Process for strengthening leaching of low-grade manganese ore by using tea polyphenol as reducing agent

Abstract

The invention discloses a process for strengthening leaching of low-grade manganese ore by using tea polyphenol as a reducing agent, which comprises the following steps: (1) carrying out primary treatment, crushing manganese ore powder, levigating and screening to required particle size; (2) sulfuric acid is added into the ground raw materials for acid treatment, and manganese mineral powder and a sulfuric acid solution are uniformly dispersed through ultrasonic dispersion; and (3) adding tea polyphenol into the manganese mineral powder sulfuric acid dispersion liquid, carrying out a reduction reaction in a high-pressure reaction kettle to obtain a stable manganese mineral powder dispersion liquid, carrying out operations such as centrifugal filtration and the like to obtain a leachate, diluting the filtrate, and testing the manganese content by using a flame atomic absorption spectrometry. The method has the advantages that the reducing agent is green, pollution-free and wide in source, and the preparation process is simple, safe and rapid; under the conditions of an acid medium and a hydrothermal reaction, the reaction rate of the tea polyphenol serving as a reducing agent and the manganese ore is higher, the leaching efficiency is higher, equipment is simple, operation is convenient, environment friendliness is achieved, and good application prospects are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of reducing low-grade manganese ore, and specifically relates to a process for strengthening the leaching of low-grade manganese ore by using tea polyphenols as a reducing agent. Background Art

[0002] Manganese is an important strategic resource and is widely used in metallurgy, chemical industry, batteries and other fields. Manganese mainly exists in various manganese ores in the form of manganese dioxide. With the large-scale exploitation and utilization of manganese mineral resources, the reserves of high-grade manganese ore resources in my country have sharply decreased, resulting in the production of manganese-based new energy materials mainly based on low-grade manganese ore. However, most low-grade manganese ores are difficult to leach efficiently, and traditional smelting processes are difficult to achieve their efficient utilization. Therefore, it is urgent to develop green, efficient and economical new metallurgical technologies to solve the problem of efficient utilization of low-grade manganese ores and promote the green transformation of the manganese smelting industry. Because manganese dioxide exhibits extremely strong chemical stability in both acidic and alkaline environments, traditional acid leaching or alkali leaching methods are difficult to effectively dissolve it, resulting in huge challenges in the extraction of manganese.

[0003] At present, the reduction leaching technology of manganese ore can be roughly divided into roasting reduction leaching technology and direct reduction leaching technology according to the coupling mode of reduction and leaching process. The former adopts a two-step method, first roasting and reducing the manganese ore and the reducing agent under high temperature conditions, and then leaching the reduced product; the latter combines the reduction and leaching process into one, directly adding the reducing agent to the leaching agent to achieve the reduction and dissolution of manganese. The two approaches are as follows:

[0004] (1) Reduction roasting-leaching method, using reducing agents (such as C, CO, CH4, etc.) at high temperature [1] The tetravalent manganese (MnO2) in pyrolusite is reduced to low-valent divalent manganese (MnO or Mn), and the reduction product is leached with dilute sulfuric acid, so that manganese enters the solution in the form of soluble MnSO4. Compared with direct leaching, the reduction roasting pretreatment can significantly improve the leaching rate and selectivity of manganese. However, the reduction roasting process involves chemical reactions at high temperatures, which usually consumes a lot of energy. This high-temperature operation not only increases energy consumption, but also increases the production cost of the product; and harmful gases are produced during the reduction roasting process, which has a negative impact on the environment; the by-products produced during the reduction roasting process sometimes interfere with subsequent leaching steps.

[0005] (2) Direct reduction leaching method: The principle of direct reduction leaching of pyrolusite is: based on the tetravalent manganese (Mn 4+ ) has strong oxidizing properties under acidic conditions. By adding a reducing agent, under suitable conditions such as acidity, temperature, and ore-liquid ratio, tetravalent manganese can be reduced to divalent manganese ions (Mn 2+), thereby dissolving into the solution. Compared with the reduction roasting-leaching method, the direct reduction leaching method omits the pretreatment step of high-temperature roasting, can be implemented at room temperature and pressure, has a simpler process flow, and has lower energy consumption. However, due to the complex mineral composition and ore structure of manganese ore, there are problems such as low manganese leaching rate, poor selectivity, and many impurity elements in the direct leaching process. Therefore, it is necessary to conduct in-depth research on the leaching process mechanism, optimize the leaching process, and develop new reducing agents and leaching systems, in order to further improve the leaching rate and selectivity of manganese, reduce energy consumption, and achieve clean and efficient smelting.

[0006] Biomass reduction leaching technology is an emerging hydrometallurgical method and belongs to direct reduction leaching technology. It has the advantages of being environmentally friendly, low cost, and simple process. However, there are many types of biomass and the composition is complex and changeable, which makes the reduction leaching process difficult to control, limiting the large-scale application of this technology. In order to overcome the above difficulties and realize the efficient utilization of low-grade manganese ore resources, the present invention has developed a new type of low-grade manganese ore reduction leaching technology: using tea polyphenols in biomass tea as a biomass reducing agent, because of its unique reducing properties, it is expected to overcome the above difficulties. Compared with the reduction roasting-leaching method, this method does not require high-temperature pretreatment and can be carried out at room temperature and pressure. The process has low energy consumption and low cost, and has obvious advantages; tea polyphenols can not only effectively reduce manganese ore, but also because of its biodegradability and environmental friendliness, it is considered to be a safe and sustainable reducing agent; other direct reduction leaching methods, such as Li Chaozhu et al. [2] Using pyrite as a reducing agent, Zheng Yu et al. [3] Although the leaching efficiency can reach more than 98% when pyrite is used as a reducing agent, other impurities generated in the process are not conducive to subsequent purification, and the reduction produces harmful gases that pollute the environment. In addition, it is restricted by the volume effect phenomenon, and appropriate measures need to be taken to reduce the hindering effect of the sulfide film on leaching. Compared with these methods, the present invention uses tea polyphenols as a reducing agent in a sulfuric acid medium to efficiently leach manganese from low-grade manganese through a hydrothermal reaction. Under the hydrothermal reaction conditions, the reaction rate of tea polyphenols with manganese ore is faster, the leaching efficiency is higher, and the equipment is simple and easy to operate, which has good application prospects. In addition, tea polyphenols will not introduce additional impurities during the reduction process, which simplifies the subsequent purification steps, and the process is simple and easy to promote and use, which has obvious advantages.

[0007] References:

[0008] [1] Zhang Hanquan, Zhang Pengfei, Xu Xin. Current status of comprehensive utilization of high iron manganese oxide ore and development of reduction roasting [J]. Comprehensive Utilization of Mineral Resources, 2023, 44(02): 141-149, 176.

[0009] [2] Li Chaozhu, Chen Yanhui. Study on the process of preparing manganese sulfate by direct leaching of low-grade pyrolusite[J]. Guangdong Chemical Industry, 2014, 41(19): 24-25, 29.

[0010] [3] Zheng Yu, Li Bingzhen, Liu Changgen, et al. Experimental study on synergistic leaching of pyrolusite-pyrite[J]. Mining and Metallurgical Engineering, 2022, 42(05): 103-105,110. Summary of the invention

[0011] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a process for enhancing the leaching of low-grade manganese ore using tea polyphenols as a reducing agent, thereby solving the problems of difficulty in leaching and extraction of low-grade manganese ore, high energy consumption, environmental pollution, high cost and complexity caused by by-products in the process, and providing a solution for the effective utilization of low-grade manganese ore resources.

[0012] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0013] A process for enhancing the leaching of low-grade manganese ore by using tea polyphenols as a reducing agent comprises the following steps:

[0014] (1) After preliminary physical treatment, the manganese ore powder is crushed, ground and sieved to a desired particle size for later use;

[0015] (2) adding sulfuric acid to the ground raw material for acid treatment, and uniformly dispersing the manganese ore powder and the sulfuric acid solution by ultrasonic dispersion to obtain a stable manganese ore powder sulfuric acid dispersion;

[0016] (3) Tea polyphenols are used as a reducing agent, and the reducing agent is added to a sulfuric acid dispersion of manganese ore powder. A reduction reaction is carried out in a reactor to reduce manganese from tetravalent to divalent and dissolve in the solution. A leaching solution is obtained by centrifugal filtration, and the filtrate is diluted and tested for manganese content by flame atomic absorption spectrometry.

[0017] Furthermore, tea polyphenols are used as a reducing agent in a sulfuric acid medium to efficiently leach manganese from low-grade manganese ore through a hydrothermal reaction.

[0018] Preferably, the particle size of the manganese ore powder described in step (1) is distributed in the range of 62-74 μm.

[0019] Preferably, the concentration of sulfuric acid in step (2) is 0.5-3 mol / L.

[0020] Preferably, the ultrasonic time in step (2) is 30-50 min, and the ultrasonic power is 15-25 kHz.

[0021] Preferably, the reaction temperature in step (3) is 60-150° C., and the reaction time is 1-10 h.

[0022] More preferably, the reaction temperature is 95-130° C., and the reaction time is 2-6 h.

[0023] Preferably, in step (3), the mass ratio of tea polyphenols to manganese ore is (0.01-0.055):1.

[0024] More preferably, the mass ratio of tea polyphenols to manganese ore is (0.02-0.045):1.

[0025] Preferably, the liquid-to-solid ratio (L / S) in step (3) is 3-15.

[0026] Compared with the prior art, the breakthrough advantages of the present invention are not only reflected in the optimization of operating conditions and the significant reduction of costs, but also in its profound contribution to environmental protection and the significant improvement of process efficiency and purity, which are specifically described as follows:

[0027] (1) Easy operation and energy consumption innovation

[0028] The traditional reduction roasting-leaching method, as one of the mainstream technologies for manganese ore processing, relies on a high temperature and high pressure environment to achieve the reduction effect. This process not only consumes a lot of energy, but also requires complex equipment support and strict operation control. In contrast, the present invention abandons the cumbersome steps of high temperature pretreatment and realizes direct reduction and leaching at normal temperature and pressure, greatly simplifies the process flow and reduces energy consumption. This technological innovation not only reduces the operating costs of enterprises, but also reduces the safety hazards caused by high temperature operations, embodies the green production concept of energy conservation and emission reduction, and is of great significance for promoting the sustainable development of the mining industry.

[0029] (2) Introduction of environmentally friendly reducing agents

[0030] In the selection of reducing agents, the present invention abandons the chemical substances that may produce harmful gases, such as C, CO, CH4, SO2, etc., which are commonly used in traditional methods. If these substances are not properly handled during the reduction process, they are very likely to emit pollutants such as sulfur dioxide and carbon monoxide, which pose a serious threat to the environment, such as aggravating the formation of acid rain and promoting the global greenhouse effect. As a natural product, tea polyphenols have unique biodegradability and environmental friendliness. While effectively reducing manganese ore, it avoids the generation of harmful gases and ensures the cleanliness and environmental protection of the production process. This transformation is not only a powerful response to the pollution problem of traditional industries, but also a solid step towards green chemistry and circular economy.

[0031] (3) Efficient leaching and improved purity

[0032] Faced with the complex mineral composition and ore structure of manganese ore, traditional leaching methods often find it difficult to balance high leaching rate and low impurity content, resulting in uneven product quality. The core of the present invention is to use tea polyphenols as a reducing agent. Its unique chemical properties make it almost impossible to introduce any foreign impurities during the reduction process, thereby greatly simplifying the subsequent purification steps and reducing production costs. More importantly, under the most optimized experimental conditions, the leaching efficiency of manganese ore is as high as 98.17%. This data not only far exceeds the traditional method, but also demonstrates the outstanding ability of the present invention in improving resource utilization and promoting efficient resource conversion. In addition, the output of high-purity manganese products also provides more high-quality raw materials for the downstream deep processing industry, promoting the upgrading and optimization of the entire industrial chain.

[0033] In summary, the emergence of the present invention is not only a major innovation in traditional manganese ore processing technology, but also a profound practice of environmental protection concepts and efficient production concepts. Its significant advantages in simplifying processes, reducing energy consumption, protecting the environment, and improving efficiency and purity have undoubtedly injected new vitality into the sustainable development of the manganese ore processing industry, demonstrating the key role of scientific and technological innovation in promoting industrial transformation and upgrading. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the effect of the mass ratio of tea polyphenols to manganese ore on manganese leaching rate;

[0035] Figure 2 This is the effect of L / S on the leaching rate of low-grade manganese ore;

[0036] Figure 3 This is the effect of sulfuric acid concentration on the leaching rate of low-grade manganese ore;

[0037] Figure 4 This is the effect of leaching temperature on the leaching rate of low-grade manganese ore;

[0038] Figure 5 This is the effect of leaching time on the leaching rate of low-grade manganese ore;

[0039] Figure 6 This is the X-ray diffraction (XRD) pattern of manganese ore before leaching;

[0040] Figure 7 This is the X-ray diffraction (XRD) pattern of manganese ore after leaching. DETAILED DESCRIPTION

[0041] In order to enable those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of this application.

[0042] In an embodiment of the present invention, a process for enhancing the leaching of low-grade manganese ore by using tea polyphenols as a reducing agent comprises the following steps:

[0043] (1) After preliminary physical treatment, the manganese ore powder is crushed, ground and sieved to a desired particle size for later use;

[0044] (2) adding sulfuric acid to the ground raw material for acid treatment, and uniformly dispersing the manganese ore powder and the sulfuric acid solution by ultrasonic dispersion to obtain a stable manganese ore powder sulfuric acid dispersion;

[0045] (3) Tea polyphenols are used as a reducing agent, and the reducing agent is added to a sulfuric acid dispersion of manganese ore powder. A reduction reaction is carried out in a high-pressure reactor to reduce manganese from tetravalent to divalent and dissolve in the solution. A leaching solution is obtained by centrifugal filtration and the filtrate is diluted and tested for manganese content by flame atomic absorption spectrometry.

[0046] The manganese ore powder described in step (1) has a particle size distribution of 62-74 μm.

[0047] The concentration of sulfuric acid in step (2) is 0.5-3 mol / L.

[0048] The ultrasonic time in step (2) is 30-50 min, and the ultrasonic power is 15-25 kHz.

[0049] The reaction temperature in step (3) is 60-150° C. and the reaction time is 1-10 h.

[0050] The mass ratio of tea polyphenols to manganese ore in step (3) is (0.01-0.055):1.

[0051] The liquid-to-solid ratio (L / S) in step (3) is 3-15.

[0052] Technical principle of the present invention:

[0053] In this innovative process of using tea polyphenols as a reducing agent to reduce low-grade manganese ore, each step and the raw materials involved play an indispensable role. Through precise synergy, they jointly promote the efficient leaching of manganese, achieving technological breakthroughs and performance improvements.

[0054] 1. Specific role and synergistic effect of raw materials

[0055] (1) Manganese ore powder: As the main body of the reaction, low-grade manganese ore powder is physically refined and sieved to obtain a particle size distribution of 62 to 74 μm, ensuring the uniformity of the particles. This not only increases the contact area between the ore powder and the chemical reagent, but also promotes the effective mixing between the reactants, laying the foundation for the efficient subsequent chemical reaction. The high-valent manganese (such as MnO2) in the manganese ore powder is the main target to be reduced, and its abundant existence is the prerequisite for the reaction to proceed.

[0056] (2) Sulfuric acid: The addition of sulfuric acid provides the necessary acidic environment for the reaction system, which is the key to activating the reducing ability of tea polyphenols. Under acidic conditions, the phenolic hydroxyl groups in tea polyphenols are more easily ionized and release electrons, thereby enhancing their reducing ability. At the same time, sulfuric acid also promotes the dissolution of minerals in manganese ore powder, making it easier for manganese ions to transfer from the solid phase to the liquid phase, thereby increasing the leaching rate of manganese. The concentration control of sulfuric acid is crucial (the present invention has optimized the sulfuric acid concentration of 0.5-2 mol / l after many tests). Too high a concentration may lead to aggravated equipment corrosion, while too low a concentration is insufficient to fully activate the reaction system.

[0057] (3) Tea polyphenols: As a core reducing agent, tea polyphenols play a decisive role in reducing low-grade manganese ore due to its natural antioxidant, non-toxic and high-efficiency reducing properties. The phenolic hydroxyl groups in tea polyphenol molecules directly reduce high-valent manganese to low-valent manganese (Mn 2+ ), this process is not only green and environmentally friendly, but also avoids the environmental pollution problems that may be caused by traditional reducing agents. The synergistic effect of tea polyphenols and sulfuric acid further enhances the reduction effect and ensures the efficient leaching of manganese.

[0058] 2. The necessity and importance of raw material dosage control

[0059] Controlling the mass ratio of tea polyphenols to manganese ore powder is the key to optimizing reaction efficiency and economy. Although too high a dosage of tea polyphenols can increase the reduction rate, it will increase the cost; too low a dosage may lead to incomplete reduction and affect the leaching rate of manganese. Similarly, the selection of liquid-to-solid ratio (L / S) is also crucial, which directly affects the fluidity, mass transfer efficiency and quality of the final product of the reaction system. Reasonable control of these parameters can reduce energy consumption and cost while ensuring the reaction effect. After multiple tests, the present invention optimized and selected the mass ratio of tea polyphenols and manganese ore powder to be (0.02-0.045): 1, and the liquid-to-solid ratio (L / S) to be 3-9, achieving unexpected technical effects.

[0060] 3. Selection and optimization of process parameters

[0061] (1) Ultrasonic dispersion time and power: Ultrasonic dispersion not only accelerates the mixing of manganese ore powder and sulfuric acid solution, but also promotes the renewal of particle surface and improves the contact efficiency of reactants. Properly extending the ultrasonic time and increasing the ultrasonic power can help form a more stable manganese ore powder sulfuric acid dispersion, creating favorable conditions for subsequent reduction reactions. However, too long time and high power may also lead to increased energy consumption and equipment wear, so precise control is required. The present invention has optimized the ultrasonic time to 30-50 min and the ultrasonic power to 15-25 kHz after multiple tests.

[0062] (2) Reaction temperature and time: Under high temperature conditions, the reduction activity and reaction rate of tea polyphenols are significantly improved, but too high a temperature may lead to an increase in side reactions and even destroy the structure of tea polyphenols. Therefore, choosing an appropriate reaction temperature (60-105°C) and reaction time (1-4h) can ensure efficient reduction while controlling costs and safety risks. By optimizing these parameters, the best balance between reaction efficiency and economic benefits is achieved.

[0063] In summary, the present invention uses tea polyphenols as a reducing agent to strengthen the leaching of low-grade manganese ore, and achieves efficient and green leaching of manganese by finely controlling the amount of raw materials and optimizing process parameters. This innovation not only solves the problem of low-grade manganese ore resource utilization, but also provides a new idea for the sustainable development of the field of metal extraction.

[0064] In order to make the disclosure of the present invention more complete, it is described below through more specific embodiments.

[0065] Example 1

[0066] A process for enhancing the leaching of low-grade manganese ore by using tea polyphenols as a reducing agent comprises the following steps:

[0067] (1) The manganese ore sample was ground to a particle size of less than 74 μm, sulfuric acid with a concentration of 2 mol / l was added to the ore powder sample, and the mixture was stirred in a 60°C water bath to ensure sufficient mixing; the mixed solution was subjected to ultrasonic treatment with an ultrasonic power of 15 kHz and a dispersion time of 50 min.

[0068] (2) slowly adding tea polyphenols to the dispersion prepared in (1), wherein the mass ratio of tea polyphenols to manganese ore powder is 0.01:1; the liquid-to-solid ratio of the dispersion is 11:1; placing the stable dispersion in a high-pressure reactor for reduction leaching, the leaching temperature is 105° C., and the leaching time is 4 hours; after the reaction is completed, the product is centrifuged, filtered and washed, and the filtrate is diluted and tested for manganese content by flame atomic absorption spectrometry.

[0069] The reduction leaching test results are shown in Table 1.

[0070] Example 2

[0071] A process for enhancing the leaching of low-grade manganese ore by using tea polyphenols as a reducing agent comprises the following steps:

[0072] (1) The manganese ore sample was ground to a particle size of less than 74 μm, sulfuric acid with a concentration of 2 mol / l was added to the ore powder sample, and the mixture was stirred in a 60°C water bath to ensure sufficient mixing; the mixed solution was subjected to ultrasonic treatment with an ultrasonic power of 15 kHz and a dispersion time of 50 min.

[0073] (2) slowly adding tea polyphenols to the dispersion prepared in (1), wherein the mass ratio of tea polyphenols to manganese ore powder is 0.035:1; the liquid-to-solid ratio of the dispersion is 6:1; placing the stable dispersion in a high-pressure reactor for reduction leaching, the leaching temperature is 105° C., and the leaching time is 4 hours; after the reaction is completed, the product is centrifuged, filtered and washed, and the filtrate is diluted and tested for manganese content by flame atomic absorption spectrometry.

[0074] The reduction leaching test results are shown in Table 1.

[0075] Example 3

[0076] A process for enhancing the leaching of low-grade manganese ore by using tea polyphenols as a reducing agent comprises the following steps:

[0077] (1) The manganese ore sample was ground to a particle size of less than 74 μm, sulfuric acid with a concentration of 1 mol / l was added to the ore powder sample, and the mixture was stirred in a 60°C water bath to ensure sufficient mixing; the mixed solution was subjected to ultrasonic treatment with an ultrasonic power of 15 kHz and a dispersion time of 50 min.

[0078] (2) slowly adding tea polyphenols to the dispersion prepared in (1), wherein the mass ratio of tea polyphenols to manganese ore powder is 0.035:1; the liquid-to-solid ratio of the dispersion is 9:1; placing the stable dispersion in a high-pressure reactor for reduction leaching, the leaching temperature is 105° C., and the leaching time is 4 hours; after the reaction is completed, the product is centrifuged, filtered and washed, and the filtrate is diluted and tested for manganese content by flame atomic absorption spectrometry.

[0079] The reduction leaching test results are shown in Table 1.

[0080] Example 4

[0081] A process for enhancing the leaching of low-grade manganese ore by using tea polyphenols as a reducing agent comprises the following steps:

[0082] (1) The manganese ore sample was ground to a particle size of less than 74 μm, sulfuric acid with a concentration of 1 mol / l was added to the ore powder sample, and the mixture was stirred in a 60°C water bath to ensure sufficient mixing; the mixed solution was subjected to ultrasonic treatment with an ultrasonic power of 15 kHz and a dispersion time of 50 min.

[0083] (2) slowly adding tea polyphenols to the dispersion prepared in (1), wherein the mass ratio of tea polyphenols to manganese ore powder is 0.035:1; the liquid-to-solid ratio of the dispersion is 9:1; placing the stable dispersion in a high-pressure reactor for reduction leaching, the leaching temperature is 100° C., and the leaching time is 4 hours; after the reaction is completed, the product is centrifuged, filtered and washed, and the filtrate is diluted and tested for manganese content by flame atomic absorption spectrometry.

[0084] The results of mineral flotation tests are shown in Table 1.

[0085] Example 5

[0086] A process for enhancing the leaching of low-grade manganese ore by using tea polyphenols as a reducing agent comprises the following steps:

[0087] (1) The manganese ore sample was ground to a particle size of less than 74 μm, sulfuric acid with a concentration of 1 mol / l was added to the ore powder sample, and the mixture was stirred in a 60°C water bath to ensure sufficient mixing; the mixed solution was subjected to ultrasonic treatment with an ultrasonic power of 15 kHz and a dispersion time of 50 min.

[0088] (2) slowly adding tea polyphenols to the dispersion prepared in (1), wherein the mass ratio of tea polyphenols to manganese ore powder is 0.035:1; the liquid-to-solid ratio of the dispersion is 9:1; placing the stable dispersion in a high-pressure reactor for reduction leaching, the leaching temperature is 120° C., and the leaching time is 4 h; after the reaction is completed, the product is centrifuged, filtered and washed, and the filtrate is diluted and tested for manganese content by flame atomic absorption spectrometry.

[0089] The results of mineral flotation tests are shown in Table 1.

[0090] Comparative Example 1

[0091] The same raw material as the manganese ore powder in Example 1 was used. The particle size of the raw material after grinding was 50 μm. A reduction leaching experiment was carried out with fixed sulfuric acid concentration: 2 mol / L; liquid-solid ratio: 11:1; leaching temperature: 105°C; leaching time: 4 h. The difference was that the mass ratio of tea polyphenols to manganese ore powder was adjusted to 0.035:1. The leaching rate of manganese ore is shown in Table 1. The leaching rate of manganese ore is 95.83%. Compared with Example 1, the other conditions remain unchanged, but the mass ratio is changed. The manganese leaching rate changes significantly, indicating that the change in mass ratio affects the leaching of manganese ore. Figure 1In the single factor experiment shown in the figure, when the mass ratio of tea polyphenols to manganese ore is 3.5%, the leaching rate of manganese is close to the maximum value, which may be attributed to two main reasons: first, most of the soluble manganese has been reduced and dissolved, and the residual insoluble manganese ore is difficult to react further; second, due to the constraints of kinetic conditions such as reaction area, temperature, and acid concentration, continuing to increase the amount of reducing agent cannot effectively improve the leaching rate, and the effective reduction sites have been fully utilized. Considering that too high an addition ratio will increase the difficulty of subsequent solid-liquid separation, for the leaching process of low-grade manganese ore, controlling the mass ratio of tea polyphenols to manganese ore at 3.5% is the best choice.

[0092] Comparative Example 2

[0093] The same raw material as the manganese ore powder in Example 2 was used. The particle size of the raw material after grinding was 50 μm. A reduction leaching experiment was carried out. The mass ratio of tea polyphenols to manganese ore was fixed at 0.035:1, the concentration of sulfuric acid was 2 mol / L, the leaching temperature was 105°C, and the leaching time was 4 h. The difference was that the liquid-solid ratio of the dispersion was adjusted to 9:1. The leaching rate of manganese ore is shown in Table 1. The leaching rate of manganese ore is 95.95%. Compared with Example 2, other conditions remain unchanged, but the liquid-solid ratio is changed. The manganese leaching rate changes significantly, indicating that the change in the liquid-solid ratio affects the leaching of manganese ore. Figure 2 In the single factor experiment shown, increasing the liquid-solid ratio can improve the leaching kinetics and promote the dissolution of manganese. However, when the liquid-solid ratio exceeds 9, the leaching rate increase is significantly reduced, and the effect of increasing the liquid-solid ratio tends to be saturated. Weighing the leaching effect and economy, a liquid-solid ratio of 9 is determined to be the optimal process condition.

[0094] Comparative Example 3

[0095] The raw material consistent with the manganese ore powder in Example 3 was used. The particle size of the raw material after grinding was 50 μm. A reduction leaching experiment was carried out. The mass ratio of tea polyphenols to manganese ore was fixed at 0.035:1, the liquid-solid ratio was maintained at 9:1, the leaching temperature was maintained at 105°C, and the leaching time was fixed at 4 hours. The difference was that the sulfuric acid concentration was adjusted to 1.5 mol / l. The manganese ore leaching rate is shown in Table 1, and the manganese ore leaching rate is 96.78%. Compared with Example 3, other conditions remain unchanged, and the manganese leaching rate changes significantly when the sulfuric acid concentration is changed, indicating that the change in sulfuric acid concentration affects the leaching of manganese ore. Figure 3 In the single factor experiment shown in the figure, the manganese leaching rate increased significantly with the increase of sulfuric acid concentration. When the sulfuric acid concentration reached 1.5 mol / L, the manganese leaching rate reached a maximum of 96.78%. However, when the sulfuric acid concentration was further increased to above 2 mol / L, the leaching rate decreased slightly. This may be due to the high H + concentration has a destructive effect on the reducing agent, resulting in the reduction of Mn 2+The leaching reaction is inhibited by oxidation. In addition, too high acid concentration may increase the viscosity of the system, trigger side reactions, and further affect the leaching effect. Taking into account factors such as leaching rate, cost, reducing agent stability, system viscosity, and side reaction control, the experiment determined that the sulfuric acid concentration of 1.5 mol / L was the optimal process condition.

[0096] Comparative Example 4

[0097] The same raw material as the manganese ore powder in Example 4 was used. The particle size of the raw material after grinding was 50 μm. A reduction leaching experiment was carried out. The mass ratio of tea polyphenols to manganese ore was fixed at 0.035:1, the liquid-solid ratio (L / S) was maintained at 9:1, the sulfuric acid concentration was constant at 1.5 mol / L, and the leaching time was kept unchanged at 4 hours. The difference was that the leaching temperature was adjusted to 120°C. The leaching rate of manganese ore is shown in Table 1, and the leaching rate of manganese ore is 97.87%. Compared with Example 4, other conditions remain unchanged, and the leaching temperature is changed. The manganese leaching rate changes significantly, indicating that the change in leaching temperature affects the leaching of manganese ore. Figure 4 In the single factor experiment shown in the figure, as the temperature increases from 60°C to 105°C, the leaching rate of manganese increases significantly from 76.23% to 96.78%. This phenomenon can be explained by the reaction kinetics theory: the increase in temperature leads to an increase in solubility, a decrease in the thickness of the diffusion layer, an acceleration of molecular motion, an increase in the number of activated molecules, and a decrease in the viscosity of the liquid phase. The combined effect of these factors accelerates the leaching rate. When the temperature continues to rise to 120°C, the leaching rate of manganese slowly rises to a maximum value of 97.87%. However, after exceeding 120°C, the leaching rate shows a downward trend and tends to be flat after 130°C. This phenomenon may be related to the decrease in the thermal stability of tea polyphenols. At moderate temperatures, tea polyphenols can effectively promote the reduction leaching of manganese. However, under high temperature conditions, these active components may be over-oxidized, accompanied by the pyrolysis of high molecular weight organic matter, and the generated secondary biomass may weaken the reduction effect of tea polyphenols, and even form complex compounds that inhibit the leaching of manganese. Taking into account the leaching rate and the stability of tea polyphenols, the present invention determines 120°C as the optimal leaching temperature.

[0098] Comparative Example 5

[0099] The same raw material as the manganese ore powder in Example 5 was used. The particle size of the raw material after grinding was 50 μm. A reduction leaching experiment was carried out. The mass ratio of tea polyphenols to manganese ore was fixed at 0.035:1, the liquid-solid ratio (L / S) was maintained at 9:1, the sulfuric acid concentration was constant at 1.5 mol / L, and the leaching temperature was kept at 120°C. The difference was that the leaching time was adjusted to 2 hours. The leaching rate of manganese ore is shown in Table 1, and the leaching rate of manganese ore is 94.83%. Compared with Example 5, other conditions remain unchanged, and the leaching time is changed. The manganese leaching rate changes significantly, indicating that the change in leaching time affects the leaching of manganese ore. Figure 5As shown in the single factor experiment, the leaching rate of manganese shows a trend of first rising rapidly and then slowly tending to equilibrium as the leaching time increases. In the early stage of leaching (1-2 hours), the leaching rate of manganese rises sharply from 84.66% to 94.83%, indicating that at this stage, the extension of leaching time has a significant effect on improving the leaching rate of manganese. As the leaching time is further extended, the rising rate of manganese leaching rate gradually slows down. When the leaching time reaches 4 hours, the manganese leaching rate reaches a maximum value of 97.87%. Taking into account the leaching efficiency and energy consumption, the optimal leaching time is determined to be 4 hours.

[0100] Take two groups of 1g manganese ore samples and add a certain amount of sulfuric acid and tea polyphenols respectively. When sulfuric acid is used alone as the leaching agent, the leaching rate of manganese ore is low, and the leaching rate of manganese ore is only 25.47% as shown in Table 2. This shows that in the absence of a reducing agent, it is difficult to effectively dissolve manganese ore with sulfuric acid alone; when tea polyphenols are used alone as a reducing agent, the leaching rate of manganese ore is even lower, and the leaching rate of manganese ore is only 7.43% as shown in Table 2. This shows that under non-acidic conditions, tea polyphenols cannot effectively promote the dissolution of manganese ore.

[0101] Based on the results of the single factor experiment, it was found that the mass ratio of tea polyphenols to manganese ore had a significant effect on the manganese leaching rate. Further experiments determined that 3.5% was the optimal ratio. Then, sulfuric acid concentration, leaching temperature and leaching time were determined to be the key influencing factors in the manganese leaching process. In order to further optimize the leaching process, the Box-Behnken design was adopted, and three levels were selected for each factor. The factor level settings are shown in Table 3. Using Design Expert 13.0 software, with the manganese leaching rate as the response value, 17 experimental points were automatically generated through Box-Behnken design based on the selected factors and levels, including 12 factor points and 5 center points. According to the experimental design plan, leaching experiments were carried out at 17 experimental points, and each experimental point was repeated 3 times. The experimental results were averaged. The experimental data were analyzed for variance using Design Expert 13.0 software. According to the experimental data, the empirical relationship between the manganese leaching rate and the three factors was obtained by using the multivariate quadratic regression method: Y = 98.08 + 0.4413A-0.0363B + 0.0975C + 0.445A*B + 0.3775A*C-0.0425B*C-1.08A 2 -1.55B 2- 1.18C 2 .

[0102] Based on the established quadratic regression model, the numerical optimization function of Design Expert software was used to search for the optimal process parameter combination that can maximize the manganese leaching rate within the set factor range. The optimization goal was set to maximize the manganese leaching rate, and the range of the three factors was limited to the level of the experimental design. After calculation, the optimal process parameter combination was obtained as follows: sulfuric acid concentration 2.11 mol / L, leaching temperature 120.1℃, leaching time 4.08h. Under these conditions, the predicted manganese leaching rate was 98.13%, which was close to the experimental value.

[0103] In order to verify the stability of the optimized process, three repeated experiments were carried out under the conditions of the best process parameter combination. The experimental results are shown in Table 4. The verification experimental results show that under the optimized process conditions, the manganese leaching rate is 98.17% on average. The verification experimental results show that under the optimized process conditions, the manganese leaching rate is 98.17% on average, which is very close to the model prediction value of 98.13%, and the relative error is only 0.04%, indicating that the process parameter combination is reliable and the established regression model has good prediction ability.

[0104] Based on the results of response surface methodology optimization, the optimal process parameter combination for tea reduction leaching of manganese ore was obtained: the mass ratio of tea polyphenols to manganese ore was 3.5%, the concentration of sulfuric acid was 2.11 mol / L, the leaching temperature was 120.1℃, and the leaching time was 4.1h. Under these conditions, the manganese leaching rate could reach more than 98.17%, which was nearly 4 percentage points higher than the leaching rate under the initial process conditions.

[0105] See also Figure 6 and Figure 7 According to the X-ray diffraction (XRD) pattern analysis before and after leaching of manganese ore, the manganese in the manganese ore before leaching mainly exists in the form of MnO and Mn3O4, and also contains silicon dioxide (SiO2), ferric oxide (Fe2O3), aluminum oxide (Al2O3) and other components. After leaching, manganese oxide is no longer visible, and the manganese element in the ore is basically leached completely.

[0106] Table 1 Leaching rate of low-grade manganese ore reduced by tea polyphenols as a reducing agent

[0107] Test groups Leaching rate / % Sample Leaching rate / % Example 1 88.57 Comparative Example 1 95.83 Example 2 85.83 Comparative Example 2 95.95 Example 3 92.55 Comparative Example 3 96.78 Example 4 95.13 Comparative Example 4 97.87 Example 5 97.87 Comparative Example 5 94.83

[0108] Table 2 Leaching rate when sulfuric acid or tea polyphenols are used alone to leaching manganese ore

[0109] Leaching agent Leaching rate / % sulfuric acid 25.47 Tea polyphenols 7.43

[0110] Table 3 Experimental level factors

[0111]

[0112] Table 4 Verification experimental results

[0113]

[0114] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A process for enhancing the leaching of low-grade manganese ore using tea polyphenols as a reducing agent, characterized in that: (1) After preliminary physical treatment, the manganese ore powder is crushed, ground and sieved to a desired particle size for later use; (2) adding sulfuric acid to the ground raw material for acid treatment, and uniformly dispersing the manganese ore powder and the sulfuric acid solution by ultrasonic dispersion to obtain a stable manganese ore powder sulfuric acid dispersion; (3) Using tea polyphenols as a reducing agent, the reducing agent is added to a manganese ore powder sulfuric acid dispersion, and a reduction reaction is carried out in a reactor to obtain a stable manganese ore powder dispersion, and a leaching solution is obtained by centrifugal filtration. After the filtrate is diluted, the manganese content is tested by flame atomic absorption spectrometry.

2. A process for enhancing the leaching of low-grade manganese ore using tea polyphenols as a reducing agent according to claim 1, characterized in that: In the presence of sulfuric acid, tea polyphenols are used as a reducing agent to efficiently leach manganese from low-grade manganese ore through hydrothermal reaction.

3. A process for enhancing the leaching of low-grade manganese ore by using tea polyphenols as a reducing agent according to claim 1, characterized in that: The manganese ore powder described in step (1) has a particle size distribution of 62-74 μm.

4. A process for enhancing the leaching of low-grade manganese ore by using tea polyphenols as a reducing agent according to claim 1, characterized in that: The concentration of sulfuric acid in step (2) is 0.5-3 mol / L.

5. The process for enhancing the leaching of low-grade manganese ore by using tea polyphenols as a reducing agent according to claim 1, characterized in that: The ultrasonic time in step (2) is 30-50 min, and the ultrasonic power is 15-25 kHz.

6. The process for enhancing the leaching of low-grade manganese ore by using tea polyphenols as a reducing agent according to claim 1, characterized in that: The reaction temperature in step (3) is 60-150° C. and the reaction time is 1-10 h.

7. A process for enhancing the leaching of low-grade manganese ore using tea polyphenols as a reducing agent according to claim 6, characterized in that: The reaction temperature is 95-130° C., and the reaction time is 2-6 hours.

8. The process for enhancing the leaching of low-grade manganese ore by using tea polyphenols as a reducing agent according to claim 1, characterized in that: The mass ratio of tea polyphenols to manganese ore in step (3) is (0.01-0.055):

1.

9. A process for enhancing the leaching of low-grade manganese ore using tea polyphenols as a reducing agent according to claim 8, characterized in that: The mass ratio of tea polyphenols to manganese ore is (0.02-0.045):

1.

10. The process for enhancing the leaching of low-grade manganese ore by using tea polyphenols as a reducing agent according to claim 1, characterized in that: The liquid-to-solid ratio (L / S) in step (3) is 3-15.

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