Method for removing thallium by pre-electrolysis of zinc electrolyte

Abstract

The present application belongs to the technical field of non-ferrous hydrometallurgy, and particularly relates to a method for removing thallium from zinc electrolyte by pre-electrolysis. The method comprises the following steps: introducing the thallium-containing zinc sulfate electrolyte produced in a purification process into an electrolytic cell, inserting an inert anode and a cathode, adding manganese ions, and after power-on, oxidizing the divalent manganese ions around the anode to generate manganese oxide clusters under the electrochemical oxidation. Subsequently, all the electrolyte is directly punched into a stirring tank without solid-liquid separation, and in-situ oxidation-adsorption reaction of the electrolyte occurs in the stirring tank, thallium is adsorbed in the structure of the manganese oxide clusters, and the thallium content in the solution can be reduced to below 0.2 mg / L, which will not affect the plate burning during zinc electrodeposition. The method of the present application is directly carried out in the electrolysis process of zinc hydrometallurgy, does not need to additionally increase electrolysis facilities, is simple and efficient, and does not consume additional reagents.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of non-ferrous hydrometallurgy, and particularly relates to a method for removing thallium by pre-electrolysis of zinc electrolyte. BACKGROUND

[0002] Thallium mainly occurs in lead-zinc ore. Currently, zinc sulfate solution purification and thallium removal in the process of zinc hydrometallurgy mainly adopts zinc powder replacement method. Due to the similar deposition potentials of zinc and thallium, thallium removal is not complete, and excessive zinc powder leads to high cost.

[0003] Manganese-based materials are used for thallium removal in large quantities due to their good structural stability, oxidation characteristics, and good adsorption of thallium.

[0004] Zinc hydrometallurgy zinc sulfate electrolysis solution usually contains a certain amount of Mn 2+ , which is deposited in the form of manganese oxide on the anode and enters the anode mud during zinc deposition production. However, due to the low concentration of Mn 2+ , it cannot be deposited alone in large quantities, but is mixed and deposited with lead oxide formed after the oxidation of anode lead. In addition, the solution circulation speed is not fast enough during zinc deposition, and the formed manganese-lead anode mud is attached to the anode plate and cannot enter the solution to participate in the reaction. At this time, zinc has already started to deposit on the cathode, and if the solution contains thallium, it has already started to deposit on the anode. SUMMARY

[0005] To solve the above problems, one of the purposes of the application is to provide a method for removing thallium by pre-electrolysis of zinc electrolyte, which removes thallium by controlling the in-situ generation of manganese oxide clusters during pre-electrolysis, and has the advantages of low unit cost and simple process.

[0006] The second purpose of the application is to provide a method for removing thallium by pre-electrolysis of zinc electrolyte and its application in the process of zinc hydrometallurgy.

[0007] In view of the problems in the prior art, the application provides the following technical solutions:

[0008] A method for removing thallium by pre-electrolysis of zinc electrolyte, characterized in that it comprises the following steps:

[0009] (1) introducing zinc sulfate electrolyte containing thallium into an electrolytic cell, inserting inert anodes and cathodes, and adding manganese ions; then conducting pre-electrolysis reaction to oxidize divalent manganese ions to manganese oxide clusters; setting a certain electrolyte circulation speed during the pre-electrolysis reaction process to prevent the generated manganese oxide clusters from being attached to the anode plate;

[0010] (2) the electrolyte containing manganese oxide clusters is all introduced into the stirring tank, stirring is conducted, in-situ oxidation-adsorption reaction occurs, thallium is adsorbed in the manganese oxide clusters, and after solid-liquid separation, the thallium-removed zinc sulfate electrolyte is obtained.

[0011] Further, the zinc sulfate electrolyte of the present application mainly contains zinc sulfate, and free ions include Zn 2 + , SO4 2- , H + , Mn 2+ , Tl + , Na + , Mg 2+ , Cl - , Ca 2+ , etc. 2 , and the generated manganese oxide clusters in the electrolyte have nano-particle and molecular cluster structures, and are not removed from the solution, and have large surface potential energy, can catalyze oxidation reaction, can form good oxidation adsorption of Tl+, and thus can selectively adsorb thallium.

[0012] Further, in step (1), the content of manganese ions added is higher than 0.5 g / L; and further preferably, the content of manganese ions added is higher than 2 g / L.

[0013] Further, in step (1), the manganese ions are added in the form of manganese sulfate or manganese acetate; and further preferably, the manganese ions are added in the form of manganese sulfate.

[0014] Further, in step (1), the current density of pre-electrolysis is 100-300 A / m 2 , the temperature is 40-80℃, and the time is 30-120 min.

[0015] Further preferably, in step (1), the current density of pre-electrolysis is 200-300 A / m 2 , and the temperature is 70-80℃.

[0016] Further, in step (2), during the pre-electrolysis reaction process, the circulation speed of the electrolyte is 3-6 L / (h·L), i.e., the volume of liquid circulated per hour is 3-6 times the volume of the electrolysis tank.

[0017] Further, in step (2), during the in-situ oxidation-adsorption reaction process, the temperature is 30-70℃, the time is 10-60 min, and the stirring speed is 20-200 rpm

[0018] The present application also discloses an application of a method for removing thallium from zinc electrolyte in a zinc hydrometallurgy process, the thallium-containing zinc sulfate electrolyte is obtained from a leaching liquid purification process, and the thallium-removed zinc sulfate electrolyte is used for zinc electrodeposition production.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] The present application makes innovative adjustment to the current zinc electrolysis process, first, pre-electrolysis is carried out at an intermediate current density, which is lower than the normal zinc deposition current density, so the cathode zinc deposition is inhibited; but it is much higher than the deposition current density of electrolytic manganese dioxide, under the high concentration of added manganese ions, manganese oxide is rapidly nucleated and deposited, a large number of crystal nuclei are rapidly deposited near the anode plate, and they are clustered together before the crystal is arranged, forming amorphous clusters, at the same time, they are flushed into the solution at a high flow rate, the crystal nuclei cannot continue to grow on the anode and remain in the nano form, forming amorphous clusters composed of nanocrystals, which have strong reactivity. The anode substrate lead cannot be flushed away even if it is oxidized because it is tightly combined with the basic atomic bond, and finally only forms a zinc sulfate electrolyte containing manganese oxide clusters. At this time, the manganese oxide is always immersed in the electrolyte, retains reactivity, and directly flows into the stirred tank to carry out the thallium removal reaction by oxidation and adsorption, so that thallium is directionally oxidized and captured and adsorbed by the manganese oxide clusters with large reaction area and high reactivity, and is separated out.

[0021] (2) The present application proposes a method of pre-electrolysis for removing thallium before zinc sulfate electrolysis, which fully utilizes the Mn 2+ electrolysis system and the circulation system owned by the zinc electrolysis workshop, without external addition, generates manganese oxide clusters by pre-electrolysis before zinc deposition to remove thallium by adsorption, thereby eliminating the harm to zinc electrolysis. At the same time, the present application innovatively utilizes the zinc electrolysis tank to carry out the pre-electrolysis method for the thallium removal reaction, but does not deposit thallium on the cathode and anode, so as to not affect the deposition of zinc and process adjustment.

[0022] (3) The pre-electrolysis process of the present application does not need to increase additional equipment and consume additional reagents, the cathode and anode and the electrolysis tank are only manganese oxide cluster generation equipment, do not carry out the thallium removal reaction, and the manganese oxide clusters generated by the anode are effective materials. The manganese oxide clusters do not leave the electrolyte from synthesis to use, and are seamlessly connected from production to use, retain the reactivity of the manganese oxide clusters, can fully oxidize and adsorb thallium, reduce the thallium content in the solution to below 0.2 mg / L, and will not affect the plate burning during zinc deposition. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0024] Figure 1 It is a flowchart of the preparation method of the present application;

[0025] Figure 2 SEM photograph 1 of the manganese oxide cluster obtained in Example 1;

[0026] Figure 3 SEM photograph 2 of the manganese oxide cluster obtained in Example 1;

[0027] Figure 4 XRD result of the manganese oxide cluster obtained in Example 1;

[0028] Figure 5 SEM photograph of the manganese oxide cluster obtained in Example 4;

[0029] Figure 6 XRD result of the manganese oxide cluster obtained in Example 4. DETAILED DESCRIPTION

[0030] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present application is not limited to the following specific embodiments.

[0031] Unless otherwise defined, all the professional terms used in the following have the same meaning as understood by those skilled in the art. The professional terms used in the present application are only for the purpose of describing the specific embodiments and are not intended to limit the scope of protection of the present application.

[0032] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods.

[0033] Example 1

[0034] The composition of the zinc sulfate electrolyte containing thallium as a test raw material is: Zn 58.39 g / L, Mn 3.60 g / L, H2SO4 162 g / L, Tl 1.54 mg / L.

[0035] As shown in Figure 1 , the specific steps of the present embodiment are as follows:

[0036] (1) Preparing manganese oxide clusters by pre-electrolysis: 10 L of the above-mentioned zinc sulfate electrolyte is used for the test electrolytic cell, which is prepared by reducing the size of the standard zinc electrolytic cell. The electrolyte is heated to 70°C and then introduced into the electrolytic cell and the matching storage tank. The anode and cathode plates are placed and the circuit is connected. Manganese sulfate is added to the electrolyte to make the total manganese ion concentration reach 8 g / L. The electrolysis is carried out at a current density of 300 A / m 2 for 60 min, and the solution circulation speed is maintained at 5 L / (h·L) during the process.

[0037] After electrolysis, all electrolyte was directly transferred to a stirred tank, and samples were taken and filtered to obtain solid manganese oxide samples for SEM and XRD analysis. The results are attached. Figures 2-4 As shown.

[0038] from Figure 2 and 3 It can be seen that the microstructure of the manganese oxide sample is entirely clustered, with nano-sized and uniformly distributed particles. The clustered particles all have countless tiny tendril structures, providing sufficient contact interfaces for the efficient reaction.

[0039] from Figure 4 XRD analysis showed that the product had low diffraction intensity and high background baseline, indicating that it was amorphous and had high reactivity.

[0040] (2) Manganese oxide cluster oxidation adsorption for thallium removal: The electrolyte from the electrolytic cell was cooled slightly in the stirring tank and then stirred at a speed of 100 rpm. No reagents were added during the process. The reaction temperature was kept at 60℃. After 30 min of reaction, stirring was stopped, the filtrate was filtered and separated, and a sample was taken for ICP analysis. The Tl content was found to be 0.11 mg / L. The thallium removal rate was calculated to be 92.86%, indicating that the thallium removal reaction was complete.

[0041] Example 2

[0042] The composition of the purified zinc sulfate solution containing thallium used as the test stock solution is the same as in Example 1.

[0043] like Figure 1 As shown, the specific steps in this embodiment are as follows:

[0044] (1) Pre-electrolysis preparation of manganese oxide clusters: Take 10L of the above zinc sulfate electrolyte. The electrolytic cell used in the experiment is made by scaling down the size of the standard zinc electrolytic cell. After heating the electrolyte to 40℃, it is introduced into the electrolytic cell and the matching storage tank. Place the anode and cathode plates and connect the circuit. Add manganese sulfate to make the total manganese ion concentration reach 6g / L. At 200A / m 2 Electrolysis was performed at a current density of 120 min, with the solution circulation rate maintained at 3.5 L / (h∙L) during the process.

[0045] After electrolysis is complete, all the electrolyte is directly placed into the stirred tank.

[0046] (2) Manganese oxide cluster oxidation adsorption for thallium removal: The electrolyte from the electrolytic cell was cooled slightly in the stirring tank and then stirred at a speed of 160 rpm. No reagents were added during the process, and the reaction temperature was kept at 40℃. After 30 min of reaction, stirring was stopped, the filtrate was filtered and separated, and a sample was taken for ICP analysis. The Tl content was found to be 0.20 mg / L. The thallium removal rate was calculated to be 87.01%, and the thallium removal reaction was complete.

[0047] Example 3

[0048] The composition of the purified thallium-containing zinc sulfate solution used as the test stock solution is the same as that of Example 1.

[0049] As shown in Figure 1 , the specific steps of this example are as follows:

[0050] (1) Preparation of manganese oxide clusters by pre-electrolysis: 10 L of the above-mentioned zinc sulfate electrolyte was used for the test electrolytic cell, which was made by reducing the size of a standard zinc electrolytic cell. The electrolyte was heated to 80°C and then introduced into the electrolytic cell and the matching storage tank. The anode and cathode plates were placed and the circuit was connected. Manganese sulfate was added to the electrolyte to make the total manganese ion concentration reach 10 g / L. The electrolysis was carried out at a current density of 300 A / m 2 for 40 min, and the solution circulation speed was maintained at 5 L / (h·L) during the process.

[0051] After the electrolysis was completed, all the electrolyte was directly put into the stirring tank.

[0052] (2) Oxidation and adsorption of thallium by manganese oxide clusters: the electrolyte from the electrolytic cell was stirred after being slightly cooled in the stirring tank at a speed of 160 revolutions / min. No reagent was added during the process, and the reaction temperature was maintained at 50°C. After 30 min of reaction, the stirring was stopped, the filtrate was separated by filtration, and the sample was analyzed by ICP to obtain a Tl content of 0.03 mg / L. The thallium removal rate was calculated to be 98.05%, and the thallium removal reaction was complete.

[0053] Example 4

[0054] The composition of the purified thallium-containing zinc sulfate solution used as the test stock solution is the same as that of Example 1, and the manganese source used is manganese acetate.

[0055] As shown in Figure 1 , the specific steps of this example are as follows:

[0056] (1) Preparation of manganese oxide clusters by pre-electrolysis: 10 L of the above-mentioned zinc sulfate electrolyte was used for the test electrolytic cell, which was made by reducing the size of a standard zinc electrolytic cell. The electrolyte was heated to 60°C and then introduced into the electrolytic cell and the matching storage tank. The anode and cathode plates were placed and the circuit was connected. Manganese acetate was added to the electrolyte to make the total manganese ion concentration reach 10 g / L. The electrolysis was carried out at a current density of 150 A / m 2 for 90 min, and the solution circulation speed was maintained at 2 L / (h·L) during the process.

[0057] After the electrolysis was completed, all the electrolyte was directly put into the stirring tank. The solid manganese oxide sample was obtained by filtering the sample and analyzed by SEM and XRD, and the results are shown in Figure 4 and Figure 5 .

[0058] From Figure 5It can be seen that, similar to the case of manganese sulfate as manganese source, the manganese oxide sample forms a cluster structure ball, which is very uniform.

[0059] Figure 6 The XRD also shows that the product is amorphous manganese oxide, the overall diffraction intensity is still not high, and has high reactivity; but the baseline intensity is obviously lower than that of the sample of Example 1, indicating that the manganese oxide obtained at the slightly lower current density has better crystallinity, which again confirms the rationality of the intermediate current density used in the present application for preparing amorphous manganese oxide clusters.

[0060] (2) Oxidative adsorption of thallium by manganese oxide clusters: the electrolyte from the electrolytic cell is cooled slightly in the stirring tank, and stirring is started at a speed of 50 revolutions / min, without adding any reagent during the process, and the reaction temperature is maintained at 45°C. After 20 min of reaction, stirring is stopped, the filtrate is separated by filtration, and ICP analysis of the sample shows that the Tl content is 0.16 mg / L, and the thallium removal rate is calculated to be 89.61%, and the thallium removal reaction is complete.

[0061] Example 5

[0062] The composition of the purified thallium-containing zinc sulfate solution used as the test stock solution is the same as that of Example 1, and the manganese source used is manganese acetate.

[0063] As shown in Figure 1 , the specific steps of the present embodiment are as follows:

[0064] (1) Preparation of manganese oxide clusters by pre-electrolysis: 10 L of the above-mentioned zinc sulfate electrolyte is used for the test, and the electrolytic cell is prepared by reducing the size of a standard zinc electrolytic cell. The electrolyte is heated to 70°C and then introduced into the electrolytic cell and the matching storage tank. The anode and cathode plates are placed and the circuit is connected. Manganese acetate is added to the electrolyte to make the total manganese ion concentration reach 10 g / L. Electrolysis is carried out at a current density of 250 A / m 2 for 60 min, and the solution circulation speed is maintained at 4 L / (h·L) during the process.

[0065] After electrolysis is completed, all the electrolyte is directly placed into the stirring tank.

[0066] (2) Oxidative adsorption of thallium by manganese oxide clusters: the electrolyte from the electrolytic cell is cooled slightly in the stirring tank, and stirring is started at a speed of 70 revolutions / min, without adding any reagent during the process, and the reaction temperature is maintained at 35°C. After 60 min of reaction, stirring is stopped, the filtrate is separated by filtration, and ICP analysis of the sample shows that the Tl content is 0.08 mg / L, and the thallium removal rate is calculated to be 94.81%, and the thallium removal reaction is complete.

[0067] The above only describes the preferred embodiments of the present application, and it should be noted that for ordinary skilled persons in the technical field, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered within the protection scope of the present application.

Claims

1. A method for pre-electrolytic depletion of thallium in a zinc electrolyte, characterized in that, Includes the following steps: (1) A zinc sulfate electrolyte containing thallium is introduced into an electrolytic cell, an inert anode and a cathode are inserted, and manganese ions are added; then an electric current is applied to carry out a pre-electrolysis reaction, with a pre-electrolysis current density of 100~300 A / m. 2 The divalent manganese ions are oxidized to form manganese oxide clusters; During the pre-electrolysis reaction, the electrolyte circulation rate is 3~6 L / (h∙L), so that the generated manganese oxide clusters do not stick to the anode plate; (2) The electrolyte containing manganese oxide clusters is passed into the stirring tank and stirred to produce an in-situ oxidation-adsorption reaction. Thallium is adsorbed in the manganese oxide clusters. After solid-liquid separation, zinc sulfate electrolyte after thallium removal is obtained.

2. The method as described in claim 1, characterized in that, In step (1), the manganese ion content is higher than 0.5 g / L.

3. The method as described in claim 2, characterized in that, In step (1), the amount of manganese ions added is higher than 2 g / L.

4. The method according to any one of claims 1 to 3, characterized in that, In step (1), the manganese ions are added in the form of manganese sulfate or manganese acetate.

5. The method as described in claim 1, characterized in that, In step (1), the pre-electrolysis temperature is 40~80℃ and the time is 30~120min.

6. The method as described in claim 5, characterized in that, In step (1), the current density of the pre-electrolysis is 200~300 A / m. 2 The temperature is 70~80℃.

7. The method as described in claim 1, characterized in that, In step (2), the in-situ oxidation-adsorption reaction process is carried out at a temperature of 30~70℃, a time of 10~60min, and a stirring speed of 20~200rpm.

8. The method as described in claim 1, characterized in that, The thallium-containing zinc sulfate electrolyte is produced by the leaching solution purification process. The zinc sulfate electrolyte after thallium removal is used for zinc electrowinning.

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