Graphene Oxide Membrane With A Controllable Interlayer Spacing, A Preparation Method And Use Thereof

Abstract

A graphene oxide membrane with a controllable interlayer spacing, a preparation method and use thereof are provided. The preparation method provides of infiltrating a graphene oxide membrane in an aqueous solution A of salt to swell, thereby obtaining the graphene oxide membrane with the controllable interlayer spacing. The aqueous solution A of salt is a solution containing metal cation, and the concentration of the metal cation in the aqueous solution A is from 0.25-2.5 mol/L. The application can precisely control the size of the interlayer spacing of the graphene oxide membrane in the range of 1114 , and the variable range of this spacing can be controlled to within 0.61 . The graphene oxide membrane with the controllable interlayer spacing of the application has excellent mechanical strength, which remains a complete membrane state after 5 hours of infiltration. The preparation process is simple and easy to be operated, and the obtained graphene oxide membrane has a function of screening and filtering smaller ions, and thus has a good application prospect.

Claims

1. A method of preparing a graphene oxide membrane with a controllable interlayer spacing, comprising: infiltrating a graphene oxide membrane in an aqueous solution A of salt to swell, thereby obtaining the graphene oxide membrane with the controllable interlayer spacing, wherein the aqueous solution A of salt is a solution containing metal cation, and the concentration of the metal cation in the aqueous solution A is from 0.25 to 2.5 mol/L.

2. The method according to claim 1, wherein the graphene oxide membrane is prepared from a graphene oxide solution through a drop-cast method or a suction filter method.

3. The method according to claim 2, wherein the first drying is at 5565 C. for 57 hours; and/or, the second drying is at 5565 C. for 1113 hours.

4. The method according to claim 1, wherein during the infiltration, ambient temperature is from 17 to 23 C.; the metal cation is one or more of K.sup.+, Na.sup.+, Li.sup.+, Ca.sup.2+, and Mg.sup.2+; the pH of the aqueous solution A is 58; and/or, the time of the infiltration is from 1 to 3 hours.

5. The method according to claim 1 wherein the aqueous solution A of salt contains an anion which is an anion wherein the size of hydrated anion is smaller than hydrated cation; in the aqueous solution A of salt, when the metal cation is K.sup.+, the anion includes one or more of F.sup., Cl.sup., Br.sup., I.sup., and NO.sub.3.sup. in addition to OH.sup.; and/or, in the aqueous solution A of salt, when the metal cation is Na.sup.+, Li.sup.+ or Ca.sup.2+, the anion includes one or more of F.sup., Cl.sup., Br.sup., I.sup. and NO.sup.3 in addition to OH.sup.; and/or, in the aqueous solution A of salt, when the metal cation is Mg.sup.2+, the anion includes one or more of F.sup., Cl.sup., Br.sup., I.sup., SO.sub.4.sup.2, and NO.sub.3.sup. in addition to OH.sup..

6. A graphene oxide membrane with a controllable interlayer spacing produced by the method according to claim 1.

7. The graphene oxide membrane according to claim 6, wherein the graphene oxide membrane with the controllable interlayer spacing is selected from any one of following membranes: 1) in the aqueous solution A of salt, the metal cation is K.sup.+, and the size of the interlayer spacing of the graphene oxide membrane with the controllable interlayer spacing is 11.40.1 ; 2) in the aqueous solution A of salt, the metal cation is Na.sup.+, and the size of the interlayer spacing of the graphene oxide membrane with the controllable interlayer spacing is 12.10.2 ; 3) in the aqueous solution A of salt, the metal cation is Ca.sup.2+, and the size of the interlayer spacing of the graphene oxide membrane with the controllable interlayer spacing is 12.90.2 ; 4) in the aqueous solution A of salt, the metal cation is Li.sup.+, and the size of the interlayer spacing of the graphene oxide membrane with the controllable interlayer spacing is 13.50.2 ; 5) in the aqueous solution A of the salt, the metal cation is Mg.sup.2+, and the size of the interlayer spacing of the graphene oxide membrane with the controllable interlayer spacing is 13.60.1 .

8. A method wherein the graphene oxide membrane with the controllable interlayer spacing according to claim 7 is used in filtering an aqueous solution B of salt.

9. The method according to claim 8, wherein the aqueous solution B of salt has a concentration of from 0.25 to 2.5 mol/L; the operation of filtering is carried out according to following steps: controlling the interlayer spacing of the graphene oxide membrane by the aqueous solution A of salt, and then filtering the aqueous solution B of the salt by the graphene oxide membrane with the controlled interlayer spacing; and/or, the amount of the aqueous solution B of salt is the same as the amount of the aqueous solution A for controlling the interlayer spacing.

10. The method according to claim 9, wherein the graphene oxide membrane with the controllable interlayer spacing is prepared by any one of the following methods: 1) the graphene oxide membrane with the controllable interlayer spacing is prepared by infiltrating a graphene oxide membrane in aqueous solution A of salt containing K.sup.+, which entraps K.sup.+ and ions or molecules with hydrated radii greater than 3.31 , but allows water molecules to pass; 2) the graphene oxide membrane with the controllable interlayer spacing is prepared by infiltrating a graphene oxide membrane in aqueous solution A of salt containing Na.sup.+, which entraps ions or molecules with hydrated radii greater than 3.58 , but allows ions or molecules with a hydrated ionic radius of 3.58 or less to pass; 3) the graphene oxide membrane with the controllable interlayer spacing is prepared by infiltrating a graphene oxide membrane in aqueous solution A of salt containing Ca.sup.2+, which entraps ions or molecules with a hydrated ionic radius greater than 4.12 , but allows ions and molecules with a hydrated ionic radius of 4.12 or less to pass; 4) the graphene oxide membrane with the controllable interlayer spacing is prepared by infiltrating a graphene oxide membrane in the aqueous solution A of salt containing Li.sup.+, which entraps ions or molecules with a hydrated ionic radius greater than 3.82 , but allows ions and molecules with a hydrated ionic radius of 3.82 or less to pass; or 5) the graphene oxide membrane with the controllable interlayer spacing is prepared by infiltrating a graphene oxide membrane in the aqueous solution A of salt containing Mg.sup.2+, which entraps ions or molecules with a hydrated ionic radius greater than 4.28 , but allows ions and molecules with a hydrated ionic radius of 4.28 or less to pass.

11. The method according to claim 2, wherein the method for preparing the graphene oxide membrane through the drop-cast method comprises: dropping 0.81.2 mL of 35 mg/mL graphene oxide solution on a paper sheet, after a first drying, rinsing the paper sheet repeatedly with deionized water, and immersing the paper sheet in deionized water for half an hour and then taking the paper sheet out, after a second drying, obtaining the graphene oxide membrane.

12. The method according to claim 3, wherein the first drying is performed at 60 C. for 6 hours.

13. The method according to claim 3, wherein the second drying is performed at 60 C. for 12 h.

14. The method of claim 4, wherein during infiltrating, the ambient temperature is 20 C.

15. The method of claim 4, wherein the pH of the aqueous solution is at 7.

16. The method of claim 5, wherein in addition to OH.sup., the anion is one or more of Cl.sup., F.sup., Br.sup., SO.sub.4.sup.2, and NO.sub.3.sup..

17. The method of claim 5, wherein in addition to OH.sup., the anion is one or more of Cl.sup., F.sup., and Br.sup..

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] FIG. 1 is a topographical view of graphene oxide membrane of Example 1, wherein A is a physical photo of graphene oxide membrane, B is a scanning electron microscope view of a surface topography of graphene oxide membrane, and C is an atomic force microscope view of a surface topography of graphene oxide membrane.

[0050] FIG. 2 is a graph showing the interlayer spacing data of the products obtained by immersing the graphene oxide membranes in different salt solutions in Examples 2 to 6 and in pure water.

[0051] FIG. 3 is a graph showing the interlayer spacing data of graphene oxide membranes with controllable interlayer spacings after being infiltrated in different solutions.

[0052] FIG. 4 is a graph showing the results of graphene oxide membranes and graphene oxide membranes with controllable interlayer spacings after adsorption of salt solution in different solutions, wherein A is a graph showing the results of graphene oxide membranes after adsorption of salt solution in different solutions (in each group, the wet membrane weight is on the left side and the dry membrane weight is on the right side), B is a graph showing the results of graphene oxide membranes with controllable interlayer spacings after adsorption of salt solution in different solutions (in each group, the wet membrane weight (membrane+salt solution within the membrane) is on the left side, the dry membrane weight (membrane+salt weigh within the membrane) is on the left side)).

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0053] The application is further illustrated by the following examples, which are not intended to limit the application. The experimental methods in the following examples, which do not specify the specific conditions, are selected according to conventional methods and conditions, or according to the manufacturer's instructions.

Example 1

[0054] Preparation method of graphene oxide solution (modified Hummers method):

[0055] 1) Pre-oxidation of graphite: 2.5 g of potassium persulfate (K.sub.2S.sub.2O.sub.8) and 2.5 g of phosphorus pentoxide (P.sub.2O.sub.5) are dissolved in 12 mL of concentrated sulfuric acid, and heated to 80 C. 3 g of natural graphite is added to the above solution, and incubated at 80 C. for 4.5 h. The obtained solution is cooled to room temperature, diluted with 500 mL of deionized water, and stand overnight. Residual acid is removed by filtrating with a 0.2 mm filter. The pre-oxide is obtained by drying in a vacuum oven at 60 C.

[0056] 2) Oxidation: the obtained pre-oxide is added to 120 mL of concentrated sulfuric acid in an ice bath, and 15 g of KMnO.sub.4 is slowly added while stirring and the temperature should be kept below 20 C. during the stirring. It is then stirred at 35 C. for 2 hours. 250 mL of deionized water is then added, and the dilution process should also be conducted in an ice bath so that the temperature is controlled below 50 C. After stirred for another 2 hours, 0.7 L of deionized water is added, and 20 mL of 30% H.sub.2O.sub.2 is immediately added. After the above mixing, bubbles are generated in the solution, and the color changes from brown to bright yellow, and the reaction is terminated after about 0.5 hours.

[0057] 3) Post-treatment: the above mixture is filtered and washed with 1 L of 1:10 dilute hydrochloric acid, wherein the purpose of filtration is to remove part of metal ions. Then it is washed with 1 L of water to remove excess acid. The solution is dissolved in 1 L of deionized water. Then, a graphene oxide solution is obtained by ultrasonic at 100 W for about 0.5 hour, in which the carbon content is about 5 mg/mL.

[0058] The method for preparing graphene oxide membrane by a drop-cast method comprises the following steps:

[0059] 1 mL of 35 mg/mL graphene oxide solution is dropped on a smooth paper sheet, which is dried in an oven at 60 C. for about 12 h. The independent graphene oxide membrane is removed and rinsed repeatedly with deionized water. After being infiltrated in a large amount of deionized water for half an hour, the graphene oxide membrane is taken out, dried at 60 C. for 6 hours, and then placed in a drying vessel for use. The obtained graphene oxide membrane has a thickness of about 30 m.

[0060] FIG. 1 is a topographical view of graphene oxide membrane of Example 1, wherein A is a physical photo of graphene oxide membrane, B is a scanning electron microscope view of a surface topography of graphene oxide membrane, and C is an atomic force microscope view of a surface topography of graphene oxide membrane.

[0061] The graphene oxide membrane prepared in this Example has the characteristics of ultra-thin, high flow rate, energy-saving and the like, and has independent and unsupported mechanical strength, and can be directly used for saltwater screening and separation.

Example 2

[0062] A sample of the graphene oxide membrane prepared in Example 1 is infiltrated in 0.25 mol/L KCl solution for 1 h (pH 7 and ambient temperature is 20 C.) so that the raw material is fully swelled, and the corresponding graphene oxide membrane with a controllable interlayer spacing is obtained. XRD is used to detect the size of interlayer spacing.

Example 3

[0063] A sample of the graphene oxide membrane prepared in Example 1 is infiltrated in 0.25 mol/L NaCl solution for 1 h (pH 7 and ambient temperature is 20 C.) so that the raw material is fully swelled, and the corresponding graphene oxide membrane with a controllable interlayer spacing is obtained. XRD is used to detect the size of the interlayer spacing.

Example 4

[0064] A sample of the graphene oxide membrane prepared in Example 1 is infiltrated in 0.25 mol/L CaCl.sub.2) solution for 1 h (pH 7 and ambient temperature is 20 C.) so that the raw material is fully swelled, and the corresponding graphene oxide membrane with a controllable interlayer spacing is obtained. XRD is used to detect the size of the interlayer spacing.

Example 5

[0065] A sample of the graphene oxide membrane prepared in Example 1 is infiltrated in 0.25 mol/L LiCl solution for 1 h (pH 7 and ambient temperature is 20 C.) so that the raw material is fully swelled, and the corresponding graphene oxide membrane with a controllable interlayer spacing is obtained. XRD is used to detect the size of the interlayer spacing.

Example 6

[0066] A sample of the graphene oxide membrane prepared in Example 1 is infiltrated in 0.25 mol/L MgCl.sub.2 solution for 1 h (pH 7 and ambient temperature is 20 C.) so that the raw material is fully swelled, and the corresponding graphene oxide membrane with a controllable interlayer spacing is obtained. XRD is used to detect the size of the interlayer spacing.

[0067] Effect Example 1

[0068] XRD (X-ray diffractometer) is used to detect the size of the interlayer spacing of the graphene oxide membranes with controllable interlayer spacings of the embodiments.

[0069] FIG. 2 is a graph showing the interlayer spacing data of the products obtained by immersing the graphene oxide membranes in different salt solutions in Examples 2 to 6 and in pure water. It can be seen that the graphene oxide membranes with different interlayer spacings will be obtained by immersing the graphene oxide membranes in different salt solutions.

[0070] Four samples of the graphene oxide membrane prepared in Example 1 are infiltrated in 0.25 mol/L KCl solution for 1 h (pH 7 and ambient temperature is 20 C.) so that the raw materials are fully swelled, and the corresponding graphene oxide membranes with controllable interlayer spacings are obtained. Then, an equal amount of 0.25 mol/L NaCl solution, CaCl.sub.2 solution, LiCl solution and MgCl.sub.2 solution are added to form a mixed salt solution, in which the membranes are infiltrated for 0.5 hour (pH 7, and ambient temperature is 20 C.). XRD is then used to detect the size of the interlayer spacing.

[0071] FIG. 3 is a graph showing the interlayer spacing data of graphene oxide membranes with controllable interlayer spacings after being infiltrated in different solutions. It can be seen that, as to the graphene oxide membrane with the controllable interlayer spacing controlled by KCl, the interlayer spacing without adding any salt solution is substantially the same as the interlayer spacing after adding an equal amount of other salt solution. Thus, the obtained interlayer spacing is very stable after being controlled by KCl, and is not affected by the subsequent addition of other salt solutions. The subsequent addition of the salt solution cannot increase the size of the interlayer spacing, that is to say, the ion for controlling the smaller size of the interlayer spacing has a trapping effect to the other ions.

Effect Example 2

[0072] The ability of absorbing the salt solution of graphene oxide membrane is detected as follows:

[0073] Four samples of the graphene oxide membrane obtained in Example 1 are infiltrated in 0.25 mol/L KCl solution, NaCl solution, LiCl solution, CaCl.sub.2) solution and MgCl.sub.2 solution respectively for 1 hour (pH 7 and ambient temperature is 20 C.). The above infiltrating solution is removed, and the water on the surfaces of the membranes is removed by centrifugation. The wet membrane is weighed and placed in an oven at 60 C. for 6 hours, and then the dry membrane is weighed.

[0074] The ability of absorbing the salt solution of graphene oxide membranes with controllable interlayer spacings are detected as follows:

[0075] Four samples of the graphene oxide membrane prepared in Example 1 are infiltrated in 0.25 mol/L KCl solution for 1 hour (pH 7 and ambient temperature is 20 C.) so that the raw materials are fully swelled, and the corresponding graphene oxide membranes with controllable interlayer spacings are obtained. Then, an equal amount of 0.25 mol/L NaCl solution, CaCl.sub.2) solution, LiCl solution and MgCl.sub.2 solution are added to form a mixed salt solution, in which the membranes are infiltrated for 0.5 hour. The above infiltrating solution is removed, and the water on the surfaces of the membranes is removed by centrifugation. The wet membrane is weighed and placed in an oven at 60 C. for 6 hours, and then the dry membrane is weighed.

[0076] FIG. 4 is a graph showing the results of graphene oxide membranes and graphene oxide membranes with controllable interlayer spacings after adsorption of salt solution in different solutions, wherein A is a graph showing the results of graphene oxide membranes after adsorption of salt solution in different solutions (in each group, the wet membrane weight is on the left side and the dry membrane weight is on the right side), B is a graph showing the results of graphene oxide membranes with controllable interlayer spacings after adsorption of salt solution in different solutions (in each group, the wet membrane weight (membrane+salt solution within the membrane) is on the left side, the dry membrane weight (membrane+salt weight within the membrane) is on the left side)). It can be seen from A, when the graphene oxide membranes are immersed in five kinds of salt solutions, respectively, the salt water adsorptions of the membranes are different are larger, and a certain amount of salt after drying is contained in the membranes. It can be seen from B, when the graphene oxide membranes are infiltrated in KCl solution firstly and then an equal amount of other salt solutions is subsequently added, the adsorption amount of salt solution is substantially same to that of the pure KCl solution, and the weight of the dried membrane is substantially same to the weight of dried membrane after immersed in pure KCl solution. It shows that the KCl solution can effectively prevent the penetration of other salt solutions after adjusting the membrane channel, which is obviously less than the adsorption amount of other salt solutions after infiltration, but the weight of wet membrane is still about 2.4 times that of the dry membrane, which indicates that water molecules can still penetrate into the membrane.

[0077] While the invention has been described with above preferred embodiments, it should be understood by the person skilled in the art that the embodiments are only examples, and may be altered or modified without departing from the spirit and scope of the invention.

[0078] Accordingly, the scope of the invention is defined by the appended claims.