CN114715985A - Electrochemical desalination system constructed from mycelium-derived carbon - Google Patents

Abstract

The invention discloses an electrochemical desalination system constructed from mycelium-derived carbon, comprising a power source and a desalination unit, wherein the desalination unit includes an electrode tank, and the electrode tank is provided with a cathode and an anode, and the cathode and the anode are connected with each other. The active substances are all mycelium-derived carbon materials obtained by carbonization of the mycelium. The present invention first proposes a method for electrochemical desalination using fungal mycelium-derived carbon, which can greatly improve the desalination rate while increasing the desalination amount per unit mass, reduce the cycle period and time cost, and is beneficial to resource utilization and the environment Protect.

Description

An electrochemical desalination system constructed from mycelium-derived carbon

technical field

The invention relates to an electrochemical desalination system, in particular to an electrochemical desalination system constructed from mycelium-derived carbon.

Background technique

With the increase in human demand for fresh water, many desalination technologies have been adopted to solve the problem of fresh water supply. Widely used desalination technologies include membrane distillation, reverse osmosis, ion exchange and electrodialysis, all of which have certain disadvantages. Membrane distillation and reverse osmosis use thermal energy and pressure energy as desalination energy, and have high energy density; ion exchange and electrodialysis require expensive ion exchange membranes, and fragile membranes bring huge costs.

Capacitive deionization and desalination (CDI) is a technology that utilizes electric double-layer capacitor materials to electro-absorb salt ions in solution for desalination and desalination of seawater. CDI has traditionally relied on inexpensive activated carbon electrodes for desalination. Industrial activated carbon has uneven particles and low specific surface area, which seriously affects the desalination effect, and when working in an environment with high salinity and high voltage, activated carbon will also be corroded to a certain extent. The capacitive properties of CDI carbon-based materials directly affect the desalination effect. Good capacitive properties require high specific surface area, excellent hydrophilicity, high conductivity, fast ion adsorption response, and long-term stability. Therefore, it is necessary to develop a A simple and easy-to-prepare carbon material satisfies the above advantages.

Biochar is usually obtained by carbonizing biomass precursors at moderate temperatures (400-800°C). Biochar retains the original structure of biomass, but has poor porosity and low activity. Untreated biochar has only limited desalination performance. Biocarbon can form unique three-dimensional interconnected porous structures due to its easy chemical activation treatment. The modified derived carbon has the advantages of high specific surface area, large pore volume, and well-tailored pore size, and generally modified biocarbon contains various pore structures. Biochar itself contains nutrients and can form self-doping, and heteroatoms can improve the surface properties of carbon pores and form highly polar and hydrophilic centers. However, some biomass materials in organisms, due to their origin from functionalized different tissues, may not be conducive to the adsorption, desorption and transport processes of ions.

Compared with other technologies, the low desalination energy consumption of the CDI process is very advantageous, but to realize its industrial application, how to improve the desalination performance and desalination cycle speed of carbon materials is a big problem.

SUMMARY OF THE INVENTION

Purpose of the invention: The purpose of the present invention is to provide an electrochemical desalination system constructed from mycelium-derived carbon, which can greatly improve the desalination speed and reduce the cycle period and time cost.

Technical solution: The electrochemical desalination system constructed from mycelium-derived carbon according to the present invention includes a power source and a desalination unit, and the desalination unit includes an electrode tank, and the electrode tank is provided with a cathode and an anode, and the cathode and the The active materials of the anode are all mycelium-derived carbon materials obtained by carbonization of the mycelium.

Wherein, the electrochemical desalination system constructed by the mycelium-derived carbon further includes a conveying mechanism for conveying the brine solution to be desalinated into the electrode tank; the conveying mechanism is preferably a conveying pump; the power source is preferably a constant pressure power supply. The cathode and the anode are arranged in parallel in the electrode tank, a separator is placed between the cathode and the anode, and a separator can also be arranged between the cathode and the anode if necessary. Technical assembly can be done. The electrode tank is provided with a water inlet and a water outlet. The brine solution and the electrode tank form a loop, the liquid flow pipe is connected to the water inlet and the water outlet of the electrode tank, and the other two ends of the liquid flow pipe are respectively connected to the conveying mechanism and the brine solution. The anode and the cathode are respectively connected with the positive and negative electrodes of the constant voltage power supply. The area of the cathode and the anode is preferably 10cm×10cm, and the distance between the electrodes is preferably 1cm; the flow rate of the saline solution and the flow in the electrode tank is 10-50mL min ^-1 . The electrolyte in the electrode tank is a brine solution that needs to be desalinated; specifically, it can be a high-concentration NaCl solution or a mixture of Na ⁺ , Pb ²⁺ , Cu ²⁺ , Fe ³⁺ , Cr ³⁺ , Cl ^- , SO ₄ ^2- , PO ₄ ^3- A soluble matter solution composed of any two or more ions; the concentration of the brine fed in is preferably 200-5000 mg/L; the applied voltage is preferably 0.8-1.4V, more preferably 1.0-1.4V.

Wherein, after the mycelium is carbonized, it is prepared by making pores with a pore-forming agent; wherein, the processes of carbonization and pore-making are carried out in an inert atmosphere.

The specific steps for preparing the mycelium-derived carbon material are: carbonizing the mycelium powder under an inert atmosphere of 300-600° C. for 1.5-5 hours to obtain the mycelium carbon powder; mixing the mycelium carbon powder with a pore-forming agent Mixed, activated under an inert atmosphere of 650-900° C. for 2-5 hours, washed and dried to obtain a mycelium-derived carbon material. Wherein, the mass ratio of the pore-forming agent and the carbonized mycelium is 2:1-8:1, more preferably 2:1-5:1; the carbonization temperature is 300-600°C, and the time is 1.5-5h, The carbonization temperature is more preferably 500-600°C; the activation temperature is 650-900°C, the time is 2-5h, and the activation temperature is more preferably 700-900°C. The quality of the mycelium-derived carbon material accounts for 10% to 30% of the total quality of the precursor mycelium.

Wherein, the mycelium is Ganoderma lucidum, enoki mushroom, slip mushroom, black fungus, white fungus, straw mushroom, red mushroom, ghost umbrella, mushroom, thunder mushroom, pine mushroom, fly mushroom, bolete, honey fungus, tuckahoe, One of Porcine or Lei Wan.

Wherein, the mycelium is collected from the field, discarded strains from the farm, or grown by artificial culture, and the artificial culture refers to being obtained from sporophyte culture.

The steps of obtaining mycelium by sporophyte culture are:

(1) obtain sporophyte, make sporophyte suspension; put sporophyte suspension into potato dextrose agar medium and cultivate; the nutrients in described potato dextrose agar medium include: peptone, sucrose, yeast extract, Phosphates, magnesium salts, vitamins, ammonium salts;

(2) The first stage: the culture medium is placed on a rotating vibrating sieve for 6 to 9 days;

(3) Second stage: Mix a small amount of fermentation broth obtained in the first stage with the initial sporophyte suspension in a mass ratio of 1:7 to 1:9, and cultivate for 3-6 in the same environment as the first stage. After washing and drying, the mycelial membrane was obtained.

Wherein, in step (1), the pH value of the adjustment medium is 5.5-6.5; the content of peptone is 3-20 g L ^-1 ; the content of sucrose is 15-50 g L ^-1 ; yeast extract, phosphate, magnesium salt The content of vitamin C is 0.5～5g L ^-1 respectively; the content of vitamin is 0.01～0.10g L ^-1 ; the content of ammonium salt is 1～10g L ^-1 . Among them, the vitamin is preferably vitamin B1; the ammonium salt can be replaced by glutamic acid; the phosphate can be replaced by monohydrogen phosphate and dihydrogen phosphate.

In step (3), the mycelium mycelium membrane obtained after cultivation is cut into small pieces or small pieces, washed, dried and then pulverized to obtain mycelium powder, which is used for later use.

The steps for preparing cathode and anode from mycelium-derived carbon material are:

The mycelium-derived carbon material is mixed with a binder, a conductive agent and an organic solvent to prepare a slurry, and the slurry is coated on a conductive substrate and dried. Among them, the mass ratio of mycelium-derived carbon, binder and conductive agent is 8:1:1; the binder is polyvinylidene fluoride, polytetrafluoroethylene or cation exchange membrane; the conductive agent is acetylene black or carbon black ; Conductive matrix is titanium mesh, titanium foam, carbon paper or carbon cloth.

Principle: The CDI process performance based on electric double layer capacitance depends on the carbon pore properties, interconnected structure, surface properties and large specific surface area of carbon materials. The present invention adopts targeted thinking to find carbon materials suitable for CDI process, and mycelium is the organ that transmits substances and transports nutrients in fungal strains, just like the CDI process of migrating and adsorbing ions in industrial applications. For the mycelium biochar system, the present invention optimizes the pore structure and surface properties through various means. It mainly includes the following points:

(1) Desalination of CDI using the naturally endowed mycelium transport system, the natural biological transport organ has higher-order structures that are difficult to synthesize by conventional chemical methods; (2) A mycelium culture method is proposed, using a shake flask- Two-step growth of mycelia in static culture. In the process of shaking the flask, the mycelium of Ganoderma lucidum is intertwined and gradually cross-linked from a spherical dispersion into a fibrous mesh-like mycelial film; (3) The synthesis is guided by the characteristics of carbon materials required by the CDI process to prepare mycelium In the process of deriving carbon, there is a high nitrogen culture and micropore forming process, which optimizes the surface properties and specific surface area.

It is precisely because of the above design points that the structure from the biological top layer confers the advantages of the mycelium-derived carbon CDI system in desalination. The abundant connected pore structure is conducive to the transmission of liquid flow in the carbon matrix and accelerates the migration of ions; the ultra-high specific surface area provides a sufficient number of microporous adsorption sites, and ions are easily captured by the carbon pores; high nitrogen atom doping The properties make the carbon surface more fully in contact with the liquid, strengthen the ion anchoring, and the mycelium-derived carbon itself has good electrical conductivity. During the electrochemical adsorption process, the transport behavior of both ions and electrons has been greatly optimized, so the mycelium-derived carbon system has an ultra-high salt adsorption rate (up to 12.31 mg g ^-1 min ^-1 , which is the highest in general carbon materials). three times), the saturated adsorption capacity is also significantly increased. In the patent CN111087054A, bio-straw-derived carbon is used as the active material of CDI. Since ordinary straw does not have the above-mentioned characteristics and advantages, its saturated adsorption capacity is maintained at the level of 10.65 mg g ^-1 , which is slightly higher than that of commercial activated carbon and mycelium. The bulk-derived carbon CDI system can achieve a high saturation adsorption capacity of 24.20 mg g ^-1 under similar conditions.

Beneficial effects: Compared with the prior art, the present invention achieves the following remarkable effects: (1) The present invention proposes for the first time a method for electrochemical desalination using the mycelium of fungi, which can greatly increase the desalination amount per unit mass while improving the desalination amount per unit mass. The desalination speed is increased, the cycle period and time cost are reduced, and it is beneficial to resource utilization and environmental protection. (2) The mycelium-derived carbon was used as the active electrode of the CDI desalination system, and the CDI desalination system was established through the electric double layer capacitance of the carbon mesh, which could be used to remove salt ions in water. (3) Mycelium is easy to adsorb metal ions in soil, and the formed mycelium-derived carbon possesses an intertwined network to transport water or ions, which is suitable for CDI applications. (4) Mycelium-derived carbon is a natural ion transport system, and its ability to remove salt ions is more than twice that of commercial activated carbon electrodes, and the highest removal rate of salt ions can reach more than four times. (5) The device in the present invention is simple and novel in construction, low in cost, easy to implement, and can well achieve desalination effect. (6) Mycelium is different from the edible part of fungi, which generally exists underground and has no production and use value in industry. Using waste mycelium as the active material of electrodes for electrochemical desalination will be an effective way to help resource utilization and improve quality and efficiency.

Description of drawings

Figure 1 is the electrochemical desalination cycle system shown in Example 1;

Fig. 2 is the photograph of the mycelium membrane of embodiment 1;

Fig. 3 is the SEM image of the mycelium powder after the mycelium film of Example 1 is pulverized;

4 is a SEM image of the mycelium-derived carbon material of Example 1;

5 is a TEM image of the mycelium-derived carbon material of Example 1;

Figure 6 is the desalination cycle curve obtained in Example 1, the conductivity records the concentration change of the solution, and the current shows the response of the desalination system under the applied voltage;

Fig. 7 is the desalination capacity curve of the mycelium-derived carbon CDI system and the commercial activated carbon CDI system of Example 1;

Fig. 8 is the desalination rate curve of the mycelium-derived carbon CDI system of Example 1 and the commercial activated carbon CDI system;

Figure 9 is the desalination capacity curve indicated by groups 1 to 3 in Table 1;

Figure 10 is the desalination capacity curve indicated by groups 3 to 5 in Table 1;

11 is the saturated adsorption capacity curve of the mycelium-derived carbon electrode under different sodium chloride concentrations of Example 1.

Detailed ways

The present invention will be described in further detail below.

Example 1

As shown in FIG. 1 , the present invention provides an electrochemical desalination system constructed from mycelium-derived carbon, including a power source, a desalination unit, and a conveying mechanism for conveying the brine solution to be desalinated into the desalination unit. The power supply in this embodiment is a constant voltage power supply. The desalination unit of this embodiment includes an electrode tank, and the electrode tank is provided with a cathode and an anode that are parallel to each other, and the active materials of the cathode and the anode are both mycelium-derived carbon materials. The cathode and the anode are fixed by a separator, the separator is a frame structure, and the thickness of the separator is approximately the distance between the two electrodes, which is 1 cm in this embodiment; a separator is arranged in the middle of the frame to prevent short circuit. The separator in this embodiment is a silicon-based separator, and the conveying mechanism is a peristaltic pump. The area of both the cathode and the anode is 10 cm x 10 cm. The flow tube is connected to the electrode tank and peristaltic pump.

The mycelium-derived carbon material in this embodiment is prepared by carbonizing the mycelium and then pore-forming with a pore-forming agent. Among them, the mycelium is obtained by culturing the sporophyte of Ganoderma lucidum. The specific steps are as follows:

(1) Place the sporophyte suspension of Ganoderma lucidum on potato dextrose agar medium, add 5g L ^-1 peptone, 35g L ^-1 sucrose, 2.5g L ^-1 yeast extract, 1g L ^- 1 to the medium ¹ KH ₂ PO ₄ , 0.5 g L ^-1 MgSO ₄ , 0.05 g L ^-1 vitamin B1 and 5 g L ^-1 (NH ₄ ) ₂ SO ₄ , adjust the pH to 6;

The first stage: the culture medium is placed on a rotary vibrating sieve at 28°C, the rotation speed is set to 150rpm, and the culture period is 7 days;

The second stage: Mix a small amount of the fermentation broth obtained in the first stage with the initial mycelium suspension, the mass ratio is 1:9, and cultivate for 5 days under the same environment. After 12 days of culture, the grown mycelium membrane was washed three times with distilled water, then cut into small pieces, washed with water to clean the surface dirt, dried at 60 °C, and mechanically pulverized after drying to obtain micron-sized mycelium. powder;

(2) carbonizing the obtained mycelium powder at 500°C for 2 h to obtain the mycelium carbon powder;

(3) Mix KOH and mycelium carbon powder in a mass ratio of 4:1, activate under a nitrogen atmosphere at 800°C for 3 h, wash the product and dry at 60°C to obtain a mycelium-derived carbon material, that is, For the active material, denoted as C500A800K4.

The preparation method of the cathode and anode of the present embodiment includes the following steps:

The mycelium-derived carbon material, binder and conductive agent were mixed and added to the polyvinylpyrrolidone solvent in a mass ratio of 8:1:1. After ultrasonication for 10 min, a slurry was prepared, which was evenly drop-coated on the carbon fiber felt. After drying at ℃, the mycelium-derived carbon electrodes were obtained, which were used as cathode and anode, respectively. The binder in this embodiment is polyvinylidene fluoride, and the conductive agent is acetylene black.

The mycelium film obtained by the culture method of the present application is shown in Figure 2, and the micron-scale mycelium powder is shown in Figure 3. It can be seen that the mycelium in the mycelium film has multiple antennae, which is unique. The structure of the mycelium makes the antennae connected with each other after carbonization of the mycelium, forming a three-dimensional connected network structure.

The morphologies of the mycelium-derived carbon materials are shown in Figures 4 and 5. Figure 4 is the SEM image of the mycelium-derived carbon material prepared by this method. It can be observed that the mycelium is composed of carbon tubes, and these tubular filaments are intertwined to form a three-dimensionally connected ion transport network. Figure 5 is a TEM image of the mycelium-derived carbon material prepared by this method. It can be seen that the outer diameter of the tubular structure is 600 nm, and the inner hollow hole is 150-200 nm. There are many pores of 50-100 nm on the tube wall.

Desalination process:

500mg L ^-1 of NaCl salt solution was poured into the whole system, and the parameters of the peristaltic pump were adjusted to make the liquid flow rate 20ml min ^-1 , and the solution circulated in the whole system to form an electrochemical desalination system. As shown in Figure 6, the circuit was turned on, and voltage was applied to the two electrodes of the desalination unit, and the electrochemical desalination system was subjected to ion adsorption cycles under constant voltage reaction conditions. During the three cycles, the voltage was set to 0.8 V, 1.0V, 1.2V, after the voltage is applied, the cathode cell begins to adsorb sodium ions in the solution, and the anode cell adsorbs chloride ions. As the ions are collected on the electrode, the solution concentration in the circulating system decreases, and the conductivity decreases. When the power supply is disconnected, the anode and cathode discharge ions, the concentration of the solution increases, and the conductivity increases. Repeating the above process can realize the purification of brine and the enrichment cycle of ions. Figures 7 and 8 show the comparison of desalination capacity and desalination rate between mycelium-derived carbon and commercial activated carbon, respectively. Mycelium-derived carbon showed a saturated adsorption capacity of 24.20 mg g ^-1 and 12.31 mg g ^-1 min. The highest salt adsorption rate of ^-1 , compared to the performance of commercial activated carbon of only 9.58 mg g ^-1 and 2.54 mg g ^{- 1} min ^-1 .

In order to test the effect of desalination under different voltages, the voltages were set to 1.0V, 1.2V, and 1.4V in turn, and the brine concentration was kept at 500 mg L ^-1 . The specific parameters are shown in Table 1; The concentration was set to 500 mg L ^-1 , 200 mg L ^-1 , and 800 mg L ^-1 in turn, and the holding voltage was 1.4 V. The specific parameters are shown in Table 1. The test data obtained by the above-mentioned test groups with different voltages and different brine concentrations are shown in Figure 9 and Figure 10. The ordinate in Figure 9 is the mass of the salt that can be adsorbed by the active substance per unit mass, and the highest value represents the saturated adsorption capacity; this The mycelium-derived carbon CDI system of the embodiment has a saturated adsorption capacity of 28.2, 24.0 and 17.3 mg g ^{- 1} in solutions of 1.4 V, 800, 500 and 200 mg L-1, respectively, and at 500 mg L ^-1 , 1.4, 1.2 and At a voltage of 1.0 V, the saturated adsorption amounts were 24.2, 20.1 and 16.0 mg g ^-1 , respectively.

Fig. 11 shows the saturated adsorption capacity curves of this example under different sodium chloride solutions, which shows that the CDI system can be loaded with a voltage of 0.8V-1.4V, and the brine concentration range for desalination can be controlled within 200mg L ^-1 -5000mg L ^{- 1} .

Table 1

group Operating voltage (V) Saline concentration (mg/L) 1 1.0 500 2 1.2 500 3 1.4 500 4 1.4 200 5 1.4 800

Example 2

On the basis of Example 1, the difference from Example 1 is that carbonization at 600°C, activation of pores at 800°C, where the mass ratio of KOH and mycelium powder is 4:1; the product is denoted as C600A800K4.

Example 3

On the basis of Example 1, the difference from Example 1 is that carbonization at 500°C, activation of pores at 700°C, where the mass ratio of KOH and mycelium powder is 4:1; the product is denoted as C500A700K4.

Example 4

On the basis of Example 1, the difference from Example 1 is that carbonization at 500°C, activation of pores at 900°C, where the mass ratio of KOH and mycelium powder is 4:1; the product is denoted as C500A900K4.

Example 5

On the basis of Example 1, the difference from Example 1 is that carbonization at 500°C, activation of pores at 800°C, where the mass ratio of KOH and mycelium powder is 2:1; the product is denoted as C500A800K2.

Example 6

On the basis of Example 1, the difference from Example 1 is that carbonization at 500°C, activation of pores at 800°C, where the mass ratio of KOH and mycelium powder is 5:1; the product is denoted as C500A800K5.

The performance of the CDI system mainly depends on the surface area, pore structure and capacitive properties. Relevant tests were carried out on the mycelium-derived carbon materials of Examples 1-6, and the test results of commercial activated carbon charcoal were given, as shown in Table 2 below.

Table 2 lists the performance parameters of carbonization at 500 to 600 °C, pore formation at 700 to 900 °C, and the mass ratio of KOH to carbon at 2:1 to 5:1. The saturated adsorption capacity was measured at 1.4V and 500mg L ^-1 of sodium chloride solution, and the mycelium-derived carbon materials obtained in Examples 1-6 all had a desalination effect far higher than that of commercial activated carbon. Generally speaking, the carbonization temperature has little effect on the performance. Too high pore-forming temperature and too high KOH addition will increase the degree of reaction between the surface of the mycelium carbon and KOH, and the micropore volume will decrease and the average pore size will increase. . Low pore-forming temperature and KOH addition may make the reaction incomplete. The test data in Table 2 shows that the mycelium-derived carbon material of the present invention is a good molding template, can easily obtain a connected structure with high specific surface area, and is suitable for CDI desalination.

Table 2

Claims (10)

1. An electrochemical desalination system constructed by mycelium-derived carbon comprises a power supply and a desalination unit, wherein the desalination unit comprises an electrode tank, and a cathode and an anode are arranged in the electrode tank.

2. The electrochemical desalination system constructed from mycelium-derived carbon according to claim 1, wherein the mycelium-derived carbon material is prepared by carbonizing mycelium and then forming pores with a pore-forming agent.

3. The electrochemical desalination system constructed from mycelium-derived carbon according to claim 1, wherein the mycelium in the mycelium-derived carbon material is obtained by direct collection or culture of sporophytes.

4. The electrochemical desalination system constructed from mycelium-derived carbon according to claim 1, wherein the mycelium of the mycelium-derived carbon material is one of ganoderma lucidum, flammulina velutipes, pholiota nameko, black fungus, tremella, volvariella volvacea, coprinus comatus, tricholoma matsutake, toad, boletus, armillaria mellea, poria cocos, polyporus umbellatus, or omphalia.

5. The electrochemical desalination system constructed from mycelium-derived carbon according to claim 2, wherein the mass ratio of the pore-forming agent to the carbonized mycelium is 2:1 to 8: 1.

6. The electrochemical desalination system constructed from mycelium-derived carbon according to claim 1, wherein the carbonization temperature is 300 to 600 ℃ for 1.5 to 5 hours.

7. The electrochemical desalination system constructed from mycelium-derived carbon according to claim 2, wherein the pore-forming temperature is 650 ℃ to 900 ℃ for 2 to 5 hours.

8. The electrochemical desalination system constructed from mycelium-derived carbon according to claim 3, wherein the mycelium is obtained by culturing sporozoites by the steps of:

(1) obtaining sporophytes to prepare a sporophyte suspension; culturing the sporophyte suspension in potato glucose agar culture medium; the nutrient substances in the potato dextrose agar culture medium comprise: peptone, sucrose, yeast extract, phosphate, magnesium salt, vitamins, ammonium salt;

(2) the first stage is as follows: placing the culture medium on a rotary vibrating screen for culturing;

(3) and a second stage: and mixing the fermentation liquor obtained in the first stage with the initial sporophyte suspension according to the mass ratio of 1: 7-1: 9, culturing in the same environment as that of the first stage to obtain a mycelium membrane, and crushing to obtain mycelium powder.

9. The electrochemical desalination system constructed from mycelium-derived carbon according to claim 8, wherein the peptone is contained in an amount of 3 to 20g L in the step (1)^-1(ii) a The content of the sucrose is 15-50 g L^-1(ii) a The contents of yeast extract, phosphate and magnesium salt are respectively 0.5-5 g L^-1(ii) a The content of the vitamin is 0.01-0.10 g L^-1(ii) a The content of ammonium salt is 1-10 g L^-1。

10. The electrochemical desalination system constructed by mycelium-derived carbon according to claim 8, wherein the first stage of the culturing in the step (2) is performed for 6 to 9 days; in step (3), the second stage culture is carried out for 3-6 days.

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