Application of microalgae carbon as particle electrode in flow electrode capacitive desalination

Abstract

The present invention discloses an application of microalgae carbon as a particle electrode in flow electrode capacitive desalination. The preparation method of the microalgae carbon comprises the following steps: heating the microalgae particles to 600-1000°C at a heating rate of 1-10°C / min under vacuum conditions, and keeping the temperature for 2-10 hours, cooling, washing, and drying to obtain the microalgae carbon. The present invention converts microalgae into microalgae carbon and uses it in a flow electrode capacitive desalination device, which has a higher desalination efficiency than an activated carbon particle electrode.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to an application of microalgae carbon as a particle electrode in mobile electrode capacitive desalination. Background Art

[0002] Wastewater desalination technology is an important part of wastewater treatment. High-salt wastewater can corrode pipelines and equipment and cause land salinization. High-salt wastewater has a strong inhibitory effect on microorganisms. Traditional wastewater biological treatment processes are difficult to effectively treat high-salt wastewater. Traditional physical and chemical desalination technologies such as reverse osmosis and adsorption are costly and inefficient. The entire industry is in urgent need of new wastewater desalination technologies. In addition, low-cost desalination technology can also be applied to seawater desalination to alleviate the problem of insufficient fresh water.

[0003] Capacitive desalination technology has the advantages of easy operation, low energy consumption, and small footprint, but the treatment efficiency still needs to be further improved. The limited electrode area is one of the important factors that limit its efficiency. To address this problem, mobile electrode capacitive desalination technology came into being. The anode pool / wastewater pool / cathode pool is formed by using anion and cation membranes, and granular activated carbon is added to the anode pool and cathode pool to form a plasma. This mobile electrode capacitive desalination technology shows better desalination efficiency than traditional capacitive desalination technology. Among them, granular activated carbon, as the core component of the plasma, occupies an important position. However, the conductivity of activated carbon particles is insufficient, and the adsorption of salt ions on the surface is low, which makes this direction urgently need cheap and efficient granular electrodes to further improve performance. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide an application of microalgae carbon as a particle electrode in flowing electrode capacitive desalination, converting microalgae into microalgae carbon and using it in a flowing electrode capacitive desalination device, which has a higher desalination efficiency than activated carbon particle electrodes.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The invention discloses an application of microalgae carbon as a particle electrode in mobile electrode capacitive desalination. The preparation method of the microalgae carbon comprises the following steps: heating the microalgae particles to 600-1000°C at a heating rate of 1-10°C / min under vacuum conditions, and keeping the temperature for 2-10 hours, cooling, washing and drying to obtain the microalgae carbon.

[0007] As a preferred technical solution, the microalgae particles are a mixture of one or more microalgae belonging to the phylum Cyanobacteria, Chlorophyta, Chrysophyta and Rhodophyta.

[0008] As a preferred technical solution, the microalgae particles are most preferably Chlorella.

[0009] As a preferred technical solution, the vacuum condition refers to an air pressure less than 10Pa.

[0010] As a preferred technical solution, the temperature condition is preferably increased to 1000°C.

[0011] As a preferred technical solution, the microalgae carbon is used as a particle electrode, and an electrolyte is added to form a microalgae carbon plasma; then the microalgae carbon plasma is placed in the anode pool and / or cathode pool of a flowing electrode capacitive desalination device, and a voltage is applied to the flowing electrode capacitive desalination device to desalinate the wastewater.

[0012] As a preferred technical solution, the mass fraction of the microalgae carbon in the microalgae carbon plasma is 5% to 20%.

[0013] As a preferred technical solution, the voltage applied to the mobile electrode capacitive desalination device is in the range of 1 to 5V.

[0014] The beneficial effects of the present invention are:

[0015] The present invention finds that due to the small size of microalgae, rich microscale undulating structure, and rich nitrogen and phosphorus elements, the microalgae can be carbonized under vacuum conditions to convert the microalgae into microalgae carbon, a carbon material with a micro-size structure, doped with nitrogen and phosphorus elements, and having a certain conductivity.

[0016] The vacuum high-temperature carbonization process makes the microalgae carbon have a high degree of graphitization. Since the conductivity of carbon materials comes from the conjugated π electron transfer of sp2 hybridized carbon (i.e. graphitic carbon), the high degree of graphitization will make it have a relatively high conductivity. At the same time, the vacuum carbonization process promotes the in-situ doping of the high concentration of nitrogen and phosphorus elements contained in the microalgae carbon itself, which are embedded in the carbon material in the form of bonding. When nitrogen, phosphorus and other elements with different electronegativity from carbon atoms are doped into the carbon material, the electron cloud polarization will occur near the doping site, and the electron density will be unevenly distributed, which usually enhances its surface binding ability with different ions, thereby enhancing its adsorption capacity for ions and increasing the adsorption amount. Therefore, using microalgae carbon instead of activated carbon as a particle electrode in a flow electrode capacitor desalination device has a higher desalination efficiency than activated carbon particle electrodes.

[0017] At the same time, microalgae are widely distributed around the world and reproduce rapidly. In particular, microalgae that reproduce excessively after algal blooms occur in water bodies are typical waste that needs to be treated. Therefore, using microalgae as raw materials has both cost and environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to make the purpose, technical solution and beneficial effects of the present invention clearer, the present invention provides the following drawings for illustration:

[0019] Figure 1 Schematic diagram of the mobile electrode capacitive desalination device.

[0020] Figure 2 XRD patterns of microalgae carbon obtained by vacuum carbonization of microalgae at 600℃, 800℃ and 1000℃.

[0021] Figure 3 TEM images of microalgae carbon obtained by vacuum carbonization of microalgae at 600℃, 800℃ and 1000℃.

[0022] Figure 4 XPS graphs of microalgae carbon obtained by vacuum carbonization of microalgae at 600℃, 800℃ and 1000℃. DETAILED DESCRIPTION

[0023] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0024] The activated carbon particles used in the following examples and comparative examples are activated carbon prepared from coal powder as raw material, and the particle size is 0.2-0.5 mm.

[0025] The mobile electrode capacitor desalination device used in the present invention is as follows Figure 1 As shown, the device can be divided into an anode pool / wastewater pool / cathode pool, with an anion exchange membrane separating the anode pool from the wastewater pool, and a cation exchange membrane separating the wastewater pool from the cathode pool. Based on this structure, when a positive voltage is applied to one side of the anode pool, the anions in the wastewater pool will be concentrated to the anode pool through the anion exchange membrane under the action of the electric field, while the cations in the anode pool are driven by the electric field to move toward the wastewater pool, but cannot enter the wastewater pool because they cannot pass through the anion exchange membrane. The principle is the same on the cathode pool side. The plasma of the anode pool and the cathode pool can circulate and receive the separated ions. In this way, the anions and cations in the wastewater pool can be continuously separated to the anode pool and the cathode pool on both sides to achieve desalination.

[0026] Example 1

[0027] (1) Preparation of microalgae carbon AMC-600 carbonized at 600℃

[0028] Weigh 100 g of dried Chlorella, raise the temperature to 600°C at a rate of 5°C / min and keep it for 2 hours under vacuum conditions with an air pressure of less than 10 Pa, then cool it down, wash and dry the obtained solid, and name it AMC-600.

[0029] (2) Prepare anode plasma and perform desalination treatment

[0030] Weigh 5g of AMC-600 sample and add it to 95mL of 0.1mol / L sodium sulfate solution to prepare the anode plasma (mass fraction 5%). Weigh 5g of activated carbon particles and add it to 95mL of 0.1mol / L sodium sulfate solution to prepare the cathode plasma. Figure 1 The assembled flow electrode capacitive desalination device is shown, with a sodium chloride solution with an initial concentration of 500 mg / L as the water to be treated. The circulation flow rate of the anode pool and the cathode pool is 30 mL / min, and the flow rate of the wastewater pool is 30 mL / min. The anode pool is connected to the positive pole of the voltage-stabilized power supply, and a voltage of 1.5 V is applied to achieve desalination of the water to be treated.

[0031] Example 2

[0032] (1) Preparation of microalgae carbon AMC-800 carbonized at 800℃

[0033] Weigh 100 g of dried Chlorella, and under vacuum conditions with an air pressure of less than 10 Pa, heat it to 800°C at a rate of 5°C / min and keep it for 2 hours, then cool it down, wash and dry the resulting solid, and name it AMC-800.

[0034] (2) Prepare anode plasma and perform desalination treatment

[0035] Weigh 5g of AMC-800 sample and add it to 95mL of 0.1mol / L sodium sulfate solution to prepare the anode plasma (mass fraction 5%). Weigh 5g of activated carbon particles and add it to 95mL of 0.1mol / L sodium sulfate solution to prepare the cathode plasma. Figure 1 The assembled flow electrode capacitive desalination device is shown, with a sodium chloride solution with an initial concentration of 500 mg / L as the water to be treated. The circulation flow rate of the anode pool and the cathode pool is 30 mL / min, and the flow rate of the wastewater pool is 30 mL / min. The anode pool is connected to the positive pole of the voltage-stabilized power supply, and a voltage of 1.5 V is applied to achieve desalination of the water to be treated.

[0036] Example 3

[0037] (1) Preparation of microalgae carbon AMC-1000 carbonized at 1000℃

[0038] Weigh 100 g of dried Chlorella, raise the temperature to 1000°C at a rate of 5°C / min and keep it for 2 hours under vacuum conditions with an air pressure of less than 10 Pa, then cool it down, wash and dry the obtained solid, and name it AMC-1000.

[0039] (2) Prepare anode plasma and perform desalination treatment

[0040] Weigh 5g of AMC-1000 sample and add it to 95mL of 0.1mol / L sodium sulfate solution to prepare the anode plasma (mass fraction 5%). Weigh 5g of activated carbon particles and add it to 95mL of 0.1mol / L sodium sulfate solution to prepare the cathode plasma. Figure 1 The assembled flow electrode capacitive desalination device is shown, with a sodium chloride solution with an initial concentration of 500 mg / L as the water to be treated. The circulation flow rate of the anode pool and the cathode pool is 30 mL / min, and the flow rate of the wastewater pool is 30 mL / min. The anode pool is connected to the positive pole of the voltage-stabilized power supply, and a voltage of 1.5 V is applied to achieve desalination of the water to be treated.

[0041] Comparative Example 1

[0042] Weigh 5g of activated carbon particles and add them to 95mL of a solution containing 0.1mol / L sodium sulfate to prepare an anode plasma (mass fraction 5%). Weigh 5g of activated carbon particles and add them to 95mL of a solution containing 0.1mol / L sodium sulfate to prepare a cathode plasma. Figure 1 The assembled flow electrode capacitive desalination device is shown, with a sodium chloride solution with an initial concentration of 500 mg / L as the water to be treated. The circulation flow rate of the anode pool and the cathode pool is 30 mL / min, and the flow rate of the wastewater pool is 30 mL / min. The anode pool is connected to the positive pole of the voltage-stabilized power supply, and a voltage of 1.5 V is applied to achieve desalination of the water to be treated.

[0043] The microalgae carbon obtained in Example 1, Example 2 and Example 3 was analyzed by X-ray diffractometer. The results are as follows: Figure 2 All three samples showed typical crystal peaks of carbon materials, which confirmed that Examples 1, 2 and 3 successfully transformed microalgae into carbon materials with different crystallinity.

[0044] The microalgae carbon obtained in Example 1, Example 2 and Example 3 was analyzed using a transmission electrode microscope. The results are as follows: Figure 3 As shown in Figure 2, it can be seen that the three types of microalgae carbon all have porous or undulating microstructures.

[0045] The nitrogen and phosphorus doping of the microalgae carbon obtained in Example 1, Example 2 and Example 3 was measured by X-ray spectrometer. The results can be seen in Figure 4 It can be seen that the three samples all contain nitrogen and phosphorus elements to varying degrees, proving that nitrogen and phosphorus elements have been successfully doped into microalgae carbon.

[0046] The simulated wastewater treated in Example 1, Example 2, Example 3 and Comparative Example 1 was continuously measured for salt concentration, and the results are shown in Table 1. It can be noted that except for the different granular electrode materials used in the anode cell plasma in Example 1, Example 2, Example 3 and Comparative Example 1, all other conditions remain the same. The implementation results show that the desalination capacity of Example 1, Example 2 and Example 3 is significantly better than that of Comparative Example 1, indicating that microalgae carbon can improve the performance of the flow electrode desalination system instead of activated carbon. At the same time, Example 1, Example 2 and Example 3 are compared with each other, and Example 3 has the best performance.

[0047] The above-described embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or changes made by those skilled in the art based on the present invention are within the protection scope of the present invention. The protection scope of the present invention shall be subject to the claims.

Claims

1. An application of microalgae carbon as a particle electrode in flow electrode capacitive desalination, characterized in that: The preparation method of microalgae carbon comprises the following steps: heating the microalgae particles to 1000°C at a heating rate of 1-10°C / min under vacuum conditions, and keeping the temperature for 2-10 hours, cooling the temperature, washing and drying to obtain microalgae carbon; the vacuum condition refers to a gas pressure of less than 10Pa; The microalgae carbon is used as a particle electrode, and an electrolyte is added to form a microalgae carbon plasma; then the microalgae carbon plasma is placed in the anode pool and / or cathode pool of a flowing electrode capacitor desalination device, and a voltage is applied to the flowing electrode capacitor desalination device to desalinate the wastewater.

2. The use of the microalgae carbon as a particle electrode in mobile electrode capacitive desalination according to claim 1 is characterized by: The microalgae particles are a mixture of one or more microalgae belonging to the phylum Cyanobacteria, Chlorophyta, Chrysophyta and Rhodophyta.

3. The use of the microalgae carbon as a particle electrode in mobile electrode capacitive desalination according to claim 2 is characterized by: The microalgae particles are Chlorella.

4. The use of the microalgae carbon as a particle electrode in flow electrode capacitive desalination according to claim 1, characterized in that: The mass fraction of the microalgae carbon in the microalgae carbon plasma is 5% to 20%.

5. The use of the microalgae carbon as a particle electrode in flow electrode capacitive desalination according to claim 1, characterized in that: The voltage applied to the flowing electrode capacitive desalination device is in the range of 1 to 5V.

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