Method for removing thallium from zinc sulfate solution

Abstract

The invention provides a method for removing thallium from a zinc sulfate solution, which comprises the following steps: adding acid to adjust the pH value of the zinc sulfate solution to be less than or equal to 2.5, and then adding ferrous sulfate to enable the concentration of iron ions in the solution to be 1.5-2.0 g / L; introducing ozone into the zinc sulfate solution added with the ferrous sulfate, adding alkali to adjust the pH value to 4.5-5.0 after primary reaction, and then continuously reacting to obtain a reacted solution; and adding gelatin into the reacted solution, stirring, standing and filtering to obtain the thallium-removed zinc sulfate solution. According to the method for removing thallium from the zinc sulfate solution, the technological process is simple, thallium in the zinc sulfate solution can be effectively removed, and the removal rate of thallium in the zinc sulfate solution can reach 50%-60%.

Description

Technical Field

[0001] The invention relates to the technical field of hydrometallurgical zinc solution purification, and in particular to a method for removing thallium from a zinc sulfate solution. Background Art

[0002] Thallium is a sulfur-loving and copper-loving element, often associated with sulfide ores such as lead, zinc, copper, and iron. It is a harmful impurity element in the hydrometallurgical zinc smelting process. It enters the smelting system from the raw material end and is dispersed in flue gas, slag, solution, and wastewater. Thallium in flue gas enters the dirty acid or acidic wastewater during washing. Thallium in slag is mainly enriched in high-fluorine and chlorine smoke from multi-hearth furnaces. Thallium in solution comes from the leaching of roasted sand, and most of it enters the purified slag during zinc powder replacement. Most of the thallium in wastewater enters the slag during lime neutralization-sulfurization precipitation.

[0003] The key to the impact of thallium on zinc smelting lies in the solution. Studies have shown that when the thallium content in the electrolyte exceeds 0.6 mg / L, it will cause severe "burning" of the precipitated zinc and induce other impurities to "burn", resulting in the inability to precipitate zinc normally, which will have an adverse effect on product output and technical and economic indicators, leading to continuous fluctuations in production. Therefore, the open circuit of thallium in the zinc sulfate solution of hydrometallurgical zinc smelting has always been a difficult problem in the industry.

[0004] The main methods for removing thallium from zinc sulfate solution in wet zinc smelting include precipitation, adsorption, ion exchange, biological preparation and other methods. Currently, precipitation and adsorption are the main methods in industrial applications.

[0005] There is a method of removing thallium by using electrolytic anode mud in the cadmium wet leaching stage, so that thallium is oxidized by the anode mud and precipitated into the slag. This method is beneficial to the stable control of thallium in the new electrolytic solution, but it has problems such as small processing capacity, unstable thallium removal effect, large amount of anode mud, low utilization rate, and easy blockage of pipes and tanks.

[0006] There is also a process for removing thallium by using ozone to catalytically oxidize thallium-, arsenic- and cadmium-containing wastewater, but the required pH is 10-11. The oxidizing ability of hydroxyl radicals produced by ozone under alkaline conditions is greater than that of ozone, and thallium is removed by oxidation. Under this condition, most heavy metal ions will be hydrolyzed and precipitated, which is not suitable for the removal of thallium in zinc sulfate solution in wet zinc smelting.

[0007] Therefore, how to effectively remove thallium from zinc sulfate solution through a simple process is an urgent problem to be solved in the current hydrometallurgical zinc smelting industry. Summary of the invention

[0008] The technical problem to be solved by the present invention is to provide a method for removing thallium from a zinc sulfate solution which has a simple process flow and can effectively remove thallium.

[0009] In order to solve the above technical problems, the present invention provides a method for removing thallium from a zinc sulfate solution, comprising the following steps:

[0010] Acid is added to adjust the pH of the zinc sulfate solution to ≤ 2.5, and then ferrous sulfate is added to make the iron ion concentration in the solution reach 1.5-2.0 g / L;

[0011] Passing ozone into the zinc sulfate solution after adding ferrous sulfate, adding alkali to adjust the pH to 4.5-5.0 after the initial reaction, and then continuing the reaction to obtain a post-reaction solution;

[0012] Add cow glue to the solution after the reaction, stir, let stand, and filter to obtain the zinc sulfate solution after thallium is removed.

[0013] Furthermore, in the zinc sulfate solution, the zinc ion concentration is 40-180 g / L, the total iron ion concentration is 0.01-1.5 g / L, the manganese ion concentration is 1.5-3.5 g / L, and the thallium ion concentration is not less than 0.8 mg / L.

[0014] Furthermore, the acid added to adjust the pH of the zinc sulfate solution is dilute sulfuric acid or / and electrolytic waste liquid, and the concentrations of the dilute sulfuric acid and the electrolytic waste liquid are both 150-200 g / L.

[0015] Furthermore, when ozone is introduced into the zinc sulfate solution after adding ferrous sulfate, the temperature of the solution is 40-80° C., the concentration of the ozone is 60-100 mg / L, and the amount of ozone introduced is 10-40 ml of ozone per minute per liter of solution.

[0016] Furthermore, the initial reaction time after the introduction of ozone is 30 to 45 minutes, and the reaction time after the addition of alkali to adjust the pH is 45 to 60 minutes.

[0017] Furthermore, after ozone is introduced into the zinc sulfate solution to which ferrous sulfate has been added, an explosion device is used to enhance the mass transfer between ozone and the solution.

[0018] Furthermore, the alkali used for adjusting the pH value is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and sodium bicarbonate.

[0019] Furthermore, the alkali is added in the form of an alkali solution, and the mass concentration of the alkali solution is 10% to 20%.

[0020] Furthermore, the temperature of the solution after the reaction is maintained at 40-80°C, the concentration of cow glue in the solution after the reaction is 0.5-2.0 g / L, and the cow glue is added in the form of a cow glue solution, which is a cow glue solution with a mass percentage concentration of 5-20% obtained by dissolving cow glue in water at 60-70°C.

[0021] Furthermore, after adding the cow glue to the reaction solution, the stirring time is 3 to 8 minutes and the standing time is 10 to 20 minutes.

[0022] The invention provides a method for removing thallium from a zinc sulfate solution. Ozone is introduced into a zinc sulfate solution for hydrometallurgical zinc smelting, and the catalytic oxidation of divalent manganese ions in the solution in the ozone system can be used to convert monovalent thallium ions in the solution into trivalent thallium ions. Then, alkali is added to the zinc sulfate solution, and the pH value of the solution is controlled within a reasonable range. Finally, thallium hydroxide precipitation can be obtained by hydrolysis to remove thallium from the zinc sulfate solution. The removal rate of thallium in the zinc sulfate solution can reach 50%-60%, thereby ensuring the effective removal of thallium and avoiding the loss of zinc.

[0023] In addition, the present invention provides a method for removing thallium from a zinc sulfate solution, which includes adding ferrous sulfate to the zinc sulfate solution in advance, oxidizing divalent ferrous ions into trivalent ferrous ions under the action of ozone and hydrolyzing them into ferric hydroxide, and adsorbing thallium hydroxide produced by hydrolysis to form a coprecipitate, making it easier to separate thallium from the zinc sulfate solution.

[0024] At the same time, the present invention provides a method for removing thallium from a zinc sulfate solution. After ozone is introduced into the zinc sulfate solution for a preliminary reaction, alkali is added to control the pH value of the solution to continue the reaction, and then the thallium in the solution is flocculated and precipitated. Finally, the zinc sulfate solution after the thallium is removed is obtained by filtering. Not only is the process simple, but also no impurity elements harmful to hydrometallurgy are introduced, and the method is suitable for purifying thallium in the zinc sulfate solution. At the same time, it is easy to connect with the existing hydrometallurgy process, and can realize the effective opening of thallium in the zinc sulfate solution, thereby providing a guarantee for the stable operation of zinc electrolysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A flow chart of a method for removing thallium from a zinc sulfate solution provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] See also Figure 1 The present invention provides a method for removing thallium from a zinc sulfate solution, comprising the following steps:

[0027] Step 1) pretreatment: adding acid to adjust the pH of the zinc sulfate solution to ≤2.5, and then adding ferrous sulfate to make the iron ion concentration in the solution reach 1.5-2.0 g / L. By adjusting the pH of the zinc sulfate solution to ≤2.5, the ferrous sulfate can be fully dissolved in the zinc sulfate solution to increase the iron ion concentration in the solution, which is conducive to the production of sufficient ferric hydroxide and thallium hydroxide co-precipitation in the subsequent process, thereby facilitating the precipitation of thallium from the zinc sulfate solution.

[0028] Among them, the zinc ion concentration in the zinc sulfate solution is 40-180 g / L, the total iron ion concentration is 0.01-1.5 g / L, the manganese ion concentration is 1.5-3.5 g / L, and the thallium ion concentration is not less than 0.8 mg / L.

[0029] The acid added to the zinc sulfate solution is dilute sulfuric acid and / or electrolytic waste liquid.

[0030] Furthermore, the concentrations of the dilute sulfuric acid and the electrolytic waste liquid are both 150-200 g / L.

[0031] Step 2) catalytic oxidation: ozone is introduced into the zinc sulfate solution after ferrous sulfate is added, and after the initial reaction, alkali is added to adjust the pH to 4.5-5.0, and then the reaction is continued to obtain a post-reaction solution.

[0032] In this process, the ozone introduced can oxidize the divalent iron ions, divalent manganese ions and monovalent thallium ions in the zinc sulfate solution, and convert these three ions into trivalent iron ions, high-valent manganese ions (+4, +7), and trivalent thallium ions, respectively. The trivalent iron ions are hydrolyzed into ferric hydroxide with adsorption in the subsequent process of adjusting the pH of the solution, while the high-valent manganese ions can oxidize the monovalent thallium ions into trivalent thallium ions and be reduced to divalent manganese ions at the same time. Then the divalent manganese ions undergo redox reaction with ozone again, and the cycle repeats, so that the divalent manganese ions play a catalytic role. The trivalent thallium ions are hydrolyzed into thallium hydroxide and co-precipitated with ferric hydroxide in the subsequent process. The reaction principles involved in this process are as follows:

[0033] Mn 2+ +O3+H2O=MnO2+O2+2H + (1)

[0034] 2Mn 2+ +5O3+3H2O=2MnO4 - +5O2+6H + (2)

[0035] 2MnO2+3O3+H2O=2MnO4 - +3O2+2H + (3)

[0036] MnO2+Tl + +4H + =Mn 2+ +Tl 3+ +2H2O (4)

[0037] 2MnO4 - +5Tl + +16H + =2Mn 2+ +5Tl 3+ +8H2O (5)

[0038] Tl + +O3+2H + =Tl 3+ +O2+H2O (6)

[0039] Tl 3+ +3OH - =Tl(OH)3↓ (7)

[0040] 2Fe 2+ +O3+2H + =2Fe 3+ +O2+H2O (8)

[0041] 2Fe 2+ +MnO2+4H + =2Fe 3+ +Mn 2+ +2H2O (9)

[0042] 3Fe 2+ +MnO4 - +4H + =3Fe 3+ +MnO2+2H2O (10)

[0043] Fe 3+ +3OH - =Fe(OH)3↓ (11)

[0044] When ozone is introduced into the zinc sulfate solution after adding ferrous sulfate, in order to promote the catalytic oxidation in the process to proceed smoothly and fully react, the temperature of the solution is controlled to 40-80°C and the concentration of ozone is controlled to 60-100 mg / L.

[0045] Furthermore, the amount of ozone introduced is controlled to be 10 to 40 ml of ozone per liter of solution per minute.

[0046] Moreover, in order to promote the catalytic oxidation after the introduction of ozone to proceed fully, the initial reaction time after the introduction of ozone is controlled to be 30 to 45 minutes. In order to promote the trivalent iron ions and trivalent thallium ions in the solution to fully form iron hydroxide precipitates and thallium hydroxide precipitates, respectively, and in order to enable the iron hydroxide precipitates and thallium hydroxide precipitates to fully co-precipitate, the reaction time after adding alkali to adjust the pH of the solution is controlled to be 45 to 60 minutes.

[0047] At the same time, in order to strengthen the transfer, mixing and reaction processes between ozone molecules and thallium ions and to improve the reaction efficiency of ozone and thallium ions, an explosion device is used to strengthen the mass transfer between ozone and solution after ozone is introduced into the zinc sulfate solution after ferrous sulfate is added.

[0048] The alkali used to adjust the pH value is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and sodium bicarbonate.

[0049] The alkali is added in the form of an alkali solution, and the mass concentration of the alkali solution is 10% to 20%.

[0050] Step 3) Flocculation precipitation: Adding beef glue to the solution after the reaction, stirring, standing, and filtering to obtain the zinc sulfate solution after thallium removal.

[0051] The temperature of the solution after the reaction is maintained at 40-80°C, the concentration of cow glue in the solution after the reaction is 0.5-2.0 g / L, and the cow glue is added in the form of a cow glue solution, which is a cow glue solution with a mass percentage concentration of 5-20% obtained by dissolving cow glue in water at 60-70°C.

[0052] Furthermore, after adding the beef glue to the solution after the reaction, the stirring time is 3 to 8 minutes and the standing time is 10 to 20 minutes.

[0053] The following is a detailed description of the method for removing thallium from a zinc sulfate solution provided by the present invention through examples.

[0054] Example 1

[0055] The present embodiment provides a method for removing thallium from a zinc sulfate solution, comprising the following steps:

[0056] (1) Pretreatment: The supernatant in the roasted sand was taken as the treatment object, which contained 1.2 mg / L thallium, 150 g / L zinc, 1.8 g / L manganese, 0.012 g / L iron, and pH = 5.0. 180 g / L of dilute sulfuric acid was added to adjust the pH to 2.5, and ferrous sulfate was added to make the total iron ion concentration reach 2 g / L;

[0057] (2) Catalytic oxidation: The temperature is 70°C, and ozone with a concentration of 70 mg / L is introduced into the pretreated solution. The ozone mass transfer between the ozone and the solution is enhanced by using an explosion device. The ozone dosage is 40 ml / min / L. 溶液 , the reaction time is 30 minutes, 10% sodium hydroxide is added to adjust the pH to 4.5, and the ozone is stopped after the reaction is continued for 50 minutes;

[0058] (3) Flocculation precipitation: Add 10% of beef glue to the solution after catalytic oxidation to make the dosage reach 1g / L, stir for 5 minutes, let it stand for 15 minutes, and filter to obtain the zinc sulfate solution after thallium removal.

[0059] The thallium content in the zinc sulfate solution after thallium removal obtained in this embodiment is detected to be 0.48 mg / L, so the thallium removal rate of this embodiment is 60%. The effective opening of thallium can be achieved, and the thallium content level of the entire smelting system is effectively reduced.

[0060] Example 2

[0061] This embodiment discloses a method for removing thallium from a zinc sulfate solution, comprising the following steps:

[0062] (1) Pretreatment: The supernatant in the roasted sand was taken as the treatment object, which contained 1.0 mg / L thallium, 148 g / L zinc, 1.9 g / L manganese, 0.015 g / L iron, and pH = 5.2. 185 g / L of dilute sulfuric acid was added to adjust the pH to 2.0, and ferrous sulfate was added to make the total iron ion concentration reach 1.5 g / L;

[0063] (2) Catalytic oxidation: The temperature is 65°C, and ozone with a concentration of 80 mg / L is introduced into the pretreated solution. The ozone and solution mass transfer is enhanced by an explosion device. The ozone dosage is 30 ml / min / L. 溶液 , the reaction time is 40 minutes, 15% sodium hydroxide is added to adjust the pH to 4.5, and the ozone is stopped after the reaction is continued for 45 minutes;

[0064] (3) Flocculation precipitation: Add 15% of beef glue to the solution after catalytic oxidation to make the dosage reach 1.5 g / L, stir for 6 minutes, let it stand for 10 minutes, and filter to obtain the zinc sulfate solution after thallium removal.

[0065] The thallium content in the zinc sulfate solution after thallium removal obtained in this embodiment is detected to be 0.5 mg / L, so the thallium removal rate of this embodiment is 50%. The effective opening of thallium can be achieved, and the thallium content level of the entire smelting system is effectively reduced.

[0066] Example 3

[0067] This embodiment discloses a method for removing thallium from a zinc sulfate solution, comprising the following steps:

[0068] (1) Pretreatment: Take roasted sand flushing liquid as the treatment object, which contains 0.5 mg / L thallium, 80 g / L zinc, 1.5 g / L manganese, and 1.6 g / L iron, and pH = 1.5. The pH meets the requirements and does not need to be adjusted. Ferrous sulfate is added to make the total iron ion concentration reach 2.0 g / L;

[0069] (2) Catalytic oxidation: The temperature is 80°C, and ozone with a concentration of 90 mg / L is introduced into the pretreated solution. The ozone and solution mass transfer is enhanced by an explosion device. The ozone dosage is 20 ml / min / L. 溶液 , the reaction time is 45min, 20% sodium hydroxide is added to adjust the pH to 5.0, and the ozone is stopped after the reaction is continued for 60min;

[0070] (3) Flocculation precipitation: Add 20% of beef glue to the solution after catalytic oxidation to make the dosage reach 1.5 g / L, stir for 5 minutes, let it stand for 15 minutes, and filter to obtain the zinc sulfate solution after thallium removal.

[0071] The thallium content in the zinc sulfate solution after thallium removal obtained in this embodiment is detected to be 0.22 mg / L, so the thallium removal rate of this embodiment is 56%. The effective opening of thallium can be achieved, and the thallium content level of the entire smelting system is effectively reduced.

[0072] Example 4

[0073] This embodiment discloses a method for removing thallium from a zinc sulfate solution, comprising the following steps:

[0074] (1) Pretreatment: Take roasted sand and neutrally leach 2 # The bath liquid is used as the treatment object, which contains 1.8 mg / L thallium, 145 g / L zinc, 2.0 g / L manganese, 0.8 g / L iron, and pH = 2.5. The pH meets the requirements and does not need to be adjusted. Ferrous sulfate is added to make the total iron ion concentration reach 2.0 g / L.

[0075] (2) Catalytic oxidation: The temperature is 70°C, and ozone with a concentration of 100 mg / L is introduced into the pretreated solution. The ozone and solution mass transfer is enhanced by an explosion device. The ozone dosage is 10 ml / min / L. 溶液 , the reaction time is 45min, 10% sodium hydroxide is added to adjust the pH to 5.0, and the ozone is stopped after the reaction is continued for 60min;

[0076] (3) Flocculation precipitation: Add 15% of beef glue to the solution after catalytic oxidation to make the dosage reach 2.0 g / L, stir for 3 minutes, let it stand for 15 minutes, and filter to obtain the zinc sulfate solution after thallium removal.

[0077] The thallium content in the zinc sulfate solution after thallium removal obtained in this embodiment is detected to be 0.75 mg / L, so the thallium removal rate of this embodiment is 58.3%. The effective opening of thallium can be achieved, and the thallium content level of the entire smelting system is effectively reduced.

[0078] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for removing thallium from a zinc sulfate solution, characterized in that: The steps include: Acid is added to adjust the pH of the zinc sulfate solution to ≤ 2.5, and then ferrous sulfate is added to make the iron ion concentration in the solution reach 1.5-2.0 g / L; Passing ozone into the zinc sulfate solution after adding ferrous sulfate, adding alkali to adjust the pH to 4.5-5.0 after the initial reaction, and then continuing the reaction to obtain a post-reaction solution; Add cow glue to the solution after the reaction, stir, let stand, and filter to obtain the zinc sulfate solution after thallium is removed.

2. The method for removing thallium from zinc sulfate solution according to claim 1, wherein: The zinc sulfate solution has a zinc ion concentration of 40-180 g / L, a total iron ion concentration of 0.01-1.5 g / L, a manganese ion concentration of 1.5-3.5 g / L, and a thallium ion concentration of not less than 0.8 mg / L.

3. The method for removing thallium from zinc sulfate solution according to claim 1, wherein: The acid added to adjust the pH of the zinc sulfate solution is dilute sulfuric acid or / and electrolytic waste liquid, and the concentrations of the dilute sulfuric acid and the electrolytic waste liquid are both 150-200 g / L.

4. The method for removing thallium from zinc sulfate solution according to claim 1, wherein: When ozone is introduced into the zinc sulfate solution after adding ferrous sulfate, the temperature of the solution is 40-80° C., the concentration of the ozone is 60-100 mg / L, and the amount of ozone introduced is 10-40 ml of ozone per minute per liter of solution.

5. The method for removing thallium from zinc sulfate solution according to claim 4, wherein: The initial reaction time after the introduction of ozone is 30 to 45 minutes, and the reaction time after the pH is adjusted by adding alkali is 45 to 60 minutes.

6. The method for removing thallium from zinc sulfate solution according to claim 5, wherein: After ozone is introduced into the zinc sulfate solution to which ferrous sulfate has been added, an explosion device is used to enhance the mass transfer between ozone and the solution.

7. The method for removing thallium from zinc sulfate solution according to claim 5, wherein: The alkali used for adjusting pH is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and sodium bicarbonate.

8. The method for removing thallium from zinc sulfate solution according to claim 7, wherein: The alkali is added in the form of an alkali solution, and the mass concentration of the alkali solution is 10% to 20%.

9. The method for removing thallium from zinc sulfate solution according to claim 1, wherein: The temperature of the solution after the reaction is maintained at 40-80°C, the concentration of cow glue in the solution after the reaction is 0.5-2.0 g / L, and the cow glue is added in the form of a cow glue solution, which is a cow glue solution with a mass percentage concentration of 5-20% obtained by dissolving cow glue in water at 60-70°C.

10. The method for removing thallium from zinc sulfate solution according to claim 1, characterized in that: After adding the cow glue to the reaction solution, the stirring time is 3 to 8 minutes and the standing time is 10 to 20 minutes.

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