Coal gangue-based Na-type zeolite as well as preparation method and application thereof

Abstract

The invention discloses coal gangue-based Na-type zeolite as well as a preparation method and application thereof, and belongs to the technical field of water treatment. The preparation method of the coal gangue-based Na-type zeolite comprises the following steps: adding coal gangue into an aqueous solution of sodium hydroxide, stirring and aging, and then heating and crystallizing to prepare the coal gangue-based modified material, the stirring and aging conditions are as follows: the aging temperature is 20-80 DEG C, and the aging time is 12-24 hours; the heating crystallization conditions are as follows: the crystallization temperature is 100-140 DEG C, and the crystallization time is 12-24 hours; the mass ratio of the sodium hydroxide to the coal gangue is 1: (0.5-1.5). The preparation method is simple in process, free of a high-temperature calcination process and suitable for large-scale production, the prepared Na-type zeolite has high phosphorus adsorption capacity, the problem of reutilization of coal gangue is solved, efficient phosphorus removal in water can be achieved, and the purpose of turning waste into wealth is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of water treatment, and in particular to a gangue-based Na-type zeolite, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, a large amount of sewage has been effectively treated, but urban river pollution still exists, and the proportion of Class V water bodies is still not low. In Class V water quality lakes and reservoirs, the main pollution indicators are total phosphorus, chemical oxygen demand and permanganate index. Total phosphorus, as the first exceeding factor, still accounts for a much higher proportion of sections exceeding the standard than chemical oxygen demand and ammonia nitrogen, becoming the main pollutant affecting surface water quality. This shows that eutrophication of water bodies, especially phosphorus removal in water, has become a major problem that needs to be solved urgently.

[0003] At present, the commonly used phosphorus removal methods include chemical flocculation, ion exchange and artificial wetland. Although the chemical flocculation method has a stable treatment effect, the system operation is easy to automate, and the phosphorus removal rate can reach about 75%, due to the artificial addition of chemical agents, on the one hand, a large amount of sludge is produced, which is difficult to handle, and on the other hand, it causes an increase in water treatment costs. The ion exchange method uses porous anion exchange resins to selectively absorb and remove phosphorus from sewage. There are a series of problems such as easy poisoning of resin drugs, low exchange capacity and poor selectivity when using ion exchange to remove phosphorus, so it is difficult to apply it on a large scale in actual projects. Artificial wetlands are an enhancement of the purification function of natural wetlands. Its principle is mainly to use the interaction between the matrix, aquatic plants and microorganisms in the wetland, and combine the advantages of chemical, biological and adsorption methods to treat phosphorus in wastewater. Artificial wetlands have the advantages of high efficiency, low investment and low energy consumption in treating sewage, but their disadvantages are large land occupation and difficult operation and maintenance.

[0004] Zeolite is a kind of aluminosilicate mineral with good adsorption and ion exchange properties, which is often used to remove pollutants such as ammonia nitrogen, phosphorus, heavy metals and organic matter in wastewater. Among them, Na-type zeolite, that is, sodium zeolite, as a kind of zeolite, has a series of unique advantages, which are mainly derived from its specific chemical composition and crystal structure: 1) High temperature resistance: Sodium zeolite has good high temperature resistance, which means that it can still maintain its structure and stability under high temperature environment and is not easily destroyed; 2) Chemical stability: Sodium zeolite exhibits high chemical stability and is not easy to react with other substances. This stability allows sodium zeolite to be used as a catalyst in chemical reactions to help accelerate the reaction rate without changing the nature of the reaction; 3) Adsorption: Sodium zeolite has significant adsorption capacity, and its pore and hole structure give it a large internal surface area. These pores are generally greater than 50% of the total volume of the crystal, and are uniform in size and regular in shape, providing conditions for efficient adsorption; 4) Ion exchangeability: Sodium zeolite has ion exchange capacity, which is derived from the exchangeable cations present in its crystal structure, such as Na + This ion exchangeability not only enhances the catalytic activity of sodium zeolite, but also makes it potentially applicable in environmental protection fields, such as wastewater treatment and heavy metal recovery. In summary, Na-type zeolite has many advantages over other zeolites, which make it have important application value in many industrial fields.

[0005] Gangue is an industrial solid waste generated during coal mining and washing. It is a black-gray rock associated with coal seams during coal formation. It has a low carbon content and is harder than coal. Its types include tunneling gangue during tunneling, natural gangue mined from the roof, floor and interlayer during mining, and coal gangue sorted during coal washing. Due to the huge output of gangue and the limitations of geographical location and transportation, a large amount of gangue cannot be consumed in a timely and large-scale manner and can only be stored on site, which seriously affects the growth of vegetation in the mining area and aggravates ecological and environmental problems such as vegetation withering and land desertification in the mining area. Therefore, it is urgent to seek a new resource recycling and treatment method to turn gangue into "treasure" and utilize it as a high-value-added resource.

[0006] When coal gangue is directly used as a carrier material for phosphorus removal in water, the phosphorus removal efficiency is extremely low. The preparation of zeolite-based environmentally friendly materials by hydrothermal modification of coal gangue can achieve the effective utilization of coal gangue, the low-cost preparation of zeolite-based materials, and the control of environmental pollution. It is one of the most promising ways to utilize coal gangue in a high-value manner. However, the preparation processes of the currently used coal gangue-based zeolites are mostly cumbersome and complicated, especially the need for high-temperature calcination processes, which have high process requirements, and most of the zeolites provided are P-type or Y-type zeolites, which have limited phosphorus removal effects. Summary of the invention

[0007] Based on this, the main purpose of this application is to provide a method for preparing coal gangue-based Na-type zeolite. Coal gangue is used as raw material, and Na-type zeolite is prepared through alkali melting and low-temperature hydrothermal crystallization. The process is simple, does not require high-temperature calcination process, and is suitable for large-scale production. The prepared Na-type zeolite has a strong ability to adsorb phosphorus, which not only solves the problem of coal gangue recycling, but also realizes efficient phosphorus removal in water, achieving the purpose of turning waste into treasure.

[0008] The first aspect of the present application provides a method for preparing a gangue-based Na-type zeolite, comprising the following steps:

[0009] The gangue is added into an aqueous solution of sodium hydroxide, stirred and aged, and then heated and crystallized to prepare the gangue-based Na-type zeolite;

[0010] The stirring aging conditions include: aging temperature of 20-80°C, aging time of 12-24h; the heating crystallization conditions include: crystallization temperature of 100-140°C, crystallization time of 12-24h; the mass ratio of sodium hydroxide to coal gangue is 1:0.5-1.5.

[0011] In some embodiments, the aging temperature is 15-25°C; the crystallization temperature is 110-130°C.

[0012] In some embodiments, the aging time is 10-14 hours; the crystallization time is 10-14 hours; and the mass ratio of sodium hydroxide to coal gangue is 1:1-1.5.

[0013] In some embodiments, the crystallization temperature is 105-115° C. or 125-135° C.; and the mass ratio of sodium hydroxide to coal gangue is 1:1 or 1:1.5.

[0014] In some embodiments, the concentration of the aqueous solution of sodium hydroxide is 40-60 g / L.

[0015] In some embodiments, the preparation method further comprises the step of pre-treating the coal gangue; the pre-treatment conditions include: crushing and sieving the coal gangue to a particle size of ≤150 μm.

[0016] In some embodiments, the heating crystallization step further includes solid-liquid separation, washing, drying and grinding steps.

[0017] The second aspect of the present application provides a gangue-based Na-type zeolite prepared by the aforementioned preparation method.

[0018] The third aspect of the present application provides the use of the aforementioned gangue-based Na-type zeolite in treating wastewater.

[0019] In some embodiments, the wastewater is phosphorus-containing wastewater.

[0020] In some embodiments, the mass volume ratio of the gangue-based Na-type zeolite to the wastewater is 1 g: (50-1000) mL.

[0021] Beneficial effects of this application:

[0022] 1. This application uses coal gangue as raw material, fully activates the beneficial metal elements in the coal gangue through alkali melting and low-temperature hydrothermal crystallization, and prepares Na-type zeolite. The process is simple, does not require high-temperature calcination process, and is suitable for large-scale production.

[0023] 2. The Na-type zeolite prepared in the present application has a strong ability to adsorb phosphorus, and has a good removal rate and a high adsorption capacity for phosphorus removal in water. It overcomes the disadvantages of low phosphorus removal efficiency when coal gangue is directly used as a carrier material, and also solves the problem of coal gangue recycling, achieving the purpose of turning waste into treasure.

[0024] 3. The raw materials of this application, coal gangue and sodium hydroxide, are widely available, and the preparation method is simple, economical and fast; there is no need to add any additional precious materials, and the waste "coal gangue" is used as the raw material, so the preparation method is simple and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art description. The drawings are only used to illustrate the preferred implementation methods and are not considered to be limitations of the present application. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0026] Figure 1 The morphology and XRD curves of the original coal gangue sample and coal gangue-based Na-type zeolite.

[0027] Figure 2 These are the phosphorus removal curves of original gangue and gangue-based Na-type zeolite. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of this application clearer and to provide a more thorough and comprehensive understanding of the disclosed content of this application, the technical solution of this application will be clearly and completely described below in conjunction with the specific embodiments of this application and the corresponding drawings. The described embodiments are only part of the embodiments of this application, not all of them.

[0029] The implementation of the present application is described in detail below in conjunction with the accompanying drawings. This embodiment is implemented based on the technical solution of the present application, and a detailed implementation method and specific operation process are given, but the protection scope of the present application is not limited to the following embodiments.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0031] the term

[0032] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0033] In the present application, "plurality", "multiple" and the like, unless otherwise specified, refer to a number greater than or equal to 2. For example, "one or more" or "at least one" means one or greater than or equal to two.

[0034] In the present application, the terms "further", "particularly" and the like are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of the present application.

[0035] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0036] In the present application, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​in the numerical interval is considered to be continuous, and includes the two numerical endpoints (i.e., the minimum value and the maximum value) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers in the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical range disclosed herein should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows broadly including numerical interval types such as percentage intervals, ratio intervals, and ratio intervals.

[0037] In the present application, the term "room temperature" generally refers to 4-35° C., preferably 20±5° C. In the embodiments of the present application, room temperature refers to 20-30° C.

[0038] In this application, unless otherwise specified, the temperature parameter is allowed to be either a constant temperature treatment or to vary within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C and ±1°C are allowed.

[0039] In this application, when referring to the unit of a data range, if there is a unit only after the right endpoint, it means that the units of the left and right endpoints are the same. For example, 2-5h means that the units of the left endpoint "2" and the right endpoint "5" are both h (hours).

[0040] The first aspect of the present application provides a method for preparing a gangue-based Na-type zeolite, comprising the following steps:

[0041] The gangue is added into an aqueous solution of sodium hydroxide, stirred and aged, and then heated and crystallized to prepare the gangue-based modified material;

[0042] The stirring aging conditions include: aging temperature of 20-80°C, aging time of 12-24h; the heating crystallization conditions include: crystallization temperature of 100-140°C, crystallization time of 12-24h; the mass ratio of sodium hydroxide to coal gangue is 1:0.5-1.5.

[0043] Specifically, the aging temperature can be 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, etc., and the aging time can be 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, etc.; the conditions for heating crystallization include: the crystallization temperature can be 100°C, 110°C, 120°C, 130°C, 140 ℃, etc., the crystallization time can be 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h; the mass ratio of sodium hydroxide to coal gangue can be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, etc.

[0044] The present application adopts coal gangue as raw material, fully activates beneficial metal elements in the coal gangue through alkali melting and low-temperature hydrothermal crystallization, and prepares Na-type zeolite. The process is simple, does not require high-temperature calcination process, and is suitable for large-scale production.

[0045] It is understandable that the aging temperature and time, the crystallization temperature and time, and the mass ratio of sodium hydroxide to coal gangue will affect the chemical composition and crystal structure of the prepared zeolite, and thus affect its adsorption and phosphorus removal effect. The present application prepares a coal gangue-based Na-type zeolite with a target structure by optimizing the above conditions. The coal gangue-based Na-type zeolite has a strong ability to adsorb phosphorus, and has a good removal rate and a high adsorption capacity for phosphorus removal in water, overcoming the disadvantages of low phosphorus removal efficiency when coal gangue is directly used as a carrier material.

[0046] In some embodiments, the aging temperature is 15-25°C; the crystallization temperature is 110-130°C.

[0047] In some embodiments, the aging time is 10-14 hours; the crystallization time is 10-14 hours; and the mass ratio of sodium hydroxide to coal gangue is 1:1-1.5.

[0048] In some embodiments, the crystallization temperature is 105-115° C. or 125-135° C.; and the mass ratio of sodium hydroxide to coal gangue is 1:1 or 1:1.5.

[0049] In some embodiments, the concentration of the aqueous solution of sodium hydroxide is 40-60 g / L, specifically 40 g / L, 45 g / L, 50 g / L, 55 g / L, 60 g / L, etc.

[0050] In some embodiments, the preparation method further comprises the step of pre-treating the coal gangue; the pre-treatment conditions include: crushing and sieving the coal gangue to a particle size of ≤150 μm.

[0051] In some embodiments, the heating and crystallization step further includes solid-liquid separation, washing, drying and grinding steps. The conditions for the solid-liquid separation, drying and washing are not particularly limited, and common solid-liquid separation methods (centrifugation, filtration, etc.), common drying methods (such as heating drying, vacuum drying, freeze drying, natural drying, etc.), and common washing methods can be used.

[0052] The second aspect of the present application provides a gangue-based Na-type zeolite prepared by the aforementioned preparation method.

[0053] The third aspect of the present application provides the use of the aforementioned gangue-based Na-type zeolite in treating wastewater.

[0054] In some embodiments, the wastewater is phosphorus-containing wastewater.

[0055] In some embodiments, the mass volume ratio of the gangue-based Na-type zeolite to the wastewater is 1 g: (50-1000) mL.

[0056] Unless otherwise specified, the raw materials used in the following experiments can be purchased from the market.

[0057] The following are specific embodiments.

[0058] Example 1

[0059] The preparation method of gangue-based zeolite, the specific process is as follows:

[0060] 1) Crush and sieve the coal gangue to a particle size of ≤150 μm;

[0061] 2) Prepare 60 mL of 50 g / L sodium hydroxide aqueous solution;

[0062] 3) adding the coal gangue powder to the aqueous solution of sodium hydroxide at a mass ratio of sodium hydroxide to coal gangue (i.e., alkali-ash ratio) of 1:0.5-1.5, stirring and aging at 20-80°C for 12-36h, and then heating and crystallizing in an oven at 90-130°C for 6-24h after stirring evenly. The specific conditions are shown in Table 1;

[0063] (4) The crystallized material is centrifuged, washed, filtered, dried, and ground to prepare gangue-based zeolite.

[0064] Table 1 Specific process parameters of gangue-based Na-type zeolite

[0065]

[0066] The morphology and XRD curve of the gangue-based zeolite (i.e., sample 2) prepared in the second group of experiments are shown in Figure 1 As shown, PDF# 44-0052 in (c) is a standard card for Na-type zeolite. It can be seen that the XRD curve of sample 2 is consistent with PDF# 44-0052, which shows that the gangue-based zeolite of sample 2 is Na-type zeolite.

[0067] Example 2

[0068] Evaluation of phosphorus removal performance of gangue-based zeolite prepared in Example 1

[0069] A total phosphorus solution with an initial concentration of 50 mg / L was prepared to simulate phosphorus-containing wastewater, and the gangue-based zeolite prepared in Example 1 was added respectively. Under the condition of a solid-liquid ratio of 1:250, the mixture was shaken at a speed of 150 rpm for 48 h and 72 h.

[0070] After the experiment, the phosphorus concentration was measured and the removal rate and adsorption amount were calculated.

[0071] Removal rate calculation formula: Formula (1);

[0072] In formula (1), ŋ is the removal rate (%); C0, C e are the initial phosphorus concentration before treatment and the phosphorus concentration after treatment (mg / L), respectively.

[0073] Adsorption capacity calculation formula: Formula (2);

[0074] In formula (2), Q e is the adsorption capacity, mg / g; C0, C eare the initial phosphorus concentration before treatment and the phosphorus concentration after treatment (mg / L), respectively; V is the volume of the solution, L; m is the mass of the adsorbent, g.

[0075] The experimental results of the treatment for 48 hours are shown in Table 1, and the phosphorus removal curve of sample 2 after treatment for 72 hours is shown in Figure 2 As shown in Table 1, it can be seen that the aging temperature and time, crystallization temperature and time, and the mass ratio of sodium hydroxide to coal gangue have a great influence on the performance of the prepared zeolite. Among them, sample 2-3 has the best phosphorus removal effect. Figure 2 It can be seen that the phosphorus removal rate of sample 2 reached 95.9% after 24 hours of treatment, and the adsorption capacity reached 12.79 mg / g.

[0076] Combination Figure 1 It can be seen that sample 2 is a gangue-based Na-type zeolite. It can be seen that the present application has prepared a gangue-based Na-type zeolite by optimizing the above conditions, which has a good phosphorus removal effect and has a good removal rate and a high adsorption capacity for phosphorus removal in water.

[0077] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0078] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A method for preparing gangue-based Na-type zeolite, characterized in that: The steps include: The gangue is added into an aqueous solution of sodium hydroxide, stirred and aged, and then heated and crystallized to prepare the gangue-based Na-type zeolite; The stirring aging conditions include: aging temperature of 20-80°C, aging time of 12-24h; the heating crystallization conditions include: crystallization temperature of 100-140°C, crystallization time of 12-24h; the mass ratio of sodium hydroxide to coal gangue is 1:0.5-1.

5.

2. The preparation method according to claim 1, characterized in that The aging temperature is 15-25°C; the crystallization temperature is 110-130°C.

3. The preparation method according to claim 2, characterized in that: The aging time is 10-14 hours; the crystallization time is 10-14 hours; and the mass ratio of sodium hydroxide to coal gangue is 1:1-1.

5.

4. The preparation method according to claim 3, characterized in that: The crystallization temperature is 105-115° C. or 125-135° C.; the mass ratio of sodium hydroxide to coal gangue is 1:1 or 1:1.

5.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The concentration of the aqueous solution of sodium hydroxide is 40-60 g / L.

6. The preparation method according to any one of claims 1 to 4, characterized in that: The preparation method also includes the step of pre-treating the coal gangue; The pretreatment conditions include: crushing and sieving the coal gangue to make its particle size ≤150 μm.

7. The preparation method according to any one of claims 1 to 4, characterized in that: The heating and crystallization step also includes solid-liquid separation, washing, drying and grinding steps.

8. Gangue-based Na-type zeolite prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the gangue-based Na-type zeolite as claimed in claim 8 in treating wastewater.

10. The use according to claim 9, characterized in that The wastewater is phosphorus-containing wastewater; And / or the mass volume ratio of the gangue-based Na-type zeolite to the wastewater is 1 g: (50-1000) mL.

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