Super activated carbon for electrosorption desalination and preparation method thereof
By performing constant temperature activation and "ventilation-vacuum" treatment on the fruit shell, super activated carbon with high pore capacity and high specific surface area was prepared, which solved the problem of difficult preparation of super activated carbon in the prior art, and achieved its excellent performance in electrosorption and desalination and the possibility of large-scale production.
Patent Information
- Application Number
- CN202310883431.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-07-19
- Publication Date
- 2025-04-25
- Estimated Expiration
- 2043-07-19
AI Technical Summary
It is difficult to macro-preparation of super activated carbon with high pore capacity and high specific surface area in the prior art, resulting in poor performance in electrosorption and desalting.
The super activated carbon was prepared by using fruit shells as raw materials through multiple "ventilation-vacuum" during constant temperature activation to ensure high pore capacity and large specific surface area. It also exhibited an electrosorption and desalting amount of 20 to 70 mg/g in a 500 mg/L NaCl solution at a voltage of 1.2V.
The prepared super activated carbon has a large pore capacity (2.0-2.5 ml/g) and a high specific surface area (2290-3000 m2/g), and has good performance in electrosorption and desalting, and this method is suitable for large-scale production.
Smart Images
Figure CN117049535B_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of activated carbon preparation, and specifically relates to super activated carbon for electric adsorption desalination and a preparation method thereof. Background Art
[0002] Capacitive deionization has the characteristics of low energy consumption and no secondary pollution, and is regarded as a desalination technology with great application prospects. Electrode materials are the core of electrosorption desalination technology. Activated carbon has the characteristics of low price, adjustable pore structure and surface chemical properties, and is a potential electrosorption desalination material. However, the specific surface area of traditional activated carbon is less than 1200m 2 / g, pore volume <1.2ml / g, its electro-adsorption desalination capacity is not ideal. Super activated carbon refers to a carbon with a specific surface area of 2000m 2 / g is a special type of activated carbon. We found that super activated carbon with high pore volume (>2.0ml / g) has excellent desalination performance. However, the preparation of this type of activated carbon is extremely difficult and is rarely reported in domestic and foreign literature. Therefore, exploring methods suitable for large-scale preparation of this type of activated carbon has become an urgent need in the field of low-energy desalination. Summary of the invention
[0003] The technical problem to be solved by the present invention is to provide a super activated carbon for electric adsorption desalination and a preparation method thereof. The activated carbon is made of fruit shells and is repeatedly "ventilated-vacuumed" during the constant temperature activation process. The super activated carbon obtained has a high pore volume and a large specific surface area. It exhibits an electric adsorption desalination capacity of 20 to 70 mg / g in a 500 mg / L NaCl solution at a voltage of 1.2 V and can be mass-produced. The technical solution adopted is:
[0004] A super activated carbon for electric adsorption desalination, which uses fruit shells as raw materials, and is immersed in an acid solution for constant temperature activation. The super activated carbon has a pore volume of 2.15-2.5 ml / g and a specific surface area of 2290-3000 m 2 / g, and the electrosorption desalination capacity in 500mg / L NaCl solution at a voltage of 1.2V is 28-70mg / g.
[0005] Preferably, the acid is phosphoric acid, and the concentration of the phosphoric acid solution is 35-45 wt %.
[0006] Preferably, the amount of desalination by electrosorption is measured by mixing activated carbon, carbon black and PVDF to form an electrode sheet in an electrosorption desalination device without an ion exchange membrane.
[0007] The above-mentioned method for preparing super activated carbon for electric adsorption desalination comprises the following steps:
[0008] (1) immersing the fruit shell in a phosphoric acid solution to obtain a mixture, and then drying to a constant weight to obtain a phosphoric acid-loaded fruit shell containing pure phosphoric acid;
[0009] (2) the phosphoric acid-loaded fruit shells are quickly transferred to a tubular furnace at 860-950° C. in a flow of N2-water vapor at a pressure of less than 1.2 bar for constant temperature activation, the tubular furnace is heated to maintain a constant temperature, and after every 30-60 minutes of activation, the gas flow is cut off, the furnace tube is evacuated to a vacuum degree greater than 0.4 bar, and maintained for 30-180 seconds, and then a mixture of N2-water vapor at a pressure of less than 1.2 bar is introduced again;
[0010] (3) After several "ventilation-vacuuming" cycles, until the activation time reaches 130 to 300 minutes;
[0011] (4) After activation, the product is taken out, washed to neutrality, and then dried to obtain the super activated carbon.
[0012] Preferably, in step (1), the drying temperature is 100-120°C.
[0013] Preferably, in step (2), the relative humidity of the N2-water vapor flow is greater than 90%.
[0014] Preferably, in step (3), the number of "ventilation-vacuuming" cycles is 3 to 6 times.
[0015] Preferably, in step (4), the product is washed with deionized water until it becomes neutral, and then dried in a drying oven at 40 to 60° C. to a constant weight.
[0016] As a further preference, the relative humidity of the N2-water vapor flow used is greater than 90% (at 25°C) and as large as possible, the temperature of constant temperature activation is 950°C, and the number of "ventilation-vacuuming" cycles is 6 times. When the time reaches 300 minutes, the pore volume of the prepared super activated carbon is the largest, which is 2.50 ml / g.
[0017] Compared with the prior art, the present invention is beneficial in that:
[0018] 1) The super activated carbon prepared by the present invention has a large pore volume (2.0-2.5 ml / g) and a high specific surface area (2290-3000 m 2 / g);
[0019] 2) The super activated carbon prepared by the present invention can show an electro-adsorption desalination capacity of 20 to 70 mg / g in a 500 mg / L NaCl solution at a voltage of 1.2 V;
[0020] 3) The entire preparation does not require expensive raw materials, activators, equipment, etc. The raw materials are easily available, which is convenient for industrial large-scale production and application. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 This is a scanning electron microscope image of the super activated carbon prepared in Example 1 of the present invention;
[0022] Figure 2 This is the N2 adsorption-desorption isotherm of the super activated carbon prepared in Example 1 of the present invention. DETAILED DESCRIPTION
[0023] The drawings are only used for illustrative purposes; for those skilled in the art, some well-known structures and their descriptions in the drawings may be omitted, and therefore, they should not be understood as limitations on the present invention.
[0024] The technical solutions and effects of the present invention are described in detail below with reference to the accompanying drawings.
[0025] Example 1
[0026] A method for preparing super activated carbon for electric adsorption desalination, which can prepare activated carbon with high pore volume, comprises the following steps:
[0027] (1) H3PO4 with a concentration of 35 wt% was mixed with coconut shell, and then dried at 100°C to constant weight to obtain coconut shell containing 40 wt% pure H3PO4.
[0028] (2) The coconut shell loaded with phosphoric acid was placed in a quartz boat and quickly pushed into a tube furnace at 890°C in a N2-water vapor flow at a pressure of 1.05 bar (the relative humidity of the flow at 25°C was 91%). After constant temperature activation for 40 minutes, the flow was cut off, and the furnace tube was evacuated to a vacuum degree of 0.5 bar and maintained for 40 seconds. After that, the N2-water vapor mixture was introduced again.
[0029] (3) Repeat the “ventilation-vacuuming” cycle 4 times until the activation time reaches 150 minutes.
[0030] (4) After activation, the product is taken out, washed to neutrality, and then dried to obtain the super activated carbon.
[0031] The specific surface area and pore volume of the material were obtained by nitrogen adsorption and desorption technology. In addition, the material was mixed with carbon black and PVDF in a mass ratio of 8:1:1 to make an electrode sheet, and its desalination performance was evaluated in a 1.2V, 500mg / L NaCl solution in a capacitive deionization device without an ion exchange membrane. It was found that the pore volume of the material was 2.15ml / g and the specific surface area was 2290m 2 / g, and the desalination capacity is 28mg / g.
[0032] Example 2
[0033] A method for preparing super activated carbon for electric adsorption desalination can prepare activated carbon with high pore volume, and the specific steps include:
[0034] (1) H3PO4 with a concentration of 45 wt% was mixed with walnut shell powder, and then dried at 100°C to constant weight to obtain a walnut shell powder mixture containing 60 wt% pure H3PO4.
[0035] (2) The phosphate-loaded walnut powder mixture is placed in a quartz boat and quickly pushed into a tube furnace at 890°C in a N2-water vapor flow at a pressure of 1.07 bar (the relative humidity of the flow at 25°C is 92%). After constant temperature activation for 50 minutes, the flow is cut off, and the furnace tube is evacuated to a vacuum degree of 0.6 bar and maintained for 50 seconds. After that, the N2-water vapor mixture is introduced again.
[0036] (3) Repeat the “ventilation-vacuuming” cycle 4 times until the activation time reaches 180 minutes.
[0037] (4) After activation, the product is taken out, washed to neutrality, and then dried to obtain the super activated carbon.
[0038] The specific surface area and pore volume of the material were obtained by nitrogen adsorption and desorption technology. In addition, the material was mixed with carbon black and PVDF in a mass ratio of 8:1:1 to make an electrode sheet, and its desalination performance was evaluated in a 1.2V, 500mg / L NaCl solution in a capacitive deionization device without an ion exchange membrane. It was found that the pore volume of the material was 2.25ml / g and the specific surface area was 2460m 2 / g, and the desalination capacity is 32mg / g.
[0039] Example 3
[0040] A method for preparing super activated carbon for electric adsorption desalination can prepare activated carbon with high pore volume, and the specific steps include:
[0041] (1) H3PO4 with a concentration of 45 wt% was mixed with walnut shell powder, and then dried at 110°C to constant weight to obtain phosphoric acid-loaded nut shells containing 50 wt% pure H3PO4.
[0042] (2) The phosphoric acid-loaded fruit shells of step (1) are placed in a quartz boat and rapidly pushed into a tube furnace having a temperature of 910° C. in a N2-water vapor flow at a pressure of 1.03 bar (the relative humidity of the flow at 25° C. is 91%). After constant temperature activation for 50 min, the flow is cut off, and the furnace tube is evacuated to a vacuum degree of 0.7 bar and maintained for 50 s. Thereafter, the N2-water vapor mixture is introduced again.
[0043] (3) Repeat the “ventilation-vacuuming” cycle 4 times until the activation time reaches 200 minutes.
[0044] (4) Finally, wash the sample to neutrality and dry it.
[0045] The specific surface area and pore volume of the material were obtained by nitrogen adsorption and desorption technology. In addition, the material was mixed with carbon black and PVDF in a mass ratio of 8:1:1 to make an electrode sheet, and its desalination performance was evaluated in a 1.2V, 500mg / L NaCl solution in a capacitive deionization device without an ion exchange membrane. It was found that the pore volume of the material was 2.36ml / g and the specific surface area was 2720m 2 / g, and the desalination capacity is 39mg / g.
[0046] Figure 1 The N2 adsorption-desorption isotherms and scanning electron microscope images of the final product are listed in the figure.
[0047] The effects of vacuum conditions, activation atmosphere type, activation atmosphere humidity, activation temperature, and phosphoric acid concentration on the pore volume, specific surface area, and desalination capacity of the obtained product were tested.
[0048] Comparative Example 1
[0049] The process is basically the same as Example 1, but without the cycle of cutting off the gas flow and pumping negative pressure, N2-water vapor flow is introduced at a constant flow rate, and the activation time is 150 minutes. The test shows that the specific surface area of the obtained material is 1400m 2 / g, the pore volume is 1.25ml / g, and the desalination amount is 16mg / g. Combining Comparative Example 1 with Example 1, it can be seen that the introduction of the step of cutting off the gas flow and pumping negative pressure plays an important role in the preparation of super activated carbon with high pore volume.
[0050] Comparative Example 2
[0051] The process is basically the same as in Example 1, but the relative humidity of the N2-water vapor flow at room temperature is 80%. The test shows that the specific surface area of the obtained material is 1500m 2 / g, the pore volume is 1.325ml / g, and the desalination capacity is 18mg / g. Combining Comparative Example 2 with Example 1, it can be seen that controlling the relative humidity of the N2-water vapor flow used plays an important role in preparing super activated carbon with high pore volume.
[0052] Comparative Example 3
[0053] The same as Example 2, but the constant temperature activation temperature used is 780°C. Tests show that the specific surface area of the material is 1300m 2 / g, the pore volume is 1.05ml / g, and the desalination capacity is 12mg / g. Combining Comparative Example 3 with Example 2, it can be seen that controlling the activation temperature plays an important role in preparing super activated carbon with high pore volume.
[0054] Comparative Example 4
[0055] The process is basically the same as in Example 2, but a vacuum process is introduced every 80 minutes of activation. The test shows that the specific surface area of the material is 1600m 2 / g, the pore volume is 1.35ml / g, and the desalination capacity is 16mg / g. Combining Comparative Example 4 with Example 2, it can be seen that controlling the frequency of introducing negative pressure treatment plays an important role in preparing super activated carbon with high pore volume.
[0056] Comparative Example 5
[0057] The same as Example 2, but the N2-water vapor mixture in Example 2 is replaced by CO2 at the same pressure. The test shows that the specific surface area of the material is 1800m2 / g, the pore volume is 1.65ml / g, and the desalination capacity is 19mg / g. Combining Comparative Example 5 with Example 2, it can be seen that the type of gas in the activation process plays an important role in the preparation of super activated carbon with high pore volume.
[0058] Comparative Example 6
[0059] The same as Example 3, but the concentration of H3PO4 used is 35wt%. According to the test, the pore volume of the material is 2.37ml / g and the specific surface area is 2732m 2 / g, the desalination capacity is 38mg / g. Combining Comparative Example 6 with Example 3, it can be seen that the concentration of H3PO4 does not have a great effect on the preparation of super activated carbon with high pore volume, but when the concentration is low, the drying time to constant weight will be longer.
[0060] Example 4
[0061] A method for preparing super activated carbon for electric adsorption desalination can prepare activated carbon with high pore volume, and the specific steps include:
[0062] (1) H3PO4 with a concentration of 45 wt% was mixed with walnut shell powder, and then dried at 120°C to constant weight to obtain phosphoric acid-loaded nut shells containing 50 wt% pure H3PO4.
[0063] (2) The phosphoric acid-loaded fruit shells of step (1) are placed in a quartz boat and rapidly pushed into a tube furnace at 950° C. in a N2-water vapor flow at a pressure of 1.03 bar (the relative humidity of the flow at 25° C. is 93%). After constant temperature activation for 30 min, the flow is cut off, and the furnace tube is evacuated to a vacuum degree of 0.5 bar and maintained for 40 s. Thereafter, the N2-water vapor mixture is introduced again.
[0064] (3) Repeat the “ventilation-vacuuming” cycle 5 times until the activation time reaches 150 minutes.
[0065] (4) Finally, wash the sample to neutrality and dry it.
[0066] The specific surface area and pore volume of the material were obtained by nitrogen adsorption and desorption technology. In addition, the material was mixed with carbon black and PVDF in a mass ratio of 8:1:1 to make an electrode sheet, and its desalination performance was evaluated in a 1.2V, 500mg / L NaCl solution in a capacitive deionization device without an ion exchange membrane. It was found that the pore volume of the material was 2.40ml / g and the specific surface area was 2835m 2 / g, and the desalination capacity is 47mg / g.
[0067] Example 5
[0068] A method for preparing super activated carbon for electrosorption desalination, wherein each constant temperature activation time is 40 minutes, and "ventilation-vacuuming" is repeated 5 times until the activation time reaches 200 minutes.
[0069] The test shows that the pore volume of the material is 2.44ml / g and the specific surface area is 2893m 2 / g, and the desalination capacity is 55mg / g.
[0070] Other unmentioned places are the same as those in Example 4.
[0071] Example 6
[0072] A method for preparing super activated carbon for electrosorption desalination, wherein each constant temperature activation time is 40 minutes, and "ventilation-vacuuming" is repeated 6 times until the activation time reaches 240 minutes.
[0073] The test shows that the pore volume of the material is 2.47ml / g and the specific surface area is 2943m 2 / g, and the desalination capacity is 63mg / g.
[0074] Other unmentioned places are the same as those in Example 4.
[0075] Example 7
[0076] A method for preparing super activated carbon for electrosorption desalination, in which the carbon is rapidly pushed into a tubular furnace at 950°C in a N2-water vapor flow at a pressure of 1.03 bar (the relative humidity of the flow at 25°C is 95%), each constant temperature activation time is 50 minutes, and the "ventilation-vacuuming" cycle is repeated 6 times until the activation time reaches 300 minutes.
[0077] The test shows that the pore volume of the material is 2.50ml / g and the specific surface area is 2998m 2 / g, and the desalination capacity is 69mg / g.
[0078] Other unmentioned places are the same as those in Example 4.
[0079] The performances of the high pore volume super activated carbons prepared in Examples 1-7 and Comparative Examples 1-5 were compared, and the results are shown in Table 1.
[0080] Table 1 is the preparation conditions and performance comparison of the examples and comparative examples
[0081]
[0082]
[0083]
[0084] It can be seen from Table 1 that the relative humidity of the N2-water vapor flow used is greater than 90% (at 25°C) and as large as possible, the temperature of constant temperature activation is 950°C, and the number of "ventilation-vacuuming" cycles is 6 times. When the time reaches 300min, the pore volume of the prepared super activated carbon is the largest, which is 2.50ml / g, and the specific surface area can also reach nearly 3000m 2 / g, and the desalination capacity is also the largest. When the temperature of constant temperature activation exceeds 950℃, and / or the number of "ventilation-vacuuming" cycles exceeds 6 times, and / or the total activation time exceeds 300min, the pore volume and specific surface area will decrease, and the cost will also increase.
[0085] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.
Claims
1. A method for preparing super activated carbon for electrosorption desalination, using fruit shells as raw materials, immersing the fruit shells in an acid solution, and activating them at a constant temperature after drying, characterized in that: The steps include: (1) immersing the fruit shell in a phosphoric acid solution to obtain a mixture, and then drying to a constant weight to obtain a phosphoric acid-loaded fruit shell containing pure phosphoric acid; (2) The phosphoric acid-loaded fruit shells are quickly transferred to a tube furnace at 860-950°C in a N2-water vapor flow at a pressure of less than 1.2 bar, and activated at a constant temperature. After every 30-60 minutes of activation, the gas flow is cut off, and the furnace tube is evacuated to a vacuum degree greater than 0.4 bar and maintained for 30-180 seconds. After that, a mixture of N2-water vapor at a pressure of less than 1.2 bar is introduced again; wherein the relative humidity of the N2-water vapor flow at 25°C is greater than 90%; (3) After 3 to 6 "ventilation-vacuuming" cycles, until the activation time reaches 130 to 300 minutes; (4) After activation, the product is taken out, washed to neutrality, and then dried to obtain the super activated carbon; The super activated carbon has a pore volume of 2.15-2.5 ml / g and a specific surface area of 2290-3000 m 2 / g, and the electrosorption desalination capacity in 500mg / L NaCl solution at a voltage of 1.2V is 28-70mg / g.
2. The method for preparing super activated carbon for electrosorption desalination according to claim 1, characterized in that: The concentration of the phosphoric acid solution is 35-45 wt %.
3. The method for preparing super activated carbon for electrosorption desalination according to claim 1, characterized in that: The amount of desalination by electrosorption is measured by mixing activated carbon, carbon black and PVDF to make electrode sheets in an electrosorption desalination device that does not contain an ion exchange membrane.
4. The method for preparing super activated carbon for electrosorption desalination according to claim 1, characterized in that: In the step (1), the drying temperature is 100 to 120°C.
5. The method for preparing super activated carbon for electrosorption desalination according to claim 1, characterized in that: In the step (4), the product is washed with deionized water until it becomes neutral, and then dried in a drying oven at 40 to 60° C. to a constant weight.
6. The method for preparing super activated carbon for electrosorption desalination according to claim 1, characterized in that: During constant temperature activation, the temperature of the tube furnace is 950°C, and the gas flow is cut off every 50 minutes of activation, and 6 "ventilation-vacuuming" cycles are performed until the activation time reaches 300 minutes.