Method for deeply removing cristobalite in bentonite by using nanoscale filtering membrane
By deeply removing quartz from bentonite using a nanoscale filtration membrane, the problem of difficult removal of quartz from bentonite is solved, and high-purity montmorillonite is prepared, which is suitable for the pharmaceutical and cosmetic fields.
Patent Information
- Application Number
- CN202511001182.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-21
- Publication Date
- 2025-12-12
AI Technical Summary
Quartz in bentonite is difficult to remove, affecting its performance and potentially causing cancer. Existing technologies are insufficient to effectively separate and purify high-purity, high-quality montmorillonite.
The deep removal of cristobalite from bentonite using nanoscale filtration membranes includes preliminary purification to remove large particle impurities, sodium treatment to improve expansion and dispersibility, freeze-cycle treatment to remove interlayer forces, and micron-level filtration and pressurized ultrafiltration to deeply remove submicron-sized cristobalite.
The preparation of high-purity montmorillonite has been achieved, which improves the expansion properties of bentonite. The process is simple, low-cost, and produces no byproducts, making it suitable for the pharmaceutical and cosmetic fields.
Smart Images
Figure CN121107428A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of bentonite purification, and particularly relates to a method for deeply removing cristobalite in bentonite by using nanoscale filter membrane. BACKGROUND
[0002] With the development of nanotechnology, montmorillonite is paid more attention as a drug delivery medium. According to the type and content of exchangeable cations, montmorillonite can be divided into calcium-based montmorillonite and sodium-based montmorillonite, and the latter has better plasticity, swelling, suspensibility, adsorbability and ion exchange property than the former.
[0003] Bentonite is a natural adsorptive clay mineral, and its medicinal value is recorded in Tang Dynasty 'Bencao Gangmu Shiyi'. The main component of bentonite, montmorillonite, has superior performance, so that bentonite is widely used in medical applications. The strong adsorption of bentonite can detoxify some toxic substances, and can be widely used for stopping diarrhea and treating digestive tract ulcers. However, bentonite is usually associated with various impurities, which affects its performance, and quartz and cristobalite in bentonite are difficult to remove and can cause cancer in human body. Therefore, it is a technical problem to be solved to separate and purify bentonite to obtain high-purity and high-quality montmorillonite, so that it is safer and more effective. SUMMARY
[0004] In view of the above problems of the prior art, the present application provides a method for deeply removing cristobalite in bentonite by using nanoscale filter membrane. The method comprises the following steps: removing large particle impurities in bentonite by simple preliminary purification, improving the swelling and dispersibility of bentonite by sodium treatment, weakening the interlayer interaction of bentonite by freeze-thaw treatment, effectively separating montmorillonite from cristobalite by using nanoscale filter membrane, and deeply removing submicron cristobalite by using a pressurized ultrafiltration device to obtain high-purity and high-quality montmorillonite.
[0005] To achieve the above-mentioned purpose, the specific technical scheme of the present application is as follows:
[0006] The present application provides a method for deeply removing cristobalite in bentonite by using nanoscale filter membrane, which comprises the following steps:
[0007] S1, dispersing calcium-based bentonite in water in a certain proportion, adding an appropriate amount of dispersant, and then stirring, standing, centrifuging and drying to obtain preliminarily purified bentonite;
[0008] S2, mixing the preliminarily purified bentonite with sodium salt in water to perform ion exchange modification to obtain sodium-based bentonite;
[0009] S3, configuring the sodium-based bentonite into a suspension, and obtaining pre-hydrated bentonite after pre-hydration;
[0010] S4, the pre-hydrated bentonite is peeled to prepare a bentonite nanosheet suspension with 1-5 layers;
[0011] S5, the bentonite nanosheet suspension is filtered through a microporous filter membrane to preliminarily remove micro-sized cristobalite;
[0012] S6, after the bentonite nanosheet permeate liquid after the preliminary removal of micro-sized cristobalite is filtered through an ultrafiltration membrane, high-purity montmorillonite is obtained by drying.
[0013] Further, in step S1, the mass ratio of the calcium-based bentonite to water is 1: (5-20).
[0014] Further, in step S1, the amount of the dispersant is 1%-6% of the mass of the calcium-based bentonite.
[0015] Further, in step S1, the dispersant is sodium hexametaphosphate and / or sodium pyrophosphate.
[0016] Further, in step S1, the stirring time is 1-6 h.
[0017] Further, in step S1, the standing time is 12-24 h.
[0018] Further, in step S1, the centrifugal speed is 3000 r / min, and the centrifugal time is 2 min.
[0019] Further, in step S1, the drying temperature is 105 ℃-110 ℃, and the drying time is 12-24 h.
[0020] Further, in step S1, after adding an appropriate amount of dispersant, a sodium hydroxide solution with a concentration of 0.1-1 mol / L is added to adjust the pH value to 8-10, and then stirring, standing, centrifugation, and drying are performed to obtain the preliminarily purified bentonite.
[0021] Further, in step S2, the mass ratio of the preliminarily purified bentonite to water is 1: (10-20).
[0022] Further, in step S2, the amount of the sodium salt is 2%-10% of the mass of the preliminarily purified bentonite.
[0023] Further, in step S2, the sodium salt includes but is not limited to at least one of sodium chloride, sodium pyrophosphate, and sodium carbonate.
[0024] Further, in step S2, the temperature for mixing for ion exchange modification is 40-80 ℃, and the time is 1-6 h.
[0025] Further, in step S2, the number of times of ion exchange modification is 1-5.
[0026] Further, the specific operation of step S3 is as follows: the sodium-based bentonite is configured into a suspension with a concentration of 1wt%-5wt%, stirred for 12-24 h, and then subjected to ultrasonic treatment under an ultrasonic intensity of 20 kHz for 15-60 min to obtain the pre-hydrated bentonite.
[0027] Further, the specific operation of step S4 is as follows: the pre-hydrated bentonite is subjected to cyclic freezing treatment, and the thawed bentonite is subjected to ultrasonic treatment and then centrifugal treatment to obtain a bentonite nanosheet suspension with 1-5 layers.
[0028] Further, the number of times of cyclic freezing is 1-2 times.
[0029] Further, the ultrasonic treatment has an intensity of 20-30 kHz and a time of 10-30 min.
[0030] Further, in step S5, the bentonite nanosheet suspension is subjected to vacuum suction filtration through a mixed cellulose ester (MCE) membrane with a pore size of 0.45 μm to preliminarily remove the micron-sized cristobalite.
[0031] Further, the vacuum suction filtration is performed 1-5 times.
[0032] Further, in step S6, the bentonite nanosheet permeate liquid after the preliminary removal of the micron-sized cristobalite is subjected to pressure filtration through an ultrafiltration membrane with a pore size of 100 kDa (corresponding to a pore size of 10 nm) of an ultrafiltration device, and then vacuum dried to obtain high-purity montmorillonite.
[0033] Further, the pressure filtration is repeated 3 times to obtain the high-purity montmorillonite.
[0034] Further, the pressure of the pressure filtration is 0.2-0.5 MPa.
[0035] Further, after the filtration through the ultrafiltration membrane, the filtered liquid is subjected to rotary evaporation to a solid content of 50% or more, an appropriate amount of anhydrous ethanol is added to prevent the nanosheets from aggregating, ultrasonic dispersion is performed for 10 min, and then drying is performed to obtain the high-purity montmorillonite from which the cristobalite has been removed.
[0036] The application also provides high-purity montmorillonite prepared by the method.
[0037] The application also provides application of the high-purity montmorillonite in the fields of medicine and cosmetics.
[0038] Compared with the prior art, the application has the following advantages:
[0039] (1) The present application removes large particle impurities in advance by preliminary wet purification, greatly improves the swelling performance of bentonite, and lays a foundation for subsequent steps.
[0040] (2) The present application increases the hydration swelling property by introducing sodium ions with excellent hydration capacity through ion exchange modification, and makes part of the bentonite directly exfoliate into nanosheets after pre-hydration treatment.
[0041] (3) The present application exfoliates bentonite into single-layer or few-layer nanosheets by the method of cyclic freezing + ultrasonic treatment + centrifugation, so as to completely separate sub-micron quartz and nanometer montmorillonite.
[0042] (4) The present application removes sub-micron quartz by multiple vacuum filtration through a micrometer filter membrane, and performs secondary pressure ultrafiltration on the solution after vacuum filtration by using a nanometer filter membrane, so as to obtain high-purity montmorillonite from which quartz is removed.
[0043] (5) The present application has simple process and low production cost, no by-products are generated in the whole process, and the obtained high-purity montmorillonite can be directly used in the production of medical and cosmetic fields. BRIEF DESCRIPTION OF DRAWINGS
[0044] Figure 1 XRD pattern of calcium-based bentonite in Example 1;
[0045] Figure 2 XRD pattern of calcium-based bentonite subjected to preliminary wet purification in Example 1;
[0046] Figure 3 XRD pattern of sodium ion-modified bentonite in Example 1;
[0047] Figure 4 XRD pattern of high-purity montmorillonite from which quartz is removed in Example 1;
[0048] Figure 5 XRD pattern of the dried sample of the exfoliated montmorillonite nanosheet suspension in Example 2;
[0049] Figure 6 XRD pattern of high-purity montmorillonite from which quartz is removed in Example 2. DETAILED DESCRIPTION
[0050] In order for those skilled in the art to better understand the present application, the technical solutions of the present application will be described clearly and completely below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.
[0051] This invention provides a method for deep removal of quartz from bentonite using a nanoscale filtration membrane, comprising the following steps:
[0052] S1. Disperse calcium-based bentonite in water at a mass ratio of 1:(5~20), add 1%~6% of the mass of calcium-based bentonite as a dispersant, stir for 1~6 h, let stand for 12~24 h, centrifuge at 3000 r / min for 2 min, and dry the supernatant at 105 ℃~110 ℃ for 12~24 h to obtain preliminarily purified bentonite;
[0053] S2. The preliminarily purified bentonite and sodium salt are mixed in water at a mass ratio of 100:(2~10), and ion exchange modification is carried out at 40~80℃ for 1~6 h to obtain sodium-based bentonite; wherein, the mass ratio of the preliminarily purified bentonite to water is 1:(10~20).
[0054] S3. Prepare a suspension of sodium-based bentonite with a concentration of 1wt%~5wt%, stir for 12~24 h, and then sonicate it at an ultrasonic intensity of 20 kHz for 15~60 min to obtain prehydrated bentonite.
[0055] S4. The prehydrated bentonite is subjected to cyclic freezing 1-2 times. The thawed bentonite is then subjected to ultrasonic treatment and centrifugation to obtain a bentonite nanosheet suspension with 1-5 layers.
[0056] S5. The bentonite nanosheet suspension was initially removed by vacuum filtration through a mixed cellulose ester (MCE) membrane with a pore size of 0.45 μm.
[0057] S6. The bentonite nanosheet permeate after the initial removal of micron-sized cristobalite is passed through an ultrafiltration device through a 100kDa (corresponding to 10 nm pore size) ultrafiltration membrane and then pressurized at a pressure of 0.2~0.5 MPa.
[0058] S7. After filtration through an ultrafiltration membrane, the following steps are also included: rotary evaporation of the filtered liquid until the solid content is above 50%, addition of an appropriate amount of anhydrous ethanol to prevent nanosheet aggregation, ultrasonic dispersion for 10 min, and vacuum drying to obtain high-purity montmorillonite with cristobalite removed.
[0059] In some examples, the dispersant is sodium hexametaphosphate and / or sodium pyrophosphate.
[0060] In some examples, after adding a dispersant, a sodium hydroxide solution with a concentration of 0.1~1 mol / L is added to adjust the pH value to 8~10, followed by stirring, standing, centrifugation, and drying to obtain preliminarily purified bentonite.
[0061] In some examples, the sodium salt includes, but is not limited to, at least one of sodium chloride, sodium pyrophosphate, sodium carbonate.
[0062] In some examples, the ion exchange modification is performed 1-5 times.
[0063] In some examples, the ultrasonic treatment is performed at a strength of 20-30 kHz for 10-30 min.
[0064] In some examples, the vacuum filtration is performed 1-5 times.
[0065] Example 1
[0066] A high-purity montmorillonite with paraspodumene removed is prepared according to the following method:
[0067] 1) 10 g of calcium-based bentonite is dispersed in 120 mL of deionized water, 0.1 g of sodium hexametaphosphate is added, stirred for 2 h, and left to stand for 12 h. The supernatant is centrifuged at 3000 r / min for 2 min, and the bottom precipitate is discarded. The supernatant is dried to obtain a calcium-based bentonite purified by a preliminary wet method.
[0068] 2) 10 g of the calcium-based bentonite purified by the preliminary wet method is dispersed in 120 mL of deionized water, 0.2 g of sodium carbonate is added, and stirred at 40 ℃ for 3 h. The mixture is centrifuged at 3000 r / min for 2 min, and the bottom precipitate is discarded. The supernatant is dried to obtain sodium ion-modified bentonite.
[0069] 3) The sodium ion-modified bentonite is configured into a 1 wt% suspension, stirred for 12 h, and ultrasonically treated at a strength of 20 kHz for 30 min to obtain pre-hydrated bentonite.
[0070] 4) The pre-hydrated bentonite is frozen at -20 ℃ for 24 h, and thawed for 2 cycles. The thawed bentonite solution is ultrasonically treated at a strength of 20 kHz for 20 min, and centrifuged at 10000 r / min for 30 min to obtain a suspension of exfoliated montmorillonite nanosheets.
[0071] 5) The suspension of exfoliated montmorillonite nanosheets is vacuum filtered through a mixed cellulose ester (MCE) membrane with a pore size of 0.45 μm. The permeate is transferred to a 100 kDa (about corresponding to a pore size of 10 nm) ultrafiltration membrane system for pressure filtration (pressure is 0.2 MPa). The ultrafiltration is repeated 3 times.
[0072] 6) The filtered liquid was rotary evaporated at 40 °C until the solid content was 50%, and 1% anhydrous ethanol was added to prevent the nanosheets from agglomerating. After ultrasonic dispersion for 10 min, the dispersion was poured into a freeze-drying pan, pre-frozen to -80 °C and then vacuum dried for 24 h to obtain high-purity montmorillonite with cristobalite removed.
[0073] Figure 1 The figure shows the XRD pattern of the calcium-based bentonite used in Example 1. As can be seen from the figure, the main components of the calcium-based bentonite are montmorillonite, cristobalite, quartz and dolomite; among them, the peak of cristobalite is relatively sharp, indicating that the content of cristobalite is high. Figure 2 The figure shows the XRD pattern of calcium-based bentonite preliminarily purified by wet process in Example 1. As can be seen from the figure, after preliminary wet purification, most of the impurities were removed and the content of montmorillonite increased, but it still contained a lot of quartz, which is difficult to remove. Figure 3 The figure shows the XRD pattern of sodium ion modified bentonite in Example 1. It can be seen from the figure that other impurities have been basically removed, but it is still difficult to remove cristobalite. Figure 4 The image shows the XRD pattern of high-purity montmorillonite obtained after removing cristobalite in Example 1. As can be seen from the image, all diffraction peaks of the high-purity montmorillonite obtained after vacuum filtration and pressure filtration are those of montmorillonite, indicating that the cristobalite was completely removed. These results demonstrate that the nanoscale filtration membrane provided by this invention can completely remove cristobalite and other associated impurities.
[0074] Example 2
[0075] A high-purity montmorillonite with cristobalite removed is prepared by the following method:
[0076] 1) Disperse 10 g of calcium-based bentonite in 120 mL of deionized water, add 0.1 g of sodium hexametaphosphate, stir for 4 h, let stand for 12 h, take the supernatant and centrifuge at 3000 r / min for 2 min, discard the bottom precipitate and take the supernatant and dry it to obtain the calcium-based bentonite preliminarily purified by wet method.
[0077] 2) Take 10 g of calcium-based bentonite that has been preliminarily purified by wet method and disperse it in 120 mL of deionized water. Add 0.2 g of sodium carbonate and stir at 40 ℃ for 6 h. Then, centrifuge at 3000 r / min for 2 min, discard the bottom precipitate, take the supernatant and dry it to obtain sodium ion modified bentonite.
[0078] 3) Sodium ion modified bentonite was prepared into a 1 wt% suspension, stirred for 12 h, and then sonicated at 20 kHz for 30 min to obtain prehydrated bentonite.
[0079] 4) The prehydrated bentonite was frozen at -20 ℃ for 24 h and thawed once. The thawed bentonite solution was sonicated at 20 kHz for 20 min and then centrifuged at 10000 r / min for 30 min to obtain the exfoliated montmorillonite nanosheet suspension.
[0080] 5) The sloughed montmorillonite nanosheet suspension was vacuum filtered through a mixed cellulose ester membrane with a pore size of 0.45 μm. The permeate was then transferred to a 100 kDa ultrafiltration membrane system for pressure filtration (pressure of 0.2 MPa). The ultrafiltration was repeated 3 times.
[0081] 6) The filtered liquid was rotary evaporated at 40 °C until the solid content was 50%, and 1% anhydrous ethanol was added to prevent the nanosheets from agglomerating. After ultrasonic dispersion for 10 min, the dispersion was poured into a freeze-drying pan, pre-frozen to -80 °C and then vacuum dried for 24 h to obtain high-purity montmorillonite with cristobalite removed.
[0082] Figure 5 The image shows the XRD pattern of the dried sample of the montmorillonite nanosheet suspension exfoliated in Example 2. As can be seen from the image, other impurities have been removed, but the peak of cristobalite still exists. Figure 6 The image shows the XRD pattern of high-purity montmorillonite obtained after removing cristobalite in Example 2. As can be seen from the image, all diffraction peaks of the high-purity montmorillonite obtained after vacuum filtration and pressure filtration are montmorillonite diffraction peaks, indicating that cristobalite was completely removed. These results demonstrate that the nanoscale filtration membrane provided by this invention can completely remove cristobalite and other associated impurities, obtaining high-purity montmorillonite.
[0083] Example 3
[0084] A high-purity montmorillonite with cristobalite removed is prepared by the following method:
[0085] 1) Disperse 10 g of calcium-based bentonite in 120 mL of deionized water, add 0.2 g of sodium hexametaphosphate, adjust the pH of the solution to 9-10 with sodium hydroxide at a concentration of 1 mol / L, stir for 1.5 h, let stand for 12 h, take the supernatant and centrifuge at 3000 r / min for 2 min, discard the bottom precipitate, take the supernatant and dry it to obtain the calcium-based bentonite preliminarily purified by wet method.
[0086] 2) Take 10 g of calcium-based bentonite that has been preliminarily purified by wet method and disperse it in 120 mL of deionized water. Add 0.5 g of sodium chloride and stir at 60 ℃ for 6 h. Centrifuge at 3000 r / min for 2 min, discard the bottom precipitate and take the supernatant to dry to obtain sodium ion modified bentonite.
[0087] 3) Sodium ion modified bentonite was prepared into a 2wt% suspension, stirred for 16 h, and then sonicated at 20 kHz for 30 min to obtain prehydrated bentonite.
[0088] 4) The prehydrated bentonite was frozen at -20 ℃ for 24 h and thawed twice. The thawed bentonite solution was sonicated at 20 kHz for 20 min and then centrifuged at 10000 r / min for 30 min to obtain the exfoliated montmorillonite nanosheet suspension.
[0089] 5) The sloughed montmorillonite nanosheet suspension was vacuum filtered through a mixed cellulose ester membrane with a pore size of 0.45 μm. The permeate was then transferred to a 100 kDa ultrafiltration membrane system for pressure filtration (pressure of 0.2 MPa). The ultrafiltration was repeated 3 times.
[0090] 6) The filtered liquid was rotary evaporated at 40 °C until the solid content was 50%, and 1% anhydrous ethanol was added to prevent the nanosheets from agglomerating. After ultrasonic dispersion for 10 min, the dispersion was poured into a freeze-drying pan, pre-frozen to -80 °C and then vacuum dried for 24 h to obtain high-purity montmorillonite with cristobalite removed.
[0091] Upon testing, the XRD pattern of the high-purity montmorillonite with cristobalite removed in Example 3 showed that all diffraction peaks belonged to montmorillonite, indicating that the use of a nanoscale filtration membrane can completely remove cristobalite and other associated impurities.
[0092] Example 4
[0093] A high-purity montmorillonite with cristobalite removed is prepared by the following method:
[0094] 1) Disperse 10 g of calcium-based bentonite in 200 mL of deionized water, add 0.1 g of sodium hexametaphosphate, adjust the pH of the solution to 9-10 with 1 mol / L sodium hydroxide, stir for 4 h, let stand for 12 h, take the supernatant and centrifuge at 3000 r / min for 2 min, discard the bottom precipitate, take the supernatant and dry it to obtain the calcium-based bentonite preliminarily purified by wet method.
[0095] 2) Take 10 g of calcium-based bentonite that has been preliminarily purified by wet method and disperse it in 200 mL of deionized water. Add 0.5 g of sodium pyrophosphate and stir at 70 °C for 3 h. Then, centrifuge at 3000 r / min for 2 min, discard the bottom precipitate, take the supernatant and dry it to obtain sodium ion modified bentonite.
[0096] 3) Sodium ion modified bentonite was prepared into a 3wt% suspension, stirred for 24 h, and then sonicated at 20 kHz for 30 min to obtain prehydrated bentonite.
[0097] 4) The prehydrated bentonite was frozen at -20 ℃ for 24 h and thawed once. The thawed bentonite solution was sonicated at 20 kHz for 20 min and then centrifuged at 10000 r / min for 30 min to obtain the exfoliated montmorillonite nanosheet suspension.
[0098] 5) The sloughed montmorillonite nanosheet suspension was vacuum filtered through a mixed cellulose ester membrane with a pore size of 0.45 μm. The permeate was then transferred to a 100 kDa ultrafiltration membrane system for pressure filtration (pressure of 0.2 MPa). The ultrafiltration was repeated 3 times.
[0099] 6) The filtered liquid was rotary evaporated at 40 °C until the solid content was 50%, and 1% anhydrous ethanol was added to prevent the nanosheets from agglomerating. After ultrasonic dispersion for 10 min, the dispersion was poured into a freeze-drying pan, pre-frozen to -80 °C and then vacuum dried for 24 h to obtain high-purity montmorillonite with cristobalite removed.
[0100] Upon testing, the XRD pattern of the high-purity montmorillonite with cristobalite removed in Example 4 showed that all diffraction peaks belonged to montmorillonite, indicating that the use of a nanoscale filtration membrane can completely remove cristobalite and other associated impurities.
[0101] Example 5
[0102] A high-purity montmorillonite with cristobalite removed is prepared by the following method:
[0103] 1) Disperse 10 g of calcium-based bentonite in 200 mL of deionized water, add 0.2 g of sodium hexametaphosphate, adjust the pH of the solution to 8-10 with 1 mol / L sodium hydroxide, stir for 2 h, let stand for 12 h, take the supernatant and centrifuge at 3000 r / min for 2 min, discard the bottom precipitate, take the supernatant and dry it to obtain the calcium-based bentonite preliminarily purified by wet method.
[0104] 2) Take 10 g of calcium-based bentonite that has been preliminarily purified by wet method and disperse it in 200 mL of deionized water. Add 0.5 g of sodium carbonate and stir at 60 ℃ for 3 h. Then, centrifuge at 3000 r / min for 2 min, discard the bottom precipitate, take the supernatant and dry it to obtain sodium ion modified bentonite.
[0105] 3) Sodium ion modified bentonite was prepared into a 3wt% suspension, stirred for 24 h, and then sonicated at 20 kHz for 30 min to obtain prehydrated bentonite.
[0106] 4) The prehydrated bentonite was frozen at -20 ℃ for 24 h and thawed twice. The thawed bentonite solution was sonicated at 20 kHz for 20 min and then centrifuged at 10000 r / min for 30 min to obtain the exfoliated montmorillonite nanosheet suspension.
[0107] 5) The sloughed montmorillonite nanosheet suspension was vacuum filtered through a mixed cellulose ester membrane with a pore size of 0.45 μm. The permeate was then transferred to a 100 kDa ultrafiltration membrane system for pressure filtration (pressure of 0.2 MPa). The ultrafiltration was repeated 3 times.
[0108] 6) The filtered liquid was rotary evaporated at 40 °C until the solid content was 50%, and 1% anhydrous ethanol was added to prevent the nanosheets from agglomerating. After ultrasonic dispersion for 10 min, the dispersion was poured into a freeze-drying pan, pre-frozen to -80 °C and then vacuum dried for 24 h to obtain high-purity montmorillonite with cristobalite removed.
[0109] Upon testing, the XRD pattern of the high-purity montmorillonite with cristobalite removed in Example 5 showed that all diffraction peaks belonged to montmorillonite, indicating that the use of a nanoscale filtration membrane can completely remove cristobalite and other associated impurities.
[0110] In summary, this invention removes large particulate impurities from calcium-based bentonite through preliminary wet purification, and then introduces sodium ions with excellent hydration capabilities into the interlayer of the bentonite via ion exchange modification and pre-hydration treatment, increasing its hydration and swelling performance. The bentonite can then be easily exfoliated into single-layer or few-layer nanosheets. These nanosheets are then subjected to multiple vacuum filtrations using micron-sized filtration membranes, followed by secondary pressure ultrafiltration using nanon-sized filtration membranes to deeply remove submicron-sized cristobalite, resulting in high-purity montmorillonite. The process provided by this invention is simple, has low production costs, generates no byproducts, and the resulting high-purity montmorillonite can be directly used in the production of pharmaceuticals, cosmetics, and other fields.
[0111] The above detailed embodiments describe the implementation of the present invention; however, the present invention is not limited to the specific details described in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.
Claims
1. A method for deep removal of quartz from bentonite using a nanoscale filtration membrane, characterized in that, Includes the following steps: S1. Disperse calcium-based bentonite in water, add an appropriate amount of dispersant, and then stir, let stand, centrifuge, and dry to obtain preliminarily purified bentonite. S2. The preliminarily purified bentonite is mixed with sodium salt in water for ion exchange modification to obtain sodium-based bentonite. S3. Sodium-based bentonite is prepared into a suspension and pre-hydrated to obtain pre-hydrated bentonite. S4. The prehydrated bentonite is peeled off to obtain a bentonite nanosheet suspension; S5. The bentonite nanosheet suspension is filtered through a microporous membrane to initially remove micron-sized cristobalite. S6. After the bentonite nanosheet permeate with micron-sized cristobalite removed was initially filtered through an ultrafiltration membrane, it was dried to obtain high-purity montmorillonite.
2. The method for deep removal of quartz from bentonite using a nanoscale filtration membrane according to claim 1, characterized in that, In step S6, the bentonite nanosheet permeate after the initial removal of micron-sized cristobalite is filtered under pressure through a 100kDa ultrafiltration membrane using an ultrafiltration device, and then vacuum dried to obtain high-purity montmorillonite.
3. The method for deep removal of quartz from bentonite using a nanoscale filtration membrane according to claim 1, characterized in that, In step S1, the dispersant is sodium hexametaphosphate and / or sodium pyrophosphate.
4. The method for deep removal of quartz from bentonite using a nanoscale filtration membrane according to claim 1, characterized in that, In step S1, after adding an appropriate amount of dispersant, a sodium hydroxide solution with a concentration of 0.1~1 mol / L is added to adjust the pH value to 8~10. Then, the mixture is stirred, allowed to stand, centrifuged, and dried to obtain preliminarily purified bentonite.
5. The method for deep removal of quartz from bentonite using a nanoscale filtration membrane according to claim 1, characterized in that, In step S2, the sodium salt includes, but is not limited to, at least one of sodium chloride, sodium pyrophosphate, and sodium carbonate.
6. The method for deep removal of quartz from bentonite using a nanoscale filtration membrane according to claim 1, characterized in that, In step S2, the temperature for ion exchange modification of the mixture is 40~80℃, and the time is 1~6 h.
7. The method for deep removal of quartz from bentonite using a nanoscale filtration membrane according to claim 1, characterized in that, The specific operation of step S3 is as follows: Sodium-based bentonite is prepared into a suspension with a concentration of 1wt%~5wt%, stirred for 12~24h, and then ultrasonically treated at an ultrasonic intensity of 20 kHz for 15~60 min to obtain prehydrated bentonite.
8. The method for deep removal of quartz from bentonite using a nanoscale filtration membrane according to claim 1, characterized in that, The specific operation of step S4 is as follows: the prehydrated bentonite is subjected to cyclic freezing treatment, the thawed bentonite is subjected to ultrasonic treatment and then centrifugation treatment to obtain a bentonite nanosheet suspension with 1-5 layers.
9. High-purity montmorillonite prepared by the method according to any one of claims 1-8.
10. The application of the high-purity montmorillonite according to claim 9 in the fields of medicine or cosmetics.