Preparation method and application of fly ash-based composite material capable of selectively adsorbing sulfate radicals

Abstract

The invention discloses a preparation method and application of a fly ash-based composite material capable of selectively adsorbing sulfate radicals, and belongs to the technical field of solid waste resource utilization and sewage treatment.The method comprises the following steps that 1, dried fly ash is ground and sieved to obtain a 100-mesh powder material; immersing the powder material into dilute sodium hydroxide for modification, and then drying to obtain a modified fly ash material; (2) immersing the alkali modified fly ash material into a YCl3 solution, carrying out metal salt activation treatment, and then drying at 105 DEG C to obtain an activated fly ash material; the activated fly ash material is put into a muffle furnace to be fully roasted and activated at the temperature of 600-900 DEG C, and the fly ash-based composite material is obtained after cooling and can efficiently adsorb sulfate ions in wastewater. The preparation method is simple, the adsorption capacity is high, the emission concentration reaches the class III standard of GB3838-2002 surface water environmental quality standard, namely, the sulfate radical content is lower than 250 mg / L, and the preparation cost is low.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste resource utilization and sewage treatment, and particularly relates to a fly ash-based composite material capable of selectively adsorbing sulfate and a preparation method thereof. Background Art

[0002] Sulfate ions are widely present in surface water, groundwater, and industrial wastewater, such as acid mine drainage and pharmaceutical and dyeing wastewater. The main source of sulfate in natural water bodies is the chemical weathering and oxidation of sulfur-containing minerals. Although sulfate ions are generally considered non-toxic, their potential harm to organisms and the environment cannot be ignored. High concentrations of sulfate ions in water can lead to an imbalance in the natural sulfur cycle in ecosystems, and long-term ingestion can be harmful to human health. Therefore, it is necessary to remove sulfate ions from wastewater before it is discharged into the surrounding environment.

[0003] At present, calcium oxide precipitation is the most widely used method for removing sulfate in factories. However, calcium oxide will react with sulfate to form fluorgypsum (the main components are calcium fluoride and calcium sulfate), which makes it difficult to effectively separate the two products, and the product value is not high. Therefore, how to quickly and effectively separate fluoride ions and sulfate ions is a technical problem that technicians in this field urgently need to solve. It is worth noting that compared with the precipitation method, the adsorption method has received widespread attention due to its advantages such as being able to quickly and effectively remove sulfate ions and having no by-products. Although scientists have extensively studied granular activated carbon (GAC) and anion exchange resins to adsorb and remove sulfate from industrial wastewater, the selection of these adsorption materials is poor and difficult to apply to the treatment of wastewater with high fluoride and high sulfate. Therefore, it is imperative to develop a material that can quickly and effectively selectively adsorb sulfate ions.

[0004] Among the many adsorption materials, fly ash, a byproduct of coal-fired power plants, is produced in significant quantities. While its composition varies widely across regions, its primary components are SiO₂ and Al₂O₃, which exhibit strong alkalinity, flocculation, and adsorption properties. Furthermore, its abundance and low price make it a valuable and affordable option for sulfate wastewater treatment. However, its inherent adsorption capacity is insufficient, largely failing to meet treatment requirements. To further enhance its adsorption capacity, fly ash can be modified.

[0005] Fly ash modification methods primarily include physical and chemical approaches. Physical modification involves adjusting the fly ash's physical structure by altering its particle size distribution, surface area, and pore structure through grinding and sieving. Chemical modification, currently the mainstream modification method, primarily involves altering the physical and chemical properties of fly ash through activation with specific metal salts and high-temperature calcination. This study successfully synthesized a series of fly ash-based adsorbents by introducing specific metal active components and combining them with alkali modification and calcination. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention proposes a fly ash-based composite material for selectively adsorbing sulfate and a preparation method thereof, which has good environmental, economic and social benefits and broad application prospects.

[0007] To achieve the above objectives, the present invention provides the following technical solutions:

[0008] A fly ash-based composite material for selectively adsorbing sulfate and a preparation method thereof, comprising the following steps:

[0009] (1) Grinding the dry fly ash into particles and sieving to obtain fly ash powder material;

[0010] (2) mixing the fly ash powder material with dilute sodium hydroxide at a certain solid-liquid ratio, performing activation treatment, and then drying to obtain an alkali-modified fly ash material;

[0011] (3) mixing the activated fly ash material with a YCl3 solution at a certain solid-liquid ratio, performing a metal salt impregnation activation treatment, and then drying to obtain an activated fly ash material;

[0012] (4) The activated fly ash material is fully calcined and cooled to obtain a composite adsorption material.

[0013] As a further illustration of the present invention, in step (4), the roasting parameters are set as follows: roasting temperature 600-900°C, heating rate 10°C / min, roasting time 1-2h, and holding time 0.5-1.5h.

[0014] As a further illustration of the present invention, in step (2), the certain solid-liquid ratio is 0.1 to 0.5 g / mL, and the duration of the hydrochloric acid immersion modification treatment is 2 to 4 hours.

[0015] As a further illustration of the present invention, in step (3), the certain solid-liquid ratio is 0.2 to 0.5 g / mL, and the duration of the metal salt impregnation activation treatment is 2 to 5 hours.

[0016] As a further illustration of the present invention, in steps (2) and (3), the drying temperature is 105°C.

[0017] As a further illustration of the present invention, in step 1, the mesh number of the sieve is 100 mesh.

[0018] The present invention also provides a fly ash-based composite material for selectively adsorbing sulfate, which is prepared by the above-mentioned preparation method.

[0019] The present invention further describes that the raw materials of the fly ash-based composite material for selective adsorption of sulfate ions adopt the following specifications: the red mud is fly ash with an average silica content of 30-40%; the concentration of the dilute hydrochloric acid is 0.1 mol / L; and the concentration of the YCl3 solution is 0.5 mol / L.

[0020] The application of the fly ash-based composite material for selectively adsorbing sulfate in the treatment of sulfate-containing wastewater has a good adsorption effect. The adsorption material is relatively stable and can be repeatedly used after regeneration without causing secondary pollution.

[0021] In this invention, solid waste fly ash is used as the substrate. The fly ash contains an average silica content of approximately 30-40%, along with significant amounts of metal oxides such as aluminum oxide and calcium oxide. These metal oxides, upon activation, can generate active hydroxyl groups. Dilute sodium hydroxide is used as a modifier, reacting with substances in the raw fly ash to form a zeolite-like molecular sieve, improving its physical properties and forming a porous adsorbent. The metal salt YCl3 is used as an activator, combining with the metal oxides in the fly ash and, after high-temperature calcination, generating an yttrium-silicon complex containing active hydroxyl groups (Y-OH). Comparative experimental data demonstrates that this adsorbent exhibits excellent treatment effects on acidic, sulfate-containing wastewater.

[0022] Advantages of the present invention:

[0023] 1. The preparation method proposed in the present invention has a simple process, does not require complex technical equipment or high-pressure equipment, has low cost, and the prepared material has good adsorption performance, which is suitable for industrial promotion and large-scale production.

[0024] 2. The material prepared by the present invention has high stability, long service life and good regeneration effect.

[0025] 3. The material prepared by this invention is suitable for treating acidic, sulfate-containing industrial wastewater, achieving excellent results. The effluent meets the Class III standard of "GB3838-2002 Surface Water Environmental Quality Standard," meaning a sulfate concentration of less than 250 mg / L. (When treating industrial wastewater containing large amounts of sulfate and fluoride ions, the material of this invention preferentially adsorbs sulfate ions.) DETAILED DESCRIPTION

[0026] The present invention is further described below with reference to specific embodiments.

[0027] The raw materials used in the following examples are: fly ash from a desulfurization power plant in Guangxi, with a silicon dioxide content of 34.5%, a calcium oxide content of 26%, an aluminum oxide content of 17.3%, and an iron oxide content of 6%; dilute sodium hydroxide and yttrium chloride are both analytically pure chemical reagents.

[0028] Example 1:

[0029] A method for preparing a fly ash-based composite material for selectively adsorbing sulfate, comprising the following steps:

[0030] (1) Grinding the dried fly ash into fine particles and passing through a 100-mesh sieve to obtain fly ash powder material;

[0031] (2) mixing the fly ash powder material with dilute sodium hydroxide (0.1 mol / L) at a solid-liquid ratio of 0.5 g / mL, performing an impregnation modification treatment for 3 h, and then drying in an oven at 105° C. to obtain an alkali-modified fly ash material;

[0032] (3) The alkali-modified fly ash material was mixed with YCl3 solution (0.5 mol / L) at a solid-liquid ratio of 0.8 g / mL, and an impregnation activation treatment was performed for 3 h, and then dried in an oven at 105°C to obtain an activated fly ash material;

[0033] (4) The activated fly ash material was placed in a muffle furnace for full calcination (calcination temperature 850°C, heating rate 10°C / min, calcination time 1.5h, holding time 0.5h), and then taken out and cooled to room temperature to obtain a composite adsorption material.

[0034] Example 2:

[0035] A method for preparing a fly ash-based composite material for selectively adsorbing sulfate, comprising the following steps:

[0036] (1) Grinding the dry fly ash into fine particles and passing through a 100-mesh sieve to obtain the initial fly ash raw material;

[0037] (2) mixing the initial fly ash raw material with dilute sodium hydroxide (0.1 mol / L) at a solid-liquid ratio of 0.5 g / mL, performing an impregnation modification treatment for 2 h, and then drying in an oven at 105° C. to obtain a modified fly ash material;

[0038] (3) The modified fly ash material was mixed with YCl3 solution (0.5 mol / L) at a solid-liquid ratio of 0.5 g / mL, and an impregnation activation treatment was performed for 2.5 h, and then dried in an oven at 105°C to obtain an activated fly ash material;

[0039] (4) The activated fly ash material was placed in a muffle furnace for full calcination (calcination temperature 800°C, heating rate 10°C / min, calcination time 1.3h, holding time 0.5h), and then taken out and cooled to room temperature to obtain a composite adsorption material.

[0040] Example 3:

[0041] A method for preparing a fly ash-based composite material for selectively adsorbing sulfate, comprising the following steps:

[0042] (1) Grinding the dried fly ash into fine particles and passing through a 100-mesh sieve to obtain the initial fly ash raw material;

[0043] (2) mixing the initial fly ash raw material with dilute sodium hydroxide (0.1 mol / L) at a solid-liquid ratio of 0.5 g / mL, performing an impregnation modification treatment for 2 h, and then drying in an oven at 105° C. to obtain a modified fly ash material;

[0044] (3) The modified fly ash material was mixed with YCl3 solution (0.5 mol / L) at a solid-liquid ratio of 0.2 g / mL, and an impregnation activation treatment was performed for 3 h, and then dried in an oven at 105°C to obtain an activated fly ash material;

[0045] (4) The activated fly ash material was placed in a muffle furnace for full calcination (calcination temperature 700°C, heating rate 10°C / min, calcination time 1h, holding time 0.5h), and then taken out and cooled to room temperature to obtain a composite adsorption material.

[0046] Those skilled in the art will appreciate that the equipment or devices used in the above different embodiments are only used to illustrate the embodiments and are not intended to limit the present invention. Under the condition of ensuring compliance with the operating steps, any other available equipment or devices can be used in the preparation method according to the present invention.

[0047] Comparative Example 1

[0048] A method for preparing an adsorption material, which differs from Example 1 in that only YCl3 metal salt is used for modification without using sodium hydroxide for activation.

[0049] Comparative Example 2

[0050] A method for preparing an adsorption material, which differs from Example 1 in that only sodium hydroxide is used to activate fly ash, and YCl3 metal salt is not used for activation modification.

[0051] Implementation effect analysis:

[0052] The materials prepared in Examples 1-3 and Comparative Examples 1-2 were respectively used to treat aluminum fluoride industrial wastewater.

[0053] The treatment target was aluminum fluoride industrial wastewater containing a sulfate ion concentration of 2010 mg / L and a fluoride ion concentration of 2268 mg / L, with an initial pH of 3.1. Adsorption was performed using a filtration device using the adsorbent materials obtained in Examples 1-3 and Comparative Examples 1-2. The maximum adsorption capacity of fluoride ions by the composite adsorbent was then determined using the Langmuir model. The fluoride ion concentration in the wastewater was determined in accordance with the standard GB 7484-87, "Water Quality—Determination of Fluoride—Ion-Selective Electrode Method," and the sulfate ion concentration in the wastewater was determined in accordance with the standard HJ / T 342-2007, "Water Quality—Determination of Sulfate—Barium Chromate Spectrophotometric Method." The results are shown in Table 1.

[0054] Table 1 Comparison of the effects of treating aluminum fluoride industrial wastewater in Examples 1-3 and Comparative Examples 1-2

[0055]

[0056] As shown in Table 1, the material of the present invention can preferentially adsorb sulfate ions when treating industrial wastewater containing a large amount of sulfate ions and fluoride ions. Under the optimal conditions (Example 2), it can meet the Class III standard of "GB3838-2002 Surface Water Environmental Quality Standard", that is, the sulfate mass concentration is less than 250 mg / L.

[0057] Obviously, the above embodiments are merely examples for the purpose of clearly illustrating the present invention and are not intended to limit the implementation of the present invention. Those skilled in the art will readily appreciate that other variations or modifications may be made based on the above description. It is not necessary and impossible to enumerate all possible implementations here. Obvious variations or modifications derived therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing a fly ash-based composite material for selectively adsorbing sulfate and its application, characterized by: The following steps are involved: (1) Grinding the dry fly ash into particles and sieving to obtain powder material; (2) immersing the powder material in dilute sodium hydroxide for alkali washing and modification, and then drying the modified powder material to obtain an alkali-modified fly ash material; (3) immersing the alkali-modified fly ash material in a YCl3 solution for further activation treatment with a metal salt, and then drying to obtain an activated fly ash material; (4) The activated fly ash material is placed in a muffle furnace for full calcination, and the fly ash-based composite material is obtained after cooling.

2. The method for preparing the fly ash-based composite material for selective sulfate adsorption according to claim 1, characterized in that: In step (4), the roasting parameters are set as follows: roasting temperature 600-900°C, heating rate 10°C / min, roasting time 1-2h, and holding time 0.5-1.5h.

3. The method for preparing the fly ash-based composite material for selective sulfate adsorption according to claim 1, characterized in that: In step (2), the solid-liquid ratio of the powder material to the dilute sodium hydroxide is 0.1 to 0.5 g / mL, and the duration of the immersion modification treatment is 2 to 4 hours.

4. The method for preparing the fly ash-based composite material for selective sulfate adsorption according to claim 1, characterized in that: In step (3), the solid-liquid ratio of the activated fly ash material to the YCl3 solution is 0.2 to 0.8 g / mL, and the duration of the immersion activation treatment is 2 to 4 hours.

5. The method for preparing the fly ash-based composite material for selective sulfate adsorption according to claim 1, characterized in that: In steps (2) and (3), the drying temperature is 105-150°C.

6. The method for preparing the fly ash-based composite material for selective sulfate adsorption according to claim 1, characterized in that: In step (1), the grinding is dry powder, and the grinding is performed to a 100-mesh sieve residue of 1%.

7. A fly ash-based composite material for selectively adsorbing sulfate, characterized in that: The method is prepared by any one of claims 1 to 6.

8. The fly ash-based composite material for selective sulfate adsorption according to claim 7, characterized in that: The fly ash has an average silicon dioxide content of 30-40%; the concentration of the dilute sodium hydroxide is 0.1 mol / L; and the concentration of the YCl3 solution is 0.5 mol / L.

9. Use of the fly ash-based composite material for selectively adsorbing sulfate as claimed in claim 7 or 8 in treating wastewater containing sulfate.

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