Method for preparing heavy manganese carbonate from manganese slag washing water based on microreactor

Abstract

The invention belongs to the technical field of manganese slag treatment, and provides a method for preparing heavy manganese carbonate from manganese slag washing water based on a microreactor. The method comprises the following steps: mixing manganese slag washing water and an additive, and carrying out solid-liquid separation to obtain filter residues and filtrate; and mixing the filtrate and the alkali liquor to obtain a manganese ion solution, and respectively introducing the manganese ion solution and carbon dioxide mixed gas into the microreactor for reaction to obtain the heavy manganese carbonate. The manganese slag washing water and the carbon dioxide react in the microreactor, and the pH value of the manganese ion solution, the flow of the manganese ion solution and the carbon dioxide, the reaction temperature, the reaction pressure and the reaction time are controlled, so that the yield of manganese in the obtained heavy manganese carbonate is high, the purity is high, and the manganese content in the effluent filtrate is low; the obtained heavy manganese carbonate can be directly used as a raw material for electrolytic manganese metal, and the purposes of effective treatment of manganese residue washing water and comprehensive recycling of resources under mild conditions are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of manganese slag treatment, and in particular to a method for preparing heavy manganese carbonate by washing manganese slag with water based on a microreactor. Background Art

[0002] Electrolytic manganese slag is the acidic waste residue produced after manganese carbonate ore undergoes acid leaching, neutralization, and filter pressing in the electrolytic manganese metal process. Electrolytic manganese slag is often acidic or weakly acidic due to its high water content and complex chemical composition. Among them, Si, Ca, Fe, Al, Mg, Cr ions, soluble manganese compounds, and ionic ammonia nitrogen are the main pollutants. At present, most electrolytic manganese slag is directly stored. Long-term storage of electrolytic manganese slag not only occupies land resources, but also easily produces a large amount of leachate in the rainy season. The leachate enters the surrounding soil and groundwater, causing serious environmental pollution.

[0003] Chemical precipitation and micro-electrolysis are commonly used in the treatment process of manganese and ammonia nitrogen wastewater. This type of method has a high removal efficiency for high-concentration manganese ions, but there are still major problems in meeting the requirements of emission standards. For example, the calcium hydroxide precipitation method requires a higher pH value to achieve an effluent manganese ion concentration of about 2 mg / L, and the effluent is unstable. At the same time, due to the introduction of a large number of calcium ions, the precipitated residue is difficult to recycle. Micro-electrolysis technology has no engineering application at present due to its high operating cost, difficulty in control, and relatively immature technology. The invention patents with publication numbers CN03172194A and CN102728230A propose a membrane combination process. The main problems of this process are high membrane load during operation, harsh operating conditions, high operating difficulty, and difficulty in operation. It is difficult to ensure long-term stable operation. The effluent ammonia nitrogen is unstable, and a filtration adsorption system needs to be added, which increases the operating cost.

[0004] A microreactor is a three-dimensional structural element that can be used for chemical reactions and is made of a solid matrix using special micromachining technology. Microreactors usually contain small channel sizes (equivalent diameter less than 500μm) and channel diversity, in which fluids flow and react. The internal microstructure of the microreactor gives the microreactor equipment a very large specific surface area, which can reach hundreds or even thousands of times the specific surface area of ​​a stirred tank. Microreactors have excellent heat and mass transfer capabilities, and can achieve instantaneous uniform mixing of materials and efficient heat transfer. Therefore, many reactions that cannot be achieved in conventional reactors can be achieved in microreactors. At present, microreactors have been widely used in the research and development of chemical process, and their application in commercial production is increasing. Its main application areas include organic synthesis processes, the preparation of micro and nano materials, and the production of daily chemicals.

[0005] Therefore, it is of great significance to provide a method for preparing heavy manganese carbonate from manganese slag washing water based on a microreactor to improve the recovery rate of manganese ions and the purity of manganese carbonate. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing heavy manganese carbonate by washing manganese slag with water based on a microreactor in view of the shortcomings of the prior art.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing heavy manganese carbonate from manganese slag washing water based on a microreactor, comprising the following steps:

[0009] 1) mixing the manganese slag washing water and the additive and performing solid-liquid separation to obtain a filter residue and a filtrate;

[0010] 2) The filtrate is mixed with the alkali solution to obtain a manganese ion solution, and the manganese ion solution and the carbon dioxide mixed gas are respectively introduced into a microreactor to react to obtain heavy manganese carbonate.

[0011] Preferably, the additive in step 1) comprises calcium carbonate and calcium oxide, and the mass ratio of calcium carbonate to calcium oxide is 1.5 to 2.5:1.

[0012] Preferably, the pH value of the mixed solution obtained by mixing the manganese slag washing water and the additive in step 1) is 5.7-6.2.

[0013] Preferably, the alkali solution in step 2) is a sodium hydroxide solution, the mass concentration of the sodium hydroxide solution is 10-15%; and the pH value of the manganese ion solution is 8.7-9.3.

[0014] Preferably, in the microreactor of step 2), the flow rate of the manganese ion solution is 2-4 L / min, and the flow rate of the carbon dioxide mixed gas is 0.3-0.5 L / min.

[0015] Preferably, the carbon dioxide mixed gas in step 2) consists of carbon dioxide and nitrogen, and the volume concentration of carbon dioxide in the carbon dioxide mixed gas is 15-22%.

[0016] Preferably, the reaction temperature in step 2) is 45-55° C., and the reaction time is 1-2 h.

[0017] Preferably, the reaction pressure in step 2) is 0.5-2 MPa.

[0018] The beneficial effects of the present invention include the following:

[0019] 1) In the present invention, manganese slag washing water reacts with carbon dioxide in a microreactor, and by controlling the pH value of the manganese ion solution, the flow rates of the manganese ion solution and the carbon dioxide, the reaction temperature, pressure and time, the obtained heavy manganese carbonate has a high manganese yield and high purity, and the manganese content in the effluent filtrate is low; the obtained heavy manganese carbonate can be directly used as a raw material for electrolytic manganese metal, thereby achieving the purpose of effective treatment of manganese slag washing water and comprehensive resource recovery and utilization under mild conditions.

[0020] 2) When preparing manganese carbonate in the present invention, the pH value of the manganese ion solution is first adjusted to alkaline, and carbon dioxide is introduced into the microreactor. The carbon dioxide first undergoes an ionization reaction to generate bicarbonate and carbonate. Since the manganese ion solution is alkaline, the carbon dioxide is ionized to generate more carbonate. The carbonate combines with the manganese ions in the solution to obtain heavy manganese carbonate with a regular shape. DETAILED DESCRIPTION

[0021] The present invention provides a method for preparing heavy manganese carbonate from manganese slag washing water based on a microreactor, comprising the following steps:

[0022] 1) mixing the manganese slag washing water and the additive and performing solid-liquid separation to obtain a filter residue and a filtrate;

[0023] 2) The filtrate is mixed with the alkali solution to obtain a manganese ion solution, and the manganese ion solution and the carbon dioxide mixed gas are respectively introduced into a microreactor to react to obtain heavy manganese carbonate.

[0024] In the present invention, manganese slag washing water is wastewater generated in the process of treating electrolytic manganese production, and its main components include manganese dioxide, manganese sulfate and ammonia nitrogen, etc., and an appropriate method is used to treat the manganese slag washing water to reduce the impact on the environment.

[0025] The manganese slag washing water of the present invention preferably contains the following substances: Mn 2+ 2.5~3g / L, Mg 2+ 1.5~2g / L, Ca 2+ 0.11~0.13g / L, NH4 + -N 1.5~2g / L.

[0026] In the present invention, the additive in step 1) preferably comprises calcium carbonate and calcium oxide, and the mass ratio of calcium carbonate to calcium oxide is preferably 1.5 to 2.5:1, more preferably 1.8 to 2.2:1, and more preferably 2:1.

[0027] In the present invention, the pH value of the mixed solution obtained by mixing the manganese slag washing water and the additive in step 1) is preferably 5.7 to 6.2, more preferably 5.8 to 6.1, and more preferably 5.9 to 6.0.

[0028] The pH value of the mixed solution obtained by mixing the manganese slag washing water and the additive in the present invention is 5.7-6.2, which is conducive to removing impurities such as iron, calcium, magnesium, etc., and manganese does not form precipitation.

[0029] In the present invention, the alkali solution in step 2) is preferably a sodium hydroxide solution, and the mass concentration of the sodium hydroxide solution is preferably 10-15%, more preferably 11-14%, and more preferably 12-13%; the pH value of the manganese ion solution is preferably 8.7-9.3, more preferably 8.8-9.1, and more preferably 8.9-9.0.

[0030] In the present invention, as the pH value of the manganese ion solution increases, the concentration of the remaining soluble manganese after the manganese ion solution reacts with carbon dioxide gradually decreases, and the recovery rate of the soluble manganese gradually increases; when the pH value reaches 8.7-9.3, the recovery rate of the soluble manganese tends to be balanced; the pH value should not be too high to avoid the generation of calcium magnesium carbonate precipitation and hydroxide precipitation, and the precipitation mixed with manganese carbonate slag will reduce the purity of manganese carbonate.

[0031] In the present invention, in the microreactor described in step 2), the flow rate of the manganese ion solution is preferably 2-4 L / min, more preferably 2.5-3.5 L / min, and more preferably 3 L / min; the flow rate of the carbon dioxide mixed gas is preferably 0.3-0.5 L / min, more preferably 0.35-0.45 L / min, and more preferably 0.4 L / min.

[0032] The carbon dioxide flow rate is too small, and the manganese ion recovery rate is low. The carbon dioxide flow rate of the present invention makes the manganese ion recovery rate higher. The manganese recovery rate does not change much when the carbon dioxide flow rate is further increased. The manganese carbonate grains obtained by the carbon dioxide flow rate of the present invention are uniform and coarse, which can reduce the entrainment of impurity ions such as sodium ions and sulfate ions.

[0033] In the present invention, the carbon dioxide mixed gas in step 2) is preferably composed of carbon dioxide and nitrogen, and the volume concentration of carbon dioxide in the carbon dioxide mixed gas is preferably 15-22%, more preferably 17-20%, and more preferably 18-19%.

[0034] In the present invention, the reaction temperature in step 2) is preferably 45-55°C, more preferably 47-53°C, more preferably 49-50°C, and the reaction time is preferably 1-2h, more preferably 1.3-1.7h, more preferably 1.5h.

[0035] In the present invention, the pressure of the reaction in step 2) is preferably 0.5 to 2 MPa, more preferably 0.8 to 1.6 MPa, and even more preferably 1 to 1.5 MPa.

[0036] The invention reduces the solubility of manganese carbonate by reasonably controlling the reaction temperature and pressure, is beneficial to controlling the saturation of the reaction system, accelerates the formation of crystal nuclei, and promotes the generation of manganese carbonate precipitation.

[0037] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0038] In the embodiment, the manganese slag washing water contains the following substances: Mn 2+ 2.8g / L, Mg 2+ 1.6 g / L, Ca 2+ 0.12g / L, NH4 + -N 1.7 g / L;

[0039] The microreactor is a small-scale PTFE threaded tube microreactor, model: NYC-YN-2X (8D).

[0040] Example 1

[0041] The manganese slag washing water and the additive are mixed, and the pH value of the obtained mixed solution is 5.9. The additive is composed of calcium carbonate and calcium oxide in a mass ratio of 2:1. The mixed solution is filtered to obtain filter residue and filtrate. The filter residue mainly contains impurities such as iron, calcium, and magnesium.

[0042] The filtrate is mixed with a sodium hydroxide solution with a mass concentration of 12% to obtain a manganese ion solution with a pH value of 9.1. The manganese ion solution and the carbon dioxide mixed gas are respectively introduced into a microreactor for reaction. The flow rate of the manganese ion solution is 3 L / min, and the flow rate of the carbon dioxide mixed gas (the volume concentration of carbon dioxide in the mixed gas is 18%) is 0.4 L / min. The reaction is carried out at 50° C. and a pressure of 1.5 MPa for 1.5 hours, and crystallization forms particles. The particles are washed with deionized water, filtered, and dried to obtain black solid particles of heavy manganese carbonate. The filtrate after the reaction is a manganese removal filtrate.

[0043] The manganese concentration in the manganese removal filtrate obtained in this embodiment is 0.45 mg / L, which meets the first-level emission standard for total manganese in the "Integrated Wastewater Discharge Standard" (GB8978-1996); compared with manganese slag washing water, the total content of iron, magnesium and calcium in the manganese removal filtrate is reduced by 90%.

[0044] The purity of the heavy manganese carbonate in this embodiment is 98.5%, and the recovery rate of soluble manganese is 98.7%. The heavy manganese carbonate can be directly used as a raw material for electrolytic manganese metal.

[0045] Example 2

[0046] The manganese slag washing water and the additive are mixed, and the pH value of the obtained mixed solution is 6.1. The additive is composed of calcium carbonate and calcium oxide with a mass ratio of 2.2:1. The mixed solution is filtered to obtain filter residue and filtrate. The filter residue mainly contains impurities such as iron, calcium, and magnesium.

[0047] The filtrate is mixed with a sodium hydroxide solution with a mass concentration of 14% to obtain a manganese ion solution with a pH value of 9.3. The manganese ion solution and the carbon dioxide mixed gas are respectively introduced into a microreactor for reaction. The flow rate of the manganese ion solution is 3.5 L / min, and the flow rate of the carbon dioxide mixed gas (the volume concentration of carbon dioxide in the mixed gas is 20%) is 0.45 L / min. The reaction is carried out at 53° C. and a pressure of 0.8 MPa for 1 hour, and crystallization forms particles. The particles are washed with deionized water, filtered, and dried to obtain black solid particles of heavy manganese carbonate. The filtrate after the reaction is a manganese removal filtrate.

[0048] The manganese concentration in the manganese removal filtrate obtained in this embodiment is 0.48 mg / L, which meets the first-level emission standard for total manganese in the "Integrated Sewage Discharge Standard" (GB8978-1996); compared with manganese slag washing water, the total content of iron, magnesium and calcium in the manganese removal filtrate is reduced by 87%.

[0049] The purity of the heavy manganese carbonate in this embodiment is 97.5%, and the recovery rate of soluble manganese is 98%. The heavy manganese carbonate can be directly used as a raw material for electrolytic manganese metal.

[0050] Example 3

[0051] The manganese slag washing water and the additive are mixed, and the pH value of the obtained mixed solution is 5.7. The additive is composed of calcium carbonate and calcium oxide with a mass ratio of 1.8:1. The mixed solution is filtered to obtain filter residue and filtrate. The filter residue mainly contains impurities such as iron, calcium, and magnesium.

[0052] The filtrate is mixed with a sodium hydroxide solution with a mass concentration of 10% to obtain a manganese ion solution with a pH value of 8.8. The manganese ion solution and the carbon dioxide mixed gas are respectively introduced into a microreactor for reaction. The flow rate of the manganese ion solution is 2.5 L / min, and the flow rate of the carbon dioxide mixed gas (the volume concentration of carbon dioxide in the mixed gas is 16%) is 0.35 L / min. The reaction is carried out at 45° C. and a pressure of 1.2 MPa for 2 hours to crystallize into particles. The particles are washed with deionized water, filtered, and dried to obtain black solid particles of heavy manganese carbonate. The filtrate after the reaction is a manganese removal filtrate.

[0053] The manganese concentration in the manganese removal filtrate obtained in this embodiment is 0.47 mg / L, which meets the first-level emission standard for total manganese in the "Integrated Sewage Discharge Standard" (GB8978-1996); compared with manganese slag washing water, the total content of iron, magnesium and calcium in the manganese removal filtrate is reduced by 85%.

[0054] The purity of the heavy manganese carbonate in this embodiment is 97.8%, and the recovery rate of soluble manganese is 98%. The heavy manganese carbonate can be directly used as a raw material for electrolytic manganese metal.

[0055] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing heavy manganese carbonate from manganese slag washing water based on a microreactor, characterized in that: The following steps are included: 1) mixing the manganese slag washing water and the additive and performing solid-liquid separation to obtain a filter residue and a filtrate; 2) The filtrate is mixed with the alkali solution to obtain a manganese ion solution, and the manganese ion solution and the carbon dioxide mixed gas are respectively introduced into a microreactor to react to obtain heavy manganese carbonate.

2. The method for preparing heavy manganese carbonate from manganese slag washing water based on a microreactor according to claim 1, characterized in that: Step 1) The additive comprises calcium carbonate and calcium oxide, and the mass ratio of calcium carbonate to calcium oxide is 1.5-2.5:

1.

3. The method for preparing heavy manganese carbonate from manganese slag washing water based on a microreactor according to claim 1 or 2, characterized in that: In step 1), the pH value of the mixed solution obtained by mixing the manganese slag washing water and the additive is 5.7-6.

2.

4. The method for preparing heavy manganese carbonate from manganese slag washing water based on a microreactor according to claim 3, characterized in that: Step 2) The alkali solution is a sodium hydroxide solution, the mass concentration of the sodium hydroxide solution is 10-15%; the pH value of the manganese ion solution is 8.7-9.

3.

5. The method for preparing heavy manganese carbonate from manganese slag washing water based on a microreactor according to claim 4, characterized in that: Step 2) In the microreactor, the flow rate of the manganese ion solution is 2-4 L / min, and the flow rate of the carbon dioxide mixed gas is 0.3-0.5 L / min.

6. The method for preparing heavy manganese carbonate from manganese slag washing water based on a microreactor according to claim 4 or 5, characterized in that: Step 2) The carbon dioxide mixed gas is composed of carbon dioxide and nitrogen, and the volume concentration of carbon dioxide in the carbon dioxide mixed gas is 15-22%.

7. The method for preparing heavy manganese carbonate from manganese slag washing water based on a microreactor according to claim 6, characterized in that: Step 2) The reaction temperature is 45-55°C and the reaction time is 1-2h.

8. The method for preparing heavy manganese carbonate from manganese slag washing water based on a microreactor according to claim 7, characterized in that: Step 2) The reaction pressure is 0.5-2 MPa.