Mine wastewater water treatment agent, preparation method and application thereof

Abstract

The application discloses a water treatment agent for mine wastewater, a preparation method and application thereof, and belongs to the technical field of wastewater treatment. The water treatment agent comprises porous carbon, an amide group is grafted on the porous carbon, and calcium carbonate is arranged in the pores or on the surface of the porous carbon. The water treatment agent can effectively improve the treatment efficiency of acid mine wastewater and save the treatment process. The application further provides the preparation method and application of the water treatment.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a wastewater treatment agent for mines, its preparation method, and its application. Background Technology

[0002] With the rapid development of the industrial economy, the demand for mineral resources is constantly increasing. The development process generates large amounts of wastewater and tailings, causing serious pollution to the ecological environment. Acid mine drainage (AMD) is a typical type of mine wastewater, originating from the oxidation reaction of sulfide minerals in tailings with oxygen and water in the air. AMD is rich in heavy metal ions and sulfates, and its low pH value easily causes heavy metal pollution, acid pollution, and high salinity pollution, seriously harming the soil environment, ecosystems, and human health.

[0003] Depending on the type of mineral, acidic mine wastewater can be classified into non-ferrous metal mine wastewater, pyrite mine wastewater, coal mine wastewater, and other non-metallic mineral wastewater. These acidic mine wastewaters share common characteristics: they are highly acidic (pH can be as low as 2) and contain a wide variety and abundant amounts of heavy metal ions.

[0004] Traditional technologies for treating acidic mine wastewater mainly include ion exchange, membrane separation, adsorption, neutralization precipitation, microbial methods, and constructed wetlands. Ion exchange suffers from problems such as low initial saturation, poisoning, aging and failure, frequent regeneration, and high investment costs. Membrane separation uses relatively expensive membranes and is difficult to apply to highly acidic wastewater. Neutralization precipitation requires external reagents, leading to high costs. Microbial and constructed wetland methods have stringent environmental requirements. Overall, adsorption offers the best treatment effect and is the most promising method, but it is inefficient and requires a long process.

[0005] In summary, it is necessary to try to optimize the adsorption method to improve the treatment efficiency of acidic mine wastewater and save on treatment processes. Summary of the Invention

[0006] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a water treatment agent that can effectively improve the treatment efficiency of acidic mine wastewater and save on treatment processes.

[0007] The present invention also provides a method for preparing the above-mentioned water treatment agent.

[0008] The present invention also provides applications of the above-mentioned water treatment agent.

[0009] According to an embodiment of a first aspect of the present invention, a mine wastewater treatment agent is provided, the agent comprising:

[0010] Porous carbon, wherein amide groups are grafted onto the porous carbon;

[0011] Calcium carbonate, wherein the calcium carbonate is disposed in the pores or on the surface of the porous carbon.

[0012] The water treatment agent according to embodiments of the present invention has at least the following beneficial effects:

[0013] Mine wastewater is usually acidic (rich in sulfate ions) and contains heavy metal ions such as lead, copper, and cadmium.

[0014] Acidity not only increases the migration of heavy metal ions in mine wastewater but also causes acidification of water bodies and soil, damaging the environment. The water treatment agent provided by this invention incorporates calcium carbonate, which can react with acid, within the pores of porous carbon. This raises the pH of the mine wastewater near the agent, reducing the migration of heavy metal ions (leading to the formation of hydroxide precipitates, etc.). The resulting precipitates can adhere to the porous carbon, even penetrating deep into its pores and being immobilized. Compared to water treatment agents that simply mix calcium carbonate and porous carbon, the water treatment agent provided by this invention exhibits a synergistic effect between calcium carbonate and porous carbon, not only raising the pH of the mine wastewater but also immobilizing, to a certain extent, the insoluble substances formed by heavy metal ions.

[0015] Furthermore, considering the unique characteristics of mine wastewater, the main product of the reaction between calcium carbonate and mine wastewater is calcium sulfate, which has very low solubility in water and, like insoluble heavy metal ions, adheres to porous carbon. In other words, the water treatment agent provided by this invention, in addition to improving the acidity and heavy metal ion pollution of mine wastewater, can also remove sulfate ions to a certain extent. Most importantly, it does not introduce a large amount of ionic impurities (it will increase a small amount of calcium ions).

[0016] In addition, porous carbon has a high pore size structure, and with the adsorption and complexation of amide groups, it can adsorb and fix heavy metal ions that have not become insoluble due to pH changes, thereby further reducing the content of heavy metal ions in the treated wastewater.

[0017] Finally, the used water treatment agent can be calcined under oxygen-free conditions, whereby the porous carbon can reduce the insoluble heavy metal ions; the calcined products mainly include anhydrous calcium sulfate and heavy metal elements, which can be further separated by differences in specific gravity and other factors.

[0018] In summary, the water treatment agent provided by this invention exhibits a synergistic effect between the porous carbon structure, calcium carbonate component, and mine wastewater component, as well as a synergistic effect between the porous carbon structure and amide groups. This significantly improves the treatment efficiency of mine wastewater and reduces the number of steps in mine wastewater treatment.

[0019] According to some embodiments of the present invention, the pH of the mine wastewater at 25°C is 2.0 to 6.0. For example, it can be 2.5 to 3.

[0020] According to some embodiments of the present invention, the mine wastewater includes suspended solids, sulfate ions, and metal ions. Wherein:

[0021] The concentration of the suspended solids is 11–158 mg / L. Specifically, it could be 50–100 mg / L. More specifically, it could be approximately 75 mg / L.

[0022] The concentration of sulfate is 0.04–13 mmol / L. For example, it can be 5–10 mmol / L. For example, it can be approximately 8.5 mmol / L.

[0023] The metal ions include Cu 2+ Pb 2+ Zn 2+ Cd 2+ Mn 2+ and Fe 3+ At least one of them.

[0024] The Cu 2+ The concentration is 0.01–0.65 mg / L. For example, it can be 0.3–0.35 mg / L. More specifically, it can be about 0.31 mg / L.

[0025] The Pb 2+ The concentration is 0.01–0.95 mg / L. Specifically, it could be 0.5–0.6 mg / L. More specifically, it could be approximately 0.55 mg / L.

[0026] The Zn 2+ The concentration ranges from 0.02 to 286 mg / L. Specifically, it could be 100 to 150 mg / L. More specifically, it could be approximately 137 mg / L.

[0027] The Cd 2+ The concentration is 0.001–3.0 mg / L. For example, it could be 2–3 mg / L. More specifically, it could be approximately 2.5 mg / L.

[0028] The Mn 2+ The concentration is 0.1–2 mg / L. For example, it can be 1–1.5 mg / L. More specifically, it can be about 1.1 mg / L.

[0029] The Fe 3+ The concentration is 8–15 mg / L. Specifically, it could be 10–14 mg / L. More specifically, it could be approximately 12 mg / L.

[0030] According to some embodiments of the present invention, the amide group is derived from at least one of acrylamide and cinnamamide.

[0031] According to some embodiments of the present invention, the grafting rate of amide groups on the porous carbon is 20-30%. Specifically, it can be about 23%.

[0032] Unless otherwise specified, the grafting rate is the ratio of the number of amide groups grafted to the number of original hydroxyl and carboxyl groups on the porous carbon; the grafting rate is usually characterized and calculated by infrared spectroscopy or other methods.

[0033] According to some embodiments of the present invention, the porous carbon has a pore size of 0.1–5 nm. This pore size is larger than the ionic radius of calcium ions and heavy metal ions, but small enough to immobilize solid particles such as calcium carbonate. Specifically, it can be 0.2–1.5 nm.

[0034] According to some embodiments of the present invention, the specific surface area of ​​the porous carbon is 2000-3000 m². 2 / g. A larger specific surface area indicates a richer microporous structure, which is more conducive to the fixation of calcium carbonate and other substances, and also more conducive to the adsorption of heavy metal ions. For example, it can be 2500–2600 μm. 2 / g.

[0035] According to some embodiments of the present invention, the particle size of the porous carbon is 1 to 10 mm. For example, it can be 2 to 3 mm.

[0036] According to some embodiments of the present invention, the porous carbon includes at least one of activated carbon and bio-based pyrolytic carbon.

[0037] According to some embodiments of the present invention, the mass ratio of calcium carbonate to porous carbon is 0.5 to 1:1. Within this range, the porous carbon still has sufficient pore structure to achieve adsorption performance, and the amount of calcium carbonate it contains is also sufficient to adjust the pH.

[0038] According to some embodiments of the present invention, the mass ratio of calcium carbonate to porous carbon is 0.8 to 0.9:1.

[0039] According to an embodiment of a second aspect of the present invention, a method for preparing the aforementioned water treatment agent is provided, the method comprising the following steps:

[0040] S1. Grafting amide groups onto porous carbon precursors;

[0041] S2. Mix the intermediate product obtained in step S1 with the calcium acetate solution;

[0042] S3. Dry the mixture obtained in step S2 in a carbon dioxide atmosphere.

[0043] Since the preparation method employs all the technical solutions of the water treatment agents described in the above embodiments, it possesses at least all the beneficial effects brought about by the technical solutions of the above embodiments. Furthermore, the preparation method is simple, easy to operate, and facilitates large-scale production.

[0044] According to some embodiments of the present invention, in step S1, the porous carbon precursor contains hydroxyl and carboxyl groups.

[0045] The porous carbon precursor is commercially available. Some commercially available products contain the hydroxyl and carboxyl groups. If the content is low, the porous carbon precursor can be mixed with an oxidizing acid or oxidant before grafting. The oxidizing acid includes sulfuric acid. The oxidant includes hydrogen peroxide. In actual production, the content of hydroxyl and carboxyl groups on the porous carbon precursor can be adjusted by adjusting the concentration of the oxidizing acid / oxidant and the mixing time.

[0046] The porous carbon precursor contains 1-5% oxygen. This includes oxygen from hydroxyl and carboxyl groups. This oxygen content can be determined using XPS testing. For example, it could be 3-4%.

[0047] According to some embodiments of the present invention, in step S1, the grafting process includes polymerizing the porous carbon precursor, the amide precursor and the olefinic acid.

[0048] According to some embodiments of the present invention, the amide precursor includes at least one of acrylamide and cinnamamide.

[0049] According to some embodiments of the present invention, the acrylic acid includes at least one of acrylic acid and methacrylic acid.

[0050] According to some embodiments of the present invention, in step S1, the grafting process is carried out under the action of an initiator. The initiator includes ferrous sulfate and hydrogen peroxide. The interaction of the two can generate oxidizing free radicals, which promote the polymerization of double bonds in the olefinic acid and amide precursor, and promote the reaction between the carboxyl groups in the olefinic acid and the hydroxyl groups on the porous carbon precursor, resulting in a stable chemical grafting effect.

[0051] According to some embodiments of the present invention, the mass percentage of ferrous sulfate and hydrogen peroxide (30% concentration) in the initiator is 0.8 to 1.1:1. Specifically, it can be about 1:1.

[0052] According to some embodiments of the present invention, the initiator accounts for 10-20% of the mass percentage of the porous carbon precursor. Specifically, it may be about 15%.

[0053] According to some embodiments of the present invention, the mass ratio of the amide precursor to the porous carbon precursor is 1 to 2:1. For example, it can be about 1.5:1.

[0054] According to some embodiments of the present invention, the molar ratio of the amide precursor to the olefinic acid is 0.5 to 1:1. Specifically, it can be about 0.8:1.

[0055] According to some embodiments of the present invention, in step S1, the grafting temperature is 65–85°C. For example, it can be approximately 70°C.

[0056] According to some embodiments of the present invention, in step S1, the grafting time is 0.5 to 2 hours. For example, it can be about 1 hour.

[0057] According to some embodiments of the present invention, step S1 is performed in a protective atmosphere. Unless otherwise specified, the protective atmosphere in the present invention includes at least one of nitrogen and argon.

[0058] According to some embodiments of the present invention, step S1 specifically includes:

[0059] The porous carbon precursor was homogenized with water, and the initiator was added to the resulting slurry; then the amide precursor and olefinic acid were added for grafting.

[0060] The grafted product was subjected to solid-liquid separation, washing, and drying in sequence.

[0061] According to some embodiments of the present invention, in the water homogenization, the mass-to-volume ratio of the porous carbon precursor to water is 1 g: 5-10 mL. For example, it can be approximately 1 g: 8 mL.

[0062] According to some embodiments of the present invention, in step S2, the concentration of the calcium acetate solution is 150–350 g / L. The ratio of the volume of the calcium acetate solution to the mass of the intermediate product obtained in step S1 can be determined based on the required mass of calcium carbonate to be loaded, as long as the calcium acetate solution can completely wet the intermediate product.

[0063] According to some embodiments of the present invention, in step S2, the concentration of the calcium acetate solution is 150–350 g / L. Specifically, it can be 200–330 g / L. More specifically, it can be about 250 g / L or 310 g / L.

[0064] According to some embodiments of the present invention, in step S3, the drying temperature is 40–80°C. No solid-liquid separation is performed between steps S2 and S3; therefore, the proportion of calcium carbonate in the obtained water treatment agent can be determined by the material ratio in step S2. Further, drying is performed in a carbon dioxide atmosphere, where the calcium acetate in step S2 is converted to calcium carbonate, and the generated acetic acid volatilizes and escapes from the water treatment agent.

[0065] According to an embodiment of a third aspect of the present invention, a method for treating mine wastewater is provided, the method comprising passing the mine wastewater through the aforementioned water treatment agent.

[0066] Since the treatment method employs all the technical solutions of the water treatment agents described in the above embodiments, it possesses at least all the beneficial effects brought about by the technical solutions of the above embodiments. That is, the water treatment method has simple steps.

[0067] According to some embodiments of the present invention, in the treatment method, the water treatment agent is filled in a columnar container. The ratio of the stacking height of the water treatment agent to the diameter of the columnar container is 5 to 10:1.

[0068] In the treatment method, the content of metal ions in the water passing through the water treatment agent can be monitored. If it exceeds a set value, the water treatment agent needs to be replaced.

[0069] According to an embodiment of the fourth aspect of the present invention, the application of the water treatment agent in the construction of artificial wetlands is provided.

[0070] Since the constructed wetland adopts all the technical solutions of the water treatment agent in the above embodiments, it has at least all the beneficial effects brought about by the technical solutions in the above embodiments.

[0071] Unless otherwise specified, the term "about" in this invention actually means that the error is allowed to be within ±2%, for example, about 100 is actually 100 ± 2% × 100.

[0072] Unless otherwise specified, "between" in this invention includes the number itself, for example, "between 2 and 3" includes the endpoint values ​​2 and 3.

[0073] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Detailed Implementation

[0074] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0075] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0076] Unless otherwise specified, the following applies to the specific implementation methods:

[0077] The porous carbon precursor was purchased from Shanghai Lekang Activated Carbon Co., Ltd. It had a particle size of approximately 2 mm (micrometer, 100 samples tested, average value taken), was spherical, and had a specific surface area of ​​2600 m². 2 / g(BET), pore size distribution between 0.2 and 1.5 nm (BET); oxygen content is approximately 4% (XPS).

[0078] The mine wastewater has a pH of approximately 2.5, a suspended solids concentration of 75 mg / L, a sulfate concentration of approximately 8.5 mmol / L, and a Cu content of approximately 8.5 mmol / L. 2+ The concentration was 0.31 mg / L, Pb 2+ The concentration is 0.57 mg / L, Zn 2+ The concentration was 137 mg / L, Cd 2+ The concentration was 2.4 mg / L, Mn 2+ The concentration was 1.1 mg / L, Fe 3+ The concentration is 12 mg / L.

[0079] Example 1

[0080] This example demonstrates the preparation of a water treatment agent. The specific preparation steps are as follows:

[0081] S1. Under argon protection, amide groups are grafted onto a porous carbon precursor; specifically:

[0082] The porous carbon precursor was homogenized with water at a mass-to-volume ratio of 1g:8mL.

[0083] Add an initiator accounting for 15% of the mass of the porous carbon precursor to the obtained slurry and stir until homogeneous; the mass ratio of ferrous sulfite to hydrogen peroxide (30% concentration) in the initiator is 1:1.

[0084] Add 1.5 times the mass of porous carbon precursor acrylamide and 0.8 times the molar mass of acrylamide methylallylic acid to the obtained slurry; heat to 70℃ and react for 1 hour;

[0085] Solid-liquid separation was then performed, followed by washing with water and drying to obtain an intermediate product. Infrared spectroscopy revealed that the grafting rate of amide groups in this intermediate product was approximately 23%.

[0086] S2. Mix the intermediate product obtained in step S1 with the calcium acetate solution; the concentration of the calcium acetate solution is 2 mol / L, and the mass-to-volume ratio of the intermediate product to calcium acetate is 1 g: 4 mL.

[0087] S3. Dry the mixture obtained in step S2 in a carbon dioxide atmosphere; the drying temperature is about 60°C.

[0088] Example 2

[0089] This example prepares a water treatment agent, which differs from Example 1 in that:

[0090] In step S2, the concentration of the calcium acetate solution is 1.5 mol / L.

[0091] Comparative Example 1

[0092] This example demonstrates the preparation of a water treatment agent, specifically:

[0093] The product obtained in step S1 of Example 1 was mixed with 80% by mass of nano-calcium carbonate (purchased from Xianfeng Nano, with a particle size of 40-80 nm).

[0094] Comparative Example 2

[0095] This example prepares a water treatment agent, which differs from Example 1 in that:

[0096] Step S1 is excluded; the porous carbon precursor raw material used in Example 1 is used directly for steps S2 to S3.

[0097] Application examples

[0098] This example uses the water treatment agent obtained from the embodiments and comparative examples to treat mine wastewater. Specifically:

[0099] The mine wastewater is passed through a column filled with a water treatment agent, the column having an aspect ratio of 8:1; in this example, the diameter used is 5cm. In actual production, the column diameter can be adjusted according to the required production capacity, test conditions, etc., and the above aspect ratio can also be adjusted according to the required interval for replacing the water treatment agent.

[0100] Test case

[0101] This example tested the pH, suspended solids (standard gravimetric method, calculating the weight gain of the filter paper to the mass ratio of the filtered water after passing through filter paper at 103–105°C), sulfate content (ion chromatography), and metal ion content (ICP-OES) of the influent and effluent. The effluent was taken as the water from the second column volume; for example, if the column volume is 1L, then the second L of water passing through the column was taken as the effluent for testing. The test results are shown in Table 1.

[0102] Table 1 shows the influent and effluent water quality when using different water treatment agents.

[0103]

[0104]

[0105] According to the results in Table 1, the water treatment agent prepared by this invention has the functions of pH adjuster, adsorbent and filter layer. It can significantly reduce the content of suspended solids and metal ions in water, and at the same time increase the pH of the water. The water quality of the treated water meets the water quality standards for industrial wastewater reuse specified in GB / T19923-2005.

[0106] Comparing Examples 1 and 2, it can be seen that reducing the amount of calcium carbonate results in a decrease in the calcium carbonate content on the surface of the water treatment agent, thus slightly reducing its pH-raising effect and the proportion of metal ion hydroxides generated. Therefore, the effluent quality of Example 2 is slightly lower than that of Example 1. In actual production, by adjusting the column's length-to-diameter ratio and using the water treatment agent obtained in Example 2, it is expected that better effluent quality can be obtained.

[0107] Comparing Example 1 and Comparative Example 1, it is evident that if nano-calcium carbonate does not form a loading layer with porous carbon, the calcium carbonate powder is easily washed out of the column and loses its performance. In other words, the water treatment agent obtained in Comparative Example 1 failed to exert the synergistic effect between calcium carbonate and porous carbon. Furthermore, the nano-calcium carbonate used in Comparative Example 1 can itself be considered a suspended solid. Therefore, the parameters obtained, such as the suspended solids, pH, and heavy metal ion content of the water, are all inferior to those of Example 1. The comparison between Example 1 and Comparative Example 1 also demonstrates that there is a synergistic effect between porous carbon and calcium carbonate in the water treatment agent provided by this invention.

[0108] Comparing Example 1 and Comparative Example 2, it can be seen that if the porous carbon is not modified with amide groups, it is equivalent to omitting the flocculation and adsorption effects of polyamide. Therefore, the content of suspended solids and heavy metal ions in the resulting water is higher than that in the Example, but the quality of the effluent is slightly better than that in Comparative Example 1.

[0109] In summary, the water treatment agent provided by this invention exhibits a synergistic effect among its components, significantly improving the quality of the treated water. Due to its unique mechanism of action, the resulting water treatment agent is also expected to be used in wetland construction, for example, as a substrate for ponds.

[0110] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A method for preparing a water treatment agent for mine wastewater, characterized in that, The preparation method includes the following steps: S1. Grafting amide groups onto a porous carbon precursor; the grafting process includes polymerizing the porous carbon precursor, the amide precursor, and an acrylate; the amide precursor includes at least one of acrylamide and cinnamamide; the acrylate includes at least one of acrylic acid and methacrylic acid; S2. Mix the intermediate product obtained in step S1 with the calcium acetate solution; S3. Dry the mixture obtained in step S2 in a carbon dioxide atmosphere; The water treatment agent is composed of the following components: Porous carbon, wherein amide groups are grafted onto the porous carbon; Calcium carbonate, wherein the calcium carbonate is disposed in the pores or on the surface of the porous carbon; The mass ratio of calcium carbonate to porous carbon is 0.5 to 1:

1.

2. The preparation method according to claim 1, characterized in that, The grafting rate of amide groups on the porous carbon is 20-30%.

3. The preparation method according to claim 1, characterized in that, The porous carbon has a pore size of 0.1~5nm; and / or, the porous carbon has a particle size of 1~10mm.

4. The preparation method according to claim 1, characterized in that, In step S2, the concentration of the calcium acetate solution is 150~350 g / L.

5. A method for treating mine wastewater, characterized in that, The treatment method includes treating the mine wastewater with a water treatment agent prepared by any one of the preparation methods described in claims 1 to 4.

6. The application of a water treatment agent prepared by the preparation method according to any one of claims 1 to 4 in the construction of artificial wetlands.

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