Magnetic geopolymer as well as preparation method and application thereof

Abstract

The invention discloses a magnetic geopolymer as well as a preparation method and application thereof, and relates to the technical field of solid waste resource utilization and wastewater treatment. The preparation method comprises the following steps: drying nickel slag, crushing and grinding, adding calcium oxide to adjust alkalinity, and heating and melting to obtain a nickel slag melt; the nickel slag melt is subjected to water quenching, and magnetic slag micro powder is obtained through drying, crushing and screening; and mixing the magnetic slag micro powder with an alkaline activator, injecting the mixture into a mold, performing constant-temperature maintenance, demolding, and crushing to obtain the magnetic geopolymer. The magnetic geopolymer prepared by the invention has high adsorption capacity and rapid adsorption kinetics for multiple heavy metal ions in water, and has excellent magnetic separation performance.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization and wastewater treatment technology, specifically to a magnetic geopolymer and its preparation method and application. Background Technology

[0002] Nickel slag is a solid waste generated during the nickel smelting process. Approximately 6-16 tons of nickel slag are produced for every ton of metallic nickel produced. my country currently has over 40 million tons of nickel slag stockpiled, and this amount is increasing by 2 million tons annually. Nickel slag contains abundant valuable components such as iron, silicon, and magnesium (total iron content is as high as 35%-40%). However, long-term stockpiling not only occupies large amounts of land but also leads to the migration of heavy metal ions due to rainwater leaching, polluting the soil and groundwater, resulting in resource waste and environmental risks.

[0003] Geopolymers are inorganic polymer materials formed by activating aluminosilicate raw materials with an alkaline activator. They possess advantages such as a three-dimensional network structure, high specific surface area, and good chemical stability, and have broad application prospects in adsorption, catalysis, and building materials. Using industrial solid waste to prepare geopolymers can reduce material costs and achieve resource utilization of solid waste. Meanwhile, magnetic adsorption materials have attracted much attention in wastewater treatment due to their advantages of fast separation speed and simple operation. By introducing a magnetic phase into geopolymers, rapid magnetic separation of adsorption materials can be achieved, improving wastewater treatment efficiency.

[0004] Currently, some studies have used nickel slag to prepare geopolymers. Existing techniques often involve the later doping of magnetic particles to prepare magnetic geopolymers; however, the magnetic particles do not bond tightly to the geopolymer matrix and are prone to detachment, leading to a decline in adsorption and magnetic response performance. Furthermore, the naturally occurring magnetite phase in nickel slag is not fully utilized, resulting in high material preparation costs. Moreover, existing research primarily focuses on optimizing mechanical properties, with limited research on its application to heavy metal adsorption, and it suffers from problems such as low adsorption capacity, difficult separation, and poor magnetic controllability.

[0005] Therefore, developing a method for preparing magnetic geopolymers that utilizes the magnetic phase of molten nickel slag itself, is simple in process, and has excellent adsorption and magnetic separation properties is of great significance for the resource utilization of nickel slag and the treatment of heavy metal wastewater. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide a magnetic geopolymer, its preparation method, and its application. This method utilizes magnetite precipitated in situ during the melting process as a magnetic source, the high activity of the rapidly cooled glass phase as a geopolymerization reaction source, and combines a magnetic enhancer to regulate the magnetic response performance of the material. The magnetic geopolymer is prepared through alkali excitation. The resulting product exhibits high adsorption capacity and rapid adsorption kinetics for various heavy metal ions in water, and possesses excellent magnetic separation performance. Simultaneously, it solves the environmental problems associated with nickel slag storage.

[0007] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for preparing a magnetic geopolymer is provided, comprising the following steps:

[0008] (1) After drying the nickel slag, crush and grind it, then add calcium oxide to adjust the alkalinity to 0.5-0.7, then heat it to 1500-1550℃ in air or a weak oxidizing atmosphere to melt it and keep it warm to obtain nickel slag melt;

[0009] (2) The nickel slag melt obtained in step (1) is quenched in water, dried, crushed and screened to obtain magnetic slag powder;

[0010] Alternatively, the nickel slag melt obtained in step (1) is cooled to 1300-1350℃ at 4-6℃ / min, then quenched in water, and dried, crushed and sieved to obtain magnetic slag powder.

[0011] (3) The magnetic slag powder obtained in step (2) is mixed with an alkaline activator and injected into a mold of a predetermined shape. Air bubbles are removed and the mixture is cured at a constant temperature. After demolding, the mixture is crushed to obtain a magnetic geopolymer. The alkaline activator is composed of silica sol, sodium hydroxide and sodium aluminate.

[0012] The core of geopolymerization is the dehydration condensation process between aluminosilicates, with silicon and aluminum being the key components of the reaction system. This invention uses nickel slag as raw material, and through melt oxidation treatment, transforms the iron-magnesium olivine phase into magnetic iron components and highly active silicon. Subsequently, by adjusting the silicon-aluminum ratio and optimizing the alkali activator, a magnetic geopolymer adsorbent is prepared. This adsorbent not only exhibits excellent adsorption performance for heavy metal ion wastewater but also allows for efficient recovery using magnetic separation technology, combining the advantages of high adsorption efficiency and resource utilization.

[0013] Furthermore, in step (1), the heating rate is 5-10 ℃ / min; the holding time is 1-2 h.

[0014] Furthermore, in step (1), the powder is ground to 200 mesh.

[0015] Furthermore, in step (1), the alkalinity is adjusted to 0.6.

[0016] Furthermore, in step (3), the alkaline activator is composed of silica sol, sodium hydroxide and sodium aluminate, and reacts fully for 12-24 h by magnetic stirring.

[0017] Furthermore, in step (3), after the magnetic slag powder is mixed with the alkaline activator, the molar ratio of silicon, aluminum and sodium is 1-3:1:1.

[0018] Based on the elemental analysis of nickel slag, sodium aluminate and sodium hydroxide are mainly used to prepare the alkaline activation solution, and then silica sol is added to make the silicon, aluminum and sodium elements reach the corresponding ratio after mixing with magnetic slag powder.

[0019] Furthermore, in step (3), air bubbles are removed by slight vibration.

[0020] Furthermore, in step (3), the temperature is kept constant at 50-80℃ for 24-48 hours.

[0021] The present invention also provides a magnetic geopolymer prepared by the above-mentioned method.

[0022] This invention also provides the application of the above-mentioned magnetic geopolymer in the adsorption of heavy metal ions.

[0023] Furthermore, this application involves using magnetic geopolymers to adsorb heavy metal ions in water.

[0024] Furthermore, heavy metal ions include, but are not limited to: Ni 2+ Cu 2+ Cd 2+ Zn 2+ Pb 2+ Co 2+ wait.

[0025] Furthermore, the adsorption conditions were: room temperature, pH=3-7, and the amount of magnetic geopolymer added was 0.5-2.0 g / L.

[0026] The present invention also provides a heavy metal ion adsorbent comprising the above-mentioned magnetic geopolymer.

[0027] The present invention has the following beneficial effects:

[0028] 1. The main raw material of this invention is industrial waste nickel slag, which reduces pollution from solid waste stockpiling. Through a synergistic process of directional modification and geological polymerization, the high-value resource utilization of nickel slag is realized, effectively reducing the raw material cost of adsorbent preparation.

[0029] 2. Compared with the traditional method of externally doped magnetic powder, the present invention uses magnetite crystals precipitated in situ, which are not easy to fall off or dissolve during use, and the magnetic properties are stable and durable.

[0030] 3. The magnetic geopolymer adsorbent material prepared by this invention combines the high adsorption rate of geopolymers with the rapid separation characteristics of magnetic materials. This magnetic geopolymer adsorbent material achieves an adsorption rate of over 90% for some heavy metal ion solutions, and a magnetic separation recovery rate greater than 95%. After adsorption, it can be rapidly separated by a magnetic field, solving the problems of difficult separation and low efficiency of traditional adsorbent materials. Attached Figure Description

[0031] Figure 1 The XRD pattern of the nickel slag used in Example 1;

[0032] Figure 2 This is a sample image of the magnetic geopolymer prepared in Example 1. Detailed Implementation

[0033] The principles and features of this invention are described below. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0034] Example 1

[0035] A magnetic geopolymer, the preparation method of which includes the following steps:

[0036] (1) The nickel slag (XRD pattern as shown) Figure 1 (As shown) After drying, it is crushed and ground to 200 mesh. Then, calcium oxide is added to adjust the alkalinity to 0.6. Then, under air or a weak oxidizing atmosphere, it is heated to 1500℃ at a heating rate of 5℃ / min and held for 2 hours to obtain nickel slag melt.

[0037] (2) The nickel slag melt obtained in step (1) is quenched in water, dried, crushed and screened to obtain magnetic slag powder;

[0038] (3) Mix silica sol, sodium hydroxide and sodium aluminate and react under magnetic stirring for 24 h to obtain an alkaline activator; mix the magnetic slag powder obtained in step (2) with the alkaline activator. After mixing, the molar ratio of silicon, aluminum and sodium elements is 1:1:1. Then inject it into a mold of a predetermined shape, remove air bubbles and keep it at a constant temperature of 60°C for 48 h. After demolding, crush it to obtain a magnetic geopolymer.

[0039] Example 2

[0040] A magnetic geopolymer, the preparation method of which includes the following steps:

[0041] (1) After drying the nickel slag, crush it and grind it to 200 mesh. Then add calcium oxide to adjust the alkalinity to 0.6. Then heat it to 1500℃ in air or weak oxidizing atmosphere at a heating rate of 5℃ / min and keep it at the temperature for 2 hours to obtain nickel slag melt.

[0042] (2) The nickel slag melt obtained in step (1) is quenched in water, dried, crushed and screened to obtain magnetic slag powder;

[0043] (3) Mix silica sol, sodium hydroxide and sodium aluminate, and react under magnetic stirring for 24 h to obtain an alkaline activator; mix the magnetic slag powder obtained in step (2) with the alkaline activator, and after mixing, the molar ratio of silicon, aluminum and sodium elements is 1.5:1:1, then inject it into a mold of a predetermined shape, remove air bubbles and cure at 80℃ for 48 h, demold and crush to obtain a magnetic geopolymer (such as... Figure 2 (As shown).

[0044] Example 3

[0045] A magnetic geopolymer, the preparation method of which includes the following steps:

[0046] (1) After drying the nickel slag, crush it and grind it to 200 mesh. Then add calcium oxide to adjust the alkalinity to 0.6. Then heat it to 1500℃ in air or weak oxidizing atmosphere at a heating rate of 5℃ / min and keep it at the temperature for 2 hours to obtain nickel slag melt.

[0047] (2) The nickel slag melt obtained in step (1) is cooled to 1350°C at 5°C / min, then quenched in water, dried, crushed and sieved to obtain magnetic slag powder;

[0048] (3) Mix silica sol, sodium hydroxide and sodium aluminate and react under magnetic stirring for 24 h to obtain an alkaline activator; mix the magnetic slag powder obtained in step (2) with the alkaline activator. After mixing, the molar ratio of silicon, aluminum and sodium elements is 2:1:1. Then inject it into a mold of a predetermined shape, remove air bubbles and keep it at a constant temperature of 60°C for 48 h. After demolding, crush it to obtain a magnetic geopolymer.

[0049] Example 4

[0050] A magnetic geopolymer, the preparation method of which includes the following steps:

[0051] (1) After drying the nickel slag, crush it and grind it to 200 mesh. Then add calcium oxide to adjust the alkalinity to 0.6. Then heat it to 1500℃ in air or weak oxidizing atmosphere at a heating rate of 5℃ / min and keep it at the temperature for 1-2 h to obtain nickel slag melt.

[0052] (2) The nickel slag melt obtained in step (1) is cooled to 1350°C at 5°C / min, then quenched in water, dried, crushed and sieved to obtain magnetic slag powder;

[0053] (3) Mix silica sol, sodium hydroxide and sodium aluminate and react under magnetic stirring for 12 h to obtain an alkaline activator; mix the magnetic slag powder obtained in step (2) with the alkaline activator. After mixing, the molar ratio of silicon, aluminum and sodium elements is 2.5:1:1. Then inject it into a mold of a predetermined shape, remove air bubbles and keep it at a constant temperature of 80°C for 48 h. After demolding, crush it to obtain a magnetic geopolymer.

[0054] Example 5

[0055] A magnetic geopolymer, the preparation method of which includes the following steps:

[0056] (1) After drying the nickel slag, crush it and grind it to 200 mesh. Then add calcium oxide to adjust the alkalinity to 0.6. Then heat it to 1500℃ in air or weak oxidizing atmosphere at a heating rate of 5℃ / min and keep it at the temperature for 2 hours to obtain nickel slag melt.

[0057] (2) The nickel slag melt obtained in step (1) is cooled to 1300℃ at 5℃ / min, then quenched in water, dried, crushed and sieved to obtain magnetic slag powder;

[0058] (3) Mix silica sol, sodium hydroxide and sodium aluminate and react under magnetic stirring for 18 h to obtain an alkaline activator; mix the magnetic slag powder obtained in step (2) with the alkaline activator at a silicon-to-aluminum ratio of 3, inject into a mold of a predetermined shape, remove air bubbles and keep it at a constant temperature of 80°C for 24 h, demold and crush to obtain a magnetic geopolymer.

[0059] Example 6

[0060] A magnetic geopolymer, the preparation method of which includes the following steps:

[0061] (1) After drying the nickel slag, crush it and grind it to 200 mesh. Then add calcium oxide to adjust the alkalinity to 0.6. Then heat it to 1500℃ in air or weak oxidizing atmosphere at a heating rate of 10℃ / min and keep it at that temperature for 2 hours to obtain nickel slag melt.

[0062] (2) The nickel slag melt obtained in step (1) is cooled to 1350°C at 5°C / min, then quenched in water, dried, crushed and sieved to obtain magnetic slag powder;

[0063] (3) Mix silica sol, sodium hydroxide and sodium aluminate and react under magnetic stirring for 18 h to obtain an alkaline activator; mix the magnetic slag powder obtained in step (2) with the alkaline activator. After mixing, the molar ratio of silicon, aluminum and sodium elements is 2:1:1. Then inject it into a mold of a predetermined shape, remove air bubbles and keep it at a constant temperature of 80°C for 24 h. After demolding, crush it to obtain a magnetic geopolymer.

[0064] Experimental Example 1

[0065] (1) Prepare simulated wastewater containing heavy metal ions at different concentrations, add the magnetic geopolymer prepared in Examples 1-6, and use a syringe with a filter head of 0.45 μm to draw 5 mL of reaction solution at time points of 5 min, 15 min, 30 min, 60 min, 2 h, 4 h, 8 h and 12 h respectively. Collect the filtrate in a centrifuge tube, detect the concentration of heavy metal ions by inductively coupled plasma spectroscopy (ICP), and calculate the adsorption rate. The results are shown in Table 1.

[0066] Table 1. Results of Heavy Metal Ion Adsorption Rate

[0067]

[0068] The results show that the magnetic geopolymer adsorbent material prepared in this invention has an adsorption rate of over 90% for heavy metal ion solutions.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a magnetic geopolymer, characterized in that, Includes the following steps: (1) After drying the nickel slag, crush and grind it, then add calcium oxide to adjust the alkalinity to 0.5-0.7, then heat it to 1500-1550℃ in air or a weak oxidizing atmosphere to melt it and keep it warm to obtain nickel slag melt; (2) The nickel slag melt obtained in step (1) is quenched in water, dried, crushed and screened to obtain magnetic slag powder; Alternatively, the nickel slag melt obtained in step (1) is cooled to 1300-1350℃ at 4-6℃ / min, then quenched in water, and dried, crushed and sieved to obtain magnetic slag powder. (3) The magnetic slag powder obtained in step (2) is mixed with an alkaline activator and injected into a mold of a predetermined shape. Air bubbles are removed and the mixture is cured at a constant temperature. After demolding, the mixture is crushed to obtain a magnetic geopolymer. The alkaline activator is composed of silica sol, sodium hydroxide and sodium aluminate.

2. The method for preparing the magnetic geopolymer as described in claim 1, characterized in that, In step (1), the heating rate is 5-10 ℃ / min; the holding time is 1-2 h.

3. The method for preparing the magnetic geopolymer as described in claim 1, characterized in that, In step (3), after the magnetic slag powder is mixed with the alkaline activator, the molar ratio of silicon, aluminum and sodium is 1-3:1:

1.

4. The method for preparing the magnetic geopolymer as described in claim 1, characterized in that, In step (3), the temperature is kept constant at 50-80℃ for 24-48 hours.

5. The magnetic geopolymer prepared by the method of any one of claims 1-4.

6. The application of the magnetic geopolymer according to claim 5 in the adsorption of heavy metal ions.

7. The application as described in claim 6, characterized in that, The magnetic geopolymer is used to adsorb heavy metal ions in water.

8. The application as described in claim 7, characterized in that, The adsorption conditions are: room temperature, pH=3-7, and the amount of magnetic geopolymer added is 0.5-2.0 g / L.

9. A heavy metal ion adsorbent, characterized in that, Includes the magnetic geopolymer described in claim 5.

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