Preparation method of manganese ferrite and manganese dioxide core-shell material based on monatomic cobalt doping and application of manganese ferrite and manganese dioxide core-shell material in efficient generation of Fe (IV) targeted thallium removal

Abstract

The invention discloses a preparation method of a manganese ferrite and manganese dioxide core-shell material based on monatomic cobalt doping and application of the manganese ferrite and manganese dioxide core-shell material in efficient generation of Fe (IV) targeted thallium removal, and belongs to the field of environmental functional materials and advanced oxidation treatment of heavy metal wastewater. The invention aims to solve the problem of low removal rate of thallium in wastewater. The method comprises the following steps: 1, preparing ZIF-8 (at) Co; 2, a Co-N4 / MnFe2O4 core is prepared, and the Co-N4 / (3) preparing Co-N4 / MnFe2O4 (at) MnO2; 4, PSS surface modification; and 5, loading and sealing double oxidants. Through Co-N4 / Mn < 2 + > dual catalysis and KHSO5 / CaO2 synergistic oxidation, the yield gt of Fe (IV) is realized in a complex water body; 90% and the Tl removal rate gt; 99.9% by weight; the PSS modified shell layer shields hardness interference, the TiO2-x / PDA layer photolyzes organic matters, the cost is low, and the bottleneck of the existing thallium removal technology is broken through.

Description

Technical Field

[0001] The invention belongs to the field of environmental functional materials and advanced oxidation treatment of heavy metal wastewater. Background Art

[0002] Tetravalent iron (Fe(IV)) has strong oxidizing properties (standard oxidation potential E 0 = +2.4V), can completely oxidize the thallium ions (Tl + →Tl 3+ ), generating Tl(OH)3 (K sp =10 -45 ), which is more selective than traditional oxidants (such as chlorine and ozone). However, traditional chemical methods (such as Fe 2+ The Fe(IV) generation efficiency in activated persulfate is generally less than 60%, and is easily driven by free radical pathways (SO4• - / •OH) competition, resulting in incomplete oxidation; at the same time, the acidic environment (pH = 3-5) must be strictly controlled to maintain the stability of Fe(IV), as neutral / alkaline conditions easily lead to inactivation; traditional chemical materials are mostly non-recyclable (such as potassium ferrate, which is easily decomposed), or their activity drops sharply after regeneration (cycles < 5 times, efficiency drops by > 50%), resulting in high treatment costs and complex operations. In addition, there are high hardness ions (> 500 mg / L Ca 2+ / Mg 2+ ) will block pores or compete for adsorption sites, causing the thallium removal efficiency to drop by >40%; organic matter (such as humic acid HA>50mg / L) covers active sites or consumes Fe(IV), resulting in a removal rate drop of >30%. Summary of the Invention

[0003] The purpose of the present invention is to solve the problem of low thallium removal rate in wastewater and provide a preparation method of manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping and its application in the efficient generation of Fe(IV) for targeted thallium removal.

[0004] The present invention prepares a manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping. Through dual oxidant triggering and surface functionalization design, it realizes the efficient and directional generation of Fe(IV) and the targeted removal of thallium in complex water bodies.

[0005] The present invention provides a targeted anti-interference core-shell material, which is 2+ Dual catalysis and KHSO5 / CaO2 synergistic oxidation achieved Fe(IV) yields >90% and Tl removal rates >99.9% in complex water bodies; PSS modified shell (Co-N4MnFe2O4@MnO2-PSS) shielded hardness interference, TiO 2-x / PDA layer photolyzes organic matter, removes water and breaks through the bottleneck of existing thallium removal technology.

[0006] In the manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping prepared by the present invention:

[0007] ① Core: The Co-N4 / MnFe2O4 core prepared in the present invention is a single-atom Co-doped MnFe2O4 nanosphere with a particle size of 50±5nm and a saturation magnetization of ≥45 emu / g. The single-atom Co exists in the form of Co-N4 coordination, and the Co loading is 1-2wt%;

[0008] ② Shell layer: The shell layer prepared by the present invention is: PSS-modified mesoporous MnO2 nanosheets (MnFe2O4@MnO2-PSS, thickness 20±2 nm, pore size 5 nm), with a PSS grafting density of 0.8-1.2 mmol / g;

[0009] ③ Load: KHSO5 and CaO2 (molar ratio (3~4):1) are loaded and encapsulated in the MnO2 mesopores;

[0010] ④. Surface sealing layer: TiO 2-x / PDA film (thickness <5 nm).

[0011] A manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping is used for efficient generation of Fe(IV) for targeted thallium removal.

[0012] A method for preparing a manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping is specifically completed by the following steps:

[0013] 1. Preparation of ZIF-8@Co:

[0014] ① Dissolve Zn(NO3)2 and Co(NO3)2 in methanol and stir evenly to obtain solution A;

[0015] ② Dissolve 2-methylimidazole in 100 mL of methanol and stir evenly to obtain solution B;

[0016] ③. Mix solution B and solution A evenly, and then stir in a water bath at 25°C for a period of time to obtain reaction product I;

[0017] ④. Centrifuge the reaction product I, wash it, and dry it to obtain ZIF-8@Co;

[0018] 2. Preparation of Co-N4 / MnFe2O4 core:

[0019] ①. Bubble nitrogen into the water to remove oxygen, then dissolve FeCl3 and MnCl2 in oxygen-free water to obtain solution C;

[0020] ② Add ZIF-8@Co to solution C, disperse under ultrasonication for a period of time, then add NaOH solution dropwise until the pH of the system reaches 12, and heat the reaction for a period of time to obtain reaction product II;

[0021] ③. Filter the reaction product II and then wash the obtained solid matter to obtain a precursor;

[0022] ④. Place the precursor in a tube furnace, pyrolyze it under a nitrogen atmosphere, and cool it to room temperature to obtain the Co-N4 / MnFe2O4 core;

[0023] 3. Preparation of Co-N4 / MnFe2O4@MnO2:

[0024] ① Dissolve hexadecyltrimethylammonium bromide in ultrapure water at 60-70°C, add Co-N4 / MnFe2O4 cores, and sonicate for a period of time to obtain solution D.

[0025] ②. Add KMnO4 solution dropwise to solution D and stir at 70°C for a period of time to obtain reaction product III;

[0026] ③. Centrifuge the reaction product III and wash the resulting solid to obtain Co-N4 / MnFe2O4@MnO2, which is a core-shell intermediate;

[0027] 4. PSS surface modification:

[0028] ① Immerse the core-shell intermediate in an aqueous solution of sodium polystyrene sulfonate, stir at 80°C to 90°C for a period of time, then add a crosslinker solution and continue heating and stirring to crosslink for a period of time to obtain reaction product IV;

[0029] ②, centrifuge the reaction product IV and then wash it to obtain Co-N4 / MnFe2O4@MnO2-PSS;

[0030] 5. Dual oxidant loading and sealing:

[0031] ①, Mix KHSO5 and CaO2, and ball-mill them to a particle size of <5μm to obtain an oxidant mixed powder;

[0032] ② Place Co-N4 / MnFe2O4@MnO2-PSS in a vacuum drying oven, raise the temperature to 50°C under a reduced pressure of -0.1 MPa, spray the oxidant mixed powder onto the Co-N4 / MnFe2O4@MnO2-PSS, and maintain the pressure at -0.1 MPa and 50°C for 2 hours to obtain Co-N4 / MnFe2O4@MnO2-PSS-OX;

[0033] ③ Preparation of TiO 2-x / PDA sealing layer:

[0034] a. Dissolve Ti(OBu)4 in anhydrous ethanol and stir magnetically for a period of time to obtain solution A; dissolve NaBH4 in ultrapure water and dissolve it by ultrasonic for a period of time to obtain solution B; add solution B dropwise to solution A to obtain a blue sol; transfer the blue sol to a polytetrafluoroethylene-lined reactor and perform hydrothermal reaction at 160°C for 10-12 hours to obtain reaction product V; centrifuge reaction product V, wash the obtained solid matter, and vacuum dry to obtain TiO 2-x ;

[0035] b: Dopamine hydrochloride was dissolved in Tris-HCl buffer, and nitrogen was introduced into the solution for a period of time to deoxygenate it to obtain a PDA prepolymer solution; TiO 2-x Dissolve in anhydrous ethanol, add dispersant, and ultrasonicate for a period of time to obtain TiO 2-x dispersion; TiO 2-x The dispersion was added to the PDA prepolymer solution and stirred at 25°C in the dark for a period of time to obtain a gray-blue composite dispersion;

[0036] ④. Immerse Co-N4 / MnFe2O4@MnO2-PSS-OX into the gray-blue composite dispersion, oscillate and deposit for a period of time at 25°C and in the dark, and then oscillate and deposit for a period of time under heating and in the dark to obtain Co-N4 / MnFe2O4@MnO2-PSS-OX@PDA / TiO 2-x , which is a manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping.

[0037] A manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping is used for efficient generation of Fe(IV) for targeted thallium removal.

[0038] Principle of the present invention:

[0039] 1. In situ Fe(VI) generation:

[0040] 1. Construct a Co-N4 / MnFe2O4@MnO2 core-shell structure (core: 50nm magnetic MnFe2O4; shell: 20nm mesoporous MnO2), and dope single-atom Co-N4 sites in the MnFe2O4 core to form Co-N4 / MnFe2O4 (Co loading 1.5 wt%; Mn in MnFe2O4 is +2 valence, Fe is +3 valence. Single-atom Co-N4 catalyzes Fe 2+ Regeneration, accelerated electron transfer; Mn 2+ Dissolution quenches free radical byproducts and inhibits SO4 ·- Fe consumption 2+ ;

[0041] ;

[0042] ;

[0043] 2. The oxidants KHSO5 and CaO2 (molar ratio 3:1) are co-encapsulated in the shell mesopores, and the dual oxidants synergistically generate Fe(IV), with the total yield increased to >90%. Neutralization , maintain pH = 5.0 ± 0.3;

[0044] ;

[0045] ;

[0046] ;

[0047] 3. Shell modification: polystyrene sulfonate (PSS) is grafted onto the surface of MnO2 to introduce sulfonic acid groups ( ) Preferentially chelates Ca 2+ (logK=5.2), liberating Tl + Adsorption sites;

[0048] 4. Sealing layer: PDA doped with oxygen vacancy TiO 2-x , the absorption wavelength extends to 600nm, visible light catalysis

[0049] Degradation of humic acid HA;

[0050] 2. Selective thallium removal:

[0051] 1. Selective oxidation of Tl by Fe(IV) + ;

[0052] ;

[0053] 2. MnO2 in-situ lattice fixation of Tl 3+ ;

[0054] ;

[0055] 3. Regeneration cycle: acid dissolution-oxidation repair:

[0056] 1. Oxalic acid pickling regeneration:

[0057] ;

[0058] 2. Shell regeneration:

[0059] .

[0060] Effects of the present invention:

[0061] 1. The Fe(IV) yield of the existing technology is ≤60%, resulting in incomplete oxidation (residual Tl>50μg / L). The present invention uses single-atom Co catalysis to increase the Fe(II) regeneration rate by 5 times (k=3.2×10 4 M -1 s -1 ), efficiently generates Fe(IV) with a yield of >90%; the dual oxidants (KHSO5 / CaO2) work together to increase the oxidation capacity by 120%, and the Tl processing capacity per unit material reaches 580mg / g;

[0062] 2. Traditional methods fail in high hardness / high COD water bodies, with a Tl removal rate of <60%. However, the present invention uses PSS to modify the shell: the sulfonic acid group chelates Ca in the water. 2+ (binding constant logK = 5.2), release Exclusive adsorption site; using TiO 2-x / PDA photocatalytic layer: degrades HA under visible light, COD removal rate>80%, protects active sites, and significantly improves anti-interference performance;

[0063] 3. The traditional method requires precise control of pH, frequent manual intervention, and increased drug consumption costs; the pH of the present invention is self-balanced: Fe 2+ Reacts with KHSO5 to release H + , Fe 2+ Reacts with H2O2 and consumes H + , maintain pH=5.0±0.5; Tl + Concentration trigger: Automatic activation when >5μg / L, no monitoring equipment required; the traditional process requires five steps: "acid adjustment → oxidant addition → reducing agent addition → precipitation → filtration", while the present invention simplifies the process to only two steps: "feeding → magnetic separation", simplifying the operation;

[0064] 4. The energy consumption of the electrochemical method is >5kWh / ton of water, and the cost of the chemical method is >$0.5 / ton of water; however, the present invention consumes zero electricity and does not require external energy; the material is recycled 30 times with a loss rate of <10%, and the processing cost is $0.05 / ton of water, a cost reduction of 90%. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 Schematic diagram of the structure of a manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping prepared in Example 1;

[0066] Figure 2 This is an overall flow chart for removing thallium from a manganese ferrite@manganese dioxide core-shell material doped with single-atom cobalt prepared in Example 1 in Example 2;

[0067] Figure 3 Performance comparison chart. DETAILED DESCRIPTION

[0068] Specific embodiment 1: This embodiment is a preparation method of a manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping, which is specifically completed in the following steps:

[0069] 1. Preparation of ZIF-8@Co:

[0070] ① Dissolve Zn(NO3)2 and Co(NO3)2 in methanol and stir evenly to obtain solution A;

[0071] ② Dissolve 2-methylimidazole in 100 mL of methanol and stir evenly to obtain solution B;

[0072] ③. Mix solution B and solution A evenly, and then stir in a water bath at 25°C for a period of time to obtain reaction product I;

[0073] ④. Centrifuge the reaction product I, wash it, and dry it to obtain ZIF-8@Co;

[0074] 2. Preparation of Co-N4 / MnFe2O4 core:

[0075] ①. Bubble nitrogen into the water to remove oxygen, then dissolve FeCl3 and MnCl2 in oxygen-free water to obtain solution C;

[0076] ②. Add ZIF-8@Co to solution C, disperse under ultrasonication for a period of time, then add NaOH solution dropwise until the pH of the system reaches 12, and heat the reaction for a period of time to obtain reaction product II.

[0077] ③. Filter the reaction product II and then wash the obtained solid matter to obtain a precursor;

[0078] ④. Place the precursor in a tube furnace, pyrolyze it under a nitrogen atmosphere, and cool it to room temperature to obtain the Co-N4 / MnFe2O4 core;

[0079] 3. Preparation of Co-N4 / MnFe2O4@MnO2:

[0080] ① Dissolve hexadecyltrimethylammonium bromide in ultrapure water at 60-70°C, add Co-N4 / MnFe2O4 cores, and sonicate for a period of time to obtain solution D.

[0081] ②. Add KMnO4 solution dropwise to solution D and stir at 70°C for a period of time to obtain reaction product III;

[0082] ③. Centrifuge the reaction product III and wash the resulting solid to obtain Co-N4 / MnFe2O4@MnO2, which is a core-shell intermediate;

[0083] 4. PSS surface modification:

[0084] ① Immerse the core-shell intermediate in an aqueous solution of sodium polystyrene sulfonate, stir at 80°C to 90°C for a period of time, then add a crosslinker solution and continue heating and stirring to crosslink for a period of time to obtain reaction product IV;

[0085] ②, centrifuge the reaction product IV and then wash it to obtain Co-N4 / MnFe2O4@MnO2-PSS;

[0086] 5. Dual oxidant loading and sealing:

[0087] ①. Mix KHSO5 and CaO2, and ball-mill them to a particle size of <5μm to obtain an oxidant mixed powder;

[0088] ② Place Co-N4 / MnFe2O4@MnO2-PSS in a vacuum drying oven, raise the temperature to 50°C under a reduced pressure of -0.1 MPa, spray the oxidant mixed powder onto the Co-N4 / MnFe2O4@MnO2-PSS, and maintain the pressure at -0.1 MPa and 50°C for 2 hours to obtain Co-N4 / MnFe2O4@MnO2-PSS-OX;

[0089] ③ Preparation of TiO 2-x / PDA sealing layer:

[0090] a. Dissolve Ti(OBu)4 in anhydrous ethanol and stir magnetically for a period of time to obtain solution A; dissolve NaBH4 in ultrapure water and dissolve it by ultrasonic for a period of time to obtain solution B; add solution B dropwise to solution A to obtain a blue sol; transfer the blue sol to a polytetrafluoroethylene-lined reactor and perform hydrothermal reaction at 160°C for 10-12 hours to obtain reaction product V; centrifuge reaction product V, wash the obtained solid matter, and vacuum dry to obtain TiO 2-x ;

[0091] b: Dopamine hydrochloride was dissolved in Tris-HCl buffer, and nitrogen was introduced into the solution for a period of time to deoxygenate it to obtain a PDA prepolymer solution; TiO 2-x Dissolve in anhydrous ethanol, add dispersant, and ultrasonicate for a period of time to obtain TiO 2-x dispersion; TiO 2-x The dispersion was added to the PDA prepolymer solution and stirred at 25°C in the dark for a period of time to obtain a gray-blue composite dispersion.

[0092] ④. Immerse Co-N4 / MnFe2O4@MnO2-PSS-OX into the gray-blue composite dispersion, oscillate and deposit for a period of time at 25°C and in the dark, and then oscillate and deposit for a period of time under heating and in the dark to obtain Co-N4 / MnFe2O4@MnO2-PSS-OX@PDA / TiO 2-x , which is a manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping.

[0093] Specific embodiment 2: The difference between this embodiment and specific embodiment 1 is that: the molar ratio of Co(NO3)2 and Zn(NO3)2 described in step 1① is (0.5mmol~1.5mmol):10; the volume ratio of the amount of Co(NO3)2 described in step 1① to methanol is (0.5mmol~1.5mmol):100mL; the volume ratio of the amount of 2-methylimidazole described in step 1② to methanol is (30mmol~50mmol):100mL; the stirring time described in step 1③ is 20h~24h; the volume ratio of solution B to solution A described in step 1③ is 1:1; the centrifugal speed described in step 1④ is 8000rpm~10000rpm, and the centrifugal time is 10 min~15min; the washing described in step 1④ is washing 3~5 times with methanol; the drying temperature described in step 1④ is 40℃~60℃, and the drying time is 4h~6h. Other steps and parameters are the same as specific embodiment 1.

[0094] Specific embodiment three: The difference between this embodiment and specific embodiment one or two is that: the molar ratio of FeCl3 to MnCl2 described in step 2① is 2:1; the volume ratio of the amount of FeCl3 described in step 2① to the oxygen-free water is 20mmol:100mL; the time of ultrasonic dispersion described in step 2② is 30min~60min; the mass ratio of ZIF-8@Co described in step 2② to the oxygen-free water described in step 2① is (1.5g~2.5g):100 mL; the concentration of the NaOH solution in step 2 (2) is 1 mol / L; the heating reaction temperature in step 2 (2) is 70°C-80°C, and the heating reaction time is 5-7 hours; in step 2 (3), reaction product II is filtered, and the resulting solid material is washed 3-5 times with anhydrous ethanol; the pyrolysis process in step 2 (4) is as follows: first, heating from room temperature to 300°C at a heating rate of 2°C / min and holding, then heating from 300°C to 600°C at a heating rate of 5°C / min and holding. Other steps and parameters are the same as those in Specific Embodiments 1 or 2.

[0095] Specific embodiment 4: The difference between this embodiment and specific embodiments 1 to 3 is that: the volume ratio of the amount of hexadecyltrimethylammonium bromide described in step 3 ① to ultrapure water is (2mmol~3mmol): 200mL; the volume ratio of the mass of the Co-N4 / MnFe2O4 core described in step 3 ① to ultrapure water is (1.0g~1.5g): 200mL; the time of ultrasonic dispersion described in step 3 ① is 30min~60min; the concentration of the KMnO4 solution described in step 3 ② is 0.5mol / L; the stirring time at 70°C in step 3 ② is 3h~4h; the speed of dropping the KMnO4 solution in step 3 ② is 2 mL / min; the volume ratio of the KMnO4 solution in step 3② to the ultrapure water in step 3① is 10:100; the centrifugation speed in step 3③ is 10,000 rpm, and the centrifugation time is 5 to 10 minutes; in step 3③, reaction product III is centrifuged, and the resulting solid material is washed 3 to 5 times with ultrapure water; the shell thickness of the core-shell intermediate in step 3③ is 20±2 nm. Other steps and parameters are the same as those in specific embodiments 1 to 3.

[0096] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that: the volume ratio of the core-shell intermediate mass to the aqueous solution of sodium polystyrene sulfonate described in step 4 (1) is 1 g:100 mL; the mass fraction of the aqueous solution of sodium polystyrene sulfonate described in step 4 (1) is 5%, and the Mw of sodium polystyrene sulfonate is 70 kDa; the stirring time at 80°C to 90°C in step 4 (1) is 1 to 2 hours; the crosslinker solution described in step 4 (1) is a mixture of EDC solution and NHS solution, wherein the volume ratio of EDC solution to NHS solution is 1:1, the concentration of EDC solution is 0.1 mol / L, and the concentration of NHS solution is 0.05 mol / L; the volume ratio of the crosslinker solution described in step 4 (1) to the aqueous solution of sodium polystyrene sulfonate is 10:100; and the crosslinking time described in step 4 (1) is 30 to 60 minutes. Other steps and parameters are the same as those of specific embodiments 1 to 4.

[0097] Specific embodiment six: The difference between this embodiment and specific embodiments one to five is that: the centrifugal speed described in step four ② is 10000rpm, and the centrifugal time is 5min~10min; the washing described in step four ② is washing 3 to 5 times with anhydrous ethanol; the molar ratio of CaO2 to KHSO5 described in step five ① is 1:3; the mass ratio of the Co-N4 / MnFe2O4@MnO2-PSS and the oxidant mixed powder described in step five ② is 100:(25~30); the Ti(OBu)4 substance in solution A described in step five ③a is 1: The volume ratio of the amount of NaBH4 in solution B described in step 5 (3a) to ultrapure water is 0.01 mol:50 mL; the volume ratio of solution A to solution B described in step 5 (3a) is 50 mL:20 mL; the dropwise addition rate described in step 5 (3a) is 1 mL / min; the magnetic stirring time described in step 5 (3a) is 20 to 30 minutes; the ultrasonic dissolution time described in step 5 (3a) is 20 to 30 minutes; the centrifugation speed described in step 5 (3a) is 12,000 rpm, and the centrifugation time is 10 to 20 minutes; the solid material obtained in step 5 (3a) is washed alternately with anhydrous ethanol and water, and then vacuum dried at 60 to 70 degrees Celsius for 5 to 7 hours. Other steps and parameters are the same as those in specific embodiments 1 to 5.

[0098] Specific embodiment seven: The differences between this embodiment and specific embodiments one to six are: the volume ratio of the mass of dopamine hydrochloride in the PDA prepolymer solution described in step five ③b to the volume of Tris-HCl buffer is 0.2g:100mL; the concentration of the Tris-HCl buffer is 0.1mol / L, and the pH value is 8.4-8.6; in step five ③b, nitrogen is introduced into the solution for deoxygenation for 10 min-15 min; the TiO 2-x TiO in dispersion 2-x , the mass volume ratio of the dispersant to anhydrous ethanol is 0.1g:0.01g:10mL; the dispersant described in step 5 ③b is disodium EDTA; the TiO 2-x The volume ratio of the dispersion to the PDA prepolymer solution is (8-12):100; in step 5 ③b, TiO 2-x The dispersion was added to the PDA prepolymer solution and stirred at 25° C. in the dark for 20 to 30 minutes to obtain a gray-blue composite dispersion. The other steps and parameters were the same as those in the first to sixth embodiments.

[0099] Specific Embodiment 8: This embodiment differs from Specific Embodiments 1 to 7 in that the volume ratio of the Co-N4 / MnFe2O4@MnO2-PSS-OX mass to the gray-blue composite dispersion in step 5 (4) is 1 g:50 mL. In step 5 (4), the Co-N4 / MnFe2O4@MnO2-PSS-OX is immersed in the gray-blue composite dispersion and subjected to oscillation deposition at 25°C, protected from light, and a rotation speed of 150 rpm for 4 hours, followed by oscillation deposition at 40°C, protected from light, and a rotation speed of 150 rpm for 2 to 3 hours. Other steps and parameters are the same as for Specific Embodiments 1 to 7.

[0100] Specific embodiment nine: This embodiment is a manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping for efficient generation of Fe(IV) and targeted removal of thallium.

[0101] Specific embodiment 10: The difference between this embodiment and specific embodiments 1 to 9 is that a manganese ferrite @ manganese dioxide core-shell material based on single-atom cobalt doping is used to efficiently generate Fe(IV) and target thallium removal, which is specifically completed in the following steps:

[0102] The manganese ferrite @ manganese dioxide core-shell material based on single-atom cobalt doping is added to the thallium-containing water body and reacted for 15min~20min, and then the manganese ferrite @ manganese dioxide core-shell material based on single-atom cobalt doping is magnetically separated and recovered to obtain treated water; the manganese ferrite @ manganese dioxide core-shell material based on single-atom cobalt doping is then regenerated; the addition amount of the manganese ferrite @ manganese dioxide core-shell material based on single-atom cobalt doping is 0.05 g / L~0.1 g / L; Tl in the thallium-containing water body is 0.05 g / L~0.1 g / L; + The concentration is 5μg~100μg / L; the regeneration method is: first use a 2+ The manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping was cleaned 2 to 4 times with the pickling solution to desorb thallium, and then immersed in a KMnO4 solution with a concentration of 0.05 mol / L to repair it; the Co-containing 2+ The concentration of H2C2O4 in the pickling solution is 0.1mol / L, the concentration of HCl is 0.05mol / L, and the concentration of Co 2+ The concentration of is 0.01 mol / L. Other steps and parameters are the same as those in the first to ninth embodiments.

[0103] The following examples are used to verify the beneficial effects of the present invention:

[0104] Example 1: A method for preparing a manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping is specifically completed by the following steps:

[0105] 1. Preparation of ZIF-8@Co:

[0106] ① Dissolve 10 mmol Zn(NO3)2 and 1 mmol Co(NO3)2 in 100 mL methanol and stir evenly to obtain solution A;

[0107] ② Dissolve 40 mmol of 2-methylimidazole in 100 mL of methanol and stir evenly to obtain solution B;

[0108] ③. Mix solution B and solution A evenly, and then stir in a water bath at 25°C for 24 hours to obtain reaction product I;

[0109] The volume ratio of solution B to solution A described in step 1 (3) is 1:1;

[0110] ④. The reaction product I was centrifuged, washed with methanol three times, and dried to obtain ZIF-8@Co;

[0111] The centrifugal speed in step 1 (4) is 8000 rpm and the centrifugal time is 10 min;

[0112] The drying temperature in step 1 (4) is 60°C and the drying time is 5 hours;

[0113] 2. Preparation of Co-N4 / MnFe2O4 core:

[0114] ①. Bubble nitrogen into the water to remove oxygen, then dissolve 20 mmol FeCl3 and 10 mmol MnCl2 in 100 mL of oxygen-free water to obtain solution C.

[0115] ② Add 2 g of ZIF-8@Co to solution C, ultrasonically disperse for 30 min, then add NaOH solution dropwise until the pH of the system reaches 12. Then, heat the mixture at 80°C for 6 h to obtain reaction product II.

[0116] The concentration of the NaOH solution described in step 2② is 1 mol / L;

[0117] ③. Filter the reaction product II, and then wash the obtained solid material with anhydrous ethanol three times to obtain a precursor;

[0118] ④. The precursor was placed in a tube furnace, pyrolyzed under a nitrogen atmosphere, and cooled to room temperature to obtain Co-N4 / MnFe2O4 cores (single-atom Co-N4 doped MnFe2O4 nanospheres with a particle size of 50±5nm);

[0119] The pyrolysis process described in step 2 (4) is as follows: first, heating from room temperature to 300°C at a heating rate of 2°C / min and holding for 1 hour, then heating from 300°C to 600°C at a heating rate of 5°C / min and holding for 2 hours;

[0120] 3. Preparation of Co-N4 / MnFe2O4@MnO2:

[0121] ① Dissolve 2.5 mmol of hexadecyltrimethylammonium bromide in 200 mL of ultrapure water at 60°C, then add 1.0 g of Co-N4 / MnFe2O4 cores and sonicate for 30 min to obtain solution D;

[0122] ②. Add 20 mL of KMnO4 solution dropwise to solution D and stir at 70°C for 3 h to obtain reaction product III.

[0123] The concentration of the KMnO4 solution described in step 3② is 0.5 mol / L;

[0124] In step 3②, the rate of adding KMnO4 solution is 2 mL / min;

[0125] ③. Centrifuge the reaction product III, and then wash the resulting solid material three times with ultrapure water to obtain Co-N4 / MnFe2O4@MnO2, which is a core-shell intermediate;

[0126] The centrifugal speed in step 3 (3) is 10,000 rpm and the centrifugal time is 5 min;

[0127] The shell thickness of the core-shell intermediate in step 3 (3) is 20±2 nm;

[0128] 4. PSS surface modification:

[0129] ① Immerse 1 g of the core-shell intermediate in 100 mL of an aqueous solution of sodium polystyrene sulfonate, stir at 80°C for 1 hour, then add 10 mL of a crosslinker solution and continue heating and stirring for 30 minutes to obtain reaction product IV;

[0130] The mass fraction of the aqueous solution of sodium polystyrene sulfonate described in step 4① is 5%, and the Mw of sodium polystyrene sulfonate is 70 kDa;

[0131] The cross-linking agent solution described in step 4 (1) is a mixture of EDC solution and NHS solution, wherein the volume ratio of EDC solution to NHS solution is 1:1, the concentration of EDC solution is 0.1 mol / L, and the concentration of NHS solution is 0.05 mol / L;

[0132] ②, centrifuge the reaction product IV and wash it with anhydrous ethanol three times to obtain Co-N4 / MnFe2O4@MnO2-PSS;

[0133] The centrifugal speed in step 4 (2) is 10,000 rpm and the centrifugal time is 5 min;

[0134] The MnO2-PSS in the MnFe2O4@MnO2-PSS described in step 4② is PSS-modified MnO2 nanosheets with a thickness of 20±2 nm and a pore size of 5 nm;

[0135] 5. Dual oxidant loading and sealing:

[0136] ①. Mix KHSO5 and CaO2, and ball-mill them to a particle size of <5μm to obtain an oxidant mixed powder;

[0137] The molar ratio of CaO2 to KHSO5 described in step 5① is 1:3;

[0138] ② Place Co-N4 / MnFe2O4@MnO2-PSS in a vacuum drying oven, raise the temperature to 50°C under a reduced pressure of -0.1 MPa, spray the oxidant mixed powder onto the Co-N4 / MnFe2O4@MnO2-PSS, and maintain the pressure at -0.1 MPa and 50°C for 2 hours to obtain Co-N4 / MnFe2O4@MnO2-PSS-OX;

[0139] The mass ratio of the Co-N4 / MnFe2O4@MnO2-PSS and oxidant mixed powders described in step 5① is 100:28;

[0140] ③ Preparation of TiO 2-x / PDA sealing layer:

[0141] a: 0.01 mol Ti(OBu)4 was dissolved in 50 mL of anhydrous ethanol and magnetically stirred for 30 min to obtain solution A; 0.02 mol NaBH4 was dissolved in 20 mL of ultrapure water and ultrasonically dissolved for 20 min to obtain solution B; solution B was added dropwise to solution A to obtain a blue sol; the blue sol was transferred to a polytetrafluoroethylene-lined reactor and hydrothermally reacted at 160°C for 12 h to obtain reaction product V; reaction product V was centrifuged, the obtained solid matter was washed, and vacuum dried to obtain TiO 2-x ;

[0142] The rate of addition in step 5 ③a is 1 mL / min;

[0143] The centrifugal speed in step 5 (3)a is 12000 rpm and the centrifugal time is 10 min;

[0144] Step 5 ③a: wash the solid material obtained with anhydrous ethanol and water alternately for 2 times, and then vacuum dry at 60°C for 6 hours;

[0145] b: 0.2 g dopamine hydrochloride was dissolved in 100 mL Tris-HCl buffer, and nitrogen was introduced into the solution for deoxygenation for 15 min to obtain PDA prepolymer solution; 0.1 g TiO 2-x Dissolve in 10 mL of anhydrous ethanol, add 0.01 g of dispersant, and ultrasonicate for 30 min to obtain TiO 2-x dispersion; TiO 2-x The dispersion was added to the PDA prepolymer solution and stirred at 25°C in the dark for 30 min to obtain a gray-blue composite dispersion.

[0146] The concentration of the Tris-HCl buffer described in step 5 (3)b is 0.1 mol / L and the pH value is 8.5;

[0147] The dispersant described in step 5 ③b is disodium EDTA;

[0148] ④. Immerse Co-N4 / MnFe2O4@MnO2-PSS-OX into the gray-blue composite dispersion and oscillate and deposit at 25°C, protected from light, and a rotation speed of 150 rpm for 4 h. Then oscillate and deposit at 40°C, protected from light, and a rotation speed of 150 rpm for 2 h to obtain Co-N4 / MnFe2O4@MnO2-PSS-OX@PDA / TiO 2-x , that is, manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping;

[0149] The volume ratio of the mass of Co-N4 / MnFe2O4@MnO2-PSS-OX described in step 5④ to the gray-blue composite dispersion is 1g:50mL;

[0150] Co-N4 / MnFe2O4@MnO2-PSS-OX@PDA / TiO described in step 5④ 2-x The middle sealing layer is TiO 2-x / PDA film, thickness <5nm.

[0151] Comparative Example 1: Preparation of Co-N4-undoped manganese ferrite@manganese dioxide core-shell material, specifically completed by the following steps:

[0152] 1. Preparation of MnFe2O4 core:

[0153] ①. Bubble nitrogen into the water to remove oxygen, then dissolve 20 mmol FeCl3 and 10 mmol MnCl2 in 100 mL of oxygen-free water to obtain solution C.

[0154] ②. NaOH solution was added dropwise to solution C until the pH of the system reached 12, and then heated at 80°C for 6 h to obtain reaction product II.

[0155] The concentration of the NaOH solution described in step 1② is 1 mol / L;

[0156] ③. Filter the reaction product II', and then wash the obtained solid material with anhydrous ethanol three times to obtain a precursor;

[0157] ④. The precursor was placed in a tube furnace, pyrolyzed under a nitrogen atmosphere, and cooled to room temperature to obtain MnFe2O4 cores (MnFe2O4 nanospheres with a particle size of 50±5 nm);

[0158] The pyrolysis process described in step 1 (4) is as follows: first, heating from room temperature to 300°C at a heating rate of 2°C / min and holding for 1 hour, then heating from 300°C to 600°C at a heating rate of 5°C / min and holding for 2 hours; 2. Preparation of MnFe2O4@MnO2:

[0159] ① Dissolve 2.5 mmol of hexadecyltrimethylammonium bromide in 200 mL of ultrapure water at 60°C, then add 1.0 g of MnFe2O4 cores (MnFe2O4 nanospheres, particle size 50 ± 5 nm), and sonicate for 30 min to obtain solution D.

[0160] ②. Add 20 mL of KMnO4 solution dropwise to solution D and stir at 70°C for 3 h to obtain reaction product III.

[0161] The concentration of the KMnO4 solution described in step 2② is 0.5 mol / L;

[0162] In step 2②, the rate of adding KMnO4 solution is 2 mL / min;

[0163] ③. Centrifuge the reaction product III, and then wash the resulting solid material three times with ultrapure water to obtain MnFe2O4@MnO2, which is the core-shell intermediate;

[0164] The centrifugal speed in step 2 (3) is 10,000 rpm and the centrifugal time is 5 min;

[0165] The shell thickness of the core-shell intermediate in step 2 (3) is 20 ± 2 nm;

[0166] 3. PSS surface modification:

[0167] ① Immerse 1 g of the core-shell intermediate in 100 mL of an aqueous solution of sodium polystyrene sulfonate, stir at 80°C for 1 hour, then add 10 mL of a crosslinker solution and continue heating and stirring for 30 minutes to obtain reaction product IV;

[0168] The mass fraction of the aqueous solution of sodium polystyrene sulfonate described in step 3① is 5%, and the Mw of sodium polystyrene sulfonate is 70 kDa;

[0169] The cross-linking agent solution described in step 3① is a mixture of EDC solution and NHS solution, wherein the volume ratio of EDC solution to NHS solution is 1:1, the concentration of EDC solution is 0.1 mol / L, and the concentration of NHS solution is 0.05 mol / L;

[0170] ②, centrifuge the reaction product IV, and then wash it with anhydrous ethanol three times to obtain MnFe2O4@MnO2-PSS;

[0171] The centrifugal speed in step 3② is 10000 rpm and the centrifugal time is 5 min;

[0172] The MnO2-PSS in the MnFe2O4@MnO2-PSS described in step 3② is PSS-modified MnO2 nanosheets with a thickness of 20±2 nm and a pore size of 5 nm;

[0173] 4. Dual Oxidant Loading and Sealing:

[0174] ①. Mix KHSO5 and CaO2, and ball-mill them to a particle size of <5μm to obtain an oxidant mixed powder;

[0175] The molar ratio of CaO2 to KHSO5 described in step 4① is 1:3;

[0176] ② Place MnFe2O4@MnO2-PSS in a vacuum drying oven, raise the temperature to 50°C under a reduced pressure of -0.1 MPa, spray the oxidant mixed powder onto the MnFe2O4@MnO2-PSS, and maintain the pressure at -0.1 MPa and 50°C for 2 hours to obtain MnFe2O4@MnO2-PSS-OX;

[0177] The mass ratio of the MnFe2O4@MnO2-PSS and oxidant mixed powders described in step 4① is 100:28;

[0178] ③ Preparation of TiO 2-x / PDA sealing layer:

[0179] a: 0.01 mol Ti(OBu)4 was dissolved in 50 mL of anhydrous ethanol and magnetically stirred for 30 min to obtain solution A; 0.02 mol NaBH4 was dissolved in 20 mL of ultrapure water and ultrasonically dissolved for 20 min to obtain solution B; solution B was added dropwise to solution A to obtain a blue sol; the blue sol was transferred to a polytetrafluoroethylene-lined reactor and hydrothermally reacted at 160°C for 12 h to obtain reaction product V; reaction product V was centrifuged, the obtained solid matter was washed, and vacuum dried to obtain TiO 2-x ;

[0180] The rate of addition in step 4 ③a is 1 mL / min;

[0181] The centrifugal speed in step 4 (3)a is 12000 rpm and the centrifugal time is 10 min;

[0182] In step 4 (3)a, the solid material obtained was washed alternately with anhydrous ethanol and water, each washed twice, and then vacuum-dried at 60°C for 6 hours;

[0183] b: 0.2 g dopamine hydrochloride was dissolved in 100 mL Tris-HCl buffer, and nitrogen was introduced into the solution for deoxygenation for 15 min to obtain PDA prepolymer solution; 0.1 g TiO 2-x Dissolve in 10 mL of anhydrous ethanol, add 0.01 g of dispersant, and ultrasonicate for 30 min to obtain TiO 2-x dispersion; TiO 2-x The dispersion was added to the PDA prepolymer solution and stirred at 25°C in the dark for 30 min to obtain a gray-blue composite dispersion.

[0184] The concentration of the Tris-HCl buffer described in step 4 (3)b is 0.1 mol / L and the pH value is 8.5;

[0185] The dispersant in step 4 ③b is disodium EDTA;

[0186] ④. Immerse MnFe2O4@MnO2-PSS in the gray-blue composite dispersion and oscillate and deposit at 25°C, protected from light, and a rotation speed of 150 rpm for 4 h. Then oscillate and deposit at 40°C, protected from light, and a rotation speed of 150 rpm for 2 h to obtain MnFe2O4@MnO2-PSS-OX@PDA / TiO 2-x , that is, manganese ferrite@manganese dioxide core-shell material without Co-N4 doping;

[0187] The volume ratio of the mass of MnFe2O4@MnO2-PSS described in step 4 (4) to the gray-blue composite dispersion is 1 g:50 mL;

[0188] MnFe2O4@MnO2-PSS-OX@PDA / TiO described in step 4④ 2-x The middle sealing layer is TiO 2-x / PDA film, thickness <5nm.

[0189] Comparative Example 2: A method for preparing a manganese ferrite@manganese dioxide core-shell material whose surface is not modified with PSS is specifically completed by the following steps:

[0190] 1. Preparation of ZIF-8@Co:

[0191] ① Dissolve 10 mmol Zn(NO3)2 and 1 mmol Co(NO3)2 in 100 mL methanol and stir evenly to obtain solution A;

[0192] ② Dissolve 40 mmol of 2-methylimidazole in 100 mL of methanol and stir evenly to obtain solution B;

[0193] ③. Mix solution B and solution A evenly, and then stir in a water bath at 25°C for 24 hours to obtain reaction product I;

[0194] The volume ratio of solution B to solution A described in step 1 (3) is 1:1;

[0195] ④. The reaction product I was centrifuged, washed with methanol three times, and dried to obtain ZIF-8@Co;

[0196] The centrifugal speed in step 1 (4) is 8000 rpm and the centrifugal time is 10 min;

[0197] The drying temperature in step 1 (4) is 60°C and the drying time is 5 hours;

[0198] 2. Preparation of Co-N4 / MnFe2O4 core:

[0199] ①. Bubble nitrogen into the water to remove oxygen, then dissolve 20 mmol FeCl3 and 10 mmol MnCl2 in 100 mL of oxygen-free water to obtain solution C.

[0200] ② Add 2 g of ZIF-8@Co to solution C, ultrasonically disperse for 30 min, then add NaOH solution dropwise until the pH of the system reaches 12. Then, heat the mixture at 80°C for 6 h to obtain reaction product II.

[0201] The concentration of the NaOH solution described in step 2② is 1 mol / L;

[0202] ③. Filter the reaction product II, and then wash the obtained solid material with anhydrous ethanol three times to obtain a precursor;

[0203] ④. The precursor was placed in a tube furnace, pyrolyzed under a nitrogen atmosphere, and cooled to room temperature to obtain Co-N4 / MnFe2O4 cores (single-atom Co-N4 doped MnFe2O4 nanospheres with a particle size of 50±5nm);

[0204] The pyrolysis process described in step 2 (4) is as follows: first, heating from room temperature to 300°C at a heating rate of 2°C / min and holding for 1 hour, then heating from 300°C to 600°C at a heating rate of 5°C / min and holding for 2 hours;

[0205] 3. Preparation of Co-N4 / MnFe2O4@MnO2:

[0206] ① Dissolve 2.5 mmol of hexadecyltrimethylammonium bromide in 200 mL of ultrapure water at 60°C, then add 1.0 g of Co-N4 / MnFe2O4 cores and sonicate for 30 min to obtain solution D;

[0207] ②. Add 20 mL of KMnO4 solution dropwise to solution D and stir at 70°C for 3 h to obtain reaction product III.

[0208] The concentration of the KMnO4 solution described in step 3② is 0.5 mol / L;

[0209] In step 3②, the rate of adding KMnO4 solution is 2 mL / min;

[0210] ③. Centrifuge the reaction product III, and then wash the resulting solid material three times with ultrapure water to obtain Co-N4 / MnFe2O4@MnO2, which is a core-shell intermediate;

[0211] The centrifugal speed in step 3 (3) is 10,000 rpm and the centrifugal time is 5 min;

[0212] The shell thickness of the core-shell intermediate in step 3 (3) is 20±2 nm;

[0213] 4. Dual Oxidant Loading and Sealing:

[0214] ①. Mix KHSO5 and CaO2, and ball-mill them to a particle size of <5μm to obtain an oxidant mixed powder;

[0215] The molar ratio of CaO2 to KHSO5 described in step 4① is 1:3;

[0216] ② Place Co-N4 / MnFe2O4@MnO2 in a vacuum drying oven, raise the temperature to 50°C under a reduced pressure of -0.1 MPa, spray the oxidant mixed powder onto Co-N4 / MnFe2O4@MnO2, and maintain the pressure at -0.1 MPa and 50°C for 2 hours to obtain Co-N4 / MnFe2O4@MnO2-OX;

[0217] The mass ratio of the Co-N4 / MnFe2O4@MnO2 and oxidant mixed powders described in step 4① is 100:28;

[0218] ③ Preparation of TiO 2-x / PDA sealing layer:

[0219] a: 0.01 mol Ti(OBu)4 was dissolved in 50 mL of anhydrous ethanol and magnetically stirred for 30 min to obtain solution A; 0.02 mol NaBH4 was dissolved in 20 mL of ultrapure water and ultrasonically dissolved for 20 min to obtain solution B; solution B was added dropwise to solution A to obtain a blue sol; the blue sol was transferred to a polytetrafluoroethylene-lined reactor and hydrothermally reacted at 160°C for 12 h to obtain reaction product V; reaction product V was centrifuged, the obtained solid matter was washed, and vacuum dried to obtain TiO 2-x ;

[0220] The rate of addition in step 4 ③a is 1 mL / min;

[0221] The centrifugal speed in step 4 (3)a is 12000 rpm and the centrifugal time is 10 min;

[0222] In step 4 (3)a, the solid material obtained was washed alternately with anhydrous ethanol and water, each washed twice, and then vacuum-dried at 60°C for 6 hours;

[0223] b: 0.2 g dopamine hydrochloride was dissolved in 100 mL Tris-HCl buffer, and nitrogen was introduced into the solution for deoxygenation for 15 min to obtain PDA prepolymer solution; 0.1 g TiO 2-x Dissolve in 10 mL of anhydrous ethanol, add 0.01 g of dispersant, and ultrasonicate for 30 min to obtain TiO 2-x dispersion; TiO 2-x The dispersion was added to the PDA prepolymer solution and stirred at 25°C in the dark for 30 min to obtain a gray-blue composite dispersion.

[0224] The concentration of the Tris-HCl buffer described in step 4 (3)b is 0.1 mol / L and the pH value is 8.5;

[0225] The dispersant in step 4 ③b is disodium EDTA;

[0226] ④. Immerse Co-N4 / MnFe2O4@MnO2 in the gray-blue composite dispersion and oscillate and deposit at 25°C, protected from light, and a rotation speed of 150 rpm for 4 h. Then oscillate and deposit at 40°C, protected from light, and a rotation speed of 150 rpm for 2 h to obtain Co-N4 / MnFe2O4@MnO2-OX@PDA / TiO 2-x , that is, the manganese ferrite@manganese dioxide core-shell material whose surface is not modified by PSS;

[0227] The volume ratio of the mass of MnFe2O4@MnO2 to the gray-blue composite dispersion described in step 4 (4) is 1g:50mL;

[0228] Co-N4 / MnFe2O4@MnO2-OX@PDA / TiO described in step 4④ 2-x The middle sealing layer is TiO 2-x / PDA film, thickness <5nm.

[0229] Comparative Example 3: PDA sealing layer without oxygen vacancy doped TiO 2-x The preparation method of the manganese ferrite@manganese dioxide core-shell material is specifically completed by the following steps:

[0230] 1. Preparation of ZIF-8@Co:

[0231] ① Dissolve 10 mmol Zn(NO3)2 and 1 mmol Co(NO3)2 in 100 mL methanol and stir evenly to obtain solution A;

[0232] ② Dissolve 40 mmol of 2-methylimidazole in 100 mL of methanol and stir evenly to obtain solution B;

[0233] ③. Mix solution B and solution A evenly, and then stir in a water bath at 25°C for 24 hours to obtain reaction product I;

[0234] The volume ratio of solution B to solution A described in step 1 (3) is 1:1;

[0235] ④. The reaction product I was centrifuged, washed with methanol three times, and dried to obtain ZIF-8@Co;

[0236] The centrifugal speed in step 1 (4) is 8000 rpm and the centrifugal time is 10 min;

[0237] The drying temperature in step 1 (4) is 60°C and the drying time is 5 hours;

[0238] 2. Preparation of Co-N4 / MnFe2O4 core:

[0239] ①. Bubble nitrogen into the water to remove oxygen, then dissolve 20 mmol FeCl3 and 10 mmol MnCl2 in 100 mL of oxygen-free water to obtain solution C.

[0240] ② Add 2 g of ZIF-8@Co to solution C, ultrasonically disperse for 30 min, then add NaOH solution dropwise until the pH of the system reaches 12. Then, heat the mixture at 80°C for 6 h to obtain reaction product II.

[0241] The concentration of the NaOH solution described in step 2② is 1 mol / L;

[0242] ③. Filter the reaction product II, and then wash the obtained solid material with anhydrous ethanol three times to obtain a precursor;

[0243] ④. The precursor was placed in a tube furnace, pyrolyzed under a nitrogen atmosphere, and cooled to room temperature to obtain Co-N4 / MnFe2O4 cores (single-atom Co-N4 doped MnFe2O4 nanospheres with a particle size of 50±5nm);

[0244] The pyrolysis process described in step 2 (4) is as follows: first, heating from room temperature to 300°C at a heating rate of 2°C / min and holding for 1 hour, then heating from 300°C to 600°C at a heating rate of 5°C / min and holding for 2 hours;

[0245] 3. Preparation of Co-N4 / MnFe2O4@MnO2:

[0246] ① Dissolve 2.5 mmol of hexadecyltrimethylammonium bromide in 200 mL of ultrapure water at 60°C, then add 1.0 g of Co-N4 / MnFe2O4 cores and sonicate for 30 min to obtain solution D;

[0247] ②. Add 20 mL of KMnO4 solution dropwise to solution D and stir at 70°C for 3 h to obtain reaction product III.

[0248] The concentration of the KMnO4 solution described in step 3② is 0.5 mol / L;

[0249] In step 3②, the rate of adding KMnO4 solution is 2 mL / min;

[0250] ③. Centrifuge the reaction product III, and then wash the resulting solid material three times with ultrapure water to obtain Co-N4 / MnFe2O4@MnO2, which is a core-shell intermediate;

[0251] The centrifugal speed in step 3 (3) is 10,000 rpm and the centrifugal time is 5 min;

[0252] The shell thickness of the core-shell intermediate in step 3 (3) is 20±2 nm;

[0253] 4. PSS surface modification:

[0254] ① Immerse 1 g of the core-shell intermediate in 100 mL of an aqueous solution of sodium polystyrene sulfonate, stir at 80°C for 1 hour, then add 10 mL of a crosslinker solution and continue heating and stirring for 30 minutes to obtain reaction product IV;

[0255] The mass fraction of the aqueous solution of sodium polystyrene sulfonate described in step 4① is 5%, and the Mw of sodium polystyrene sulfonate is 70 kDa;

[0256] The cross-linking agent solution described in step 4 (1) is a mixture of EDC solution and NHS solution, wherein the volume ratio of EDC solution to NHS solution is 1:1, the concentration of EDC solution is 0.1 mol / L, and the concentration of NHS solution is 0.05 mol / L;

[0257] ②, centrifuge the reaction product IV and wash it with anhydrous ethanol three times to obtain Co-N4 / MnFe2O4@MnO2-PSS;

[0258] The centrifugal speed in step 4 (2) is 10,000 rpm and the centrifugal time is 5 min;

[0259] The MnO2-PSS in the MnFe2O4@MnO2-PSS described in step 4② is PSS-modified MnO2 nanosheets with a thickness of 20±2 nm and a pore size of 5 nm;

[0260] 5. Dual oxidant loading and sealing:

[0261] ①. Mix KHSO5 and CaO2, and ball-mill them to a particle size of <5μm to obtain an oxidant mixed powder;

[0262] The molar ratio of CaO2 to KHSO5 described in step 5① is 1:3;

[0263] ② Place Co-N4 / MnFe2O4@MnO2-PSS in a vacuum drying oven, raise the temperature to 50°C under a reduced pressure of -0.1 MPa, spray the oxidant mixed powder onto the Co-N4 / MnFe2O4@MnO2-PSS, and maintain the pressure at -0.1 MPa and 50°C for 2 hours to obtain Co-N4 / MnFe2O4@MnO2-PSS-OX;

[0264] The mass ratio of the Co-N4 / MnFe2O4@MnO2-PSS and oxidant mixed powders described in step 5① is 100:28;

[0265] ③. Making PDA sealing layer:

[0266] 0.2 g of dopamine hydrochloride was dissolved in 100 mL of Tris-HCl buffer, and nitrogen was introduced into the solution for deoxygenation for 15 min to obtain a PDA prepolymer solution;

[0267] The concentration of the Tris-HCl buffer described in step 5 (3) is 0.1 mol / L and the pH value is 8.5;

[0268] ④. Immerse Co-N4 / MnFe2O4@MnO2-PSS-OX into PDA prepolymer solution, oscillate and deposit at 25°C, dark and 150 rpm for 4 h, then oscillate and deposit at 40°C, dark and 150 rpm for 2 h to obtain Co-N4 / MnFe2O4@MnO2-PSS-OX@PDA, which is the PDA sealing layer without oxygen vacancy TiO 2-x Manganese ferrite@manganese dioxide core-shell material;

[0269] The volume ratio of the mass of Co-N4 / MnFe2O4@MnO2-PSS-OX described in step 5④ to the gray-blue composite dispersion is 1g:50mL;

[0270] Co-N4 / MnFe2O4@MnO2-PSS-OX@PDA described in step 5④ The middle sealing layer is a PDA film with a thickness of less than 5nm.

[0271] Application Example 1: A manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping prepared in Example 1 is used to efficiently generate Fe(IV) for targeted thallium removal, which is specifically accomplished by the following steps:

[0272] The manganese ferrite @ manganese dioxide core-shell material based on single-atom cobalt doping prepared in Example 1 was added to the thallium-containing water body and reacted for 15 minutes, and then the manganese ferrite @ manganese dioxide core-shell material based on single-atom cobalt doping was recovered by magnetic separation to obtain treated water; the manganese ferrite @ manganese dioxide core-shell material based on single-atom cobalt doping was then regenerated; the addition amount of the manganese ferrite @ manganese dioxide core-shell material based on single-atom cobalt doping was 0.1 g / L; Tl in the thallium-containing water body was 0.1 g / L; + The concentration is 0.1 mg / L; the regeneration method is: first use a 2+ The single-atom cobalt-doped manganese ferrite@manganese dioxide core-shell material was cleaned three times with an acid wash solution to desorb thallium, and then immersed in a 0.05 mol / L KMnO4 solution for 15 to 30 min to repair it; the Co-containing 2+ The concentration of H2C2O4 in the pickling solution is 0.1mol / L, the concentration of HCl is 0.05mol / L, and the concentration of Co 2+ The concentration is 0.01mol / L;

[0273] According to the same process as above, the manganese ferrite @ manganese dioxide core-shell material based on single-atom cobalt doping prepared in Example 1 was replaced by the manganese ferrite @ manganese dioxide core-shell material without Co-N4 doping prepared in Comparative Example 1, and the other steps and parameters remained unchanged;

[0274] The yield of Fe(IV) when the manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping prepared in Example 1 and the manganese ferrite@manganese dioxide core-shell material without Co-N4 doping prepared in Comparative Example 1 were activated is shown in FIG. Figure 3 As shown in the two bar graphs 1 and 2 in the middle left part;

[0275] from Figure 3 The two bar graphs 1 and 2 on the left side show that the Fe(IV) yield of the activated manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping prepared in Example 1 is 92.5%; the Fe(IV) yield of the activated manganese ferrite@manganese dioxide core-shell material without Co-N4 doping prepared in Comparative Example 1 is 54.2% (<60%). The PMSO probe method was used to verify the Fe(IV) production. 10μM PMSO (methyl phenyl sulfoxide) was added and the product was detected. (methyl phenyl sulfone), and the Fe(IV) concentration was quantified by HPLC-MS (liquid chromatography-mass spectrometry).

[0276] The removal rate of Tl by the manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping prepared in Example 1 was 99.99%. The removal rate of Tl by the manganese ferrite@manganese dioxide core-shell material without Co-N4 doping prepared in Comparative Example 1 was 82.3% (↓17.69%, due to the lack of Co-N4 sites, the Fe(IV) yield was significantly reduced, resulting in its limited oxidation ability for Tl⁺).

[0277] Application Example 2: A manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping prepared in Example 1 is used to efficiently generate Fe(IV) for targeted thallium removal, which is specifically accomplished by the following steps:

[0278] The manganese ferrite @ manganese dioxide core-shell material based on single-atom cobalt doping prepared in Example 1 was added to a thallium-containing water body (high hardness water) and reacted for 15 minutes, followed by magnetic separation to recover the manganese ferrite @ manganese dioxide core-shell material based on single-atom cobalt doping to obtain treated water; the manganese ferrite @ manganese dioxide core-shell material based on single-atom cobalt doping was then regenerated; the addition amount of the manganese ferrite @ manganese dioxide core-shell material based on single-atom cobalt doping was 0.1 g / L; Tl in the thallium-containing water body was 0.1 g / L. + The concentration is 0.1 mg / L, Ca 2+ The concentration is 1000 mg / L; the regeneration method is: first use a 2+ The single-atom cobalt-doped manganese ferrite@manganese dioxide core-shell material was cleaned three times with an acid wash solution to desorb thallium, and then immersed in a 0.05 mol / L KMnO4 solution for 15 to 30 minutes to repair it; the Co-containing 2+The concentration of H2C2O4 in the pickling solution is 0.1mol / L, the concentration of HCl is 0.05mol / L, and the concentration of Co 2+ The concentration is 0.01mol / L;

[0279] According to the same process as above, the manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping prepared in Example 1 was replaced with the manganese ferrite@manganese dioxide core-shell material whose surface was not modified with PSS prepared in Comparative Example 2, and the other steps and parameters remained unchanged;

[0280] At 1000 mg / L Ca 2+ Under the interference, the manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping prepared in Example 1 and the manganese ferrite@manganese dioxide core-shell material without PSS modification prepared in Comparative Example 2 were used to remove Tl. The removal rate of Tl was shown in FIG. Figure 3 As shown in the two bar graphs 3 and 4 in the middle part;

[0281] from Figure 3 From the two bar graphs 3 and 4 in the middle part, we can see that the removal rate of Tl by the manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping prepared in Example 1 is 99.2%. The removal rate of Tl by the manganese ferrite@manganese dioxide core-shell material without PSS modification prepared in Example 2 is 67.9% (↓31.3%, in the presence of Ca 2+ interference).

[0282] Application Example 3: A manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping prepared in Example 1 is used to efficiently generate Fe(IV) for targeted thallium removal, which is specifically accomplished by the following steps:

[0283] The manganese ferrite @ manganese dioxide core-shell material based on single-atom cobalt doping prepared in Example 1 was added to a thallium-containing water body (containing humic acid water), and then the manganese ferrite @ manganese dioxide core-shell material based on single-atom cobalt doping was magnetically separated and recovered to obtain treated water; the manganese ferrite @ manganese dioxide core-shell material based on single-atom cobalt doping was then regenerated; the addition amount of the manganese ferrite @ manganese dioxide core-shell material based on single-atom cobalt doping was 0.1 g / L; Tl in the thallium-containing water body was 0.1 g / L. + The concentration is 0.1 mg / L, the concentration of humic acid is 50 mg / L; the regeneration method is: first use a mixture containing Co 2+ The single-atom cobalt-doped manganese ferrite@manganese dioxide core-shell material was cleaned three times with an acid wash solution to desorb thallium, and then immersed in a 0.05 mol / L KMnO4 solution for 15 to 30 minutes to repair it; the Co-containing 2+The concentration of H2C2O4 in the pickling solution is 0.1mol / L, the concentration of HCl is 0.05mol / L, and the concentration of Co 2+ The concentration is 0.01mol / L;

[0284] According to the same process as above, the manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping prepared in Example 1 was replaced with the PDA sealing layer undoped with oxygen vacancy TiO prepared in Comparative Example 3. 2-x The manganese ferrite@manganese dioxide core-shell material, other steps and parameters remain unchanged;

[0285] Under the interference of 50 mg / L humic acid, the manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping prepared in Example 1 and the PDA sealing layer undoped with oxygen vacancy TiO prepared in Comparative Example 3 were used. 2-x The removal rate of Tl by manganese ferrite@manganese dioxide core-shell material is shown in Figure 3 As shown in the two bar graphs 5 and 6 in the middle right part;

[0286] from Figure 3 The two bar graphs 5 and 6 on the right side show that the removal rate of Tl by the manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping prepared in Example 1 is 98.3%; the PDA sealing layer prepared in Comparative Example 3 is not doped with oxygen vacancy TiO 2-x The removal efficiency of Tl by the manganese ferrite@manganese dioxide core-shell material was 80.49% (↓17.9%, due to the interference of HA).

Claims

1. A method for preparing a manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping, characterized in that The preparation method is specifically completed according to the following steps:

1. Preparation of ZIF-8@Co: ① Dissolve Zn(NO3)2 and Co(NO3)2 in methanol and stir evenly to obtain solution A; ② Dissolve 2-methylimidazole in methanol and stir evenly to obtain solution B; ③. Mix solution B and solution A evenly, and then stir in a water bath at 25°C for a period of time to obtain reaction product I; ④. Centrifuge the reaction product I, wash it, and dry it to obtain ZIF-8@Co; 2. Preparation of Co-N4 / MnFe2O4 core: ①. Bubble nitrogen into the water to remove oxygen, then dissolve FeCl3 and MnCl2 in oxygen-free water to obtain solution C; ②. Add ZIF-8@Co to solution C, disperse under ultrasonication for a period of time, then add NaOH solution dropwise until the pH of the system reaches 12, and heat the reaction for a period of time to obtain reaction product II. ③. Filter the reaction product II and then wash the obtained solid matter to obtain a precursor; ④. Place the precursor in a tube furnace, pyrolyze it under a nitrogen atmosphere, and cool it to room temperature to obtain the Co-N4 / MnFe2O4 core; 3. Preparation of Co-N4 / MnFe2O4@MnO2: ① Dissolve hexadecyltrimethylammonium bromide in ultrapure water at 60-70°C, add Co-N4 / MnFe2O4 cores, and sonicate for a period of time to obtain solution D. ②. Add KMnO4 solution dropwise to solution D and stir at 70°C for a period of time to obtain reaction product III; ③. Centrifuge the reaction product III and wash the resulting solid to obtain Co-N4 / MnFe2O4@MnO2, which is a core-shell intermediate; 4. PSS surface modification: ① Immerse the core-shell intermediate in an aqueous solution of sodium polystyrene sulfonate, stir at 80°C to 90°C for a period of time, then add a crosslinker solution and continue heating and stirring to crosslink for a period of time to obtain reaction product IV; ②, centrifuge the reaction product IV and then wash it to obtain Co-N4 / MnFe2O4@MnO2-PSS; 5. Dual oxidant loading and sealing: ①. Mix KHSO5 and CaO2, and ball-mill them to a particle size of <5μm to obtain an oxidant mixed powder; ② Place Co-N4 / MnFe2O4@MnO2-PSS in a vacuum drying oven, raise the temperature to 50°C under a reduced pressure of -0.1 MPa, spray the oxidant mixed powder onto the Co-N4 / MnFe2O4@MnO2-PSS, and maintain the pressure at -0.1 MPa and 50°C for 2 hours to obtain Co-N4 / MnFe2O4@MnO2-PSS-OX; ③ Preparation of TiO 2-x / PDA sealing layer: a: Dissolve Ti(OBu)4 in anhydrous ethanol and stir magnetically for a period of time to obtain solution A; dissolve NaBH4 in ultrapure water and dissolve it by ultrasonic for a period of time to obtain solution B; add solution B dropwise to solution A to obtain a blue sol; The blue sol was transferred to a polytetrafluoroethylene-lined reactor and subjected to hydrothermal reaction at 160°C for 10 h to 12 h to obtain a reaction product V. The reaction product V was centrifuged, the obtained solid matter was washed, and vacuum dried to obtain TiO 2-x ; b: Dopamine hydrochloride was dissolved in Tris-HCl buffer, and nitrogen was introduced into the solution for a period of time to deoxygenate it to obtain a PDA prepolymer solution; TiO 2-x Dissolve in anhydrous ethanol, add dispersant, and ultrasonicate for a period of time to obtain TiO 2-x dispersion; TiO 2-x The dispersion was added to the PDA prepolymer solution and stirred at 25°C in the dark for a period of time to obtain a gray-blue composite dispersion. ④. Immerse Co-N4 / MnFe2O4@MnO2-PSS-OX into the gray-blue composite dispersion, oscillate and deposit for a period of time at 25°C and in the dark, and then oscillate and deposit for a period of time under heating and in the dark to obtain Co-N4 / MnFe2O4@MnO2-PSS-OX@PDA / TiO 2-x , which is a manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping.

2. The method for preparing a manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping according to claim 1, characterized in that The molar ratio of Co(NO3)2 to Zn(NO3)2 described in step 1① is (0.5mmol~1.5mmol):10; the volume ratio of the amount of Co(NO3)2 described in step 1① to methanol is (0.5mmol~1.5mmol):100mL; the volume ratio of the amount of 2-methylimidazole described in step 1② to methanol is (30mmol~50mmol):100mL; the stirring time described in step 1③ is 20h~24h; the volume ratio of solution B to solution A described in step 1③ is 1:1; the centrifugal speed described in step 1④ is 8000rpm~10000rpm, and the centrifugal time is 10min~15min; the washing described in step 1④ is washing 3 times~5 times with methanol; the drying temperature described in step 1④ is 40℃~60℃, and the drying time is 4h~6h.

3. The method for preparing a manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping according to claim 1, characterized in that The molar ratio of FeCl3 to MnCl2 described in step 2① is 2:1; the volume ratio of the amount of FeCl3 described in step 2① to the oxygen-free water is 20mmol:100mL; the time of ultrasonic dispersion described in step 2② is 30min~60min; the volume ratio of the mass of ZIF-8@Co described in step 2② to the oxygen-free water described in step 2① is (1.5g~2.5g):100mL; the concentration of the NaOH solution described in step 2② is 1mol / L; the temperature of the heating reaction described in step 2② is 70℃~80℃, and the heating reaction time is 5h~7h; in step 2③, the reaction product II is filtered, and the obtained solid material is washed 3 times to 5 times with anhydrous ethanol; the pyrolysis process described in step 2④ is: first, the temperature is increased from room temperature to 300℃ at a heating rate of 2℃ / min and kept warm, and then the temperature is increased from 300℃ to 600℃ at a heating rate of 5℃ / min and kept warm.

4. The method for preparing a manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping according to claim 1, characterized in that The volume ratio of the amount of hexadecyltrimethylammonium bromide described in step 3① to ultrapure water is (2mmol~3mmol):200mL; the volume ratio of the mass of the Co-N4 / MnFe2O4 core described in step 3① to ultrapure water is (1.0g~1.5g):200mL; the ultrasonic dispersion time described in step 3① is 30min~60min; the concentration of the KMnO4 solution described in step 3② is 0.5mol / L; the stirring time at 70°C in step 3② is 3h~4h; the dropwise addition rate of the KMnO4 solution in step 3② is 2 mL / min; the volume ratio of the KMnO4 solution described in step 3② to the volume ratio of the ultrapure water described in step 3① is 10:100; the centrifugal speed described in step 3③ is 10000 rpm, and the centrifugation time is 5min~10min; in step 3③, the reaction product III is centrifuged, and then the obtained solid material is washed 3 times to 5 times with ultrapure water; the shell thickness of the core-shell intermediate in step 3③ is 20±2nm.

5. The method for preparing a manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping according to claim 1, characterized in that The volume ratio of the mass of the core-shell intermediate described in step 4 ① to the aqueous solution of sodium polystyrene sulfonate is 1g:100mL; the mass fraction of the aqueous solution of sodium polystyrene sulfonate described in step 4 ① is 5%, and the Mw of sodium polystyrene sulfonate is 70 kDa; the stirring time at 80°C~90°C in step 4 ① is 1h~2h; the crosslinker solution described in step 4 ① is a mixture of EDC solution and NHS solution, wherein the volume ratio of EDC solution to NHS solution is 1:1, the concentration of EDC solution is 0.1mol / L, and the concentration of NHS solution is 0.05mol / L; the volume ratio of the crosslinker solution described in step 4 ① to the aqueous solution of sodium polystyrene sulfonate is 10:100; the crosslinking time described in step 4 ① is 30min~60min.

6. The method for preparing a manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping according to claim 1, characterized in that The centrifugal speed described in step 4 ② is 10000 rpm, and the centrifugal time is 5 min~10 min; the washing described in step 4 ② is washing 3 to 5 times with anhydrous ethanol; the molar ratio of CaO2 to KHSO5 described in step 5 ① is 1:3; the mass ratio of the Co-N4 / MnFe2O4@MnO2-PSS and the oxidant mixed powder described in step 5 ② is 100:(25~30); the volume ratio of the amount of Ti(OBu)4 in solution A described in step 5 ③a to anhydrous ethanol is 0.01 mol:50mL; the volume ratio of the amount of NaBH4 in the solution B described in step 5 ③a to ultrapure water is 0.02mol:20mL; the volume ratio of solution A to solution B described in step 5 ③a is 50mL:20mL; the dropping speed described in step 5 ③a is 1mL / min; the time of magnetic stirring described in step 5 ③a is 20min~30min; the time of ultrasonic dissolution described in step 5 ③a is 20min~30min; the centrifugal speed described in step 5 ③a is 12000 rpm, and the centrifugal time is 10min~20min; in step 5 ③a, the solid substance obtained is washed alternately with anhydrous ethanol and water, and then vacuum dried at 60℃~70℃ for 5h~7h.

7. The method for preparing a manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping according to claim 1, characterized in that The volume ratio of dopamine hydrochloride in the PDA prepolymer solution described in step 5 ③b to Tris-HCl buffer is 0.2g:100mL; the concentration of the Tris-HCl buffer is 0.1mol / L, and the pH value is 8.4-8.6; in step 5 ③b, nitrogen is introduced into the solution for deoxygenation for 10 min-15 min; the TiO 2-x TiO in dispersion 2-x , the mass volume ratio of the dispersant to anhydrous ethanol is 0.1g:0.01g:10mL; the dispersant described in step 5 ③b is disodium EDTA; the TiO 2-x The volume ratio of the dispersion to the PDA prepolymer solution is (8-12):100; in step 5 ③b, TiO 2-x The dispersion was added to the PDA prepolymer solution and stirred at 25°C in the dark for 20 min to 30 min to obtain a gray-blue composite dispersion.

8. The method for preparing a manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping according to claim 1, characterized in that The mass ratio of Co-N4 / MnFe2O4@MnO2-PSS-OX described in step 5④ to the volume ratio of the gray-blue composite dispersion is 1g:50mL; in step 5④, Co-N4 / MnFe2O4@MnO2-PSS-OX is immersed in the gray-blue composite dispersion, and oscillated and deposited at 25°C, protected from light, and a rotation speed of 150rpm for 4 hours, and then oscillated and deposited at 40°C, protected from light, and a rotation speed of 150rpm for 2h~3h.

9. Application of a manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping prepared by the preparation method according to claim 1, characterized in that A manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping is used for efficient generation of Fe(IV) for targeted thallium removal.

10. The use of a manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping according to claim 9, characterized in that A manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping is used to efficiently generate Fe(IV) for targeted thallium removal, which is specifically accomplished by the following steps: The manganese ferrite @ manganese dioxide core-shell material based on single-atom cobalt doping is added to the thallium-containing water body and reacted for 15min~20min, and then the manganese ferrite @ manganese dioxide core-shell material based on single-atom cobalt doping is magnetically separated and recovered to obtain treated water; the manganese ferrite @ manganese dioxide core-shell material based on single-atom cobalt doping is then regenerated; the addition amount of the manganese ferrite @ manganese dioxide core-shell material based on single-atom cobalt doping is 0.05g / L~0.1g / L; Tl in the thallium-containing water body is 0.05g / L~0.1g / L; + The concentration is 5μg~100μg / L; the regeneration method is: first use a 2+ The manganese ferrite@manganese dioxide core-shell material based on single-atom cobalt doping was cleaned 2 to 4 times with the pickling solution to desorb thallium, and then immersed in a KMnO4 solution with a concentration of 0.05 mol / L to repair it; the Co-containing 2+ The concentration of H2C2O4 in the pickling solution is 0.1mol / L, the concentration of HCl is 0.05mol / L, and the concentration of Co 2+ The concentration is 0.01mol / L.

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