Device and method for preparing polydopamine in-situ coating layer magnetized carbon base material

Abstract

The invention discloses a device and a method for preparing a polydopamine in-situ coating layer magnetized carbon base material, in an integrated sealing device, timing operation of different parts is controlled through a PLC (programmable logic controller), magnetizing and coating processes are realized, operation steps are reduced, ammonium persulfate (APS) is introduced as an oxidizing agent to trigger a free radical chain reaction, and the magnetic carbon base material is prepared. And the coating time of polydopamine (PDA) is shortened to 4-6 hours from 24 hours in the prior art. The method solves the problems of low magnetizing efficiency caused by tedious steps and step-by-step preparation in the process of magnetizing the carbon base material by adopting a coprecipitation method at present, and the problems of overlong coating time caused by the fact that the self-polymerization process of a PDA coating technology is limited by solution diffusion, a non-uniform coating is easy to form, the performance stability of the material is influenced and the coating time is too long.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental functional materials, and in particular relates to a device and method for preparing a magnetic carbon substrate with an in-situ coating layer of polydopamine. Background Art

[0002] Carbon substrates, such as activated carbon, are typically made by activating carbon-containing materials such as wood, coal, and fruit shells under high-temperature, oxygen-deficient conditions. Activated carbon adsorption is the process of removing pollutants from water by utilizing the activated carbon's physical adsorption, chemical adsorption, oxidation, catalytic oxidation, and reduction properties. Commonly used activated carbons include powdered carbon and granular carbon. However, after granular activated carbon reaches adsorption saturation and replacement, it is typically discarded, buried, or burned due to high recycling and operating costs, resulting in a waste of resources and the risk of secondary environmental pollution. Powdered activated carbon has a large specific surface area and strong adsorption capacity, and is effective in removing recalcitrant substances that are difficult to remove by conventional biological methods. However, due to its small particle size and light specific gravity, powdered activated carbon also has the disadvantage of being difficult to separate from treated water and easily lost during use. Therefore, how to enhance the retention and screening capabilities of such lightweight carbon substrate systems is a key issue that needs to be addressed in the large-scale engineering application of carbon substrates.

[0003] To overcome this problem, magnetic separation technology, which is safe, effective, and inexpensive, is used to magnetize carbon substrates to prepare magnetic carbon substrates, retaining the original physical and chemical properties of the carbon substrate while also possessing the characteristics of magnetic separation. However, among the commonly used preparation methods, coprecipitation is the most common method for preparing magnetic carbon substrates, due to its advantages such as uniform loading of magnetic materials, mild reaction conditions, and ease of scale-up. However, the traditional method uses chemical coprecipitation to load Fe3O4 particles on the surface of the carbon substrate. However, the physical adsorption between the particles and the substrate is the main mechanism, and they easily fall off in acidic or high ionic strength environments, resulting in magnetic attenuation. The corresponding preparation process is cumbersome, and the magnetic carbon substrate often clogs the carbon substrate pores, resulting in a reduction in the specific surface area and adsorption efficiency of the carbon substrate. The prepared magnetic carbon substrate also has the problem of easy shedding of magnetic materials. At the same time, the step-by-step preparation process often comes into contact with air, resulting in reaction with oxygen to form iron oxide (Fe2O3), resulting in low magnetic efficiency of the resulting magnetic carbon substrate. At the same time, traditional PDA coating relies on the spontaneous oxidative polymerization of dopamine under weakly alkaline conditions, which usually takes 12 to 24 hours, is inefficient, and consumes a lot of energy. Summary of the Invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a device and method for preparing a polydopamine in-situ coating layer for magnetizing a carbon substrate, so as to solve the problem of low magnetization efficiency caused by the cumbersome steps and step-by-step preparation in the current magnetization process of the carbon substrate using the co-precipitation method, as well as the problem that the self-polymerization process of the PDA coating technology is limited by the diffusion of the solution, which easily forms an uneven coating, affects the stability of the material performance, and causes the coating time to be too long. In the present invention, in an integrated sealing device, the timed operation of different components is controlled by PLC to realize the magnetization and coating process, reduce the number of operating steps, and by introducing ammonium persulfate (APS) as an oxidant to trigger a free radical chain reaction, the PDA coating time is compressed from the traditional 24 hours to 4 to 6 hours.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A device for preparing a magnetic carbon substrate with an in-situ coating layer of polydopamine, comprising a reaction tank with a built-in stirrer, the reaction tank being connected to a hot water bath, an aeration pump, a first peristaltic pump, a pH meter, a PLC controller, a feed port, and four reagent bottles; the outlets of the four reagent bottles are respectively connected to a reagent inlet of the reaction tank via a syringe pump; the feed port is used to feed the carbon substrate and ultrapure water; the four reagent bottles respectively store a magnetic reagent, an alkaline reagent, a buffer reagent, and dopamine hydrochloride; the buffer reagent is a Tris-HCl buffer solution containing ammonium persulfate;

[0007] The PLC controller is configured to control the start and stop timing of the agitator, hot water bath device, aeration pump, first peristaltic pump and each injection pump, and the pH meter is configured to provide the PLC controller with the real-time pH value in the reaction tank so that the PLC controller controls the addition of the alkaline reagent through the injection pump.

[0008] In one embodiment, the preparation device for the polydopamine in-situ coating layer magnetic carbon substrate further comprises: a condenser, a nitrogen bottle and a second peristaltic pump;

[0009] The condenser includes a water seal bottle and a cold water bath device. The water seal bottle stores the carbon substrate and ultrapure water and is connected to the feed port via a pipe with a one-way valve. The cold water bath device acts on the pipe to cool the carbon substrate and the ultrapure water.

[0010] The nitrogen bottle is connected to the aeration head at the bottom of the reaction tank through a pipeline, and the aeration pump is installed on the pipeline;

[0011] The second peristaltic pump is installed in the bottom pipe of the reaction tank and is used to discharge the deionized water in the tank.

[0012] In one embodiment, the apparatus for preparing the polydopamine in-situ coating layer magnetic carbon substrate further comprises: an additional reagent bottle;

[0013] The additional reagent bottle stores a mixed solution of NaOH and NH3·H2O. When the pH meter shows that the pH exceeds a first threshold, the PLC controller controls to stop adding the alkaline reagent and starts adding the mixed solution of NaOH and NH3·H2O until the pH meter shows that the pH reaches the set value.

[0014] The present invention also provides a method for preparing a polydopamine in-situ coating layer magnetic carbon substrate, which is based on the above-mentioned preparation device of a polydopamine in-situ coating layer magnetic carbon substrate, and comprises the following steps:

[0015] Step 1, feeding a carbon substrate and ultrapure water into the reaction cell;

[0016] Step 2: Execute the following steps under the control of the PLC controller:

[0017] Step 21, controlling to immediately start the stirrer and the hot water bath device for stirring and heating;

[0018] Step 22, after a set time t1, start the aeration pump to perform aeration, after a set time t2, start the syringe pump to quantitatively add a magnetic reagent to the reaction tank, and continuously add an alkaline reagent until the real-time pH value received from the pH meter reaches the set value, control the agitator to turn off, and maintain heating;

[0019] Step 23, after a set time t3, controlling the hot water bath device to close and cool;

[0020] Step 24, after a set time t4, controlling the first peristaltic pump to add deionized water to wash the obtained magnetic carbon substrate, and controlling the discharge of the deionized water;

[0021] Step 25, controlling the syringe pump to quantitatively add the buffer reagent and dopamine hydrochloride, and controlling the start of the stirrer;

[0022] Step 26: After the set time t5, control the first peristaltic pump to add deionized water for washing to obtain a magnetic carbon substrate having an in-situ coating layer of polydopamine.

[0023] In one embodiment, the weight ratio of the carbon substrate to ultrapure water is 1:3 to 1:5, the weight ratio of the magnetic agent to the carbon substrate is 1:3 to 1:5, and the pH setting value is 9.2; the amount of the buffer reagent added is 0.5 to 1.5 L / kg of carbon substrate, and the weight ratio of dopamine hydrochloride to the initial carbon substrate is 1:8 to 1:12.

[0024] In one embodiment, the magnetic agent is a mixed solution of FeCl3·6H2O and FeSO4·7H2O in a molar ratio of 1.5:1 to 2.5:1.

[0025] In one embodiment, t1 = 10 to 20 min, t2 = 8 to 15 min, t3 = 1.5 to 3 h, t4 = 1 to 2 h, and t5 = 4 to 6 h.

[0026] In one embodiment, the water bath temperature of the hot water bath device is 70° C., the stirring speed of the stirrer in step 21 is 600-800 r / min, and the stirring speed of the stirrer in step 25 is 200-400 r / min.

[0027] In one embodiment, the alkaline reagent is a sodium hydroxide solution. In step 22, the sodium hydroxide solution is first added under control, and the addition is stopped when the pH meter shows pH>10.5. Then, a mixed solution of NaOH and NH3·H2O in a molar ratio of 3:1 to 5:1 is added under control, and the addition is stopped when the pH meter shows 9.0 to 9.5.

[0028] Among them, sodium hydroxide solution was injected at a rate of 1 mL / s to quickly neutralize Fe 3+ / Fe 2+ The hydrolysis acid, NaOH and NH3·H2O mixed solution was injected at a rate of 0.3-0.7 mL / s, and the complexation of NH3·H2O was used to regulate the conversion of Fe(OH)3→Fe3O4. Specifically, NH3 complexed Fe 3+ → Reduce free Fe 3+ Concentration; Fe3O4 generates and consumes OH - →Release H + →The pH gradually dropped to the buffer zone between 9.0 and 9.5.

[0029] In one embodiment, the product of step 24 is washed with deionized water to reduce its alkalinity to a pH less than 8 (close to neutral).

[0030] In one embodiment, the Tris-HCl buffer solution containing ammonium persulfate has a pH of 8.0-9.0, an ammonium persulfate concentration of 0.5-2.0 mM, and a molar ratio of ammonium persulfate to dopamine hydrochloride in the range of 1:1-1:3.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The system construction is simple to operate. The present invention adopts an integrated preparation device and realizes the preparation of the magnetic carbon substrate with the polydopamine in-situ coating layer through PLC control. The reaction conditions are mild and easy to achieve, with strong controllability, and the thickness and uniformity of the coating layer can be accurately controlled.

[0033] 2. By introducing ammonium persulfate (APS) as an oxidant, a free radical chain reaction is triggered, and the polydopamine (PDA) coating time is compressed from the traditional 24 hours to 4 to 6 hours.

[0034] 3. Use NaOH (strong base) and NH3·H2O (weak base) in a 4:1 molar ratio to form a gradient dissociation environment. Through the complexation of NH3·H2O, the rapid precipitation of Fe(OH)3 is inhibited, and the directional growth of Fe3O4 spinel structure is promoted. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of the reaction device in an embodiment of the present invention.

[0036] Figure 2 This is the program control Yes / No diagram corresponding to Example 1 of the present invention.

[0037] Figure 3 This is a physical picture of the magnetic carbon substrate prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0038] The embodiments of the present invention are described in detail below with reference to the accompanying drawings and examples.

[0039] like Figure 1 As shown, the apparatus for preparing a magnetic carbon substrate with an in-situ polydopamine coating layer of the present invention includes a reaction tank 1, in which an agitator 2 is provided. The reaction tank 1 is connected to a hot water bath 3, an aeration pump 4, a first peristaltic pump 5, a pH meter 6, a PLC controller 7, a feed port 8, and four reagent bottles. The feed port 8 is used to feed the carbon substrate and ultrapure water.

[0040] The four reagent bottles of the present invention respectively store magnetic reagent, alkaline reagent, buffer reagent and dopamine hydrochloride. The reaction pool 1 has four reagent inlets. The outlets of the four reagent bottles are respectively connected to a reagent inlet through a syringe pump, and the corresponding reagents are delivered into the reaction pool 1 under the action of the syringe pump.

[0041] The magnetic agent is used to provide a magnetic material for the carbon substrate. It can be FeCl3·6H2O or FeSO4·7H2O, or a mixed solution of the two. In the embodiment of the present invention, the magnetic agent is a mixed solution of FeCl3·6H2O and FeSO4·7H2O with a molar ratio of 1.5:1 to 2.5:1, and the molar ratio is more preferably 2:1. This directly meets the crystal growth requirements, reduces the generation of by-products (such as γ-Fe2O3 or FeOOH), and improves the purity of the magnetic core.

[0042] Dopamine hydrochloride is an in-situ coating material, which uses norepinephrine hydrochloride and contains hydroxyl and amino bifunctional groups to improve the cross-linking density of the coating layer.

[0043] The alkaline reagent is used to adjust the pH value of the reaction system. In the embodiment of the present invention, sodium hydroxide solution can be used.

[0044] The present invention uses a Tris-HCl buffer solution containing ammonium persulfate as a buffer reagent. On the one hand, it is used to introduce ammonium persulfate (APS) as an oxidant, which can trigger the oxidative self-polymerization of dopamine and significantly shorten the polydopamine (PDA) coating time through a free radical chain reaction. On the other hand, the APS / Tris-HCl buffer system is used to achieve a "sustained release" function. Through the synergistic effect of the pH-regulated oxidant decomposition kinetics and the ion complexation effect, the free radical generation rate and distribution are precisely controlled, thereby optimizing the uniformity and density of the polydopamine (PDA) coating layer. For example, the Tris-HCl buffer solution containing ammonium persulfate of the present invention has a pH of 8.0 to 9.0, preferably 8.5, and an ammonium persulfate concentration of 0.5 to 2.0 mM, preferably 1 mM, to prevent excessive oxidation caused by excessive concentration and a rough coating layer. The molar ratio of ammonium persulfate to dopamine hydrochloride ranges from 1:1 to 1:3.

[0045] According to the above structure, the agitator 2, hot water bath 3, aeration pump 4, first peristaltic pump 5, and each syringe pump are connected to a PLC controller 7, which controls the start and stop timing of each device. The PLC controller 7 is primarily based on time and receives the real-time pH value of the reaction tank 1 collected by the pH meter 6. The pH value is used as the basis for controlling the addition of the alkaline reagent.

[0046] Furthermore, the apparatus for preparing a polydopamine-in-situ coated magnetic carbon substrate of the present invention further includes a condenser 8. The condenser 8 comprises a water seal bottle 9 and a cold water bath 10. The water seal bottle 9 stores the carbon substrate and ultrapure water, which are fed through a feed port 8 connected to a pipe with a one-way valve 11. The cold water bath 10 acts on the pipe to cool the carbon substrate and ultrapure water before entering the reaction tank 1. The one-way valve design creates a sealed environment without air pressure and prevents evaporation and loss of water.

[0047] Furthermore, the preparation device of the polydopamine in-situ coating layer magnetic carbon substrate of the present invention also includes a nitrogen bottle 12, which is connected to the aeration head at the bottom of the reaction tank 1 through a pipeline, and an aeration pump 4 is installed on the pipeline, and aeration is performed by controlling the aeration pump 4 by the PLC controller 7.

[0048] Furthermore, the preparation device of the polydopamine in-situ coating layer magnetic carbon substrate of the present invention also includes a second peristaltic pump 13, which is installed in the bottom pipe of the reaction tank 1. Its main function is to discharge the deionized water in the tank, and its start and stop timing can also be controlled by the PLC controller 7.

[0049] Furthermore, the preparation device of the polydopamine in-situ coating layer magnetic carbon substrate of the present invention also includes an additional reagent bottle, which stores a mixed solution of NaOH and NH3·H2O, which is an additional reagent for the aforementioned alkaline reagent, and the molar ratio of the two is 3:1 to 5:1, preferably 4:1. Its main function is to further refine the pH value of the adjustment system. Specifically, when the pH meter 6 shows that the pH exceeds the first threshold value (typically 10.5), the PLC controller 7 controls the injection pump corresponding to the reagent bottle storing the alkaline reagent to stop working, stop adding the alkaline reagent, start the injection pump corresponding to the additional reagent bottle, and add the mixed solution of NaOH and NH3·H2O until the pH meter 6 shows that the pH reaches the set value (typically 9.2).

[0050] refer to Figure 2 As shown, the method for preparing a polydopamine in-situ coating layer magnetic carbon substrate of the present invention using the above-mentioned polydopamine in-situ coating layer magnetic carbon substrate mainly includes the following steps:

[0051] Step 1: Add carbon substrate and ultrapure water into reaction tank 1.

[0052] The carbon substrate in the present invention mainly includes walnut shells, fruit shells, peanut shells, cotton shells, etc. Each time the carbon substrate is prepared, it is mixed with ultrapure water in a weight ratio of 1:3 to 1:5, preferably 1:4 in this embodiment.

[0053] Step 2: Execute the following steps under the control of the PLC controller 7:

[0054] Step 21 : After the carbon substrate and ultrapure water are injected, the stirrer 2 and the hot water bath device 3 are immediately started to stir and heat.

[0055] For example, the water bath temperature of the hot water bath device 3 is preferably 70° C., and the stirring speed of the stirrer 2 is 600-800 r / min. The carbon substrate is quickly and fully dispersed uniformly through rapid stirring, while avoiding powdering of the carbon substrate, which is beneficial to subsequent magnetic carbon recovery.

[0056] Step 22: After the set time t1, start the aeration pump 4 for aeration, and after the set time t2, start the injection pump to quantitatively add the magnetic reagent to the reaction tank 1, and continuously add the alkaline reagent until the real-time pH value received from the pH meter 6 reaches the set value, control the agitator 2 to be turned off, and maintain heating.

[0057] For example, the weight ratio of the magnetic agent to the carbon substrate is 1:3 to 1:5, more preferably 1:4. t1 = 10 to 20 min, more preferably 15 min, t2 = 8 to 15 min, more preferably 10 min, to achieve an anaerobic preparation environment.

[0058] Furthermore, the alkaline reagent sodium hydroxide solution (concentration 5 mol / L) is first controlled to be added, and when the pH meter 6 shows pH>10.5, the injection pump is controlled to stop adding, and then another injection pump is controlled to add a mixed solution of NaOH and NH3·H2O. When the pH meter 6 shows 9.0-9.5 (more preferably 9.2), the injection pump is controlled to stop adding.

[0059] Furthermore, NaOH solution was injected at a rate of 1 mL / s to quickly neutralize Fe 3+ / Fe 2+ The hydrolysis acid, NaOH and NH3·H2O mixed solution was injected at a rate of 0.5 mL / s, and the complexing effect of NH3·H2O was used to regulate the conversion of Fe(OH)3→Fe3O4.

[0060] In this step, after the iron salt solution enters the surface of the carbon substrate to be magnetized, it inhibits the rapid precipitation of Fe(OH)3 through the complexation effect of NH3·H2O under heating conditions, promotes the directional growth of Fe3O4 spinel structure, and enables magnetic particles to be generated in situ on the carbon substrate by co-precipitation.

[0061] Step 23: After the set time t3, the hot water bath device 3 is controlled to be closed and cooled.

[0062] For example, t3 = 1.5 to 3 hours, preferably 2 hours, and this process is a static aging process.

[0063] Step 24, after the set time t4, control the first peristaltic pump 5 to add deionized water for washing for about 5 minutes to reduce its alkalinity and make the pH less than 8 (close to neutral) to obtain a magnetic carbon substrate, and control the discharge of deionized water.

[0064] For example, t4 = 1 to 2 h, preferably 1.5 h, which can ensure cooling to room temperature.

[0065] Step 25, controlling the syringe pump to quantitatively add the buffer reagent and dopamine hydrochloride, and controlling the start of the stirrer 2 to form an in-situ polydopamine coating layer.

[0066] For example, the amount of buffer added is 0.5-1.5 L / kg of carbon substrate, and the weight ratio of dopamine hydrochloride to the initial carbon substrate is 1:8-1:12, preferably 1:10. The stirring speed of stirrer 2 is 200-400 rpm to ensure homogenization of the solution and prevent excessive local concentration of APS.

[0067] Step 26: After the set time t5, control the first peristaltic pump 5 to add deionized water for washing to obtain a magnetic carbon substrate having an in-situ coating layer of polydopamine.

[0068] For example, t5 = 4 to 6 hours, preferably 5 hours.

[0069] The PLC controller 7 of the present invention can realize timing control by program, and the control program is:

[0070] st=>start: Start the PLC controller

[0071] open_bath_stir=>operation: PLC controls the opening of a 70°C water bath and agitator;

[0072] wait_10min=>operation: wait 10 minutes;

[0073] open_aerate=>operation: PLC controls the aeration pump to aerate for 10 minutes;

[0074] inject_mix=>operation: PLC controls the injection pump to add FeCl3·6H2O and FeSO4·7H2O mixed solution and carbon substrate in a ratio of 1:4;

[0075] inject_naoh=>operation: PLC controls the injection pump to drip 5 mol / L sodium hydroxide solution;

[0076] judge_ph=>condition: pH meter shows pH>10.5?

[0077] stop_naoh=>operation: PLC controls the injection pump to stop adding sodium hydroxide solution;

[0078] inject_naoh=>operation: PLC controls the injection pump to drip a mixed solution of NaOH and NH3·H2O with a molar ratio of 4:1;

[0079] judge_ph=>condition: pH meter shows pH=7.2?

[0080] stop_naoh=>operation: PLC controls the syringe pump to stop adding the mixed solution of NaOH and NH3·H2O;

[0081] close_stir=>operation: PLC controls the stirring machine to be closed;

[0082] wait_2h=>operation: let it stand for 2 hours;

[0083] close_bath=>operation: PLC controls the closing of the 70°C water bath cycle;

[0084] Cool_down=>operation: Cool to room temperature for 1.5 hours;

[0085] wash_product=>operation: PLC controls the peristaltic pump to add deionized water to wash the product for 5 minutes;

[0086] end=>end: Obtaining a fully magnetized carbon substrate;

[0087] exclude_water=>operation: PLC controls the peristaltic pump to exclude deionized water;

[0088] inject_mix=>operation: PLC controls the injection pump to add 2 L of Tris-HCl buffer solution containing ammonium persulfate (APS);

[0089] inject_da=>operation:PLC controlled injection pump adds PLC controlled injection pump adds dopamine hydrochloride;

[0090] open_stir=>operation: PLC controls the stirring machine to start;

[0091] wait_5h=>operation: wait 5h;

[0092] wash_product=>operation: PLC controls the peristaltic pump to add deionized water to wash the product for 5 minutes;

[0093] end=>end: obtaining a polydopamine in-situ coating layer and magnetic carbon substrate;

[0094] st->open_bath_stir->wait_10min->open_aerate->inject_mix->inject_naoh-

[0095] >judge_phjudge_ph(yes)->stop_naoh->close_stir->wait_2h->close_bath-

[0096] >cool_down->wash_product->endjudge_ph(no)->inject_naoh

[0097] The specific steps are explained as follows:

[0098] st (start): Start the PLC controller, which is the starting point of the entire automation control process and provides a control basis for the orderly operation of subsequent equipment;

[0099] open_bath_stir: PLC controls the opening of a 70°C water bath and agitator;

[0100] wait_10min: wait for 10 minutes;

[0101] open_aerate: PLC controls the aeration pump to aerate for 10 minutes;

[0102] inject_mix: PLC controls the injection pump to add the FeCl3·6H2O and FeSO4·7H2O mixed solution, and add it to the carbon substrate in a ratio of 1:4;

[0103] inject_naoh: PLC controls the injection pump to drip 5 mol / L sodium hydroxide solution;

[0104] judge_ph: This is a judgment step, which uses a pH meter to monitor the pH value of the reaction system in real time to determine whether the pH value meets the condition of pH>10.5;

[0105] The judgment result is "yes": stop_naoh: When the pH meter shows pH>10.5, the PLC controls the injection pump to stop adding sodium hydroxide solution;

[0106] inject_naoh: PLC controls the injection pump to drip a mixed solution of NaOH and NH3·H2O with a molar ratio of 4:1;

[0107] judge_ph: This is a judgment step, which uses a pH meter to monitor the pH value of the reaction system in real time to determine whether the pH value meets the condition of pH = 9.2;

[0108] The judgment result is "yes": stop_naoh: When the pH meter shows pH = 9.2, the PLC controls the syringe pump to stop adding the mixed solution of NaOH and NH3·H2O;

[0109] close_stir: PLC controls to close the stirrer and stop the stirring operation;

[0110] wait_2h: let it stand for 2 hours;

[0111] close_bath: PLC controls the closing of the 70°C water bath cycle;

[0112] cool_down: Cool down to room temperature for 1.5 hours;

[0113] wash_product: PLC controls the peristaltic pump to add deionized water to wash the product for 5 minutes;

[0114] End: Obtaining the magnetic carbon substrate;

[0115] exclude_water=>operation: PLC controls the peristaltic pump to exclude deionized water;

[0116] inject_mix=>operation: PLC controls the injection pump to add 2 L of Tris-HCl buffer solution containing ammonium persulfate (APS);

[0117] inject_da=>operation:PLC controlled injection pump adds PLC controlled injection pump adds dopamine hydrochloride;

[0118] open_stir=>operation: PLC controls the stirring machine to start;

[0119] wait_5h=>operation: wait 5h;

[0120] wash_product=>operation: PLC controls the peristaltic pump to add deionized water to wash the product for 5 minutes;

[0121] end=>end: obtain the magnetic carbon substrate material with polydopamine in-situ coating layer, and the whole process ends;

[0122] The judgment result is "no": If the pH meter shows pH ≤ 9, continue to execute the inject_naoh step, that is, continue to add sodium hydroxide solution until the pH is greater than 9;

[0123] Through PLC automated control, the magnetization and in-situ coating process of the carbon substrate can be completed accurately. Each step is closely linked to ensure that a high-quality magnetized carbon substrate is ultimately obtained.

[0124] In a specific embodiment of the present invention, 50g of dried peanut shells and 200mL of ultrapure water are added to the reaction tank 1 through the feed port 4, and the PLC controller 7 is started for magnetization. First, the PLC controller 7 controls the 70°C hot water bath device 3 and the stirrer 2 to start. After 20 minutes of reaching 70°C, the aeration pump 4 is controlled to aerate for 10 minutes to achieve an anaerobic preparation environment. Then, the injection pump is controlled to add 1L of a mixed solution of FeCl3·6H2O and FeSO4·7H2O, and then the injection pump is controlled to dropwise add a sodium hydroxide solution with a concentration of 5mol / L. When the pH meter 6 shows pH>10.5, the injection pump is controlled to stop adding, and then the injection pump is controlled to dropwise add NaOH and NH3·H2 with a molar ratio of 4:1. O mixed solution, when the pH meter 6 shows 9.2, the injection pump is controlled to stop adding, then the stirrer 2 is controlled to be closed, and the mixture is allowed to stand for 2 hours, and then the hot water bath device 3 is controlled to be closed, and the mixture is cooled to room temperature for 1.5 hours, and finally the first peristaltic pump 5 is controlled to add ionized water to wash the product for 5 minutes to obtain a magnetic carbon substrate, and then the second peristaltic pump 13 is controlled to remove deionized water, and the injection pump is controlled to add 2L of Tris-HCl buffer solution containing ammonium persulfate (APS); then the injection pump is controlled to add dopamine hydrochloride, and the mass ratio of dopamine hydrochloride to the magnetic carbon substrate is 1:10, and then the stirrer 2 is controlled to be turned on, and after 5 hours, the first peristaltic pump 5 is controlled to add deionized water to wash the product to obtain a magnetic carbon substrate with an in-situ coating layer of polydopamine. The prepared product is as follows Figure 3 shown.

[0125] It was used to adsorb methylene blue (MB). The results showed that the prepared magnetic carbon substrate had good adsorption performance for MB, and the adsorption capacity of methylene blue increased by 20% to 40% compared with the accelerated coated sample. The magnetic carbon substrate and the solution could be quickly separated by an external magnetic field.

[0126] In summary, the present invention utilizes an integrated sealing device, which is simple to operate, to in situ coat the surface of a magnetic carbon substrate with a polydopamine layer, improving the material's stability, biocompatibility, and surface functionality. Without compromising coating quality, the process time is shortened to 4-6 hours, and the functionality of the coating layer is significantly enhanced, enabling industrialized large-scale production.

Claims

1. A device for preparing a polydopamine in-situ coating layer of a magnetic carbon substrate, characterized in that: The invention relates to a reaction tank (1) having a built-in stirrer (2), wherein the reaction tank (1) is connected to a hot water bath device (3), an aeration pump (4), a first peristaltic pump (5), a pH meter (6), a PLC controller (7), a feed port (8) and four reagent bottles; the outlets of the four reagent bottles are respectively connected to a reagent inlet of the reaction tank (1) via a syringe pump; the feed port (8) is used to feed a carbon substrate and ultrapure water; the four reagent bottles respectively store a magnetic reagent, an alkaline reagent, a buffer reagent and dopamine hydrochloride; the buffer reagent is a Tris-HCl buffer solution containing ammonium persulfate; The PLC controller (7) is configured to control the start and stop timing of the stirrer (2), the hot water bath device (3), the aeration pump (4), the first peristaltic pump (5) and each injection pump, and the pH meter (6) is configured to provide the PLC controller (7) with the real-time pH value in the reaction tank (1), so that the PLC controller (7) controls the addition of the alkaline reagent through the injection pump.

2. The device for preparing a magnetic carbon substrate with an in-situ polydopamine coating layer according to claim 1, characterized in that: Also includes: a condenser (8), a nitrogen bottle (12) and a second peristaltic pump (13); The condenser (8) includes a water seal bottle (9) and a cold water bath device (10), wherein the water seal bottle (9) stores the carbon substrate and ultrapure water and is connected to the feed port (8) via a pipeline with a one-way valve (11); the cold water bath device (10) acts on the pipeline to cool the carbon substrate and the ultrapure water; The nitrogen bottle (12) is connected to the aeration head at the bottom of the reaction tank (1) through a pipeline, and the aeration pump (4) is installed on the pipeline; The second peristaltic pump (13) is installed in the bottom pipe of the reaction tank (1) and is used to discharge the deionized water in the tank.

3. The device for preparing a magnetic carbon substrate with an in-situ polydopamine coating layer according to claim 1, characterized in that: Also includes: Additional reagent bottles; The additional reagent bottle stores a mixed solution of NaOH and NH3·H2O. When the pH meter (6) displays that the pH exceeds a first threshold value, the PLC controller (7) controls to stop adding the alkaline reagent and starts adding the mixed solution of NaOH and NH3·H2O until the pH meter (6) displays that the pH reaches the set value.

4. A method for preparing a polydopamine in-situ coating layer magnetic carbon substrate, based on the preparation device of a polydopamine in-situ coating layer magnetic carbon substrate according to claim 1, characterized in that: The steps include: Step 1, feeding a carbon substrate and ultrapure water into the reaction cell (1); Step 2, under the control of the PLC controller (7), perform the following steps: Step 21, controlling to immediately start the stirrer (2) and the hot water bath device (3) to stir and heat; Step 22, after a set time t1, the aeration pump (4) is started to perform aeration, after a set time t2, the injection pump is started to quantitatively add a magnetic reagent to the reaction tank (1), and the alkaline reagent is continuously added until the real-time pH value received from the pH meter (6) reaches the set value, and the stirrer (2) is controlled to be turned off and the heating is maintained; Step 23, after a set time t3, controlling to close the hot water bath device (3) and cool down; Step 24, after a set time t4, controlling the first peristaltic pump (5) to add deionized water to wash the obtained magnetic carbon substrate, and controlling the discharge of the deionized water; Step 25, controlling the syringe pump to quantitatively add the buffer reagent and dopamine hydrochloride, and controlling the start of the stirrer (2); Step 26, after the set time t5, controlling the first peristaltic pump (5) to add deionized water for washing to obtain a magnetic carbon substrate having an in-situ coating layer of polydopamine.

5. The method for preparing a magnetic carbon substrate with an in-situ polydopamine coating layer according to claim 4, characterized in that: The weight ratio of the carbon substrate to ultrapure water is 1:3 to 1:5, the weight ratio of the magnetic reagent to the carbon substrate is 1:3 to 1:5, and the pH setting value is 9.2; the amount of the buffer reagent added is 0.5 to 1.5 L / kg of carbon substrate, and the weight ratio of dopamine hydrochloride to the initial carbon substrate is 1:8 to 1:

12.

6. The method for preparing a magnetic carbon substrate with an in-situ polydopamine coating layer according to claim 4 or 5, characterized in that: The magnetic agent is a mixed solution of FeCl3·6H2O and FeSO4·7H2O in a molar ratio of 1.5:1 to 2.5:

1.

7. The method for preparing a magnetic carbon substrate with an in-situ polydopamine coating layer according to claim 4 or 5, characterized in that: The t1=10-20 min, t2=8-15 min, t3=1.5-3 h, t4=1-2 h, and t5=4-6 h.

8. The method for preparing a magnetic carbon substrate with an in-situ polydopamine coating layer according to claim 4 or 5, characterized in that: The water bath temperature of the hot water bath device (3) is 70°C, the stirring speed of the stirrer (2) in step 21 is 600-800 r / min, and the stirring speed of the stirrer (2) in step 25 is 200-400 r / min.

9. The method for preparing a magnetic carbon substrate with an in-situ polydopamine coating layer according to claim 4 or 5, characterized in that: The alkaline reagent is a sodium hydroxide solution. In step 22, the sodium hydroxide solution is first added under control, and the process is stopped when the pH meter (6) shows a pH value greater than 10.

5. Then, a mixed solution of NaOH and NH3·H2O in a molar ratio of 3:1 to 5:1 is added under control, and the process is stopped when the pH meter (6) shows a value of 9.0 to 9.

5. Among them, sodium hydroxide solution was injected at a rate of 1 mL / s to quickly neutralize Fe 3+ / Fe2 + The hydrolysis acid, a mixed solution of NaOH and NH3·H2O was injected at a rate of 0.3-0.7 mL / s, and the complexing effect of NH3·H2O was used to regulate the conversion of Fe(OH)3 to Fe3O4.

10. The method for preparing a magnetic carbon substrate with an in-situ polydopamine coating layer according to claim 4 or 7, characterized in that: The Tris-HCl buffer solution containing ammonium persulfate has a pH of 8.0-9.0, an ammonium persulfate concentration of 0.5-2.0 mM, and a molar ratio of ammonium persulfate to dopamine hydrochloride of 1:1-1:3.

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