Zinc-sulfur co-doped water hyacinth-based biochar and its preparation method and application

Abstract

The present invention provides zinc-sulfur co-doped water hyacinth-based biochar and its preparation method and application, belonging to the field of environmental functional materials. The preparation method of zinc-sulfur co-doped water hyacinth-based biochar comprises: (1) hydroponically cultivating water hyacinth in a ZnSO4 solution to obtain a biomass raw material; (2) subjecting the biomass raw material obtained in step (1) to a first pyrolysis treatment, and grinding to obtain prefabricated biochar; (3) deashing the prefabricated biochar prepared in step (2), and then subjecting it to a second pyrolysis treatment, and finally grinding, washing, and drying to obtain zinc-sulfur co-doped water hyacinth-based biochar. The zinc-sulfur co-doped water hyacinth-based biochar is both an activator for persulfate oxidation and a catalyst for photoactivated persulfate oxidation, and is the key to optimizing the synergistic effect of the persulfate / ultraviolet advanced oxidation system (PS / UV).

Description

Technical Field

[0001] The present invention relates to the field of environmental functional materials, and in particular to zinc-sulfur co-doped water hyacinth-based biochar, and a preparation method and application thereof. Background Art

[0002] Tetracyclines (TC) were discovered and reported in the 1940s as a natural product of soil bacteria and were quickly commercialized through clinical application. They are a group of well-tolerated, easily administered, broad-spectrum antibiotics widely used in human and veterinary medicine, aquaculture, and agriculture. However, due to poor absorption and metabolism in humans and animals, TC is excreted as the parent compound and accumulates in the environment. This leads to a gradual increase in chronic drug toxicity in water and soil and the spread of antibiotic-resistant genes, posing a long-term threat to ecosystems and human health. Furthermore, it is important to note that global antibiotic consumption has increased significantly since the beginning of the 21st century. This dramatic increase in the use of all antibiotics, including TC, has led to an increase in the amount of pharmaceutical wastewater containing high concentrations of TC residues, posing a greater threat to ecosystems and human health.

[0003] Over the past few years, persulfate-based advanced oxidation processes (AOPs) have been considered a highly competitive technology in the water treatment field. This is due to the numerous methods available for activating persulfate (PS), making it suitable for use in water environments with a wide pH range. PS also offers advantages such as ease of transportation and storage, abundant catalyst sources, and low catalyst costs. Currently, the application of PS-activated AOPs systems for TC removal in water has been widely studied. However, this research primarily focuses on wastewaters with TC concentrations below 50 mg / L, while high-concentration pharmaceutical wastewaters often have TC concentrations exceeding 200 mg / L, requiring systems with higher removal efficiencies. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a zinc-sulfur co-doped water hyacinth-based biochar and a preparation method thereof. The biochar serves as an activator and catalyst for a persulfate / ultraviolet advanced oxidation system (PS / UV), which can achieve efficient removal of high-concentration TC wastewater.

[0005] The technical solutions of the present invention are as follows:

[0006] The present invention provides a method for preparing zinc-sulfur co-doped water hyacinth-based biochar, comprising the following steps:

[0007] (1) preparing biomass raw materials: hydroponically cultivating water hyacinth in a ZnSO4 solution to obtain biomass raw materials;

[0008] (2) Preparing prefabricated biochar: subjecting the biomass raw material obtained in step (1) to a first pyrolysis treatment and grinding to obtain prefabricated biochar;

[0009] (3) Preparation of zinc-sulfur co-doped water hyacinth-based biochar: The prefabricated biochar prepared in step (2) is first subjected to a deashing treatment, then subjected to a second pyrolysis treatment, and finally ground, washed, and dried to obtain zinc-sulfur co-doped water hyacinth-based biochar.

[0010] In one embodiment, in step (1), the water hyacinth is in the growth stage; the concentration of the ZnSO4 solution is 50-1000 mg / L; preferably, the concentration of the ZnSO4 solution is 200 mg / L; the time of directional hydroponics is 10-60 days; preferably, the time of directional hydroponics is 24 days.

[0011] In one embodiment, in step (2), the specific steps of the first heat treatment are: heating to 400-600°C at a heating rate of 3-8°C / min under a protective atmosphere, keeping warm for 1-3h, then cooling to 70-90°C at a rate of 3-8°C / min, and then naturally cooling to room temperature.

[0012] Preferably, in step (2), the specific steps of the first heat treatment are: heating to 600°C at a heating rate of 5°C / min under a protective atmosphere, keeping warm for 2h, then cooling to 80°C at a rate of 5°C / min, and then naturally cooling to room temperature.

[0013] Preferably, the flow rate of the protective atmosphere is 80 mmHg / min.

[0014] In the present invention, the protective atmosphere is an atmosphere that does not participate in the reaction, for example, nitrogen atmosphere, helium atmosphere, argon atmosphere, etc.

[0015] In one embodiment, in step (3), the specific steps of the deashing treatment are: mixing the prefabricated biochar prepared in step (2) with alkali and water in a mass ratio of 1:3-5:30, soaking for 0.5-2 hours, and heating the mixture at 80-120° C. until the solution mixture becomes a slurry and then stopping the heating.

[0016] Preferably, the base is potassium hydroxide and / or sodium hydroxide.

[0017] Preferably, in step (3), the specific steps of the deashing treatment are: mixing the prefabricated biochar prepared in step (2) with alkali and water in a mass ratio of 1:4:30, soaking for 1 hour, heating the mixture at 100°C until the solution mixture becomes a slurry, stopping heating and performing drying after the deashing treatment.

[0018] In one embodiment, in step (3), the specific steps of the second pyrolysis treatment are: under a protective atmosphere, heating the temperature to 300-400°C at a heating rate of 3-8°C / min, keeping the temperature for 1-3 hours, then heating the temperature to 750-900°C at the same rate, keeping the temperature for 1-3 hours, and then naturally cooling the temperature to 40-60°C.

[0019] Preferably, in step (3), the specific steps of the second pyrolysis treatment are: at room temperature, heating to 350°C at a rate of 5°C / min, keeping warm for 1 hour, then heating to 800°C at the same rate, keeping warm for 1 hour, and then naturally cooling to 45°C; the specific steps of washing are: washing with 5-10wt.% hydrochloric acid until the small boiling phenomenon disappears, then washing with ethanol three to five times, and finally washing repeatedly with water until the pH of the washing solution is neutral.

[0020] The present invention also provides zinc-sulfur co-doped water hyacinth-based biochar prepared by the above preparation method.

[0021] The present invention also provides the use of the zinc-sulfur co-doped water hyacinth-based biochar in persulfate oxidation and degradation of organic pollutants or photoactivated persulfate oxidation and degradation of organic pollutants.

[0022] The principle of persulfate advanced oxidation (APO) is based on the cleavage of peroxy bonds in persulfate molecules, triggering a chain reaction that produces oxygen-containing species such as persulfate radicals, hydroxyl radicals, superoxide radicals, and singlet oxygen, which degrade the target compound. While this study only tested the degradation of tetracycline wastewater, based on the principle of APO, the zinc-sulfur co-doped water hyacinth-based biochar of this invention is also suitable for persulfate oxidation and degradation of other organic pollutants.

[0023] In a specific embodiment, the organic pollutant is a tetracycline antibiotic; the application is to first mix the zinc-sulfur co-doped water hyacinth-based biochar with the tetracycline antibiotic wastewater for 20-60 minutes, and then add persulfate to start the degradation reaction; preferably, the zinc-sulfur co-doped water hyacinth-based biochar is mixed with the tetracycline antibiotic wastewater for 30 minutes.

[0024] In one specific embodiment, the mass ratio of zinc-sulfur co-doped water hyacinth-based biochar, persulfate and tetracycline antibiotics is 0.1-0.5:0.2-0.4:0.1-0.5; preferably, the mass ratio of zinc-sulfur co-doped water hyacinth-based biochar, persulfate and tetracycline antibiotics is 0.3:0.28:0.25.

[0025] In one embodiment, the application is as follows: in the dark, the zinc-sulfur co-doped water hyacinth-based biochar is mixed with tetracycline antibiotic wastewater for 30 minutes, and then persulfate is added, the reaction is continued for 60 minutes, and then the reaction is continued under ultraviolet light for 120-180 minutes.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] By combining targeted hydroponics of water hyacinth with zinc sulfide solution and pyrolysis activation, a zinc-sulfur co-doped water hyacinth-based biochar with high activation and catalytic performance was obtained. This overcomes technical challenges such as agglomeration of the loaded materials and secondary pollution caused by metal shedding during water treatment. Applied to the persulfate degradation of organic pollutants, the zinc-sulfur co-doped water hyacinth-based biochar acts as both an activator and a catalyst for photoactivated persulfate oxidation, making it key to optimizing the PDS / UV synergistic effect and enabling efficient degradation of high-concentration TC wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The photos are of water hyacinth grown in hydroponic culture with 200mg / L ZnSO4 solution on the 1st, 5th, 10th, 15th and 24th days;

[0029] Figure 2 , (a) is the XRD spectra of HBC and ZSHBC, (b) is the TEM images of HBC and ZSHBC, and (c) is the element distribution diagram of C, O, N, S and Zn of ZSHBC;

[0030] Figure 3 Nitrogen adsorption-desorption isotherms of HBC, ZSHBC, and Zn / S@BC;

[0031] Figure 4 This is a comparative line graph showing the change in the residual rate of TC in the TC solution as a function of reaction time in Examples 2-4;

[0032] Figure 5 This is a comparative line graph showing the change in the residual rate of TC in the TC solution as a function of reaction time in Examples 3, 5, and 6;

[0033] Figure 6 This is a comparative line graph showing the change in the residual rate of TC in the TC solution as a function of reaction time in Example 2, Example 3, and Comparative Examples 3-5;

[0034] Figure 7 A comparative line graph showing the change in the residual rate of TC in the TC solution as a function of reaction time in Example 3 and Comparative Example 6;

[0035] Figure 8This is a bar chart of the zinc ion content in the reaction solution collected after 180 minutes of reaction, which is collected in Example 3 and Comparative Example 7. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0037] Example 1

[0038] Preparation of zinc-sulfur co-doped water hyacinth-based biochar

[0039] Water hyacinths in the growing period were collected from lakes, washed with deionized water, and transferred to hydroponic pots. A 200 mg / L ZnSO4·7H2O solution was prepared for directional hydroponics. After 24 days, the zinc-sulfur-rich plants were collected, washed with deionized water, cut into smaller pieces with scissors, and placed in a forced air drying oven at 80°C for 48 hours. The dried raw materials were then transferred to a tube furnace and heated to 600°C at a heating rate of 5°C / min. Nitrogen gas at a flow rate of 80 mmHg / min was introduced and maintained in the nitrogen atmosphere for 2 hours. The temperature was then reduced to 80°C at a rate of 5°C / min and naturally cooled to room temperature. The obtained prefabricated biochar was ground, passed through a 200-mesh sieve, dried, and placed in a beaker with KOH in a mass ratio of 1:4. 30 ml of deionized water was added and stirred thoroughly. The beaker was sealed with plastic wrap and soaked for 1 hour. After soaking, the plastic wrap was removed and the mixture was heated in a water bath at 100 ° C to evaporate the water. The sample powder stuck to the wall of the beaker was washed off with a wash bottle for about half an hour until the solution mixture became a slurry or there was a little water. The heating was stopped and the beaker containing the sample was transferred to an 80 ° C drying oven and dried for 12 hours. The sample was then transferred to a tubular furnace. The pyrolysis process was as follows: under a protective atmosphere, the temperature was increased from 20 ° C to 350 ° C at a rate of 5 ° C / min and kept warm for 1 hour, and then increased to 800 ° C at the same rate and kept warm for 1 hour, and then it was naturally cooled to 45 ° C, taken out and poured into a mortar for grinding. The ground sample was washed with a Buchner funnel, and the process was as follows: the activated sample was washed with 10wt% HCl. When washing with HCl, KOH would react with it and a small boiling phenomenon would be seen. HCl was used until this phenomenon disappeared, and then it was washed three times with ethanol. Finally, it was repeatedly washed with deionized water until the pH of the washing solution was neutral. Finally, it was placed in an oven at a temperature of 120°C and dried for 24 hours to obtain a sample named ZSHBC.

[0040] In this embodiment, the photos of water hyacinth on the 1st, 5th, 10th, 15th and 24th days of directional hydroculture in ZnSO4·7H2O solution are shown in FIG. Figure 1 shown.

[0041] Comparative Example 1

[0042] Preparation of undoped water hyacinth-based biochar materials

[0043] The method is basically the same as Example 1, except that the ZnSO4·7H2O solution is replaced by an aqueous solution. The functional biochar material obtained in Comparative Example 1 is named HBC.

[0044] Comparative Example 2

[0045] Preparation of modified water hyacinth-based biochar composites using traditional vacuum infiltration method

[0046] Water hyacinths were collected from lakes during their growth phase, cleaned with deionized water, cut into smaller pieces with scissors, and dried in a forced-air drying oven at 80°C for 48 hours. The dried raw material was then pulverized and passed through a 50-mesh sieve. 30g of the sieved powder was then added to 60g of a 200mg / L ZnSO4 aqueous solution at 80°C, stirred at 200 rpm for 8 hours, and then removed and washed with deionized water until the solution was neutral. The washed powder was then dried in a vacuum drying oven at 80°C for at least 12 hours to produce a composite material precursor. The precursor was transferred to a tube furnace and heated to 600°C at a heating rate of 5°C / min. Nitrogen gas was introduced at a flow rate of 80 mmHg / min and maintained under a nitrogen atmosphere for 2 hours. The temperature was then reduced to 80°C at a rate of 5°C / min and naturally cooled to room temperature. The obtained prefabricated biochar was ground, passed through a 200-mesh sieve, dried, and placed in a beaker with KOH in a mass ratio of 1:4. 30 ml of deionized water was added and stirred thoroughly. The beaker was sealed with plastic wrap and soaked for 1 hour. After soaking, the plastic wrap was removed and the mixture was heated in a water bath at 100 ° C to evaporate the water. The sample powder stuck to the wall of the beaker was washed off with a wash bottle for about half an hour until the solution mixture became a slurry or there was a little water. The heating was stopped and the beaker containing the sample was transferred to an 80 ° C drying oven and dried for 12 hours. The sample was then transferred to a tubular furnace. The pyrolysis process was as follows: under a protective atmosphere, the temperature was increased from 20 ° C to 350 ° C at a rate of 5 ° C / min and kept warm for 1 hour, and then increased to 800 ° C at the same rate and kept warm for 1 hour, and then it was naturally cooled to 45 ° C and taken out and poured into a mortar for grinding. The ground sample was washed with a Buchner funnel, and the process was as follows: the activated sample was washed with 10wt% HCl. When washing with HCl, KOH would react with it and a small boiling phenomenon would be seen. HCl was used until this phenomenon disappeared, and then it was washed three times with ethanol. Finally, it was repeatedly washed with deionized water until the pH of the washing solution was neutral. Finally, it was placed in an oven at a temperature of 120°C and dried for 24 hours to obtain a sample named Zn / S@BC.

[0047] The XRD patterns and TEM images of ZSHBC and HBC are shown in Figure 2 (a) and (b) are shown in Figure 2. The distribution of C, O, N, S and Zn elements in ZSHBC is shown in Figure 2. Figure 2 As shown in (c) in .

[0048] from Figure 2 It can be seen that ZSHBC is a Zn and S co-doped functional biochar. Zn and S are highly dispersed on the surface of the carbon matrix without agglomeration. Zn mainly exists in the form of ZnO, ZnS and Zn.

[0049] Figure 3 The nitrogen adsorption-desorption isotherms of ZSHBC, Zn / S@BC and HBC at 77 K were tested by Brunauer-Emmett-Teller (BET, Quantachrome NOVA1000), and the structural parameters of ZSHBC, Zn / S@BC and HBC were calculated by density functional theory (DFT) analysis, as shown in Table 1.

[0050] Table 1. Structural parameters of ZSHBC and HBC calculated by DFT analysis

[0051]

[0052] Example 2

[0053] A ZSHBC-PDS (dark) system was designed: First, 12 mg of ZSHBC was thoroughly mixed with 40 mL of a 250 mg / L high-concentration TC solution in a conical flask under dark conditions for 30 minutes to ensure adsorption saturation and eliminate interference with the subsequent advanced oxidation reaction. Continuing in the dark, 11.2 mg of PDS was injected into the conical flask to initiate the reaction, which continued for 180 minutes. During the reaction, 0.5 mL samples were taken at time points (0, 10, 20, 30, 45, 60, 65, 70, 80, 90, 120, and 180 minutes). The samples were filtered through a 0.45 μm polyethersulfone (PES) filter, collected in a brown centrifuge tube, and diluted. The residual TC in the TC solution was immediately analyzed by UV spectrophotometry and TOC analysis. After 180 minutes of reaction, the TC removal rate reached 85.95%.

[0054] Example 3

[0055] A ZSHBC-PDS / UV (delayed illumination) synergistic AOP system was designed: First, 12 mg of ZSHBC biochar catalytic activator was thoroughly mixed with 40 ml of a 250 mg / L high-concentration TC solution in a conical flask in the dark for 30 minutes to ensure adsorption saturation and eliminate interference with the subsequent advanced oxidation reaction. The reaction was then initiated by injecting 11.2 mg of PDS into the conical flask. After 60 minutes of reaction, a xenon lamp was turned on and the reaction continued under UV illumination for 180 minutes. During the reaction, 0.5 ml samples were taken at time points (0, 10, 20, 30, 45, 60, 65, 70, 80, 90, 120, and 180 minutes). The samples were filtered through a 0.45 μm polyethersulfone (PES) filter, collected in a brown centrifuge tube, and diluted. The residual TC in the TC solution was immediately analyzed by UV spectrophotometry and TOC analysis. After 180 minutes of reaction, the TC removal rate reached 95.23%.

[0056] Example 4

[0057] A ZSHBC-PDS / UV (normal light) synergistic AOP system was designed: First, in the dark, 12 mg of ZSHBC biochar catalytic activator was thoroughly mixed with 40 ml of a 250 mg / L high-concentration TC solution in an Erlenmeyer flask for 30 minutes to ensure adsorption saturation and eliminate interference with the subsequent advanced oxidation reaction. The reaction was then initiated by injecting 11.2 mg of PDS into the Erlenmeyer flask, while a xenon lamp was turned on, and the reaction continued for 180 minutes. During the reaction, 0.5 ml samples were taken at time points (0, 10, 20, 30, 45, 60, 65, 70, 80, 90, 120, and 180 minutes). The samples were filtered through a 0.45 μm polyethersulfone (PES) filter, collected in a brown centrifuge tube, and diluted. The residual TC in the TC solution was immediately analyzed by UV spectrophotometry and TOC analysis. After 180 minutes of reaction, the TC removal rate reached 91.31%.

[0058] Example 2-4, the comparison line graph of the change of the residual rate of TC in the TC solution with the reaction time is shown in Figure 4 shown.

[0059] Example 5

[0060] Design of ZSHBC-PDS / UV (delayed illumination) synergistic AOP system: basically the same as Example 3, except that the concentration of TC solution was different, 150 mg / L. After 180 minutes of reaction, the TC removal rate reached 99.06%.

[0061] Example 6

[0062] Design of ZSHBC-PDS / UV (delayed illumination) synergistic AOP system: basically the same as Example 3, except that the concentration of TC solution was different, 50 mg / L. After 180 minutes of reaction, the TC removal rate reached 100%.

[0063] The comparison line graph of the residual rate of TC in TC solution versus reaction time for Example 3, Example 5, and Example 6 is shown in FIG. Figure 5 shown.

[0064] The TOC of the wastewater before and after the reaction of Example 3, Example 5 and Example 6 was measured using a Shimadzu TOC-4100 total organic carbon analyzer, and the mineralization rates of the wastewater were calculated to be 92.53%, 98.72% and 100%, respectively.

[0065] Comparative Example 3

[0066] Design of the PDS (dark) system: basically the same as Example 2, except that no ZSHBC was added in this comparative example. After 180 minutes of reaction, the TC removal rate was only 13.53%.

[0067] Comparison between this comparative example and Example 2 shows that ZSHBC is a highly efficient PDS activator.

[0068] Comparative Example 4

[0069] PDS / UV (delayed illumination) system: This is essentially the same as Example 3, except that this comparative example does not include ZSHBC. First, in the dark, 40 ml of a 250 mg / L high-concentration TC solution was injected into an Erlenmeyer flask. 30 minutes later, 11.2 mg of PDS was injected into the flask to initiate the reaction. After 60 minutes of reaction, a xenon lamp was turned on and the reaction continued under UV light for 180 minutes. During the reaction, 0.5 ml samples were taken at time points (0, 10, 20, 30, 45, 60, 65, 70, 80, 90, 120, and 180 minutes). The samples were then filtered through a 0.45 μm polyethersulfone (PES) filter, collected in a brown centrifuge tube, and diluted. The TC solution was then immediately analyzed for residual TC using UV spectrophotometry and a TOC test. After 180 minutes of reaction, the TC removal rate was only 19.41%.

[0070] Comparative Example 5

[0071] UV (delayed light) system: basically the same as Comparative Example 4, except that PDS was not added in this comparative example. After 180 minutes of reaction, the TC removal rate was only 10.64%.

[0072] Comparison of Comparative Examples 4-5 with Example 3 shows that without ZSHBC as a medium, it is difficult for UV to directly activate PDS and thus difficult to remove TC. The addition of ZSHBC to the PDS / UV (delayed illumination) system is the key to removing high-concentration TC.

[0073] The comparison line graph of the variation of the residual rate of TC in the TC solution with the reaction time for Example 2, Example 3 and Comparative Examples 3-5 is shown in FIG. Figure 6 shown.

[0074] Comparative Example 6

[0075] Design of HBC-PDS / UV (delayed illumination) synergistic AOP system: basically the same as Example 3, except that ZSHBC was replaced with HBC in this comparative example. After 180 minutes of reaction, the TC removal rate was only 24.77%.

[0076] The comparison line graph of the variation of the residual rate of TC in the TC solution with the reaction time of Example 3 and Comparative Example 6 is shown in FIG. Figure 7 shown.

[0077] Comparative Example 7

[0078] A Zn / S@BC-PDS / UV (delayed illumination) synergistic AOP system was designed: First, 12 mg of Zn / S@BC biochar composite was thoroughly mixed with 40 ml of a 250 mg / L high-concentration TC solution in a conical flask in the dark for 30 minutes. Then, 11.2 mg of PDS was injected into the flask to initiate the reaction. After 60 minutes, a xenon lamp was turned on and the reaction continued under UV light for 180 minutes. The reaction solution was then filtered through a 0.45 μm polyethersulfone (PES) filter and collected in a brown centrifuge tube. After 180 minutes of reaction, the TC removal rate was only 65.7%.

[0079] The reaction solution collected after 180 min of reaction in Example 3 and Comparative Example 7 was immediately tested for zinc ion content using ICP-MS. The results are shown in Table 1. Figure 8 As shown by Figure 8 It can be seen that after using Zn / S@BC to treat the wastewater, the zinc ion concentration in the wastewater is as high as 33.4 mg / L, and zinc ions show obvious leakage; while the zinc ion concentration in the wastewater after ZSHBC treatment in Example 3 is only 0.78 mg / L, which meets the requirement of the second-class surface water zinc ion concentration (1.0 mg / L) in the Surface Water Environmental Quality Standard (GB3838-2002) and will not cause secondary water pollution.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing zinc-sulfur co-doped water hyacinth-based biochar, characterized in that: The steps include: (1) preparing biomass raw materials: hydroponically cultivating water hyacinth in a ZnSO4 solution to obtain biomass raw materials; (2) Preparation of prefabricated biochar: The biomass raw material obtained in step (1) is subjected to a first pyrolysis treatment and then ground. obtaining prefabricated biochar; (3) Preparation of zinc-sulfur co-doped water hyacinth-based biochar: The prefabricated biochar prepared in step (2) is first subjected to a deashing treatment, then subjected to a second pyrolysis treatment, and finally ground, washed, and dried to obtain zinc-sulfur co-doped water hyacinth-based biochar.

2. The method for preparing zinc-sulfur co-doped water hyacinth-based biochar according to claim 1, characterized in that: In step (1), the water hyacinth is in the growth period; and the concentration of the ZnSO4 solution is 50-1000 mg / L.

3. The method for preparing zinc-sulfur co-doped water hyacinth-based biochar according to claim 2, characterized in that: The concentration of ZnSO4 solution is 200 mg / L; the time of directional hydroponics is 10-60 days.

4. The method for preparing zinc-sulfur co-doped water hyacinth-based biochar according to claim 2, characterized in that: The duration of directional hydroponics is 24 days.

5. The method for preparing zinc-sulfur co-doped water hyacinth-based biochar according to claim 1, characterized in that: In step (2), the specific steps of the first heat treatment are: heating to 400-600°C at a heating rate of 3-8°C / min under a protective atmosphere, keeping warm for 1-3h, then cooling to 70-90°C at a rate of 3-8°C / min, and then naturally cooling to room temperature.

6. The method for preparing zinc-sulfur co-doped water hyacinth-based biochar according to claim 1, characterized in that: In step (3), the specific steps of the deashing treatment are: mixing the prefabricated biochar prepared in step (2) with alkali and water in a mass ratio of 1:3-5:30, soaking for 0.5-2 hours, and heating the mixture at 80-120° C. until the solution mixture becomes a slurry and then stopping the heating.

7. The method for preparing zinc-sulfur co-doped water hyacinth-based biochar according to claim 1, characterized in that: In step (3), the specific steps of the second pyrolysis treatment are: under a protective atmosphere, heating the temperature to 300-400°C at a heating rate of 3-8°C / min, keeping the temperature for 1-3 hours, then heating the temperature to 750-900°C at the same rate, keeping the temperature for 1-3 hours, and then naturally cooling the temperature to 40-60°C; the specific steps of washing are: washing with 5-10wt.% hydrochloric acid until the small boiling phenomenon disappears, then washing with ethanol three to five times, and finally washing repeatedly with water until the pH of the washing solution is neutral.

8. Zinc-sulfur co-doped water hyacinth-based biochar prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the zinc-sulfur co-doped water hyacinth-based biochar according to claim 8 in persulfate oxidation degradation of organic pollutants or photoactivated persulfate oxidation degradation of organic pollutants.

10. The use according to claim 9, characterized in that The organic pollutants are tetracycline antibiotics; the application is to first mix zinc-sulfur co-doped water hyacinth-based biochar with tetracycline antibiotic wastewater for 20-60 minutes, and then add persulfate to start the degradation reaction.

11. The use according to claim 10, characterized in that Zinc and sulfur co-doped water hyacinth-based biochar was mixed with tetracycline antibiotic wastewater for 30 minutes.

12. The use according to claim 11, characterized in that The mass ratio of zinc-sulfur co-doped water hyacinth-based biochar, persulfate and tetracycline antibiotics is 0.1-0.5:0.2-0.4:0.1-0.

5.

13. The use according to claim 12, characterized in that The mass ratio of zinc-sulfur co-doped water hyacinth-based biochar, persulfate and tetracycline antibiotics was 0.3:0.28:0.

25.

14. The use according to claim 11, characterized in that The application is as follows: in the dark, the zinc-sulfur co-doped water hyacinth-based biochar is mixed with tetracycline antibiotic wastewater for 30 minutes, and then persulfate is added, the reaction continues for 60 minutes, and then the reaction is continued for 120-180 minutes under ultraviolet light.

Images