Mechanical ball-milling mthod for preparing a polydopamine-modified montmorillonite nanomaterial

Abstract

A mechanical ball-milling method for preparing a polydopamine-modified montmorillonite nanomaterial is disclosed. The method includes dispersing a montmorillonite material in an aqueous solution, stirring, concentrating and collecting a concentrated montmorillonite solution for use; adding dopamine hydrochloride to a buffer solution to prepare a dopamine hydrochloride solution, with a concentration of 0.2-1 g/mL, and adjusting the pH value of the dopamine hydrochloride solution; and adding the dopamine hydrochloride solution and the concentrated montmorillonite solution simultaneously into a ball mill jar to form a mixture, and then subjecting the mixture to a ball milling for 0.3-6 hours, pouring the mixture out of the ball mill jar, and subjecting to a solid-liquid separation by a centrifugation, and then washing a solid product with deionized water for 3-6 times, and removing water from the solid product, to obtain the polydopamine-modified montmorillonite nanomaterial.

Claims

1. A mechanical ball-milling method for preparing a polydopamine-modified montmorillonite nanomaterial, comprising: dispersing a montmorillonite material in an aqueous solution, stirring, concentrating, and collecting a concentrated montmorillonite solution for use; adding dopamine hydrochloride to a buffer solution to prepare a dopamine hydrochloride solution, with a concentration of 0.2-1 g/L, and adjusting a pH value of the dopamine hydrochloride solution, wherein hydrogen peroxide is added to the dopamine hydrochloride solution in an amount of 6-20 wt %; and adding the dopamine hydrochloride solution and the concentrated montmorillonite solution simultaneously into a ball mill jar to form a mixture, then subjecting the mixture to a ball milling for 0.3-6 hours, pouring the mixture out of the ball mill jar, subjecting the mixture to a solid-liquid separation by a centrifugation, then washing a solid product with deionized water for 3-6 times, and removing water from the solid product, to obtain a polydopamine-modified montmorillonite nanomaterial, wherein the ball milling is carried out using zirconia beads having diameters of 2 mm, 5 mm, 10 mm, and 15 mm as grinding balls, wherein a mass ratio for each diameter of the zirconia beads among the grinding balls is 4:8:20:5, respectively, wherein a mass ratio of grinding balls to material is between 10:1 and 50:1, and wherein the ball milling is carried out with a rotation speed of 300-500 r/min.

2. The mechanical ball-milling method for preparing a polydopamine-modified montmorillonite nanomaterial of claim 1, wherein dispersing the montmorillonite material in the aqueous solution, stirring, concentrating, and collecting the concentrated montmorillonite solution for use further comprises using a solid/liquid ratio of montmorillonite to deionized water is 1:50-100 g/mL.

3. The mechanical ball-milling method for preparing a polydopamine-modified montmorillonite nanomaterial of claim 1, wherein during the addition of the dopamine hydrochloride solution and the concentrated montmorillonite solution simultaneously into the ball mill jar to form the mixture, the pH value of the dopamine hydrochloride solution is 8-9.

4. The mechanical ball-milling method for preparing a polydopamine-modified montmorillonite nanomaterial of claim 1, wherein subjecting the mixture to a ball milling for 0.3-6 hours further comprises removing water from the solid product by a lyophilization, and wherein before the lyophilization a dilute solution with a solid substance concentration of 5-25 wt % is prepared with a substance to be lyophilized, and the lyophilization is carried out at a temperature of 40° C. to 50° C. for 24-72 hours.

5. The mechanical ball-milling method for preparing a polydopamine-modified montmorillonite nanomaterial of claim 1, wherein subjecting the mixture to a ball milling for 0.3-6 hours further comprises removing water from the solid product by a vacuum drying until a constant weight of the product is achieved, and a resulting product is subjected to another ball milling, to obtain the polydopamine-modified montmorillonite nanomaterial.

6. The mechanical ball-milling method for preparing a polydopamine-modified montmorillonite nanomaterial of claim 5, wherein the vacuum drying is carried out at a temperature of 80-100° C. for 6-12 hours.

7. The mechanical ball-milling method for preparing a polydopamine-modified montmorillonite nanomaterial of claim 5, wherein another ball milling is carried out for 15-30 mins. by using additional zirconia beads having diameters of 5 mm, 10 mm, 15 mm and 20 mm as grinding balls, with a mass ratio of grinding balls for each diameter of 3:8:20:8, a ball-to-material weight ratio of 10-50:1, and a rotation speed of 300-500 r/min.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a process flow diagram of the method according to the present disclosure.

(2) FIG. 2A shows a scanning electron microscope (SEM) image and an energy dispersive spectrometer (EDS) graph of the montmorillonite used in Example 1;

(3) FIG. 2B shows a SEM image and an EDS graph of the polydopamine-modified montmorillonite prepared with a ball milling method modification for 30 min in Example 1; and

(4) FIG. 2C shows a SEM image and an EDS graph of the polydopamine-modified montmorillonite prepared with a solution method modification for 6 hours in Example 1.

(5) FIG. 3 shows X-ray photoelectron spectroscopy (XPS) graphs of montmorillonite used in Example 1 (labeled as MMT), the polydopamine-modified montmorillonite prepared with a ball milling method modification for 30 min in Example 1 (labeled as Bal-MMT.sub.30min) and the polydopamine-modified montmorillonite prepared with a solution method modification for 6 hours in Example 1 (labeled as Sol-MMT.sub.6h), in which, (2) is a partial enlarged view of the range of 50-450 eV in (1).

(6) FIG. 4 shows a small-angle X-ray diffraction (XRD) pattern of the polydopamine-modified montmorillonite obtained in Example 1, with a ball milling method modification for 30 min and a solution method modification for 6 hours.

(7) FIG. 5 shows a comparison diagram of the preparation process of the ball milling method and the solution method in Example 1.

(8) FIG. 6 shows a small angle X-ray diffraction (XRD) pattern of the polydopamine-modified montmorillonite obtained in Example 2, with a ball milling method modification for 60 min and a lyophilization.

(9) FIG. 7 shows a small-angle X-ray diffraction (XRD) pattern of the polydopamine-modified montmorillonite obtained in Example 3, with a ball milling method modification for 90 min and a lyophilization.

(10) FIG. 8 shows a small angle X-ray diffraction (XRD) pattern of the polydopamine-modified montmorillonites obtained in Example 4, with a milling method modification for 30 min and another milling method modification for 20 min, and obtained in Example 1, with a ball milling method modification for 30 min and a lyophilization.

(11) FIG. 9 shows a comparison diagram of the preparation process of the ball milling method and the solution method in Example 4 and FIG. 10 is a flow chart of an embodiment of a method according to the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(12) The technical solutions in the embodiments of the present disclosure are described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all the embodiments.

(13) The present disclosure provides a mechanical ball-milling method for preparing a polydopamine-modified montmorillonite nanomaterial, as shown in FIG. 1 and FIG. 10, comprising the following steps:

(14) (1) dispersing a montmorillonite material in an aqueous solution, stirring, concentrating and collecting a concentrated montmorillonite solution for use;

(15) (2) adding dopamine hydrochloride to a buffer solution to prepare a dopamine hydrochloride solution, with a concentration of 0.2-1 g/mL, and adjusting a pH value of the dopamine hydrochloride solution; and

(16) (3) adding the dopamine hydrochloride solution and the concentrated montmorillonite solution simultaneously into a ball mill jar to form a mixture, then subjecting the mixture to a ball-milling for 0.3-6 hours, pouring the mixture out of the ball mill jar, subjecting to a solid-liquid separation by a centrifugation, then washing a solid product with deionized water for 3-6 times, and removing water from the solid product, to obtain a polydopamine-modified montmorillonite nanomaterial.

(17) In step (1), a solid/liquid ratio of montmorillonite to deionized water is 1:50-100 g/mL.

(18) In step (2), an oxidant in a small amount is added to the dopamine hydrochloride solution, wherein the oxidant includes any one of hydrogen peroxide, copper sulfate, ammonium sulfate, and sodium periodate, and the amount of the oxidant is 6-20 wt %. In some embodiments, the oxidant is hydrogen peroxide and/or copper sulfate.

(19) In step (2), a mass ratio of dopamine hydrochloride to montmorillonite is 1:1-1:2, and the pH value of the dopamine hydrochloride solution is 8-9.

(20) In step (3), the ball milling is carried out by using zirconia beads which include zirconia beads having a diameter of 2 mm, 5 mm, 10 mm and 15 mm as grinding balls, with a mass ratio of grinding balls for each diameter of 4:8:20:5, a ball-to-material weight ratio of 10-50:1, and a rotation speed of 300-500 r/min.

(21) In step (3), water is removed from the solid product by a lyophilization, and before the lyophilization a dilute solution with a solid substance concentration of 5-25 wt % is prepared with the substance to be lyophilized, and the lyophilization is carried out at a temperature of −40° C. to −50° C. for 24-72 hours.

(22) In step (3), water is removed from the solid product by a vacuum drying, and the resulting product is then subjected to another ball-milling, to obtain the polydopamine-modified montmorillonite nanomaterial.

(23) Further to that, the vacuum drying is carried out at a temperature of 80-100° C. for 6-12 hours, until that the mass of the sample is constant.

(24) Further to that, the another ball milling is carried out for 15-30 min by using zirconia beads which include zirconia beads having a diameter of 5 mm, 10 mm, 15 mm, and 20 mm, as grinding balls, with a mass ratio of grinding balls for each diameter of 3:8:20:8, a ball-to-material weight ratio of 10-50:1, and a rotation speed of 300-500 r/min.

(25) The present disclosure will be further described below in reference with specific examples and drawings:

Examples 1

(26) Ball Milling Method:

(27) 4 g of montmorillonite (MMT) was dispersed in 200 ml of aqueous solution, and they were stirred quickly, concentrated and a concentrated MMT solution was collected for use. 4 g of dopamine hydrochloride was added to a buffer solution to prepare a dopamine hydrochloride solution, and then 8 wt % hydrogen peroxide (oxidant) was added to the dopamine hydrochloride solution, and the pH value of the resulting solution was adjusted to 8-9. The resulting solution and the concentrated MMT solution were added simultaneously into a ball mill jar, and subjected to a ball-milling for 30 min, in which zirconia beads which include zirconia beads having a diameter of 2 mm, 5 mm, 10 mm and 15 mm, were used as grinding balls, with a mass ratio of grinding balls for each diameter of 4:8:20:5, a ball-to-material weight ratio of 30:1, and a rotation speed of 400 r/min. The solid product was separated by a ultrasonic centrifugation, then washed with deionized water, and lyophilized at a temperature of −40° C. to −50° C. for 48 hours, obtaining a polydopamine-modified MMT (Bal-MMT.sub.30min).

(28) Solution Method:

(29) 4 g of MMT was dispersed in 200 ml of aqueous solution, and they were stirred quickly to obtain an MMT suspension. 4 g of dopamine hydrochloride was added to a buffer solution to prepare the dopamine hydrochloride solution, and the pH value of the dopamine hydrochloride solution was adjusted to 8-9. The dopamine hydrochloride solution obtained was quickly added into the MMT suspension, and they were stirred with a high speed for 6 hours. The solid product was separated by a ultrasonic centrifugation, then washed with deionized water, and lyophilized at a temperature of −40° C. to −50° C. for 48 hours, obtaining a polydopamine-modified MMT (Sol-MMT.sub.6h).

(30) FIG. 2A shows a SEM image and an EDS graph of the montmorillonite used in Example 1; FIG. 2B shows a SEM image and an EDS graph of the polydopamine-modified montmorillonite prepared with a ball milling method modification for 30 min in Example 1; and FIG. 2C shows a SEM image and an EDS graph of the polydopamine-modified montmorillonite prepared with a solution method modification for 6 hours in Example 1. It can be seen from FIGS. 2A-2C that the surface of the MMT before modification was smoother and there was obvious agglomeration. After modification with dopamine, it can be seen from both of the SEM images of Bal-MMT.sub.30min and Sol-MMT.sub.6h that the MMT lamellas were expanded and in a curled state, indicating that dopamine can expand the MMT lamellas.

(31) FIG. 3 shows XPS graphs of montmorillonite used in Example 1 (labeled as MMT), the polydopamine-modified montmorillonite prepared with a ball milling method modification for 30 min in Example 1 (labeled as Bal-MMT.sub.30min) and the polydopamine-modified montmorillonite prepared with a solution method modification for 6 hours in Example 1 (labeled as Sol-MMT.sub.6h), in which, (2) is a partial enlarged view of the range of 50-450 eV in (1). As shown in (1) and (2) of FIG. 3, characteristic Al2p and Si2p signals of MMT appears at 79.5 eV and 107.7 eV. After modification with dopamine, the electron peak intensity of Al2p and Si2p signals of MMT was weakened, due to the polydopamine layer on the surface of MMT. In the XPS graph of Bal-MMT.sub.30min and Sol-MMT.sub.6h, characteristic Nis signal of dopamine appears at 406.7 eV. The result indicates that a polydopamine layer were formed on the surface of MMT after oxidation and self-polymerization of dopamine.

(32) FIG. 4 showed XRD diffraction patterns of Bal-MMT.sub.30min and Sol-MMT.sub.6h obtained in this example. It can be seen from the XRD patterns that the interlayer spacing d.sub.001 corresponding to the diffraction peak of the crystal plane (001) of MMT was 1.24 nm After being treated in this example, the diffraction peaks of the crystal plane (001) of Bal-MMT.sub.30min and Sol-MMT.sub.6h all moved to the small angle direction, and the interlayer spacing of Bal-MMT.sub.30min was expanded to d.sub.001=1.58 nm, and the interlayer spacing of Sol-MMT.sub.6h was expanded to d.sub.001=1.57 nm. The result indicated that this example could not only expand the interlayer spacing of MMT, but also achieve the interlayer expansion effect of the solution method for 6 hours, which was consistent with the result in FIG. 2. The preparation process was shown in FIG. 5, which shows a comparison diagram of the preparation process of the ball milling method and the solution method in Example 1.

Example 2

(33) 4 g of MMT was dispersed in 200 ml of aqueous solution, and they were stirred quickly, concentrated and a concentrated MMT solution was collected for use. 4 g of dopamine hydrochloride was added to a buffer solution to prepare a dopamine hydrochloride solution, and 8 wt % hydrogen peroxide was added to the dopamine hydrochloride solution, and the pH value of the resulting solution was adjusted to 8-9. The resulting solution and the concentrated MMT solution were added simultaneously to a ball mill jar, and subjected to a ball-milling for 60 min, in which zirconia beads which include zirconia beads having a diameter of 2 mm, 5 mm, 10 mm and 15 mm, were used as grinding balls, with a mass ratio of grinding balls for each diameter of 4:8:20:5, a ball-to-material weight ratio of 20:1, and a rotation speed of 400 r/min. The solid product was separated by a ultrasonic centrifugation, then washed with deionized water, and lyophilized at a temperature of −40° C. to −50° C. for 48 hours, obtaining a polydopamine-modified MMT (Bal-MMT.sub.60min).

(34) FIG. 6 shows the XRD diffraction pattern of Bal-MMT.sub.60min obtained in this example. It can be seen from the XRD pattern that the interlayer spacing d.sub.001 corresponding to the diffraction peak of the crystal plane (001) of MMT was 1.24 nm. After being treated in this example, the diffraction peak of the crystal plane (001) of Bal-MMT.sub.60min obviously moved to a small angle direction, and the interlayer spacing was expanded to d.sub.001=1.62 nm, indicating that this example can expand the interlayer spacing of MMT.

Example 3

(35) 4 g of MMT was added in 200 ml of aqueous solution, and they were stirred quickly, concentrated and a concentrated MMT solution was collected for use. 4 g of dopamine hydrochloride was added to a buffer solution to prepare a dopamine hydrochloride solution, and 8 wt % hydrogen peroxide was added to the dopamine hydrochloride solution, and the pH value of the resulting solution was adjusted to 8-9. The resulting solution and the concentrated MMT solution were added simultaneously to a ball mill jar, and subjected to a ball-milling for 90 min, in which zirconia beads which include zirconia beads having a diameter of 2 mm, 5 mm, 10 mm and 15 mm, were used as grinding balls, with a mass ratio of grinding balls for each diameter of 4:8:20:5, a ball-to-material weight ratio of 20:1, and a rotation speed of 400 r/min. The solid product was separated by a ultrasonic centrifugation, then washed with deionized water, and lyophilized at a temperature of −40° C. to −50° C. for 48 hours, obtaining a polydopamine-modified MMT (Bal-MMT.sub.90min).

(36) FIG. 7 shows the XRD diffraction pattern of Bal-MMT.sub.90min obtained in this example. It can be seen from the XRD pattern that the interlayer spacing d.sub.001 corresponding to the diffraction peak of the crystal plane (001) of MMT was 1.24 nm. After being treated in this example, the diffraction peak of the crystal plane (001) of Bal-MMT.sub.90min obviously moved to a small angle direction, and the interlayer spacing was expanded to d.sub.001=1.65 nm, indicating that this example can expand the interlayer spacing of MMT.

Example 4

(37) 4 g of MMT was dispersed in 200 ml of aqueous solution, and they were stirred quickly, concentrated and a concentrated MMT solution was collected for use. 4 g of dopamine hydrochloride was added to a buffer solution to prepare a dopamine hydrochloride solution, and 8 wt % hydrogen peroxide was added to the dopamine hydrochloride solution, and the pH value of the resulting solution was adjusted to 8-9. The resulting solution and the concentrated MMT solution were added simultaneously to a ball mill jar, and subjected to a ball-milling for 30 min, in which zirconia beads which include zirconia beads having a diameter of 2 mm, 5 mm, 10 mm and 15 mm, were used as grinding balls, with a mass ratio of grinding balls for each diameter of 4:8:20:5, a ball-to-material weight ratio of 10:1-50:1, and a rotation speed of 400 r/min. The solid product was separated by a ultrasonic centrifugation, then washed with deionized water, and vacuum dried at a temperature of 80° C. for 7 h, until the mass of the sample was constant. The resulting product was then subjected to another ball-milling for 20 min, in which zirconia beads which include zirconia beads having a diameter of 5 mm, 10 mm, 15 mm and 20 mm, were used as grinding balls, with a mass ratio of grinding balls for each diameter of 3:8:20:8, a ball-to-material weight ratio of 20:1, and a rotation speed of 400 r/min, obtaining a polydopamine-modified MMT (Ba.sub.2-MMT.sub.30min).

(38) FIG. 8 shows the XRD diffraction pattern of Bal.sub.2-MMT.sub.30min obtained in this example. It can be seen from the XRD pattern that the interlayer spacing d.sub.001 corresponding to the diffraction peak of the crystal plane (001) of MMT was 1.24 nm After being treated in this example, the diffraction peak of the crystal plane (001) of Bal.sub.2-MMT.sub.30min obviously moved to the small angle direction, and the interlayer spacing was expanded to d.sub.001=1.57 nm, indicating that this example can expand the interlayer spacing of MMT. Compared with the Bal-MMT.sub.30min in Example 1, the layer expansion effect of Bal.sub.2-MMT.sub.30min was equivalent to that of Bal-MMT.sub.30min. The preparation process was shown in FIG. 9, which shows a comparison diagram of the preparation process of the ball milling method and the solution method in Example 4.

(39) The above are only preferred embodiments of the present disclosure, and the protection scope of the present disclosure is not limited to the above-mentioned examples. For those skilled in the art, improvements and variations obtained without departing from the technical concept of the present disclosure should also be regarded as the protection scope of the present disclosure.