Method for recovering thallium from sintering machine head ash

Abstract

The invention relates to a method for recovering thallium from sintering machine head ash, which comprises the following steps: 1) washing the sintering machine head ash by using acidic water, and carrying out solid-liquid separation to obtain low-salt filter residues and high-salt wastewater; (2) washing the low-salt filter residue obtained in the step (1) by using acidic water, and carrying out solid-liquid separation to obtain a filter cake and filtrate; and (3) adding chlorine salt into the filtrate obtained in the step (2) to carry out thallium precipitation reaction, and after the reaction is completed, carrying out solid-liquid separation to obtain thallium chloride and post-precipitation liquid. According to the method, a multi-stage washing method is adopted, the pH value in the washing process is controlled, the thallium ions are accurately separated from the sintering machine head ash, then through the same ion precipitation effect, the thallium chloride is precipitated, the thallium ions are recycled, the method is simple and easy to operate, and the obtained thallium chloride is high in purity. In addition, the trend of the filtrate is determined according to the concentration of thallium ions in the filtrate, the separation efficiency of thallium chloride and the recovery rate of thallium ions are improved, and the loss of thallium ions is prevented.

Description

Technical Field

[0001] The present invention relates to a method for recovering thallium, specifically to a method for recovering thallium from sintering machine head ash, belonging to the technical field of sintered solid waste treatment. Background Art

[0002] Thallium is a metal with active properties. It generally exists in the form of compounds and as a by - product, and has strong neurotoxicity, with its toxicity stronger than that of lead, cadmium, and mercury. The main compounds of thallium include oxides, sulfides, halides, sulfates, etc. Thallium salts are generally colorless, odorless crystals, which form thallium sub - compounds after dissolving in water and are relatively stable when stored in water or paraffin. Thallium is widely used in various fields such as electronics, military, aerospace, chemical industry, metallurgy, and communication, and has potential application value in aspects such as optical fibers, radiation scintillators, optical transmission positions, radiation shielding materials, catalysts, and superconducting materials.

[0003] Thallium in iron and steel enterprises mainly comes from iron ore. Under the high - temperature conditions of the sintering and blast furnace processes, it volatilizes into the dust, mainly distributed in the sintering machine head ash. According to statistics, about 50 - 70% of thallium will be enriched in the sintering machine head ash. Due to the high toxicity of thallium to the human body and the poor prognosis, etc., preventing thallium pollution is particularly important. At the same time, due to the wide application of thallium at present, the recovery of thallium has high economic benefits and importance.

[0004] Existing methods for disposing of thallium in sintering machine head ash mainly involve desalination by washing with water and then removing thallium from the washing liquid, such as Chinese Patent ZL202111464826.X "A Method and Treatment System for Co - treating Wet Flue Gas Desulfurization Wastewater and Sintering Ash", Chinese Patent ZL202210784214.7 "A Method for Removing Heavy Metals and Thallium from the Flushing Liquid of Sintering Machine Head Electrostatic Precipitation Ash", and Chinese Patent ZL202211085603.7 "A Multi - Sulfur - Based Heavy Metal Removal Agent and Its Preparation Method and Application". The above methods all focus on control from the perspective of thallium removal and do not achieve the recovery of thallium resources.

[0005] The components in the sintering machine head ash are relatively complex, with high iron, potassium, lead, and carbon contents. The main chemical components include substances such as Fe2O3, Fe3O4, CaO, C, SiO2, KCl, NaCl, and PbCl2. The output of sintering machine head ash accounts for about 2% - 4% of the sinter output, and the annual production of sintering machine head ash in the country is as high as about 15 million tons. Due to the complexity of the components of sintering machine head ash, there is currently no relatively mature thallium recovery method, resulting in a waste of thallium resources.

[0006] Therefore, there is an urgent need for a method that can effectively recover high - purity thallium from sintering machine head ash, realize the full utilization of sintering machine head ash, and avoid waste of resources. Summary of the Invention

[0007] In view of the problems in the prior art that the composition of sintering machine head ash is complex and thallium elements are not effectively recovered, the present invention proposes a method for recovering thallium from sintering machine head ash. According to the composition of the sintering machine head ash, it is washed in multiple stages, and the pH value of the solution in each washing process is adjusted to separate thallium ions from the sintering machine head ash, and then it is precipitated and separated to obtain high-purity thallium salt with a high recovery rate.

[0008] According to an embodiment of the present invention, a method for recovering thallium from sintering machine head ash is provided.

[0009] A method for recovering thallium from sintering machine head ash, the method comprising the following steps:

[0010] 1) Washing the sintering machine head ash with acidic water, and after solid-liquid separation, obtaining low-salt filter residue and high-salt wastewater;

[0011] 2) Washing the low-salt filter residue obtained in step 1) with acidic water, and after solid-liquid separation, obtaining a filter cake and a filtrate;

[0012] 3) Adding a chloride salt to the filtrate obtained in step 2) for thallium precipitation reaction, and after the reaction is completed, solid-liquid separation is carried out to obtain thallium chloride and a post-precipitation solution.

[0013] Preferably, the washing with acidic water in step 1) is to wash the sintering machine head ash with acidic water once or multiple times, preferably once.

[0014] Preferably, the washing of the low-salt filter residue with acidic water in step 2) is once or multiple times, preferably twice; preferably, the filtrate obtained from the first washing enters the thallium precipitation reaction in step 3), the filter cake obtained from the first washing is subjected to a second washing, and the washing liquid for the second washing is recycled to the first washing as the washing water for the low-salt filter residue; or, the washing liquid for the second washing is recycled to step 1) as the washing water for the sintering machine head ash.

[0015] Preferably, the pH of the high-salt wastewater in step 1) is 5-7, preferably 5.2-6.5, more preferably 5.4-6.0.

[0016] Preferably, in the low-salt filter residue obtained in step 1), the mass of chlorine is not higher than 4%-8%, preferably 5%-7%.

[0017] Preferably, the solid-liquid ratio of the sintering machine head ash to acidic water in step 1) is 0.25-1.5 g / mL, preferably 0.33-1 g / mL.

[0018] Preferably, the pH of the filtrate in step 2) is 3-5, preferably 3.2-4.5, more preferably 3.5-4.

[0019] Preferably, the acidic water described in steps 1) and 2) is one or more of dilute sulfuric acid, dilute nitric acid, and dilute hydrochloric acid, preferably dilute hydrochloric acid.

[0020] Preferably, the chloride salt described in step 3) is sodium chloride.

[0021] Preferably, the addition amount of the chloride salt described in step 3) is 6 - 12 g / L, preferably 7 - 10 g / L.

[0022] Preferably, the time for the thallium precipitation reaction described in step 3) is 10 - 40 min, preferably 20 - 30 min.

[0023] Preferably, step 1) is specifically: washing the sintering machine head ash with acidic water, with a solid - liquid ratio of 0.25 - 1.5 g / mL (preferably 0.33 - 1 g / mL), and after solid - liquid separation, obtaining low - salt filter residue and high - salt wastewater; among them, the mass of chlorine in the low - salt filter residue is not higher than 4% - 8% (preferably not higher than 5% - 7%). The pH of the high - salt wastewater is 5 - 7 (preferably 5.2 - 6.5).

[0024] Preferably, step 2) is specifically: washing the low - salt filter residue obtained in step 1) with acidic water, and after solid - liquid separation, obtaining a filter cake and a filtrate; among them, the pH of the filtrate is 3 - 5 (preferably 3.2 - 4.5); the acid - water washing is carried out twice. The filtrate obtained from the first washing enters the thallium precipitation process of step 3). The filter cake obtained from the first water washing is subjected to the second washing, and the washing liquid from the second washing is recycled to the first washing as the washing water for the low - salt filter residue.

[0025] Preferably, step 3) is specifically: adding sodium chloride to the filtrate obtained in step 2) for thallium precipitation reaction, with an addition amount of 6 - 12 g / L (preferably 7 - 10 g / L), and after reacting for 10 - 40 min (preferably 20 - 30 min), performing solid - liquid separation to obtain thallous chloride and a post - precipitation liquid.

[0026] Preferably, the method further includes: 2a) detecting the concentration of thallium ions in the filtrate obtained in step 2). When the thallium ion concentration is not higher than the set value, the filtrate is recycled to step 1) as the washing water for the sintering machine head ash; when the thallium ion concentration is higher than the set value, the filtrate enters the thallium precipitation process of step 3).

[0027] Preferably, the method further includes: 4) adjusting the post - precipitation liquid obtained in step 3) to be alkaline for precipitation reaction, and after the reaction is completed, filtering to obtain a copper - containing precipitate and a residual liquid; the residual liquid is recycled to step 1) as the washing water for the sintering machine head ash.

[0028] Preferably, the set value in step 2a) is that the thallium ion concentration is greater than 1 g / L, preferably greater than 1.5 g / L.

[0029] Preferably, the reagent used to adjust the post-precipitation solution to alkaline in step 4) is one or two of sodium hydroxide and potassium hydroxide, preferably sodium hydroxide.

[0030] Preferably, the alkalinity in step 4) is a pH value of 8 - 10, preferably 8.5 - 9.5.

[0031] Preferably, the time for the precipitation reaction in step 4) is 10 - 40 min, preferably 20 - 30 min.

[0032] Preferably, the main component of the copper-containing precipitate in step 4) is copper hydroxide.

[0033] Preferably, step 2a) is specifically: detecting the thallium ion concentration in the filtrate obtained in step 2), when the thallium ion concentration is not higher than 1 g / L (preferably 1.5 g / L), returning the obtained filtrate to step 1) as the washing water for the sintering machine head ash, when the thallium ion concentration is higher than 1 g / L (preferably 1.5 g / L), the secondary water washing solution enters the thallium precipitation process in step 3).

[0034] Preferably, step 4) is specifically: adjusting the pH of the post-precipitation solution obtained in step 3) to 8 - 10 (preferably 8.5 - 9.5) with sodium hydroxide, after the solution reacts for 10 - 40 min (preferably 20 - 30 min), performing solid-liquid separation to obtain a copper-containing precipitate and a residual liquid; recycling the residual liquid to step 1) as the washing water for the sintering machine head ash.

[0035] In the present invention, it is found that during the dissolution process of sintering machine head ash, under the condition of weak acidic and high salt, the dissolution amount of thallium is relatively low. Since salts are easily soluble, regardless of the pH value of the solution, all salt ions will enter the washing liquid, maintaining a high salt system. According to the above principle, the present invention adopts a multi-stage washing method. Since the sintering machine head ash is alkaline, acidic water is used to wash it. During the washing process, the pH of the solution is adjusted to separate thallium from the sintering machine head ash. Specifically, first, the sintering machine head ash is washed with acidic water. During the washing process, the pH of the solution is controlled to be 5 - 7. A large amount of salt ions in the solution can reduce the precipitation of thallium ions from the sintering machine head ash. The salt ions enter the high-salt wastewater, and the thallium ions enter the low-salt filter residue. According to experiments, when the sintering machine head ash is placed in a solution with a weak acid and near-neutral condition, the dissolution amount of thallium can be reduced by 85% - 95%. On the basis of the acidic water washing, the low-salt filter residue obtained by washing is subjected to acidic washing. 90% of the thallium in the sintering machine head ash is acid-soluble. At the same time, the sintering machine head ash contains a large amount of iron. According to experiments, by adjusting the pH of the filtrate to 3 - 5, it is possible to avoid incomplete dissolution of thallium ions, realize the dissolution of thallium from the low-salt filter residue and enter the filtrate, while iron will not dissolve and remains in the filter cake.

[0036] In the present invention, a chloride salt is added to the solution containing thallium chloride (i.e., the filtrate) to produce a common ion precipitation effect with the thallium ions in the filtrate, converting thallium chloride into a precipitate. In addition, during the acidic water washing process in step 2), in addition to the dissolution of thallium from the low-salt filter residue, a small amount of copper ions will also dissolve. Therefore, after the thallium is precipitated, the post-precipitation solution is adjusted to alkaline, and a relatively high-purity copper hydroxide precipitate can be recovered. Preferably, when the concentration of thallium ions in the filtrate is insufficient, there may be a phenomenon that thallium ions cannot be completely precipitated, resulting in the loss of thallium ions. In the present invention, by detecting the concentration of thallium ions in the filtrate, when the concentration of thallium ions is lower than the set value, the filtrate is returned to the acidic water washing process in step 1); when the concentration of thallium ions in the filtrate reaches the set value, a chloride salt is added to it to form a thallium chloride precipitate, improving the recovery rate of thallium ions.

[0037] In the present invention, in combination with the properties of the sintering machine head ash, by controlling the pH value of the solution during the acidic washing processes in step 1) and step 2), thallium ions are accurately separated from the sintering machine head ash, and through the common ion precipitation effect, thallium chloride is converted into a precipitate to complete the recovery of thallium ions. At the same time, to prevent the concentration of thallium ions from being too low, resulting in poor precipitation effect, by detecting the concentration of thallium ions in the filtrate and determining the direction of the filtrate according to the set value, the efficiency of the precipitation process and the recovery rate of thallium ions are improved, and the loss of thallium ions is prevented.

[0038] In the present invention, the acid washing processes in steps 1) and 2) can both be set as multi-stage washing. Among them, the acid washing in step 2) is preferably two-stage washing to further separate the thallium ions in the filter cake, and the washing liquid obtained from the second washing is recycled to the first washing process to improve the recovery rate of thallium ions.

[0039] In the present invention, hydrochloric acid can also be added during the acid washing process to control the pH value of the solution, provide a certain concentration of chloride ions, and prevent the oxidation of monovalent Tl.

[0040] In the present invention, the solid-liquid separation can be carried out by means such as centrifugation, pressure filtration, vacuum separation, etc.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. A method for recovering thallium from sintering machine head ash provided by the present invention adopts a multi-stage washing method and controls the pH value of the solution during washing to accurately separate thallium ions from sintering machine head ash, and then through the co-ion precipitation effect, thallous chloride is precipitated to complete the recovery of thallium ions. The method is simple and easy to operate, and the obtained thallous chloride has high purity.

[0043] 2. A method for recovering thallium from sintering machine head ash provided by the present invention determines the flow direction of the filtrate according to the concentration of thallium ions in the filtrate, improves the precipitation efficiency of thallous chloride and the recovery rate of thallium ions, and prevents the loss of thallium ions.

[0044] 3. A method for recovering thallium from sintering machine head ash provided by the present invention sets the acid water washing step as multiple washings to further precipitate thallium ions from the filter cake and improve the recovery rate of thallium ions. Brief Description of the Drawings

[0045] Figure 1 It is a flowchart of a method for recovering thallium from sintering machine head ash provided by the present invention. Detailed Embodiments

[0046] The technical solutions of the present invention are illustrated below by examples. The scope claimed by the present invention includes but is not limited to the following examples.

[0047] According to the embodiments of the present invention, a method for recovering thallium from sintering machine head ash is provided.

[0048] A method for recovering thallium from sintering machine head ash, the method comprising the following steps:

[0049] 1) Wash the sintering machine head ash with acid water, and after solid-liquid separation, obtain a low-salt filter residue and high-salt wastewater;

[0050] 2) Wash the low-salt filter residue obtained in step 1) with acidic water, and after solid-liquid separation, obtain a filter cake and a filtrate.

[0051] 3) Add a chloride salt to the filtrate obtained in step 2) for thallium precipitation reaction. After the reaction is completed, solid-liquid separation is carried out to obtain thallium chloride and a post-precipitation liquid.

[0052] Preferably, the washing with acidic water in step 1) is to wash the sintering machine head ash with acidic water once or multiple times, preferably once.

[0053] Preferably, the washing of the low-salt filter residue with acidic water in step 2) is once or multiple times, preferably twice; as an option, the filtrate obtained from the first washing enters the thallium precipitation reaction in step 3), the filter cake obtained from the first washing is subjected to a second washing, and the washing liquid from the second washing is recycled to the first washing as the washing water for the low-salt filter residue; or, the washing liquid from the second washing is recycled to step 1) as the washing water for the sintering machine head ash.

[0054] Preferably, the pH of the high-salt wastewater in step 1) is 5 - 7, preferably 5.2 - 6.5, more preferably 5.4 - 6.0.

[0055] Preferably, in the low-salt filter residue obtained in step 1), the mass of chlorine is not higher than 4% - 8%, preferably 5% - 7%.

[0056] Preferably, the solid-liquid ratio of the sintering machine head ash to the acidic water in step 1) is 0.25 - 1.5 g / mL, preferably 0.33 - 1 g / mL.

[0057] Preferably, the pH of the filtrate in step 2) is 3 - 5, preferably 3.2 - 4.5, more preferably 3.5 - 4.

[0058] Preferably, the acidic water in steps 1) and 2) is one or more of dilute sulfuric acid, dilute nitric acid, and dilute hydrochloric acid, preferably dilute hydrochloric acid.

[0059] Preferably, the chloride salt in step 3) is sodium chloride.

[0060] Preferably, the addition amount of the chloride salt in step 3) is 6 - 12 g / L, preferably 7 - 10 g / L.

[0061] Preferably, the time of the thallium precipitation reaction in step 3) is 10 - 40 min, preferably 20 - 30 min.

[0062] Preferably, step 1) is specifically as follows: The sintering machine head ash is washed with acidic water, and the solid-liquid ratio is 0.25 - 1.5 g / mL (preferably 0.33 - 1 g / mL). After solid-liquid separation, low-salt filter residue and high-salt wastewater are obtained. Among them, the mass of chlorine in the low-salt filter residue is not higher than 4% - 8% (preferably not higher than 5% - 7%). The pH of the high-salt wastewater is 5 - 7 (preferably 5.2 - 6.5).

[0063] Preferably, step 2) is specifically as follows: The low-salt filter residue obtained in step 1) is washed with acidic water, and after solid-liquid separation, a filter cake and a filtrate are obtained. Among them, the pH of the filtrate is 3 - 5 (preferably 3.2 - 4.5); the acid water washing is carried out twice. The filtrate obtained from the first washing enters the thallium precipitation process in step 3). The filter cake obtained from the first water washing is subjected to the second washing, and the washing liquid from the second washing is recycled to the first washing as the washing water for the low-salt filter residue.

[0064] Preferably, step 3) is specifically as follows: Sodium chloride is added to the filtrate obtained in step 2) for thallium precipitation reaction, and the addition amount is 6 - 12 g / L (preferably 7 - 10 g / L). After reacting for 10 - 40 min (preferably 20 - 30 min), solid-liquid separation is carried out to obtain thallous chloride and a post-precipitation liquid.

[0065] Preferably, the method further includes: 2a) Detecting the concentration of thallium ions in the filtrate obtained in step 2). When the thallium ion concentration is not higher than the set value, the filtrate is recycled to step 1) as the washing water for the sintering machine head ash; when the thallium ion concentration is higher than the set value, the filtrate enters the thallium precipitation process in step 3).

[0066] Preferably, the method further includes: 4) Adjusting the post-precipitation liquid obtained in step 3) to be alkaline for precipitation reaction. After the reaction is completed, a copper-containing precipitate and a residual liquid are obtained through filtration; the residual liquid is recycled to step 1) as the washing water for the sintering machine head ash.

[0067] Preferably, the set value in step 2a) is that the thallium ion concentration is greater than 1 g / L, preferably the thallium ion concentration is greater than 1.5 g / L.

[0068] Preferably, the reagent used to adjust the post-precipitation liquid to be alkaline in step 4) is one or two of sodium hydroxide and potassium hydroxide, preferably sodium hydroxide.

[0069] Preferably, the alkalinity in step 4) is a pH value of 8 - 10, preferably 8.5 - 9.5.

[0070] Preferably, the time for the precipitation reaction in step 4) is 10 - 40 min, preferably 20 - 30 min.

[0071] Preferably, the main component of the copper-containing precipitate in step 4) is copper hydroxide.

[0072] Preferably, step 2a) is specifically as follows: detecting the concentration of thallium ions in the filtrate obtained in step 2), when the thallium ion concentration is not higher than 1 g / L (preferably 1.5 g / L), returning the obtained filtrate to step 1) as the washing water for the sintering machine head ash, and when the thallium ion concentration is higher than 1 g / L (preferably 1.5 g / L), the secondary washing liquid enters the thallium precipitation process in step 3).

[0073] Preferably, step 4) is specifically as follows: adjusting the pH of the post-precipitation liquid obtained in step 3) to 8-10 (preferably 8.5-9.5) with sodium hydroxide, waiting for 10-40 min (preferably 20-30 min) for the solution to react, and then performing solid-liquid separation to obtain a copper-containing precipitate and a residual liquid; recycling the residual liquid to step 1) as the washing water for the sintering machine head ash.

[0074] Example 1

[0075] A method for recovering thallium from sintering machine head ash:

[0076] 1) Wash 3 kg of sintering machine head ash with 4 L of dilute hydrochloric acid with a pH of 3, and then perform solid-liquid separation to obtain 2.33 kg of low-salt filter residue and 3.6 L of high-salt wastewater; among them, the mass of chlorine in the low-salt filter residue is detected to be 6.1%, and the pH of the high-salt wastewater is 5.8.

[0077] 2) Wash the 2.33 kg of low-salt filter residue obtained in step 1) twice with dilute hydrochloric acid with a pH of 3. The solid-liquid ratio of the first washing is 1.18 g / mL, and then solid-liquid separation is performed to obtain 2.03 kg of filter cake and 1.95 L of filtrate. The 2.03 kg of filter cake is washed a second time, and the solid-liquid ratio of the second washing is 1.07 g / mL. The washing liquid obtained from the second water washing is recycled to the first washing as the washing water for the low-salt filter residue; among them, the pH of the filtrate is 3.7.

[0078] 2a) The concentration of thallium ions in the obtained filtrate is detected to be 1.8 g / L.

[0079] 3) Add 15.6 g of sodium chloride to the 1.95 L of filtrate obtained in step 2), react for 0.5 h, and then perform solid-liquid separation to obtain 2.29 g of thallium chloride and 1.95 L of post-precipitation liquid.

[0080] 4) Adjust the pH of the 1.95 L of post-precipitation liquid obtained in step 3) to 9 with sodium hydroxide, wait for 0.5 h, and then perform solid-liquid separation to obtain 11.8 g of copper-containing precipitate and 1.95 L of residual liquid. The residual liquid is recycled to step 1) as the washing water for the sintering machine head ash.

[0081] The detected purity of thallium(I) chloride is 96.1%, and the purity of copper hydroxide is 91.7%.

[0082] Using the same method as in Example 1, adjust the addition amount of dilute hydrochloric acid in step 1) and the addition amount of dilute hydrochloric acid in step 2), control the pH values of the high-salt wastewater and the filtrate, and conduct parallel experiments. The specific conditions are shown in Table 1.

[0083] Table 1

[0084]

[0085]

[0086] Detect the mass and purity of thallium(I) chloride obtained in Examples 1 to 17, and the results are shown in Table 2.

[0087] Table 2

[0088]

[0089] According to Examples 1 to 17, it can be concluded that by controlling the pH value of the solution during the washing process, thallium ions can be accurately separated from the sintering machine head ash, and thallium(I) chloride can be precipitated through the common-ion precipitation effect. Then, by adjusting the pH, copper-containing precipitate can be obtained to complete the recovery of thallium ions and copper ions. The obtained thallium(I) chloride and copper hydroxide have high yields and purities.

Claims

1. A method for recovering thallium from sintering machine head ash, characterized in that: The method includes the following steps: 1) Washing the sintering machine head ash with acidic water, and obtaining low-salt filter residue and high-salt wastewater after solid-liquid separation; 2) Washing the low-salt filter residue obtained in step 1) with acidic water, and obtaining filter cake and filtrate after solid-liquid separation; 3) Adding chloride salt to the filtrate obtained in step 2) for thallium precipitation reaction, and obtaining thallous chloride and post-precipitation liquid after solid-liquid separation after the reaction is completed.

2. The method according to claim 1, wherein: The washing with acidic water in step 1) is one-time washing or multiple washings of the sintering machine head ash with acidic water, preferably one-time washing; and / or The washing of the low-salt filter residue with acidic water in step 2) is one-time washing or multiple washings, preferably two-time washings; Preferably, the filtrate obtained from the first washing enters the thallium precipitation reaction in step 3), the filter cake obtained from the first washing is subjected to the second washing, and the washing liquid from the second washing is recycled to the first washing as the washing water for the low-salt filter residue; Or, the washing liquid from the second washing is recycled to step 1) as the washing water for the sintering machine head ash.

3. The method according to claim 1 or 2, characterized in that: The pH of the high-salt wastewater in step 1) is 5-7, preferably 5.2-6.5, more preferably 5.4-6.0; and / or In the low-salt filter residue obtained in step 1), the mass of chlorine is not higher than 4%-8%, preferably 5%-7%; and / or The solid-liquid ratio of the sintering machine head ash to the acidic water in step 1) is 0.25-1.5 g / mL, preferably 0.33-1 g / mL.

4. The method according to any one of claims 1 to 3, characterized in that: The pH of the filtrate in step 2) is 3-5, preferably 3.2-4.5, more preferably 3.5-4; and / or The acidic water in steps 1) and 2) is one or more of dilute sulfuric acid, dilute nitric acid, and dilute hydrochloric acid, preferably dilute hydrochloric acid; and / or The chloride salt in step 3) is sodium chloride; and / or The addition amount of the chloride salt in step 3) is 6-12 g / L, preferably 7-10 g / L; and / or The time of the thallium precipitation reaction in step 3) is 10-40 min, preferably 20-30 min.

5. The method according to any one of claims 1 to 4, characterized in that: Specifically, step 1) is: washing the sintering machine head ash with acidic water, with a solid-liquid ratio of 0.25-1.5 g / mL (preferably 0.33-1 g / mL), and obtaining low-salt filter residue and high-salt wastewater after solid-liquid separation; wherein, the mass of chlorine in the low-salt filter residue is not higher than 4%-8% (preferably not higher than 5%-7%); the pH of the high-salt wastewater is 5-7 (preferably 5.2-6.5); and / or Specifically, step 2) is: washing the low-salt filter residue obtained in step 1) with acidic water, and obtaining filter cake and filtrate after solid-liquid separation; wherein, the pH of the filtrate is 3-5 (preferably 3.2-4.5); the acidic water washing is two-time washing, the filtrate obtained from the first water washing enters the thallium precipitation process in step 3), the filter cake obtained from the first washing is subjected to the second washing, and the washing liquid from the second washing is recycled to the first washing as the washing water for the low-salt filter residue; and / or Step 3) specifically includes: adding sodium chloride to the filtrate obtained in Step 2) for thallium precipitation reaction, with the addition amount being 6 - 12 g / L (preferably 7 - 10 g / L), reacting for 10 - 40 min (preferably 20 - 30 min), and then performing solid-liquid separation to obtain thallous chloride and the post-precipitation liquid.

6. The method according to any one of claims 1-5, characterized in that: This method further includes: 2a) Detecting the concentration of thallium ions in the filtrate obtained in Step 2). When the thallium ion concentration is not higher than the set value, the filtrate is recycled to Step 1) as the washing water for the sintering machine head ash; when the thallium ion concentration is higher than the set value, the filtrate enters the thallium precipitation process in Step 3); and / or 4) Adjusting the post-precipitation liquid obtained in Step 3) to be alkaline for precipitation reaction. After the reaction is completed, copper-containing precipitate and residual liquid are obtained through filtration; the residual liquid is recycled to Step 1) as the washing water for the sintering machine head ash.

7. The method according to claim 6, wherein: The set value described in Step 2a) is that the thallium ion concentration is greater than 1 g / L, preferably the thallium ion concentration is greater than 1.5 g / L.

8. The method according to claim 6 or 7, characterized in that: The reagent used to adjust the post-precipitation liquid to be alkaline in Step 4) is one or both of sodium hydroxide and potassium hydroxide, preferably sodium hydroxide; and / or The alkalinity in Step 4) is a pH value of 8 - 10, preferably 8.5 - 9.5; and / or The time for the precipitation reaction in Step 4) is 10 - 40 min, preferably 20 - 30 min; and / or The main component of the copper-containing precipitate in Step 4) is copper hydroxide.

9. The method according to any one of claims 6 - 8, characterized in that: Step 2a) specifically includes: detecting the concentration of thallium ions in the filtrate obtained in Step 2). When the thallium ion concentration is not higher than 1 g / L (preferably 1.5 g / L), the obtained filtrate is returned to Step 1) as the washing water for the sintering machine head ash. When the thallium ion concentration is higher than 1 g / L (preferably 1.5 g / L), the secondary washing liquid enters the thallium precipitation process in Step 3).

10. The method according to any one of claims 6-9, characterized in that: Step 4) specifically includes: adjusting the pH of the post-precipitation liquid obtained in Step 3) to 8 - 10 (preferably 8.5 - 9.5) with sodium hydroxide. After the solution reacts for 10 - 40 min (preferably 20 - 30 min), solid-liquid separation is performed to obtain copper-containing precipitate and residual liquid; the residual liquid is recycled to Step 1) as the washing water for the sintering machine head ash.

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