A zeolite molecular sieve for removing hexavalent chromium from wastewater and a preparation method thereof
Zeolite molecular sieves were prepared by hydrothermal synthesis, which solved the problem of complex and energy-intensive molecular sieve synthesis, and achieved simplified operation and efficient adsorption of hexavalent chromium, making it suitable for industrial applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JINGGANGSHAN UNIVERSITY
- Filing Date
- 2024-04-19
- Publication Date
- 2026-06-26
AI Technical Summary
Existing molecular sieve synthesis technologies are characterized by complex processes, high energy consumption, and inconvenient operation. Furthermore, existing molecular sieves have insufficient adsorption capacity for hexavalent chromium.
Zeolite molecular sieves were prepared by hydrothermal synthesis using sodium silicate nonahydrate, sodium aluminate, TMABr, basic activator, and ethanol as raw materials, which simplifies the operation steps and improves the adsorption performance.
The preparation process is simple, safe and easy to implement, with fast crystallization speed, making it suitable for industrial production. Furthermore, the molecular sieve exhibits excellent adsorption performance for hexavalent chromium, is low in cost, and has wide applicability.
Smart Images
Figure CN118343780B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of environmental engineering water pollution protection technology, and in particular to a zeolite molecular sieve for removing hexavalent chromium from wastewater and its preparation method. Background Technology
[0002] With rapid economic development and an increasing number of manufacturing enterprises, factories are discharging large amounts of untreated wastewater, leading to excessive levels of heavy metals in water bodies. There are two main methods for removing hexavalent chromium from wastewater: adsorption and chemical reduction. Compared to chemical reduction, adsorption is more effective and has lower reaction requirements, making it a promising method with significant practical application value, and it has received widespread attention in recent years.
[0003] Currently, the method of removing hexavalent chromium using molecular sieve adsorption is widely adopted by researchers. However, its preparation process is complex, requires high temperatures, and is time-consuming. Therefore, simplifying the preparation method of molecular sieves and enhancing their adsorption capacity for hexavalent chromium is a pressing issue. There is currently limited research on the fabrication of molecular sieves with good hexavalent chromium adsorption capabilities; thus, a simple and efficient molecular sieve preparation process is urgently needed. Summary of the Invention
[0004] The purpose of this application is to propose a zeolite molecular sieve for removing hexavalent chromium from wastewater and its preparation method, aiming to solve the problems of complex process flow, huge energy consumption and inconvenient operation of existing molecular sieve synthesis technology.
[0005] On the one hand, this application proposes a method for preparing zeolite molecular sieves for removing hexavalent chromium from wastewater, characterized in that the preparation method uses sodium silicate nonahydrate, sodium aluminate, TMABr, alkaline activator, and ethanol as raw materials, and obtains the molecular sieve by hydrothermal synthesis.
[0006] In some embodiments, the silicon-to-aluminum ratio of the raw materials is 1.7-1.8:1, and by mass percentage, the content of sodium silicate nonahydrate is 30-35%, the content of sodium aluminate is 5-6%, the content of TMABr is 7-9%, the content of ethanol is 9-10%, and the remainder is an alkaline activator.
[0007] In some embodiments, the alkaline activator is at least one of NaOH and TMAOH.
[0008] In some embodiments, the preparation method includes:
[0009] Mix the solution and stir: Put all the raw materials into a PTFE-lined stainless steel autoclave, then put the PTFE-lined stainless steel autoclave into an ultrasonic cleaner and stir it ultrasonically, while shaking it slowly during the stirring process.
[0010] Synthesis reaction: After stirring, tighten the PTFE-lined stainless steel autoclave and place it in a constant temperature chamber for constant temperature reaction.
[0011] Sample removal: After the constant temperature is completed, remove the PTFE-lined stainless steel autoclave, wait for it to cool, rotate the lid to remove the white liner, and dry it to obtain the molecular sieve.
[0012] In some embodiments, in the step of placing a polytetrafluoroethylene-lined stainless steel autoclave into an ultrasonic cleaner for ultrasonic stirring:
[0013] The ultrasonic stirring time is 5-20 minutes.
[0014] In some embodiments, after the stirring is completed, the polytetrafluoroethylene-lined stainless steel autoclave is tightened, and the polytetrafluoroethylene-lined stainless steel autoclave is placed in a constant temperature chamber for constant temperature reaction:
[0015] Set the temperature of the constant temperature chamber to 120-150℃. Once the temperature of the constant temperature chamber reaches 120-150℃, place the PTFE-lined stainless steel autoclave into the constant temperature chamber.
[0016] In some embodiments, the isothermal reaction time is 20-30 hours.
[0017] In some embodiments, the silicon-to-aluminum ratio of the raw materials is 1.77:1, and by mass percentage, the content of sodium silicate nonahydrate is 32.84%, sodium aluminate is 5.57%, TMABr is 8.09%, sodium hydroxide is 1.17%, TMAOH is 42.94%, and ethanol is 9.39%.
[0018] In some embodiments, the silicon-to-aluminum ratio of the raw materials is 1.77:1, and by mass percentage, the content of sodium silicate nonahydrate is 33.23%, the content of sodium aluminate is 5.64%, the content of TMABr is 8.19%, the content of TMAOH is 43.44%, and the content of ethanol is 9.50%.
[0019] On the other hand, this application also proposes a zeolite molecular sieve for removing hexavalent chromium from wastewater, which is obtained by the above-mentioned preparation method of a zeolite molecular sieve for removing hexavalent chromium from wastewater.
[0020] Compared with the prior art, this application has the following advantages:
[0021] 1. The preparation process proposed in this application is simple, easy to operate, and safe.
[0022] 2. The preparation method proposed in this application is carried out in a hydrothermal system. Since water can be used as a solvent to increase the solubility and reactivity of the reactants, the initial gel dissolves and rearranges in the system, thereby increasing the crystallization rate and nucleation rate.
[0023] 3. It is applicable to the vast majority of kaolin mines, and production can be adjusted as needed to produce other types of molecular sieves. It is simple to operate and suitable for mechanized and automated production, providing a great advantage for industrial production.
[0024] 4. The raw materials used in this application are inexpensive, and the molecular sieves prepared have excellent adsorption performance, giving them a significant competitive advantage in the market.
[0025] 5. The molecular sieves obtained by the preparation method proposed in this application have advantages such as high crystallization degree, stable active sites, good reproducibility, easy control of orientation crystals, and easy control of crystallization product morphology and particle size, which are conducive to industrial scale-up production and development in the direction of sustainable development.
[0026] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by means of embodiments thereof. Attached Figure Description
[0027] Figure 1 A schematic diagram of the hexavalent chromium adsorption capacity of sample materials A, B, and C is shown.
[0028] Figure 2 The SEM images of sample material A (left) and sample material B (right) without adsorbed Cr(VI) are shown.
[0029] Figure 3 The SEM images of sample material A (left) and sample material B (right) after adsorption of Cr(VI) are shown.
[0030] Figure 4 The XRD analysis results of sample material A and sample material B after adsorption of Cr(VI) are shown. Detailed Implementation
[0031] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate several embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.
[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.
[0033] In this paper, the term "hydrothermal synthesis" refers to a method of synthesis using chemical reactions of substances in aqueous solutions at temperatures of 90–1000 °C and pressures of 1 MPa–1 GPa. Under subcritical and supercritical hydrothermal conditions, the reaction occurs at the molecular level, resulting in increased reactivity; therefore, hydrothermal reactions can replace certain high-temperature solid-state reactions. Furthermore, because the homogeneous and heterogeneous nucleation mechanisms of hydrothermal reactions differ from the diffusion mechanisms of solid-state reactions, it is possible to create novel compounds and materials that cannot be prepared by other methods.
[0034] Example 1
[0035] The silicon-to-aluminum ratio of the raw materials is controlled at 1.77:1. By mass percentage, the content of sodium silicate nonahydrate is 32.84%, sodium aluminate is 5.57%, TMABr is 8.09%, sodium hydroxide is 1.17%, TMAOH is 42.94%, and ethanol is 9.39%. The sum of the contents of the above-mentioned drugs is 100%.
[0036] Step 1: Mix and stir the solution: Place all the medicines into a PTFE-lined stainless steel autoclave, then place the autoclave into a large beaker. Place the large beaker into an ultrasonic cleaner and stir ultrasonically for 10 minutes, gently shaking it during the process.
[0037] Step 2: Synthesis reaction: After stirring, tighten the PTFE-lined stainless steel autoclave, set the constant temperature chamber to 140℃, and when the constant temperature chamber reaches 140℃, place the stainless steel autoclave directly into the constant temperature chamber for 24 hours.
[0038] Step 3: Sample Removal: After 24 hours, turn off the power at the lower left side of the thermostat, turn on the thermostat, remove the stainless steel autoclave, and after cooling, rotate the lid to remove the white liner. Place it in another oven set to 110℃ to dry, and obtain sample material A.
[0039] Example 2
[0040] The silicon-to-aluminum ratio of the raw materials is controlled at 1.77:1. By mass percentage, the content of sodium silicate nonahydrate is 33.23%, sodium aluminate is 5.64%, TMABr is 8.19%, TMAOH is 43.44%, and ethanol is 9.50%. The sum of the contents of the above-mentioned drugs is 100%.
[0041] Step 1: Mix and stir the solution: Place all the medicines into a PTFE-lined stainless steel autoclave, then place the autoclave into a large beaker. Place the large beaker into an ultrasonic cleaner and stir ultrasonically for 10 minutes, gently shaking it during the process.
[0042] Step 2: Synthesis reaction: After stirring, tighten the PTFE-lined stainless steel autoclave, set the constant temperature chamber to 140℃, and when the constant temperature chamber reaches 140℃, place the stainless steel autoclave directly into the constant temperature chamber for 24 hours.
[0043] Step 3: Sample Removal: After 24 hours, turn off the power at the lower left side of the thermostat, turn on the thermostat, remove the stainless steel autoclave, and after cooling, rotate the lid to remove the white liner. Place it in another oven set to 110℃ to dry, and obtain sample material B.
[0044] Example 3
[0045] The silicon-to-aluminum ratio of the raw materials is controlled at 1.77:1. By mass percentage, the content of sodium silicate nonahydrate is 58.75%, sodium aluminate is 9.97%, TMABr is 14.48%, and ethanol is 16.80%. The sum of the contents of the above-mentioned drugs is 100%.
[0046] Step 1: Mix and stir the solution: Place all the medicines into a PTFE-lined stainless steel autoclave, then place the autoclave into a large beaker. Place the large beaker into an ultrasonic cleaner and stir ultrasonically for 10 minutes, gently shaking it during the process.
[0047] Step 2: Synthesis reaction: After stirring, tighten the PTFE-lined stainless steel autoclave, set the constant temperature chamber to 140℃, and when the constant temperature chamber reaches 140℃, place the stainless steel autoclave directly into the constant temperature chamber for 24 hours.
[0048] Step 3: Sample Removal: After 24 hours, turn off the power at the lower left side of the thermostat, turn on the thermostat, remove the stainless steel autoclave, and after cooling, rotate the lid to remove the white liner. Place it in another oven set to 110℃ to dry, and obtain sample material C.
[0049] Experimental Example
[0050] Step 1: Weigh 0.1g each of sample materials A, B and C obtained from Example 1, Example 2 and Example 3 respectively, and mix them with 40mL of 100mg / L Cr(VI) at pH 3 into centrifuge tubes.
[0051] Step 2: Place each centrifuge tube into the shaker, turn on the power to the shaker, set the temperature to 25°C, the rotation speed to 180 r / min, and the time to 14 h.
[0052] Step 3: After the shaker reaches the set time, remove the centrifuge tubes, turn off the shaker power, put the centrifuge tubes in the refrigerator, and then use the diphenylcarbazide spectrophotometric method to determine the hexavalent chromium content in the solution to calculate the adsorption capacity.
[0053] Please see Figure 1 The diagram shows the hexavalent chromium adsorption capacity of samples A, B, and C. Figure 1 It can be seen that the adsorption capacities of sample materials A, B, and C are 17.11 mg / g, 12.23 mg / g, and 5.19 mg / g, respectively. In other words, material A has a better adsorption capacity for hexavalent chromium than materials B and C.
[0054] Scanning electron microscopy (SEM) was used to analyze the surface morphology of the prepared unadsorbed Cr(VI) materials A and B. Please refer to [link to SEM]. Figure 2 The image shows SEM images of sample material A (left) and sample material B (right) without adsorbed Cr(VI). Figure 2 It can be seen that the sample materials A and B obtained by the preparation method proposed in this application have obvious pore structure characteristics.
[0055] Materials A and B after Cr(VI) adsorption were analyzed using scanning electron microscopy (SEM) to determine their surface morphology. Please refer to [link to SEM]. Figure 3 The image shows SEM images of sample material A (left) and sample material B (right) after adsorption of Cr(VI). Figure 3 It can be seen that the prepared sample has obvious porous structure characteristics, and its surface is more dense than that of materials A and B without Cr(VI) adsorption, which may be due to the adsorption of a large amount of Cr(VI) on the material surface.
[0056] In addition, XRD analysis was performed on Yangping materials A and B after Cr(VI) adsorption. Please refer to [link to relevant documentation]. Figure 4 The figure shows the XRD analysis results of sample material A and sample material B after adsorbing Cr(VI). As can be seen from the figure, both materials A and B have obvious molecular sieve structures. After adsorbing Cr(VI), Cr(VI) in material A appears in the form of Na2Cr2O7; while after adsorbing Cr(VI) in material B, Cr(VI) appears in the form of HCrO2.
[0057] Comparative Example 1
[0058] The technical solution of Chinese Patent No. CN110639481A, entitled "A Method for Preparing Polypyrrole and Mesoporous Molecular Sieves Composite Materials", is used as the first comparative example of this application. It uses a muffle furnace to prepare molecular sieves, and the calcination temperature reaches 550°C and lasts for 5 hours. Therefore, the preparation cost is very high and a long cooling time is also required.
[0059] Comparative Example 2
[0060] The technical solution of Chinese Patent No. CN108264122B, entitled "A Method for Preparing Hexavalent Chromium Adsorption and Reduction Material", is used as Comparative Example 2 of this application. The method requires a reaction time of 48-60 hours at 140-180°C in a reactor, which is far longer than the reaction time of this application. In addition, it also requires the introduction of argon gas for deoxygenation and sealing for preparation, making the cost and steps more complicated than those of this application.
[0061] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.
Claims
1. A method for preparing a zeolite molecular sieve for removing hexavalent chromium from wastewater, characterized in that the preparation method uses sodium silicate nonahydrate, sodium aluminate, TMABr, basic activator, and ethanol as raw materials, and obtains the molecular sieve by hydrothermal synthesis. The silicon-to-aluminum ratio of the raw material is 1.
7. The ratio is 1.8:1, and the content of sodium silicate nonahydrate is 30% by mass percentage. 35%, sodium aluminate content is 5 6%, TMABr content is 7 9%, ethanol content is 9 10%, the remainder being alkaline activators; The alkaline activator is NaOH and TMAOH.
2. The method for preparing a zeolite molecular sieve for removing hexavalent chromium from wastewater according to claim 1, characterized in that, The preparation method includes: mixing and stirring the solution: placing all the raw materials into a polytetrafluoroethylene-lined stainless steel autoclave, then placing the polytetrafluoroethylene-lined stainless steel autoclave into an ultrasonic cleaner for ultrasonic stirring, and slowly shaking it during the stirring process; synthesis reaction: after stirring, tightening the polytetrafluoroethylene-lined stainless steel autoclave, and placing the polytetrafluoroethylene-lined stainless steel autoclave into a constant temperature chamber for constant temperature reaction; sample removal: after the constant temperature is completed, removing the polytetrafluoroethylene-lined stainless steel autoclave, and after cooling, rotating the lid to remove the white liner, and drying it to obtain a molecular sieve.
3. The method for preparing a zeolite molecular sieve for removing hexavalent chromium from wastewater according to claim 2, characterized in that, In the step of placing the PTFE-lined stainless steel autoclave into the ultrasonic cleaner for ultrasonic stirring: the ultrasonic stirring time is 5 minutes. 20 minutes.
4. The method for preparing a zeolite molecular sieve for removing hexavalent chromium from wastewater according to claim 2, characterized in that, After the stirring is complete, tighten the PTFE-lined stainless steel autoclave and place it in a constant temperature chamber for the constant temperature reaction. Set the temperature of the constant temperature chamber to 120°C. 150℃, wait for the constant temperature chamber to rise to 120℃ At 150℃, place the PTFE-lined stainless steel autoclave into a constant temperature chamber.
5. The method for preparing a zeolite molecular sieve for removing hexavalent chromium from wastewater according to claim 4, characterized in that, The isothermal reaction time is 20 minutes. 30 hours.
6. The method for preparing a zeolite molecular sieve for removing hexavalent chromium from wastewater according to claim 1, characterized in that, The raw materials have a silicon-to-aluminum ratio of 1.77:1, and by mass percentage, the content of sodium silicate nonahydrate is 32.84%, sodium aluminate is 5.57%, TMABr is 8.09%, sodium hydroxide is 1.17%, TMAOH is 42.94%, and ethanol is 9.39%.
7. A zeolite molecular sieve for removing hexavalent chromium from wastewater, characterized in that, According to claim 1 The zeolite molecular sieve for removing hexavalent chromium from wastewater is obtained by any one of the methods described in claim 6.