A tailings treatment process for hydrometallurgical zinc smelting

Abstract

This invention provides a process for treating tailings from hydrometallurgical zinc smelting, specifically for processing tailings after activation roasting, acid leaching, and chloride leaching. Acid leaching is performed using a sulfuric acid solution of a specific concentration and dosage, with the addition of metal fluorides to further enhance the metal leaching effect. Under the experimental conditions of this invention, the As content in the treated tailings is reduced to ≤0.1%, meeting general solid waste requirements; furthermore, the used acid leaching solution contains few impurities, is easy to recycle, and can be reused, effectively reducing costs.

Description

Technical Field

[0001] This invention relates to a technology for recycling and utilizing waste residue from hydrometallurgical zinc smelting, specifically to a process for treating tailings residue from hydrometallurgical zinc smelting. Background Technology

[0002] Hydrometallurgical zinc smelting accounts for over 80% of total zinc smelting worldwide, becoming the future direction of global zinc production. The main hydrometallurgical processes include: medium-acid leaching, high-temperature high-acid leaching, and direct oxygen pressure leaching of zinc sulfide concentrate. Early hydrometallurgical zinc smelting largely employed high-temperature high-acid leaching, which produces iron ore slag and lead-silver slag. The stockpiled waste residue was primarily a mixture of these two types of waste residue, as seen in companies like Chifeng Zhongse Zinc Industry and Hanzhong Zinc Industry. The waste residue from high-temperature, high-acid hydrometallurgical zinc smelting consists of fine particles and contains certain amounts of zinc, lead, copper, indium, and associated valuable elements such as gold and silver. If this waste residue is not effectively utilized, it will cause serious environmental pollution and resource waste.

[0003] Waste residue from hydrometallurgical zinc smelting is a secondary resource with high recycling value. Researching the comprehensive utilization of waste residue from hydrometallurgical zinc smelting can not only reduce environmental pollution and alleviate the burden on enterprises, but also turn a harmful resource into a beneficial one, achieving a balance of economic, environmental, and social benefits.

[0004] Chinese patent CN113621813A proposes a method for separating and recovering copper and arsenic from wet zinc-copper slag. This method utilizes high-temperature decomposition of the slag under electromagnetic disturbances and a reducing atmosphere created by a graphite device within a medium-frequency furnace. Arsenic is converted into elemental arsenic and volatilized, directly achieving efficient separation of copper and arsenic from the slag to obtain high-quality crude copper and metallic arsenic products. However, this method involves complex processing and high costs, making practical industrial application difficult.

[0005] Arsenic, as one of the harmful elements in the electrolytic process of hydrometallurgical zinc smelting, requires pollution control due to increasingly stringent environmental regulations. Arsenic is highly toxic and bioaccumulative; if large amounts accumulate without effective treatment and utilization, it will cause serious environmental pollution and resource waste. Therefore, the recovery and treatment of arsenic from the tailings of hydrometallurgical zinc smelting is an unavoidable challenge for the sustainable development of the smelting industry. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a tailings treatment process for hydrometallurgical zinc smelting, which can reduce the As content in the tailings to below 0.1%, meeting the requirements for general solid waste.

[0007] The present invention provides a tailings treatment process for treating the tailings from the waste residue of hydrometallurgical zinc smelting after activation roasting, acid leaching, and chloride leaching.

[0008] As a preferred embodiment of the present invention, the specific steps of the waste residue from the hydrometallurgical zinc smelting process, including activation roasting, acid leaching, and chloride leaching, are as follows:

[0009] The waste residue is activated and roasted to produce roasted sand. The roasted sand is leached with sulfuric acid aqueous solution to obtain metal elements to obtain acid leaching residue. The acid leaching residue is then treated with chloride salt leaching to obtain the tailings.

[0010] As a preferred technical solution of the present invention, the metal elements contained in the tailings include one or more of Zn, Fe, Pb, Ag, In, Cu, Cd, As, Ca, Si, Mg, Mn, and Bi.

[0011] As a preferred embodiment of the present invention, the As content in the tailings is 0.2 to 0.35 wt%.

[0012] As a preferred embodiment of the present invention, the tailings treatment process includes the following steps:

[0013] Add the tailings to a strong acid aqueous solution and stir for 20-40 minutes. Add the metal fluoride and heat to 85-95℃ for 6-9 hours. Cool down and filter to obtain acid leaching residue and acid leaching solution.

[0014] The inventors discovered in their experiments that when the reaction temperature is too low, an effective reaction cannot occur, resulting in an inability to achieve an effective leaching effect of As. However, when the temperature is too high, the reaction is rapid, releasing a large amount of heat, and the HF generated in the reaction evaporates too quickly, failing to react with inclusions of metal elements in the system, thus affecting the leaching rate of As.

[0015] In a preferred embodiment of the present invention, the strong acid is sulfuric acid.

[0016] Sulfuric acid solution provides the best leaching effect. Existing technologies often use strong acid solutions such as hydrochloric acid, sulfuric acid, and phosphoric acid for acid leaching of metallic mineral materials. However, the main component to be leached from the tailings treated in this application is As (As). By reducing the As content, the tailings can meet the requirements for general solid waste and can be directly discharged. The inventors discovered that if hydrochloric acid is used as the leaching solution, its high acidity causes most of the metal elements in the tailings to precipitate, resulting in an excessive metal content in the leaching solution. Furthermore, the use of hydrochloric acid introduces chloride ions, increasing the content of toxic components in the leaching solution and making recycling impossible. In contrast, this invention uses an aqueous sulfuric acid solution as the leaching agent, which has excellent leaching effect on As, does not lead to excessive leaching of metal elements, and does not introduce other toxic components. After arsenic precipitation treatment with sulfide, the leaching solution can be recycled, making it safer and more environmentally friendly.

[0017] As a preferred technical solution of the present invention, the mass ratio of the tailings to the volume ratio of the sulfuric acid aqueous solution is 1g:3ml-5ml.

[0018] When more sulfuric acid is used, the amount of reactant sulfuric acid becomes excessive, leading to the leaching of large amounts of metal elements, particularly Fe from the tailings, which leach into the acid leaching solution, resulting in a high impurity content. This invention uses a specific concentration of sulfuric acid solution and limits the ratio of the volume of the sulfuric acid solution to the mass of the tailings to achieve efficient leaching of arsenic from the tailings. The inventors discovered in experiments that under the experimental conditions of this invention, there is an excellent leaching rate for As, but the leaching rate for other metal elements is not high. Therefore, when recycling the acid leaching solution, only a sulfidation arsenic precipitation treatment is needed, and the resulting sulfuric acid solution can be recycled.

[0019] In a preferred embodiment of the present invention, the metal fluoride is CaF2.

[0020] In a preferred embodiment of the present invention, the mass of CaF2 accounts for 5-10% of the mass of the waste residue.

[0021] Adding CaF2 significantly increases the leaching rate of As in tailings. The inventors believe this is because the reaction of H2SO4 and CaF2 at high temperatures produces HF, which breaks down the silicon-containing phases in the tailings, releasing the As elements trapped within them and thus reducing arsenic levels. Specifically, the best As leaching effect is achieved when CaF2 constitutes 5-10% of the waste residue mass. The inventors found that excessive CaF2 consumption leads to a large amount of acid being wasted, hindering effective As leaching and generating excessive hydrofluoric acid, resulting in waste and environmental pollution. Conversely, insufficient CaF2 production results in a low HF concentration, which is insufficient to effectively break down the silicon-containing phases in the tailings, leading to a lower As leaching rate.

[0022] As a preferred embodiment of the present invention, the concentration of the sulfuric acid aqueous solution is 2-3 mol / L.

[0023] To maintain a high As leaching rate and effectively prevent the excessive leaching of other metal elements, this invention specifically uses a sulfuric acid solution with a concentration of 2-3 mol / L. Furthermore, the ratio of the mass (g) of the tailings residue to the volume (ml) of the sulfuric acid solution is limited to 1:3-5. During the experiment, in addition to limiting the amount used, the concentration of the sulfuric acid solution also needs to be controlled. If the sulfuric acid solution concentration is too high, it will also lead to the excessive leaching of other metal elements, especially Fe, from the tailings residue, thus affecting the leaching of As ions. Simultaneously, the acid leaching solution will contain more impurities, making post-treatment difficult. However, if the sulfuric acid solution concentration is too low, it cannot achieve an effective leaching reaction, and there is insufficient acid to react with CaF2, resulting in inefficient As leaching.

[0024] As a preferred embodiment of the present invention, the As content in the filter residue after the tailings treatment process is ≤0.1%.

[0025] Compared with the prior art, the beneficial effects of this invention are as follows:

[0026] In the tailings treatment process of this invention, acid leaching is performed using a sulfuric acid aqueous solution of a specific concentration and dosage, and metal fluorides are added to further enhance the metal leaching effect. Under the experimental conditions of this invention, the leaching of other metal elements in the tailings can be avoided to a certain extent, achieving efficient leaching of As. The As content in the treated tailings is reduced to ≤0.1%, meeting the requirements for general solid waste; furthermore, the used acid leaching solution has few impurities, is easy to recycle, and can be reused, effectively reducing costs. Detailed Implementation

[0027] The present invention will be further described in detail below through specific embodiments. It should be noted that the following embodiments are further illustrative of the present invention, and not limitations thereof.

[0028] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention. Unless otherwise specified, the experimental materials and reagents used herein are commercially available products conventionally available in this field.

[0029] Example

[0030] Example 1

[0031] This embodiment provides a tailings treatment process for hydrometallurgical zinc smelting. The tailings being treated are waste residue from hydrometallurgical zinc smelting that has undergone activation roasting, acid leaching, and chloride leaching treatments. The specific treatment steps are as follows:

[0032] The waste residue from the hydrometallurgical zinc smelting process was activated and roasted at 670℃ for 2 hours. The roasted calcined sand was then leached with a dilute sulfuric acid aqueous solution at room temperature for 1 hour. After solid-liquid separation, acid-leached residue was obtained. This acid-leached residue was then leached with saturated sodium chloride at 90℃ for 4 hours, and after solid-liquid separation, tailings were obtained. This process involves acid leaching to extract zinc, indium, copper, and cadmium from the hydrometallurgical zinc smelting waste residue into the acid leaching solution, and chloride leaching to extract lead and silver from the waste residue into the chloride leaching solution, thus separating the valuable metals. The main elements in the tailings were iron and silicon. The metal element content in the tailings is shown in Table 1.

[0033] Table 1

[0034] name Zn Fe Pb Ag In Cu Cd As <![CDATA[1 # Tailings / % 0.16 43 0.033 <0.001 0.012 0.017 <0.001 0.32 name Ca Si Mg Mn Bi <![CDATA[Cl - ]]> Total S <![CDATA[1 # Tailings / % 0.042 34.0 0.005 0.014 0.016 <0.005 0.15

[0035] The specific steps for treating the tailings in this embodiment are as follows:

[0036] Add 10g of tailings to 30mL of 3mol / L sulfuric acid aqueous solution, stir for 30min, add 1g of CaF2, heat to 90℃, and react for 6h; cool down and filter to obtain acid leaching residue and acid leaching solution.

[0037] Example 2

[0038] This embodiment provides a tailings treatment process for hydrometallurgical zinc smelting, wherein the metal element content in the treated tailings is the same as in Embodiment 1.

[0039] The difference from Example 1 is that the specific treatment steps for the tailings in this example are as follows:

[0040] Add 10g of tailings to 30mL of 2mol / L sulfuric acid aqueous solution, stir for 30min, add 1g of CaF2, heat to 90℃, and react for 8h; cool down and filter to obtain acid leaching residue and acid leaching solution.

[0041] Example 3

[0042] This embodiment provides a tailings treatment process for hydrometallurgical zinc smelting. The tailings being treated are waste residue from hydrometallurgical zinc smelting that has undergone activation roasting, acid leaching, and chloride leaching treatments. The specific treatment steps are as follows:

[0043] The waste residue from the hydrometallurgical zinc smelting process was activated and roasted at 670℃ for 2 hours. The roasted calcined sand was then leached with a dilute sulfuric acid aqueous solution at room temperature for 1 hour. After solid-liquid separation, acid-leached residue was obtained. This acid-leached residue was then leached with saturated sodium chloride at 90℃ for 4 hours, and after solid-liquid separation, tailings were obtained. This process involves acid leaching to extract zinc, indium, copper, and cadmium from the hydrometallurgical zinc smelting waste residue into the acid leaching solution, and chloride leaching to extract lead and silver from the waste residue into the chloride leaching solution, thus separating the valuable metals. The main elements in the tailings were iron and silicon. The metal element content in the tailings is shown in Table 2.

[0044] Table 2

[0045] <![CDATA[2 # Tailings Fe Pb Zn <![CDATA[In / g·t -1 ]]> <![CDATA[Ag / g·t -1 ]]> Cu content / % 33.76 0.317 0.81 33 9.44 0.057 <![CDATA[2 # Tailings Cd As S Si Ca content / % 0.069 0.24 5.64 10.57 6.54

[0046] The specific steps for treating the tailings in this embodiment are as follows:

[0047] Add 30g of tailings to 90mL of 3mol / L sulfuric acid aqueous solution, stir for 30min, add 3g of CaF2, heat to 90℃, and react for 8h; cool down and filter to obtain acid leaching residue and acid leaching solution.

[0048] Example 4

[0049] This embodiment provides a tailings treatment process for hydrometallurgical zinc smelting, wherein the metal element content in the treated tailings is the same as in Embodiment 1.

[0050] The difference from Example 1 is that the specific treatment steps for the tailings in this example are as follows:

[0051] Add 10g of tailings to 30mL of 3mol / L sulfuric acid aqueous solution, stir for 30min, add 0.6g of CaF2, heat to 90℃, and react for 6h; cool down and filter to obtain acid leaching residue and acid leaching solution.

[0052] Example 5

[0053] This embodiment provides a tailings treatment process for hydrometallurgical zinc smelting, wherein the metal element content in the treated tailings is the same as in Embodiment 1.

[0054] The difference from Example 1 is that the specific treatment steps for the tailings in this example are as follows:

[0055] Add 10g of tailings to 50mL of 3mol / L sulfuric acid aqueous solution, stir for 30min, add 1g of CaF2, heat to 90℃, and react for 6h; cool down and filter to obtain acid leaching residue and acid leaching solution.

[0056] Comparative Example 1

[0057] This embodiment provides a tailings treatment process for hydrometallurgical zinc smelting, wherein the metal element content in the treated tailings is the same as in Embodiment 1.

[0058] The difference from Example 1 is that the specific treatment steps for the tailings in this example are as follows:

[0059] Add 10g of tailings to 30mL of 1mol / L sulfuric acid aqueous solution, stir for 30min, heat to 90℃, and react for 6h; cool down and filter to obtain acid leaching residue and acid leaching solution.

[0060] Comparative Example 2

[0061] This embodiment provides a tailings treatment process for hydrometallurgical zinc smelting, wherein the metal element content in the treated tailings is the same as in Embodiment 1.

[0062] The difference from Example 1 is that the specific treatment steps for the tailings in this example are as follows:

[0063] Add 10g of tailings to 20mL of 3mol / L sulfuric acid aqueous solution, stir for 30min, add 1g of CaF2, heat to 90℃, and react for 6h; cool down, filter to obtain acid leaching residue and acid leaching solution.

[0064] Comparative Example 3

[0065] This embodiment provides a tailings treatment process for hydrometallurgical zinc smelting, wherein the metal element content in the treated tailings is the same as in Embodiment 1.

[0066] The difference from Example 1 is that the specific treatment steps for the tailings in this example are as follows:

[0067] Add 10g of tailings to 30mL of 3mol / L sulfuric acid aqueous solution, stir for 30min, add 1g of CaF2, heat to 80℃, and react for 6h; cool down and filter to obtain acid leaching residue and acid leaching solution.

[0068] Comparative Example 4

[0069] This embodiment provides a tailings treatment process for hydrometallurgical zinc smelting, wherein the metal element content in the treated tailings is the same as in Embodiment 1.

[0070] The difference from Example 1 is that the specific treatment steps for the tailings in this example are as follows:

[0071] Add 10g of tailings to 30mL of 3mol / L sulfuric acid aqueous solution, stir for 30min, add 1.5g of CaF2, heat to 90℃, and react for 6h; cool down and filter to obtain acid leaching residue and acid leaching solution.

[0072] Performance testing

[0073] The metal content of the acid leaching residues from Examples 1-5 and Comparative Examples 1-4 was tested using ICP (Inductively Coupled Plasma Emission Spectrometry). The As leaching rate was calculated based on the mass of the tailings and the mass of the acid leaching residue, as well as its As content. The leaching rate data are shown in Table 3 below.

[0074] Table 3

[0075] Example As leaching rate / % As content in leaching residue / % Fe leaching rate / % Example 1 94.31 0.02 18.62 Example 2 72.4 0.092 17.20 Example 3 61.0 0.096 16.81 Example 4 74.55 0.09 19.09 Example 5 97.19 0.01 19.77 Comparative Example 1 31.06 0.237 11.23 Comparative Example 2 65.50 0.12 16.76 Comparative Example 3 57.34 0.15 16.12 Comparative Example 4 41.81 0.18 15.76

[0076] As can be seen from the test results of the embodiments in Table 3 above, the As content in the tailings after acid leaching treatment according to the present invention is reduced to ≤0.1%, which meets the requirements of general solid waste.

[0077] Obviously, the above embodiments are merely examples for clear illustration and are not intended to limit the implementation. Those skilled in the art can make other variations or modifications based on the above description, and any obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A tailings treatment process for hydrometallurgical zinc smelting, characterized in that, The tailings treatment process is used to treat the tailings after the waste residue from hydrometallurgical zinc smelting has undergone activation roasting, acid leaching, and chloride leaching. The tailings treatment process includes the following steps: Add the tailings to a strong acid aqueous solution and stir for 20-40 minutes. Add the metal fluoride and heat to 85-95℃ to react for 6-9 hours. Cool down and filter to obtain acid leaching residue and acid leaching solution. The strong acid is sulfuric acid; the concentration of the sulfuric acid aqueous solution is 2-3 mol / L. The mass ratio of the tailings to the volume of the sulfuric acid aqueous solution is 1g:3mL-5mL; The metal fluoride is CaF2, and the mass of CaF2 accounts for 5-10% of the mass of the waste residue; The tailings contain one or more of the following metallic elements: Zn, Fe, Pb, Ag, In, Cu, Cd, As, Ca, Si, Mg, Mn, and Bi; the As content in the tailings is 0.2 to 0.35 wt%, and the As is encapsulated in a silicon phase.

2. The tailings treatment process for hydrometallurgical zinc smelting according to claim 1, characterized in that, The specific steps for the activation roasting, acid leaching, and chloride leaching of the waste residue from the hydrometallurgical zinc refining process are as follows: The waste residue is activated and roasted to produce roasted sand. The roasted sand is leached with sulfuric acid aqueous solution to obtain metal elements to obtain acid leaching residue. The acid leaching residue is then treated with chloride salt leaching to obtain the tailings.

3. The tailings treatment process for hydrometallurgical zinc smelting according to claim 1, characterized in that, The As content in the filter residue after the tailings treatment process is ≤0.1%.