A zirconium hydroxide modified NaA molecular sieve and its preparation method and application

Abstract

The present invention provides a zirconium hydroxide modified NaA molecular sieve, its preparation method and application, relating to the technical fields of molecular sieve synthesis and water treatment. In the present invention, coal gangue is calcined and activated to obtain metakaolin; the metakaolin is mixed with sodium hydroxide, an aluminum source, a zirconium source and water to obtain an initial solution; the initial solution is aged, and the obtained precursor solution is hydrothermally crystallized to obtain a zirconium modified NaA molecular sieve; the zirconium modified NaA molecular sieve is subjected to NH4 + ion exchange and Zr 4+ ion exchange. After the obtained ZrA molecular sieve is impregnated with a soluble zirconium salt solution, it is mixed with an alkali solution for a precipitation reaction to obtain a zirconium hydroxide modified NaA molecular sieve. The present invention can effectively solve the problem of coal gangue accumulation pollution and turn waste into treasure; the present invention can make zirconium hydroxide combine better with the NaA molecular sieve and have a larger zirconium hydroxide loading amount, achieving excellent sulfate adsorption performance; the method of the present invention has a simple process and low cost.

Description

Technical Field

[0001] The invention relates to the technical field of molecular sieve synthesis and water treatment, and in particular to a zirconium hydroxide modified NaA molecular sieve and a preparation method and application thereof. Background Art

[0002] Gangue is solid waste discharged during coal mining and coal washing. It is a black rock that is associated with coal during the coal formation process, has a low coal content and is harder than coal. As an inevitable associated waste in the coal industry, gangue accounts for about 10-15% of coal production. At present, the accumulation and discharge of gangue is serious, which not only wastes resources, but also occupies a large amount of land, which is not conducive to the environmental governance of mining areas. Realizing the resource reuse of gangue will have important economic and environmental benefits.

[0003] As a micro-mesoporous material, NaA molecular sieve has uniform and ordered pores and high specific surface area, excellent ion exchange capacity and good thermal stability. It is widely used in detergent additives, adsorbents and as a carrier of metal ions. Mine water often contains high sulfate ions. This is because coal contains sulfate, which dissolves in water during mining to form sulfate ions. Sulfate ions can cause water quality deterioration and have a negative impact on the ecological environment. Zirconium hydroxide is an amphoteric hydroxide with good selective adsorption capacity for sulfate. There are related technologies to load zirconium hydroxide onto molecular sieves to achieve adsorption and separation of sulfate ions in water, but the molecular sieve has a low loading capacity for zirconium hydroxide, resulting in poor adsorption of sulfate. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a zirconium hydroxide modified NaA molecular sieve and its preparation method and application. The present invention synthesizes NaA molecular sieve from industrial waste coal gangue, turning waste into treasure, and realizes high loading of molecular sieve for zirconium hydroxide, and has excellent adsorption effect on sulfate ions in water.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a zirconium hydroxide modified NaA molecular sieve, comprising the following steps:

[0007] The coal gangue is roasted and activated to obtain metakaolin;

[0008] The metakaolin is mixed with sodium hydroxide, an aluminum source, a zirconium source and water to obtain an initial solution; the metakaolin is calculated as SiO2 and Al2O3, the sodium hydroxide is calculated as Na2O, the aluminum source is calculated as Al2O3, the molar ratio of SiO2, Al2O3, Na2O and water in the initial solution is (1.3-2.4):1:(1.6-6):(130-300), and the concentration of the zirconium source in the initial solution is 0.01-0.2 mol / L;

[0009] Aging the initial solution to obtain a precursor solution;

[0010] The precursor solution is subjected to hydrothermal crystallization to obtain a zirconium-modified NaA molecular sieve;

[0011] The zirconium-modified NaA molecular sieve is successively subjected to NH4 + Ion exchange and Zr 4+ Ion exchange to obtain ZrA molecular sieve;

[0012] After the ZrA molecular sieve is impregnated with a soluble zirconium salt solution, it is mixed with an alkali solution to undergo a precipitation reaction, thereby obtaining the zirconium hydroxide-modified NaA molecular sieve.

[0013] Preferably, the calcination activation is carried out at a temperature of 750-900° C. for a time of 2-4 hours in an air atmosphere.

[0014] Preferably, the aluminum source includes sodium metaaluminate and / or aluminum nitrate; and the zirconium source includes zirconium oxychloride and / or zirconium nitrate.

[0015] Preferably, the aging temperature is 40-70° C., the time is 0-4 hours, and the time is not 0.

[0016] Preferably, the hydrothermal crystallization temperature is 80-100° C., the time is 0-8 hours, and the time is not 0.

[0017] Preferably, the NH4 + The ion exchange is carried out in a soluble ammonium salt solution containing NH4 + The concentration of NH4 is 0.1~0.2mol / L. + The temperature of ion exchange is 50~70℃ and the time is 2~6h.

[0018] Preferably, the Zr 4+ The ion exchange is carried out in a soluble zirconium salt solution, wherein Zr 4+ The concentration of Zr is 0.1~0.2mol / L; 4+ The temperature of ion exchange is 50~70℃ and the time is 2~6h.

[0019] Preferably, the soluble zirconium salt solution contains Zr 4+ The concentration is 0.1-0.2 mol / L, and the impregnation is equal volume impregnation; the temperature of the precipitation reaction is 30-70°C, and the time is 6-12h.

[0020] The present invention provides a zirconium hydroxide modified NaA molecular sieve prepared by the preparation method described in the above technical scheme.

[0021] The present invention provides the use of the zirconium hydroxide modified NaA molecular sieve described in the above technical solution in adsorbing sulfate ions in wastewater.

[0022] The present invention provides a method for preparing a zirconium hydroxide modified NaA molecular sieve. Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention uses coal gangue instead of chemical raw materials to synthesize NaA molecular sieve, which can effectively solve the pollution problem of coal gangue accumulation, turn waste into treasure, and be green and environmentally friendly;

[0024] In the present invention, a zirconium source is added to the initial solution. During the aging and hydrothermal crystallization (mainly hydrothermal crystallization) process, along with the depolymerization and condensation of aluminosilicate, zirconium atoms isomorphously replace part of aluminum atoms and enter the NaA molecular sieve framework, which can provide a better pore surface structure for the subsequent loading of zirconium hydroxide active components and is not easy to lose. The present invention adopts a two-step ion exchange, NH4 + Ion exchange removes free Na in the cell + Exchanged for NH4 + , Zr 4+ Ion exchange converts NH4 + Exchanged for Zr 4+ , zirconium hydroxide can be better loaded onto the NaA molecular sieve. Therefore, the present invention can make zirconium hydroxide and the NaA molecular sieve combine better, the zirconium hydroxide loading amount is larger, and a better sulfate adsorption effect is achieved;

[0025] The present invention uses NaA molecular sieve as a support to load zirconium hydroxide, which has a stable structure, a large specific surface area, a short time for ion exchange with metal ions, and a large exchange capacity, and can further ensure high adsorption of sulfate.

[0026] The preparation method provided by the invention has simple process and low cost.

[0027] The present invention provides the use of the zirconium hydroxide modified NaA molecular sieve described in the above technical solution in adsorbing sulfate ions in wastewater. The zirconium hydroxide modified NaA molecular sieve provided by the present invention has a high sulfate adsorption rate, excellent sulfate adsorption performance, and can be repeatedly regenerated. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the process for preparing zirconium hydroxide modified NaA molecular sieve according to an embodiment of the present invention;

[0029] Figure 2 This is the XRD pattern of the zirconium hydroxide modified NaA molecular sieve prepared in Example 2;

[0030] Figure 3 This is the infrared spectrum (FTIR) of the zirconium hydroxide modified NaA molecular sieve prepared in Example 2. DETAILED DESCRIPTION

[0031] The present invention provides a method for preparing a zirconium hydroxide modified NaA molecular sieve, comprising the following steps:

[0032] The coal gangue is roasted and activated to obtain metakaolin;

[0033] The metakaolin is mixed with sodium hydroxide, an aluminum source, a zirconium source and water to obtain an initial solution; the metakaolin is calculated as SiO2 and Al2O3, the sodium hydroxide is calculated as Na2O, the aluminum source is calculated as Al2O3, the molar ratio of SiO2, Al2O3, Na2O and water in the initial solution is (1.3-2.4):1:(1.6-6):(130-300), and the concentration of the zirconium source in the initial solution is 0.01-0.2 mol / L;

[0034] Aging the initial solution to obtain a precursor solution;

[0035] The precursor solution is subjected to hydrothermal crystallization to obtain a zirconium-modified NaA molecular sieve;

[0036] The zirconium-modified NaA molecular sieve is successively subjected to NH4 + Ion exchange and Zr 4+ Ion exchange to obtain ZrA molecular sieve;

[0037] After the ZrA molecular sieve is impregnated with a soluble zirconium salt solution, it is mixed with an alkali solution to undergo a precipitation reaction, thereby obtaining the zirconium hydroxide-modified NaA molecular sieve.

[0038] In the present invention, unless otherwise specified, the raw materials involved are commercially available products well known in the art.

[0039] Figure 1 The schematic diagram of the process for preparing zirconium hydroxide modified NaA molecular sieve according to the embodiment of the present invention is shown below. Figure 1 Provide detailed explanation.

[0040] The invention roasts (also called calcining) coal gangue to activate it and obtain metakaolin.

[0041] In the present invention, the gangue is preferably gangue powder, specifically gangue powder that has passed a 200-mesh sieve. The main component of gangue is kaolinite, which contains a large amount of aluminosilicate. In the present invention, the temperature of the calcination activation is preferably 750-900°C, which can be 800, 850 or 900°C, the time is preferably 2-4h, which can be 2, 3 or 4h, and the heating rate to the temperature of the calcination activation is preferably 10°C / min; the calcination activation is carried out in an air atmosphere. In an embodiment of the present invention, the calcination activation is carried out in a muffle furnace. Gangue generally contains water, organic matter, fixed carbon, etc. After the gangue is calcined at 750-900°C in an air atmosphere, dehydration and decarbonization occur, the kaolinite lattice collapses at high temperature, the lamellar structure is destroyed, the hydroxyl group of the aluminum hydroxide octahedron is removed to become an aluminum oxide tetrahedron, and finally transformed into metakaolin in which silicon oxide tetrahedron and aluminum oxide tetrahedron are polymerized. The present invention uses industrial waste coal gangue as a raw material to synthesize molecular sieves, which can not only expand the source of molecular sieve raw materials and reduce the production cost of molecular sieves, but also solve the problem of coal gangue disposal and realize the resource utilization of coal solid waste.

[0042] After obtaining the metakaolin, the present invention mixes the metakaolin with sodium hydroxide, an aluminum source, a zirconium source and water to obtain an initial solution.

[0043] In the present invention, the aluminum source preferably includes sodium metaaluminate and / or aluminum nitrate; the zirconium source preferably includes zirconium oxychloride and / or zirconium nitrate; and the water is preferably deionized water.

[0044] In the present invention, the mixing is preferably stirring mixing. The present invention has no special requirements on the speed and time of the stirring mixing, as long as the components are mixed evenly.

[0045] In the present invention, the metakaolin is calculated as SiO2 and Al2O3, the sodium hydroxide is calculated as Na2O, the aluminum source is calculated as Al2O3, and the molar ratio of SiO2, Al2O3, Na2O and water in the initial solution is (1.3~2.4):1:(1.6~6):(130~300), preferably 2:1:(1.6~2.8):(200~224); the present invention does not need to supplement an additional silicon source. The present invention controls the molar ratio of the raw materials within the above range, which can ensure that the synthesized NaA molecular sieve has a high degree of crystallinity, which is beneficial to increase the loading amount of subsequent zirconium hydroxide. In the present invention, the concentration of the zirconium source in the initial solution is 0.01~0.2mol / L, which can be 0.01, 0.05, 0.1 or 0.2mol / L; too high a concentration of the zirconium source will destroy the molecular sieve structure.

[0046] After obtaining the initial solution, the present invention ages the initial solution to obtain a precursor solution.

[0047] In the present invention, the aging temperature is preferably 40-70°C, and can be 40, 50, 60 or 70°C; the time is preferably 0-4h (and the time is not 0), and can be 1, 2, 3 or 4h; the aging is preferably carried out under static and constant temperature conditions.

[0048] During the aging process, the aluminum source and the zirconium source gradually dissolve in an alkaline environment, and the metakaolin powder also depolymerizes under the stimulation of the alkali, and the two repolymerize to form a new aluminosilicate aggregate. Appropriate aging temperature can provide thermal kinetic energy, accelerate molecular flow, promote the dissolution of materials, and shorten the growth cycle, but if the aging temperature is too high, it will enter the crystallization stage in advance, resulting in insufficient materials in the reaction system, which is not conducive to the synthesis of molecular sieves. Similarly, controlling the appropriate aging time is conducive to the full dissolution of each component, thereby improving the crystallinity of the molecular sieve, but if the aging time is too long, the water evaporates, and the components condense under the action of the alkali, which hinders the synthesis of the molecular sieve.

[0049] After obtaining the precursor solution, the present invention performs hydrothermal crystallization on the precursor solution to obtain the zirconium-modified NaA molecular sieve.

[0050] In the present invention, the temperature of the hydrothermal crystallization is preferably 80-100°C, which can be 80, 85, 90, 95 or 100°C, and the time is preferably 0-8h (and the time is not 0), which can be 2, 4, 6 or 8h; the hydrothermal crystallization is preferably dynamic hydrothermal crystallization, and the dynamic hydrothermal crystallization is preferably carried out under rotation, and the rotation speed is preferably 10-20r / min. In an embodiment of the present invention, the precursor solution is placed in a reactor lined with polytetrafluoroethylene, and the reactor is then placed in a magnetic stirring oil bath for the hydrothermal crystallization.

[0051] During the hydrothermal crystallization process, zirconium replaces aluminum atoms and is incorporated into the framework, and there is no need to add corrosive acid solutions, such as ammonium fluorozirconate ((NH4)2ZrF6) or other F - Introducing zirconium ions after the solution destroys the molecular sieve framework can save materials, simplify the preparation process, avoid generating polluted waste and polluting the environment, and is environmentally friendly.

[0052] After the hydrothermal crystallization is completed, the present invention preferably sequentially washes, filters and dries the obtained crystallized product to obtain the zirconium-modified NaA molecular sieve. In the present invention, the washing is preferably washing with water until neutral.

[0053] After obtaining the zirconium-modified NaA molecular sieve, the present invention sequentially treats the zirconium-modified NaA molecular sieve with NH4 + Ion exchange and Zr 4+ Ion exchange to obtain ZrA molecular sieve.

[0054] In the present invention, the NH4+ The ion exchange is preferably carried out in a soluble ammonium salt solution, specifically by mixing the zirconium-modified NaA molecular sieve with a soluble ammonium salt solution to carry out the NH4 + Ion exchange. In the present invention, the soluble ammonium salt solution is preferably an aqueous solution of ammonium chloride; NH4 + The concentration of the soluble ammonium salt solution is preferably 0.1-0.2 mol / L. The present invention has no special requirements on the amount of the soluble ammonium salt solution, as long as it can completely immerse the zirconium-modified NaA molecular sieve. In the embodiment of the present invention, the amount ratio of the zirconium-modified NaA molecular sieve to the soluble ammonium salt solution is 5 g: 300 mL. In the present invention, the NH4 + The ion exchange temperature is preferably 50-70°C, and may be 50, 60 or 70°C. The time is preferably 2-6 hours, and may be 2, 4 or 6 hours. + Ion exchange is used to convert the free Na in the unit cell of the zirconium-modified NaA molecular sieve into + Exchange to NH4 + The NH4 + After ion exchange, the obtained reaction solution is preferably filtered, solid phase washed and dried in sequence, and then the subsequent Zr 4+ Ion exchange. In the present embodiment, the NH4 + The molecular sieve obtained after ion exchange is recorded as NH4A molecular sieve.

[0055] In the present invention, the Zr 4+ The ion exchange is preferably carried out in a soluble zirconium salt solution, specifically by converting the NH4 + The molecular sieve obtained after ion exchange (NH4A molecular sieve) is mixed with a soluble zirconium salt solution for Zr 4+ In the present invention, the soluble zirconium salt solution is preferably an aqueous zirconium oxychloride solution; 4+ The concentration of the soluble zirconium salt solution is preferably 0.1-0.2 mol / L. The present invention has no special requirements on the amount of the soluble zirconium salt solution. + The molecular sieve (NH4A molecular sieve) obtained after ion exchange is completely immersed. In the embodiment of the present invention, the ratio of the NH4A molecular sieve to the soluble zirconium salt solution is 5g:400mL. 4+ The ion exchange temperature is preferably 50-70°C, and may be 50, 60 or 70°C. The time is preferably 2-6 hours, and may be 2, 4 or 6 hours. 4+ Ion exchange, NH4 in the molecular sieve unit cell + Exchange to Zr 4+ The Zr 4+After ion exchange, the obtained reaction solution is preferably filtered, solid phase washed and dried in sequence, and then subsequently immersed in a soluble zirconium salt solution. 4+ The molecular sieve obtained after ion exchange is ZrA molecular sieve.

[0056] After obtaining the ZrA molecular sieve, the present invention soaks the ZrA molecular sieve in a soluble zirconium salt solution, and then mixes it with an alkali solution to perform a precipitation reaction, thereby obtaining the zirconium hydroxide modified NaA molecular sieve.

[0057] In the present invention, the soluble zirconium salt solution is preferably an aqueous zirconium oxychloride solution, wherein Zr 4+ The concentration is preferably 0.1-0.2 mol / L; the impregnation is preferably equal volume impregnation, the temperature of the equal volume impregnation is preferably 60-70°C, and the time is preferably 12 hours. In the present invention, the equal volume impregnation can evenly distribute the active components in the pores on the surface of the molecular sieve.

[0058] In the present invention, the alkali solution is preferably ammonia water, the mass fraction of the ammonia water is preferably 25-28%, and the volume ratio of the ammonia water to the soluble zirconium salt solution impregnated with the ZrA molecular sieve is preferably 1:1. In the present invention, the temperature of the precipitation reaction is preferably 30-70°C, which can be 30, 40, 50, 60 or 70°C, and the time is preferably 6-12 hours. After the precipitation reaction, the Zr in the soluble zirconium salt solution impregnated with the ZrA molecular sieve is 4+ The reaction generates a Zr-OH active component, which is loaded on the surface of the molecular sieve. The zirconium incorporated into the molecular sieve framework and the zirconium ions exchanged in the unit cell can change the molecular sieve pores and surface structure, so that it can better load zirconium hydroxide and is not easy to lose. After the precipitation reaction, the present invention preferably filters, washes and dries the obtained molecular sieve in sequence to obtain the zirconium hydroxide modified NaA molecular sieve. In the present invention, the zirconium hydroxide modified NaA molecular sieve is recorded as Zr(OH)4 / ZrA molecular sieve, that is, ZrA molecular sieve loaded with Zr(OH)4.

[0059] In the present invention, the zirconium-doped NaA molecular sieve formed by hydrothermal crystallization is subjected to NH4 + and Zr 4+ Two ion exchange processes can introduce more Zr 4+ , so that zirconium hydroxide and NaA molecular sieve can be better combined and the loading amount can be larger, so as to achieve better sulfate adsorption and multiple desorption and regeneration effects.

[0060] The preparation method provided by the invention has simple process, low cost and little environmental pollution.

[0061] The present invention provides a zirconium hydroxide modified NaA molecular sieve prepared by the preparation method described in the above technical scheme.

[0062] The present invention provides the application of the zirconium hydroxide modified NaA molecular sieve described in the above technical solution in the adsorption of sulfate ions in wastewater. In the present invention, the pH value of the wastewater is preferably 2.5~4, which can be 2.5, 3 or 4, and the concentration of sulfate ions in the wastewater is preferably 400~600 mg / L, which can be 400, 500 or 600 mg / L; the adsorption is preferably carried out at room temperature. The zirconium hydroxide modified NaA molecular sieve provided by the present invention can efficiently and selectively adsorb sulfate ions in wastewater (such as mine water), with a high sulfate removal rate, and has good application prospects in the field of mine water treatment, which can achieve the effect of turning waste into treasure and treating waste with waste. In addition, the zirconium hydroxide modified NaA molecular sieve has excellent regeneration performance, can be repeatedly regenerated and reused, and the regenerated molecular sieve can still maintain an adsorption capacity equivalent to more than 80% of the initial state. In the present invention, the regeneration method is preferably: soaking the adsorption saturated molecular sieve in a NaOH solution to desorb sulfate ions; the concentration of the NaOH solution is preferably 10g / L.

[0063] In order to further illustrate the present invention, the zirconium hydroxide modified NaA molecular sieve provided by the present invention and its preparation method and application are described in detail below in combination with examples, but they should not be construed as limiting the scope of protection of the present invention.

[0064] Example 1

[0065] The preparation steps of zirconium hydroxide modified NaA molecular sieve are as follows (process as shown in Figure 1 shown):

[0066] (1) Calcination and activation: put the coal gangue powder into a crucible, heat it to 800°C in a muffle furnace at a heating rate of 10°C / min and calcine for 2 h to obtain metakaolin, wherein the coal gangue powder is sieved through a 200-mesh sieve;

[0067] (2) Material addition: the metakaolin, sodium hydroxide, sodium aluminate, zirconium oxychloride octahydrate and deionized water are mixed and stirred in a certain molar ratio for 1 hour to obtain an initial solution, wherein the molar ratio is SiO2:Al2O3:Na2O:H2O=2:1:1.6:200, and the concentration of zirconium oxychloride in the initial solution is 0.01 mol / L;

[0068] (3) Static aging: The initial solution was aged at 50°C for 2 h to obtain a precursor solution;

[0069] (4) Dynamic crystallization: Place all the precursor liquid materials in a reactor lined with polytetrafluoroethylene, then place the reactor in a magnetic stirring oil bath, rotate the shaft at a speed of 20 r / min, and perform dynamic hydrothermal crystallization at 90°C for 2 h; add deionized water to the crystallized product and wash it, repeating this process until the system becomes neutral, and then dry it at 60°C for 6 h to obtain a zirconium-modified NaA molecular sieve;

[0070] (5) NH4 + Ion exchange: 5 g of zirconium-modified NaA molecular sieve was mixed with 300 mL of 0.1 mol / L ammonium chloride aqueous solution, heated to 50 °C in a constant temperature water bath and ion exchanged for 2 h, then filtered, washed and dried (dried at 60 °C for 6 h) to obtain NH4A molecular sieve;

[0071] (6) Zr 4+ Ion exchange: 5 g NH4A molecular sieve was mixed with 400 mL 0.1 mol / L zirconium oxychloride aqueous solution, heated to 50 °C in a constant temperature water bath and ion exchanged for 2 h, then filtered, washed and dried to obtain ZrA molecular sieve;

[0072] (7) Loading zirconium hydroxide active component: The ZrA molecular sieve was uniformly mixed with a ZrOCl2 solution with a concentration of 0.1 mol / L, and impregnated at 60°C for 12 h by an equal volume impregnation method. Then, ammonia water (AR, 25-28 wt%, Shanghai Aladdin Biochemical Technology Co., Ltd.) was added, and the ratio of the volume of ammonia water to the volume of 0.1 mol / L ZrOCl2 solution was 1:1. After continuing to impregnate at 60°C for 12 h, the mixture was filtered, washed with deionized water, and dried at 60°C for 12 h to obtain a zirconium hydroxide-modified NaA molecular sieve.

[0073] The sulfate ion adsorption performance of the zirconium hydroxide modified NaA molecular sieve prepared in Example 1 was tested. The test solution was a sodium sulfate aqueous solution, 200 mL of the sodium sulfate aqueous solution, and the amount of the zirconium hydroxide modified NaA molecular sieve added was 1 g. The test results showed that at pH = 2.5, room temperature, sulfate (SO4 2- ) Under the condition of initial concentration of 500mg / L, adsorption for 120min, SO4 2- The adsorption rate is 60%.

[0074] Example 2

[0075] The preparation steps of zirconium hydroxide modified NaA molecular sieve are as follows (process as shown in Figure 1 shown):

[0076] (1) Calcination and activation: same as step (1) in Example 1;

[0077] (2) Material addition: kaolin, sodium hydroxide, sodium aluminate, zirconium oxychloride octahydrate and deionized water were mixed and stirred in a certain molar ratio for 1 hour to obtain an initial solution, the molar ratio of which was SiO2:Al2O3:Na2O:H2O=2:1:2.8:224, and the concentration of zirconium oxychloride in the initial solution was 0.05 mol / L;

[0078] (3) Static aging: The initial solution was aged at 60°C for 2 h to obtain a precursor solution;

[0079] (4) Dynamic crystallization: Place all the precursor liquid materials in a reactor lined with polytetrafluoroethylene, then place the reactor in a magnetic stirring oil bath, rotate the shaft at a speed of 20 r / min, and perform dynamic hydrothermal crystallization at 95°C for 2 h; add deionized water to the crystallized product and wash it, repeating this process until the system becomes neutral, and then dry it at 60°C for 6 h to obtain a zirconium-modified NaA molecular sieve;

[0080] (5) NH4 + Ion exchange: 5 g of zirconium-modified NaA molecular sieve was mixed with 300 mL of 0.1 mol / L ammonium chloride aqueous solution, heated to 60 ° C in a constant temperature water bath and ion exchanged for 4 h, then filtered, washed and dried (dried at 60 ° C for 6 h) to obtain NH4A molecular sieve;

[0081] (6) Zr 4+ Ion exchange: 5 g of NH4A molecular sieve was mixed with 400 mL of 0.1 mol / L zirconium oxychloride aqueous solution, heated to 60 ° C in a constant temperature water bath and ion exchanged for 4 h, then filtered, washed and dried to obtain ZrA molecular sieve;

[0082] (7) Loading zirconium hydroxide active component: The ZrA molecular sieve was uniformly mixed with a 0.1 mol / L ZrOCl2 solution, and then impregnated at 60°C for 12 h by an equal volume impregnation method. Then, ammonia water (AR, 25-28 wt%, Shanghai Aladdin Biochemical Technology Co., Ltd.) was added, and the ratio of the volume of ammonia water to the volume of 0.1 mol / L ZrOCl2 solution was 1:1. After continuing to impregnate at 60°C for 12 h, the mixture was filtered, washed with deionized water, and dried at 60°C for 12 h to obtain a zirconium hydroxide modified NaA molecular sieve, which was recorded as Zr(OH)4 / ZrA molecular sieve.

[0083] Figure 2 This is the XRD pattern of the zirconium hydroxide modified NaA molecular sieve prepared in Example 2. Figure 2The homemade NaA molecular sieve in is the zirconium hydroxide modified NaA molecular sieve prepared in Example 2. It can be seen that the positions and intensities of the five diffraction peaks of the relative crystallinity of the molecular sieve, 7.16°, 10.14°, 23.96°, 27.09°, and 29.92°, are consistent with the diffraction peak positions and intensities of the NaA molecular sieve standard spectrum, and there is no impurity peak, indicating that the molecular sieve prepared in this example is a NaA molecular sieve.

[0084] Figure 3 This is the infrared spectrum (FTIR) of the Zr(OH)4 / ZrA molecular sieve prepared in Example 2. Figure 3 NaA is the zirconium-modified NaA molecular sieve prepared in step (4) of Example 2, and NH4A is the NH4A molecular sieve prepared in step (5) of Example 2. The FTIR spectrum of NaA mainly includes the following absorption peaks: 3465 cm -1 The OH stretching vibration peak of bound water in the molecular sieve is 1646 cm -1 The HOH bending vibration peak of bound water is at 1000cm -1 The peak of Si-O antisymmetric stretching vibration is at 451cm -1 The peak at 554 cm corresponds to the bending vibration of TO (T = Si, Al). -1 The peaks at 3203cm correspond to the bending vibration of Si-O-Al bonds. These peaks are consistent with the characteristics of NaA molecular sieve. Compared with NaA molecular sieve, the FTIR spectrum of NH4A shows two new absorption peaks: 3203cm -1 NH4 + NH stretching vibration peak, 1400 cm -1 NH4 + The NH bending vibration peak indicates that NH4 + Success and Na + Ion exchange was performed. In the FTIR spectrum of Zr(OH)4 / ZrA molecular sieve, 1384 cm -1 A sharp absorption peak of Zr-OH appears at the surface, indicating that Zr(OH)4 is loaded on the NaA molecular sieve.

[0085] The sulfate ion adsorption performance of Zr(OH)4 / ZrA molecular sieve prepared in Example 2 was tested. The test solution was a sodium sulfate aqueous solution, 200 mL of sodium sulfate aqueous solution, and the amount of zirconium hydroxide modified NaA molecular sieve added was 1 g. The test results showed that at pH = 3 and room temperature, sulfate (SO4 2- ) Under the condition of initial concentration of 500mg / L, adsorption for 120min, SO4 2- The adsorption rate was 90%; at pH = 3, room temperature, sulfate (SO4 2-) under the condition of initial concentration of 5g / L, the adsorption capacity is 132.76mg / g. The molecular sieve after adsorption is regenerated by adding 10g / L NaOH solution (500mL) to the molecular sieve after adsorption at room temperature, desorbing for 60min, and repeating the above sulfate ion adsorption performance test (pH=3, room temperature, sulfate (SO4 2- ) Under the condition of initial concentration of 500 mg / L and adsorption for 120 min), the adsorption rate was 73.51%.

[0086] Example 3

[0087] The preparation steps of zirconium hydroxide modified NaA molecular sieve are as follows (process as shown in Figure 1 shown):

[0088] (1) Calcination and activation: same as step (1) in Example 1;

[0089] (2) Material addition: kaolin, sodium hydroxide, sodium aluminate, zirconium oxychloride octahydrate and deionized water were mixed and stirred at a certain molar ratio for 1 hour to obtain an initial solution, the molar ratio of which was SiO2:Al2O3:Na2O:H2O=2:1:2.0:300, and the concentration of zirconium oxychloride in the initial solution was 0.2 mol / L;

[0090] (3) Static aging: The initial solution was aged at 60°C for 2 h to obtain a precursor solution;

[0091] (4) Dynamic crystallization: Place all the precursor liquid materials in a reactor lined with polytetrafluoroethylene, then place the reactor in a magnetic stirring oil bath, rotate the shaft at a speed of 20 r / min, and perform dynamic hydrothermal crystallization at 95°C for 2 h; add deionized water to the crystallized product and wash it, repeating this process until the system becomes neutral, and then dry it at 60°C for 6 h to obtain a zirconium-modified NaA molecular sieve;

[0092] (5) to (7): The same as steps (5) to (7) of Example 1, to obtain zirconium hydroxide modified NaA molecular sieve, denoted as Zr(OH)4 / ZrA molecular sieve.

[0093] The sulfate ion adsorption performance of Zr(OH)4 / ZrA molecular sieve prepared in Example 3 was tested. The test solution was a sodium sulfate aqueous solution, 200 mL of sodium sulfate aqueous solution, and the amount of zirconium hydroxide modified NaA molecular sieve added was 1 g. The test results showed that at pH = 3 and room temperature, sulfate (SO4 2- ) Under the condition of initial concentration of 500mg / L, adsorption for 120min, SO4 2- The adsorption rate is 67%.

[0094] Example 4

[0095] The preparation steps of zirconium hydroxide modified NaA molecular sieve are as follows (process as shown in Figure 1 shown):

[0096] (1) to (4): The same as steps (1) to (4) of Example 1, to obtain zirconium-modified NaA molecular sieve;

[0097] (5) NH4 + Ion exchange: 5 g of zirconium-modified NaA molecular sieve was mixed with 300 mL of 0.2 mol / L ammonium chloride aqueous solution, heated to 70 °C in a constant temperature water bath and ion exchanged for 6 h, then filtered, washed and dried (dried at 60 °C for 6 h) to obtain NH4A molecular sieve;

[0098] (6) Zr 4+ Ion exchange: 5 g of NH4A molecular sieve was mixed with 400 mL of 0.2 mol / L zirconium oxychloride aqueous solution, heated to 70 °C in a constant temperature water bath and ion exchanged for 6 h, then filtered, washed and dried to obtain ZrA molecular sieve;

[0099] (7) Loading zirconium hydroxide active component: The ZrA molecular sieve was uniformly mixed with a 0.1 mol / L ZrOCl2 solution, and then impregnated at 70°C for 12 h using an equal volume impregnation method. Ammonia water (AR, 25-28 wt%, Shanghai Aladdin Biochemical Technology Co., Ltd.) was then added, and the ratio of the volume of ammonia water to the volume of the 0.1 mol / L ZrOCl2 solution was 1:1. After continuing to impregnate at 70°C for 12 h, the mixture was filtered, washed with deionized water, and dried at 60°C for 12 h to obtain a zirconium hydroxide modified NaA molecular sieve, which was recorded as Zr(OH)4 / ZrA molecular sieve.

[0100] The sulfate ion adsorption performance of Zr(OH)4 / ZrA molecular sieve prepared in Example 4 was tested. The test solution was a sodium sulfate aqueous solution, 200 mL of sodium sulfate aqueous solution, and the amount of zirconium hydroxide modified NaA molecular sieve added was 1 g. The test results showed that at pH = 4 and room temperature, sulfate (SO4 2- ) Under the condition of initial concentration of 500mg / L, adsorption for 120min, SO4 2- The adsorption rate is 65%.

[0101] Comparative Example 1

[0102] (1) Calcination and activation: same as step (1) in Example 1;

[0103] (2) Material addition: kaolin, sodium hydroxide, sodium aluminate and deionized water were mixed and stirred for 1 h in a certain molar ratio to obtain an initial solution, the molar ratio of which was SiO2:Al2O3:Na2O:H2O=2:1:2.8:224;

[0104] (3) Static aging: The initial solution was aged at 60°C for 2 h to obtain a precursor solution;

[0105] (4) Dynamic crystallization: Place all the precursor liquid materials in a reactor lined with polytetrafluoroethylene, then place the reactor in a magnetic stirring oil bath, rotate the shaft at a speed of 20 r / min, and perform dynamic hydrothermal crystallization at 95°C for 2 h; add deionized water to the crystallized product and wash it, repeat this process until the system becomes neutral, and then dry it at 60°C for 6 h to obtain NaA molecular sieve;

[0106] (5) NH4 + Ion exchange: 5 g of NaA molecular sieve was mixed with 300 mL of 0.1 mol / L ammonium chloride aqueous solution, heated to 60 °C in a constant temperature water bath and ion exchanged for 4 h to obtain a mixed solution of NH4A molecular sieve;

[0107] (6) Adding zirconium: add 10 mL of 0.1 mol / L ammonium fluorozirconate solution to the mixed solution of NH4A molecular sieve, heat to 70°C in a constant temperature water bath and react for 2 h, then filter and wash to obtain NH4A molecular sieve doped with zirconium;

[0108] (7) Zr 4+ Ion exchange: 5 g of NH4A molecular sieve doped with zirconium was mixed with 400 mL of 0.1 mol / L zirconium oxychloride aqueous solution, heated to 60 ° C in a constant temperature water bath and ion exchanged for 4 h, then filtered, washed and dried to obtain ZrA molecular sieve;

[0109] (8) Loading zirconium hydroxide active component: The ZrA molecular sieve was uniformly mixed with a 0.1 mol / L ZrOCl2 solution, and then impregnated at 60°C for 12 h using an equal volume impregnation method. Ammonia water (AR, 25-28 wt%, Shanghai Aladdin Biochemical Technology Co., Ltd.) was then added, and the ratio of the volume of ammonia water to the volume of the 0.1 mol / L ZrOCl2 solution was 1:1. After continuing to impregnate at 60°C for 12 h, the mixture was filtered, washed with deionized water, and dried at 60°C for 12 h to obtain a zirconium hydroxide modified NaA molecular sieve.

[0110] The sulfate ion adsorption performance of the zirconium hydroxide modified NaA molecular sieve prepared in Comparative Example 1 was tested. The test solution was a sodium sulfate aqueous solution, 200 mL of the sodium sulfate aqueous solution, and the amount of the zirconium hydroxide modified NaA molecular sieve added was 1 g. The test results showed that at pH = 3 and room temperature, sulfate (SO4 2- ) Under the condition of initial concentration of 500 mg / L, adsorption lasted for 120 min and the adsorption rate was 50%. Under this adsorption condition, the adsorption capacity was measured to be 71.24 mg / g.

[0111] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing zirconium hydroxide modified NaA molecular sieve, characterized in that: The following steps are involved: The gangue is calcined and activated to obtain metakaolin; the calcination and activation temperature is 750~900℃, the time is 2~4h, and the calcination and activation is carried out in an air atmosphere; The metakaolin is mixed with sodium hydroxide, an aluminum source, a zirconium source and water to obtain an initial solution; the aluminum source is sodium aluminate and / or aluminum nitrate; the metakaolin is calculated as SiO2 and Al2O3, the sodium hydroxide is calculated as Na2O, the aluminum source is calculated as Al2O3, the molar ratio of SiO2, Al2O3, Na2O and water in the initial solution is (1.3-2.4):1:(1.6-6):(130-300), and the concentration of the zirconium source in the initial solution is 0.01-0.2 mol / L; Aging the initial solution to obtain a precursor solution; the aging temperature is 40-70° C., the time is 0-4 hours, and the time is not 0; The precursor solution is subjected to hydrothermal crystallization to obtain a zirconium-modified NaA molecular sieve; The zirconium-modified NaA molecular sieve is successively subjected to NH4 + Ion exchange and Zr 4+ Ion exchange to obtain ZrA molecular sieve; After the ZrA molecular sieve is impregnated with a soluble zirconium salt solution, it is mixed with an alkali solution to undergo a precipitation reaction, thereby obtaining the zirconium hydroxide-modified NaA molecular sieve.

2. The preparation method according to claim 1, characterized in that: The zirconium source includes zirconium oxychloride and / or zirconium nitrate.

3. The preparation method according to claim 1, characterized in that: The temperature of the hydrothermal crystallization is 80-100° C., the time is 0-8 hours, and the time is not 0.

4. The preparation method according to claim 1, characterized in that: The NH4 + The ion exchange is carried out in a soluble ammonium salt solution containing NH4 + The concentration of NH4 is 0.1~0.2mol / L; + The temperature of ion exchange is 50~70℃ and the time is 2~6h.

5. The preparation method according to claim 1, characterized in that: The Zr 4+ The ion exchange is carried out in a soluble zirconium salt solution, wherein Zr 4+ The concentration of Zr is 0.1~0.2mol / L; 4+ The temperature of ion exchange is 50~70℃ and the time is 2~6h.

6. The preparation method according to claim 1, characterized in that: The soluble zirconium salt solution contains Zr 4+ The concentration is 0.1-0.2 mol / L, and the impregnation is equal volume impregnation; the temperature of the precipitation reaction is 30-70°C, and the time is 6-12h.

7. The zirconium hydroxide modified NaA molecular sieve prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the zirconium hydroxide modified NaA molecular sieve according to claim 7 in adsorbing sulfate ions in wastewater.

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