Method for selectively separating and recovering manganese ions from manganese-containing wastewater

Abstract

The present application relates to a kind of manganese ion selective separation and recovery method in manganese-containing wastewater based on magnetic substance crystal nucleus interface regulation;Belong to wastewater treatment technical field.The present application adjusts pH to 5-6 in manganese-containing wastewater, adds magnetic substance particle, water-soluble iron salt and / or water-soluble ferrous salt;Stirring, then carry out solid-liquid separation in the environment of additional magnetic field, obtain precipitate and post-manganese removal liquid, the magnetic substance contains oxide;The particle size of the magnetic substance particle is less than or equal to 38 microns.The present application realizes the resource treatment of manganese-containing wastewater, and manganese removal rate is high, and water purification effect is good, and production cost is low, and operation is simple, and environment-friendly, suitable for industrial application.

Description

Technical Field

[0001] This invention relates to a method for selective separation and recovery of manganese ions in manganese-containing wastewater based on the control of the crystal nucleus interface of magnetic materials; it belongs to the field of wastewater treatment technology. Background Technology

[0002] Manganese and its alloys are widely used in steel, alloys, magnetic materials, and chemical industries, serving as crucial metallic raw materials for national economic development and national defense. Electrolytic manganese extraction is a key method for obtaining manganese from manganese minerals. However, this process generates large quantities of manganese slag. These massive accumulations of electrolytic manganese slag, when exposed to rain, produce significant amounts of leachate, forming wastewater containing heavy metals such as manganese and magnesium. Untreated wastewater discharge poses a significant threat to soil, water bodies, and human health. Adsorption and ion exchange technologies can adsorb and concentrate manganese from wastewater onto adsorbents or resins, followed by desorption to regenerate the adsorbents and resins. This method is suitable for low-concentration manganese-containing wastewater, but it involves long reaction times and high treatment costs. Electrolysis treats manganese from wastewater using an external electric field. This method can effectively achieve resource recovery from manganese-containing wastewater, but prolonged operation can damage electrodes, affecting treatment efficiency, and its relatively high energy consumption significantly limits its application. The most common method at present is precipitation, which mainly includes: sulfide precipitation, carbonate precipitation, hydroxide precipitation, and oxidation precipitation. However, precipitation has relatively poor selectivity and cannot selectively recover and enrich manganese. It is too slow to treat high-concentration wastewater and has strict requirements on pH.

[0003] In summary, current manganese-containing wastewater treatment technologies have drawbacks such as poor manganese removal selectivity, high production costs, and difficulty in recycling manganese resources.

[0004] The technical problem to be solved by this invention is to overcome the shortcomings and defects mentioned in the background art above, and to provide a method for selective separation, enrichment and recovery of manganese ions in manganese-containing wastewater based on the co-precipitation of iron and manganese ions induced by magnetic mineral crystal nuclei. Based on the different precipitation pH of various metal ions, hydrolysis is used to co-precipitate manganese and iron ions in manganese-containing wastewater, forming an iron-manganese coprecipitate. This effectively separates manganese from other ions in the solution, and simultaneously solves the problem of difficult solid-liquid separation due to the presence of a large amount of colloid in the formed iron-manganese coprecipitate. Summary of the Invention

[0005] This invention provides a method for the selective separation and recovery of manganese ions in manganese-containing wastewater; it achieves rapid precipitation of manganese ions in manganese-containing wastewater based on the control of the crystal nucleus interface of magnetic materials.

[0006] In applications, magnetic materials include magnetic minerals.

[0007] This invention discloses a method for selective separation and recovery of manganese ions from manganese-containing wastewater, comprising the following steps:

[0008] The pH of the manganese-containing wastewater is adjusted to 5-6, and magnetic particles, water-soluble iron salts and / or water-soluble ferrous salts are added; the mixture is stirred, and then solid-liquid separation is carried out in an environment with an external magnetic field to obtain a precipitate and a manganese-removed liquid. The magnetic material contains oxides; the particle size of the magnetic material is less than or equal to 38 micrometers.

[0009] This invention discloses a method for the selective separation and recovery of manganese ions from manganese-containing wastewater; the magnetic material is preferably modified natural magnetite. The modified natural magnetite is prepared through the following process:

[0010] Natural magnetite is crushed, ground, and floated to obtain a concentrate with a particle size of less than 400 mesh (preferably less than 800 mesh). After roasting, washing, and drying, modified magnetite nuclei are obtained. The roasting temperature is 130-350℃, preferably, and the roasting time is 0.5-3 hours.

[0011] When roasting natural magnetite, the requirements for the atmosphere are not high; an air atmosphere or a protective atmosphere can be used.

[0012] This invention discloses a method for selectively separating and recovering manganese ions from manganese-containing wastewater; the water-soluble iron salt is selected from at least one of Fe2(SO4)3, FeCl3, and ferric nitrate. Ferric sulfate is preferred.

[0013] This invention discloses a method for selective separation and recovery of manganese ions from manganese-containing wastewater; the water-soluble ferrous salt is selected from at least one of FeSO4, ferrous chloride, and ferrous nitrate.

[0014] This invention discloses a method for selectively separating and recovering manganese ions from manganese-containing wastewater; magnetic material particles are added at a ratio of 0.1 to 1.1 g, preferably magnetic material particles, to 1 g of manganese ions in the manganese-containing wastewater.

[0015] This invention discloses a method for selective separation and recovery of manganese ions from manganese-containing wastewater; the molar ratio of water-soluble iron salt to manganese ions in the manganese-containing wastewater is: iron:manganese = 1.1 to 2.5, preferably 1.5 or higher.

[0016] This invention discloses a method for selective separation and recovery of manganese ions from manganese-containing wastewater; the molar ratio of water-soluble ferrous salt to manganese ions in the manganese-containing wastewater is: iron:manganese = 1.1 to 2.5, preferably 1.5 or higher; if ferrous salt is used, it is best to heat it at a temperature between 25 and 55°C, which is conducive to the phase transformation of ferrous salt.

[0017] The amount of magnetic material used generally depends on the actual application. If it passes through a 1250-mesh sieve, the molar ratio of ultrafine magnetic material particles to iron salt can be as low as 0.05; if it passes through an 800-mesh sieve, the molar ratio of magnetic material particles to iron salt can be as low as 0.1; and if it passes through a 400-mesh sieve, the molar ratio of magnetic material particles to iron salt should be greater than 0.2.

[0018] This invention discloses a method for selectively separating and recovering manganese ions from manganese-containing wastewater, wherein the stirring is aeration stirring.

[0019] The stirring speed is 100–500 rpm. In this invention, the high-speed stirring speed is 300–500 rpm; the low-speed stirring speed is 100–200 rpm.

[0020] This invention involves adjusting the pH of manganese-containing wastewater to 5-6, adding modified magnetite crystal nuclei, and then adding FeSO4 or Fe2(SO4)3 (preferably Fe2(SO4)3) to the wastewater. The amount of iron is 1.5 to 2 times the amount of manganese, where the amount of iron refers to the iron element from water-soluble ferric and ferrous salts. For example, if there are 1 mol of Mn, 1.5 times the amount of Fe is used, requiring 1.5 mol of Fe salt. After aeration and stirring, iron and manganese precipitates crystallize on the magnetic nuclei, forming a large amount of colloid, making solid-liquid separation difficult and resulting in a slow precipitation rate. Therefore, an external magnetic field must be applied. The magnetic field strength is generally determined based on the volume of water; generally, 1 L of water requires a magnetic field strength of 2500 Gauss to 8000 Gauss (1 Tesla = 1 W Gauss), and the larger the volume, the larger the magnetic field required.

[0021] This invention discloses a method for selectively separating and recovering manganese ions from manganese-containing wastewater. It uses an external magnetic field to assist in the rapid solid-liquid separation of a difficult-to-precipitate solid-liquid mixture, obtaining precipitate and wastewater. The precipitate can be recovered and used as a smelting raw material, while the wastewater meets the discharge standards.

[0022] Principles and advantages

[0023] Manganese-containing wastewater contains a large amount of manganese. Taking advantage of the properties of iron and manganese, iron can be used as a co-precipitant to precipitate manganese under low pH conditions, which can improve the removal efficiency of manganese. Most manganese-containing wastewater has a low pH, which reduces the difficulty of pH adjustment and has strong universality, and has a good effect on treating various complex water qualities.

[0024] Using natural magnetic minerals as magnetic nuclei is a low-cost approach that allows for directional and rapid precipitation. Furthermore, the morphology of the precipitate can be controlled by adjusting the size of the magnetic nuclei and the strength of the magnetic field. Due to the induction by the magnetic nuclei, the number of crystals during iron-manganese precipitation does not increase significantly, while the crystal size increases significantly, which is more conducive to precipitation recovery and resource utilization. Using magnetic field-induced precipitation allows for better control of the precipitation process, reducing the use of traditional flocculants. This method not only removes manganese but also removes fine particles and suspended pollutants from wastewater, improving water purification efficiency.

[0025] In short, this invention achieves resource-based treatment of manganese-containing wastewater, with high manganese removal rate, good water purification effect, low production cost, simple operation, environmental friendliness, and suitability for industrial application. Attached Figure Description

[0026] Figure 1 This is a process flow diagram used in Embodiment 3 of the present invention. Detailed Implementation

[0027] The modified magnets used in the embodiments of the present invention are prepared by the following process:

[0028] Natural magnetite is crushed, ground, and floated to obtain a concentrate with a particle size of less than 400 mesh. This concentrate is then roasted (at 300 degrees Celsius for 60 minutes in air), washed (using a circulating mixture of water and ethanol), and dried to obtain modified magnetite nuclei. Magnetite (Fe3O4) is the main component, along with some hematite, rutile, amphibole, ilmenite, mica, quartz, and chlorite, all in relatively small amounts.

[0029] Example 1:

[0030] A factory in Xiangxi, Hunan Province, was discharging manganese-containing wastewater with a pH of 2.9 and a total manganese content of 4890 mg / L. One liter of this wastewater was taken, and without adjusting the pH, 3g of modified magnetite was added directly. After stirring for 30 minutes, the mixture was filtered. The filter residue was still mainly composed of magnetite, indicating that manganese ions were not effectively treated. To address this, the pH of the wastewater was adjusted to 4.6, and 25g of ferric sulfate powder was added. The mixture was then mechanically stirred for 30 minutes (300-500 rpm). A permanent magnet was used to rapidly compress the precipitate (using an external magnetic field of 4500 Gauss). Solid-liquid separation was completed in less than 2 seconds, reducing the total manganese concentration in the clarified liquid to 469.4 mg / L, achieving a removal rate of 90.4%.

[0031] Example 2

[0032] A laboratory in Changsha, Hunan Province, had manganese-containing wastewater with a pH of 4.4 and a total manganese content of 6145.5 mg / L. 500 mL of this wastewater was taken, the pH adjusted to 5.6, and 2.5 g of magnetite was added. After stirring for 10 minutes and filtering (300-500 rpm), the total manganese content was 6136.5 mg / L. Under the same conditions, Fe was introduced... 3+ After aeration and mechanical stirring for 10 minutes, followed by settling for 10 minutes, no significant solid-liquid separation was observed in the vertical direction. Magnetic flocs were recovered using a magnet (external magnetic field strength of 4500 Gauss). After solid-liquid separation, manganese in the clarified liquid was measured, showing a removal rate of 91.2%. This demonstrates that the selective separation and enrichment recovery method for manganese ions in manganese-containing wastewater based on the co-precipitation of iron and manganese ions induced by magnetic mineral crystal nuclei can effectively and selectively separate and recover manganese from manganese-containing wastewater.

[0033] Example 3

[0034] Three types of manganese-containing wastewater (each with a treatment capacity of 1L) were collected from an electrolytic manganese plant in Huayuan County, Hunan Province. The pH was adjusted to 5-6. The different treatment conditions and results are shown in the table. As can be seen from the table, the selective separation-enrichment and recovery method of manganese ions in manganese-containing wastewater based on the co-precipitation of iron and manganese ions induced by magnetic mineral crystal nuclei can effectively and selectively separate manganese from manganese-containing wastewater. Under the assistance of a magnetic field, the enrichment and recovery of manganese can be completed quickly (the strength of the external magnetic field is shown in Table 1).

[0035] Table 1

[0036]

[0037]

[0038] Rotation speed: 300-500 rpm.

[0039] Example 4: A laboratory wastewater containing manganese had a pH of 3.5 and a total manganese content of 2,420 mg / L. 500 L of this wastewater was taken, and the pH was adjusted to 5.0. 2 g of magnetite and 16 g of ferrous sulfate powder were added. The mixture was stirred at high speed with aeration at 40°C for 15 min (300–500 rpm). Afterward, the temperature was not maintained, and the stirring was slowed down (100–200 rpm) without aeration. Adsorption was performed using a 3000 Gauss permanent magnet. The total manganese removal rate in the clarified liquid after solid-liquid separation reached 93.1%.

Claims

1. A method for selective separation and recovery of manganese ions from manganese-containing wastewater; characterized in that: The process includes the following steps: adjusting the pH of manganese-containing wastewater to 5-6; adding magnetic material particles, water-soluble iron salts, and / or water-soluble ferrous salts at a ratio of 0.1-1.1g of magnetic material particles to 1g of manganese ions in the wastewater; stirring; and then performing solid-liquid separation in an external magnetic field environment to obtain a precipitate and a manganese-removed liquid. The magnetic material contains oxides; the particle size of the magnetic material particles is less than or equal to 38 micrometers; the molar ratio of water-soluble iron salts to manganese ions in the manganese-containing wastewater is: iron:manganese = 1.1-2.5; the stirring is aeration stirring. The magnetic material is modified natural magnetite; the modified natural magnetite is prepared by the following process: Natural magnetite is crushed, ground, and floated to obtain a concentrate with a particle size of less than 400 mesh. After roasting, washing, and drying, modified magnetite nuclei are obtained. The roasting temperature is 130-350℃ and the roasting time is 0.5-3h. The strength of the external magnetic field is determined by the volume of water, that is, 1L of water corresponds to a magnetic field strength of 2500 Gauss to 8000 Gauss.

2. The method for selective separation and recovery of manganese ions in manganese-containing wastewater according to claim 1; characterized in that: The water-soluble iron salt is selected from at least one of Fe2(SO4)3, FeCl3, and ferric nitrate.

3. A method for selective separation and recovery of manganese ions in manganese-containing wastewater according to claim 1; characterized in that: The water-soluble iron salt is ferric sulfate.

4. A method for selective separation and recovery of manganese ions in manganese-containing wastewater according to claim 1; characterized in that: The water-soluble ferrous salt is selected from at least one of FeSO4, ferrous chloride, and ferrous nitrate.

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