte. In addition, in order to control the lead content of the zinc flakes, strontium carbonate is added, and strontium sulfate is formed in the zinc sulfate solution to co-precipitate with the lead ions in the solution to remove the lead ions. In addition, during zinc electrolysis, zinc is precipitated at the cathode, and in addition to releasing oxygen by electrolyzing water at the anode, some of the divalent manganese ions in the solution will be oxidized to manganese dioxide and deposited on the surface of the anode plate to prevent the anode plate from being corroded. Some lead compounds will also be mixed in. When the anode mud on the surface of the anode plate falls off, it will enter the electrolyte together. This part of the slag will also affect the quality of the zinc flakes.

[0004] In summary, the waste electrolyte from the zinc electrolysis cycle needs to enter the sedimentation tank to remove some particulate matter, but the residual organic matter and suspended particles in the solution remain in the electrolyte cycle. The presence of these impurities restricts the further improvement of the zinc sheet grade rate.

[0005] In order to solve the problem of impurities in the waste electrolyte, some people have proposed to use filter pressing to remove them. This method is effective in removing suspended particles in the electrolyte, but it is not effective for the organic matter remaining in it. Moreover, the biggest problem is that the circulation volume of the waste electrolyte is very large, which is 20-30 times that of the new electrolyte. For example, a zinc plant with an annual output of 100,000 tons of zinc ingots has a daily new electrolyte volume of about 5000m3. 3 , so the waste liquid circulation volume is 100,000-150,000 m3 , with the waste electrolyte filtration rate of 0.3m 3 / (m 2 h), 100m is required 2 There are about 150 filter presses, which also need to be equipped with corresponding pumps, equipment management personnel, slag unloading personnel, etc. The cost is very high and it is difficult to apply in actual production. By increasing the circulation volume of the electrolyte and increasing the sedimentation time of the electrolyte, it has a certain effect to a certain extent, but the effect is relatively limited.

[0006] In order to remove the organic matter remaining in the waste electrolyte, it has been proposed to use activated carbon adsorption for removal. This method is effective for removing organic matter, but very high-quality wood activated carbon must be used. When activated carbon of other qualities adsorbs organic matter, the metal and non-metal elements contained in it will be dissolved by sulfuric acid in the waste liquid into the electrolyte, causing the treated solution to be unable to be recycled back to the electrolytic cell for use. In addition, after activated carbon adsorption, the slurry needs to be separated from the liquid and solid. It is difficult for a filter press to meet the requirements of such a large solution volume.

[0007] In addition, the prior art discloses a method for reducing the power consumption of zinc electrolysis in the publication number CN113668015A. In this method, when the problem of organic matter in the electrolyte is addressed, the electrolyte is synergistically acted by electrodialysis-ultrasound to achieve the effect of rapid separation and degradation of organic matter. Specifically, the patent document discloses the following technical content: the electrodialysis selective membrane separates sulfuric acid, organic matter and zinc sulfate, respectively obtaining a melt containing sulfuric acid and organic matter, and an aqueous solution containing a large amount of zinc sulfate, and reducing the sulfuric acid concentration in zinc electrolysis to more than 50-80g / L, and reducing the organic matter concentration by 20-30%. Although this method can reduce organic matter, the process not only reduces the acidity, but also produces an aqueous solution containing a large amount of zinc sulfate, which is difficult to connect with the existing electro-zinc system. In addition, the process cost of electrodialysis is high, and the operating requirements are also high, so the practicality of this solution is poor and it is not convenient for industrial application.

[0008] Therefore, how to efficiently and low-cost remove organic matter and suspended particles contained in waste electrolyte has always been a technical problem that needs to be solved urgently by technicians in this field. Summary of the invention

[0009] In order to solve or partially solve the problems existing in the related art, the present application provides a method for purifying zinc electrolysis waste electrolyte, which can efficiently remove organic matter and suspended particles (solid contents) in the waste electrolyte, has a large processing capacity, high efficiency, and is easy to apply in industry.

[0010] A method for purifying waste electrolyte in a zinc electrolysis process in the present application comprises the following steps:

[0011] (1) Introduce compressed air into a closed gas storage container until the pressure in the gas storage container reaches 2-3 kg / cm 2 When the waste electrolyte is introduced for dissolved gas treatment;

[0012] (2) introducing the waste electrolyte after the dissolved gas treatment into a closed ultrasonic degreasing tank for flotation treatment for a period of time, and maintaining the pressure in the ultrasonic degreasing tank not less than 0.3 MPa during the flotation treatment; the ultrasonic degreasing tank is provided with an ultrasonic generator;

[0013] (3) leaving the waste electrolyte after flotation treatment to stand for a period of time, and turning on the ultrasonic generator in the ultrasonic degreasing tank to perform ultrasonic treatment on the waste electrolyte;

[0014] The upper foam oil in the waste electrolyte obtained after ultrasonic treatment is collected and filtered, and the liquid after filtration is returned to the leaching process;

[0015] The lower layer of spent electrolyte obtained after removing the foamy oil from the spent electrolyte obtained after ultrasonic treatment is returned to the electrolysis process.

[0016] Furthermore, during the ultrasonic treatment in step (3), the power of the ultrasonic generator is 600-1000W, and the ultrasonic intensity is 0.5-1.5W / cm 3 , the ultrasonic treatment temperature is 40-50℃.

[0017] Furthermore, the flotation treatment time in step (2) is 60 min-120 min.

[0018] Furthermore, the standing aging time in step (3) is more than 30 minutes.

[0019] Mechanism of action of this application:

[0020] The flotation method uses highly dispersed microbubbles as carriers to adhere to suspended matter in wastewater, making it less dense than water and float to the surface of the water to achieve solid-liquid separation. It can be used to separate solids from solids, solids from liquids, liquids from liquids, and even ions in solutes.

[0021] The cavitation effect and demulsification effect of ultrasound are applied to the removal of residual organic matter and particulate matter treatment of waste electrolyte, which has a miraculous effect. Under the action of ultrasonic demulsification effect, the inter-enclosed particles formed by organic matter and solution in waste electrolyte will be broken, and organic matter will diffuse to the surface of solution. Under the action of ultrasonic cavitation, the diffusion speed is very fast, and organic matter will be driven to the surface of solution to form a foam layer within a time range of seconds. The removal of organic matter can be achieved by discharging the foam layer in time. In addition, in the process of organic matter floating up, the tiny particles in the waste electrolyte that are difficult to settle will float to the surface of solution together with the organic foam, and be removed from the electrolyte together with the foam. With the removal of organic matter in the solution, the viscosity of the solution decreases, and the sedimentation rate of larger particles in the waste electrolyte is accelerated, which accelerates the removal of particulate matter in the solution; the discharged foam layer only needs to use a filter press for liquid-solid separation to separate the particles from the electrolyte. This part of the electrolyte cannot be returned to the zinc electrolysis system, and needs to be sent to the leaching of zinc-containing raw materials for use, and the filter residue is stored or enters the pyrometallurgical harmless treatment.

[0022] The beneficial effects of this application are:

[0023] (1) After the waste electrolyte is subjected to aeration treatment by the method of the present application, it is subjected to flotation treatment, static aging, and ultrasonic treatment in sequence. The upper foam oil in the waste electrolyte obtained after the ultrasonic treatment is collected and filtered, and the liquid after the filtration is returned to the leaching process; the lower layer of waste electrolyte obtained after removing the foam oil from the waste electrolyte obtained after the ultrasonic treatment is returned to the electrolysis process. In this way, efficient treatment of the waste electrolyte is achieved. Through the method of the present application, not only can the content of organic matter and solid content be effectively reduced, but the filtrate and filter residue obtained after the treatment can also be directly connected to the existing system.

[0024] (2) Since the ultrasonic demulsification of floating oil takes a very short time, the organic matter in the waste electrolyte can be driven to the surface of the solution within seconds, which is many times more efficient than using filter presses and other methods. It has obvious advantages for treating a large amount of solution.

[0025] (3) Ultrasonic demulsification of floating oil, no additives are added, so no impurities are introduced into the electrolyte. After treatment, the solution is directly returned to zinc electrolysis for use.

[0026] (4) In the present application, only a small amount of foam oil on the surface of the treated waste electrolyte needs to be separated into organic matter and solution. The operation is convenient and efficient. There is no need to equip a large number of filter presses. The waste electrolyte can be purified using one filter press.

[0027] (5) In this application, the quality of electrolytic zinc can be effectively improved after the waste electrolyte and waste liquid are purified, which is beneficial for zinc smelting enterprises to open up new markets and enhance their core competitiveness.

[0028] (6) Compared with the prior art method of removing organic matter from waste electrolyte by electrodialysis-ultrasound synergy, the present application does not require any complicated and expensive electrodialysis process, and only needs to go through dissolved gas treatment, flotation treatment, static aging, ultrasonic treatment, and filter press treatment to achieve efficient removal of organic matter from waste electrolyte. The entire operation process is simple to operate and the cost is relatively low. The treated liquid and slag are also easy to handle. Therefore, the solution in the present application is more suitable for industrial application in enterprises. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The above and other objects, features and advantages of the present application will become more apparent through a more detailed description of exemplary embodiments of the present application in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the present application.

[0030] Figure 1 It is a schematic diagram of the process flow in this application;

[0031] Figure 2 It is a schematic diagram of the electrolytic waste liquid before treatment in this application;

[0032] Figure 3 It is a schematic diagram of the electrolytic waste liquid obtained after being treated by the method in this application. DETAILED DESCRIPTION

[0033] The embodiments of the present application will be described in more detail below with reference to examples. Although the embodiments of the present application are shown in the examples, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present application more thorough and complete, and the scope of the present application can be fully communicated to those skilled in the art.

[0034] Example 1

[0035] like Figure 1 As shown, a method for purifying waste electrolyte in a zinc electrolysis process comprises the following steps:

[0036] (1) Compressed air is introduced into a closed gas storage container until the pressure in the gas storage container reaches 2 kg / cm 2 When the waste electrolyte is introduced for gas dissolution treatment; the gas storage container in this embodiment is a gas storage tank, which is resistant to corrosion by the waste electrolyte; Figure 2 centered is a schematic diagram of the appearance of the electrolytic waste liquid before treatment in this application;

[0037] Chemical composition analysis of waste electrolyte before treatment: main component content of waste electrolyte (g / L) H2SO4 160, Zn39.08, Mg26.55, Mn 6.29, impurity element content (mg / L) Cu 0.16, Cd 0.09, Co 0.25, Ge 0.035, Pb 1.55, Sr12.22, TOC 43.89, turbidity 2075NTU.

[0038] (2) introducing the waste electrolyte after the dissolved gas treatment into a closed ultrasonic degreasing tank for flotation treatment for 120 minutes, and maintaining the pressure in the ultrasonic degreasing tank not less than 0.3 MPa during the flotation treatment; the ultrasonic degreasing tank is provided with an ultrasonic generator;

[0039] (3) The waste electrolyte after flotation treatment was allowed to stand for 30 minutes, and the ultrasonic generator in the ultrasonic degreasing tank was turned on to perform ultrasonic treatment on the waste electrolyte; the power of the ultrasonic generator was 1000 W, and the ultrasonic intensity was 0.5 W / cm 3 , the ultrasonic treatment temperature is 40°C;

[0040] The upper foam oil in the waste electrolyte obtained after ultrasonic treatment is collected and filtered, and the liquid after filtration is returned to the leaching process;

[0041] The lower layer of spent electrolyte (such as Figure 3 As shown) returns to the electrolysis process. Figure 3 It is a schematic diagram of the electrolytic waste liquid obtained after being treated by the method in this application.

[0042] Chemical composition analysis of the waste electrolyte obtained after treatment: main component content of the waste electrolyte (g / L) H2SO4 158, Zn 38.63, Mg 28.42, Mn 6.08, impurity element content (mg / L) Cu 0.16, Cd 0.10, Co 0.23, Ge 0.03, Pb0.46, Sr 7.60, TOC 27.26, turbidity 1525NTU.

[0043] In this Example 1, the removal rate of organic matter (TOC) is 37.89%, and the reduction rate of turbidity is 26.51%.

[0044] Example 2

[0045] A method for purifying waste electrolyte in a zinc electrolysis process comprises the following steps:

[0046] (1) Compressed air is introduced into a closed gas storage container until the pressure in the gas storage container reaches 3 kg / cm 2 When the waste electrolyte is introduced for gas dissolution treatment; the gas storage container in this embodiment is a gas storage tank, which is resistant to corrosion by the waste electrolyte;

[0047] Chemical composition analysis of waste electrolyte before treatment: main component content of waste electrolyte (g / L) H2SO4 158, Zn38.58, Mg26.45, Mn 6.08, impurity element content (mg / L) Cu 0.15, Cd 0.10, Co 0.35, Ge 0.032, Pb 1.52, Sr12.31, TOC 44.45, turbidity 2088NTU.

[0048] (2) introducing the waste electrolyte after the dissolved gas treatment into a closed ultrasonic degreasing tank for flotation treatment for 60 minutes, and maintaining the pressure in the ultrasonic degreasing tank not less than 0.3 MPa during the flotation treatment; the ultrasonic degreasing tank is provided with an ultrasonic generator;

[0049] (3) The waste electrolyte after flotation treatment was allowed to stand for 60 minutes, and the ultrasonic generator in the ultrasonic degreasing tank was turned on to perform ultrasonic treatment on the waste electrolyte; the power of the ultrasonic generator was 600 W, and the ultrasonic intensity was 1.5 W / cm 3 , the ultrasonic treatment temperature is 50°C;

[0050] The upper foam oil in the waste electrolyte obtained after ultrasonic treatment is collected and filtered, and the liquid after filtration is returned to the leaching process;

[0051] The lower layer of spent electrolyte obtained after removing the foamy oil from the spent electrolyte obtained after ultrasonic treatment is returned to the electrolysis process.

[0052] Chemical composition analysis of the waste electrolyte obtained after treatment: main component content of the waste electrolyte (g / L) H2SO4 156, Zn 38.55, Mg 25.58, Mn 6.01, impurity element content (mg / L) Cu 0.15, Cd 0.10, Co 0.24, Ge 0.028, Pb 0.48, Sr 7.31, TOC 27.45, turbidity 1545NTU.

[0053] In this Example 2, the removal rate of organic matter (TOC) is 38.25%, and the reduction rate of turbidity is 26.01%.

[0054] The embodiments of the present application have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to the technology in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A method for purifying waste electrolyte in a zinc electrolysis process, characterized in that: The following steps are involved: (1) Introduce compressed air into a closed gas storage container until the pressure in the gas storage container reaches 2-3 kg / cm 2 When the waste electrolyte is introduced for dissolved gas treatment; (2) introducing the waste electrolyte after the dissolved gas treatment into a closed ultrasonic degreasing tank for flotation treatment for a period of time, and maintaining the pressure in the ultrasonic degreasing tank not less than 0.3 MPa during the flotation treatment; the ultrasonic degreasing tank is provided with an ultrasonic generator; (3) leaving the waste electrolyte after flotation treatment to stand for a period of time, and turning on the ultrasonic generator in the ultrasonic degreasing tank to perform ultrasonic treatment on the waste electrolyte; The upper foam oil in the waste electrolyte obtained after ultrasonic treatment is collected and filtered, and the liquid after filtration is returned to the leaching process; The lower layer of spent electrolyte obtained after removing the foamy oil from the spent electrolyte obtained after ultrasonic treatment is returned to the electrolysis process.

2. A method for purifying waste electrolyte in a zinc electrolysis process according to claim 1, characterized in that: During the ultrasonic treatment in step (3), the power of the ultrasonic generator is 600-1000W, and the ultrasonic intensity is 0.5-1.5W / cm 3 , the ultrasonic treatment temperature is 40-50℃.

3. A method for purifying waste electrolyte in a zinc electrolysis process according to claim 1, characterized in that: The flotation treatment time in step (2) is 60 min-120 min.

4. A method for purifying waste electrolyte in a zinc electrolysis process according to claim 1, characterized in that: The standing aging time in the step (3) is more than 30 minutes.

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