A method for recycling modified manganese slag to treat heavy metal ions

Abstract

The invention discloses a method for treating heavy metal ions by recycling modified manganese slag, belonging to the technical field of heavy metal ion treatment. The method comprises the following steps: (1) adjusting the pH value of heavy metal wastewater to be treated by using an alkaline solution to be 9-10; (2) mixing the heavy metal wastewater with the modified manganese slag, stirring for 20-40 minutes and then standing; (3) filtering after standing for 12-24 hours, and performing subsequent treatment on the separated wastewater. The invention aims to develop a method for removing heavy metal ions from wastewater by using manganese slag, and solve the problem that the current waste manganese slag has low activity and poor effect of removing heavy metal ions.

Description

Technical Field

[0001] The invention relates to the technical field of heavy metal ion treatment, and in particular to a method for treating heavy metal ions by recycling modified manganese slag. Background Art

[0002] The harm of heavy metals to the environment and human body is mainly due to the discharge of heavy metal-containing wastewater into water bodies, which causes a sharp increase in the heavy metal content in the water bodies, and then infiltrates the soil and accumulates through the food chain, endangering human health. Heavy metal elements are difficult to degrade, highly toxic, and difficult to recycle after treatment, which seriously endangers human safety. For example, Cr 6+ 、Cd 2+ Heavy metal elements such as Cd have carcinogenic, teratogenic, and mutagenic hazards. For example, the "Itai-itai disease" in the Jinzu River basin in Fuji Prefecture, Japan is a typical example. 2+ Poisoning incidents. This is mainly caused by the unreasonable discharge of heavy metal wastewater from electrolysis, electroplating, metal mining, smelting, chemical industry, electronics, leather making and other industries. In order to take into account both environmental and economic development benefits, research on the treatment of heavy metal pollution in water has become an inevitable trend.

[0003] Manganese ore is a kind of mineral widely distributed in nature, but for a long time, the development and utilization of manganese ore has been mainly in the field of its resource attributes, such as batteries, metallurgy, chemical industry, glass and other fields. Manganese slag is the waste left after natural manganese ore is electrolyzed or reduced. At present, manganese slag is mainly used to make manganese fertilizer, concrete, microcrystalline glass, etc. It mainly contains iron, aluminum, silicon, calcium, sulfur and other components. Manganese slag has a dense surface, few pores and large particles. It is mainly composed of crystalline slag and part of the glass phase. The chemical properties are relatively stable and the activity is slow. Therefore, it is urgent to realize the reuse of manganese slag, turn it into treasure, and recycle it to treat heavy metal ions in wastewater. Summary of the invention

[0004] In view of this, the purpose of the present invention is to develop a method for removing heavy metal ions in wastewater using manganese slag, while solving the problem that the current waste manganese slag has low activity and poor effect in removing heavy metal ions.

[0005] A method for recycling modified manganese slag to treat heavy metal ions, the steps are as follows:

[0006] (1) adjusting the pH of the heavy metal wastewater to be treated to 9-10 with an alkaline solution;

[0007] (2) mixing the heavy metal wastewater with the modified manganese slag, stirring for 20-40 minutes and then letting it stand;

[0008] (3) After standing for 12-24 hours, filter and carry out subsequent treatment on the separated wastewater.

[0009] Industrial heavy metal wastewater is highly acidic. In order to facilitate the modified manganese slag to capture and flocculate heavy metal ions, the pH value needs to be adjusted to be alkaline. The optimal range is pH = 9-10. Lime water can be used to adjust the pH.

[0010] At the same time, in order to better remove other pollutants in wastewater, it can also be used in combination with other treatment methods such as grilles, screens, aeration tanks, biochemical tanks, sedimentation tanks, etc.

[0011] Furthermore, the dosage of the modified manganese slag is 1-1000g / L. The modified manganese slag mainly removes copper ions, lead ions, mercury ions and cadmium ions in the wastewater. The higher the heavy metal content, the more modified manganese slag is used.

[0012] Furthermore, the preparation method of the modified manganese slag comprises the following steps:

[0013] a. Crush the manganese slag and place it in hot water at 70-80°C for 24 hours. Take it out and soak it in triethanolamine solution at room temperature for 24-36 hours. Take it out and rinse it with water, dry it, and grind it into manganese ore powder;

[0014] b. Add the treated manganese ore powder to Tris-hydrochloric acid buffer, then add dopamine and sodium lauryl sulfonate, adjust the pH to 9-10, stir for 3-4 hours and let stand for 12 hours, filter after standing, add a mixed solution made of sodium citrate solution, sodium nitrate solution and potassium fluoride solution at room temperature, react for 4 hours, take out, then mix with phthalate and polylactic acid-glycolic acid copolymer, and stir for 24 hours to obtain the modified manganese slag.

[0015] Manganese slag is mainly composed of densely structured crystalline minerals, glass, soluble salts and impurities. After crushing, the manganese slag particles and crystalline minerals are refined, and the internal structure of the manganese slag changes. After soaking in hot water, most of the soluble salts and impurities can be removed to avoid the reaction of the raw materials of subsequent operations with soluble salts. Triethanolamine solution is weakly alkaline, which has a local corrosive and dissolving effect on manganese slag powder, prompting the crystal lattice of manganese slag to further change, forming particles with pores, and initially activating the activity of manganese slag. Then, through grinding, the crystal form of manganese slag changes and the grains are refined under the action of mechanical force, and the specific surface area increases. After being treated with hot water and triethanolamine solution, the crystal form of manganese slag changes, and then it reacts with dopamine and sodium laurel sulfonate under alkaline conditions to generate polydopamine with hydrophilicity, making the surface of manganese slag highly modifiable. The manganese slag is then modified with sodium citrate, sodium nitrate and potassium fluoride to stably chelate the polydopamine on the surface of the manganese slag with metal oxides and modified substances, further improving the activity of the manganese slag. During the wastewater treatment process, the manganese slag is hydrated under alkaline conditions to form a gel to adsorb heavy metal ions. Phthalate esters and polylactic acid-glycolic acid copolymers are mixed on the surface of the manganese slag powder to form a film, which wraps the manganese slag powder with adsorption and high activity. After stirring and contacting with alkaline wastewater, the film degrades, and the manganese slag powder adsorbs heavy metal ions, achieving the purpose of treating wastewater, and is also convenient for normal storage.

[0016] Furthermore, the iron oxide content in the manganese slag is ≤3%. The manganese slag contains unstable iron oxide, which is very likely to react with the raw materials during the activation process. The iron content needs to be controlled when modifying the manganese slag.

[0017] Furthermore, the concentration of the triethanolamine solution is 5-10wt%.

[0018] Furthermore, the mass ratio of the manganese slag to dopamine and sodium laurel sulfonate is 10:(0.5-1):0.01.

[0019] Furthermore, the mass ratio of the manganese slag to the sodium citrate solution, the sodium nitrate solution and the potassium fluoride solution is 1:0.6:1:1.

[0020] Furthermore, the concentrations of the sodium citrate solution, sodium nitrate solution, and potassium fluoride solution are 0.2 mol / L, 1 mol / L, and 0.1 mol / L, respectively.

[0021] Furthermore, the mass ratio of the phthalate to the polylactic acid-glycolic acid copolymer is 1:0.4.

[0022] Beneficial effects:

[0023] 1. The present invention modifies and utilizes waste manganese slag, and the activity of the manganese slag is improved after modification. The industrial heavy metal wastewater containing copper ions, lead ions, mercury ions, and cadmium ions can be treated, and the removal rate reaches more than 95%, and the removal rate of mercury ions and cadmium ions reaches more than 99%.

[0024] 2. The present invention expands the application scenarios of manganese slag, improves resource utilization, realizes green circular development, and reduces and avoids the generation of pollutants.

[0025] 3. The processing method of the present invention is simple and convenient, and is suitable for large-scale promotion and use in factories. DETAILED DESCRIPTION

[0026] The present invention will be described in detail below with reference to embodiments:

[0027] Example 1: Preparation of modified manganese slag

[0028] In this embodiment, the raw materials for preparing manganese slag are weighed:

[0029] 200g manganese slag, 10g dopamine, 0.2g sodium laurel sulfonate, 0.2mol / L 120g sodium citrate solution, 1mol / L 200g sodium nitrate solution, 0.1mol / L 200g potassium fluoride solution, 200g phthalate, 80g polylactic acid-glycolic acid copolymer, the manganese slag used in this embodiment is derived from a mining company in Xiushan, Chongqing, and the iron oxide content in the manganese slag is about 2.1%.

[0030] The preparation steps are as follows:

[0031] a. The manganese slag was crushed into fine slag of about 2-3 mm and placed in hot water at 80°C for 24 hours, removed, and soaked and stirred in a 5wt% triethanolamine solution at room temperature for 24 hours until the triethanolamine solution covered the manganese slag, then removed, rinsed with water, dried, and ground into manganese ore powder with a particle size of about 0.05 mm;

[0032] b. Add the treated manganese ore powder into 0.05mmol / L Tris-hydrochloric acid buffer until it is covered, then add dopamine and sodium lauryl sulfonate, adjust the pH to 9, stir for 3h and let stand for 12h, filter after standing, add the manganese ore powder into a mixed solution of sodium citrate solution, sodium nitrate solution and potassium fluoride solution at room temperature, react for 4h, take out, then mix with phthalate and polylactic acid-glycolic acid copolymer, stir at room temperature for 24h to obtain the modified manganese slag.

[0033] Example 2: Preparation of modified manganese slag

[0034] In this embodiment, the raw materials for preparing manganese slag are weighed:

[0035] 100g manganese slag, 10g dopamine, 0.1g sodium laurel sulfonate, 0.2mol / L 60g sodium citrate solution, 1mol / L 100g sodium nitrate solution, 0.1mol / L 100g potassium fluoride solution, 100g phthalate, 40g polylactic acid-glycolic acid copolymer. The manganese slag used in this embodiment is derived from a mining company in Xiushan, Chongqing. The content of iron oxide in the manganese slag is about 2.1%.

[0036] The preparation steps are as follows:

[0037] a. The manganese slag was crushed into fine slag of about 2-5 mm and placed in hot water at 70°C for 24 hours, removed, and soaked and stirred in 8wt% triethanolamine solution at room temperature for 36 hours until the triethanolamine solution covered the manganese slag, then removed, rinsed with water, dried, and ground into manganese ore powder with a particle size of about 0.05 mm;

[0038] b. Add the treated manganese ore powder into 0.05mmol / L Tris-hydrochloric acid buffer until it is covered, then add dopamine and sodium lauryl sulfonate, adjust the pH to 10, stir for 4h and let stand for 12h, filter after standing, add the manganese ore powder into a mixed solution of sodium citrate solution, sodium nitrate solution and potassium fluoride solution at room temperature, react for 4h, take out, then mix with phthalate and polylactic acid-glycolic acid copolymer, stir at room temperature for 24h to obtain the modified manganese slag.

[0039] Example 3: Preparation of modified manganese slag

[0040] In this embodiment, the raw materials for preparing manganese slag are weighed:

[0041] 50g manganese slag, 3.5g dopamine, 0.05g sodium laurel sulfonate, 0.2mol / L 30g sodium citrate solution, 1mol / L 50g sodium nitrate solution, 0.1mol / L 50g potassium fluoride solution, 50g phthalate, 20g polylactic acid-glycolic acid copolymer, the manganese slag used in this embodiment is derived from a mining company in Xiushan, Chongqing, and the content of iron oxide in the manganese slag is about 2.1%.

[0042] The preparation steps are as follows:

[0043] a. The manganese slag was crushed into fine slag of about 2-5 mm and placed in hot water at 75°C for 24 hours, removed, and soaked and stirred in a 10wt% triethanolamine solution at room temperature for 25 hours until the triethanolamine solution covered the manganese slag, then removed, rinsed with water, dried, and ground into manganese ore powder with a particle size of about 0.05 mm;

[0044] b. Add the treated manganese ore powder into 0.05mmol / L Tris-hydrochloric acid buffer solution until it is covered, then add dopamine and sodium lauryl sulfonate, adjust the pH to 9.5, stir for 3.5h and let stand for 12h, filter after standing, add the manganese ore powder into a mixed solution of sodium citrate solution, sodium nitrate solution and potassium fluoride solution at room temperature, react for 4h, take out, then mix with phthalate and polylactic acid-glycolic acid copolymer, stir at room temperature for 24h to obtain the modified manganese slag.

[0045] Embodiment 4:

[0046] The method for treating heavy metal wastewater using the modified manganese slag prepared in Examples 1-3 is as follows:

[0047] (1) adjusting the pH value of the heavy metal wastewater to be treated to 9-10 with an alkaline solution, preferably a lime solution;

[0048] (2) mixing the heavy metal wastewater with the modified manganese slag, stirring for 20-40 minutes and then letting it stand;

[0049] (3) After standing for 12-24 hours, filter and carry out subsequent treatment on the separated wastewater.

[0050] Comparative Example 1:

[0051] This comparative example is compared with Example 1. The same manganese slag is directly crushed into fine powder of about 0.05 mm and then used for wastewater treatment.

[0052] Comparative Example 2:

[0053] This comparative example is in contrast to Example 1, and the only difference from Example 1 is that in step a, no hot water is used for soaking, and the subsequent treatment is performed after direct soaking and stirring with triethanolamine solution at room temperature.

[0054] Comparative Example 3:

[0055] This comparative example is in contrast to Example 1, and the only difference from Example 1 is that the manganese slag is directly subjected to step b treatment.

[0056] Comparative Example 4:

[0057] This comparative example is in contrast to Example 1. The only difference from Example 1 is that dopamine and sodium lauryl sulfonate are not used in step b. The specific preparation steps are as follows:

[0058] a. The manganese slag was crushed into fine slag of about 2-5 mm and placed in hot water at 80°C for 24 hours, removed, and soaked and stirred in a 5wt% triethanolamine solution at room temperature for 24 hours until the triethanolamine solution covered the manganese slag, then removed, rinsed with water, dried, and ground into manganese ore powder with a particle size of about 0.05 mm;

[0059] b. The treated manganese ore powder is added to a mixed solution of sodium citrate solution, sodium nitrate solution and potassium fluoride solution at room temperature, reacted for 4 hours, taken out, and then mixed with phthalate and polylactic acid-glycolic acid copolymer, and stirred at room temperature for 24 hours to obtain the modified manganese slag.

[0060] Comparative Example 5:

[0061] This comparative example is in contrast to Example 1. The only difference from Example 1 is that in step b, sodium citrate solution, sodium nitrate solution, and potassium fluoride solution are not used to treat the manganese ore powder. The specific preparation steps are as follows:

[0062] a. The manganese slag was crushed into fine slag of about 2-5 mm and placed in hot water at 80°C for 24 hours, removed, and soaked and stirred in a 5wt% triethanolamine solution at room temperature for 24 hours until the triethanolamine solution covered the manganese slag, then removed, rinsed with water, dried, and ground into manganese ore powder with a particle size of about 0.05 mm;

[0063] b. Add the treated manganese ore powder into 0.05mmol / L Tris-hydrochloric acid buffer solution until it is covered, then add dopamine and sodium lauryl sulfonate, adjust the pH to 9, stir for 3h and let stand for 12h, filter after standing, then mix with phthalate and polylactic acid-glycolic acid copolymer, and stir at room temperature for 24h to obtain the modified manganese slag.

[0064] The modified manganese slag prepared in Example 1 and Comparative Examples 1-5 was subjected to a wastewater treatment test:

[0065] (1) Copper sulfate, lead nitrate, mercuric chloride and cadmium chloride were prepared into a solution to simulate wastewater, so that the concentrations of copper ions, lead ions, mercury ions and cadmium ions in the water were all 10 mg / L;

[0066] (2) adjusting the pH value of the wastewater, and then dividing the wastewater into 1 L portions, and then adding the modified manganese slag prepared in Example 1 and Comparative Examples 1-5 in an amount of 200 g / L, respectively, stirring for 40 min and then standing;

[0067] (3) After standing for 24 hours, filter out the modified manganese slag and detect the concentrations of copper ions, lead ions, mercury ions, and cadmium ions in the separated water.

[0068] 1. The wastewater prepared above was adjusted to pH=5, 9, 13 with lime water, and the modified manganese slag prepared in Example 1 was used in the wastewater, respectively. The results are shown in Table 1:

[0069] Table 1

[0070] <![CDATA[Cu 2+ mg / L]]> <![CDATA[Pb 2+ mg / L]]> <![CDATA[Hg 2+ mg / L]]> <![CDATA[Cd 2+ mg / L]]> pH=5 2.10 3.20 1.70 1.50 pH=9 0.11 0.23 0.02 0.04 pH=13 0.73 0.52 0.25 0.18

[0071] According to the results in Table 1, the modified manganese slag prepared by the present invention has the best removal effect when pH = 9. When the pH is too low and the wastewater is acidic, the modified manganese slag is difficult to capture and flocculate heavy metals. When the pH is too high and the alkalinity is strong, the modified manganese slag undergoes anti-dissolution after capture and flocculation, causing the heavy metal ions accumulated around the modified manganese slag to redissolve in the solution, resulting in a decrease in the removal effect.

[0072] 2. Under the condition that the wastewater was adjusted to pH=9 with lime water, the modified manganese slag prepared in Example 1 and Comparative Examples 1-5 were used to treat the wastewater according to the above method, and the obtained data are shown in Table 2.

[0073] Table 2

[0074]

[0075]

[0076] According to the results in Table 2, the modified manganese slag prepared in Example 1 has a high heavy metal removal rate, reaching more than 95%, especially the best removal effect of mercury ions and cadmium ions. However, in Comparative Example 1, the raw manganese slag is directly crushed and used without other treatment, and only the internal pores are used to adsorb heavy metals, and the effect of removing heavy metals is poor. Compared with Example 1, Comparative Example 2 is not treated with hot water before the modification treatment, resulting in the partial soluble salts in the manganese slag being dissolved and reacting with the raw materials to adhere to the surface of the manganese slag, resulting in a reduction in the removal effect. Comparative Example 3 did not perform step a treatment, did not refine the manganese slag particles and crystalline minerals, and did not perform triethanolamine modification and hot water impurity removal treatment, resulting in the overall particles of the manganese slag being larger and the specific surface area being smaller, the internal structure and crystal form of the manganese slag did not change, and only the surface of the manganese slag could be treated in the later stage, and the amount of heavy metal ions removed was significantly reduced. Comparative Examples 4 and 5 are respectively not adding dopamine, sodium laurel sulfonate and sodium citrate solution, sodium nitrate solution, potassium fluoride solution to modify and activate the manganese slag, resulting in a low removal rate of the modified manganese slag prepared therefrom. The manganese slag surface of Comparative Example 4 does not generate hydrophilic polydopamine, which reduces the modifiability of the manganese slag. Although polydopamine is generated on the surface of Comparative Example 5, no secondary modification is performed to significantly reduce the adsorption. Therefore, Example 1 combines step a and step b to synergistically modify the manganese slag to significantly improve the removal rate of heavy metal ions.

[0077] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should be included in the scope of the claims of the present invention. The techniques, shapes, and structural parts not described in detail in the present invention are all known technologies.

Claims

1. A method for recycling modified manganese slag to treat heavy metal ions, characterized in that: The steps are as follows: (1) Adjust the pH of the heavy metal wastewater to be treated to 9-10 with an alkaline solution; (2) Mix the heavy metal wastewater with the modified manganese slag, stir for 20-40 minutes and then let it stand; (3) After standing for 12-24 hours, filter and carry out subsequent treatment of the separated wastewater; The preparation method of the modified manganese slag comprises the following steps: a. Crush the manganese slag and place it in hot water at 70-80°C for 24 hours. Take it out and soak it in triethanolamine solution at room temperature for 24-36 hours. Take it out and rinse it with water, dry it, and grind it into manganese ore powder; b. Add the treated manganese ore powder into Tris-hydrochloric acid buffer, then add dopamine and sodium laurel sulfate, adjust the pH to 9-10, stir for 3-4 hours and then let stand for 12 hours, filter after standing, add sodium citrate solution, sodium nitrate solution and potassium fluoride solution into a mixed solution at room temperature and react for 4 hours, then take out, mix with phthalate and polylactic acid-glycolic acid copolymer, and stir for 24 hours to obtain the modified manganese slag.

2. The method for recycling and treating heavy metal ions by modified manganese slag according to claim 1, characterized in that: The iron oxide content in the manganese slag is ≤3%.

3. The method for recycling and treating heavy metal ions by modified manganese slag according to claim 2, characterized in that: In the step a, the manganese slag is crushed into fine slag of 2-5 mm, and the particle size of the manganese ore powder is 0.03-0.06 mm.

4. The method for recycling and treating heavy metal ions by modified manganese slag according to claim 3, characterized in that: The concentration of the triethanolamine solution is 5-10wt%.

5. The method for recycling and treating heavy metal ions by modified manganese slag according to claim 4, characterized in that: The mass ratio of the manganese slag to dopamine and sodium laurel sulfonate is 10:(0.5-1):0.

01.

6. The method for recycling and treating heavy metal ions by modified manganese slag according to claim 5, characterized in that: The mass ratio of the manganese slag to the sodium citrate solution, the sodium nitrate solution and the potassium fluoride solution is 1:0.6:1:

1.

7. The method for recycling and treating heavy metal ions by modified manganese slag according to claim 6, characterized in that: The concentrations of the sodium citrate solution, sodium nitrate solution and potassium fluoride solution are 0.2 mol / L, 1 mol / L and 0.1 mol / L respectively.

8. The method for recycling and treating heavy metal ions by modified manganese slag according to claim 7, characterized in that: The mass ratio of the phthalate to the polylactic acid-glycolic acid copolymer is 1:0.4.

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