A heavy metal ion adsorbent, its preparation method and application

Abstract

This invention discloses a method for preparing a heavy metal ion adsorbent, the heavy metal ion adsorbent itself, and its applications. The preparation method includes the following steps: obtaining a mixture of steel slag and red mud; adding water to the mixture obtained in the above step and wet-milling it using a ball mill to obtain slurry 1; introducing CO2 gas into slurry 1 under stirring conditions to carbonize the modified porous framework particles in slurry 1 to obtain slurry 2; and filtering slurry 2 to obtain a solid, washing the solid until the pH is neutral, and drying it to obtain the heavy metal ion adsorbent. This invention uses two industrial solid wastes, steel slag and red mud, as reaction raw materials, resulting in low cost. It prepares a porous adsorbent material loaded with nano-calcium carbonate at room temperature, exhibiting high adsorption efficiency, and realizing high-value utilization of steel slag and red mud for wastewater treatment.

Description

Technical Field

[0001] This invention belongs to the field of solid waste treatment technology, and in particular relates to a method for preparing carbonized modified heavy metal adsorbents for removing heavy metal ions from water using solid waste (such as steel slag, red mud, etc.), the carbonized modified heavy metal adsorbents prepared by this method, and their applications. Background Technology

[0002] Steel slag is a solid waste generated by the steel industry. Approximately 1.5 to 2.5 tons of steel slag are produced as a byproduct of every ton of crude steel produced. In 2020, China's steel slag production reached 160 million tons. Open-air stockpiling of steel slag not only occupies a large amount of land, but the heavy metals within it can also be washed into water sources and soil by rainwater, causing groundwater and soil pollution, affecting plant growth and human health. While steel slag is currently used in industries such as cement and concrete, its added value is low, necessitating the development of high-value utilization technologies.

[0003] Red mud, also known as red clay, is an industrial solid waste discharged after alumina extraction from bauxite. It is an insoluble residue and can be classified into sintering process red mud, Bayer process red mud, and combined process red mud. Large quantities of red mud cannot be fully and effectively utilized and are instead dumped in large-scale stockpiles, occupying vast amounts of land and causing serious environmental pollution. The generation of large quantities of red mud has already had multifaceted direct and indirect impacts on human production and daily life. Therefore, minimizing the production and harm of red mud and achieving multi-channel, large-scale resource utilization is urgently needed.

[0004] In recent years, environmental pollution has become a major concern. With industrial development, the problem of heavy metal wastewater from industries such as non-ferrous metal production, mining, and chemicals has become increasingly serious. This pollution not only severely damages the ecological environment but also causes considerable harm to human health. Lead can easily cause anemia, damage brain cells, leading to congenital intellectual disability, neurological dysfunction, and kidney damage. Cadmium hinders the body's absorption of calcium, leading to osteoporosis, fractures, bone pain, bone damage, and even cancer. Even if the concentration of heavy metals discharged in wastewater is very low, it can still cause pollution due to bioaccumulation. Therefore, it is necessary to actively explore technologies for treating heavy metal wastewater to alleviate water pollution.

[0005] Existing methods for treating heavy metal wastewater include adsorption, sedimentation, coagulation, ion exchange, membrane separation, and solvent extraction. Adsorption is widely used due to its high efficiency, simple operation, and wide applicability. Traditional adsorbents include activated carbon, zeolite, kaolin, graphene, clay, and cellulose. However, these adsorbents suffer from low adsorption efficiency and non-renewability. Therefore, there is a need to find a novel adsorbent material that is highly efficient in treating heavy metal wastewater.

[0006] In this regard, patent application number CN202211627722.0 discloses a magnetic biochar composite adsorbent, its preparation method, and its application in adsorbing heavy metal chromium (VI). The steps are as follows: Waste biomass materials are washed, dried, crushed, and sieved to obtain biochar raw materials; the biochar raw materials are mixed with an alkaline solution to remove impurities, and then washed and dried to obtain alkaline biochar; the alkaline biochar is thoroughly mixed with a methanol solution of polyethyleneimine, and then cross-linked with a glutaraldehyde solution to obtain amino-modified biochar; carboxyl tetraoxide is then added to the adsorbent. Ferromagnetic nanospheres were ultrasonically dispersed in 2-morpholine ethanesulfonic acid buffer, and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide were added. The mixture was ultrasonically dispersed until homogeneous, and then shaken on a shaker for 10–30 min. After centrifugation, activated carboxylated iron oxide nanoparticles were obtained. The prepared amino-modified biochar was dispersed in buffer, and the activated carboxylated iron oxide nanoparticles were added. After ultrasonic mixing, the mixture was shaken on a shaker overnight. The product was magnetically separated, washed, and dried to obtain a magnetic biochar composite adsorbent.

[0007] Patent application CN201810465390.8 discloses an adsorbent based on waste steel slag, its preparation method, and its application. It utilizes the oxidation products generated from impurities in pig iron during the steelmaking process. After magnetic separation and sieving, steel slag tailings with a fineness of less than 150 mesh and an iron content of less than 5% are obtained. Then, 20% grinding aid and 30% surfactant are added and the mixture is ground together. Finally, it is washed with 15% HCl to obtain an adsorbent based on the treatment of Cr-containing waste steel slag. 6+ A novel adsorbent for wastewater.

[0008] Although the aforementioned adsorbents utilize waste biomass materials or steel slag at low cost, their adsorption efficiency still needs improvement. Therefore, it is necessary to further improve the preparation method of steel slag-based heavy metal adsorbents to enhance their adsorption effect on various heavy metal ions, while simultaneously utilizing steel slag and / or red mud and other solid wastes. Summary of the Invention

[0009] To address the aforementioned problems, the present invention aims to provide a carbonized modified steel slag-based heavy metal ion adsorbent for removing heavy metal ions from water, its preparation method, and its application. The heavy metal adsorbent treated by this method has a porous and loose framework with nano-sized carbonate particles loaded on the surface of the framework, resulting in a large specific surface area and a synergistic adsorption effect on heavy metal ions, thus achieving good adsorption performance for heavy metal ions.

[0010] According to one embodiment of the present invention, the preparation method of the provided heavy metal ion adsorbent includes the following steps:

[0011] S1: Grind and sieve the dried steel slag and dried red mud separately, and then disperse and mix the sieved steel slag and red mud to obtain a mixture of steel slag and red mud;

[0012] S2: Add water to the mixture of steel slag and red mud obtained in step S1, stir, and wet grind using a ball mill to obtain slurry 1 containing porous particles;

[0013] S3: Under stirring conditions, CO2 gas is introduced into the slurry 1 obtained in step S2 to carbonize the modified porous framework particles in slurry 1, resulting in slurry 2, which contains a porous framework and nano-carbonate particles supported on the pore surface; and

[0014] S4: After filtering the slurry 2 from step S3, a solid is obtained. The solid is washed until the pH is neutral and then dried (e.g., heated to the boiling point of water to evaporate the water) to obtain the heavy metal ion adsorbent.

[0015] The carbonation described in this invention refers to the process by which hydroxides or metal ions in slurry 1 react with CO2 to form carbonates.

[0016] Figure 1 A process flow diagram for preparing heavy metal ion adsorbents according to the present invention is shown. Figure 1 As shown, the overall process for preparing heavy metal ion adsorbent according to the present invention includes drying steel slag and red mud separately and then mixing and ball milling them. Water is added to the obtained mixture, and wet milling is performed to obtain slurry 1. Carbon dioxide is introduced into slurry 1 for carbonization to obtain slurry 2. Slurry 2 is filtered and boiled to obtain the adsorbent.

[0017] More specifically, the preparation method of the present invention relates to a carbonized modified steel slag-based adsorbent for removing heavy metal ions from water and a method for preparing the same.

[0018] According to the above preparation method, this invention generates sodium silicate and sodium aluminate by alkali erosion of steel slag and aluminosilicates in red mud, creating pores in the steel slag and red mud particles. Subsequently, insoluble nano-carbonates formed through carbonization adhere to the framework surface, increasing the specific surface area of ​​the adsorbent. Furthermore, the synergistic effect of red mud and steel slag enhances the reactivity of the aluminosilicate, increases the number of active sites on the adsorbent surface, and improves the adsorption rate of heavy metal ions in water.

[0019] The following describes steps S1 to S4 of the preparation method of the present invention.

[0020] Step S1 is a pretreatment step for metallurgical solid waste raw materials such as steel slag and red mud. Specifically, in step S1, the steel slag and red mud can be dried and then ball-milled separately. The ball-milled steel slag and red mud are then sieved through a 100-200 mesh sieve. The sieved steel slag and red mud are then dispersed and mixed, and homogenized to obtain a mixture of steel slag and red mud.

[0021] Preferably, the grinding time for the dried steel slag and dried red mud in step S1 is 20-60 minutes. This step can increase the contact area between the steel slag and the red mud.

[0022] The mass ratio of the dried steel slag to the dried red mud in step S1 is 1:0.2-4.0.

[0023] Step S2 yields porous steel slag and red mud particles, as well as alkali metal hydroxides. In one example, step S2 includes adding distilled water to the steel slag and red mud mixture prepared in step S1, stirring thoroughly, and then wet-milling using a small ball mill to obtain slurry 1. The wet-milling time in step S2 is 0.2-3.5 hours, and the rotation speed is 50-100 rpm. The mass ratio of the steel slag and red mud mixture to water in step S2 is 1:2.0-6.0; preferably, the water is distilled water.

[0024] Through the above-described thorough wet grinding, a slurry 1 containing porous steel slag and red mud particles, as well as alkali metal hydroxides, can be formed. The solid content in slurry 1 can be 40-60% by weight. This step utilizes the alkali in the red mud to activate the steel slag, increasing the number of active sites on the adsorbent surface and eroding the steel slag and red mud particles, forming loose, porous particles with a large specific surface area.

[0025] Specifically, wet milling of steel slag and red mud at room temperature produces porous particles, primarily composed of calcium and silica-alumina. The chemical composition of the steel slag is as follows: CaO 36.92%, SiO2 17.34%, Fe2O3 20.28%, MgO 6.82%, Al2O3 4.54%, MnO 7.74%, P2O5 2.78%, and K2O 0.06%. The main chemical compositions of the red mud are: Al2O3 25.6%, SiO2 18.54%, CaO 20.10%, Fe2O3 4.39%, and Na2O 8.29%.

[0026] During wet grinding, free calcium oxide and magnesium oxide in the steel slag dissolve in the slurry, forming alkali metal hydroxides (preferably calcium hydroxide and magnesium hydroxide). Simultaneously, Na₂O in the red mud dissolves into the slurry, creating an alkaline environment that erodes the aluminosilicates in the steel slag and red mud, forming sodium silicate and sodium aluminate. This creates pores in the steel slag and red mud particles, forming a porous framework, including a porous steel slag framework and a porous red mud particle framework, while simultaneously increasing the specific surface area of ​​the reaction.

[0027] Step S3 involves loading nano-carbonates (preferably at least one of calcium carbonate and magnesium carbonate). In one example, step S3 includes introducing CO2 into slurry 1 obtained in step S2 and using magnetic stirring to fully carbonize the metal hydroxides, steel slag, and red mud phases in slurry 1 to obtain slurry 2. Slurry 2 comprises a porous framework and nano-carbonate particles loaded on the pore surface.

[0028] In particular, after carbon dioxide is introduced, it reacts with the calcium hydroxide and magnesium hydroxide generated in step S2, as well as the mineral phases (tricalcium silicate and dicalcium silicate, etc.) of the steel slag and red mud itself, to form nano-calcium carbonate and magnesium carbonate, which are loaded onto the framework. This further increases the reaction area between the adsorbent and heavy metal ions.

[0029] Preferably, adding alkalis such as sodium hydroxide and calcium hydroxide in step S3 can promote the formation of the skeleton.

[0030] In step S3, the purity of the CO2 gas can be 95% to 99%, the flow rate is 0.2-1.2 L / min, the carbonization temperature is 50-75℃, the reaction time is 1.1-2.5 h, and the stirring rate is 300-1800 rpm.

[0031] In one example, the preparation method of the present invention may further include S2-1 after step S2: adding sodium humate solution to slurry 1 and mixing evenly to obtain slurry 3 containing alkali metal ions activated by sodium humate, wherein the amount of sodium humate added is 0.03-0.10% by weight relative to the total weight of dried steel slag and dried red mud.

[0032] The step S3 includes introducing CO2 gas into the slurry 2-1 obtained in step S2-1 at room temperature to carbonize the activated alkali metal in the slurry 2-1 to obtain slurry 3, while releasing fulvic acid in the water.

[0033] By adding a sodium humate solution to slurry 1 before step S3, alkali metal ions activated by sodium humate are obtained, which further improves the carbonization efficiency in step S3. Sodium humate is a water- or acid-soluble humic acid macromolecule that is weakly basic. The basic structure of sodium humate consists of aromatic and alicyclic rings, with functional groups such as carboxyl, hydroxyl, carbonyl, quinone, and methoxy groups attached to the rings. These groups can exchange with heavy metal ions and exhibit heavy metal adsorption capabilities. The complexation effect of sodium humate promotes the leaching of calcium and magnesium ions from the steel slag in slurry 1, thereby accelerating the carbonization reaction of calcium and magnesium ions with dissolved carbon dioxide and promoting the formation of nano-sized carbonate particles. Simultaneously, the carbonization reaction also releases fulvic acid into the water, which can be washed away in subsequent steps.

[0034] Therefore, by adding sodium humate solution, the carbonization reaction in step S3 can be carried out under very mild conditions, such as room temperature, atmospheric pressure, and a low carbon dioxide flow rate. Preferably, in step S3, the carbon dioxide flow rate introduced into slurry 2 is 0.2-1.2 L / min, the carbonization temperature is 20-30℃, the reaction time is 0.5-1 h, and the stirring rate is 300-600 rpm.

[0035] In another aspect, the present invention also provides a heavy metal ion adsorbent prepared by any of the methods described above. The heavy metal ion adsorbent of the present invention comprises a porous framework and nano-carbonates covering the surface of the framework.

[0036] More preferably, the present invention also provides a preparation method comprising:

[0037] S1: Grind and sieve the dried steel slag and dried red mud separately, and then disperse and mix the sieved steel slag and red mud to obtain a mixture of steel slag and red mud;

[0038] S2: Add water to the mixture of steel slag and red mud obtained in step S1, stir, and wet grind using a ball mill to obtain slurry 1 containing porous particles;

[0039] S2-1: After step S2, sodium humate solution is added to slurry 1 and mixed evenly to obtain slurry 2-1, wherein the amount of sodium humate added is 0.03-0.10% by weight relative to the total weight of dried steel slag and dried red mud;

[0040] S3: Under stirring conditions, CO2 gas is introduced into the slurry 2-1 obtained in step S2-1 to carbonize the modified porous aluminosilicate framework particles in slurry 2-1, resulting in slurry 2. This slurry 2 contains a porous aluminosilicate gel framework and nano-carbonate particles supported on the pore surface; and

[0041] S4: After filtering the slurry 2 from step S3, a solid is obtained. The solid is washed until the pH is neutral and then dried to obtain the heavy metal ion adsorbent.

[0042] As calcium hydroxide and magnesium hydroxide are formed, they clog the pores in the steel slag and red mud, preventing some calcium oxide and magnesium oxide from dissolving. Therefore, preferably, the applicant introduces step S2-1 between steps S2 and S3, adding sodium humate solution to slurry 1, mixing thoroughly, and preferably continuing wet milling to obtain slurry 2-1. Since sodium humate chelates with free calcium and magnesium ions in the aqueous solution, it can greatly promote the dissolution of calcium oxide and magnesium oxide. The chelates of calcium and magnesium ions are not as stable as hydroxides and carbonates; therefore, after chelate formation, they are converted back into magnesium hydroxide and calcium hydroxide, and then further converted into calcium carbonate and magnesium carbonate in step S3. Fulvic acid and its soluble salts are removed by washing in step S4.

[0043] In another aspect, the present invention also provides the application of the above-mentioned heavy metal ion adsorbent in the removal of heavy metal ions from wastewater.

[0044] In particular, the adsorbent prepared by the present invention can be used for the adsorption treatment of heavy metal wastewater, wherein the heavy metal ions are lead ions, cadmium ions, copper ions, chromium ions, etc., and the adsorption rate of heavy metals is ≥60%, preferably ≥62%, ≥65%, ≥70%, ≥75%, ≥80%, ≥85%, ≥90%, ≥95%, or ≥97%.

[0045] Compared with the prior art, the beneficial technical effects of this invention are:

[0046] This invention modifies steel slag and red mud by erosion with alkali in red mud, and by leveraging the synergistic effect of steel slag and red mud, a loose and porous steel slag and red mud particle skeleton is prepared. At the same time, the subsequent carbonization modification coats the surface of the skeleton with some nano carbonate particles, which increases the specific surface area of ​​the adsorbent, increases the number of active sites on the surface of the adsorbent, and improves the adsorption capacity of the adsorbent for heavy metal wastewater.

[0047] Although not bound by theoretical constraints, it is believed that the mechanism by which nano-carbonate particles promote heavy metal adsorption is partly due to their increased specific surface area, and partly due to their inherent chemisorption capacity. Carbonates are calcium carbonate and magnesium carbonate. Nano-carbonates are calcium carbonate and magnesium carbonate, and are insoluble in water.

[0048] In particular, different crystal faces of nano-carbonate crystals carry different charges; the 110 crystal face carries a negative charge. Based on this, it is speculated that nano-carbonate crystals more readily adsorb positively charged metal ions, which are then adsorbed onto the negatively charged 110 crystal face, resulting in a stronger adsorption capacity of nano-carbonate crystals for metal cations. Therefore, the adsorption of metal cations by nano-carbonate crystals is mostly chemisorption, accompanied by a small portion of physisorption.

[0049] In addition, the method of the present invention can also add sodium humate as a chelating agent to promote the leaching of metal ions such as calcium and magnesium in steel slag, thereby accelerating the carbonization reaction of calcium and magnesium ions with dissolved carbon dioxide and promoting the formation of nano carbonates on the surface of the porous framework.

[0050] This invention utilizes steel slag and red mud as adsorbent raw materials, which is low in cost and simple in preparation method, does not require strict equipment and process conditions, and is easy to promote and apply.

[0051] In addition, sodium humate is a green, environmentally friendly, and inexpensive organic macromolecular material, making it very suitable for the modification of heavy metal ion adsorbents. Attached Figure Description

[0052] Figure 1 This is a process flow diagram for preparing the heavy metal ion adsorbent of the present invention;

[0053] Figure 2 SEM image of the heavy metal adsorbent prepared in Example 1;

[0054] Figure 3 The image shows the SEM image of the heavy metal adsorbent prepared in Example 10. Detailed Implementation

[0055] Figure 1 This is a process flow diagram for preparing the heavy metal ion adsorbent according to the present invention. Figure 1 As shown, one example of a process for preparing a heavy metal ion adsorbent includes drying and ball milling steel slag and red mud to obtain a mixture, then adding water to the mixture and wet milling it using a ball mill to obtain slurry 1. Slurry 1 may contain modified porous aluminosilicate framework particles. CO2 gas is introduced into slurry 1 to carbonize it, obtaining slurry 2. Slurry 2 may contain porous aluminosilicate framework particles and nano-carbonate particles supported on the pore surface. Finally, the slurry is filtered and boiled to obtain the adsorbent.

[0056] The steel slag raw material described in the example below was taken from a steel plant in Shanxi Province. Its chemical composition is as follows: CaO content is 37.38%, SiO2 content is 15.58%, Fe2O3 content is 21.65%, MgO content is 6.84%, Al2O3 content is 2.63%, MnO content is 8.71%, P2O5 content is 2.40%, and K2O content is 1.43%.

[0057] The red mud raw material comes from a Bayer process alumina plant in Shanxi Province. Its main chemical composition is: Al2O3 content 25.6%, SiO2 content 18.54%, CaO content 20.10%, Fe2O3 content 4.39%, and Na2O content 8.29%.

[0058] Sodium humate comes from Guangxi Nongbao Bioengineering Company.

[0059] Example 1

[0060] S1: Dry 100 parts of steel slag and 30 parts of red mud separately, put them in a ball mill, grind for 30 minutes, and then sieve them through a 100-200 mesh sieve to obtain steel slag and red mud; mix the sieved steel slag and red mud at a weight ratio of 1:0.3 and homogenize to obtain a mixture;

[0061] S2: Add 200 parts of distilled water to the well mixed steel slag and red mud mixture in step S1, stir evenly, and wet grind thoroughly for 1 hour using a small ball mill to obtain slurry 1;

[0062] S3: CO2 is introduced into the slurry 1 obtained in step S2 at a flow rate of 1.6 L / min, and magnetic stirring is used to fully carbonize it to obtain slurry 2. The stirring rate is 500 rpm, the reaction time is 1.1 h, and the carbonization temperature is 55℃.

[0063] S4: After filtering the slurry 2 from step S3, a solid is obtained. The solid is washed three times until the pH is neutral to remove soluble alkali and other soluble components from the solid. After drying, a heavy metal ion adsorbent is obtained.

[0064] Figure 2 The image shows a SEM image of the heavy metal ion adsorbent prepared in Example 1. As can be seen from the SEM image, the heavy metal ion adsorbent of Example 1 forms a loose and porous silica-alumina framework, in which carbonate particles are attached to the surface of the framework.

[0065] Example 2

[0066] The rest is the same as in Preparation Example 1, except that the grinding time of steel slag and red mud in step S1 is 20 min.

[0067] Example 3

[0068] The rest is the same as in Preparation Example 1, except that the grinding time of steel slag and red mud in step S1 is 60 min.

[0069] Example 4

[0070] The rest is the same as in Preparation Example 1, except that the mass ratio of steel slag to red mud in step S1 is 1:1.

[0071] Example 5

[0072] The rest is the same as in Preparation Example 1, except that the mass ratio of steel slag to red mud in step S1 is 1:1.5.

[0073] Example 6

[0074] The rest is the same as in Preparation Example 1, except that the mass ratio of distilled water to steel slag and red mud mixture in step S2 is 1:3.

[0075] Example 7

[0076] The rest is the same as in Preparation Example 1, except that the ball milling time in step S2 is 2 hours.

[0077] Example 8

[0078] The rest is the same as in Preparation Example 1, except that the CO2 gas flow rate in step S3 is 1.2 L / min.

[0079] Example 9

[0080] The rest is the same as in Preparation Example 1, except that the reaction temperature in step S3 is 75°C.

[0081] Example 10

[0082] S1: Dry 100 parts of steel slag and 30 parts of red mud separately, put them in a ball mill, grind for 30 minutes, and then sieve them through a 100-200 mesh sieve to obtain steel slag and red mud; mix the sieved steel slag and red mud at a weight ratio of 1:0.3 and homogenize to obtain a mixture;

[0083] S2: Add 200 parts of distilled water to the well mixed steel slag and red mud mixture in step S1, stir evenly, and wet grind thoroughly for 1 hour using a small ball mill to obtain slurry 1;

[0084] S2-1: Add sodium humate solution to slurry 1. The amount of sodium humate added is 0.03% by weight relative to the total weight of dried steel slag and dried red mud. Mix evenly to obtain slurry 2-1.

[0085] S3: CO2 is introduced into the slurry 2-1 obtained in step S2-1 at a flow rate of 0.6 L / min, and magnetic stirring is used to fully carbonize it to obtain slurry 2. The stirring rate is 500 rpm, the reaction time is 0.5 h, and the carbonization temperature is 22℃.

[0086] S4: After filtering the slurry 2 from step S3, a solid is obtained. The solid is washed three times until the pH is neutral to remove soluble alkali and other soluble components from the solid. After drying, a heavy metal ion adsorbent is obtained.

[0087] Figure 3 This is a SEM image of the heavy metal adsorbent prepared in Example 10. The SEM image shows that the heavy metal adsorbent forms a loose silica-alumina framework with carbonate particles attached to the surface of the framework.

[0088] Example 11

[0089] The heavy metal ion adsorbent was prepared according to the method of Example 10, except that sodium humate solution was added to slurry 1, and the amount of sodium humate added was 0.09 by weight relative to the total weight of dried steel slag and dried red mud.

[0090] Example 12

[0091] S1: Dry 100 parts of steel slag and 30 parts of red mud separately, put them in a ball mill, grind for 30 minutes, and then sieve them through a 100-200 mesh sieve to obtain steel slag and red mud; mix the sieved steel slag and red mud at a weight ratio of 1:0.3 and homogenize to obtain a mixture;

[0092] S2: Add 200 parts of distilled water to the well mixed steel slag and red mud mixture in step S1, and add sodium humate at 0.03% by weight relative to the total weight of dry steel slag and dry red mud. Stir evenly and wet grind thoroughly for 1 hour using a small ball mill to obtain slurry 1.

[0093] S3: CO2 is introduced into the slurry 1 obtained in step S2 at a flow rate of 0.6 L / min, and magnetic stirring is used to fully carbonize it to obtain slurry 2. The stirring rate is 500 rpm, the reaction time is 0.5 h, and the carbonization temperature is 22℃.

[0094] S4: After filtering the slurry 2 from step S3, a solid is obtained. The solid is washed three times until the pH is neutral to remove soluble alkali and other soluble components from the solid. After drying, a heavy metal ion adsorbent is obtained.

[0095] Comparative Example 1

[0096] The heavy metal ion adsorbent was prepared according to the method in Example 1, except that blast furnace slag was used instead of red mud.

[0097] Comparative Example 2

[0098] The heavy metal ion adsorbent was prepared according to the method in Example 1, except that silica fume was used instead of red mud.

[0099] Test Example 1-12

[0100] 1. Carbonization reaction efficiency

[0101] Carbonization efficiency is reflected in the amount of carbon dioxide fixed per 100g of dried raw material during the carbonization process within a certain time period. Specifically, taking 100g of raw material (which includes dried steel slag and red mud; in the example with added sodium humate, the raw material also includes sodium humate) as the standard, the amount of CO2 that can be fixed is calculated as follows:

[0102]

[0103] Where: n CO2 The percentage efficiency of CO2 fixation (i.e., carbonization efficiency) for 100g of raw material is given. △M1 is the weight loss (mg) of the sample before the CO2 reaction, and △M2 is the weight loss (mg) of the sample after the CO2 reaction.

[0104] The carbonization reaction efficiency results of Examples 1-12 and Comparative Examples 1-3 are shown in Table 1 below:

[0105] Table 1

[0106] project <![CDATA[CO2 gas flow rate]]> reaction time carbonization temperature Carbonization efficiency % Example 1 1.6L / min 1.1h 55℃ 10.26 Example 2 1.6L / min 1.1h 55℃ 9.53 Example 3 1.6L / min 1.1h 55℃ 10.76 Example 4 1.6L / min 1.1h 55℃ 10.99 Example 5 1.6L / min 1.1h 55℃ 11.69 Example 6 1.6L / min 1.1h 55℃ 10.55 Example 7 1.6L / min 1.1h 55℃ 11.54 Example 8 1.2L / min 1.1h 55℃ 9.64 Example 9 1.6L / min 1.1h 75℃ 11.57 Example 10 0.6L / min 0.5h 22℃ 16.12 Example 11 0.6L / min 0.5h 20℃ 15.58 Example 12 1.6L / min 1.1h 22℃ 12.86 Comparative Example 1 1.6L / min 1.1h 55℃ 9.98 Comparative Example 2 1.6L / min 1.1h 55℃ 8.12

[0107] 2. Adsorption rate of heavy metal ions in water

[0108] Take 100 ml of wastewater with a lead concentration of 1 g / L, add 1 g of the adsorbent prepared in Example 1 above, stir on a magnetic stirrer at a shaking speed of 100 r / min for 300 min, filter, and determine the Pb in the solution using ICP-AES (Shimadzu Inductively Coupled Plasma Mass Spectrometer ICPMS-2030). 2+ The concentration was determined, and the recovery rate was calculated using the following formula:

[0109] R = (C0 - C) e ) / C0×100%

[0110] In the formula, C0 represents Pb. 2+ Initial mass concentration of the solution, g / L; C e For Pb at adsorption equilibrium 2+ The mass concentration of the solution, g / L; R represents the concentration of heavy metal ions adsorbent for Pb. 2+ The adsorption rate.

[0111] The adsorbents prepared in Examples 2-12 were subjected to the above tests in sequence, corresponding to Examples 2-12 respectively.

[0112] Replacement with Pb 2+ Wastewater containing Cd at the same concentration 2+ Wastewater, Cu 2+ Wastewater, Cr 6+ The wastewater was subjected to the same experimental tests as described in the above examples, and the results are shown in Table 2 below.

[0113] Table 2

[0114]

[0115] As can be seen from the experimental data in Table 2 above, the heavy metal ion adsorbents prepared in Examples 1-12 achieve superior carbonization efficiency compared to the methods in Comparative Examples 1-2. In particular, Examples 10-11 demonstrate that by adding sodium humate as a modifier after step S2, the carbonization efficiency can be improved while reducing the carbonization reaction conditions, including carbon dioxide flow rate, reaction temperature, and reaction time.

[0116] By comparing Comparative Examples 1-2 with Example 1, it can be seen that the adsorbent prepared by adding a specific proportion of red mud and steel slag as raw materials significantly improves the adsorption capacity for various heavy metal ions (including Pb) compared to adsorbents prepared from steel slag and other waste materials. 2+ Cd 2+ Cu 2+ Cr 6+ The adsorption rate of one or more of them.

[0117] By comparing Example 1 with Examples 10-11, it can be seen that adding sodium humate can further improve the adsorption capacity of the adsorbent for heavy metal wastewater.

[0118] Example 12 shows that adding sodium humate in step S2 can promote the adsorption rate of heavy metal ions, but the effect is worse than that in Example 10.

[0119] In summary, the method of this invention involves the alkali in red mud eroding steel slag and red mud, thereby forming loose and porous particles. Subsequently, the carbonized nano-calcium carbonate adheres to the surface of the framework, increasing the specific surface area. Furthermore, the synergistic effect of red mud and steel slag enhances the reactivity of the silica-alumina mixture, increasing the number of active sites on the adsorbent surface and improving the adsorption rate of heavy metal ions in water. The addition of sodium humate further improves the adsorption rate of heavy metal ions in water. This invention uses two industrial solid wastes, steel slag and red mud, as reaction raw materials, resulting in low cost and the preparation of porous adsorbent materials loaded with nano-carbonates at room temperature. These materials exhibit high adsorption efficiency, achieving high-value utilization of steel slag and red mud for wastewater treatment.

[0120] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for preparing a heavy metal ion adsorbent, comprising the following steps: S1: Grind and sieve the dried steel slag and dried red mud separately, then disperse and mix the sieved steel slag and red mud to obtain a mixture of steel slag and red mud, wherein the mass ratio of the dried steel slag to the dried red mud is 1:0.2-4.0; S2: Add water to the mixture of steel slag and red mud obtained in step S1, stir, and wet grind using a ball mill to obtain slurry 1 containing porous particles; S2-1: After step S2, sodium humate solution is added to slurry 1 and mixed evenly to obtain slurry 2-1, wherein the amount of sodium humate added is 0.03-0.10% by weight relative to the total weight of dried steel slag and dried red mud. S3: Under stirring conditions, CO2 gas is introduced into the slurry 2-1 obtained in step S2-1 to carbonize the modified porous framework particles in slurry 2-1, resulting in slurry 2, which contains a porous framework and nano-carbonate particles supported on the pore surface; and S4: After filtering the slurry 2 from step S3, a solid is obtained. The solid is washed until the pH is neutral and then dried to obtain the heavy metal ion adsorbent.

2. The preparation method according to claim 1, characterized in that, The grinding time for the dried steel slag and dried red mud in step S1 is 20-60 min, respectively.

3. The preparation method according to claim 1 or 2, characterized in that, The mass ratio of the steel slag and red mud mixture to water in step S2 is 1:2.0-6.

0.

4. The preparation method according to claim 3, characterized in that, The water is deionized water.

5. The preparation method according to claim 1 or 2, characterized in that, The wet grinding time of the ball mill in step S2 is 0.2-3.5 hours, and the number of washing cycles in step S4 is 1-3 times.

6. The preparation method according to claim 1, characterized in that, In step S3, the purity of the CO2 gas is 95% to 99%, the flow rate is 1.2-2 L / min, the carbonization temperature is 50-75℃, the reaction time is 1.1-2.5 h, and the stirring rate is 300-1800 rpm.

7. The preparation method according to claim 1, characterized in that, In step S3, the purity of the CO2 gas is 95% to 99%, the flow rate is 0.2-1.2 L / min, the carbonization temperature is 20-30℃, the reaction time is 0.5-1 h, and the stirring rate is 300-600 rpm.

8. A heavy metal ion adsorbent, characterized in that... The heavy metal ion adsorbent is prepared by the method described in any one of claims 1-7.

9. The application of the heavy metal ion adsorbent according to claim 8 in the removal of heavy metal ions from wastewater.

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