Electrochemical pretreatment method for lead-containing heavy sand

Abstract

The invention provides an electrochemical pretreatment method for lead-containing heavy sand, and belongs to the technical field of hydrometallurgy. According to the method, through two-step electrolysis, NaCl is electrolyzed, galena in the lead-containing heavy sand is oxidized, lead chloride and elemental sulfur are generated, then manganese salt is electrolyzed, metal sulfide in the lead-containing heavy sand is oxidized, and pretreatment of the lead-containing heavy sand is completed. According to the method, NaCl and Mn < 2 + > can be electrolyzed step by step by regulating and controlling the concentration proportion of NaCl and manganese salt in the electrolyte and the voltage in two-step electrolysis, and reduction of lead in the lead-containing heavy sand and oxidation of metal sulfide are sequentially achieved. According to the pretreatment method, resource recycling of the lead can be achieved, sulfide in the lead can be removed, qualified raw materials are provided for follow-up gold smelting, the method is short in process, convenient to operate, simple in equipment and environmentally friendly, and a valuable technical scheme is provided for the field of precious metal hydrometallurgy.

Description

Technical Field

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

[0002] Currently, for gold ores containing large particles of gold, the commonly used treatment process in the industry is the grinding-classification-gravity separation-flotation process. First, the ore enters a high-speed rotating ball mill and is ground into an appropriate particle size, laying a foundation for subsequent processes. Subsequently, the ground ore is transported to a Nelson device for gravity separation. The Nelson device separates heavy minerals from light minerals by means of centrifugal force and other principles to obtain gravity separation concentrate, i.e., heavy sand. The gold content in the heavy sand is generally between 10% and 50%, which is an important intermediate product for smelting enterprises. To obtain marketable products, the heavy sand still needs to be further refined and purified to finally obtain gold ingots and silver ingots that meet national standards.

[0003] The heavy sand produced by gold mining enterprises usually contains a large amount of impurity elements such as lead, iron, and sulfur in addition to the two precious metals of gold and silver. Especially when the lead content is relatively high, it will increase the smelting difficulty of the heavy sand. To obtain high-quality gold ingots in subsequent refining, pretreatment is generally required before refining to separate most of the impurity elements in the heavy sand.

[0004] Currently, the main smelting processes for lead-bearing heavy sand are pyrometallurgical smelting, nitric acid impurity removal, and hydrochloric acid impurity removal processes. However, pyrometallurgical smelting has problems such as a poor operating environment, complex operations, and difficult recovery of gold in matte; nitric acid impurity removal will generate nitrogen oxide gases, pollute the environment, and the impurity removal effect is not good; and the solubility of lead chloride changes greatly with temperature, and there is a problem that lead chloride is easily precipitated during hydrochloric acid impurity removal, resulting in difficult solid-liquid separation. Summary of the Invention

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

[0006] The present application provides an electrochemical pretreatment method for lead-bearing heavy sand, which includes the following steps: S1. Fine-grind the lead-bearing heavy sand, add it to an electrolytic cell filled with an electrolyte, stir evenly, perform a first pH adjustment, perform a first electrolysis, and then perform a first solid-liquid separation to obtain solid tailings and filtered electrolyte; S2. Cool the filtered electrolyte to obtain lead chloride and the electrolyte after lead precipitation; S3. Mix the solid tailings and the electrolyte after lead precipitation, stir evenly, perform a second pH adjustment, perform a second electrolysis, and then perform a second solid-liquid separation and washing to obtain gold-rich slag.

[0007] In the technical solution of the embodiment of the present application, through two-step electrolysis, first electrolyze NaCl to oxidize galena in the lead-bearing placer and generate lead chloride and elemental sulfur, and then electrolyze the manganese salt to oxidize metal sulfides in the lead-bearing placer to complete the pretreatment of the lead-bearing placer. By adjusting the concentration ratio of NaCl and manganese salt in the electrolyte and the voltage in the two-step electrolysis, the present invention can make NaCl and Mn 2+ be electrolyzed step by step to successively realize the reduction of lead and the oxidation of metal sulfides in the lead-bearing placer. The pretreatment method of the present invention can not only realize the resource recovery of lead, but also remove the internal sulfide thereof, providing qualified products for the subsequent gold smelting.

[0008] In some embodiments, in step S1, the electrolytes in the electrolyte of the first electrolysis include sodium chloride and / or potassium chloride, MnCl2 and / or MnSO4; the concentration of the sodium chloride and / or potassium chloride is 40-300 g / L, and the concentration of the MnCl2 and / or MnSO4 is 5-20 g / L.

[0009] In this embodiment, by controlling the concentration of each electrolysis in the electrolyte and combining with the voltage of the subsequent first electrolysis, the electrolysis of NaCl occurs first in the system to generate hypochlorite.

[0010] In some embodiments, in step S1, the voltage of the first electrolysis is 1.5-3 V, and the electrolysis time is 3-6 h.

[0011] In this embodiment, through specific electrolysis voltage and electrolysis time, galena in the placer reacts with hypochlorite generated by the electrolysis of NaCl at the anode to undergo an oxidation reaction, generating elemental sulfur and lead ions, and the lead in the solution exists in the liquid phase in the form of lead chloride.

[0012] In some embodiments, in step S3, the voltage of the second electrolysis is 6-15 V, and the electrolysis time is 1-5 h.

[0013] In this embodiment, as the electrolysis of the electrolyte NaCl in the electrolyte is completed, the second electrolysis voltage is applied to electrolyze Mn in the electrolyte 2+ to generate manganese dioxide.

[0014] In some embodiments, in step S1, the pH value regulator for the first pH value adjustment is hydrochloric acid, and the pH value for the first pH value adjustment is 1-2.

[0015] In this embodiment, under this pH value condition, the solubility of galena is relatively good, which is convenient for subsequent electrolysis.

[0016] In some embodiments, in step S1, the fine grinding means that the grinding fineness is -0.074 mm accounting for 60-90%.

[0017] In this embodiment, by grinding the minerals to a specific fineness, the effect of removing impurities in the subsequent electrolysis is better.

[0018] In some embodiments, in step S1, the mass concentration of lead-bearing placer in the electrolytic cell is 5-40%.

[0019] In some embodiments, in step S3, the pH regulator for the second pH adjustment is hydrochloric acid or sulfuric acid, and the pH value for the second pH adjustment is 1-2.

[0020] In this embodiment, the manganese dioxide generated by electrolysis reacts with sulfide minerals under acidic conditions, causing the sulfide minerals to oxidize and dissolve, while the manganese dioxide is reduced back to Mn 2+ , forming a cycle.

[0021] In some embodiments, in step S1, the method for the first solid-liquid separation is hot filtration.

[0022] In this embodiment, through hot filtration, the precipitation of lead chloride in the electrolyte during the filtration process is prevented as the temperature decreases.

[0023] 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.

[0024] In this embodiment, suitable electrolytic materials can make the electrolysis reaction proceed smoothly.

[0025] The above description is only an overview of the technical solution of the present application. In order to be able to understand the technical means of the present application more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features, and advantages of the present application more obvious and understandable, the specific embodiments of the present application are specifically given below. Detailed Description of the Embodiment

[0026] The embodiments of the technical solution of the present application will be described in detail below. The following embodiments are only used to illustrate the technical solution of the present application more clearly, so they are only examples and cannot be used to limit the protection scope of the present application.

[0028] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order, or primary-secondary relationship of the indicated technical features. In the description of the embodiments of the present application, "a plurality" means more than two, unless otherwise specifically defined.

[0029] Reference to "embodiments" in this specification means that the specific features, structures, or characteristics described in connection with the embodiments can be included in at least one embodiment of the present application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0030] In the description of the embodiments of the present application, the term "and / or" is merely a description of the association relationship between associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this text generally represents an "or" relationship between the associated objects before and after.

[0031] To solve the problems of poor precious metal recovery effect, complex process flow, and environmental pollution in the existing lead-bearing heavy sand smelting process, the present application provides an electrochemical pretreatment method for lead-bearing heavy sand. Through two-step electrolysis, first, electrolyze NaCl to oxidize galena in the lead-bearing heavy sand to generate lead chloride and elemental sulfur, and then electrolyze manganese salt to oxidize metal sulfides in the lead-bearing heavy sand to complete the pretreatment of the lead-bearing heavy sand. By regulating the concentration ratio of NaCl and manganese salt in the electrolyte and the voltage in the two-step electrolysis, the present invention can perform step-by-step electrolysis to sequentially achieve the reduction of lead and the oxidation of metal sulfides in the lead-bearing heavy sand. The pretreatment method of the present invention can not only realize the resource recovery of lead, but also remove its internal sulfides, providing qualified products for the subsequent gold smelting. This method has a short process flow, convenient operation, simple equipment, and is environmentally friendly, providing a very valuable technical solution for the field of precious metal hydrometallurgy. 2+ The pretreatment method of the present invention can not only realize the resource recovery of lead, but also remove its internal sulfides, providing qualified products for the subsequent gold smelting. This method has a short process flow, convenient operation, simple equipment, and is environmentally friendly, providing a very valuable technical solution for the field of precious metal hydrometallurgy.

[0032] The present application provides an electrochemical pretreatment method for lead-bearing heavy sand, comprising the following steps: S1. Grind the lead-bearing heavy sand finely, add it to an electrolytic cell filled with an electrolyte, stir evenly, perform a first pH adjustment, perform a first electrolysis, and then perform a first solid-liquid separation to obtain a solid tail residue and a filtered electrolyte; S2. Cool the filtered electrolyte to obtain lead chloride and the electrolyte after lead precipitation; S3. Mix the solid tail residue and the electrolyte after lead precipitation, stir evenly, perform a second pH adjustment, perform a second electrolysis, and then perform a second solid-liquid separation and washing to obtain a gold-rich residue.

[0033] In the technical solution of the embodiment of the present application, through two-step electrolysis, first electrolyze NaCl to oxidize galena in the lead-bearing heavy sand to generate lead chloride and elemental sulfur, and then electrolyze the manganese salt to oxidize the metal sulfide in the lead-bearing heavy sand to complete the pretreatment of the lead-bearing heavy sand. By regulating the concentration ratio of NaCl and manganese salt in the electrolyte and the voltage in the two-step electrolysis, the present invention can make NaCl and Mn 2+ be electrolyzed step by step to sequentially realize the reduction of lead and the oxidation of metal sulfide in the lead-bearing heavy sand. The pretreatment method of the present invention can not only realize the resource recovery of lead, but also remove the internal sulfide therein, providing qualified products for the subsequent gold smelting.

[0034] Further, in some embodiments, in step S1, the electrolytes in the electrolyte of the first electrolysis include sodium chloride and / or potassium chloride, MnCl2 and / or MnSO4; the concentration of the sodium chloride and / or potassium chloride is 40-300 g / L, and the concentration of the MnCl2 and / or MnSO4 is 5-20 g / L.

[0035] In the technical solution of the embodiment of the present application, by controlling the concentration of each electrolysis in the electrolyte and combining with the voltage of the subsequent first electrolysis, the electrolysis of NaCl occurs first in the system to generate sodium hypochlorite.

[0036] Further, in some embodiments, in step S1, the voltage of the first electrolysis is 1.5-3 V, and the electrolysis time is 3-6 h.

[0037] In the technical solution of the embodiment of the present application, through specific electrolysis voltage and electrolysis time, galena in the heavy sand reacts with the hypochlorite generated by the electrolysis of NaCl at 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.

[0038] Further, in some embodiments, in step S3, the voltage of the second electrolysis is 6-15 V, and the electrolysis time is 1-5 h.

[0039] In the technical solution of the embodiment of the present application, as the electrolysis of the electrolyte NaCl in the electrolyte is completed, the second electrolysis voltage is applied to electrolyze Mn in the electrolyte 2+ to generate manganese dioxide.

[0040] Further, in some embodiments, in step S1, the pH value regulator for the first pH value adjustment is hydrochloric acid, and the pH value for the first pH value adjustment is 1-2.

[0041] In the technical solution of the embodiment of the present application, under this pH value condition, the solubility of galena is better, which is convenient for subsequent electrolysis.

[0042] Further, in some embodiments, in step S1, the fine grinding means that the grinding fineness is 60-90% of -0.074 mm.

[0043] In the technical solution of the embodiment of the present application, by grinding the ore to a specific fineness, the effect of removing impurities in the subsequent electrolysis is better.

[0044] Further, in some embodiments, in step S1, the mass concentration of lead-bearing placer in the electrolytic cell is 5-40%.

[0045] Further, in some embodiments, in step S3, the pH regulator for the second pH adjustment is hydrochloric acid or sulfuric acid, and the pH value for the second pH adjustment is 1-2.

[0046] In the technical solution of the embodiment of the present application, the manganese dioxide generated by electrolysis reacts with sulfide minerals under acidic conditions, causing the sulfide minerals to oxidize and dissolve, while the manganese dioxide is reduced back to Mn 2+ , forming a cycle.

[0047] Further, in some embodiments, in step S1, the method for the first solid-liquid separation is hot filtration.

[0048] In the technical solution of the embodiment of the present application, through hot filtration, during the filtration process, lead chloride in the electrolyte is prevented from precipitating as the temperature decreases.

[0049] Further, 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.

[0050] In the technical solution of the embodiment of the present application, a suitable electrolytic material can make the electrolysis reaction proceed smoothly.

[0051] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application and should not be construed as a limitation of the present application. For those not specified in the embodiments regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in the field or according to the product specifications. For reagents or instruments not specified as to the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0052] Example 1 This embodiment provides a method for electrochemically pretreating lead-bearing placer, which specifically includes the following steps: (1) Grind the heavy sand finely until the mass content of -0.074 mm accounts for 60%. Add the electrolyte containing 180 g / L sodium chloride and 10 g / L manganese chloride into a PP electrolytic cell with a ruthenium-plated titanium plate as the anode and a titanium mesh as the cathode. The mass concentration of the pulp in the electrolytic cell is 5%. Adjust the pH of the pulp to 2 with hydrochloric acid. Apply a voltage of 2 V between the anode and the cathode and electrolyze for 6 hours under stirring. Then conduct hot filtration to obtain solid tailings and the filtered electrolyte.

[0053] (2) Cool the filtered electrolyte to obtain lead chloride and the electrolyte after lead precipitation.

[0054] (3) Mix the solid tailings and the electrolyte after lead precipitation and add them into the electrolytic cell. After stirring evenly, adjust the pH of the mixture to 2 with hydrochloric acid. Apply a voltage of 10 V between the anode and the cathode and electrolyze for 5 hours under stirring. Then conduct filtration and washing to obtain gold-rich slag.

[0055] The sources and performance parameters of the raw materials are as follows: All the raw materials used are heavy sand products produced by a domestic mining enterprise. The main metal element contents are shown in Table 1. Among them, 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.

[0056] Table 1 Main element contents in heavy sand Examples 2 - 3 and Comparative Examples 1 - 2 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 lies in the dosage of the electrolyte in step (1). The dosages of the electrolyte corresponding to each example and comparative example are shown in Table 2. Other steps are substantially the same as those in Example 1 and will not be elaborated here.

[0057] Table 2 Dosages of the electrolyte in Examples 2 - 3 and Comparative Examples 1 - 2 Examples 4 - 5 and Comparative Examples 3 - 4 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 lies in the electrolysis voltage in step (1). The electrolysis voltages corresponding to each example and comparative example are shown in Table 3. Other steps are substantially the same as those in Example 1 and will not be elaborated here.

[0058] Table 3 Electrolysis voltages in step (1) of Examples 4 - 7 and Comparative Examples 3 - 6 Examples 6 - 7 and Comparative Examples 5 - 6 Examples 6 - 7 and Comparative Examples 5 - 6 respectively provide a method for electrochemically pretreating lead - containing heavy sand. Compared with Example 1, the difference lies in the different electrolysis voltages in step (3). The electrolysis voltages corresponding to each example and comparative example are shown in Table 4. Other steps are substantially the same as those in Example 1 and will not be elaborated here.

[0059] Table 4 Electrolysis Voltages in Step (3) of Examples 6 - 7 and Comparative Examples 5 - 6 The purity of lead chloride precipitated in step (2), 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 in Examples 1 - 7 and Comparative Examples 1 - 6 were respectively analyzed, and the results are shown in Table 5.

[0060] Table 5 Purity of Precipitated Lead Chloride, Removal Effect of Impurity Elements in the Final Gold - Rich Slag, Yield of the Gold - Rich Slag, and Recovery Rate of Gold in Examples 1 - 7 and Comparative Examples 1 - 6 It can be seen from Examples 1 - 7 that in the solution of this application, the recovery rate of gold is relatively high, the oxidation and removal rate of sulfur is above 97%, the dissolution rate of lead is above 99%, and the removal rates of iron and copper also achieve good effects; it can be seen from Comparative Examples 1 - 2 that when the concentrations of the electrolytes sodium chloride and manganese chloride in the electrolyte decrease, the overall removal effect of impurity elements becomes worse, resulting in an increase in the slag yield and affecting the subsequent smelting effect; it can be seen from Comparative Examples 3 - 4 that when the electrolysis voltage in step (1) is too large, due to the overflow of chlorine gas generated by electrolysis, the oxidation effect of sulfides is affected, resulting in a decrease in the removal rate of impurity elements and an increase in the slag output. When the electrolysis voltage in step (1) is too small, the amount of hypochlorite generated by electrolysis decreases, resulting in a decrease in the removal rate of impurity elements and an increase in the slag output, affecting the pretreatment effect; it can be seen from Comparative Examples 5 - 6 that when the electrolysis voltage in step (3) is too large, side reactions increase, affecting the formation of manganese oxide, and further reducing the removal effect of sulfides. When the electrolysis voltage in step (3) is too small, the rate of manganese oxide formation becomes slower, affecting the impurity removal effect.

[0061] In summary, this application provides a method for electrochemically pretreating lead - containing heavy sand. Through two - step electrolysis, first electrolyze NaCl to reduce galena in the lead - containing heavy sand to lead chloride, and then electrolyze the manganese salt to oxidize metal sulfides in the lead - containing heavy sand, completing the pretreatment of the lead - containing heavy sand. By regulating the concentration ratio of NaCl and manganese salt in the electrolyte and the voltages in the two - step electrolysis, this invention can make NaCl and Mn 2+Stepwise electrolysis is carried out to successively achieve the reduction of lead in the lead-bearing heavy sand and the oxidation of metal sulfides. The pretreatment method of the present invention can not only realize the resource recovery of lead, but also remove the internal sulfides therein, providing qualified products for the subsequent gold smelting. This method has a short process, convenient operation, simple equipment and is environmentally friendly, providing a very valuable technical solution for the field of hydrometallurgy of precious metals.

[0062] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments with the same composition and the same effect as the technical idea within the scope of the technical solution of this application are included in the technical scope of this application. In addition, within the scope of not departing from the main idea of this application, various deformations that can be thought of by those skilled in the art are applied to the embodiments, and other ways constructed by combining some of the constituent elements in the embodiments are also included in the scope of this application.

Claims

1. An electrochemical pretreatment method for lead-containing heavy sand, characterized in that, It includes the following steps: S1. Fine grind the lead-bearing heavy sand, add it to an electrolytic cell filled with electrolyte, stir evenly, perform the first pH adjustment, conduct the first electrolysis, and then perform the first solid-liquid separation to obtain solid tailings and filtered electrolyte; S2. Cool the filtered electrolyte to obtain lead chloride and the electrolyte after lead precipitation; S3. Mix the solid tailings and the electrolyte after lead precipitation, stir evenly, perform the second pH adjustment, conduct the second electrolysis, and then perform the second solid-liquid separation and washing to obtain gold-rich slag.

2. The electrochemical pretreatment method of lead-bearing heavy sand according to claim 1, wherein In step S1, the electrolytes in the electrolyte for the first electrolysis include sodium chloride and / or potassium chloride, MnCl2 and / or MnSO4; the concentration of the sodium chloride and / or potassium chloride is 40 - 300 g / L, and the concentration of the MnCl2 and / or MnSO4 is 5 - 20 g / L.

3. The electrochemical pretreatment method of lead-bearing heavy sand according to claim 1, characterized in that, In step S1, the voltage for the first electrolysis is 1.5 - 3 V, and the electrolysis time is 3 - 6 h.

4. The electrochemical pretreatment method for lead-bearing heavy sand according to claim 2, wherein In step S3, the voltage for the second electrolysis is 6 - 15 V, and the electrolysis time is 1 - 5 h.

5. The electrochemical pretreatment method for lead-containing heavy sand according to claim 1, wherein In step S1, the pH regulator for the first pH adjustment is hydrochloric acid, and the pH value for the first pH adjustment is 1 - 2.

6. The electrochemical pretreatment method for lead-bearing heavy sand according to claim 1, characterized in that, In step S1, the fine grinding means that the grinding fineness of -0.074 mm accounts for 60 - 90%.

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

8. The electrochemical pretreatment method for lead-bearing heavy sand according to claim 1, wherein, In step S3, the pH regulator for the second pH adjustment is hydrochloric acid or sulfuric acid, and the pH value for the second pH adjustment is 1 - 2.

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

10. The electrochemical pretreatment method for lead-bearing heavy sand according to claim 1, wherein 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-coated titanium plate or ruthenium-coated titanium mesh, and the material of the cathode is one of titanium plate, titanium mesh or graphite.

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