A method for recovering thallium metal from lead-zinc smelting acidic wastewater

Abstract

This invention relates to the field of lead-zinc smelting technology, and its purpose is to provide a method for recovering thallium metal from lead-zinc smelting wastewater. The invention involves adjusting the wastewater, adding lime slurry and biological agents, reacting to obtain zinc slag, and then subjecting the supernatant to secondary thickening and sulfidation reactions to obtain underflow and supernatant. The supernatant is pressure filtered to obtain sulfided thallium slag, and the filtrate is returned to the mineral processing system for reuse. Simultaneously, the underflow from primary and secondary thickening is concentrated to obtain supernatant, which is returned to the equalization tank for reuse. The underflow is then pressure filtered again to obtain sludge, and the filtrate is returned to the thickening tank. The process flow of this invention is practical and reliable, simple and safe to operate, and the lime slurry and biological agents added during production are readily available. This invention has strong thallium and zinc removal capabilities, with thallium removal reaching up to 99% and zinc removal reaching up to 98%, realizing the transformation of thallium metal from waste into a valuable resource.

Description

Technical Field

[0001] This invention belongs to the field of lead-zinc smelting technology, specifically relating to a method for recovering thallium metal from lead-zinc smelting wastewater. Background Technology

[0002] A lead-zinc smelter in Gansu Province mainly produces electrolytic lead, refined zinc, refined cadmium, crude copper, industrial sulfuric acid, and lead anode mud. The company mainly uses mixed lead-zinc ore as raw material and adopts a pyrometallurgical process. The wastewater generated from flue gas scrubbing contains high levels of metal ions such as thallium and zinc. In the company's initial wastewater treatment process, there was no process route designed to treat and recover thallium.

[0003] In recent years, with increasingly stringent national environmental protection policies and industry-specific limits on metal emissions, the current "lime + iron salt" treatment process used by enterprises is insufficient to meet emission standards for metal content in wastewater or achieve metal recovery. Therefore, to reduce the emission of metal ions, especially thallium, improve the environmental quality near the plant, meet new environmental governance concepts, and better achieve compliance, reduction, and resource recovery of wastewater, this invention proposes a novel process route for treatment that ensures compliant discharge and resource recovery, eliminates potential metal pollution risks, achieves stable compliance with thallium standards in wastewater, and enables the resource reuse of thallium during the treatment process. Summary of the Invention

[0004] The purpose of this invention is to provide a method for recovering thallium metal from lead-zinc smelting wastewater, in order to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for recovering thallium metal from lead-zinc smelting wastewater includes the following steps:

[0007] Step 1: The acid wastewater first enters the equalization tank, where compressed air is introduced for mechanical stirring to homogenize the acid wastewater, causing the sludge to initially settle and then enter the sludge thickening tank.

[0008] Step 2: Pump the supernatant obtained in Step 1 into the primary integrated reaction tank, add lime slurry to adjust the pH, and after reacting for 15 minutes, the pH rises from 4 to 8.

[0009] Step 3: The acidic wastewater obtained in Step 2 flows into the zinc removal tank by gravity. Add biological agent to the zinc removal tank at a ratio of 1 kg of biological agent per cubic meter of water. After reacting for 15 minutes, the pH rises to 9, removing heavy metals such as zinc, lead, copper, and cadmium from the acidic wastewater.

[0010] Step 4: The supernatant obtained in Step 3 enters the primary thickener for sedimentation for 4 hours to perform solid-liquid separation. The underflow with a solid content of 55% enters the sludge thickening tank.

[0011] Step 5: The supernatant obtained in Step 4 enters the sulfidation reactor. The upper gas space is kept under slight negative pressure. Hydrogen sulfide of 55% or more is introduced into the lower liquid and reacted for 20 minutes. The waste gas generated by the sulfidation reaction is treated with magnesium oxide and discharged in compliance with standards. The salt solution is returned to the company's wastewater treatment system.

[0012] Step 6: The supernatant obtained in Step 5 flows into the secondary thickener by gravity. The secondary thickener settles for 4 hours to separate solids and liquids. The underflow with a solid content of 98% enters the sludge thickening tank.

[0013] Step 7: The supernatant obtained in Step 6 is pumped into a chamber filter press with a feed pressure ≥0.4 MPa. After filtration, thallium sulfide slag is obtained, and the filtrate is reused in the mineral processing system.

[0014] Step 8: Pump the supernatant from the sludge thickening tank back to the equalization tank, and pump the underflow from the sludge thickening tank into a chamber filter press with a feed pressure ≥0.4Mpa. After filtration, filter residue sludge is obtained, and the filtrate is reused in the thickening tank.

[0015] The thallium content in the acidic wastewater in step 1 is 70 mg / L.

[0016] The moisture content of the thallium sulfide slag obtained in step 7 is 60%.

[0017] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0018] This invention involves adjusting acidic wastewater, adding lime slurry and biological agents, reacting to produce zinc slag, and then subjecting the supernatant to secondary thickening and sulfidation to produce underflow and supernatant. The supernatant is then pressure filtered to obtain thallium sulfide slag, and the filtrate is returned to the mineral processing system for reuse. Simultaneously, the underflow from primary and secondary thickening is concentrated to obtain supernatant, which is returned to the equalization tank for reuse. The underflow is then pressure filtered again to obtain sludge, and the filtrate is returned to the thickening tank. The process flow of this invention is practical and reliable, simple and safe to operate, and the lime slurry and biological agents added during production are readily available. This invention has strong thallium and zinc removal capabilities, with thallium removal reaching up to 99% and zinc removal reaching up to 98%, realizing the transformation of thallium metal from waste into valuable resources. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the process flow of the present invention. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0022] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0023] Example 1

[0024] In January 2020, the chemical analysis of the main metal components of the acidic wastewater generated from flue gas scrubbing at a lead-zinc smelter in Gansu Province is shown in Table 1.

[0025] Table 1. Main Metal Components of Sludge Wastewater

[0026] name Cu Zn Pb Cd As Tl(μg / L) raw water sample 0.12 26.96 11.86 35.94 15.26 6960 Special Standards for Lead and Zinc Industry 0.5 1.5 0.5 0.05 0.3 5

[0027] The acidic wastewater first enters the equalization tank, where compressed air is introduced for mechanical stirring to homogenize it. The wastewater from the equalization tank then enters the primary integrated reaction tank, where lime slurry is added for pH adjustment. After 15 minutes of reaction, the pH rises from 4 to 8. The wastewater from the primary integrated reaction tank then flows by gravity into the zinc removal tank. Biological agents are added to the zinc removal tank at a ratio of 1 kg of biological agent per cubic meter of water. After 15 minutes of reaction, the pH rises to 9, removing heavy metals such as zinc, lead, copper, and cadmium from the wastewater. The wastewater from the zinc removal tank then enters the primary thickener for sedimentation for 4 hours to achieve solid-liquid separation. The supernatant from the primary thickener enters the sulfidation reactor. A slight negative pressure is maintained in the upper gas space, and hydrogen sulfide (55% or higher) is introduced into the lower liquid for a 20-minute reaction. The supernatant from the sulfidation reactor then flows by gravity into the secondary thickener, where sedimentation lasts for 4 hours to achieve solid-liquid separation. The supernatant from the secondary thickener is pumped into a chamber filter press with a feed pressure ≥0.4 MPa. After filtration, thallium sulfide slag (60% water content) is obtained, and the filtrate is reused in the mineral processing system. After the above production process is completed, the wastewater is chemically analyzed, and the results are shown in Table 2.

[0028] Table 2 Main Metal Components of Sludge Wastewater

[0029] name Cu Zn Pb Cd As Tl(μg / L) Purified water sample 3 0.012 — 0.01 0.03 0.34 67 Special Standards for Lead and Zinc Industry 0.5 1.5 0.5 0.05 0.3 5

[0030] The production data shows that the thallium content of the original water sample was 6960 μg / L. After treatment using the method of this invention, the thallium content was reduced to 67 μg / L, and the thallium removal efficiency reached over 99%.

[0031] Example 2

[0032] In February 2020, the chemical analysis of the main metal components of the acidic wastewater generated from flue gas scrubbing at a lead-zinc smelter in Gansu Province is shown in Table 3.

[0033] Table 3 Main Metal Components of Sludge Acid Wastewater

[0034] name Cu Zn Pb Cd As Tl(μg / L) raw water sample 0.13 27.13 11.15 36.83 15.86 6850 Special Standards for Lead and Zinc Industry 0.5 1.5 0.5 0.05 0.3 5

[0035] The acidic wastewater first enters the equalization tank, where compressed air is introduced for mechanical stirring to homogenize it. The wastewater from the equalization tank then enters the primary integrated reaction tank, where lime slurry is added for pH adjustment. After 15 minutes of reaction, the pH rises from 4 to 8. The wastewater from the primary integrated reaction tank then flows by gravity into the zinc removal tank. Biological agents are added to the zinc removal tank at a ratio of 1 kg of biological agent per cubic meter of water. After 15 minutes of reaction, the pH rises to 9, removing heavy metals such as zinc, lead, copper, and cadmium from the wastewater. The wastewater from the zinc removal tank then enters the primary thickener for sedimentation for 4 hours to achieve solid-liquid separation. The supernatant from the primary thickener enters the sulfidation reactor. A slight negative pressure is maintained in the upper gas space, and hydrogen sulfide (55% or higher) is introduced into the lower liquid for a 20-minute reaction. The supernatant from the sulfidation reactor then flows by gravity into the secondary thickener, where sedimentation lasts for 4 hours to achieve solid-liquid separation. The supernatant from the secondary thickener is pumped into a chamber filter press with a feed pressure ≥0.4 MPa. After filtration, thallium sulfide slag (60% water content) is obtained, and the filtrate is reused in the mineral processing system. After the above production process is completed, the wastewater is chemically analyzed, and the results are shown in Table 4.

[0036] Table 4. Main Metal Components of Sludge Acid Wastewater

[0037] name Cu Zn Pb Cd As Tl(μg / L) Purified water sample 3 0.011 — 0.01 0.02 0.32 65 Special Standards for Lead and Zinc Industry 0.5 1.5 0.5 0.05 0.3 5

[0038] The production data shows that the thallium metal content of the original water sample was 6850 μg / L. After treatment using the method of this invention, the thallium metal content was reduced to 65 μg / L, and the thallium removal efficiency reached over 99%.

Claims

1. A method for recovering thallium metal from acidic wastewater in lead-zinc smelting, characterized in that, Includes the following steps: Step 1: The acid wastewater first enters the equalization tank, where compressed air is introduced for mechanical stirring to homogenize the acid wastewater, causing the sludge to initially settle and then enter the sludge thickening tank. Step 2: Pump the supernatant obtained in Step 1 into the primary integrated reaction tank, add lime slurry to adjust the pH, and after reacting for 15 minutes, the pH rises from 4 to 8. Step 3: The acidic wastewater obtained in Step 2 flows into the zinc removal tank by gravity. Add biological agent to the zinc removal tank at a ratio of 1 kg of biological agent per cubic meter of water. After reacting for 15 minutes, the pH rises to 9, removing heavy metals such as zinc, lead, copper, and cadmium from the acidic wastewater. Step 4: The supernatant obtained in Step 3 enters the primary thickener for sedimentation for 4 hours to perform solid-liquid separation. The underflow with a solid content of 55% enters the sludge thickening tank. Step 5: The supernatant obtained in Step 4 enters the sulfidation reactor. The upper gas space is kept under slight negative pressure. Hydrogen sulfide of 55% or more is introduced into the lower liquid and reacted for 20 minutes. The waste gas generated by the sulfidation reaction is treated with magnesium oxide and discharged in compliance with standards. The salt solution is returned to the company's wastewater treatment system. Step 6: The supernatant obtained in Step 5 flows into the secondary thickener by gravity. The secondary thickener settles for 4 hours to separate solids and liquids. The underflow with a solid content of 98% enters the sludge thickening tank. Step 7: The supernatant obtained in Step 6 is pumped into a chamber filter press with a feed pressure ≥0.4 MPa. After filtration, thallium sulfide slag is obtained, and the filtrate is reused in the mineral processing system. Step 8: Pump the supernatant from the sludge thickening tank back to the equalization tank, and pump the underflow from the sludge thickening tank into a chamber filter press with a feed pressure ≥0.4Mpa. After filtration, filter residue sludge is obtained, and the filtrate is reused in the thickening tank. The thallium content in the acidic wastewater in step 1 is 70 mg / L; The moisture content of the thallium sulfide slag obtained in step 7 is 60%.

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