Method for improving desalination capacity of porous carbon capacitor

Abstract

The present application relates to a kind of porous carbon capacity desalination quantity promotion method.Specific scheme includes: the water with electric conductivity ≤200 μS / cm is fully immersed porous carbon, then water-porous carbon system is cooled to 0~‑20 ℃ under ≤1 atm absolute pressure and freezes, finally, it is dried quickly.This method can make the capacity desalination quantity of porous carbon increase 1%~10%, and does not need to consume chemical reagent, longer time or higher energy consumption.

Description

Technical Field

[0001] This invention relates to a method for improving the desalination performance of porous carbon used in capacitor desalination, and therefore belongs to the fields of energy conservation and environmental protection as well as new materials. Background Technology

[0002] Capacitive desalination technology, based on the principle of electric double layer, is considered the most promising next-generation desalination technology. The commonly used electrode material for this technology is porous carbon, which offers advantages over Faraday materials and metal-organic frameworks, including abundant porosity, significantly improved conductivity, tunable surface properties, good stability, and low cost. However, the desalination capacity of this material urgently needs improvement.

[0003] To improve the desalination capacity of porous carbon, doping, compounding with other components, and adding ion exchange membranes can be employed. Compared to these methods, secondary activation of porous carbon offers advantages such as not reducing pore volume, ease of control, and low cost. However, activation often requires heating the carbon source or reagents (such as KOH, CO2, or steam) to high temperatures (500-900°C) followed by cooling, resulting in drawbacks such as long activation time, high reagent consumption, thermal risks, and high energy consumption. Therefore, developing new methods to improve the desalination performance of porous carbon is of significant importance.

[0004] Based on the above background, this invention proposes a method for improving the desalination performance of porous carbon capacitors based on cryogenic activation. This method has advantages such as no consumption of reagents, no thermal risk, and short processing time, and can improve the desalination performance by 1% to 10%. Summary of the Invention

[0005] This invention provides a method for increasing the desalination capacity of porous carbon capacitors, aiming to increase the desalination capacity of porous carbon without consuming reagents, taking a long time, or consuming a large amount of energy.

[0006] The technical solution involves the following steps: fully immersing porous carbon in water with a conductivity of ≤200μS / cm, then cooling both materials to 0 ~ -20℃ under an air pressure of ≤1atm to freeze the water into ice, followed by rapid drying, thereby increasing the desalination capacity of the porous carbon by 1%~10%.

[0007] The term ≤1atm refers to the absolute pressure of the gas above the porous carbon-water system not exceeding 1atm.

[0008] The water has a pH value between 6.5 and 7.5 at 25°C.

[0009] The freezing process refers to the freezing time being ≥20 minutes.

[0010] The drying process refers to the use of negative pressure, forced air, microwave heating, or filtration dehydration during the drying process.

[0011] The drying process refers to reducing the moisture content of porous carbon to ≤0.5wt% at a drying temperature of ≤250℃.

[0012] The desalination amount refers to the equilibrium desalination amount of porous carbon made into carbon electrode sheets, measured at 1.2V in a 500mg / L NaCl aqueous solution.

[0013] Due to the adoption of the above technical solutions, the beneficial technical effects of the present invention are as follows: 1. This invention can increase the desalination capacity of porous carbon by 1% to 10% without the need for chemical reagents, long time or high energy consumption. Detailed Implementation

[0014] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Based on the embodiments in this application, other similar embodiments obtained by those skilled in the art without creative effort should all fall within the scope of protection of this application.

[0015] Example 1 5g of dried commercial activated carbon (a porous carbon) was added to 15mL of water with a conductivity of 27μS / cm and a pH of 6.8. After stirring for 1 hour, no bubbles were observed to be generated. The mixture was then cooled to -1℃ under an absolute pressure of 1 atm to allow the water to fully freeze, and this process was maintained for at least 30 minutes. The mixture was then heated to melt, filtered, and dried at 105℃ using forced air drying to obtain modified porous carbon with a water content of 0.1wt%. Tests showed that the porous carbon exhibited a 9% increase in desalination capacity in a 1.2V, 500mg / L NaCl solution, increasing the desalination capacity from 14.65mg / g to 15.82mg / g.

[0016] Comparative Example 1 The implementation steps were basically the same as in Example 1, except that the conductivity of the water used was 1040 μS / cm. The study found that the desalination rate under these conditions was 0%, lower than in Example 1, indicating that the conductivity of the chilled water affects the modification effect, and that lower conductivity of the water is beneficial for increasing the desalination rate.

[0017] Comparative Example 2 The implementation steps were basically the same as in Example 1, except that as much as 43g of porous carbon was added, resulting in the porous carbon not being completely submerged in water. The study found that the desalination rate of the porous carbon under this condition was 0%, lower than that in Example 1, indicating that the submersion state of the porous carbon before freezing can affect the desalination rate. To achieve a good improvement effect, it is necessary to completely submerge the porous carbon.

[0018] Comparative Example 3 The implementation steps are basically the same as in Example 1, except that the gas pressure during cooling is 3 atm. The study found that the desalination rate increase under this condition was lower than in Example 1, indicating that the gas pressure during cooling and freezing affects the desalination rate increase.

[0019] Comparative Example 4 The implementation steps are basically the same as in Example 1, except that the freezing temperature is lowered to -25°C. The study found that the desalination rate increase under this condition was only 2.1%, lower than in Example 1, indicating that the lowest freezing temperature used has an impact on the desalination rate increase, and excessively low temperatures are not conducive to increasing the desalination rate.

[0020] Comparative Example 5 The implementation steps were basically the same as in Example 1, except that the frozen activated carbon-ice mixture was dried at 42°C without ventilation and without filtration to remove water. The study found that the desalination rate increase under these conditions was 3.5%, lower than in Example 1, indicating that the drying method affects the desalination rate increase; a faster drying rate is beneficial for increasing the desalination rate.

[0021] Example 2 5g of dried commercial activated carbon (a porous carbon) was added to 15mL of water with a conductivity of 27μS / cm and a pH of 6.8. After stirring for 1.5h, no bubbles were observed to form. The mixture was then cooled to -2℃ under an absolute pressure of 1atm and maintained for at least 40min to allow the water to fully freeze. Subsequently, the mixture was freeze-dried under an absolute pressure of 100Pa until the water content was <0.2%, yielding the modified porous carbon. Tests showed that the porous carbon exhibited a 5.6% increase in desalination capacity in a 1.2V, 500mg / L NaCl solution compared to the unmodified version.

[0022] Table 1. Explanation of Embodiments and Comparative Examples of the Invention Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for increasing the desalination capacity of porous carbon capacitors, characterized in that, The following steps were adopted: porous carbon was immersed in water with an electrical conductivity of ≤200μS / cm, and then both were cooled to 0 ~ -20℃ under an air pressure of ≤1atm and maintained for ≥20min to make the water solid, and then dried. The ≤1atm mentioned above means that the absolute pressure of the gas above the porous carbon-water mixture does not exceed 1atm; The immersion refers to a contact time of 10 to 300 minutes between porous carbon and water, during which the porous carbon in the water does not produce bubbles.

2. The method according to claim 1, characterized in that, The water has a pH value between 6.5 and 7.5 at 25°C.

3. The method according to claim 1, characterized in that, The drying process refers to the use of negative pressure, forced air, microwave heating, or filtration dehydration during the drying process.

4. The method according to claim 1, characterized in that, The drying process refers to reducing the moisture content of porous carbon to ≤0.5wt% at a drying temperature of ≤250℃.

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