A method for separating gaseous heavy water

Abstract

The present invention relates to a method for separating gaseous heavy water from water vapor. The gaseous heavy water separation method comprises the following steps: preparing nanoporous graphene into a water suspension within a container, uniformly dispersing the suspension, vacuum filtering the suspension onto a nanofiltration membrane to form a uniform film, suspending the prepared film in still water vapor containing heavy water, allowing the heavy water in the water vapor to be fully adsorbed by the nanoporous graphene on the nanofiltration membrane, and then soaking the gaseous adsorbed membrane in deionized water at 60°C and allowing it to stand to obtain a desorbed solution. The method utilizes water vapor as the sole operating medium and is non-toxic, harmless, energy-efficient, and environmentally friendly. It also offers the advantages of easy disposal of reaction byproducts, a simple reaction process, low cost, and the elimination of the need for complex reaction processes, advanced reaction vessels, or high temperatures.

Description

Technical Field

[0001] The present invention relates to a method for separating heavy water, and more particularly to a method for separating gaseous heavy water from water vapor. Background Art

[0002] Heavy water has a wide range of applications in energy, military, scientific research, and medicine due to its superior neutron moderation compared to ordinary water and the stronger nuclear magnetic resonance signal of protium compared to deuterium. Current methods for separating deuterium include chemical exchange, electrolysis, cryogenic distillation, cryogenic adsorption, and laser separation. These include the technical solutions published in Chinese invention patents CN105408243A, CN107074539A, and CN105408243A. However, the only method used for industrial production is the Girdler-Sulfied method. This method has a relatively low single-stage separation rate, uses toxic and corrosive H2S gas, and is relatively expensive, thus limiting the industrial application of heavy water. Summary of the Invention

[0003] The object of the present invention is to provide a method for separating gaseous phase heavy water.

[0004] The gas-phase heavy water separation method of the present invention comprises the following steps: preparing nanoporous graphene into a water suspension in a container, uniformly dispersing the nanoporous graphene, vacuum filtering the nanofiltration membrane to form a uniform film, suspending the prepared membrane in still water vapor containing heavy water, so that the heavy water in the water vapor is fully adsorbed by the nanoporous graphene on the nanofiltration membrane, and then immersing the membrane after gas-phase adsorption in deionized water at 60°C and allowing it to stand to obtain a desorption solution.

[0005] Preferably, in the method for separating gaseous heavy water of the present invention, the abundance of heavy water atoms in the water vapor is 10-60%, and the mass ratio of nanoporous graphene to heavy water is 1:500-1:200.

[0006] Preferably, in the method for separating gaseous heavy water of the present invention, the pore size of the nanoporous graphene used is 3.5-4.5 nm.

[0007] More preferably, in the gas phase heavy water separation method of the present invention, the membrane after gas phase adsorption is immersed in deionized water at 60°C and allowed to stand for about 5 to 10 minutes.

[0008] Nanoporous graphene has a large number of nanoscale holes and a large relative area (~800m 2 / g). This invention uses nanoporous graphene as an adsorption material. Due to the different resistance encountered by light and heavy water molecules during their flow through the nanoporous graphene layers, they exhibit different adsorption capacities, effectively enriching heavy water. This invention applies nanoporous graphene to heavy water separation. By directly using water vapor as the operating medium, this significantly reduces the cost of heavy water enrichment, saves enrichment time, simplifies the enrichment process, and ultimately improves production efficiency.

[0009] The present invention has the following advantages:

[0010] 1) The present invention uses water vapor as the only operating medium, which is non-toxic, harmless, energy-saving, and environmentally friendly.

[0011] 2) The nanoporous graphene material used in the present invention can be prepared by a partial combustion method, the reaction byproducts are easy to handle, the reaction process is simple, and the cost is low.

[0012] 3) The present invention does not require a complicated reaction process and advanced reaction vessels, and does not require high temperature. Therefore, the reaction process is simple, economical, and rapid, and has the potential for large-scale application.

[0013] 4) The present invention demonstrates that nanoporous graphene materials with different pore size distributions are extremely promising materials for adsorbing heavy water. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The diagram shows the preparation route and preparation mechanism of the porous graphene described in the present invention.

[0015] Figure 2 Characterization diagrams of porous graphene, where a and b are transmission electron microscope images; c is a Raman spectrum characterization diagram of samples 100, 300, and 600; d is an infrared spectrum characterization diagram of the 600 sample; e and f are gas phase adsorption diagrams of Examples 1-6, respectively. DETAILED DESCRIPTION

[0016] The nanoporous graphene used in the embodiments of the present invention is prepared by a method for rapidly preparing porous graphene by a local combustion method. Please refer to the patent number: 201711053922.9, which was granted on November 19, 2019. It is a Chinese invention patent. The specific preparation process is briefly described as follows: first, 2 mL of 1 g / L graphene oxide suspension is prepared and ultrasonicated at room temperature for 10 minutes; 50 mg of zinc nitrate is weighed and dissolved in the above suspension, and ultrasonicated for 2 minutes; the above solution is filtered using quantitative filter paper; the filter paper and the residue are dried at 35°C; the filter paper with the residue is ignited and sintered until white zinc oxide covers the porous graphene; and the porous graphene is washed with a 0.01 mol / L hydrochloric acid aqueous solution to obtain the porous graphene.

[0017] The nanofiltration membrane used in the examples of the present invention is a commercial nanofiltration membrane with a diameter of 50 mm and a pore size of 0.45 μm, manufactured by Taoyuan Medical Chemical Instrument Factory. The mass ratio of the nanoporous graphene to heavy water is 1:500-1:200. The optimal abundance of the deuterium-containing gaseous water vapor is 10-60%. If the abundance is less than 0.015%, the separation efficiency of the present invention will be severely reduced.

[0018] Example 1

[0019] Steps:

[0020] 1. Weigh 2.5 mg of nanoporous graphene with a pore size of about 3.8 nm and prepare it into a suspension in a certain concentration of water in a test tube. After ultrasonic dispersion, vacuum filter it on a nanofiltration membrane to form a uniform film for later use.

[0021] 2. The prepared membrane was suspended in a round-bottom flask filled with static water vapor (deuterium content 15%) for about 45 minutes.

[0022] 3. Place the round-bottom flask in ice to cool it so that the adsorbed gaseous heavy water condenses and flows back to the bottom of the flask. Then collect the condensed water vapor for analysis.

[0023] 4. Immerse the membrane after gas phase adsorption in 2 ml of deionized water and let it stand at 60°C for 50 minutes to finally obtain the desorption solution.

[0024] 5. Remove the membrane and analyze the desorption liquid.

[0025] Example 2

[0026] Steps:

[0027] 1. Weigh 2.5 mg of nanoporous graphene with a pore size of about 3.8 nm and prepare it into a suspension in a certain concentration of water in a test tube. After ultrasonic dispersion, vacuum filter it on a nanofiltration membrane to form a uniform film for later use.

[0028] 2. The prepared membrane was suspended in a round-bottom flask filled with static water vapor (deuterium content 20%) for about 45 minutes.

[0029] 3. Place the round-bottom flask in ice to cool it so that the adsorbed gaseous heavy water condenses and flows back to the bottom of the flask. Then collect the condensed water vapor for analysis.

[0030] 4. Immerse the membrane after gas phase adsorption in 2 ml of deionized water and let it stand at 60°C for 50 minutes to finally obtain the desorption solution.

[0031] 5. Remove the membrane and analyze the desorption liquid.

[0032] Example 3

[0033] Steps:

[0034] 1. Weigh 2.5 mg of nanoporous graphene with a pore size of about 3.8 nm and prepare it into a suspension in a certain concentration of water in a test tube. After ultrasonic dispersion, vacuum filter it on a nanofiltration membrane to form a uniform film for later use.

[0035] 2. The prepared membrane was suspended in a round-bottom flask filled with static water vapor (deuterium content 25%) for about 45 minutes.

[0036] 3. Place the round-bottom flask in ice to cool it so that the adsorbed gaseous heavy water condenses and flows back to the bottom of the flask. Then collect the condensed water vapor for analysis.

[0037] 4. Immerse the membrane after gas phase adsorption in 2 ml of deionized water and let it stand at 60°C for 50 minutes to finally obtain the desorption solution.

[0038] 5. Remove the membrane and analyze the desorption liquid.

[0039] Example 4

[0040] Steps:

[0041] 1. Weigh 2.5 mg of nanoporous graphene with a pore size of about 4.2 nm and prepare it into a suspension in a certain concentration of water in a test tube. After ultrasonic dispersion, vacuum filter it on a nanofiltration membrane to form a uniform film for later use.

[0042] 2. The prepared membrane was suspended in a round-bottom flask filled with static water vapor (deuterium content 15%) for about 45 minutes.

[0043] 3. Place the round-bottom flask in ice to cool it so that the adsorbed gaseous heavy water condenses and flows back to the bottom of the flask. Then collect the condensed water vapor for analysis.

[0044] 4. Immerse the membrane after gas phase adsorption in 2 ml of deionized water and let it stand at 60°C for 50 minutes to finally obtain the desorption solution.

[0045] 5. Remove the membrane and analyze the desorption liquid.

[0046] Example 5

[0047] Steps:

[0048] 1. Weigh 2.5 mg of nanoporous graphene with a pore size of about 4.2 nm and prepare it into a suspension in a certain concentration of water in a test tube. After ultrasonic dispersion, vacuum filter it on a nanofiltration membrane to form a uniform film for later use.

[0049] 2. The prepared membrane was suspended in a round-bottom flask filled with static water vapor (deuterium content 20%) for about 45 minutes.

[0050] 3. Place the round-bottom flask in ice to cool it so that the adsorbed gaseous heavy water condenses and flows back to the bottom of the flask. Then collect the condensed water vapor for analysis.

[0051] 4. Immerse the membrane after gas phase adsorption in 2 ml of deionized water and let it stand at 60°C for 50 minutes to finally obtain the desorption solution.

[0052] 5. Remove the membrane and analyze the desorption liquid.

[0053] Example 6

[0054] Steps:

[0055] 1. Weigh 2.5 mg of nanoporous graphene with a pore size of about 4.2 nm and prepare it into a suspension in a certain concentration of water in a test tube. After ultrasonic dispersion, vacuum filter it on a nanofiltration membrane to form a uniform film for later use.

[0056] 2. The prepared membrane was suspended in a round-bottom flask filled with static water vapor (deuterium content 25%) for about 45 minutes.

[0057] 3. Place the round-bottom flask in ice to cool it so that the adsorbed gaseous heavy water condenses and flows back to the bottom of the flask. Then collect the condensed water vapor for analysis.

[0058] 4. Immerse the membrane after gas phase adsorption in 2 ml of deionized water and let it stand at 60°C for 50 minutes to finally obtain the desorption solution.

[0059] 5. Remove the membrane and analyze the desorption liquid.

[0060] The adsorption time and the deuterium abundance detection data of the condensed water vapor after adsorption in the above embodiments are shown in Table 1.

[0061] Table 1

[0062]

[0063] The surface morphology and related characterization of the nanoporous graphene of the present invention are shown in the attached Figure 2 For nanoporous graphene, the morphology was observed using a transmission electron microscope, and the obtained TEM image is as follows: Figure 2 As shown in a and b, a large number of white holes are distributed on the surface of nanoporous graphene. Figure 2 c shows the Raman spectra characterization of nanoporous graphene with different pore size distributions (named as: 100, 300, 600, 800 respectively), among which nanoporous graphene with different pore sizes all have the characteristic bands of graphene (D1 and G bands), and the value of the characteristic band D1 / G (integral area ratio) gradually decreases from 100 to 600 samples. This result shows that the defect sites sp 3 The gradual decrease in carbon proves that the quality of this type of material is gradually improving. Figure 2 d shows the infrared spectra of 600 samples of nanoporous graphene before and after the adsorption of heavy water. It can be observed from the figure that the characteristic peak position and peak intensity have changed significantly before and after the adsorption of heavy water, which indicates that heavy water is successfully adsorbed by nanoporous graphene. Figure 2 e and f show the test of the adsorption capacity of 600 and 800 sample nanoporous graphene for gaseous heavy water, respectively. The results show that both materials have a short adsorption equilibrium time, proving that the 600 and 800 sample materials have good heavy water adsorption capacity.

Claims

1. A method for separating gaseous heavy water, characterized in that First, nanoporous graphene is prepared, namely: first, 2 mL of 1 g / L graphene oxide suspension is prepared and ultrasonicated at room temperature for 10 minutes; 50 mg of zinc nitrate is weighed and dissolved in the above suspension and ultrasonicated for 2 minutes; the above solution is filtered using quantitative filter paper; the filter paper and residue are dried at 35°C; the filter paper with the residue is ignited and sintered until white zinc oxide covers the porous graphene; it is then washed with 0.01 mol / L hydrochloric acid aqueous solution to obtain nanoporous graphene with a pore size of 3.5-4.5 nm. The nanoporous graphene is prepared into an aqueous suspension in a container, and after uniform dispersion, it is vacuum filtered on a nanofiltration membrane to form a uniform membrane. The prepared membrane is suspended in still water vapor containing heavy water so that the heavy water in the water vapor is fully adsorbed by the nanoporous graphene on the nanofiltration membrane. The membrane after gas phase adsorption is then immersed in deionized water at 60°C and allowed to stand to obtain a desorption solution.

2. The method for separating gaseous heavy water according to claim 1, wherein The abundance of heavy water atoms in the water vapor is 10-60%, and the mass ratio of nanoporous graphene to heavy water is 1:500-1:

200.

3. The method for separating gaseous heavy water according to claim 1 or 2, characterized in that After gas phase adsorption, the membrane was immersed in deionized water at 60°C and allowed to stand for 5 minutes.

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