Preparation of cobalt-based biochar composite and its application in persulfate oxidation

Abstract

The application discloses a preparation method of a cobalt-based biochar composite material and application of the cobalt-based biochar composite material in persulfate oxidation, and comprises the following operation steps: a proper amount of sodium alginate is weighed, calcined, activated and dried to obtain a derived original biochar SA; after the SA is used as an adsorbent to adsorb cobalt ions, drying is performed to obtain a cobalt-containing biochar CoSA; the CoSA is uniformly ground with urea, pyrolysis is performed, washing, filtering and drying are performed, and vacuum drying is performed to obtain a cobalt-based biochar composite material CoNBC based on sodium alginate; and the activation method is that the SA is mixed with potassium hydroxide, ground in a jade mortar for 5-30 min, and then activated in ultrapure water for 1-8 h.The raw material used in the application is environment-friendly, the preparation process is simple, the cobalt-based biochar composite material obtained has excellent catalytic capacity for persulfate, can effectively control the precipitation of transition metals, reduces pollution, and greatly improves the utilization rate of metal elements.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cobalt-based biochar composite materials, and particularly relates to a preparation method of a cobalt-based biochar composite material with biochar loaded with metal cobalt and application of the cobalt-based biochar composite material in persulfate oxidation degradation. BACKGROUND

[0002] The types and quantities of synthetic organic compounds have been rapidly increasing since the middle of the 20th century. On the one hand, these organic compounds have improved the quality of human production and life, but on the other hand, they have caused great negative impacts on the environment, especially drugs, personal care products and endocrine disruptors. Non-steroidal anti-inflammatory drugs, as a common class of drugs, cannot be completely removed and are discharged into water bodies, posing potential risks to aquatic organisms and food chains. The current traditional methods (such as biological method, adsorption method and extraction method) have problems such as high cost, long cycle and low efficiency. Therefore, it is essential to develop efficient treatment technologies to solve the problem of water pollution.

[0003] The persulfate-based advanced oxidation technology is an efficient, widely selective and adaptable water treatment method, which can effectively degrade various organic and inorganic pollutants and has good removal effect on refractory organic drugs, so this technology has attracted extensive attention from researchers. As an oxidant, persulfate can be activated by various ways (such as heat, ultrasonic wave, transition metal, transition metal oxide, composite oxide and carbon material, etc.). Metal-based catalysts (such as metal oxide, spinel, perovskite, etc.) are concerned by researchers due to their high stability and excellent catalytic ability. However, most of the metal-based materials have the problem of metal aggregation in the pyrolysis preparation process, which leads to the reduction of metal utilization rate. In addition, in the process of oxidation-reduction reaction, the precipitated metal ions may cause secondary pollution to the environment. Therefore, it is necessary to find a simple preparation method to overcome the precipitation of metal ions and improve the utilization rate of metal. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art and provide a preparation method of a cobalt-based biochar composite material based on sodium alginate to improve the utilization rate of metal in metal-based materials and reduce the potential risk of metal precipitation.

[0005] Another purpose of the present application is to provide a cobalt-based biochar composite material based on sodium alginate prepared by the above preparation method.

[0006] Still another purpose of the present application is to provide the application of the above cobalt-based biochar composite material based on sodium alginate in persulfate oxidation degradation.

[0007] The present application is realized by the following technical solutions:

[0008] A preparation method of a cobalt-based biochar composite material based on sodium alginate, comprising the following steps:

[0009] S1, a proper amount of sodium alginate is weighed, calcined, activated and dried to obtain a derived original biochar SA; the sodium alginate can be commercially purchased sodium alginate, which is abundant in source, renewable, single in composition and low in cost, and is friendly to the environment.

[0010] S2, the original biochar SA is used as an adsorbent to adsorb cobalt ions, and then vacuum drying is performed to obtain a cobalt-containing biochar CoSA.

[0011] S3, the CoSA is uniformly ground with urea, pyrolysis is performed, and then washing, filtering and vacuum drying are performed to obtain the cobalt-based biochar composite material CoNBC based on sodium alginate.

[0012] Further, the mass ratio of the CoSA to urea is 1:(1-3).

[0013] Further, the pyrolysis method is: heating at a heating rate of 5-15℃ / min to 600-800℃, and then pyrolysis treatment is performed for 1-4h. The pyrolysis equipment can be a muffle furnace, a tube furnace, etc.

[0014] Further, the activation method in the S1 step is: the SA and potassium hydroxide KOH are mixed uniformly in a mass ratio of 1:(1-4) in a agate mortar for 5-30min, then the mixture is placed in ultrapure water according to the proportion of 0.5g of the ground mixture per 500mL of ultrapure water, and activated in the ultrapure water for 1-8h.

[0015] Further, the method of using the original biochar SA as an adsorbent to adsorb cobalt ions in the S2 step is: the SA adsorbent is put into a solution containing cobalt ions for adsorption, the solution containing cobalt ions is prepared by using cobalt sulfate, the concentration of cobalt ions is 10-100mg / L, the concentration of the adsorbent SA is 1-3g / L, and the adsorption time is 1-5h.

[0016] Further, the calcination method in the S1 step is: the sodium alginate is placed in a nitrogen protection atmosphere with a flow rate of 60-100mL / min, heated at a heating rate of 1-10℃ / min to 600-800℃, and then kept for 1-4h.

[0017] Further, the vacuum drying in the S2 or / S3 step is performed at a temperature of 60-80℃ for 12-24h; the washing in the S3 step is performed by using ultrapure water to wash the material three times, and 100mL of ultrapure water is used each time; and the filtering in the S3 step uses a filter membrane with a pore size of 0.45μm.

[0018] A cobalt-based biochar composite material based on sodium alginate prepared by the above preparation method.

[0019] The application of the above-mentioned cobalt-based biochar composite material based on sodium alginate in catalytic persulfate oxidation degradation, and the application in removing organic pollutants in wastewater, are carried out according to the following steps: under stirring conditions, the cobalt-based biochar composite material based on sodium alginate and persulfate are sequentially added into wastewater to react to remove organic pollutants in the wastewater; the mass ratio of the cobalt-based biochar composite material based on sodium alginate, persulfate and organic pollutants is (0.1-1):(0.1-1):(0.01-0.05); the stirring is stirring at a speed of 350-500 r / min at 25 DEG C for 5-30 min, and the pH of the wastewater is 3.5-10.0.

[0020] Further, the mass ratio of the cobalt-based biochar composite material based on sodium alginate, persulfate and organic pollutants is 0.1:0.3:0.01, and in this selected case, the removal effect on organic pollutants is best; the persulfate is persulfate PMS; the addition concentration of the cobalt-based biochar composite material based on sodium alginate is 0.100 g / L, and the addition concentration of the persulfate PMS is 0.3 g / L.

[0021] The cobalt-based biochar composite material based on sodium alginate of the application has a wide application range for the pH value of wastewater, and the degradation efficiency of pollutants in water is hardly affected by the pH value in the water body; the degradation efficiency is not affected by changing the pH value of the wastewater, such as 3.5, 5.6, 6.7, 9.0 and 10.0.

[0022] The cobalt-based biochar composite material based on sodium alginate prepared by the application loads transition metal cobalt in the porous structure of biochar and is doped with N elements, so that the catalyst has a large specific surface and more active sites; the mutual synergistic effect between cobalt, N and the rich active groups on the surface of biochar further promotes the catalytic effect in the oxidation degradation of peroxide; experiments show that cobalt and N can form Co-N coordination to form the main active site Co-Nx of PMS * , so as to activate persulfate to remove organic pollutants; at the same time, the cobalt-based biochar composite catalyst of the application and the persulfate oxidant can form a complex that promotes the reaction, and further improves the efficiency of catalytic oxidation.

[0023] The sodium alginate-based cobalt-based biochar composite material has a removal rate of 100% for organic matter; the sodium alginate-based cobalt-based biochar composite material can be recycled for 4 times, and the removal rate of the organic pollutants can also reach more than 80% after 4 reactions, and is basically not interfered by most inorganic anions and humic acid in water, specifically, the inorganic anions commonly seen in the environment are added in wastewater, and then the step of removing the organic pollutants in water by activating the persulfate by the sodium alginate-based cobalt-based biochar composite material is repeated, and the efficiency of the cobalt-based biochar composite material in activating the persulfate to remove the organic pollutants still reaches more than 90%; the cobalt-based biochar composite material / PMS system can not only efficiently remove the organic pollutants in water bodies, but also has good stability and anti-interference property.

[0024] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0025] (1) Compared with the catalysts such as biochar and metal oxides, the cobalt-based biochar composite material involved in the present application has excellent catalytic ability and good stability, greatly improves the utilization rate of transition metal atoms, and reduces the precipitation of transition metal ions.

[0026] (2) Compared with other Fenton and Fenton-like oxidation systems, the cobalt-based biochar composite material / PMS oxidation system involved in the present application can efficiently and selectively degrade organic matter in water bodies, and the system has excellent anti-interference ability and a wide pH application range. The oxidation system can completely degrade organic pollutants, and therefore has a good application prospect in the field of water pollution treatment.

[0027] (3) The cobalt-based biochar composite material with excellent catalytic ability for persulfate is prepared by simple pyrolysis, activation, grinding and other methods, and the preparation of the cobalt-based biochar composite material is simple, and the requirements for equipment and pyrolysis temperature are low. In addition, the preparation method involved in the present application uses sodium alginate as a carbon source, and compared with traditional chemical ligands (2-methyl imidazole, 1,10-phenanthroline, etc.), the raw materials are safer and more environmentally friendly. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The degradation efficiency of paracetamol by the sodium alginate-based biochar composite material prepared in Example 1 and Comparative Examples 1-3 is shown in the figure.

[0029] Figure 2 The in-situ Raman spectrum of CoNBC prepared in Example 1 in the process of catalytic oxidation degradation is shown in the figure.

[0030] Figure 3 The degradation efficiency of paracetamol by CoNBC prepared in Example 1 under different material concentrations is shown in the figure.

[0031] Figure 4 Figure of degradation efficiency of CoNBC prepared for Example 1 on paracetamol at different PMS concentrations.

[0032] Figure 5 Figure of degradation efficiency of CoNBC prepared for Example 1 on paracetamol in cyclic degradation.

[0033] Figure 6 Figure of degradation efficiency of CoNBC prepared for Example 1 on paracetamol under anions and humic acid.

[0034] Figure 7 Figure of degradation efficiency of CoNBC prepared for Example 1 on paracetamol under different water quality conditions.

[0035] Figure 8 Figure of degradation efficiency of CoNBC prepared for Example 1 on paracetamol at different pH.

[0036] Figure 9 Scanning electron microscope (SEM) and elemental distribution mapping (EDS) images of the material prepared for Example 1.

[0037] Figure 10 X-ray diffraction (XRD) images of the materials prepared for Example 1 and Comparative Examples 1-3.

[0038] Figure 11 X-ray photoelectron spectroscopy (XPS) full spectrum analysis images of the materials prepared for Example 1 and Comparative Examples 1-3. DETAILED DESCRIPTION

[0039] Example 1

[0040] This example is a preparation method of a sodium alginate-based cobalt-based biochar composite material, and the specific steps are as follows:

[0041] (1) Purchase commercially available sodium alginate, first place an appropriate amount of sodium alginate in a tube furnace, first pass nitrogen gas for 20-40 min, flow rate is 60-100 mL / min, to ensure that the tube furnace is completely filled with protective gas; then set the temperature rising program, the temperature rising rate is 1-10 ℃ / min, the temperature is raised to 600-800 ℃, and is retained for 1-4 h, to obtain a biochar of sodium alginate.

[0042] (2) Mix SA and KOH uniformly in a mass ratio of 1:2, place in an agate mortar and grind for 15 min, then pour the ground material (0.5 g) into a beaker containing 500 mL of ultrapure water, activate for 1-8 h, and place the activated SA in a drying oven, set the temperature to 80 ℃, and dry for 12 h, to obtain a derived original biochar SA.

[0043] (3) A certain mass of activated SA was weighed into a solution containing cobalt sulfate (concentration of cobalt ions: 10 mg / L), and adsorbed at a rotation speed of 350 rpm / min for 4 h. The adsorbed material was placed in a vacuum drying oven, the temperature was set to 80°C, and the drying time was 12 h, to obtain a cobalt-containing biochar material, designated as CoSA.

[0044] (4) CoSA was mixed with urea at a mass ratio of 1:1, ground in a marble mortar for 15 min, and then the ground material was placed in a quartz boat and put into a tube furnace. Nitrogen gas was first passed for 30 min at a flow rate of 60 mL / min to ensure that the tube furnace was filled with nitrogen. Then the temperature program was set, the heating rate was 5°C / min, and the temperature was raised from 25°C to 600°C. The black powder was obtained after calcination at 600°C for 1 h. The black powder was washed with ultrapure water three times to remove ash and soluble organic matter, and then filtered through a 0.45 μm filter membrane. The black powder was then placed in a vacuum drying oven, the temperature was set to 80°C, and the drying time was 12 h, to obtain a cobalt-based biochar composite material based on sodium alginate, designated as CoNBC.

[0045] Comparative Example 1

[0046] After repeating steps (1) and (2) of Example 1, the activated SA was ground in a marble mortar for 15 min, and then the ground material was placed in a quartz boat and put into a tube furnace. Nitrogen gas was first passed for 30 min at a flow rate of 60 mL / min to ensure that the tube furnace was filled with nitrogen. Then the temperature program was set, the heating rate was 5°C / min, and the temperature was raised from 25°C to 600°C. The black powder was obtained after calcination at 600°C for 1 h. The black powder was washed with ultrapure water three times to remove ash and soluble organic matter, and then filtered through a 0.45 μm filter membrane. The black powder was then placed in a drying oven, the temperature was set to 80°C, and the drying time was 12 h, to obtain a black powder, designated as BC.

[0047] Comparative Example 2

[0048] After repeating steps (1) and (2) of Example 1, the activated SA and urea were mixed in a 1:1 ratio, ground in a marble mortar for 15 min, and then the ground material was placed in a quartz boat and put into a tube furnace. Nitrogen was first passed for 30 min at a flow rate of 60 mL / min to ensure that the tube furnace was filled with nitrogen. Then, a temperature rising program was set, the temperature was raised at a rate of 5°C / min from 25°C to 600°C, and calcination was performed at 600°C for 1 h to obtain a black powder. The black powder was washed with ultrapure water three times to remove ash and soluble organic matter, filtered through a 0.45 μm filter, and then placed in a drying oven at a temperature of 80°C for 12 h to obtain a cobalt-based biochar composite based on sodium alginate, which was named NBC.

[0049] Comparative Example 3

[0050] After repeating steps (1)-(3) of Example 1, CoSA was ground in a marble mortar for 15 min, and then the ground material was placed in a quartz boat and put into a tube furnace. Nitrogen was first passed for 30 min at a flow rate of 60 mL / min to ensure that the tube furnace was filled with nitrogen. Then, a temperature rising program was set, the temperature was raised at a rate of 5°C / min from 25°C to 600°C, and calcination was performed at 600°C for 1 h to obtain a black powder. The black powder was washed with ultrapure water three times to remove ash and soluble organic matter, filtered through a 0.45 μm filter, and then placed in a drying oven at a temperature of 80°C for 12 h to obtain a black powder, which was named CoBC.

[0051] Example 2

[0052] This example provides the application of the cobalt-based biochar composite based on sodium alginate prepared in Example 1, CoBC, BC and NBC prepared in Comparative Examples 1-3, respectively, in catalytic persulfate oxidation degradation.

[0053] A solution containing 10 ppm of paracetamol was added with CoNBC, CoBC, BC and NBC prepared in Example 1 and Comparative Examples 1-3, respectively, and then with persulfate (PMS) was added to ensure that the concentration of the catalyst material in the system was 0.1 g / L and the concentration of PMS was 0.5 mM. The solution was stirred at a speed of 500 rpm / min at room temperature and atmospheric pressure for 30 min. 0.5 mL of the above PMS-treated water sample was taken, 0.5 mL of methanol was added to terminate the reaction, and the concentration of paracetamol in the water treatment process was detected by high performance liquid chromatography (HPLC). As shown in Table 1, the removal rate of paracetamol in the solution was the highest when CoNBC was used as the catalyst. Figure 1As shown, CoNBC, CoBC, BC, and NBC can all activate PMS and cause varying degrees of degradation of paracetamol. However, the degradation rate of the CoBC, BC, and NBC systems is far lower than that of the CoNBC system. Practice shows that co-doping with cobalt and nitrogen can efficiently improve the catalytic ability of cobalt-based biochar composites for PMS.

[0054] Example 3

[0055] This embodiment is a study on the mechanism of cobalt-based biochar composite material based on sodium alginate provided in Example 1 in the catalytic oxidation and degradation of persulfate, so as to provide a theoretical basis for further improving the catalytic oxidation performance of the composite material, including in the preparation and application of the composite material.

[0056] In this embodiment, acetaminophen (APAP) is used as the organic matter to be oxidized and degraded, and persulfate is permonosulfate PMS.

[0057] Active site determination: Masking experiments were conducted using sodium oxalate (NaC2O4) as a masking agent for single-atom sites. Compared with no masking agent, the results showed that the degradation rate of acetaminophen (APAP) was significantly inhibited after the addition of the masking agent, decreasing from 100% to 60%, indicating that NaC2O4 effectively inhibited the effect of Co-Nx sites. To rule out the contribution of crystalline cobalt encapsulated by the carbon layer, CoNBC was acid-washed for different durations. The experiments showed that acid washing had almost no effect on the catalytic performance of the material, thus ruling out the effect of the coated metal. To further verify the role of Co-Nx sites, the surface structure of CoNBC material before and after use was analyzed. The results showed that the Co-N content on the surface gradually decreased with the increase of catalyst usage. Combined with the catalyst performance analysis, it was inferred that Co-N coordination in this system is the formation of PMS. * The main active site.

[0058] Degradation mechanism: During the catalytic oxidation degradation process, in-situ Raman spectroscopy at different reaction times was used to determine the degradation mechanism. Figure 2 It was found that after the catalyst and oxidant combined, they would reach 600 cm. -1 Up to 800cm -1 A signal peak of the complex appears in the reaction interval. The signal of the complex weakens after the addition of organic pollutants. With increasing reaction time, the signal intensity of this complex peak gradually decreases, indicating that the complex is gradually consumed during the reaction. This result confirms that the complex is the main substance involved in the degradation of acetaminophen (APAP).

[0059] Furthermore, this embodiment also demonstrates that, in addition to paracetamol organic compounds, the cobalt-based biochar composite material based on sodium alginate prepared in this invention can also be used for the oxidative degradation of other organic compounds.

[0060] Example 4

[0061] This example is a performance test of the sodium alginate-based cobalt-based biochar composite material provided in Example 1 for degrading paracetamol at different catalyst concentrations.

[0062] A solution containing 10 ppm of paracetamol was added with CoNBC prepared in Example 1, and PMS was also added to ensure that the CoNBC concentration in the system was 0.013 g / L, 0.025 g / L, 0.05 g / L, 0.075 g / L, and 0.100 g / L, respectively, and the PMS concentration was 0.5 mM. The reaction was stirred magnetically at room temperature and normal pressure for 30 min. During the oxidation degradation reaction, 0.5 mL of the above PMS-treated water sample was taken, 0.5 mL of methanol was added, and the paracetamol concentration in the system during the oxidation degradation reaction was detected by HPLC. As shown in Figure 3 , it is shown that under the above conditions, the catalyst concentration of 0.100 g / L is the most suitable concentration for the reaction system, and is also the most effective catalyst addition concentration.

[0063] Example 5

[0064] This example is a performance test of the sodium alginate-based cobalt-based biochar composite material provided in Example 1 for degrading paracetamol at different persulfate concentrations.

[0065] A solution containing 10 ppm of paracetamol was added with CoNBC prepared in Example 1, and PMS was also added to ensure that the CoNBC concentration in the system was 0.1 g / L, and the PMS concentration was 0.08 g / L, 0.15 g / L, 0.3 g / L, 0.45 g / L, and 0.6 g / L, respectively. The reaction was stirred magnetically at room temperature and normal pressure for 30 min.

[0066] During the oxidation degradation reaction, 0.5 mL of the above PMS-treated water sample was taken, 0.5 mL of methanol was added, and the paracetamol concentration during the oxidation degradation was detected by HPLC. As shown in Figure 4 , under the above conditions, the PMS concentration of 0.3 g / L is the most suitable concentration for the reaction system.

[0067] Example 6

[0068] This example is a material cycle stability test of the sodium alginate-based cobalt-based biochar composite material provided in Example 1 for activating persulfate to degrade paracetamol.

[0069] CoNBC after the reaction of catalytic oxidation degradation of paracetamol in Example 2 was filtered through a 0.45 μm filter membrane, washed with ultrapure water three times, and placed in a vacuum drying oven with a temperature setting of 80℃. After drying for 12 h, the CoNBC was taken out and the steps of adding PMS for reaction treatment in Example 2 were repeated. During the oxidation degradation reaction, 0.5 mL of the water sample after PMS treatment was taken, 0.5 mL of methanol was added, and the concentration of paracetamol was detected by HPLC. As shown in Figure 5 , it can be seen that with the increase of the number of cycles, the removal efficiency decreases, but the removal rate of paracetamol by cobalt-based biochar composite activated persulfate after 5 cycles is still above 80%.

[0070] Example 7

[0071] This example is a test of the anti-interference of the cobalt-based biochar composite based on sodium alginate provided in Example 1 for activating persulfate to degrade paracetamol.

[0072] (1) 10 mM of Cl - , HCO3 - , H2PO4 - and 10 mg / L of humic acid (HA) were added to a 10 ppm paracetamol solution, respectively, and then the cobalt-based biochar composite prepared in Example 1 was added, and PMS was added to ensure that the CoNBC concentration in the system was 0.1 g / L and the PMS concentration was 0.5 mM. The reaction was carried out under normal temperature and pressure with magnetic stirring for 30 min. During the oxidation degradation reaction, 0.5 mL of the water sample after PMS treatment was taken, 0.5 mL of methanol was added, and the concentration of paracetamol was detected by HPLC. As shown in Figure 6 , it can be seen that the removal rate of paracetamol by cobalt-based biochar composite activated persulfate is almost not affected, and the most affected is HCO3 - added to the system, and the removal rate of paracetamol is also above 90%.

[0073] (2) The solvent in the 10 ppm paracetamol solution configured in step (1) was replaced with lake water and tap water, and the cobalt-based biochar composite provided in Example 1 was added, and persulfate was added to ensure that the CoNBC concentration in the system was 0.1 g / L and the PMS concentration was 0.5 mM. The reaction was carried out under normal temperature and pressure with magnetic stirring for 30 min. During the oxidation degradation reaction, 0.5 mL of the water sample after PMS treatment was taken, 0.5 mL of methanol was added, and the concentration of paracetamol was detected by HPLC. As shown in Figure 7 , it can be seen that the removal rate of paracetamol by cobalt-based biochar composite activated persulfate is almost not affected by the different water environments, and the removal rate reaches 100%.

[0074] Example 8

[0075] The pH of the paracetamol-containing solution was adjusted using sodium hydroxide and hydrochloric acid solutions (pH was 3.5, 5.6, 6.7, 9.0 and 10.0, respectively), and then 0.1 g / L of the CoNBC prepared in Example 1 was added to a 10 ppm paracetamol solution, and 0.5 mM of PMS was added at the same time, and the reaction was carried out under normal temperature and pressure for 30 min with magnetic stirring. During the oxidative degradation reaction, 0.5 mL of the above PMS-treated water sample was taken, 0.5 mL of methanol was added, and the paracetamol concentration was detected by HPLC. As shown in Figure 8 , it can be seen that the removal rate of paracetamol by cobalt-based biochar composite activated persulfate is almost not affected by pH, and the removal rate can reach 100%.

[0076] Example 9

[0077] The cobalt-based biochar composite prepared in the above Example 1 was subjected to scanning electron microscope morphology test and EDS element mapping, and the test result analysis is as shown in Figure 9 . As can be seen from the SEM picture of Figure 9 , the prepared cobalt-based biochar composite presents a block structure, and different size of pore structures are exhibited on the surface, and there are some small fragments on the surface of the biochar sample, which may be caused by the interaction between the metal and the surface of the biochar. Through the mapping analysis of the element distribution, it can be seen that the four elements of C, N, O and Co are distributed in the material CoNBC, which further indicates that the method of the present application successfully dopes Co and N into the biochar.

[0078] In addition, the cobalt-based biochar composite prepared in the above Example 1 and Comparative Examples 1-3 was subjected to XRD and XPS analysis, and the test result analysis is as shown in Figure 10 and Figure 11 . The XRD pattern of the catalyst shows a similar diffraction pattern of CoNBC and nitrogen-doped carbon carrier, in which two wide peaks appear at about 24.7° and 44.1°, respectively, corresponding to the graphite (002) and (100) planes, and a relatively sharp peak appears at about 31.5°, which is the peak of metal Na, indicating that the doped material still maintains the carbon quality, and no characteristic peak of Co crystal is found in CoNBC and CoBC. At the same time, the XPS full spectrum of the catalyst shows obvious signals of C, N and O, and the signal intensity of Co is very low, indicating that no Co crystal is found on the surface of the material. This is consistent with the previous results.

[0079] The above detailed description is for the specific description of the feasible embodiments of the present application, and the embodiments are not used to limit the patent scope of the present application. Any equivalent implementation or change without departing from the present application shall be included in the patent scope of the present application.

Claims

1. Use of a sodium alginate-based cobalt-based biochar composite for the removal of paracetamol by persulfate oxidation, characterized in that, The preparation method of the sodium alginate-based cobalt-based biochar composite material comprises the following steps: S1, a proper amount of sodium alginate is calcined, activated and dried to obtain a derived original biochar SA; S2, the derived original biochar SA is used as an adsorbent to adsorb cobalt ions, and then vacuum drying is performed to obtain a cobalt-containing biochar CoSA; S3, the CoSA is uniformly ground with urea, then pyrolysis is performed, and after washing, filtering and vacuum drying, a sodium alginate-based cobalt-based biochar composite material CoNBC is obtained; The calcination method in the S1 step is as follows: the sodium alginate is placed in a nitrogen protective atmosphere with a flow rate of 60-100 mL / min, heated to 600-800℃ at a heating rate of 1-10℃ / min, and then kept for 1-4h; The activation method in the S1 step is as follows: the original biochar SA and potassium hydroxide KOH are mixed uniformly in a ratio of 1:1-4 in a agate mortar, and then the mixture is placed in ultrapure water in a ratio of 0.5g of the ground mixture per 500mL of ultrapure water, and activated for 1-8h; The method for using the derived original biochar SA as an adsorbent to adsorb cobalt ions in the S2 step is as follows: the derived original biochar SA adsorbent is put into a solution containing cobalt ions for adsorption, the solution containing cobalt ions is prepared by using cobalt sulfate, the concentration of cobalt ions is 10-100mg / L, the concentration of the adsorbent is 1-3g / L, and the adsorption time is 1-5h; The pyrolysis method is as follows: heating to 600℃ at a heating rate of 5-15℃ / min, and then pyrolysis treatment is performed for 1h.

2. Use according to claim 1, characterized in that, The mass ratio of the CoSA to urea in the S3 step is 1-3:

1.

3. Use according to claim 1, characterized in that, The vacuum drying in the S2 or / and S3 step is performed at a temperature of 60-80℃ for 12-24h; the washing in the S3 step is performed by using ultrapure water to wash the material three times, and 100mL of ultrapure water is used each time; and the filtering in the S3 step is performed by using a filter membrane with a pore size of 0.45μm.

4. Use according to claim 1, characterized in that, The organic pollutants in the wastewater are removed by sequentially adding the sodium alginate-based cobalt-based biochar composite material and the persulfate salt into the wastewater under stirring to remove the organic pollutants in the wastewater; the mass ratio of the sodium alginate-based cobalt-based biochar composite material, the persulfate salt and the organic pollutants is 0.1-1:0.1-1:0.01-0.05; the stirring is performed at a speed of 350-500r / min at 25℃ for 5-30min; and the pH of the wastewater is 3.5-10.

0.

5. Use according to claim 4, characterized in that, The mass ratio of the sodium alginate-based cobalt-based biochar composite material, the persulfate salt and the organic pollutants is 0.1:0.3:0.01; the persulfate salt is persulfate PMS, the addition concentration of the sodium alginate-based cobalt-based biochar composite material is 0.100g / L, and the addition concentration of the persulfate PMS is 0.3g / L.

Images