Slag geopolymer heavy metal adsorption material and preparation method thereof

Abstract

The invention relates to the technical field of engineering materials, and discloses a slag geopolymer heavy metal adsorption material and a preparation method thereof. A geopolymer is innovatively modified by introducing a magnetic-sensitive nano material, and the heavy metal adsorption performance of the geopolymer is remarkably improved through an in-situ hydrothermal conversion process. The high-calcium slag geopolymer heavy metal adsorption material disclosed by the invention shows remarkable heavy metal adsorption performance and can realize the purpose of rapid solid-liquid separation of the adsorption material under the action of an external magnetic field, so that an innovative solution is provided for efficient and convenient heavy metal pollution treatment; the problems that a conventional low-calcium geopolymer is low in heavy metal adsorption amount, large in residue amount and difficult to dehydrate are solved, the method has wide application prospects, a new method for treating waste with waste is provided for synergistically solving heavy metal waste liquid treatment and solid waste disposal, and important environment-friendly, social and economic benefits are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of engineering materials, in particular to a novel slag geopolymer heavy metal adsorption material and a preparation method thereof. Background Art

[0002] Conventional geopolymers (such as kaolin, fly ash, and low-calcium systems) are considered to be potential heavy metal wastewater treatment materials due to their three-dimensional network structure and solid waste utilization advantages, and a large number of studies have been carried out. However, the practical application of these conventional geopolymers faces severe challenges, the core of which lies in their insufficient adsorption capacity and subsequent treatment difficulties: fly ash raw materials usually have a low calcium content (low-calcium system), and mainly form sodium aluminum silicate gel (N-(A)-SH) under strong alkali excitation. The N-(A)-SH structure is relatively dense, the pores are not fully developed (especially mesopores and macropores), and the specific surface area is low, resulting in limited exposure of active adsorption sites and poor diffusion channels. This directly results in its poor adsorption of heavy metal ions (such as Cu 2+ , Pb 2+ 、Cd 2+ The adsorption capacity and adsorption rate of conventional geopolymer adsorbents (e.g., geopolymer adsorbents) are generally low, making them difficult to meet the requirements for efficient treatment. Furthermore, to maximize the limited specific surface area and adsorption performance, conventional geopolymer adsorbents typically need to be ground into a fine powder. While this improves adsorption efficiency to a certain extent, it also creates the thorny issue of large amounts of post-treatment residue and the extreme difficulty of dehydration, severely hindering the industrialization and promotion of geopolymer adsorbents.

[0003] To address the core shortcomings of low-calcium geopolymers such as fly ash, such as their low heavy metal adsorption capacity and difficulty in solid-liquid separation, slag (particularly high-calcium slag) is being selected as a geopolymer raw material. Through its unique chemical composition and reaction products, and through magnetic powder and hydrothermal modification, these issues can be systematically addressed, demonstrating significant advantages: Slag is rich in calcium (a high-calcium system) and primarily forms calcium-aluminum silicate gel (C-(A)-SH) under strong alkali excitation. Compared to the N-(A)-SH formed by fly ash, the C-(A)-SH structure is typically looser and has more developed pores (especially mesopores). It possesses stronger ion exchange capacity, a larger specific surface area, and a richer pore network, providing more active adsorption sites and better diffusion and mass transfer pathways for heavy metal ions, fundamentally improving adsorption capacity and rate. In addition, there will be more CaO in the slag under the high calcium system, which forms Ca(OH)2 under alkali excitation and reacts with CO2 in the air to generate more CaCO3. Due to its surface roughness, CaCO3 will lead to uneven charge distribution and more binding sites, and also provide anions with strong ionization performance (CO3 2- ), CO3 2- Ions have a significant effect on the adsorption process, because CO3 2-It has strong charge properties, which combines with metal cations to form more stable compounds, ultimately leading to higher adsorption efficiency. However, the C-(A)-S-H gel in ordinary high-calcium geopolymer does not grow well, and it is also difficult to efficiently exert its own metal adsorption treatment ability.

[0004] Therefore, how to fully utilize the characteristics of high-calcium slag, optimize the activation conditions and synthesis process, to catalyze and accelerate the growth of C-(A)-S-H gel (the higher the calcium content, the more gel is generated), other beneficial heavy metal adsorption substances, and maximize the synergistic adsorption effect of CaCO3 formed under alkali activation; at the same time, how to efficiently and uniformly introduce a magnetically sensitive phase to ensure that the magnetically modified slag geopolymer has excellent heavy metal adsorption performance, excellent magnetic responsiveness, and good structural stability, and ultimately realize its efficient adsorption-quick separation-safe disposal application in heavy metal wastewater treatment, has become the core challenge and main direction of current technical research and engineering application in this field. Overcoming these problems will provide a promising technical path for solid waste resource utilization and heavy metal pollution control. SUMMARY

[0005] Therefore, how to fully utilize the characteristics of high-calcium slag, optimize the activation conditions and synthesis process, to catalyze and accelerate the growth of C-(A)-S-H gel (the higher the calcium content, the more gel is generated), other beneficial heavy metal adsorption substances, and maximize the synergistic adsorption effect of CaCO3 formed under alkali activation; at the same time, how to efficiently and uniformly introduce a magnetically sensitive phase to ensure that the magnetically modified slag geopolymer has excellent heavy metal adsorption performance, excellent magnetic responsiveness, and good structural stability, and ultimately realize its efficient adsorption-quick separation-safe disposal application in heavy metal wastewater treatment, has become the core challenge and main direction of current technical research and engineering application in this field. Overcoming these problems will provide a promising technical path for solid waste resource utilization and heavy metal pollution control.

[0006] The present application promotes the adsorption performance of slag geopolymer for heavy metals and realizes the solid-liquid separation process of heavy metal adsorption material. The present application has the following advantages.

[0007] Further, the present application enhances the ion exchange capacity and specific surface area of the adsorbent material on both chemical and physical adsorption to realize the enhancement of heavy metal adsorption capacity, which is different from the traditional method that only focuses on the enhancement of single level adsorption capacity. In addition, the magnetic sensitive nano material is introduced to modify the geopolymer, and the in-situ hydrothermal conversion method of the present application can also make the magnetic sensitive nanoparticles and geopolymer silicate species form a more close chemical bonding. The design method of the material solves the problems that the magnetic powder particles are easy to fall off (magnetic property is weakened or even lost) and the magnetic powder particles are easy to block the surface hydroxyl material of the geopolymer (affecting the adsorption capacity), so that the material not only has excellent heavy metal adsorption capacity, but also has the stable solid-liquid separation characteristics under the action of the external magnetic field. This characteristic not only improves the adsorption efficiency, but also overcomes the problem that the traditional adsorbent material is difficult to separate after water treatment, so that the adsorbent material can quickly separate from the water body by applying an external magnetic field, and a more convenient and efficient solution is provided for heavy metal pollution treatment.

[0008] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0009] The first technical purpose of the present application is to provide a slag geopolymer heavy metal adsorbent material, which is composed of the following components according to weight fraction: 98-100 parts of slag, 0.8-1.2 parts of calcium stearate, 0.6-1 part of hydrogen peroxide powder, 3-9 parts of magnetic sensitive nano material, 64-109 parts of alkali activator, and the CaO content in the slag is higher than 35%.

[0010] Optionally, the water-solid ratio of the slag geopolymer heavy metal adsorbent material is 0.45-0.6, the silicon-aluminum molar ratio is 2.2-2.8, and the solidification is carried out under the condition of constant temperature of 80 DEG C.

[0011] Optionally, the alkali activator is composed of analytical pure sodium hydroxide powder, sodium silicate powder and water. The alkali activator is prepared by mixing 14-30 parts of sodium silicate with modulus of 2.88, 5-19 parts of sodium hydroxide and 45-60 parts of water in a mass ratio, and the modulus of the prepared alkali activator is 1.0-1.3.

[0012] Optionally, the magnetic sensitive nano material is nano-Fe3O4 powder, i.e. magnetic powder, and the average particle size is 20 nm. The hydrogen peroxide powder is analytical pure, which decomposes to generate oxygen (O2) and other gases in the reaction process to form a uniform bubble structure. The calcium stearate is analytical pure, which reduces the surface tension of the bubble and enhances the mechanical strength of the bubble film to inhibit the bubble rupture or combination, thereby maintaining the stability of the bubble system.

[0013] The second technical purpose of the present application is to provide a preparation method of the slag geopolymer heavy metal adsorbent material as described above, and the method specifically comprises the following steps:

[0014] S1: Slowly add the analytical pure sodium hydroxide powder into water, and magnetically stir until completely dissolved, then stand at room temperature. After heating the solution to 50 DEG C with a water bath and keeping constant temperature, then add sodium silicate powder in batches, while stirring until the sodium silicate is completely dissolved, to prepare the alkali activator solution.

[0015] S2: The alkali activator solution described in S1 is placed at room temperature, then slowly mixed with the slag to prepare a modified geopolymer slurry, and stirred at a speed of 400 r / min on a disperser for 1-2 minutes.

[0016] S3: After adding calcium stearate, magnetic nano material (magnetic powder) and hydrogen peroxide powder to the modified geopolymer slurry obtained in S2 in turn, switch to strong stirring at a speed of 1500 r / min for 3-4 minutes, to prepare a nano-magnetic powder modified slag geopolymer slurry.

[0017] S4: Slowly inject the nano-magnetic powder modified slag geopolymer slurry prepared in S3 into a polytetrafluoroethylene mold, and after curing at 80 DEG C in an incubator for 24 hours, demold, and maintain at room temperature for 28 days.

[0018] S5: After the maintenance in S4, the geopolymer sample is placed in a reaction kettle and 2 mol / L sodium hydroxide solution is added to create a strong alkaline and high-activity hydrothermal environment, to promote the nucleation and growth of the gel and zeolite crystals. The reaction temperature is 200 DEG C, and the reaction time is 48 h, and then washed and dried to obtain the slag geopolymer heavy metal adsorption material.

[0019] Compared with the prior art, the beneficial effects of the present application are:

[0020] 1) The present application adds nano-Fe3O4 to modify, and designs a magnetic modified geopolymer heavy metal adsorption material development scheme with alkali activator modulus (1.0-1.3), silicon aluminum ratio (2.2-2.8), water solid ratio (0.45-0.6), and nano-Fe3O4 magnetic powder (3%-9%) as variables. The slag, nano-Fe3O4, hydrogen peroxide and calcium stearate form a magnetic modified geopolymer heavy metal adsorption material under the action of alkali activator. After studying the copper ion solution and carrying out the heavy metal adsorption orthogonal test of the ground geopolymer particles, the data of the heavy metal adsorption of geopolymer with different chemical compositions are analyzed, and the optimal modification formula for removing copper ions is obtained. The geopolymer adsorption material with the optimal modification is subjected to hydrothermal conversion, and a geopolymer adsorption material with excellent heavy metal adsorption effect is successfully developed, and it can realize solid-liquid separation under the action of an external magnetic field.

[0021] 2) Hydrothermal conversion improves the growth of beneficial heavy metal adsorption substances in geopolymer and improves its own microporous and mesoporous pore structure, promotes the formation and growth of gel, and significantly improves the adsorption capacity of heavy metals. Hydrothermal conversion makes the surface of the magnetic powder bond with the geopolymer to form Fe-O-Si / Al bond, and the magnetic powder is changed from simple physical mixing to chemical bonding embedded in the geopolymer matrix, and the magnetic powder is wrapped in the geopolymer system to prevent falling off, effectively improve the solid-liquid separation capacity, and release the Si-OH / Al-OH adsorption sites physically shielded by the magnetic powder. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of the provided drawings.

[0023] Figure 1 The preparation experiment process diagram of the slag geopolymer heavy metal adsorption material of the present application.

[0024] Figure 2 The Fourier infrared spectrum of the geopolymer sample.

[0025] Figure 3 The XRD spectrum of the geopolymer sample.

[0026] Figure 4 The low-temperature liquid nitrogen adsorption graph of the geopolymer sample.

[0027] Figure 5 The pore size distribution graph of mesopore and macropore (2-150nm) of the geopolymer sample.

[0028] Figure 6 The micropore pore size distribution graph (0-2nm) of the geopolymer sample.

[0029] Figure 7 The field emission electron microscope graph of the geopolymer sample, a is the conventional geopolymer, b is the nano-magnetic powder modified geopolymer, c is the hydrothermal conversion and nano-magnetic powder modified geopolymer.

[0030] Figure 8 The field emission electron microscope graph of the geopolymer sample, a is the raw material slag, b is the conventional geopolymer, c is the nano-magnetic powder modified geopolymer, d is the hydrothermal conversion and nano-magnetic powder modified geopolymer.

[0031] Figure 9 The 24h copper ion adsorption amount graph of the geopolymer sample.

[0032] Figure 10Graph of the pseudo-first order kinetic model for the conventional polymer.

[0033] Figure 11 Graph of the pseudo-second order kinetic model for the conventional polymer.

[0034] Figure 12 Graph of the intra-particle diffusion model for the conventional polymer.

[0035] Figure 13 Graph of the pseudo-first order kinetic model for the nano-magnetic powder modified polymer.

[0036] Figure 14 Graph of the pseudo-second order kinetic model for the nano-magnetic powder modified polymer.

[0037] Figure 15 Graph of the intra-particle diffusion model for the nano-magnetic powder modified polymer.

[0038] Figure 16 Graph of the pseudo-first order kinetic model for the hydrothermal conversion and nano-magnetic powder modified polymer.

[0039] Figure 17 Graph of the pseudo-second order kinetic model for the hydrothermal conversion and nano-magnetic powder modified polymer.

[0040] Figure 18 Graph of the intra-particle diffusion model for the hydrothermal conversion and nano-magnetic powder modified polymer.

[0041] Figures 10-18 Q t Q is the adsorption amount at time t, e Q is the adsorption amount at adsorption equilibrium. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work are within the protection scope of the present application.

[0043] The present application discloses a new type of slag geopolymer heavy metal adsorption material and a preparation method thereof.

[0044] In order to better understand the present application, the present application will be further specifically described by the following specific embodiments, but it should not be understood as limiting the present application. Some non-essential improvements and adjustments made by those skilled in the art according to the above content of the present application are also regarded as falling within the protection scope of the present application.

[0045] To simplify the number of experiments, embodiments use orthogonal experiment to design four factors and four levels of a total of 16 groups of experiments as examples (A-1 ~ A-16), and comparative examples (A-0), comparative examples (A-17), comparative examples (B-1), comparative examples (B-2), and it is also pointed out that the slag used in the following tests has a CaO of 39.18%. The Si / Al ratio is the core parameter for regulating the structure (especially the pore) and performance of geopolymer, and its increase will promote the formation of pores, but excessive amount will hinder the formation of geopolymer network due to Al3 + Early leaching reduces viscosity, prolongs solidification, causes gas to escape (reduces pore) and increases pore merging, affecting the gel network. Si can fix free Al3 + Form Si-O-Al bonds, increase viscosity and help stabilize pores. Therefore, optimizing the Si / Al ratio effectively regulates the pore structure, volume and final performance. In the experiment, the Si / Al ratio range is set to 2.2-2.8; the modulus of alkali activator determines the alkalinity of the reaction system. When the modulus is too high, the alkalinity of the reaction system is too low, which will hinder the polycondensation reaction of geopolymer. Therefore, in order to improve the porosity and micro-pore volume of geopolymer matrix, the modulus range is set to 1.0-1.3 in the experiment; water adjusts the viscosity of the reaction system, and increasing the water / solid ratio will reduce the density and promote the formation of capillary pores and gel pores, but excessive amount will cause pore collapse. At the same time, excessive water / solid ratio may hinder the formation of gel and affect the polycondensation reaction. At low water / solid ratio, the pore distribution is more uniform, the mixture has high viscosity and fast coagulation. Therefore, the water / solid ratio is set to 0.45-0.6 in the experiment. Table 1 shows the experimental group settings:

[0046] Table 1 Experimental group settings

[0047]

[0048]

[0049] Due to the similar production process, the production process of part of the samples is listed below. It needs to be pointed out that the images in the drawings need to be obtained in relation to the data of the 20 groups of experiments in Table 1. Among them, the A-8 group of geopolymer has the highest adsorption capacity, and the A-8HC group of geopolymer is formed by hydrothermal conversion, and the A-0 group of geopolymer is set as a control group. The silicon-aluminum ratio, water-solid ratio, and alkali activator modulus of the A-0 group are consistent with those of the A-8 group, but no magnetic powder is added. The control group B-1 group of fly ash geopolymer only replaces the slag of the A-8 group with the same amount of fly ash, and the other addition amounts are consistent. The control group B-2 group of fly ash geopolymer adds corresponding amounts of fly ash, alkali activator to make the silicon-aluminum ratio, water-solid ratio, alkali activator modulus, and magnetic powder consistent with those of the A-8 group. The control group A-17 group of slag geopolymer selects high-calcium slag with 45% calcium oxide, and other conditions are consistent with those of the A-8 group. The above 20 groups of experiments control the addition of calcium stearate and hydrogen peroxide powder crystal to be 1% and 0.8% of the weight of the slag, so as to explore the influence of silicon-aluminum ratio, water-solid ratio, alkali activator modulus, and magnetic powder on the heavy metal adsorption performance of the material.

[0050] Comparative example A-0 group

[0051] The A-0 group of slag geopolymer heavy metal adsorption material is composed of the following components by weight fraction:

[0052] 100 parts of slag, 1 part of calcium stearate, 0.8 parts of analytical pure hydrogen peroxide powder, and 88.19 parts of alkali activator. The water-solid ratio is controlled to be 0.6 during material preparation, and the silicon-aluminum molar ratio is 2.4. The material is cured at a constant temperature of 80°C.

[0053] Sodium hydroxide is an analytical pure powder, and sodium silicate is an analytical pure powder with a modulus of 2.88. The alkali activator is mixed by mass ratio of 19.1 parts of sodium silicate with a modulus of 2.88, 9.09 parts of analytical pure sodium hydroxide powder, and 60 parts of water.

[0054] After the above materials are prepared, the production method specifically includes the following steps:

[0055] S1: Slowly add analytical pure sodium hydroxide powder to water, magnetically stir until completely dissolved, and then stand at room temperature. Heat the solution to 50°C with a water bath and keep it at a constant temperature, then add sodium silicate powder in batches while stirring until the sodium silicate is completely dissolved, to prepare an alkali activator solution.

[0056] S2: The alkali activator solution described in S1 is left to stand at room temperature, then slowly mixed with slag to form geopolymer slurry, and stirred at a speed of 400 r / min on a disperser for 1-2 minutes.

[0057] S3: After calcium stearate and hydrogen peroxide are added into the geopolymer slurry obtained in S2 in sequence according to the mass fraction, the speed is switched to 1500 r / min for strong stirring for 3-4 minutes to prepare a conventional slag geopolymer slurry.

[0058] S4: The conventional slag geopolymer slurry prepared in S3 is slowly injected into a polytetrafluoroethylene mold, demolded after curing at 80℃ in a thermostat for 24 hours, and cured at room temperature for 28 days.

[0059] Comparative Example A-17 Group

[0060] The slag geopolymer heavy metal adsorption material in Group A-17 is composed of the following components according to the weight fraction:

[0061] 100 parts of high-calcium slag (artificially added with analytical pure CaO to make the content reach 45% in the above slag), 1 part of calcium stearate, 0.8 part of analytical pure hydrogen peroxide powder, 5 parts of magnetic powder, and 88.19 parts of alkali activator. The water-solid ratio is controlled to be 0.6 during material preparation, and curing is carried out at a constant temperature of 80℃.

[0062] The sodium hydroxide is an analytical pure powder, and the sodium silicate is an analytical pure powder with a modulus of 2.88. The alkali activator is mixed by mass ratio of 19.1 parts of sodium silicate with a modulus of 2.88, 9.09 parts of analytical pure sodium hydroxide powder, and 60 parts of water.

[0063] After the above materials are prepared, the preparation method specifically includes the following steps:

[0064] S1: Analytical pure sodium hydroxide particles are slowly added to room temperature ultrapure water, magnetically stirred until completely dissolved, and then left to room temperature. The solution is heated to 50℃ using a water bath and kept at a constant temperature, and then sodium silicate powder is added in batches while stirring until the sodium silicate is completely dissolved to prepare an alkali activator solution.

[0065] S2: The alkali activator solution described in S1 is left to room temperature, and then fly ash is slowly added to prepare a geopolymer slurry, which is stirred at a speed of 400 r / min for 1-2 minutes on a disperser.

[0066] S3: Calcium stearate, hydrogen peroxide, and magnetic powder are added into the geopolymer slurry obtained in S2 in sequence according to the mass fraction, and then the speed is switched to 1500 r / min for strong stirring for 3-4 minutes to prepare a nano-magnetic powder modified fly ash geopolymer slurry.

[0067] S4: The nano-magnetic powder modified fly ash geopolymer slurry prepared in S3 is slowly injected into a polytetrafluoroethylene mold, demolded after curing at 80℃ in a thermostat for 24 hours, and cured at room temperature for 28 days.

[0068] Comparative Example B-1 Group

[0069] The fly ash geopolymer heavy metal adsorption material of the B-1 group is composed of the following components in terms of weight fraction:

[0070] The fly ash is 100 parts, the calcium stearate is 1 part, the analytical pure hydrogen peroxide powder is 0.8 part, the magnetic powder is 5 parts, and the alkali activator is 88.19 parts. The water-solid ratio is controlled to be 0.6 during the preparation of the material, and the solidification is carried out under the condition of constant temperature of 80 DEG C.

[0071] The sodium hydroxide is an analytical pure powder, and the sodium silicate is an analytical pure powder, and the modulus thereof is 2.88. The alkali activator is mixed by mass ratio of 19.1 parts of sodium silicate with a modulus of 2.88, 9.09 parts of analytical pure sodium hydroxide powder and 60 parts of water.

[0072] After the above materials are prepared, the preparation method specifically includes the following steps:

[0073] S1: analytical pure sodium hydroxide particles are slowly added to room temperature ultrapure water, and magnetic stirring is carried out until complete dissolution, and then the solution is kept at room temperature. The solution is heated to 50 DEG C by using a water bath and kept at constant temperature, and then sodium silicate powder is added in batches while stirring until the sodium silicate is completely dissolved, and the alkali activator solution is prepared.

[0074] S2: The alkali activator solution of S1 is kept at room temperature, and then the fly ash is slowly mixed to prepare a geopolymer slurry, and the slurry is stirred at a speed of 400 r / min on a disperser for 1-2 minutes.

[0075] S3: The calcium stearate, hydrogen peroxide and magnetic powder are sequentially added to the geopolymer slurry obtained in S2, and then the speed is switched to 1500 r / min for strong stirring for 3-4 minutes, and the nano-magnetic powder modified fly ash geopolymer slurry is prepared.

[0076] S4: The nano-magnetic powder modified fly ash geopolymer slurry prepared in S3 is slowly injected into a polytetrafluoroethylene mold, and after being cured in a constant temperature oven at 80 DEG C for 24 hours, it is demolded and cured at room temperature for 28 days.

[0077] Comparative example B-2 group

[0078] The fly ash geopolymer heavy metal adsorption material of the B-2 group is composed of the following components in terms of weight fraction:

[0079] The fly ash is 100 parts, the calcium stearate is 1 part, the analytical pure hydrogen peroxide powder is 0.8 part, the magnetic powder is 5 parts, and the alkali activator is 117.52 parts. The water-solid ratio is controlled to be 0.6 during the preparation of the material, and the solidification is carried out under the condition of constant temperature of 80 DEG C.

[0080] Sodium hydroxide is an analytical pure powder, sodium silicate is an analytical pure powder, and its modulus is 2.88. The alkali activator is mixed in a mass ratio of 38.96 parts of sodium silicate with a modulus of 2.88, 18.56 parts of analytical pure sodium hydroxide powder, and 60 parts of water.

[0081] After the above materials are prepared, the preparation method specifically includes the following steps:

[0082] S1: analytical pure sodium hydroxide particles are slowly added to room temperature ultrapure water, and magnetic stirring is performed until complete dissolution, and then the solution is left to room temperature. The solution is heated to 50°C in a water bath and kept at a constant temperature, and then sodium silicate powder is added in batches while stirring until the sodium silicate is completely dissolved, and an alkali activator solution is prepared.

[0083] S2: The alkali activator solution described in S1 is left to room temperature, and then fly ash is slowly added to prepare a geopolymer slurry, which is stirred at a speed of 400 r / min on a disperser for 1-2 minutes.

[0084] S3: After calcium stearate, hydrogen peroxide, and magnetic powder are sequentially added to the geopolymer slurry obtained in S2, the speed is switched to 1500 r / min for strong stirring for 3-4 minutes, and a nano-magnetic powder modified fly ash geopolymer slurry is prepared.

[0085] S4: The nano-magnetic powder modified fly ash geopolymer slurry prepared in S3 is slowly injected into a polytetrafluoroethylene mold, and after curing at 80°C in a constant temperature oven for 24 hours, it is demolded and cured at room temperature for 28 days.

[0086] Example A-8 group

[0087] The slag geopolymer heavy metal adsorption material of group A-8 is composed of the following ingredients by weight fraction:

[0088] 100 parts of slag, 1 part of calcium stearate, 0.8 parts of analytical pure hydrogen peroxide powder, 5 parts of magnetic powder, and 88.19 parts of alkali activator. The water-solid ratio is controlled to be 0.6 during material preparation, the silicon-aluminum molar ratio is 2.4, and curing is carried out at 80°C under constant temperature conditions.

[0089] Sodium hydroxide is an analytical pure powder, sodium silicate is an analytical pure powder, and its modulus is 2.88. The alkali activator is mixed in a mass ratio of 38.96 parts of sodium silicate with a modulus of 2.88, 18.56 parts of analytical pure sodium hydroxide powder, and 60 parts of water.

[0090] After the above materials are prepared, the preparation method specifically includes the following steps:

[0091] S1: The analytical pure sodium hydroxide particles are slowly added to the room temperature ultrapure water, and after magnetic stirring until completely dissolved, it is left to room temperature. The solution is heated to 50℃ with a water bath and kept constant, then sodium silicate powder is added in batches while stirring until the sodium silicate is completely dissolved, and an alkali activator solution is prepared.

[0092] S2: The alkali activator solution described in S1 is left to room temperature, then slowly mixed with slag to prepare a geopolymer slurry, and stirred on a disperser at a speed of 400r / min for 1-2 minutes.

[0093] S3: After adding calcium stearate, hydrogen peroxide and magnetic powder to the geopolymer slurry obtained in S2 according to the mass fraction, switch to 1500r / min speed and stir for 3-4 minutes to prepare a nano-magnetic powder modified slag geopolymer slurry.

[0094] S4: The nano-magnetic powder modified slag geopolymer slurry prepared in S3 is slowly injected into a polytetrafluoroethylene mold, cured at 80℃ in an incubator for 24 hours, then demolded and cured at room temperature for 28 days.

[0095] Example A-8HC hydrothermal conversion group

[0096] The A-8HC group slag geopolymer heavy metal adsorption material, according to the weight fraction, is composed of the following components:

[0097] Slag 100 parts, calcium stearate 1 part, analytical pure hydrogen peroxide powder 0.8 parts, magnetic powder 5 parts, alkali activator 88.19 parts. The water-solid ratio is controlled to be 0.6 during material preparation, the silicon-aluminum molar ratio is 2.4, and the curing is carried out at 80℃ constant temperature.

[0098] The sodium hydroxide is an analytical pure powder, and the sodium silicate is an analytical pure powder with a modulus of 2.88. The alkali activator is mixed by mass ratio of 19.1 parts of sodium silicate with a modulus of 2.88, 9.09 parts of analytical pure sodium hydroxide powder and 60 parts of water.

[0099] After the above materials are prepared, the preparation method specifically includes the following steps:

[0100] S1: The analytical pure sodium hydroxide particles are slowly added to the room temperature ultrapure water, and after magnetic stirring until completely dissolved, it is left to room temperature. The solution is heated to 50℃ with a water bath and kept constant, then sodium silicate powder is added in batches while stirring until the sodium silicate is completely dissolved, and an alkali activator solution is prepared.

[0101] S2: The alkali activator solution described in S1 is left to room temperature, then slowly mixed with slag to prepare a geopolymer slurry, and stirred on a disperser at a speed of 400r / min for 1-2 minutes.

[0102] S3: After adding calcium stearate, hydrogen peroxide and magnetic powder into the slag geopolymer slurry prepared in S2 in sequence, the speed is switched to 1500 r / min for strong stirring for 3-4 minutes to prepare a nano-magnetic powder modified slag geopolymer slurry.

[0103] S4: The nano-magnetic powder modified slag geopolymer slurry prepared in S3 is slowly injected into a polytetrafluoroethylene mold, demolded after curing at 80℃ in a thermostat for 24 hours, and cured at room temperature for 28 days.

[0104] S5: After curing in S4, the geopolymer sample is placed in a reaction kettle and 2 mol / L sodium hydroxide solution is added to create a strong alkaline and high-activity hydrothermal environment to promote the nucleation and growth of gel and zeolite crystals. The reaction temperature is 200℃ and the reaction time is 48h, followed by washing and drying to obtain the slag geopolymer heavy metal adsorption material.

[0105] Performance analysis

[0106] The samples are subjected to Fourier infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), field emission electron microscopy analysis (SEM), specific surface area and pore analysis, heavy metal adsorption capacity and adsorption mechanism analysis.

[0107] 1) Comparison of slag and fly ash raw materials and adsorption performance

[0108] As shown in Table 2, compared with fly ash, the high calcium environment of slag promotes the formation of C-(A)-S-H gel, provides more adsorption sites, and has strong ion exchange capacity. Na + (singly charged, weakly bound), Ca 2+ (divalent, strongly bound), Cu 2+ exchange Na + requires 1:2 (charge compensation), while exchanging Ca 2+ is highly efficient 1:1. Therefore, the low calcium system of fly ash generates N-(A)-S-H gel, which has weaker ion exchange capacity than the C-(A)-S-H gel produced by the high calcium system of slag. More importantly, C-(A)-S-H gel will slowly release Ca 2+ and OH - in aqueous solution, and Cu 2+ occupies the position of Ca 2+ through ion exchange, and Cu 2+ will occupy the position of OH -Combined to form Cu(OH)2 loaded on the surface of the adsorbent C-(A)-SH gel. This surface-induced precipitation effect is also the main reason why the adsorption capacity of C-(A)-SH gel is higher than that of simple ion exchange, and it is also another advantage over N-(A)-SH gel. The low calcium content of fly ash leads to a scarcity of ion exchange sites, which mainly relies on physical adsorption of the silicon-aluminum network and has low efficiency. In addition, there will be more CaO in the slag under the high calcium system, which forms Ca(OH)2 under alkali excitation and reacts with CO2 in the air to generate more CaCO3. Due to its surface roughness, CaCO3 will lead to uneven charge distribution and more binding sites, and also provide anions with strong ionization properties (CO3 2- ), CO3 2- Ions have a significant effect on the adsorption process, because CO3 2- With strong charge properties, it is similar to Cu 2+ Combined to form a more stable compound, ultimately leading to higher adsorption efficiency. Therefore, the present invention selects high-calcium slag to design heavy metal geopolymer adsorption materials, which is different from conventional low-calcium geopolymer adsorbents (such as fly ash-based geopolymers). As shown in Table 3, after 24 hours of adsorption in a 200mL solution of copper ion solution at an initial concentration of 150mg / L, the adsorption performance of the control group B-1 group fly ash geopolymer, the B-2 group fly ash geopolymer and the slag geopolymer designed by us is compared. The adsorption performance of fly ash for copper ions is much lower than that of slag. The A-17 group slag geopolymer with a higher content of calcium oxide has a better adsorption effect. The more calcium oxide content in the slag, the better, as proved by the comparative example A-17 group.

[0109] Table 2 Chemical composition of fly ash and slag obtained by X-ray fluorescence spectrometer test

[0110]

[0111] Table 3 Copper ion adsorption capacity of fly ash and slag geopolymers

[0112]

[0113]

[0114] 2) Fourier transform infrared spectroscopy (FTIR) test such as Figure 2 As shown:

[0115] The FTIR spectra of each sample are shown in Figure 2. Figure 2 All samples were detected at 3450 cm -1 A broad absorption peak can be observed at 1640 cm, which is the H-OH stretching vibration peak of the raw slag. -1 It is the bending vibration peak of the -OH group of free water molecules, 513 cm -1The peak at 1481 cm is the bending vibration peak of Si-O-Si bond. -1 The OCO vibration peak appears at , indicating the presence of carbonate impurities in the sample. The increase in the fluctuation and peak intensity of the synthesized geopolymer here is because a part of the CaO in the slag forms Ca(OH)2 under alkali excitation, and then reacts with CO2 in the air to form CaCO3.

[0116] 958cm -1 The peak at 958cm is the asymmetric stretching vibration peak of Si-OT (T=Si or Al), which is the absorption peak of the silicon and aluminum components in the raw materials. -1 The Si-OT peak nearby moves slightly to a lower frequency than that of the slag, indicating that the active substances in the slag react under the action of the alkali activator, and the alumina decomposes and releases Al 3+ During the geopolymer polymerization process, Al 3+ Replacement of Si 4+ Forming long silicon-aluminum chains with Si-O-Al bonds. The peak areas of the Si-OT vibration peaks of the three geopolymers, namely, conventional geopolymer, nanomagnetic powder modified geopolymer, hydrothermal conversion and nanomagnetic powder modified geopolymer, gradually increase, indicating that the content of Si-O-Si(Al) bonds increases, indicating that more C-(A)-SH gel products are generated, proving that the hydrothermal conversion process accelerates the degree of catalytic depolymerization and polymerization reactions, and catalytically accelerates the generation and growth of calcium aluminum silicate gel. Compared with N-(A)-SH gel in fly ash base, C-(A)-SH gel in slag-based polymer can provide more adsorption sites and has strong ion exchange capacity; Na + (monovalent, weakly bound), Ca 2+ (divalent, strong binding), Cu 2+ Exchange Na + 1:2 (charge compensation) is required, while exchanging Ca 2+ It is an efficient 1:1; therefore, the low calcium system of fly ash produces N-(A)-SH gel, whose ion exchange capacity is weaker than that of the C-(A)-SH gel produced by the high calcium system of slag. -1 The H-OH group stretching vibration peak at 1645 cm is related to the water in the gel structure of the hydration product in the sample. The enhancement of this peak also verifies the formation of more C-(A)-SH gel. -1 The enhancement of the bending vibration peak of -OH group at 3455cm indicates that the amount of physically adsorbed pore water / free water in the sample increases, combined with the structural water peak (3455cm -1 ) and the changes in the Si-OT vibration bands indicate that the generation of hydration products (especially C-(A)-SH gel) in the system increases, accompanied by the evolution of the pore structure, thereby accommodating more pore water.

[0117] The above results show that the hydrothermal conversion process can accelerate the generation and growth of C-(A)-SH gel by catalysis to enhance the chemical adsorption performance of the material. -1 The bending vibration peak of -OH group at the geopolymer also directly indicates that a large number of hydroxyl species such as [Al(OH)4] - 、[AlO(OH)3] 2- 、[SiO2(OH)2] 2- 、[Si(OH)4] - These substances can remove heavy metals by forming coordination bonds through the coordination of oxygen unbonded electrons with empty orbitals of metal ions.

[0118] After the hydrothermal reaction, 669cm -1 A new peak appears at , which is the Fe-O-Si / Al bond. The nanoparticles (Fe3O4) partially dissolve under strong alkali (2mol / L NaOH) and hydrothermal (200℃) conditions, releasing Fe 2+ / Fe 3+ ions. At the same time, the silicate components in the slag depolymerize in an alkaline environment to generate active silicate (H3SiO4 - or SiO4 4- The two react through a co-condensation reaction to form Fe-O-Si covalent bonds, which means the magnetic powder particles transition from being physically dispersed to being chemically bonded and embedded in the geopolymer matrix. This specialized material interaction design ensures that the magnetic powder is not simply physically encapsulated within the geopolymer system, preventing it from falling off and losing its magnetism. Instead, it forms a stronger bond and adhesion with the geopolymer system, maintaining its magnetic properties. The embedding of the magnetic powder within the geopolymer particles also releases Si-OH / Al-OH sites that were physically blocked by the magnetic powder, enhancing the geopolymer's chemical adsorption capacity.

[0119] 3) X-ray diffraction analysis such as Figure 3 shown

[0120] X-ray diffraction analysis was used to analyze the geopolymer samples. Curve 1 shows the slag spectrum, Curve 2 shows the spectrum of conventional slag geopolymer (Group A-0), Curve 3 shows the spectrum of slag geopolymer modified with nanomagnetic powder (Group A-8), and Curve 4 shows the spectrum of hydrothermally converted and nanomagnetic powder-modified geopolymer (Group A-8HC). Curves 2, 3, and 4 all show a CaCO3 peak, consistent with the FTIR results, indicating that this is a key component of the slag geopolymer's ability to adsorb divalent copper ions.

[0121] It can be seen from Curve 1 that the slag contains components such as calcium silicate, and the several peaks at around 30 degrees correspond to calcium silicate or other aluminosilicate minerals.

[0122] As can be seen from curve 2, after the depolymerization and repolymerization of the geopolymer, the original calcium silicate peaks significantly reduced in intensity, and some peaks disappeared; a broad and diffuse background peak appeared (e.g. in the 20°-30° region), indicating the formation of amorphous / semi-crystalline phases (e.g. C-(A)-S-H gel); the peaks of curve 2 are weaker than those of curve 1, especially in the high angle region, which can indicate that part of the crystalline phase was converted into amorphous material, which is consistent with the expected formation of geopolymer.

[0123] As can be seen from curve 3, the geopolymer of group A-8 added magnetic powder, and ferroferric oxide was detected in the spectrum, which indicates that the ferroferric oxide present in the geopolymer system has not been converted into other substances and can play its own function and endow the geopolymer with magnetic sensitivity characteristics.

[0124] As can be seen from curve 4, compared with the sample without hydrothermal conversion (curve 3), a large number of new zeolite crystal phases were formed, which proves that hydrothermal conversion can catalyze and accelerate the phase transformation and crystallization of geopolymer. The peak of ferroferric oxide still exists, which also verifies the bonding of Fe-O-Si / Al bond on the surface of the magnetic powder in FTIR, which has little effect on the magnetism of the magnetic powder and can ensure the magnetic sensitivity characteristics of the material. Other peaks such as the peak of sodium silicate are weakened, which indicates that more raw materials are consumed to form new phases, which is consistent with the Fourier transform infrared spectroscopy analysis of the geopolymer after hydrothermal treatment. In the figure, curve 4 has stronger and sharper new peaks, especially in the low angle region, which proves that the geopolymer has undergone phase transformation and formed more new crystalline phases.

[0125] X-ray diffraction analysis shows that hydrothermal conversion stimulates the adjustment of bond angles of zeolite secondary structures (Si / Al-O tetrahedron) in pre-existing geopolymer and rearranges them into ordered zeolite crystal phases. Part of the geopolymer is transformed into zeolite, and the micropore and mesopore content of the zeolite is significantly higher than that of the geopolymer, which brings hope for improving the heavy metal adsorption capacity of the material from the aspect of enhancing physical adsorption. The pore structure and heavy metal adsorption capacity of the material after hydrothermal conversion will be further discussed below.

[0126] 4) Low temperature liquid nitrogen adsorption-desorption isotherm analysis as shown in Figure 4

[0127] ​The conventional polymer (group A-0) has the lowest total adsorption amount and a flat curve, indicating that the pore structure is not well developed. The magnetic powder modified polymer (group A-8) has a very low adsorption amount at a low relative pressure (P / P0<0.1), indicating that there are few micropores. The adsorption amount slowly increases at a high relative pressure (P / P0>0.5), which may be mainly due to macropores, but the porosity is low. The hydrothermally converted and magnetic powder modified polymer (group A-8HC) has a significantly higher adsorption amount than the other two samples at a low relative pressure, indicating that it has a high content of micropores. As the relative pressure increases, the adsorption amount rapidly increases and approaches saturation, indicating the presence of a large number of mesopores / macropores. The initial adsorption amount and total adsorption amount of the hydrothermally converted and nano-magnetic powder modified polymer are significantly higher than those of the nano-magnetic powder modified polymer and the conventional polymer, which directly indicates that it has a larger specific surface area, and the measured specific surface area also verifies this point.

[0128] 5) Full pore size analysis as shown in Figure 5 、 Figure 6

[0129] In the micropore pore size distribution Figure 6 , the pore volume of the conventional polymer and the nano-magnetic powder modified polymer fluctuates slightly in the pore size range of 0.4-1.4 nm, and the overall pore size distribution is relatively wide without obvious sharp peaks, indicating that the pore structure is relatively dispersed and the micropore content is low. The pore volume of the hydrothermally converted and nano-magnetic powder modified polymer group is significantly higher than that of the other two groups at 0.8 nm (the peak value reaches 0.0016 cm 3 / g), indicating that the hydrothermal treatment significantly improves the pore development degree in this pore size range and significantly increases the specific surface area by promoting the formation of micropores. The measured micropore specific surface area of the hydrothermally converted and nano-magnetic powder modified polymer group is 26.7 m 2 ·g -1 , which is much higher than the 0.73 m 2 ·g -1 of the conventional polymer group and the 1.19 m 2 ·g -1 of the nano-magnetic powder modified polymer, which verifies this point (Table 4).

[0130] In the mesopore and macropore pore size distribution Figure 5 , the conventional polymer has a pore size distribution concentrated in the macropore range of 50-100 nm, and the pore volume is very low, indicating that the pore structure is loose or has poor connectivity. The nano-magnetic powder modified polymer group has a relatively wide distribution in the range of 10-20 nm, mainly in the mesopore range, but the pore volume is much lower than that of the hydrothermally converted and nano-magnetic powder modified polymer group. The hydrothermally converted and nano-magnetic powder modified polymer group has a sharp peak in the pore volume at 2-3 nm, and another peak at about 10 nm, indicating the presence of a large number of mesopores. The pore volume is the largest (up to 0.017 cm 3 ​ / g), far beyond the other two groups. The mesopore and macropore specific surface area of the hydrothermally converted and nano-magnetic modified geopolymer was measured to be 42.5m 2 ·g -1 far higher than the conventional geopolymer group of 0.78m 2 ·g -1 , nano-magnetic modified geopolymer 2.4m 2 ·g -1 .

[0131] The above results show that the hydrothermal treatment can promote the adjustment of the amorphous geopolymer silicon-oxygen tetrahedron bond angle and phase transition to ordered zeolite crystal phase (XRD proves), and this significant promotion of hydrothermal method of zeolite crystal formation and growth significantly promotes the pore generation and recombination in the geopolymer system, forming a large number of microporous mesoporous (total pore size analysis proves).

[0132] Table 4 Comparison of pore structure parameters

[0133]

[0134] 6) Field emission scanning electron microscopy (SEM) as shown in Figure 7 , Figure 8 .

[0135] As shown in Figure 7 , the pore of the conventional geopolymer ( Figure 7 a) is significantly less than that of the nano-magnetic modified geopolymer ( Figure 7 b and 7c). Figure 8 , Figure 8 a is the SEM image of the slag powder, in which the particles are irregular debris, the surface is rough, and there is no obvious agglomeration or cementation structure. Figure 8 b is the SEM image of the conventional geopolymer group, in which the geopolymer produces a gel material and a granular material after synthesis. The gel material is C-(A)-S-H gel, and the granular material is unreacted slag. Figure 8 c is the SEM image of the nano-magnetic modified geopolymer, in which the C-(A)-S-H gel appears as a "cotton" or "hedgehog-like" agglomeration and dense accumulation of fibrous structure. Figure 8 d is the SEM image of the hydrothermally converted and nano-magnetic modified geopolymer group, in which a large number of columnar crystal zeolites are produced. Figure 8In SEM scanning electron microscopy with energy dispersive spectroscopy analysis (EDS analysis) in d, Si (19.0%) and Al (4.84%) are typical components of silicate, which is consistent with the chemical basis of zeolite. Ca (27.21%) and Na (3.24%) are charge balance cations, which are common in zeolites (such as calcium zeolite, sodium zeolite). O (41.90%) has the highest proportion, which meets the structure requirements of silicon-oxygen tetrahedron and aluminum-oxygen tetrahedron. The atomic ratio of Si / Al is: 0.3167 x 10.0475 x 2 ≈ 3.330.0475 x 20.3167 x 1 ≈ 3.33, which belongs to the common zeolite range. The carbon element in the figure is the carbonate impurities in the slag.

[0136] 7) Adsorption capacity analysis

[0137] As Figure 9 , after 24 hours of adsorption in a 200 mL solution of copper ion solution with an initial concentration of 150 mg / L, the copper ion adsorption capacity of the geopolymer modified by introducing magnetic powder and hydrothermal conversion was 273.8 mg / g, while the copper ion adsorption capacity of the geopolymer modified by introducing magnetic powder without hydrothermal conversion was 200.4 mg / g, and the copper ion adsorption capacity of the conventional geopolymer without introducing magnetic powder and without hydrothermal conversion was 237.1 mg / g. Therefore, the geopolymer modified by introducing magnetic powder and hydrothermal conversion improved by 15.5% compared with the geopolymer without introducing magnetic powder and without hydrothermal conversion, and improved by 36.6% compared with the geopolymer modified by introducing magnetic powder without hydrothermal conversion. Even compared with the excellent copper ion adsorbent of the geopolymer reported in the current report (such as hexadecyl trimethyl ammonium bromide modified nanoporous geopolymer: 205 mg / g, NaOH activated slag based geopolymer microsphere adsorbent microsphere: 220.04 mg / g), the magnetic powder modified hydrothermal conversion geopolymer prepared by the present application still exhibits higher adsorption performance, with a maximum adsorption capacity of 273.8 mg / g.

[0138] The nanometer magnetic powder modified geopolymer slightly decreased in adsorption capacity compared with the conventional geopolymer, because the nanometer magnetic powder particles were attached to the surface of the geopolymer gel, blocking part of the exposed hydroxyl substances such as [Al(OH)4] - , [AlO(OH)3] 2- , [SiO2(OH)2] 2- , [Si(OH)4] - , etc., which can be used for chemical bonding. The total number of active sites is reduced. However, after hydrothermal treatment, the surface of the magnetic powder is bonded with the geopolymer to form Fe-O-Si / Al bonds, and the magnetic powder is wrapped in the geopolymer system, so it can no longer block the mass transfer channel (pore regeneration). In addition, the zeolite crystals and C-(A)-S-H gel growth induced by hydrothermal conversion push the magnetic powder away from the surface active area, reducing the coverage (site regeneration and exposure). The magnetic powder is embedded in the gap between the geopolymer particle skeleton, becoming a support structure rather than a surface covering (magnetic powder positioning optimization).

[0139] 8) Kinetic model adsorption mechanism analysis

[0140] In order to understand the mechanism of slag geopolymer adsorbing heavy metals, quasi-first-order kinetic model, quasi-second-order kinetic model, and particle internal diffusion model were constructed for analysis. The experimental data were linearly regressed and analyzed to obtain the quasi-first-order kinetic ( Figure 10 、 Figure 13 、 Figure 16 ), quasi-second-order kinetic ( Figure 11 、 Figure 14 、 Figure 17 ), and particle internal diffusion ( Figure 12 、 Figure 15 、 Figure 18 ) adsorption kinetic fitting lines of geopolymer adsorbing Cu(II).

[0141] In the fitting analysis of conventional geopolymer, the quasi-second-order model can more highly simulate the process of slag geopolymer adsorbing Cu(II), because the regression coefficients (R 2 = 0.997) are higher than those of the quasi-first-order model (R 2 = 0.954) and the particle internal diffusion model (R 2 = 0.963). In the fitting analysis of nano-magnetic powder modified geopolymer, the quasi-second-order model regression coefficient (R 2 = 0.995) is higher than that of the quasi-first-order model (R 2 = 0.974) and the particle internal diffusion model (R 2 = 0.975). Therefore, for conventional geopolymer and nano-magnetic powder modified geopolymer, the quasi-second-order kinetic model can more fully describe the adsorption behavior of Cu(II) on the surface of slag geopolymer, which indicates that the adsorption of conventional geopolymer and nano-magnetic powder modified geopolymer to heavy metals is mainly chemical adsorption, and the adsorption rate of Cu(II) on slag geopolymer is proportional to the square of unoccupied adsorption sites in slag geopolymer. The quasi-second-order kinetic model considers that the rate-controlling step in the adsorption process is the chemical reaction between heavy metal ions and adsorbent materials or chemical adsorption through electron gain and loss, electron sharing.

[0142] Focusing on the heavy metal adsorption test of hydrothermally converted geopolymer, the quasi-first-order model can more highly simulate the process of slag geopolymer adsorbing Cu(II), because the regression coefficients (R 2 = 0.984) are higher than those of the quasi-second-order model (R 2 = 0.958) and the particle internal diffusion model (R 2 = 0.963).= 0.982) of the model. The adsorption behavior of Cu(II) on slag geopolymer surface can be more fully described by the pseudo-first-order kinetic model. This indicates that the adsorption of Cu(II) on slag geopolymer is dominated by chemical adsorption to physical adsorption, which is mainly attributed to the significant increase of microporous and mesoporous and the specific surface area of geopolymer adsorption material induced by hydrothermal conversion method. The pseudo-first-order kinetic model considers that the process is dominated by physical process (such as diffusion or surface adsorption), and the concentration change of adsorbate in solution has a significant impact on the rate, which is usually applicable to the initial stage of adsorption or the case of excess surface sites of adsorption material. The above results of pore size and specific surface area also verify this point of view.

[0143] Explanation of the enhanced adsorption capacity after hydrothermal conversion (chemical adsorption level): Compared with conventional geopolymer materials (such as kaolin, fly ash), slag can stabilize the preparation of more C-(A)-S-H gel due to its high calcium characteristics, and maximize the synergistic adsorption effect of CaCO3 formed under alkali activation, laying a solid chemical adsorption foundation for slag geopolymer. Hydrothermal process accelerates the catalytic depolymerization and polymerization degree, which will directly catalyze and accelerate the production and growth of C-(A)-S-H gel (FTIR evidence). C-(A)-S-H gel has stronger ion exchange capacity than conventional N-(A)-S-H gel, because Na + (monovalent, weak binding), Ca 2+ (bivalent, strong binding), Cu 2+ can be exchanged for Na + requires 1:2 (charge compensation), while Ca 2+ is efficiently exchanged 1:1. Therefore, the low calcium system of fly ash generates N-(A)-S-H gel, which has weaker ion exchange capacity than the high calcium system of slag to produce C-(A)-S-H gel. More importantly, C-(A)-S-H will slowly release Ca 2+ and OH - in aqueous solution, Cu 2+ occupies the position of Ca 2+ , while Cu 2+ will combine with OH - to form Cu(OH)2 loaded on the surface of the adsorbent C-(A)-S-H gel. In addition, there are more CaO in the slag under the high calcium system, which forms Ca(OH)2 under alkali activation, and reacts with CO2 in the air to generate more CaCO3. CaCO3 will cause uneven charge distribution and more binding sites due to its surface roughness, and also provides anions (CO3 2- ) with strong ionization properties, CO3 2- ions have a significant impact on the adsorption process, because CO3 2- has strong charge properties, which can be combined with Cu 2+The combination forms a more stable compound, ultimately leading to higher adsorption efficiency. Therefore, the catalytic acceleration of C-(A)-S-H gel production and growth by the hydrothermal conversion process (FTIR evidence) is an important discovery and design to enhance the heavy metal adsorption capacity of the material from the chemical adsorption level. In addition, the hydrothermal conversion enables the magnetic powder particles to be embedded in the polymer matrix by chemical bonding instead of simple wrapping (compared to nano-magnetic powder modified polymer), which can release the Si-OH / Al-OH sites physically blocked by the magnetic powder and enhance the chemical adsorption capacity of the polymer.

[0144] Explanation of adsorption capacity enhancement mechanism after hydrothermal conversion (physical adsorption level): The hydrothermal conversion and nano-magnetic powder modified polymer (A-8HC group) have the richest polymer gel network, the most zeolite crystals generated, the most superior multi-pore structure (especially high micropore and mesopore content), and the highest specific surface area. The hydrothermal treatment catalyzes the rearrangement of the silicon-aluminum structure in the amorphous polymer gel, and the phase transition to ordered zeolite crystals (evidenced by the new phase zeolite detected by X-ray diffraction test); the formation and crystal growth process of the zeolite phase significantly promotes the generation and recombination of micropores and mesopores (evidenced by the full pore size test), and the synergistic increase of micropores and mesopores provides a good migration path for heavy metal mass transfer and diffusion, and the synergistic increase of micropores and mesopores can also significantly increase the specific surface area of the material, which enhances the physical adsorption capacity of the material.

[0145] In summary, the selection of raw material slag lays a good chemical adsorption foundation for the polymer, and the hydrothermal conversion further enhances the chemical and physical adsorption capacity of the material, and the synergy of hydrothermal conversion and magnetic powder enables the magnetic powder to be embedded in the polymer matrix by chemical bonding instead of simple physical mixing, preventing shedding and effectively improving the solid-liquid separation capacity. In this invention, the use of the hydrothermal conversion process has the following advantages:

[0146] ① Catalytic acceleration of C-(A)-S-H gel production and growth (FTIR evidence) is an important discovery and design to enhance the heavy metal adsorption capacity of the material from the chemical adsorption level. The ion exchange capacity of C-(A)-S-H gel produced in high calcium system (such as slag) is significantly higher than that of N-(A)-S-H gel produced in low calcium system (such as fly ash, kaolin); C-(A)-S-H gel can also slowly release Ca 2+ and OH - in aqueous solution, through ion exchange, Cu 2+ occupies the position of Ca 2+ , and Cu 2+ will react with OH -Combined to form Cu(OH)2 loaded on the surface of the adsorbent C-(A)-SH gel; In addition, there will be more CaO in the slag under the high calcium system, which forms Ca(OH)2 under alkali excitation and reacts with CO2 in the air to generate more CaCO3. Due to its surface roughness, CaCO3 will lead to uneven charge distribution and more binding sites, and also provide anions with strong ionization properties (CO3 2- ), CO3 2- Ions have a significant effect on the adsorption process, because CO3 2- With strong charge properties, it is similar to Cu 2+ The combination forms more stable compounds, ultimately leading to higher adsorption efficiency; therefore, the hydrothermal conversion process is used to catalyze the acceleration of the production and growth of C-(A)-SH gel, which is an important discovery and design to increase the adsorption capacity of the material from the chemical adsorption level.

[0147] ② Catalytically accelerating the formation and growth of a new zeolite phase (XRD evidence) is a key discovery and design for enhancing the material's heavy metal adsorption capacity through physical adsorption. Zeolite phase formation and crystal growth significantly promote the generation and reorganization of micropores and mesopores (as evidenced by full-pore size testing). This synergistic increase in micropores and mesopores provides a favorable migration path for heavy metal mass transfer and diffusion. This synergistic increase also significantly increases the material's specific surface area, enhancing its ability to remove heavy metals through physical adsorption.

[0148] ③ The surface of the magnetic powder is bonded to the geopolymer to form Fe-O-Si / Al bonds. The magnetic powder is transformed from simple physical mixing to chemical bonding and embedding in the geopolymer matrix. The magnetic powder is wrapped in the geopolymer system to prevent it from falling off, effectively improving the solid-liquid separation ability (as evidenced by X-ray diffraction test) and releasing the Si-OH / Al-OH adsorption sites physically blocked by the magnetic powder.

[0149] In summary, the new slag geopolymer heavy metal adsorption material proposed in the present invention has a higher adsorption capacity than the currently reported geopolymer heavy metal adsorbents. The increase in the calcium oxide content in the slag can improve the heavy metal adsorption capacity of the developed geopolymer. In addition, after hydrothermal conversion, it promotes the growth of C-(A)-SH gel in the geopolymer system and catalytically accelerates the appearance and growth of zeolites with rich and developed microporous and mesoporous structures and high specific surface areas. This synergistically improves the heavy metal adsorption capacity of the material from the chemical and physical adsorption levels, respectively. Due to its magnetic sensitivity, it can overcome the solid-liquid separation problem of large-scale application of the material, showing great potential for it in the field of heavy metal wastewater adsorption treatment.

[0150] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to persons of skill in the art, and that the appended claims are intended to cover all such modifications that do not depart from the true spirit and scope of the application. Therefore, the application is not limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A slag geopolymer heavy metal adsorption material, characterized in that: The invention is composed of the following components by weight: 98-100 parts of slag, 0.8-1.2 parts of calcium stearate, 3-9 parts of magnetic sensitive nanomaterials, 0.6-1 part of hydrogen peroxide powder crystals, and 64-109 parts of alkali activator. The CaO content in the slag is higher than 35%.

2. The slag geopolymer heavy metal adsorption material according to claim 1, characterized in that: The slag geopolymer heavy metal adsorption material has a water-to-solid ratio of 0.45-0.6 and a silicon-aluminum molar ratio of 2.2-2.8, and is solidified at a constant temperature of 80°C.

3. The slag geopolymer heavy metal adsorption material according to claim 1, characterized in that: The alkaline activator is composed of analytically pure sodium hydroxide powder, sodium silicate powder and water. The alkaline activator is prepared by mixing 14-30 parts of sodium silicate with a modulus of 2.88, 5-19 parts of sodium hydroxide and 45-60 parts of water. The modulus of the alkaline activator is 1.0-1.

3.

4. The slag geopolymer heavy metal adsorption material according to claim 1, characterized in that: The magnetically sensitive nanomaterial is nano-iron tetroxide powder, i.e., magnetic powder, with an average particle size of 20 nm. The hydrogen peroxide powder is of analytical grade and decomposes to produce gas during the reaction, forming a uniform bubble structure. The calcium stearate is of analytical grade and inhibits bubble rupture or merging by reducing bubble surface tension and enhancing the mechanical strength of the bubble membrane, thereby maintaining the stability of the bubble system.

5. A method for preparing the slag geopolymer heavy metal adsorption material according to claim 1, characterized in that: The method specifically comprises the following steps: S1: Slowly add analytical grade sodium hydroxide powder to water, stir magnetically until completely dissolved, and then let it cool to room temperature; heat the solution to 50°C and maintain constant temperature, then add sodium silicate powder in batches while stirring until the sodium silicate is dissolved to prepare an alkaline activator solution; S2: The alkaline activator solution prepared in S1 is allowed to stand until it reaches room temperature, and then the slag is slowly added and stirred to form a modified geopolymer slurry; S3: adding calcium stearate, magnetic sensitive nanomaterials, and hydrogen peroxide powder crystals to the modified geopolymer slurry obtained in S2 in sequence, and stirring to obtain nano-magnetic powder modified slag geopolymer slurry; S4: Slowly inject the nano-magnetic powder modified slag geopolymer slurry prepared in S3 into a polytetrafluoroethylene mold, solidify at a constant temperature, then demould, and cure at room temperature for 28 days; S5: After S4 curing, the geopolymer sample is placed in a reactor and a 2 mol / L sodium hydroxide solution is added, followed by washing and drying to obtain the slag geopolymer heavy metal adsorption material.

6. The method for preparing the slag geopolymer heavy metal adsorption material according to claim 5, characterized in that: The stirring speed in S2 is 400 r / min, and the stirring time is 1 to 2 minutes; the stirring speed in S3 is 1500 r / min, and the stirring time is 3 to 4 minutes.

7. The method for preparing the slag geopolymer heavy metal adsorption material according to claim 5, characterized in that: In S4, the constant temperature curing temperature is 80° C. and the curing time is 24 hours.

8. The method for preparing the slag geopolymer heavy metal adsorption material according to claim 5, characterized in that: In S5, the hydrothermal reaction temperature is 200° C. and the reaction time is 48 h.

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