Composite modified zeolite for efficient solidification of fly ash heavy metals, preparation method and application

Abstract

The present invention relates to a composite modified zeolite for efficiently solidifying fly ash heavy metals, a preparation method and an application thereof. The composite modified zeolite is a base-phosphate-carbonate composite modified zeolite, and its pH is 7.2-9.1. The surface is loaded with 31%-50% phosphorus and 12%-36% carbon by mass fraction, wherein the phosphorus is loaded in the form of a phosphate group and the carbon is loaded in the form of a carbonate group; the phosphate group includes PO4 3‑ , the carbonate type includes -CO3 2‑ Using this composite modified zeolite as the immobilization and stabilization material, adding 1% of the fly ash mass to the treatment once can reduce the leaching concentrations of lead, cadmium, and zinc in the fly ash to below the limit specified in the "Standard for Pollution Control of Municipal Waste Landfill" (GB 16889-2008). It can be used for the solidification and stabilization of heavy metals in incineration fly ash, especially lead, cadmium, and zinc in the solidified and stabilized fly ash.

Description

Technical Field

[0001] The present invention relates to the technical field of heavy metal treatment of incineration fly ash, and more particularly to a composite modified zeolite for efficiently solidifying heavy metals in fly ash, a preparation method and an application thereof. Background Art

[0002] Zeolites include artificial zeolites and natural zeolites. Natural zeolites are porous aluminosilicate minerals composed of aluminosilicates, exchangeable cations, and zeolite water. Their basic skeleton is composed of multiple silicon-oxygen tetrahedra (SiO4) and aluminum-oxygen tetrahedra (AlO4). Silicon and aluminum atoms are located at the center of the tetrahedrons, connected to the four surrounding oxygen atoms through oxygen bridge bonds, thus forming a three-dimensional network structure. Natural zeolites have large cavities in this structure, which are interconnected by pores, giving the zeolite a large porosity and specific surface area. These cavities and pores are usually filled with exchangeable cations and zeolite water. These cations are highly mobile and can exchange with cations in the surrounding environment. Due to their special spatial structure, they have good adsorption and ion exchange properties, and are environmentally friendly, low-cost, and have a large specific surface area. They are often used as adsorbents and ion exchangers. However, the adsorption performance of natural zeolites is limited. After modification, the performance of zeolites can be improved to a certain extent.

[0003] For example, patent CN106380049A discloses a method for repairing heavy metal-contaminated sediment and a method for improving farmland soil using modified zeolite molecular sieves. In this patent, a chitosan solution is used to modify the surface of the zeolite to obtain a modified zeolite. The modified zeolite reduces the harm of heavy metals to the ecological environment by changing the occurrence form of heavy metals in the sediment. The modified zeolite can be used to repair heavy metal-contaminated sediment, wherein the exchangeable state of Pb is reduced by 2-3%, the exchangeable state of Cu is reduced by 1-3%, the exchangeable state of Zn is reduced by 1-4%, and the exchangeable state of Cd is reduced by 1-12%. However, the modified zeolite obtained by a single modification method still has a poor adsorption effect on heavy metals.

[0004] Patent CN104437391A discloses a modified zeolite and its preparation method and use. In this patent, the modified zeolite is obtained by combining sodium nitrate, microwave, low-temperature calcination and dodecyltrimethylammonium bromide. The adsorption rate of chromium ions or cadmium ions in chromium-containing or cadmium-containing wastewater can reach more than 95%. However, the solidification and stabilization effect of the modified zeolite on different types of heavy metals in the same sample will be significantly different. For example, the article "Study on the Adsorption Characteristics of Modified Zeolite on Heavy Metal Ions" published by Xu Xiuyun clearly mentioned that when modified zeolite is used as an adsorbent, when there are multiple heavy metal ions in the solution, there is adsorption competition between the ions, among which the competitive ability is Pb 2+ >Cd 2+ >Zn 2+ , especially Pb 2+ with cd 2+、Zn 2+ There was obvious antagonistic adsorption between them.

[0005] At present, modified zeolite is widely used in the treatment of heavy metals in wastewater and soil, but it is rarely used in the treatment of heavy metals in fly ash from the incineration of domestic waste. The fly ash produced during the incineration of domestic waste contains a variety of high-concentration heavy metals and is a hazardous waste. It is included in the "National List of Hazardous Wastes". It is necessary to reduce the effectiveness, mobility and migration of heavy metals in the fly ash so that the toxicity concentration of heavy metals in the incineration fly ash meets the limit requirements of the "Standard for the Control of Pollution from Domestic Waste Landfills" (GB 16889-2008) before it can be landfilled in the designated area of ​​the domestic waste landfill. According to the "Standard for the Control of Pollution from Domestic Waste Landfills" (GB 16889-2008), the concentration limit of lead is 0.25mg / L, the concentration limit of cadmium is 0.15mg / L, and the concentration limit of zinc is 100mg / L. The existing modified zeolite is not very effective in treating waste containing Pb 2+ 、Cd 2+ 、Zn 2+ When there are many heavy metals, Pb 2+ with cd 2+ 、Zn 2+ There is a clear antagonistic adsorption between them, making it difficult to achieve efficient adsorption of multiple heavy metals such as lead, cadmium, and zinc simultaneously. Therefore, based on the characteristics of incineration fly ash, a stabilization material that can simultaneously and efficiently solidify and stabilize lead, cadmium, and zinc is studied, which is beneficial to the harmless disposal of hazardous waste incineration fly ash. Summary of the Invention

[0006] In response to the above defects or improvement needs of the prior art, the present invention provides a composite modified zeolite for efficiently solidifying heavy metals in fly ash, a preparation method and an application thereof. The purpose is to find that a natural zeolite is modified by using an alkali modification solution and a phosphoric acid-carbonic acid group composite modification solution respectively. The composite modified zeolite obtained after the two modifications can simultaneously and efficiently solidify lead, cadmium and zinc in incineration fly ash. Surprisingly, it is found that adding 1% of the fly ash mass of the composite modified zeolite and performing a solidification treatment once can make the leaching content of lead, cadmium and zinc in the fly ash lower than the standard limit, thereby solving the problem of existing modified zeolites due to Pb 2+ with cd 2+ 、Zn 2+ There is an obvious antagonistic effect between them, making it difficult to achieve the technical problem of simultaneously and efficiently solidifying lead, cadmium and zinc in incineration fly ash.

[0007] To achieve the above-mentioned object, according to one aspect of the present invention, a composite modified zeolite for simultaneously and efficiently solidifying lead, cadmium and zinc in fly ash heavy metals is provided, characterized in that the composite modified zeolite is a base-phosphate-carbonate composite modified zeolite with a pH of 7.2 to 9.1, and a surface loading of 31% to 50% phosphorus and 12% to 36% carbon by mass, wherein the phosphorus is loaded in the form of a phosphate group and the carbon is loaded in the form of a carbonate group; the phosphate group includes -PO4 3- , the carbonate type includes -CO3 2- .

[0008] Preferably, the composite modified zeolite, the base-phosphate-carbonate composite modified zeolite, has a specific surface area of ​​40.27 to 60.19 m 2 / g, particle size is 0.2-0.4mm, pore volume is 0.07-0.10cm 3 / g.

[0009] According to another aspect of the present invention, there is also provided a method for preparing the composite modified zeolite according to the present invention, which comprises the following steps:

[0010] (1) Alkali modification: Dry natural zeolite is first modified with an alkali modification solution, solid-liquid separation is performed, and the solid phase is dried to obtain the alkali-modified zeolite; the OH in the alkali modification solution is - Concentration is 0.50~1.20mol / L;

[0011] (2) Phosphoric acid-carbonic acid group composite modification: The obtained base-modified zeolite is modified again with a phosphoric acid-carbonic acid group composite modification solution, and after solid-liquid separation and solid phase drying, a base-phosphate-carbonic acid group composite modified zeolite is obtained;

[0012] The phosphoric acid-carbonic acid group composite modified solution is prepared by mixing a phosphoric acid solution with a concentration of 0.10-1.20 mol / L and a carbonic acid solution with a concentration of 0.10-0.80 mol / L at a volume ratio of 1:0.5-2 at room temperature with stirring. The phosphoric acid group includes -PO4 3- , the carbonate group includes -CO3 2- .

[0013] Preferably, the preparation method of the composite modified zeolite capable of simultaneously and efficiently solidifying lead, cadmium and zinc in fly ash heavy metals comprises the following steps: (1) adding 20 to 50 g of zeolite powder per liter of base modification solution, mixing thoroughly, and stirring at room temperature for 2 to 6 hours for the first modification;

[0014] And add 10-20g of the base modified zeolite obtained in step (1) per liter of phosphoric acid-carbonic acid group composite modification solution, and stir at room temperature for 2h to 8h to carry out the second modification.

[0015] Preferably, in the method for preparing the composite modified zeolite capable of simultaneously and efficiently solidifying lead, cadmium and zinc in fly ash heavy metals, the alkaline modified solution comprises one or more solutions of sodium hydroxide and potassium hydroxide, wherein OH - The concentration is 0.50-1.00 mol / L; the molar ratio of phosphate group to carbonate group in the phosphate-carbonate group composite modification solution is 1:0.12-12.0, wherein the phosphate group solution is potassium phosphate and / or sodium phosphate solution, and the carbonate group solution is sodium carbonate and / or potassium carbonate solution.

[0016] Preferably, in the method for preparing the composite modified zeolite that simultaneously and efficiently solidifies lead, cadmium and zinc in fly ash heavy metals, the alkaline modification solution is a mixed solution of sodium hydroxide and potassium hydroxide, and the sodium hydroxide and potassium hydroxide are mixed and prepared according to a solid matter mass ratio of 1:0.5 to 1.5.

[0017] Preferably, in the preparation method of the composite modified zeolite that can simultaneously and efficiently solidify lead, cadmium and zinc in fly ash heavy metals, the solid phase is dried, and the solid phase material is dried at 30°C to 50°C and then ground into powder and passed through a 20-60 mesh sieve.

[0018] According to another aspect of the present invention, there is also provided an application of the composite modified zeolite according to the present invention in solidifying and stabilizing heavy metals in incineration fly ash.

[0019] Preferably, the application uses the composite modified zeolite of the present invention as a solidifying and stabilizing material, which is added at 1.0% to 3.0% of the mass of the incineration fly ash and stirred evenly; and water is added at 20% to 60% of the mass of the incineration fly ash and mixed and stirred for 10 to 30 minutes. After sufficient mixing, it is placed in a natural state for 2 to 7 days.

[0020] Preferably, in the application, the composite modified zeolite is added once for stabilization treatment according to 1% of the mass of the incineration fly ash, so that the leaching concentrations of lead, cadmium and zinc in the heavy metals of the incineration fly ash meet the landfill requirements.

[0021] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0022] The base-phosphate-carbonate composite modified zeolite provided by the present invention has a significantly improved specific surface area and porosity after composite modification with bases and phosphate-carbonate groups, and simultaneously promotes the loading of a large number of hydroxyl groups, phosphate groups and carbonate groups on its surface. These groups can form metal coordination complexes with lead, cadmium and zinc in fly ash heavy metals through complexation, coprecipitation and the like, and the two can play a synergistic role, thereby enhancing the adsorption performance of the zeolite for cadmium and zinc. The lead, cadmium and zinc in the fly ash can be simultaneously and efficiently solidified and stabilized. When the addition amount of the zeolite is 1% of the fly ash mass, a single solidification and stabilization treatment can make the leaching content of lead, cadmium and zinc in the incineration fly ash lower than the limit specified in the "Standard for Pollution Control of Municipal Waste Landfill" (GB 16889-2008). The application prospect is good, and the preparation process is simple, operates at room temperature and pressure, is environmentally friendly, and has no secondary pollution, and has great promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The solidification and stabilization effect of the composite modified zeolite material on heavy metals (lead, cadmium and zinc) in incineration fly ash in Example 2;

[0024] Figure 2 This is the solidification and stabilization effect of the composite modified zeolite material in Example 3 on heavy metals (lead, cadmium and zinc) in incineration fly ash. DETAILED DESCRIPTION

[0025] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0026] the term:

[0027] "Base" is the abbreviation of "alkaline group" in chemistry, such as OH in inorganic substances. - In organic compounds, most basic groups contain nitrogen atoms and are called nitrogenous bases. Amino group (-NH2) is the simplest nitrogenous base. In biochemistry, it is also called nucleobase or nitrogenous base, which is a nitrogen-containing compound that forms nucleosides. In this invention, "base" refers to the "basic group" in chemistry, mainly referring to the inorganic basic group OH - .

[0028] The adsorption performance and ion exchange capacity of modified zeolite are closely related to the modification conditions and the selection of modifiers. The present invention uses a relatively low concentration of alkaline modification solution (alkaline group concentration is 0.50mol / L~1.20mol / L) to modify natural zeolite for the first time. It is found that not only the material cost is reduced, but also the hydroxyl loading capacity can be increased, and the functional groups and void structure can be increased; further, a phosphoric acid-carbonic acid group composite modification solution is used for the second modification, which can enable the phosphoric acid group and the carbonate group to generate the maximum quantitative load on the zeolite to ensure that the zeolite surface is loaded with a large number of phosphoric acid groups and carbonate groups. After two modifications, a composite modified zeolite is obtained. The composite modified zeolite is used as a fly ash heavy metal solidification and stabilization material, which can reduce the leaching content of lead, cadmium and zinc in the incineration fly ash by 88.82%, 91.06% and 54.53% respectively, and the leaching concentrations of lead, cadmium and zinc in the incineration fly ash heavy metals after one treatment at an addition amount of 1% are lower than those in the "Landfill Pollution Control Standard for Domestic Waste" (GB 16889-2008) stipulates the limit value, that is, the incineration fly ash can be directly put into the landfill area of ​​domestic waste for landfill disposal after being treated with the modified zeolite.

[0029] The phosphoric acid-carbonic acid group composite modified solution is prepared by mixing a phosphoric acid solution with a concentration of 0.10-1.20 mol / L and a carbonate solution with a concentration of 0.10-0.80 mol / L at a volume ratio of 1:0.5-2 at room temperature with stirring; preferably, the phosphoric acid-carbonic acid group composite modified solution has a molar ratio of phosphoric acid to carbonate of 1:0.12-12.0.

[0030] Based on this, the present invention provides a method for preparing a composite modified zeolite that can simultaneously and efficiently solidify lead, cadmium and zinc heavy metals in fly ash, which comprises the following steps:

[0031] (1) Alkali modification: Dry natural zeolite is first modified with an alkali modification solution, solid-liquid separation is performed, and the solid phase is dried to obtain the alkali-modified zeolite; the OH in the alkali modification solution is - The concentration is 0.50-1.20 mol / L. In the present invention, it is found that the use of an alkaline solution within this concentration range to load hydroxyl groups for modification can ensure that the surface is loaded with hydroxyl functional groups and increase the void structure while reducing costs.

[0032] (2) Phosphoric acid-carbonic acid group composite modification: The obtained base-modified zeolite is modified again with a phosphoric acid-carbonic acid group composite modification solution, and after solid-liquid separation and solid phase drying, a base-phosphate-carbonic acid group composite modified zeolite is obtained;

[0033] The phosphoric acid-carbonic acid group composite modified solution is prepared by mixing a phosphoric acid solution with a concentration of 0.10-1.20 mol / L and a carbonic acid solution with a concentration of 0.10-0.80 mol / L at a volume ratio of 1:0.5-2 at room temperature with stirring. The phosphoric acid group includes -PO4 3- , the carbonate group includes -CO3 2- .

[0034] In the present invention, using this concentration of the phosphoric acid-carbonic acid composite modification solution for modification has been found to maximize the loading of phosphate and carbonate groups on the zeolite, ensuring a large number of phosphate and carbonate groups on the zeolite surface. Preferably, the molar ratio of phosphate to carbonate groups in the phosphoric acid-carbonic acid composite modification solution is 1:0.12 to 12.0.

[0035] Furthermore, 20 to 50 g of dry zeolite powder is added per liter of base-modified solution, mixed thoroughly, stirred at room temperature for 2 to 6 hours for the first modification, solid-liquid separation, and solid phase drying to obtain base-modified zeolite; the base-modified solution includes one or more solutions of sodium hydroxide and potassium hydroxide, preferably OH. - The concentration is 0.50 to 1.00 mol / L. In some embodiments, the base modification solution is a mixed solution of sodium hydroxide and potassium hydroxide, wherein the sodium hydroxide and potassium hydroxide are mixed in a solid matter weight ratio of 1:0.5 to 1.5.

[0036] Preferably, 10-20 g of the base-modified zeolite obtained in step (1) is added per liter of the phosphoric acid-carbonic acid group composite modification solution, and the mixture is stirred at room temperature for 2 h to 8 h for the second modification. After solid-liquid separation and solid phase drying, the base-phosphate-carbonic acid group composite modified zeolite is obtained; the molar ratio of the phosphoric acid group to the carbonate group in the phosphoric acid-carbonic acid group composite modification solution is 1:0.12 to 12.0, wherein the phosphoric acid group solution is potassium phosphate and / or sodium phosphate solution, and the carbonate group solution is sodium carbonate and / or potassium carbonate solution.

[0037] In some embodiments, a phosphate solution and a carbonate solution are mixed in a volume ratio of 1:0.5-2.0, wherein the phosphate group concentration in the phosphate solution is 0.10-1.20 mol / L, and the carbonate group concentration in the carbonate solution is 0.10-0.80 mol / L; the phosphate includes one or more of potassium phosphate and sodium phosphate, and the carbonate includes one or more of potassium carbonate and sodium carbonate.

[0038] In some embodiments, the solid phase drying is to dry the solid phase at 30° C. to 50° C., and after drying, the solid phase is ground into powder and passed through a 20-60 mesh sieve, which is the base-modified zeolite or base-phosphate-carbonate composite modified zeolite.

[0039] In addition, the present invention also provides a base-phosphate-carbonate composite modified zeolite, wherein the pH of the composite modified zeolite is 7.2-9.1, and the surface loading is 31%-50% phosphorus and 12%-36% carbon by mass fraction, wherein the phosphorus is loaded in the form of a phosphate group and the carbon is loaded in the form of a carbonate group; the phosphate group includes -PO4 3- , the carbonate type includes -CO3 2- .

[0040] The composite modified zeolite preferably has a specific surface area of ​​40.27 to 60.19 m 2 / g, particle size is 0.2-0.4mm, pore volume is 0.07-0.10cm 3 / g.

[0041] In the heavy metal adsorption experiment, the results showed that the composite modified zeolite can simultaneously and efficiently solidify lead, cadmium and zinc in fly ash heavy metals. The use of the composite modified zeolite to treat incineration fly ash can reduce the leaching content of lead, cadmium and zinc in the incineration fly ash by 88.82%, 91.06% and 54.53%, respectively. Moreover, when the addition amount is 1%, the leaching concentrations of lead, cadmium and zinc in the incineration fly ash after one treatment are all lower than the limit values ​​specified in the "Standard for Pollution Control of Municipal Waste Landfill" (GB 16889-2008). It is speculated that there are two reasons for this. First, the specific surface area and porosity of the zeolite are increased after modification, which improves the adsorption performance of the zeolite itself and is conducive to the formation of chelate precipitates with heavy metals. Second, the modified zeolite contains hydroxyl groups (such as -OH) and phosphate groups (such as -PO4 3- ) and carbonate types (such as -CO3 2- ), these groups can form metal coordination complexes with heavy metals cadmium and zinc through complexation, co-precipitation, etc., synergistically enhancing the adsorption performance of zeolite for cadmium and zinc. The synergistic effect of the two further reduces the effectiveness of heavy metals in incineration fly ash, thereby significantly reducing the toxicity of heavy metal leaching from incineration fly ash.

[0042] The present invention also provides a method for solidifying and stabilizing heavy metals in incineration fly ash, which comprises the following steps:

[0043] Add the base-phosphate-carbonate composite modified zeolite material of the present invention according to 1.0% to 3.0% of the mass of the incineration fly ash and stir evenly;

[0044] Add 20% to 60% of the mass of the incineration fly ash with water and mix for 10-30 minutes. After fully mixing, place it in a natural state for 2 to 7 days.

[0045] In some embodiments, adding 1% of the mass of the composite modified zeolite to the incineration fly ash for stabilization treatment once can make the leaching concentrations of lead, cadmium and zinc in the incineration fly ash heavy metals lower than the limit values ​​specified in the "Municipal Waste Landfill Pollution Control Standard" (GB16889-2008), meeting the landfill requirements.

[0046] The following are examples

[0047] Example 1 Preparation of base-phosphate-carbonate composite modified zeolite

[0048] (1) Alkali modification: obtain dried zeolite powder, add 20 g of zeolite powder per liter of alkaline modification solution, mix thoroughly, stir at room temperature for 4 h, separate the solid and liquid, dry the solid phase at 35°C, grind into powder, and pass through a 20-mesh sieve to obtain the alkaline-modified zeolite powder;

[0049] The base-modified solution is a solution obtained by mixing an alkaline substance with deionized water. In this embodiment, potassium hydroxide solution is used and is obtained as follows:

[0050] Add dry sodium hydroxide per liter of deionized water and mix thoroughly. Stir at room temperature for 0.2 hours to obtain a base-modified solution in which the potassium hydroxide concentration is 0.80 mol / L.

[0051] (2) Phosphoric acid-carbonic acid group composite modification: A sodium phosphate solution with a concentration of 0.60 mol / L and a sodium carbonate solution with a concentration of 0.48 mol / L were mixed and stirred at room temperature at a volume ratio of 1:1 for 2 h to obtain the phosphoric acid-carbonic acid group composite modification solution, wherein the molar ratio of the phosphoric acid group to the carbonate group is 1:0.80;

[0052] 10 g of the base-modified zeolite powder obtained in step (1) was added to each liter of the phosphoric acid-carbonic acid group composite modified solution, and the two were stirred at room temperature for 3 h to fully mix. After solid-liquid separation, the solid phase was dried at 30°C and ground into powder, which was passed through a 30-mesh sieve to obtain the base-phosphate-carbonic acid group composite modified zeolite material.

[0053] The surface morphology and surface element content of the base-phosphate-carbonate composite modified zeolite material obtained in this example were analyzed using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS). The surface was loaded with 42.1% phosphorus and 38.6% carbon by mass, wherein the phosphorus was loaded in the form of phosphate groups and the carbon was loaded in the form of carbonate groups. The pH value was measured by a pH meter and was 8.1. The specific surface area was measured by a specific surface area detector and was 49.82 m 2 / g, the particle size measured by a particle size analyzer is 0.2mm, and the pore volume measured by a pore volume analyzer is 0.08cm 3 / g.

[0054] Example 2 Preparation of base-phosphate-carbonate composite modified zeolite

[0055] (1) Base modification: The zeolite was dried and ground into powder, and passed through a 30-mesh sieve to obtain dried zeolite powder. 30 g of zeolite powder was added per liter of base-modified solution and mixed thoroughly. The mixture was stirred at room temperature for 3 h, and the solid-liquid separation was performed. The solid phase was dried at 40°C and ground into powder, and passed through a 30-mesh sieve to obtain base-modified zeolite powder.

[0056] The base-modified solution is prepared according to the following method:

[0057] Add dry sodium hydroxide and potassium hydroxide (sodium hydroxide and potassium hydroxide in a mass ratio of 1:1) per liter of deionized water, mix thoroughly, and stir at room temperature for 0.3 h to prepare a base-modified solution with an OH- concentration of 1.20 mol / L;

[0058] (2) Phosphoric acid-carbonic acid group composite modification: 20 g of the base-modified zeolite powder obtained in step (1) was added to each liter of the phosphoric acid-carbonic acid group composite modification solution, and the two were stirred at room temperature for 4 h to fully mix. After solid-liquid separation, the solid phase was dried at 40°C and ground into powder, and passed through a 40-mesh sieve to obtain the base-phosphate-carbonic acid group composite modified zeolite material;

[0059] The molar ratio of phosphate groups to carbonate groups in the phosphoric acid-carbonic acid group composite modified solution is 1:1, and is specifically prepared according to the following method:

[0060] A phosphate solution with a phosphate group concentration of 0.80 mol / L and a carbonate solution with a carbonate group concentration of 0.80 mol / L are stirred at room temperature for 3 hours in a volume ratio of 1:1 to obtain the phosphate-carbonate group composite modified solution, wherein the phosphate solution is a mixed solution of sodium phosphate and potassium phosphate, and the carbonate solution is a mixed solution of sodium carbonate and potassium carbonate.

[0061] The base-phosphate-carbonate composite modified zeolite material obtained in this example has a surface loaded with 45.7% phosphorus and 39.8% carbon by mass, wherein the phosphorus is loaded in the form of phosphate groups and the carbon is loaded in the form of carbonate groups; its pH is 8.3 and its specific surface area is 53.91 m 2 / g, particle size is 0.2mm, pore volume is 0.09cm 3 / g.

[0062] Example 3

[0063] (1) Base modification: The zeolite is dried and ground into powder, and the powder is passed through a 60-mesh sieve to obtain dried zeolite powder. 40 g of zeolite powder is added to each liter of base-modified solution and the mixture is thoroughly mixed. The mixture is stirred at room temperature for 3 h, and the solid-liquid separation is performed. The solid phase is dried at 45°C and ground into powder, and the powder is passed through a 40-mesh sieve to obtain base-modified zeolite powder. The base-modified solution is a 1.00 mol / L potassium hydroxide solution.

[0064] (2) Phosphoric acid-carbonic acid group composite modification: 30 g of the base-modified zeolite powder obtained in step (1) was added to each liter of the phosphoric acid-carbonic acid group composite modification solution, and the two were stirred at room temperature for 2 h to fully mix. After solid-liquid separation, the solid phase was dried at 40°C and ground into powder, and the powder was passed through a 60-mesh sieve to obtain the base-phosphate-carbonic acid group composite modified zeolite material;

[0065] The molar ratio of phosphate group to carbonate group in the phosphate-carbonate group composite modified solution is 1:5.0, and is prepared specifically according to the following method:

[0066] A phosphate solution with a phosphate group concentration of 0.80 mol / L and a carbonate solution with a carbonate group concentration of 4.00 mol / L are stirred at room temperature for 4 hours in a volume ratio of 1:1 to obtain the phosphate-carbonate group composite modified solution, wherein the phosphate solution is a mixed solution of sodium phosphate and potassium phosphate, and the carbonate solution is a mixed solution of sodium carbonate and potassium carbonate.

[0067] The base-phosphate-carbonate composite modified zeolite material obtained in this example has a surface loaded with 45.2% phosphorus and 28.3% carbon by mass, wherein the phosphorus is loaded in the form of phosphate groups and the carbon is loaded in the form of carbonate groups; its pH is 8.7 and its specific surface area is 59.61 m 2 / g, particle size is 0.23mm, pore volume is 0.10cm 3 / g.

[0068] Example 4 Application of Alkali-Phosphate-Carbonate Composite Modified Zeolite Material in the Solidification and Stabilization of Heavy Metals in Incineration Fly Ash

[0069] In this example, the base-phosphate-carbonate composite modified zeolite material obtained in Example 2 was used as a heavy metal solidification and stabilization material to evaluate its effect on the solidification and stabilization of heavy metals in incineration fly ash. The incineration fly ash was obtained from a municipal solid waste incineration power plant in a certain area of ​​South China. The leaching method of the "Solid Waste Leaching Toxicity Leaching Method - Acetate Buffer Solution Method" (HJ / T300-2007) was used to measure the leaching contents of heavy metals lead, cadmium, and zinc in the incineration fly ash. The results were 1.61 mg / L, 1.23 mg / L, and 150 mg / L, respectively. The leaching contents of heavy metals lead, cadmium, and zinc in the incineration fly ash were all higher than the "Standard for Pollution Control of Municipal Solid Waste Landfill" (GB 16889-2008). The incineration fly ash was naturally air-dried, ground, and passed through a 40-mesh sieve for later use.

[0070] The specific steps include:

[0071] Four groups of incineration fly ash were taken respectively, with the dry weight of each group of fly ash being 1000 g. One group was a blank group (CK) without the addition of solidification and stabilization materials, one group was a control group (FS) with the addition of 1% by mass of unmodified zeolite material to the incineration fly ash, one group was a base-modified group (H-FS) with the addition of 1% by mass of base-zeolite modified material to the incineration fly ash, and one group was a base-phosphate-carbonate composite modified zeolite material with the addition of 1% by mass of base-phosphate-carbonate composite modified zeolite material to the incineration fly ash as the experimental group (PC-FS). 200 g of water was added to each group and the mixture was stirred for 20 minutes. After being fully mixed, the mixture was placed in a natural state for curing for 2 days.

[0072] After curing, the ash was dried, ground and passed through a 20-mesh sieve. The heavy metal leaching content of the incineration fly ash was determined according to the leaching procedure of the "Solid Waste Leaching Toxicity Leaching Method - Acetate Buffer Solution Method" (HJ / T300-2007). The results are shown in Table 1. Compared with the limit values ​​specified in the "Landfill Pollution Control Standard for Municipal Waste" (GB 16889-2008), the results are shown in Table 1. Figure 1 shown.

[0073] Table 1 Effect of composite modified zeolite on the solidification and stabilization of heavy metals (lead, cadmium and zinc) in incineration fly ash

[0074]

[0075] As can be seen from Table 1, compared with the control group, the base-phosphate-carbonate composite modified zeolite material used in the experimental group significantly reduced the leaching content of lead, cadmium and zinc in the incineration fly ash, indicating that the base-phosphate-carbonate composite modified zeolite material provided by the present invention can simultaneously solidify and stabilize lead, cadmium and zinc in the incineration fly ash, and the leaching effects of heavy metal lead, cadmium and zinc after solidification and stabilization of the composite modified material are 1.79 times, 1.87 times and 5.11 times that of the control group, respectively, and there is a significant difference compared with the control group (P<0.05); at the same time, compared with the base-modified group, although the leaching content of heavy metal lead, cadmium and zinc in the incineration fly ash is reduced after treatment, it is still excessive, and the composite modified zeolite material provided by the present invention can make the leaching content of heavy metal lead, cadmium and zinc in the incineration fly ash lower than the limit values ​​specified in GB 16889-2008 after one treatment, indicating that the stabilization material provided by the present invention has significantly better solidification and stabilization ability for lead, cadmium and zinc in the incineration fly ash. Moreover, after adding 1% of the composite modified zeolite material provided by the present invention and undergoing a single stabilization treatment, the leaching content of heavy metals lead, cadmium and zinc in the fly ash meets the limit requirements specified in the "Landfill Pollution Control Standard for Municipal Waste" (GB 16889-2008), and the fly ash can be directly landfilled after stabilization treatment.

[0076] Example 5

[0077] In this example, the base-phosphate-carbonate composite modified zeolite material obtained in Example 3 was used as a heavy metal solidification and stabilization material to evaluate its effect on the solidification and stabilization of heavy metals in incineration fly ash. The incineration fly ash was obtained from a municipal solid waste incineration power plant in a certain area of ​​South China. The leaching method of the "Solid Waste Leaching Toxicity Leaching Method - Acetate Buffer Solution Method" (HJ / T300-2007) was used to measure the leaching contents of heavy metals lead, cadmium, and zinc in the incineration fly ash. The results were 1.61 mg / L, 1.23 mg / L, and 150 mg / L, respectively. The leaching contents of heavy metals lead, cadmium, and zinc in the incineration fly ash were all higher than the "Standard for Pollution Control of Municipal Solid Waste Landfill" (GB 16889-2008). The incineration fly ash was naturally air-dried, ground, and passed through a 40-mesh sieve for later use.

[0078] The specific steps include:

[0079] Four groups of incineration fly ash were taken respectively, with the dry weight of each group of fly ash being 500 g. One group was a blank group (CK) without the addition of solidification and stabilization materials, one group was a control group (FS) with the addition of 2% by mass of unmodified zeolite material to the incineration fly ash, one group was a base-modified group (H-FS) with the addition of 2% by mass of base-zeolite modified material to the incineration fly ash, and one group was a base-phosphate-carbonate composite modified zeolite material with the addition of 2% by mass to the incineration fly ash as the experimental group (PC-FS). 150 g of water was added to each group and the mixture was stirred for 30 minutes. After being fully mixed, the mixture was placed in a natural state for curing for 5 days.

[0080] After curing, the ash was dried, ground and passed through a 20-mesh sieve. The heavy metal leaching content of the incineration fly ash was determined according to the leaching procedure of the "Solid Waste Leaching Toxicity Leaching Method - Acetate Buffer Solution Method" (HJ / T300-2007). The results are shown in Table 2. Compared with the limit values ​​specified in the "Landfill Pollution Control Standard for Municipal Waste" (GB 16889-2008), the results are shown in Table 2. Figure 2 shown.

[0081] Table 2 Effect of composite modified zeolite on the solidification and stabilization of heavy metals (lead, cadmium and zinc) in incineration fly ash

[0082]

[0083] As shown in Table 2, compared with the control group, the base-phosphate-carbonate composite modified zeolite material used in the experimental group significantly reduced the leaching content of lead, cadmium and zinc in the incineration fly ash. The composite modified zeolite reduced the leaching content of lead, cadmium and zinc by 92.55%, 95.12% and 71.93% respectively. There were significant differences compared with the control group (P<0.05). The leaching content of heavy metal lead, cadmium and zinc in the incineration fly ash after solidification and stabilization with the composite modified zeolite was 92.55%, 95.12% and 71.93% respectively. At the same time, compared with the base-modified group, even if the base-modified zeolite is increased by 1 time, the leaching content of heavy metals lead, cadmium and zinc in the incineration fly ash after stabilization treatment is still excessive. The composite modified zeolite material provided by the present invention is only added by 1%, and the stabilization treatment can make the leaching content of heavy metals lead, cadmium and zinc in the incineration fly ash lower than the prescribed limit. This shows that the stabilization material provided by the present invention has significantly better solidification and stabilization ability for lead, cadmium and zinc in the incineration fly ash.

[0084] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A composite modified zeolite for simultaneously and efficiently solidifying lead, cadmium and zinc in fly ash heavy metals, characterized in that: The composite modified zeolite is a base-phosphate-carbonate composite modified zeolite with a pH of 7.2 to 9.

1. The surface loading is 31% to 50% phosphorus and 12% to 36% carbon by mass, wherein the phosphorus is loaded in the form of a phosphate group and the carbon is loaded in the form of a carbonate group. The phosphate group includes -PO4 3- , the carbonate type includes -CO3 2- .

2. The composite modified zeolite according to claim 1, wherein The base-phosphate-carbonate composite modified zeolite has a specific surface area of ​​40.27 to 60.19 m 2 / g, particle size is 0.2-0.4mm, pore volume is 0.07-0.10cm 3 / g.

3. A method for preparing the composite modified zeolite according to claim 1 or 2, characterized in that: The following steps are involved: (1) Alkali modification: Dry natural zeolite is first modified with an alkali modification solution, solid-liquid separation is performed, and the solid phase is dried to obtain the alkali-modified zeolite; the OH in the alkali modification solution is - Concentration is 0.50~1.20mol / L; (2) Phosphoric acid-carbonic acid group composite modification: The obtained base-modified zeolite is modified again with a phosphoric acid-carbonic acid group composite modification solution, and after solid-liquid separation and solid phase drying, a base-phosphate-carbonic acid group composite modified zeolite is obtained; The phosphoric acid-carbonic acid group composite modified solution is prepared by mixing a phosphoric acid solution with a concentration of 0.10-1.20 mol / L and a carbonic acid solution with a concentration of 0.10-0.80 mol / L at a volume ratio of 1:0.5-2 at room temperature; the phosphoric acid group includes -PO4 3- , the carbonate group includes -CO3 2- .

4. The method for preparing a composite modified zeolite capable of simultaneously and efficiently solidifying lead, cadmium and zinc in fly ash heavy metals as claimed in claim 3, characterized in that: Step (1) adding 20 to 50 g of zeolite powder per liter of base modification solution, mixing thoroughly, and stirring at room temperature for 2 to 6 hours for the first modification; And add 10-20g of the base modified zeolite obtained in step (1) per liter of phosphoric acid-carbonic acid group composite modification solution, and stir at room temperature for 2h to 8h to carry out the second modification.

5. The method for preparing a composite modified zeolite capable of simultaneously and efficiently solidifying lead, cadmium and zinc in fly ash heavy metals as claimed in claim 4, characterized in that: The base modification solution includes one or more solutions of sodium hydroxide and potassium hydroxide. - Concentration is 0.50~1.00mol / L; The molar ratio of phosphate groups to carbonate groups in the phosphate-carbonate group composite modification solution is 1:0.12-12.0, wherein the phosphate group solution is potassium phosphate and / or sodium phosphate solution, and the carbonate group solution is sodium carbonate and / or potassium carbonate solution.

6. The method for preparing a composite modified zeolite capable of simultaneously and efficiently solidifying lead, cadmium and zinc in fly ash heavy metals as claimed in claim 5, characterized in that: The base modification solution is a mixed solution of sodium hydroxide and potassium hydroxide, wherein the sodium hydroxide and potassium hydroxide are mixed and prepared according to a solid matter mass ratio of 1:0.5-1.

5.

7. The method for preparing a composite modified zeolite capable of simultaneously and efficiently solidifying lead, cadmium and zinc in fly ash heavy metals according to any one of claims 3 to 6, characterized in that: The solid phase is dried, and the solid phase material is dried at 30° C. to 50° C., and then ground into powder and passed through a 20-60 mesh sieve.

8. Use of the composite modified zeolite according to claim 1 or 2 in solidifying and stabilizing heavy metals in incineration fly ash.

9. The use according to claim 8, characterized in that The composite modified zeolite according to claim 1 or 2 is used as a solidifying and stabilizing material, added at 1.0% to 3.0% of the mass of the incineration fly ash, and stirred evenly; and water is added at 20% to 60% of the mass of the incineration fly ash and mixed and stirred for 10 to 30 minutes. After sufficient mixing, it is placed in a natural state for 2 to 7 days.

10. The use according to claim 9, characterized in that By adding composite modified zeolite at 1% of the mass of the incineration fly ash for stabilization treatment once, the leaching concentrations of lead, cadmium and zinc in the incineration fly ash heavy metals can meet the landfill requirements.

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