Electrochemical pretreatment method for lead-containing heavy sand

Abstract

The present application provides an electrochemical pretreatment method for lead-containing heavy sand, which belongs to the field of hydrometallurgy technology. The present invention uses two-step electrolysis, first electrolyzing NaCl to oxidize the galena in the lead-containing heavy sand and generate lead chloride and elemental sulfur, and then electrolyzing manganese salt to oxidize the metal sulfide in the lead-containing heavy sand, thereby completing the pretreatment of the lead-containing heavy sand. The present invention can adjust the concentration ratio of NaCl and manganese salt in the electrolyte and the voltage in the two-step electrolysis to make NaCl and Mn 2+ The electrolysis is carried out in steps, sequentially reducing the lead in the lead-containing heavy sand and oxidizing the metal sulfides. The pretreatment method of the present invention not only recovers the lead as a resource but also removes the sulfides within it, providing qualified raw materials for subsequent gold smelting. This method features a short process flow, convenient operation, simple equipment, and is environmentally friendly, providing a highly valuable technical solution for the field of precious metal hydrometallurgy.

Description

Technical Field

[0001] The invention relates to the technical field of hydrometallurgy, and in particular to an electrochemical pretreatment method for lead-containing heavy sand. Background Art

[0002] Currently, the industry's commonly used processing process for gold mines containing large gold particles is grinding, classification, gravity separation, and flotation. First, the ore enters a high-speed ball mill, where it is ground to a suitable particle size, laying the foundation for subsequent processes. The ground ore is then transported to the Nielsen equipment for gravity separation. Using centrifugal force and other principles, the Nielsen equipment separates heavy minerals from light minerals, producing gravity-separated concentrate, or heavy sand. Heavy sand typically contains 10% to 50% gold and is a key intermediate product for smelters. To produce a tradable product, the heavy sand requires further refining and purification, ultimately resulting in gold and silver ingots that meet national standards.

[0003] Heavy sand produced by gold mining companies, in addition to precious metals like gold and silver, typically contains significant amounts of impurities such as lead, iron, and sulfur. High lead content, in particular, increases the difficulty of smelting heavy sand. To ensure high-quality gold ingots are subsequently refined, pre-treatment is typically performed to separate most of the impurities from the heavy sand.

[0004] Currently, the main smelting processes for lead-containing heavy sand include pyrometallurgy, nitric acid impurity removal, and hydrochloric acid impurity removal. However, pyrometallurgy suffers from poor operating conditions, complex operations, and difficulty recovering gold from the matte. Nitric acid impurity removal produces nitrogen oxide gases, which pollute the environment and is ineffective. Furthermore, the solubility of lead chloride varies significantly with temperature, making it prone to precipitation during hydrochloric acid impurity removal, making solid-liquid separation difficult. Summary of the Invention

[0005] In view of the technical problems existing in the background technology, the present application provides an electrochemical pretreatment method for lead-containing heavy sand, which aims to solve the problems of poor precious metal recovery effect, complex process flow, and environmental pollution in the existing lead-containing heavy sand smelting process.

[0006] The present application provides a method for electrochemical pretreatment of lead-containing heavy sand, comprising the following steps:

[0007] S1. The lead-containing heavy sand is finely ground and added to an electrolytic tank containing an electrolyte, stirred, and then a first pH adjustment is performed, a first electrolysis is performed, and then a first solid-liquid separation is performed to obtain a solid tailing and a filtered electrolyte;

[0008] S2. The filtered electrolyte is cooled to obtain lead chloride and lead electrolyte after precipitation;

[0009] S3. The solid tailings and the electrolyte after lead precipitation are mixed, stirred evenly, and then a second pH adjustment is performed, a second electrolysis is performed, and then a second solid-liquid separation and washing are performed to obtain a gold-rich slag.

[0010] In the technical solution of the embodiment of the present application, a two-step electrolysis is performed, wherein NaCl is first electrolyzed to oxidize the galena in the lead-containing heavy sand and generate lead chloride and elemental sulfur, and then the manganese salt is electrolyzed to oxidize the metal sulfide in the lead-containing heavy sand, thereby completing the pretreatment of the lead-containing heavy sand. The present invention can adjust the concentration ratio of NaCl and manganese salt in the electrolyte and the voltage in the two-step electrolysis to achieve the desired effect. 2+ The electrolysis is carried out in steps to sequentially reduce the lead in the lead-containing heavy sand and oxidize the metal sulfides. The pretreatment method of the present invention not only recovers the lead as a resource, but also removes the sulfides in it, providing qualified products for subsequent gold smelting.

[0011] In some embodiments, in step S1, the electrolyte in the first electrolysis electrolyte includes sodium chloride and / or potassium chloride, MnCl2 and / or MnSO4; the concentration of the sodium chloride and / or potassium chloride is 40~300g / L, and the concentration of the MnCl2 and / or MnSO4 is 5~20g / L.

[0012] In this embodiment, by controlling the concentration of each electrolytic solution and combining it with the voltage of the subsequent first electrolysis, NaCl is electrolyzed first in the system to generate hypochlorite.

[0013] In some embodiments, in step S1, the voltage of the first electrolysis is 1.5-3 V, and the time of the electrolysis is 3-6 h.

[0014] In this embodiment, through a specific electrolysis voltage and electrolysis time, the galena in the heavy sand and the hypochlorite generated by the electrolysis of NaCl undergo an oxidation reaction under the action of the anode to generate elemental sulfur and lead ions, and the lead in the solution exists in the form of lead chloride in the liquid phase.

[0015] In some embodiments, in step S3, the voltage of the second electrolysis is 6-15V, and the electrolysis time is 1-5 hours.

[0016] In this embodiment, as the electrolysis of the electrolyte NaCl in the electrolyte is completed, a second electrolysis voltage is applied to make the Mn 2+ Electrolysis occurs to produce manganese dioxide.

[0017] In some embodiments, in step S1, the pH adjuster for the first pH adjustment is hydrochloric acid, and the pH value of the first pH adjustment is 1-2.

[0018] In this embodiment, under this pH condition, the solubility of galena is good, which provides convenience for subsequent electrolysis.

[0019] In some embodiments, in step S1, the fine grinding refers to grinding fineness of -0.074 mm accounting for 60-90%.

[0020] In this embodiment, by grinding the mineral to a specific fineness, the subsequent electrolysis can achieve a better effect in removing impurities.

[0021] In some embodiments, in step S1, the mass concentration of lead-containing heavy sand in the electrolytic cell is 5-40%.

[0022] In some embodiments, in step S3, the pH adjuster for the second pH adjustment is hydrochloric acid or sulfuric acid, and the pH value of the second pH adjustment is 1-2.

[0023] In this embodiment, the manganese dioxide produced by electrolysis reacts with the sulfide minerals under acidic conditions, causing the sulfide minerals to be oxidized and dissolved, and the manganese dioxide is reduced to Mn 2+ , forming a cycle.

[0024] In some embodiments, in step S1, the first solid-liquid separation method is hot filtration.

[0025] In this embodiment, hot filtration is used to prevent lead chloride in the electrolyte from precipitating as the temperature decreases during the filtration process.

[0026] In some embodiments, in step S1, the material of the electrolytic cell is one of PP, fiberglass, PPH or PPR; the material of the anode of the electrolytic cell is one of graphite, ruthenium-plated titanium plate or ruthenium-plated titanium mesh, and the material of the cathode is one of titanium plate, titanium mesh or graphite.

[0027] In this embodiment, suitable electrolytic materials can enable the electrolytic reaction to proceed smoothly.

[0028] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. DETAILED DESCRIPTION

[0029] The following embodiments of the technical solution of the present application are described in detail. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only used as examples and are not intended to limit the scope of protection of the present application.

[0030] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0031] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0032] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0033] In order to solve the problems of poor precious metal recovery effect, complex process flow, environmental pollution and other problems in the existing lead-containing heavy sand smelting process, the present application provides an electrochemical pretreatment method for lead-containing heavy sand. Through two-step electrolysis, NaCl is first electrolyzed to oxidize the galena in the lead-containing heavy sand to generate lead chloride and elemental sulfur, and then manganese salt is electrolyzed to oxidize the metal sulfide in the lead-containing heavy sand to complete the pretreatment of the lead-containing heavy sand. The present invention can adjust the concentration ratio of NaCl and manganese salt in the electrolyte and the voltage in the two-step electrolysis to make NaCl and Mn 2+ The electrolysis is carried out in steps, sequentially reducing the lead in the lead-containing heavy sand and oxidizing the metal sulfides. The pretreatment method of the present invention not only recovers the lead as a resource but also removes the sulfides within it, providing qualified products for subsequent gold smelting. This method features a short process flow, convenient operation, simple equipment, and is environmentally friendly, providing a highly valuable technical solution for the field of precious metal hydrometallurgy.

[0034] The present application provides a method for electrochemical pretreatment of lead-containing heavy sand, comprising the following steps:

[0035] S1. The lead-containing heavy sand is finely ground and added to an electrolytic tank containing an electrolyte, stirred, and then a first pH adjustment is performed, a first electrolysis is performed, and then a first solid-liquid separation is performed to obtain a solid tailing and a filtered electrolyte;

[0036] S2. The filtered electrolyte is cooled to obtain lead chloride and lead electrolyte after precipitation;

[0037] S3. The solid tailings and the electrolyte after lead precipitation are mixed, stirred evenly, and then a second pH adjustment is performed, a second electrolysis is performed, and then a second solid-liquid separation and washing are performed to obtain a gold-rich slag.

[0038] In the technical solution of the embodiment of the present application, a two-step electrolysis is performed, wherein NaCl is first electrolyzed to oxidize the galena in the lead-containing heavy sand to generate lead chloride and elemental sulfur, and then the manganese salt is electrolyzed to oxidize the metal sulfide in the lead-containing heavy sand, thereby completing the pretreatment of the lead-containing heavy sand. The present invention can adjust the concentration ratio of NaCl and manganese salt in the electrolyte and the voltage in the two-step electrolysis to make NaCl and Mn 2+ The electrolysis is carried out in steps to sequentially reduce the lead in the lead-containing heavy sand and oxidize the metal sulfides. The pretreatment method of the present invention not only recovers the lead as a resource, but also removes the sulfides in it, providing qualified products for subsequent gold smelting.

[0039] Furthermore, in some embodiments, in step S1, the electrolyte in the first electrolysis electrolyte includes sodium chloride and / or potassium chloride, MnCl2 and / or MnSO4; the concentration of the sodium chloride and / or potassium chloride is 40~300g / L, and the concentration of the MnCl2 and / or MnSO4 is 5~20g / L.

[0040] In the technical solution of the embodiment of the present application, by controlling the concentration of each electrolysis in the electrolyte and combining it with the voltage of the subsequent first electrolysis, NaCl is electrolyzed first in the system to generate sodium hypochlorite.

[0041] Furthermore, in some embodiments, in step S1, the voltage of the first electrolysis is 1.5-3 V, and the time of the electrolysis is 3-6 h.

[0042] In the technical solution of the embodiment of the present application, through a specific electrolysis voltage and electrolysis time, the galena in the heavy sand and the hypochlorite generated by the electrolysis of NaCl undergo an oxidation reaction under the action of the anode to generate elemental sulfur and lead ions, and the lead in the solution exists in the liquid phase in the form of lead chloride.

[0043] Furthermore, in some embodiments, in step S3, the voltage of the second electrolysis is 6-15 V, and the time of the electrolysis is 1-5 h.

[0044] In the technical solution of the embodiment of the present application, as the electrolysis of the electrolyte NaCl in the electrolyte is completed, a second electrolysis voltage is applied to make the Mn 2+ Electrolysis occurs to produce manganese dioxide.

[0045] Furthermore, in some embodiments, in step S1, the pH adjuster for the first pH adjustment is hydrochloric acid, and the pH value of the first pH adjustment is 1-2.

[0046] In the technical solution of the embodiment of the present application, under this pH condition, the solubility of galena is good, which provides convenience for subsequent electrolysis.

[0047] Furthermore, in some embodiments, in step S1, the fine grinding refers to a grinding fineness of -0.074 mm accounting for 60-90%.

[0048] In the technical solution of the embodiment of the present application, by grinding the mineral to a specific fineness, the effect of subsequent electrolysis in removing impurities is improved.

[0049] Furthermore, in some embodiments, in step S1, the mass concentration of lead-containing heavy sand in the electrolytic cell is 5-40%.

[0050] Furthermore, in some embodiments, in step S3, the pH adjuster for the second pH adjustment is hydrochloric acid or sulfuric acid, and the pH value of the second pH adjustment is 1-2.

[0051] In the technical solution of the embodiment of the present application, the manganese dioxide produced by electrolysis reacts with the sulfide minerals under acidic conditions, causing the sulfide minerals to be oxidized and dissolved, and the manganese dioxide is reduced to Mn 2+ , forming a cycle.

[0052] Furthermore, in some embodiments, in step S1, the first solid-liquid separation method is hot filtration.

[0053] In the technical solution of the embodiment of the present application, heat filtration is used to prevent lead chloride in the electrolyte from precipitating as the temperature decreases during the filtration process.

[0054] Furthermore, in some embodiments, in step S1, the material of the electrolytic cell is one of PP, fiberglass, PPH or PPR; the material of the anode of the electrolytic cell is one of graphite, ruthenium-plated titanium plate or ruthenium-plated titanium mesh, and the material of the cathode is one of titanium plate, titanium mesh or graphite.

[0055] In the technical solution of the embodiment of the present application, suitable electrolytic materials can enable the electrolytic reaction to proceed smoothly.

[0056] Some specific examples are listed below. It should be noted that the examples described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used without manufacturer's indication are all commercially available conventional products.

[0057] Example 1

[0058] This embodiment provides a method for electrochemical pretreatment of lead-containing heavy sand, which specifically includes the following steps:

[0059] (1) Grind heavy sand to -0.074 mm (60% by mass) and add it to a PP electrolytic cell containing 180 g / L sodium chloride and 10 g / L manganese chloride. The anode is a ruthenium-plated titanium plate and the cathode is a titanium mesh. The mass concentration of the slurry in the electrolytic cell is 5%. Use hydrochloric acid to adjust the pH of the slurry to 2. Apply a voltage of 2 V between the anode and cathode, and electrolyze for 6 hours under stirring. Then perform hot filtration to obtain solid tailings and filtered electrolyte.

[0060] (2) Cooling the filtered electrolyte to obtain lead chloride and lead-precipitated electrolyte.

[0061] (3) The solid tailings and the electrolyte after lead precipitation are mixed and added to the electrolytic cell. After stirring evenly, the pH of the mixture is adjusted to 2 with hydrochloric acid. A voltage of 10 V is applied between the anode and the cathode. The mixture is electrolyzed for 5 hours under stirring, and then filtered and washed to obtain gold-rich slag.

[0062] The sources and performance parameters of the raw materials are as follows:

[0063] The raw materials used were all heavy sand products produced by a domestic mining company. The contents of the main metal elements are shown in Table 1. Lead mainly exists in the form of sulfide galena, followed by sulfate, and the least is oxide, which are 71.13%, 20.23%, and 8.64% respectively.

[0064] Table 1 Content of main elements in heavy sand

[0065]

[0066] Examples 2-3 and Comparative Examples 1-2

[0067] Examples 2-3 and Comparative Examples 1-2 respectively provide a method for electrochemical pretreatment of lead-containing heavy sand. Compared with Example 1, the difference is that the amount of electrolyte in step (1) is different. The amount of electrolyte corresponding to each example and comparative example is shown in Table 2. The other steps are roughly the same as those in Example 1 and are not repeated here.

[0068] Table 2 Amount of electrolyte used in Examples 2-3 and Comparative Examples 1-2

[0069]

[0070] Examples 4-5 and Comparative Examples 3-4

[0071] Examples 4-5 and Comparative Examples 3-4 respectively provide a method for electrochemical pretreatment of lead-containing heavy sand. Compared with Example 1, the difference is that the voltage of electrolysis in step (1) is different. The electrolysis voltages corresponding to the embodiments and comparative examples are shown in Table 3. The other steps are substantially the same as those in Example 1 and are not described again here.

[0072] Table 3 Electrolysis voltage in step (1) in Examples 4 to 7 and Comparative Examples 3 to 6

[0073]

[0074] Examples 6-7 and Comparative Examples 5-6

[0075] Examples 6-7 and Comparative Examples 5-6 respectively provide a method for electrochemical pretreatment of lead-containing heavy sand. Compared with Example 1, the difference is that the voltage of electrolysis in step (3) is different. The electrolysis voltages corresponding to each embodiment and comparative example are shown in Table 4. The other steps are substantially the same as those in Example 1 and are not described again here.

[0076] Table 4 Electrolysis voltage in step (3) in Examples 6-7 and Comparative Examples 5-6

[0077]

[0078] The purity of the lead chloride precipitated in step (2) in Examples 1 to 7 and Comparative Examples 1 to 6, the removal effect of impurity elements in the final gold-rich slag, the yield of the gold-rich slag, and the recovery rate of gold in the gold-rich slag were analyzed respectively. The results are shown in Table 5.

[0079] Table 5 Purity of lead chloride precipitated in Examples 1-7 and Comparative Examples 1-6, removal effect of impurity elements in the final gold-rich slag, yield of gold-rich slag, and gold recovery rate

[0080]

[0081] It can be seen from Examples 1 to 7 that the present invention has a high gold recovery rate, the sulfur oxidation removal rate is above 97%, the lead dissolution rate is above 99%, and the iron and copper removal rates also achieve good results; it can be seen from Comparative Examples 1 to 2 that when the concentrations of sodium chloride and manganese chloride in the electrolyte decrease, the overall removal effect of impurity elements deteriorates, resulting in an increase in slag yield, which affects the subsequent smelting effect; it can be seen from Comparative Examples 3 to 4 that when the electrolysis voltage in step (1) is too large, chlorine gas is generated due to electrolysis. Overflow affects the sulfide oxidation effect, reduces the impurity element removal rate, and increases the slag production. When the electrolysis voltage in step (1) is too low, the amount of hypochlorite generated by electrolysis is reduced, resulting in a decrease in the impurity element removal rate and an increase in the slag production, affecting the pretreatment effect. It can be seen from Comparative Examples 5 to 6 that when the electrolysis voltage in step (3) is too high, the side reaction increases, affecting the formation of manganese oxide, thereby reducing the sulfide removal effect. When the electrolysis voltage in step (3) is too low, the rate of generating manganese oxide slows down, affecting the impurity removal effect.

[0082] In summary, the present application provides a method for electrochemical pretreatment of lead-containing heavy sand. Through two-step electrolysis, NaCl is first electrolyzed to reduce galena in the lead-containing heavy sand to lead chloride, and then manganese salt is electrolyzed to oxidize the metal sulfide in the lead-containing heavy sand, thereby completing the pretreatment of the lead-containing heavy sand. The present invention can adjust the concentration ratio of NaCl and manganese salt in the electrolyte and the voltage in the two-step electrolysis to reduce the galena in the lead-containing heavy sand to lead chloride. 2+ The electrolysis is carried out in steps, sequentially reducing the lead in the lead-containing heavy sand and oxidizing the metal sulfides. The pretreatment method of the present invention not only recovers the lead as a resource but also removes the sulfides within it, providing qualified products for subsequent gold smelting. This method features a short process flow, convenient operation, simple equipment, and is environmentally friendly, providing a highly valuable technical solution for the field of precious metal hydrometallurgy.

[0083] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for electrochemical pretreatment of lead-containing heavy sand, characterized in that: The following steps are involved: S1. The lead-containing heavy sand is finely ground and added to an electrolytic tank containing an electrolyte, stirred, and then a first pH adjustment is performed, a first electrolysis is performed, and then a first solid-liquid separation is performed to obtain a solid tailing and a filtered electrolyte; S2. The filtered electrolyte is cooled to obtain lead chloride and lead electrolyte after precipitation; S3. The solid tailings and the electrolyte after lead precipitation are mixed and stirred, and then a second pH adjustment is performed, a second electrolysis is performed, and then a second solid-liquid separation and washing is performed to obtain a gold-rich slag; Wherein, the electrolyte in the electrolyte of the first electrolysis includes sodium chloride and MnCl2; the concentration of sodium chloride in the electrolyte is 40-300 g / L, and the concentration of MnCl2 in the electrolyte is 5-20 g / L; The voltage of the first electrolysis is 1.5-3V, and the electrolysis time is 3-6 hours. The voltage of the second electrolysis is 6-15V, and the electrolysis time is 1-5 hours.

2. The lead-containing heavy sand electrochemical pretreatment method according to claim 1, characterized in that: In step S1, the pH value adjuster for the first pH adjustment is hydrochloric acid, and the pH value of the first pH adjustment is 1-2.

3. The lead-containing heavy sand electrochemical pretreatment method according to claim 1, characterized in that: In step S1, the fine grinding refers to grinding with a fineness of -0.074 mm accounting for 60-90%.

4. The lead-containing heavy sand electrochemical pretreatment method according to claim 1, characterized in that: In step S1, the mass concentration of lead-containing heavy sand in the electrolytic cell is 5-40%.

5. The lead-containing heavy sand electrochemical pretreatment method according to claim 1, characterized in that: In step S3, the pH value adjuster for the second pH adjustment is hydrochloric acid or sulfuric acid, and the pH value of the second pH adjustment is 1-2.

6. The lead-containing heavy sand electrochemical pretreatment method according to claim 1, characterized in that: In step S1, the first solid-liquid separation method is hot filtration.

7. The lead-containing heavy sand electrochemical pretreatment method according to claim 1, characterized in that: In step S1, the material of the electrolytic cell is one of PP, fiberglass, PPH or PPR; the material of the anode of the electrolytic cell is one of graphite, ruthenium-plated titanium plate or ruthenium-plated titanium mesh, and the material of the cathode is one of titanium plate, titanium mesh or graphite.

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