A method for oxidizing and separating manganese and magnesium using manganese dioxide as a catalyst and preparing basic magnesium carbonate

Abstract

The present invention discloses a method for oxidatively separating manganese and magnesium by using manganese dioxide as a catalyst and preparing basic magnesium carbonate. First, a carbonization precipitant is added to the manganese-magnesium-containing solution to preferentially precipitate manganese ions, and manganese carbonate and filtrate A rich in magnesium ions are obtained by filtration; an oxidant and the catalyst manganese dioxide are added to filtrate A to catalytically oxidize the remaining divalent manganese ions and convert them into insoluble manganese dioxide, thereby realizing the efficient separation of manganese and magnesium in the filtrate. The manganese dioxide formed during the oxidation process forms a self-enhancing cycle, continuously providing catalytic activity, greatly improving the oxidation efficiency, reducing the catalyst dosage at the same time, and ensuring the stability of the oxidation reaction rate; a carbonization precipitant and an alkali are added to the treated filtrate, and through staged reactions, magnesium ions form high-purity basic magnesium carbonate precipitate. The process of the present invention realizes the efficient and selective separation of manganese and magnesium, and the recovered products have high added value and can be widely used in fields such as battery materials, catalysts, and flame retardant materials.

Description

Technical Field

[0001] The present invention relates to the technical field of comprehensive utilization of industrial by-products, and particularly to a method for oxidatively separating manganese and magnesium by using manganese dioxide as a catalyst and preparing basic magnesium carbonate. Background Art

[0002] In the manganese ore smelting process, usually rhodochrosite, pyrolusite, etc. are used as raw materials, and high-purity manganese-based material products are produced through steps such as acid leaching, purification, and electrolysis. During the acid leaching of manganese, manganese (Mn² + )and magnesium (Mg² + )ions dissolve into the acidic solution simultaneously, forming a mixed solution containing manganese and magnesium. In addition, smelting solutions, ore acidic leaching solutions, mine acidic wastewaters, and manganese and magnesium-containing waste liquors discharged from industries such as chemical engineering and battery material production also widely exist in industrial production processes. The manganese and magnesium ions in these solutions are extremely similar in physical and chemical properties, especially their solubilities are close in acidic systems, making it difficult for traditional separation methods to achieve efficient separation of the two, resulting in poor separation effects and low product purity, and the efficient recovery and comprehensive utilization of resources cannot be achieved.

[0003] Existing technologies such as chemical precipitation method, extraction method, ion exchange method, and sulfide precipitation method all have limitations. The chemical precipitation method is sensitive to pH value and temperature, has poor separation selectivity and is easy to introduce impurities; the extraction method has high costs and difficult solvent recovery; although the ion exchange method has high purity, it has large equipment investment and complex processes; the sulfide precipitation method has difficult-to-filter precipitates and high environmental risks. Some processes rely on concentrating and crystallizing to form double salts and landfilling, with high treatment costs and occupying land resources, and there are long-term potential environmental pollution hazards. Therefore, there is an urgent need to develop an efficient, economical, and environmentally friendly process for separating and recovering manganese and magnesium-containing waste liquors, which is applicable to the treatment of smelting by-products, ore acid leaching waste liquors, and industrial wastewaters, to achieve efficient separation and resource utilization of manganese and magnesium, produce high-value-added products, and meet the requirements of sustainable development. Summary of the Invention

[0004] Aiming at the technical problem that it is difficult to selectively separate manganese and magnesium in the prior art, the present invention provides a method for oxidatively separating manganese and magnesium by using manganese dioxide as a catalyst and preparing basic magnesium carbonate. Through a three-step process (manganese precipitation - catalytic oxidation for manganese removal - magnesium precipitation), the method utilizes the solubility difference and redox characteristics of manganese and magnesium ions to achieve efficient separation; the recovered products exist in high-purity forms and can be used to prepare high-value-added products such as manganese carbonate, manganese dioxide, and basic magnesium carbonate respectively; the process flow is simple, and it can significantly reduce waste liquid discharge and treatment costs.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A method for oxidizing and separating manganese and magnesium using manganese dioxide as a catalyst and preparing basic magnesium carbonate, comprising the following steps:

[0007] S1. Add an alkali to the manganese-magnesium-containing solution, adjust the pH to 5.5 - 7.5, and add a soluble carbonate as a carbonization precipitant to conduct a magnesium ion carbonization precipitation reaction. The reaction temperature is 20 - 50 °C, the reaction time is 0.5 - 2 h, and filter to obtain manganese carbonate and filtrate A;

[0008] S2. Add a catalyst and an oxidant to filtrate A obtained in step S1 to conduct a catalytic oxidation reaction. The reaction temperature is 10 - 40 °C, the reaction time is 0.5 - 6 h, and filter to obtain manganese dioxide (including the added catalyst and the manganese dioxide generated during the reaction) and filtrate B;

[0009] S3. Add a soluble carbonate as a carbonization precipitant to filtrate B obtained in step S2, and add an alkali to adjust the solution pH to 8.5 - 10.5. React in two stages. The first stage is a magnesium ion carbonization precipitation reaction, the temperature is 20 - 55 °C, the time is 1 - 4 h, and the second stage is the conversion of magnesium carbonate to basic magnesium carbonate, the temperature is 60 - 95 °C, the time is 2 - 8 h, and filter to obtain a filter residue and filtrate C;

[0010] S4. Wash and dry the filter residue obtained in step S3 to obtain basic magnesium carbonate.

[0011] To achieve the efficient separation of manganese and magnesium in the solution, the present invention proposes a technical solution of three-step treatment of manganese precipitation - catalytic oxidation for manganese removal - magnesium precipitation. Add a soluble carbonate as a carbonization precipitant to the manganese-magnesium-containing solution. Utilize the characteristic that the solubility product of manganese carbonate is less than that of magnesium carbonate under the condition of pH 5.5 - 7.5, so that manganese ions preferentially precipitate out in the form of manganese carbonate, thereby obtaining high-purity manganese carbonate solid and filtrate A rich in magnesium ions. Secondly, to further reduce the residual manganese ion concentration in filtrate A, add catalyst manganese dioxide and an oxidant, and oxidize divalent manganese (Mn 2+ )to high-valent manganese (Mn 4+ )through catalytic oxidation and precipitate out in the form of insoluble manganese oxides. After solid-liquid separation, filtrate B with extremely low manganese content and rich in magnesium ions is obtained. Add a soluble carbonate as a carbonization precipitant to filtrate B and add an alkali to adjust the solution pH to 8.5 - 10.5, and promote the formation of high-purity basic magnesium carbonate precipitate of magnesium ions through staged reaction. Through this three-step process, the efficient separation and resource recovery of manganese and magnesium are realized. The process operation is simple, the separation efficiency is high, and it is suitable for the separation and treatment of manganese and magnesium in complex systems.

[0012] Further, in step S1, the manganese- and magnesium-containing solution is an industrial waste liquid, a by-product of the smelting process, acidic mine wastewater, or a treatment liquid of other manganese- and magnesium-containing mixtures, especially a sulfate-type waste liquid generated during the smelting process, a manganese- and magnesium-containing waste acid liquid remaining in the metal smelting process, or a manganese- and magnesium-containing mixed waste liquid after ore acid leaching extraction.

[0013] Further, in steps S1 and S3, the base is one or more of sodium hydroxide, potassium hydroxide, and ammonia water, and the concentration is 0.25 - 2 mol / L.

[0014] Further, in step S1, the carbonization precipitant is one or more of potassium carbonate, sodium carbonate, potassium bicarbonate, sodium bicarbonate, ammonium bicarbonate, and ammonium carbonate. The concentration of the carbonization precipitant is 0.25 - 2 mol / L, and the addition amount is such that the molar ratio of the carbonization precipitant to the manganese ions in the solution is greater than or equal to 0.8, preferably 0.8 - 1.5:1.

[0015] In step S1, the chemical reaction equation for the carbonization precipitation reaction of magnesium ions is as follows:

[0016] ,

[0017] .

[0018] In step S1, the concentration of the carbonization precipitant should not exceed 2 mol / L. If the concentration is too high, the growth rate of manganese carbonate crystals will be too fast, forming larger crystals, which may wrap a small amount of magnesium ions, resulting in magnesium loss. If the addition amount of the carbonization precipitant is too small, the concentration of manganese ions in the filtrate will be too high, and the amount of oxidant in the subsequent catalytic oxidation manganese removal step will increase significantly. If added in excess, it will cause the pH value of the solution to rise, making it difficult to control within the range of 5.5 - 7.5. As a result, both manganese ions and magnesium ions will precipitate in the form of carbonates, affecting the separation efficiency.

[0019] Further, in step S2, the dosage of the catalyst manganese dioxide is 5 - 200 mg / L of filtrate A (5 - 200 mg of manganese dioxide is added per liter of filtrate A).

[0020] It should be noted that the catalyst here directly determines the final catalytic oxidation result. Even if manganese sesquioxide with relatively similar properties is used, although a certain catalytic effect can be achieved, the catalytic effect is far less than that of manganese dioxide.

[0021] The key reason for using manganese dioxide as the catalyst to oxidize the manganese ions in the solution is that directly using a peroxide oxidant cannot effectively oxidize Mn 2+ . Although Mn 2+The redox potential of / MnO2 is 1.69 V, and that of the peroxide oxidant is approximately 1.77 V. In theory, both meet the conditions for an oxidation-reduction reaction. However, due to the extremely slow reaction kinetics, low electron transfer rate, and high reaction activation energy, the actual reaction hardly occurs. In addition, the peroxide oxidant cannot directly generate highly reactive oxygen species (such as hydroxyl radicals •OH or superoxide radicals O2• - ), and these reactive species are the core of the efficient oxidation of Mn 2+ .

[0022] Introducing manganese dioxide as a catalyst, the catalyst can effectively improve the oxidation rate of Mn 2+ by reducing the reaction activation energy and promoting electron transfer. At the same time, the catalyst dosage can be maintained at a low concentration. The manganese dioxide generated during the reaction itself has catalytic activity and can partially replace the initial catalyst, further increasing the catalytic surface area and active sites, thus maintaining the high oxidation efficiency of the system. As the reaction progresses, the precipitation of manganese dioxide continues to form, enhancing the peroxide decomposition and the generation ability of highly reactive oxygen species (ROS), forming a self-enhancing cycle mechanism. Even with a low initial catalyst dosage, this cycle mechanism can ensure that the oxidation reaction maintains high efficiency and high rate in the later stage, significantly improving the overall performance of the oxidation treatment.

[0023] Furthermore, in step S2, the oxidant is at least one of magnesium peroxide, sodium peroxide, potassium peroxide, urea peroxide, sodium percarbonate, potassium percarbonate, hydrogen peroxide, and potassium peroxymonosulfate; the molar ratio of the oxidant to the manganese ions in filtrate A is greater than or equal to 1, preferably 1 - 1.5:1.

[0024] In step S2, the chemical reaction equation for the catalytic oxidation reaction is as follows:

[0025] The peroxide decomposes in an aqueous solution (taking metal peroxide as an example), where M represents a cation, such as Na + , Ca 2+ , Mg 2+ , etc., and the reaction formula is as follows:

[0026] ,

[0027] In this catalytic reaction, the surface active sites of MnO2 can cleave H2O2 to generate peroxy radicals (HO2·) and hydroxyl radicals (·OH), and the reaction formula is as follows:

[0028] ,

[0029] The peroxy radicals (HO2·) further react to generate superoxide anion radicals O2 - ·), and the reaction formula is as follows:

[0030] ,

[0031] Hydroxyl radicals have strong oxidizing properties and can oxidize Mn 2+ to form Mn 3+ . The reaction formula is as follows:

[0032] ,

[0033] In an aqueous solution, Mn 3+ tends to undergo a hydrolysis reaction to form a hydroxide. In this reaction system, MnO(OH) is easily oxidized and transformed into MnO2. The reaction formula is as follows:

[0034] ,

[0035] .

[0036] Further, in step S3, the carbonization precipitant is one or more of potassium carbonate, sodium carbonate, potassium bicarbonate, sodium bicarbonate, ammonium bicarbonate, and ammonium carbonate. The molar ratio of the carbonization precipitant to magnesium sulfate in filtrate B is 2 - 2.5:1.

[0037] Further, in steps S1 and S3, the carbonization precipitant is added in the form of a solid directly added or prepared into a solution and then added. In step S1, it is preferably added in the form of a prepared solution, and in step S3, it is preferably added as a solid directly.

[0038] In step S3, the first stage is the carbonization precipitation reaction of magnesium ions. The chemical reaction equation is as follows:

[0039] ,

[0040] ,

[0041] The second stage is the conversion of magnesium carbonate to basic magnesium carbonate. The chemical reaction equation is as follows:

[0042] .

[0043] The amount of the carbonization precipitant added in step S3 is slightly greater than the theoretical demand of magnesium sulfate to ensure complete precipitation of magnesium ions. During the process of the first-stage reaction, alkali is continuously consumed during the precipitation of magnesium carbonate, resulting in a decrease in pH. To accelerate the sedimentation of magnesium ions, it is necessary to adjust the pH to be maintained between 8.5 - 10.5 by adding acid or alkali.

[0044] During the process of the first-stage reaction, the reaction time is 1 - 4 h. Considering the treatment efficiency, the end of the first-stage reaction is characterized by the pH of filtrate B no longer decreasing to determine whether the reaction is complete.

[0045] The second-stage reaction is the conversion process of magnesium carbonate to basic magnesium carbonate. The formation temperature of basic magnesium carbonate is above 60 °C. However, the carbonization precipitant will decompose above 60 °C. Directly heating to prepare basic magnesium carbonate will lead to a decrease in the precipitation efficiency of magnesium ions. Therefore, a two-stage reaction is adopted. First, magnesium ions are precipitated as magnesium carbonate, and then through a temperature-raising reaction, magnesium carbonate is converted into basic magnesium carbonate. To accelerate the formation of basic magnesium carbonate, the reaction temperature in the second stage is preferably 60-95 °C.

[0046] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0047] Through the three-step process of manganese precipitation - catalytic oxidation for manganese removal - magnesium precipitation, the present invention fully combines the solubility differences and redox properties of the two, realizing the efficient separation and resource utilization of manganese and magnesium. In the manganese removal step using manganese dioxide as a catalyst in the present invention, residual divalent manganese can be efficiently oxidized into insoluble manganese dioxide, effectively removing manganese ions in the solution and creating conditions for the high-purity recovery of subsequent magnesium ions. Manganese dioxide is generated during the oxidation process, forming a self-enhanced catalytic cycle, greatly improving the oxidation efficiency, while reducing the dosage of the catalyst, reflecting the dual advantages of high efficiency and economy. The recovered manganese and magnesium exist in the forms of high-purity manganese carbonate, manganese dioxide, and basic magnesium carbonate, all of which are high-value-added products and have wide application values in fields such as lithium-ion batteries, catalysts, and flame retardants.

[0048] In addition, the process flow of the present invention is simple and easy to operate, reducing the discharge of waste liquid and solid residues, and lowering environmental pollution and treatment costs. The present invention not only realizes the efficient separation and recovery of resources, but also takes into account economy and environmental protection, and is applicable to various complex systems such as smelting waste liquid, ore acid leaching wastewater, and industrial manganese- and magnesium-containing waste liquid, having significant industrial application prospects and promotion values. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a process flow block diagram of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0050] To facilitate the understanding of the present invention, the following will describe the present invention more comprehensively and meticulously in combination with the specification drawings and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.

[0051] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0052] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchase or can be prepared by existing methods.

[0053] The composition of the manganese- and magnesium-containing solution involved in the following examples is shown in Table 1.

[0054] Table 1 Elemental analysis and results of the manganese- and magnesium-containing solution

[0055] Example 1

[0056] A method for oxidizing and separating manganese and magnesium using manganese dioxide as a catalyst and preparing basic magnesium carbonate, the process flow chart is as Figure 1 shown, including the following steps:

[0057] (1) Take 300 mL of the manganese- and magnesium-containing solution and adjust the pH to 6.5; weigh 2.72 g of ammonium bicarbonate, dissolve it in water, prepare 50 mL of ammonium bicarbonate solution, transfer it into the manganese- and magnesium-containing solution, turn on the magnetic stirrer to ensure that the reaction system is fully mixed. Control the temperature at 20 °C and react for 2 h. After the reaction, filter the solution to obtain manganese carbonate and filtrate A.

[0058] (2) Adjust the pH value of filtrate A to 7.0, weigh 0.267 g of magnesium peroxide and 0.015 g of manganese dioxide, quickly add them to filtrate A, and turn on the magnetic stirrer to ensure that the reaction system is fully mixed, then place it in a constant temperature water bath device, control the temperature to 20 °C, and maintain the reaction for 0.5 h. After the reaction, filter the reaction mixture to obtain black solid manganese dioxide and filtrate B.

[0059] (3) Adjust the pH value of filtrate B to 9.0, weigh 6.61 g of ammonium bicarbonate, and add it to the continuously stirred filtrate B. Place the reaction system in a 40 °C constant temperature water bath and continue to react for 2 h. During this period, monitor the pH value of the reaction system solution and timely supplement ammonia water according to the measurement results to maintain the system pH value stable at 9.0 until the pH no longer changes, then raise the reaction temperature to 80 °C and continue to react for 4 h. After the reaction, perform solid-liquid separation by suction filtration to obtain white basic magnesium carbonate solid and filtrate C. Example 2

[0060] (1) Take 500 mL of the manganese-containing solution and adjust the pH to 7.1; weigh 3.63 g of ammonium bicarbonate, dissolve it in water, prepare 50 mL of ammonium bicarbonate solution, transfer it into the manganese- and magnesium-containing solution, turn on the magnetic stirrer to ensure that the reaction system is fully mixed. Control the temperature at 40 °C and react for 2 h. After the reaction, filter the solution to obtain manganese carbonate and filtrate A.

[0061] (2) Adjust the pH value of filtrate A to 7.2. Weigh 0.708 g of urea peroxide and 0.045 g of manganese dioxide, quickly add them to filtrate A, and start magnetic stirring to ensure that the reaction system is fully mixed. Then place it in a constant temperature water bath device, control the temperature to 35 °C, and maintain the reaction for 1 h. After the reaction is completed, filter the reaction mixture to obtain black solid manganese dioxide and filtrate B.

[0062] (3) Adjust the pH value of filtrate B to 9.0. Weigh 11.02 g of ammonium bicarbonate and add it to the continuously stirred filtrate B. Place the reaction system at 50 °C and react for 2 h. During this period, monitor the pH value of the reaction system solution and add ammonia water in a timely manner according to the measurement results to maintain the pH value of the system stable at 9.0 until the pH no longer changes. Then raise the reaction temperature to 75 °C and continue the reaction for 4 h. After the reaction is completed, perform solid-liquid separation by suction filtration to obtain white basic magnesium carbonate solid and filtrate C. Example 3

[0063] (1) Take 1 L of manganese-magnesium solution and adjust the pH to 6.3. Weigh 7.27 g of ammonium bicarbonate, dissolve it in water to prepare a 70 mL ammonium bicarbonate solution, transfer it into the manganese-magnesium solution, and start magnetic stirring to ensure that the reaction system is fully mixed. Control the temperature at 50 °C and react for 2 h. After the reaction is completed, filter the solution to obtain manganese carbonate and filtrate A.

[0064] (2) Adjust the pH value of filtrate A to 7.4. Weigh 2.22 g of sodium percarbonate and 0.09 g of manganese dioxide, quickly add them to filtrate A, and start magnetic stirring to ensure that the reaction system is fully mixed. Then place it in a constant temperature water bath device, control the temperature to 20 °C, and maintain the reaction for 0.5 h. After the reaction is completed, filter the reaction mixture to obtain black solid manganese dioxide and filtrate B.

[0065] (3) Adjust the pH value of filtrate B to 9.0. Weigh 22.05 g of ammonium bicarbonate and add it to the continuously stirred filtrate B. Place the reaction system in a 45 °C constant temperature water bath and react for 2 hours. During this period, monitor the pH value of the reaction system solution and add ammonia water in a timely manner according to the measurement results to maintain the pH value of the system stable at 9.0 until the pH no longer changes. Then raise the reaction temperature to 90 °C and continue the reaction for 4 h. After the reaction is completed, perform solid-liquid separation by suction filtration to obtain white basic magnesium carbonate solid and filtrate C. Example 4

[0066] (1) Take 1 L of the manganese- and magnesium-containing solution and adjust the pH to 7.3; weigh 12.43 g of sodium carbonate, dissolve it in water to prepare 70 mL of sodium carbonate solution, transfer it into the manganese-containing solution, turn on the magnetic stirrer to ensure thorough mixing of the reaction system. Control the temperature at 50 °C and react for 2 h. After the reaction, filter the solution to obtain manganese carbonate and filtrate A.

[0067] (2) Adjust the pH value of filtrate A to 7.0, weigh 0.89 g of magnesium peroxide and 0.05 g of manganese dioxide, quickly add them to filtrate A, and turn on the magnetic stirrer to ensure thorough mixing of the reaction system. Then place it in a constant temperature water bath device, control the temperature to 20 °C, and maintain the reaction for 0.5 h. After the reaction, filter the reaction mixture to obtain black solid manganese dioxide and filtrate B.

[0068] (3) Adjust the pH value of filtrate B to 9.0, weigh 22.2 g of sodium carbonate, and add it to filtrate B under continuous stirring. Place the reaction system in a 40 °C constant temperature water bath and continue the reaction for 2 h. During this period, monitor the pH value of the reaction system solution and add ammonia water in a timely manner according to the measurement results to maintain the system pH value stable at 9.0 until the pH no longer changes. Then raise the reaction temperature to 80 °C and continue the reaction for 4 h. After the reaction, perform solid-liquid separation by suction filtration to obtain white basic magnesium carbonate solid and filtrate C. Example 5

[0069] (1) Take 1 L of the manganese- and magnesium-containing solution and adjust the pH to 6.7; weigh 15.11 g of ammonium carbonate, dissolve it in water to prepare 70 mL of ammonium carbonate solution, transfer it into the manganese- and magnesium-containing solution, turn on the magnetic stirrer to ensure thorough mixing of the reaction system. Control the temperature at 50 °C and react for 2 h. After the reaction, filter the solution to obtain manganese carbonate and filtrate A.

[0070] (2) Adjust the pH value of filtrate A to 3.0, weigh 2.25 g of potassium percarbonate and 0.09 g of manganese dioxide, quickly add them to filtrate A, and turn on the magnetic stirrer to ensure thorough mixing of the reaction system. Then place it in a constant temperature water bath device, control the temperature to 20 °C, and maintain the reaction for 0.5 h. After the reaction, filter the reaction mixture to obtain black solid manganese dioxide and filtrate B.

[0071] (3) Adjust the pH value of filtrate B to 9.0. Weigh 19.25 g of ammonium carbonate and add it to the continuously stirred filtrate B. Place the reaction system in a constant temperature water bath at 45 °C and react for 2 hours. During this period, monitor the pH value of the reaction system solution and timely add ammonia water according to the measurement results to maintain the pH value of the system stable at 9.0 until the pH no longer changes. Then raise the reaction temperature to 90 °C and continue to react for 4 h. After the reaction is completed, perform solid-liquid separation by suction filtration to obtain white basic magnesium carbonate solid and filtrate C.

[0072] Comparative Example 1

[0073] (1) Take 300 mL of manganese-containing solution and adjust the pH to 6.3; weigh 3.63 g of ammonium bicarbonate, dissolve it in water to prepare 100 mL of ammonium bicarbonate solution, transfer it into the manganese-magnesium-containing solution, turn on the magnetic stirrer to ensure that the reaction system is fully mixed. Control the temperature at 50 °C and react for 2 h. After the reaction is completed, filter the solution to obtain manganese carbonate and filtrate A.

[0074] (2) Adjust the pH value of filtrate A to 7.0, weigh 0.267 g of magnesium peroxide, quickly add it to filtrate A, and turn on the magnetic stirrer to ensure that the reaction system is fully mixed. Then place it in a constant temperature water bath device to control the temperature at 20 °C and maintain the reaction for 0.5 hour. After the reaction is completed, filter the reaction mixture, and no black solid manganese dioxide is obtained. The filtrate is filtrate B.

[0075] (3) Adjust the pH value of filtrate B to 9.0, weigh 6.61 g of ammonium bicarbonate, and add it to the continuously stirred filtrate B. Place the reaction system in a constant temperature water bath at 40 °C and react for 2 h. During this period, monitor the pH value of the reaction system solution and timely add ammonia water according to the measurement results to maintain the pH value of the system stable at 9.0 until the pH no longer changes. Then raise the reaction temperature to 80 °C and continue to react for 4 h. After the reaction is completed, perform solid-liquid separation by suction filtration to obtain yellow basic magnesium carbonate solid and filtrate C.

[0076] Comparative Example 2

[0077] (1) Take 500 mL of manganese-containing solution and adjust the pH to 7.1; weigh 5.44 g of ammonium bicarbonate, dissolve it in water to prepare 50 mL of ammonium bicarbonate solution, transfer it into the manganese-magnesium-containing solution, turn on the magnetic stirrer to ensure that the reaction system is fully mixed. Control the temperature at 40 °C and react for 2 h. After the reaction is completed, filter the solution to obtain manganese carbonate and filtrate A.

[0078] (2) Adjust the pH value of filtrate A to 7.2. Weigh 0.708 g of urea peroxide and quickly add it to filtrate A, then start magnetic stirring to ensure thorough mixing of the reaction system. Then place it in a constant temperature water bath device, control the temperature to 35 °C, and maintain the reaction for 1 h. After the reaction is completed, filter the reaction mixture. No black solid manganese dioxide is obtained, and the filtrate is filtrate B.

[0079] (3) Adjust the pH value of filtrate B to 9.0. Weigh 11.02 g of ammonium bicarbonate and add it to filtrate B with continuous stirring. Place the reaction system at 50 °C and continue the reaction for 2 h. During this period, monitor the pH value of the reaction system solution and timely add ammonia water according to the measurement results to maintain the pH value of the system stable at 9.0 until the pH no longer changes. Then raise the reaction temperature to 75 °C and continue the reaction for 4 h. After the reaction is completed, perform solid-liquid separation by suction filtration to obtain white basic magnesium carbonate solid and filtrate C.

[0080] Comparative Example 3

[0081] (1) Take 1 L of manganese-containing solution and adjust the pH to 6.3. Weigh 7.27 g of ammonium bicarbonate, dissolve it in water to prepare a 70 mL ammonium bicarbonate solution, transfer it into the manganese-containing magnesium solution, and start magnetic stirring to ensure thorough mixing of the reaction system. Control the temperature at 50 °C and react for 2 h. After the reaction is completed, filter the solution to obtain manganese carbonate and filtrate A.

[0082] (2) Adjust the pH value of filtrate A to 3.0. Weigh 2.22 g of sodium percarbonate and quickly add it to filtrate A, then start magnetic stirring to ensure thorough mixing of the reaction system. Then place it in a constant temperature water bath device, control the temperature to 20 °C, and maintain the reaction for 0.5 h. After the reaction is completed, filter the reaction mixture. No black solid manganese dioxide is obtained, and the filtrate is filtrate B.

[0083] (3) Adjust the pH value of filtrate B to 9.0. Weigh 22.05 g of ammonium bicarbonate and add it to filtrate B with continuous stirring. Place the reaction system in a 45 °C constant temperature water bath and continue the reaction for 2 h. During this period, monitor the pH value of the reaction system solution and timely add ammonia water according to the measurement results to maintain the pH value of the system stable at 9.0 until the pH no longer changes. Then raise the reaction temperature to 90 °C and continue the reaction for 4 h. After the reaction is completed, perform solid-liquid separation by suction filtration to obtain yellow basic magnesium carbonate solid and filtrate C.

[0084] The data results of the examples and comparative examples are shown in Table 2.

[0085] Table 2 Data Results of Examples and Comparative Examples

[0086]

[0087] According to the data in Table 2, under the conditions of using manganese dioxide as the catalyst and peroxide as the oxidant, the residual amount of manganese ions (Mn²⁺) in filtrate B in Examples 1 to 5 was significantly lower than that in Comparative Examples 1 to 3. This indicates that manganese dioxide as a catalyst can effectively remove manganese ions and achieve efficient separation of manganese and magnesium. In contrast, under the condition of not introducing manganese dioxide as the catalyst, the peroxide used as the oxidant in the comparative experiments failed to achieve the expected effect, resulting in incomplete separation of manganese and magnesium, a high content of manganese ions in filtrate B, and thus affecting the purity and quality of the final product.

[0088] The data results of manganese and magnesium recovery rates in the examples and comparative examples are shown in Table 3.

[0089] Table 3 Data Results of Manganese and Magnesium Recovery Rates in Examples and Comparative Examples

[0090]

[0091] Table 3 further shows the differences in manganese and magnesium recovery rates between the examples and comparative experiments. The manganese recovery rates in Examples 1 to 5 were all maintained above 97%, and the magnesium recovery rates were also above 94%. In some experiments, the high recovery rate even approached 99%. However, the manganese recovery rates in Comparative Examples 1 to 3 were only between 86.5% and 87.5%, and the comparative experiments failed to effectively separate manganese and magnesium, resulting in the lack of magnesium recovery and impure products. This indicates that the method of the examples of the present invention not only performs excellently in the recovery of manganese, but also ensures the efficient recovery of magnesium, achieving high-purity basic magnesium carbonate products.

[0092] Traditional carbonization precipitation method has problems such as incomplete separation, serious magnesium loss, and low resource utilization rate during the separation of manganese and magnesium. The present invention has made significant improvements on this basis. Combining the physical and chemical properties of manganese and magnesium ions, a technical solution for efficient separation and resource recovery is proposed. Through the carbonization precipitation step, using the difference in the solubility products of manganese and magnesium, most manganese ions are preferentially precipitated in the form of manganese carbonate, while magnesium ions remain in the solution, achieving the preliminary separation of manganese and magnesium. This process not only effectively removes most manganese ions, but also reduces the consumption of oxidant in the subsequent oxidation treatment. Subsequently, in the oxidation separation stage, manganese dioxide catalyst and peroxide oxidant are introduced. Through catalytic oxidation, the residual manganese ions are oxidized to high-valent manganese oxides and precipitated and separated in an insoluble form, further improving the selectivity and efficiency of manganese and magnesium separation. Finally, the process of the present invention realizes the efficient separation of manganese and magnesium resources and converts them into high-value-added industrial products, including manganese carbonate, manganese dioxide, and basic magnesium carbonate, fully realizing the comprehensive utilization of resources and maximizing value improvement.

[0093] The process of the present invention is simple and efficient, applicable to various complex solution systems containing manganese and magnesium, and has broad industrial application potential. It can be used for the separation and resource recovery of manganese and magnesium in complex systems such as smelting waste liquid, mine acidic wastewater, chemical industry discharge waste liquid, and battery recycling waste liquid. In addition, this process has important application values in environmental governance (such as the treatment of heavy metal wastewater containing manganese and magnesium), the preparation of high-value-added materials, and other industrial processes involving manganese and magnesium. Compared with traditional methods, the present invention not only significantly improves the separation efficiency of manganese and magnesium, reduces production costs and environmental burdens, decreases the discharge of waste liquid and solid residues, but also realizes the green recovery and recycling of resources. This process fully meets the dual requirements of modern industry for environmental protection and economic benefits, and has significant economic value and popularization potential.

Claims

1. A method for oxidizing and separating manganese and magnesium by using manganese dioxide as a catalyst and preparing basic magnesium carbonate, characterized in that, It includes the following steps: S1. Add alkali to the manganese- and magnesium-containing solution, adjust the pH to 6.5 - 7.5, and add soluble carbonate as a carbonization precipitant to conduct the magnesium ion carbonization precipitation reaction. The carbonization precipitant is one or more of potassium carbonate, sodium carbonate, potassium bicarbonate, sodium bicarbonate, ammonium bicarbonate, and ammonium carbonate. The concentration of the carbonization precipitant is 0.25 - 2 mol / L, the molar ratio of the carbonization precipitant to the manganese ions in the solution is 0.8 - 1.5:1, the reaction temperature is 20 - 50 °C, the reaction time is 0.5 - 2 h, and filter to obtain manganese carbonate and filtrate A; S2. Add manganese dioxide as a catalyst to the filtrate A obtained in step S1, and add an oxidant to conduct a catalytic oxidation reaction. The oxidant is at least one of magnesium peroxide, sodium peroxide, potassium peroxide, urea peroxide, sodium percarbonate, potassium percarbonate, and potassium hydrogen persulfate. The reaction temperature is 10 - 40 °C, the reaction time is 0.5 - 6 h, and filter to obtain manganese dioxide and filtrate B; S3. Add soluble carbonate as a carbonization precipitant to the filtrate B obtained in step S2. The carbonization precipitant is one or more of potassium carbonate, sodium carbonate, potassium bicarbonate, sodium bicarbonate, ammonium bicarbonate, and ammonium carbonate. The molar ratio of the carbonization precipitant to magnesium sulfate in the filtrate B is 2 - 2.5:1, and add alkali to adjust the pH of the solution to 8.5 - 10.

5. React in two stages. The first stage is the magnesium ion carbonization precipitation reaction, with a temperature of 20 - 55 °C and a time of 1 - 4 h. The second stage is the conversion of magnesium carbonate to basic magnesium carbonate, with a temperature of 60 - 95 °C and a time of 2 - 8 h. Filter to obtain the filter residue and filtrate C; S4. Wash and dry the filter residue obtained in step S3 to obtain basic magnesium carbonate.

2. The method for oxidizing and separating manganese and magnesium by using manganese dioxide as a catalyst and preparing basic magnesium carbonate according to claim 1, characterized in that, In step S1, the manganese- and magnesium-containing solution is a sulfate-type waste liquid generated during the smelting process, a manganese- and magnesium-containing waste acid liquid remaining in the metal smelting process, or a manganese- and magnesium-containing mixed waste liquid after ore acid leaching extraction.

3. The method for oxidizing and separating manganese and magnesium and preparing basic magnesium carbonate by using manganese dioxide as a catalyst according to claim 1, wherein, In steps S1 and S3, the alkali is one or more of sodium hydroxide, potassium hydroxide, and ammonia water, and the concentration of the alkali is 0.25 - 2 mol / L.

4. The method for oxidizing and separating manganese and magnesium by using manganese dioxide as a catalyst and preparing basic magnesium carbonate according to claim 1, characterized in that, In step S2, the dosage of the catalyst manganese dioxide is 5 - 200 mg / L of filtrate A.

5. The method for oxidizing and separating manganese and magnesium and preparing basic magnesium carbonate by using manganese dioxide as a catalyst according to claim 1, characterized in that, In step S2, the molar ratio of the oxidant to the manganese ions in the filtrate A is 1 - 1.5:

1.

6. The method for oxidizing and separating manganese and magnesium by using manganese dioxide as a catalyst and preparing basic magnesium carbonate according to claim 1, characterized in that, In steps S1 and S3, the carbonization precipitant is added in a way of directly putting in the solid or preparing it into a solution and then putting it in.

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