Functionalized porous alumina ceramic microspheres, preparation method and application

Abstract

The application discloses functionalized porous aluminum oxide ceramic microspheres, a preparation method and application, the ceramic microspheres take aluminum oxide as a main skeleton, and have a through multistage pore structure; and a chelating functional layer is fixed on the outer surface and / or pore inner wall of the ceramic microspheres.The application realizes synchronous construction of balling and pore structure by adopting a solvent-non-solvent exchange induced phase transfer method; multistage pore structure is obtained by adjusting polymer phase content, porogen molecular weight and a coagulation bath; strong adhesion to the surface of Al2O3 is realized by the combined modification of an adhesive primer layer+covalent / coordination immobilization+secondary capture layer, and catechol / amine active sites are provided for subsequent reactions; the ceramic microspheres have high adsorption capacity and selectivity for heavy metal ions in an aqueous solution, can be regenerated by pickling with dilute hydrochloric acid after adsorption saturation, realize cyclic use and heavy metal recovery, and have wide application prospects in the field of heavy metal wastewater treatment.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional materials technology, specifically relating to functionalized porous alumina ceramic microspheres, and also to the preparation method and application of functionalized porous alumina ceramic microspheres. Background Technology

[0002] Industrial wastewater containing heavy metal ions such as lead, cadmium, mercury, copper, nickel, chromium, and arsenic is characterized by high toxicity, strong mobility, and reluctance to degrade. If left untreated, it poses a long-term cumulative risk to water bodies and ecosystems. Existing treatment technologies include chemical precipitation, ion exchange, membrane separation, and adsorption. Among these, adsorption methods have advantages due to their simplicity, ability to achieve deep purification, and ease of coupling with recovery processes.

[0003] Porous silica materials are commonly used as adsorbent carriers in published literature and patents, but their surface chemical and mechanical strength, as well as their long-term stability in complex systems containing strong acids / bases or salts, may still be limited. Meanwhile, the traditional sol-gel / template method for preparing microspheres has a limited window for controlling the pore structure and morphology, and large-scale preparation also faces challenges such as consistency in sphere formation and efficiency in solid-liquid separation.

[0004] Alumina ceramics have higher hardness, wear resistance and thermal / chemical stability, making them suitable for long-term operation under complex water quality conditions. However, the Al2O3 surface lacks specific sites with strong complexing ability for heavy metal ions, requiring innovative surface modification strategies to construct a high-density, strongly bound chelating functional layer, while also taking into account the deep functionalization of the pore inner wall and the stability of regeneration cycle. Summary of the Invention

[0005] The purpose of this invention is to provide functionalized porous alumina ceramic microspheres, which solves the problem of poor adsorption capacity of existing alumina ceramic adsorbent materials for heavy metal ions.

[0006] Another objective of this invention is to provide a method for preparing functionalized porous alumina ceramic microspheres.

[0007] Another objective of this invention is to provide applications of functionalized porous alumina ceramic microspheres.

[0008] Another objective of this invention is to provide a method for adsorbing and recovering heavy metal ions using functionalized porous alumina ceramic microspheres.

[0009] The first technical solution adopted in this invention is a functionalized porous alumina ceramic microsphere. The ceramic microsphere has a multi-level porous structure with alumina as the main framework, including at least one of mesopores and macropores. A chelating functional layer is immobilized on the outer surface and / or inner wall of the pores of the ceramic microsphere. The chelating functional layer contains groups that can form coordination bonds with heavy metal ions. The groups include one or more of hydroxyoxime, mercapto, phosphonic acid, amino, imidazole, catechol, carboxyl, and thiourea groups. The chelating functional layer includes an adhesion base layer and a chelating ligand layer. The adhesion base layer is used to achieve strong adhesion to the surface of alumina and provide reactive sites, while the chelating ligand layer is used to provide selective complexation sites for heavy metal ions.

[0010] The invention is further characterized in that,

[0011] The ceramic microspheres have a particle size of 5–2000 μm and a sphericity ≥0.90; the bulk density of the ceramic microspheres is 0.3–1.6 g / cm³, and the compressive strength of a single particle is 0.5–50 N.

[0012] The pore size distribution of the hierarchical pore structure satisfies the following: mesopore size 2–50 nm, macropore size 50 nm–20 μm; specific surface area 20–600 m² / g, and pore volume 0.2–3.0 cm³ / g.

[0013] The chelating ligand layer material includes one or more of the following: thiol small molecules, amino polycarboxylic acid ligands, hydroxyoxime-containing polymers, and phosphonic acid-containing polymers; The chelated functional layer is constructed via a combined route of surface activation-initiated polymerization / click reaction-ligand immobilization, wherein the surface activation is selected from one or more of plasma treatment, persulfate oxidation, ozone / ultraviolet treatment, and alkali treatment.

[0014] The ceramic microspheres are also loaded with a trapping layer, which is a metal-organic framework (MOF), a layered bimetallic hydroxide (LDH), a metal oxide / hydroxide nanosheet, or a composite thereof.

[0015] Wherein, the metal-organic framework (MOF) is selected from ZIF-8, ZIF-67, UiO-66 or their derivatives; the layered bimetallic hydroxide (LDH) is selected from NiFe-LDH, MgAl-LDH, CoAl-LDH; and the metal oxide / hydroxide nanosheets are selected from one or more of FeOOH, MnO2, TiO2, and ZrO2.

[0016] The second technical solution adopted in this invention is: a method for preparing functionalized porous alumina ceramic microspheres, as detailed below: Step 1: Mix aluminum oxide powder or boehmite sol with polymer binder, pore-forming agent, and dispersant in an organic solvent to obtain a dropping solution; introduce the dropping solution into a non-solvent coagulation bath by dropping, spraying, or microfluidic methods to cause phase separation / phase transfer and form a porous spherical preform; The solid content of the drop solution is 20–65 wt%, the drop temperature is 10–40℃, the coagulation bath temperature is 10–40℃, the drop height is 2–30 cm, the needle inner diameter is 0.1–2.0 mm, and the coagulation bath residence time is 0.2–6 h, so as to achieve solvent-non-solvent exchange and phase separation.

[0017] Step 2: The porous spherical preform is subjected to solvent replacement and drying, followed by thermal degreasing and sintering at 1100–1650℃ to obtain alumina ceramic microsphere substrate with a through-hole multi-level pore structure. Step 3: Construct a chelated functional layer on the surface of the alumina ceramic microsphere substrate.

[0018] The invention is further characterized in that, The porogen described in step 1 can be a water-soluble porogen or a thermally decomposable / soluble porogen; the water-soluble porogen is selected from polyethylene glycol (PEG) (molecular weight 200–20000), polyvinylpyrrolidone (PVP) (molecular weight 8000–130000), and polyvinyl alcohol (PVA); the thermally decomposable / soluble porogen is selected from one or more of starch, sucrose, urea, ammonium bicarbonate, polymethyl methacrylate (PMMA) microspheres, and paraffin microparticles; the amount of the porogen used is 1–40 wt% of the mass of the alumina solid.

[0019] The polymeric binder mentioned in step 1 is selected from one or more of polyethersulfone (PES), polyvinylidene fluoride (PVDF), polyvinylpyrrolidone (PVP), and polyacrylonitrile (PAN). Alumina can be replaced by zirconium oxide (ZrO2), titanium dioxide (TiO2), silicon nitride (Si3N4), silicon carbide (SiC), spinel (MgAl2O4), or Al2O3-ZrO2 / Al2O3-TiO2 composite systems to achieve optimized selectivity and stability for different ionic systems.

[0020] The organic solvent is one or more of N-methylpyrrolidone (NMP), dimethylformamide (DMF), and dimethylacetamide (DMAc); The non-solvent is water or a water / alcohol mixture.

[0021] Step 2 involves washing the porous spherical preform three times in water / ethanol, drying it at 60℃ for 12 h, with a thermal degreasing rate of 0.5–5℃ / min, a degreasing temperature of 400–800℃, and a holding time of 0.5–6 h; and a sintering temperature of 1200–1650℃ and a holding time of 0.5–6 h, to obtain an alumina ceramic microsphere substrate with an open through-pore structure and to avoid pore collapse. The chelating functional layer mentioned in step 3 includes an adhesion base layer and a chelating ligand layer. The adhesion base layer is a polydopamine layer. The adhesion base layer is prepared by dispersing the alumina ceramic microspheres in an aminomethane buffer solution with a pH of 8.0–9.0, adding dopamine hydrochloride, and stirring for 1–24 h to allow polydopamine to self-aggregate and deposit on the outer surface of the microspheres and the inner wall of the pores. The concentration of dopamine hydrochloride is 0.2–5.0 g / L, the solid-liquid ratio is 1:(20–500) g / mL, and the reaction temperature is 10–35℃. The multi-level porous structure is an outer dense-inner loose structure or a radial gradient structure, with an outer layer average pore diameter of 0.05–2 μm and a thickness of 10–300 μm, in order to improve mechanical strength and reduce operating pressure drop; The chelating functional layer described in step 3 is obtained by grafting ligands containing thiol or amine groups onto the polydopamine layer via Michael addition / Schiff base reaction; or by introducing a chelating ligand layer containing hydroxyoxime / phosphonic acid side chains via surface-initiated in-situ polymerization; wherein the thiol-containing ligands are cysteamine, mercaptoethylamine, 3-mercaptopropionic acid, or mercaptoacetic acid; and the amine-containing ligands are polyethyleneimine (PEI), polyamines, or amino acid derivatives.

[0022] The third technical solution adopted in this invention is: the application of functionalized porous alumina ceramic microspheres in the adsorption of heavy metal ions in aqueous solution, wherein the heavy metal ions include lead (Pb²). + , cadmium Cd² + Mercury (Hg²) + Copper Cu² + Zinc (Zn²) + , NickelNi² + Chromium Cr(III) / Cr(VI), Arsenic As(III) / As(V), Silver Ag + One or more of the following; The aqueous solution is industrial wastewater, acidic mine wastewater, electroplating wastewater, or a complex system containing salt; and the adsorption can be carried out in the range of pH 2 to 10 and salinity 0 to 100 g / L.

[0023] The fourth technical solution adopted in this invention is: a method for adsorbing and recovering heavy metal ions, comprising: Step 1: Functionalized porous alumina ceramic microspheres are contacted with an aqueous solution containing heavy metal ions for adsorption; In step 1, the contact method is a column-type fixed bed, fluidized bed, or stirred tank; the adsorption time is 1–180 min. Step 2: Solid-liquid separation yields metal-loaded microspheres; The solid-liquid separation method in step 2 is sieving, sedimentation, filtration or centrifugation; Step 3: Desorption and regeneration are achieved by at least one of the following methods: acid washing, complexing agent elution, salt solution replacement, or electrochemical regeneration, and the heavy metal ions are recovered; The acid washing in step 3 is performed with 0.01–2.0 mol / L hydrochloric acid or nitric acid; the complexing agent elution is performed with 0.01–0.5 mol / L EDTA or citrate solution; the salt solution replacement is performed with 1–200 g / L NaCl or CaCl2 solution; and the electrochemical regeneration potential is 0.2–2.5 V (relative to Ag / AgCl). Step 4: Reuse the regenerated microspheres in Step 1.

[0024] The specific synthesis mechanism of this invention is as follows: (1) The present invention uses solvent-nonsolvent exchange-induced phase separation (phase transfer method) to achieve simultaneous construction of spheres and pore structures: by controlling the polymer phase content and the molecular weight of the pore-forming agent, a multi-level pore structure with external density and internal looseness or radial gradient is obtained, which significantly improves the mass transfer rate and reduces the pressure drop; this method is friendly to large-scale drop / spray sphere formation and the particle size distribution is controllable.

[0025] (2) The present invention proposes a combination modification of “adhesive base coating + covalent / coordination immobilization + secondary trapping layer”: using polydopamine (PDA) as a general adhesive base coating to achieve strong adhesion to the Al2O3 surface and provide catechol / amine active sites for subsequent reactions; through Michael addition / Schiff base reaction, click chemistry or surface-initiated in-situ polymerization, a high-density chelating ligand layer (such as mercapto, hydroxyoxime, phosphonic acid, amino polycarboxylic acid, etc.) is constructed in situ on the inner wall of the pores; further loading MOF / LDH or metal oxide nanosheets to form a selective trapping layer, which works synergistically with the chelating layer to achieve rapid enrichment + strong complexation and immobilization, and improve the ability to resist interference from coexisting ions.

[0026] The beneficial effects of this invention are as follows: (1) High stability: The Al2O3 framework provides higher mechanical strength and chemical corrosion resistance, making it suitable for multiple regeneration cycles; (2) High efficiency mass transfer: The phase transfer-induced hierarchical porous structure improves the internal diffusion rate and shortens the time to reach adsorption equilibrium; (3) High selectivity and high capacity: Multilayer synergistic functionalization provides high-density, strong-binding chelation sites, and can achieve specific ions (such as Hg²) through secondary trapping layers. + Pb² +Enhanced selectivity of As(V)); (4) Easy to separate and recyclable: The microsphere morphology facilitates sedimentation / filtration; the regenerated eluent can be directly entered into recovery units such as electrodeposition / crystallization. Detailed Implementation

[0027] The present invention will now be described in detail with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0028] Example 1: Preparation of porous Al2O3 ceramic microsphere substrate by phase transfer method (1) Preparation of the dropping solution: Weigh 40 g of α-Al2O3 powder (D50≈0.5–1.5 μm), 2 g of PVP, 6 g of PES, and 4 g of PEG-4000, add 120 mL of NMP; add 0.2–0.5 g of dispersant (ammonium polyacrylate); ball mill / stir for 12–24 h to obtain a uniform slurry.

[0029] (2) Phase transfer to spheres: The above slurry is dropped into a deionized water coagulation bath (20–30℃) through a dropping needle (inner diameter 0.3–1.0 mm) at a height of 5–20 cm; the solvent-nonsolvent exchange is completed by standing in the coagulation bath for 0.5–2 h to obtain a porous spherical preform.

[0030] (3) Solvent replacement and drying: The green body is washed in water / ethanol 2–6 times in sequence, and dried at 60℃ for 4–12 h.

[0031] (4) Degreasing and sintering: Degreasing is performed by heating to 600℃ at 1–3℃ / min and holding for 2 h, followed by heating to 1350–1550℃ and holding for 2–4 h to sinter, resulting in porous Al2O3 ceramic microspheres.

[0032] The porous Al2O3 ceramic microspheres prepared in this embodiment have a particle size of 200–500 μm; macropores of 0.5–3 μm and mesopores of 6–15 nm; specific surface area of ​​120–220 m² / g; and compressive strength significantly higher than that of silicon-based microspheres of the same particle size.

[0033] Example 2: Polydopamine undercoat + thiol ligand grafting (for Hg²) + / Pb² + ) (1) PDA deposition: Take 5 g of microspheres from Example 1, disperse them in 500 mL of Tris buffer (10 mM, pH 8.5), add 1.0 g of dopamine hydrochloride, stir at room temperature for 6 h; wash until the supernatant is clear, dry at 60 °C to obtain PDA@Al2O3 microspheres; (2) Thiol grafting: PDA@Al2O3 microspheres were dispersed in ethanol / water (v / v=7 / 3), thiol-containing amine molecules (cysteamine or mercaptoethylamine) were added, and the reaction was carried out under mild alkaline conditions for 4–12 h. Thiol groups were immobilized by Michael addition / Schiff base reaction. After washing and drying, SH-PDA@Al2O3 was obtained.

[0034] Example 3: Surface-initiated polymerization to construct a hydroxyoxime-based polymer brush layer (for Cu²) + / Ni² + / Cd² + ) (1) Introducing initiation sites on the PDA layer: ATRP or RAFT initiation groups are introduced by reacting the amine / phenolic hydroxyl groups on the PDA with an initiator containing active esters. (2) In-situ polymerization: Surface-initiated polymerization is carried out using nitrile-containing monomers as the main monomers to obtain nitrile polymer layers; (3) Hydroxyxime conversion: Hydroxylamine hydrochloride is used to convert nitrile groups to hydroxyxime groups under alkaline conditions to obtain a high-density hydroxyxime chelate layer; this layer has a strong complexing ability for a variety of transition metal ions and is reversibly regenerated.

[0035] Example 4: Secondary capture layer (MOF / LDH) synergistic enhancement of selectivity (optional) After completing the chelation layer construction in Example 2 or 3, MOF or LDH nanosheets (such as ZIF or NiFe-LDH) can be loaded onto the outer surface / pore region through in-situ growth or layer-by-layer self-assembly to form a selective trapping layer, which can be used to improve the selectivity and anti-interference ability for specific ions or anionic forms (such as As(V) and Cr(VI)).

[0036] Example 5 The method for adsorbing and recovering heavy metal ions according to the present invention is as follows: (1) Adsorption: Take 0.1 g of functionalized microspheres and add them to 100 mL of Pb² + Adsorption was performed in simulated wastewater at a concentration of 100 mg / L using shaking; the adsorption capacity was calculated by determining the residual concentration using ICP-OES.

[0037] Regeneration and recovery: Desorption is performed using a 0.05–1.0 M acid solution or an eluent containing a complexing agent; the eluent can be fed into an electrodeposition or crystallization recovery unit; the microspheres are washed to neutral and then reused as in Example 5.

[0038] Example 6 The preparation method of the functionalized porous alumina ceramic microspheres of the present invention is as follows: Step 1: Mix aluminum oxide powder with polyvinylidene fluoride (PVDF), polyethylene glycol (PEG) with a molecular weight of 8000, and ammonium polyacrylate (DMAc) in an organic solvent to obtain a dropping solution; The amount of pore-forming agent used is 20 wt% of the solid aluminum oxide. The solid content of the drop solution was 45 wt%, the drop temperature was 25℃, the coagulation bath temperature was 30℃, the drop height was 20 cm, the needle inner diameter was 0.5 mm, and the coagulation bath residence time was 3 h, thus achieving solvent-non-solvent exchange and phase separation. The dripping solution is introduced into a deionized water / alcohol mixed phase coagulation bath by dripping to cause phase separation / phase transfer and form a porous spherical preform; wherein, the volume ratio of water to alcohol in the water / alcohol mixed system is 70:30, and the alcohol is ethanol or isopropanol; Step 2: The porous spherical preform was washed 5 times in water / ethanol, dried at 60℃ for 8 hours, then heated to 600℃ at 2℃ / min and held for 2 hours to degrease, and then heated to 1200℃ for sintering to obtain alumina ceramic microsphere substrate with a through-hole multi-level pore structure. Step 3: Construct an adhesion primer on the surface of the alumina ceramic microsphere substrate, and immobilize the chelated functional layer through covalent grafting, coordination fixation, in-situ polymerization, or layer-by-layer self-assembly; details are as follows: Alumina ceramic microspheres were dispersed in an aminomethane buffer solution at pH 9.0, and dopamine hydrochloride at a concentration of 2.0 g / L was added and the mixture was stirred for 12 h to allow polydopamine to self-polymerize and deposit on the outer surface and inner walls of the microspheres. The chelating functional layer was constructed by grafting ligands containing thiol or amine groups onto the chelating ligand layer via Michael addition / Schiff base reaction; or by introducing a polymer brush layer containing hydroxyoxime / phosphonic acid side chains through surface-initiated in-situ polymerization.

[0039] Example 7 The preparation method of the functionalized porous alumina ceramic microspheres of the present invention is as follows: Step 1: Mix aluminum oxide powder with polyvinylidene fluoride (PVDF), polyvinylpyrrolidone (70,000 molecular weight), and ammonium polyacrylate in dimethylacetamide (DMAc) to obtain a dropping solution; The solid content of the drop solution is 55 wt%, the drop temperature is 20℃, the coagulation bath temperature is 15℃, the drop height is 10 cm, the needle inner diameter is 1.5 mm, and the coagulation bath residence time is 5 h, so as to achieve solvent-non-solvent exchange and phase separation. The amount of pore-forming agent used is 30 wt% of the solid aluminum oxide. The dripping solution is introduced into a deionized water / alcohol mixed phase coagulation bath by dripping to cause phase separation / phase transfer and form a porous spherical preform; wherein, the volume ratio of water to alcohol in the water / alcohol mixed system is 30:70, and the alcohol is isopropanol.

[0040] Step 2: The porous spherical preform was washed 4 times in water / ethanol, dried at 60℃ for 10h, then heated to 600℃ at 3℃ / min and held for 2h to degrease, and then sintered at 1550℃ to obtain alumina ceramic microsphere substrate with a through-hole multi-level pore structure. Step 3: Construct an adhesion primer on the surface of the alumina ceramic microsphere substrate, and immobilize the chelated functional layer through covalent grafting, coordination fixation, in-situ polymerization, or layer-by-layer self-assembly; details are as follows: Alumina ceramic microspheres were dispersed in an aminomethane buffer solution at pH 8.0, and dopamine hydrochloride at a concentration of 5.0 g / L was added and the mixture was stirred for 16 h to allow polydopamine to self-polymerize and deposit on the outer surface and inner walls of the microspheres. The chelating functional layer was grafted onto the polydopamine layer with ligands containing thiol or amine groups through Michael addition / Schiff base reaction; or a chelating ligand layer containing hydroxyoxime / phosphonic acid side chains was introduced through surface-initiated in-situ polymerization.

[0041] Example 8 The preparation method of the functionalized porous alumina ceramic microspheres of the present invention is as follows: Step 1: Mix aluminum oxide powder with polyvinylidene fluoride (PVDF), sucrose, and ammonium polyacrylate (MPA) dispersant in dimethylacetamide (DMAc) to obtain a dropping solution; The solid content of the drop solution is 55 wt%, the drop temperature is 20℃, the coagulation bath temperature is 15℃, the drop height is 10 cm, the needle inner diameter is 1.5 mm, and the coagulation bath residence time is 5 h, so as to achieve solvent-non-solvent exchange and phase separation. The amount of sucrose used as a pore-forming agent is 18 wt% of the solid aluminum oxide. The dripping solution is introduced into a deionized water / alcohol mixed phase coagulation bath by dripping to cause phase separation / phase transfer and form a porous spherical preform; wherein, the volume ratio of water to alcohol in the water / alcohol mixed system is 25:65, and the alcohol is ethanol; Step 2: The porous spherical preform was washed three times in water / ethanol, dried at 60℃ for 12h, then heated to 600℃ at 3℃ / min and held for 2h to degrease, and then sintered at 1550℃ to obtain alumina ceramic microsphere substrate with a through-hole multi-level pore structure. Step 3: Construct an adhesion primer on the surface of the alumina ceramic microsphere substrate, and immobilize the chelated functional layer through covalent grafting, coordination fixation, in-situ polymerization, or layer-by-layer self-assembly; details are as follows: Alumina ceramic microspheres were dispersed in an aminomethane buffer solution at pH 8.0, and dopamine hydrochloride at a concentration of 5.0 g / L was added and the mixture was stirred for 16 h to allow polydopamine to self-polymerize and deposit on the outer surface and inner walls of the microspheres. The chelating functional layer was grafted onto the polydopamine layer with ligands containing thiol or amine groups through Michael addition / Schiff base reaction; or a chelating ligand layer containing hydroxyoxime / phosphonic acid side chains was introduced through surface-initiated in-situ polymerization.

Claims

1. Functionalized porous alumina ceramic microspheres, characterized in that, The ceramic microspheres have an alumina framework and a permeable hierarchical porous structure, which includes at least one of mesopores and macropores. A chelating functional layer is immobilized on the outer surface and / or inner wall of the pores of the ceramic microspheres. This chelating functional layer contains groups capable of forming coordination bonds with heavy metal ions, including one or more of hydroxyoxime, mercapto, phosphonic acid, amino, imidazole, catechol, carboxyl, and thiourea groups. The chelating functional layer comprises an adhesion base layer and a chelating ligand layer. The adhesion base layer is used to achieve strong adhesion to the alumina surface and provide reactive sites, while the chelating ligand layer is used to provide selective complexation sites for heavy metal ions.

2. The functionalized porous alumina ceramic microspheres according to claim 1, characterized in that, The ceramic microspheres have a particle size of 5 μm–2000 μm and a sphericity ≥0.90; the bulk density of the ceramic microspheres is 0.3–1.6 g / cm³; the pore size distribution of the hierarchical pore structure satisfies the following: mesopore size 2–50 nm, macropore size 50 nm–20 μm; specific surface area 20–600 m² / g, and pore volume 0.2–3.0 cm³ / g.

3. The functionalized porous alumina ceramic microspheres and system according to claim 1, characterized in that: The chelating ligand layer material includes one or more of the following: thiol small molecules, amino polycarboxylic acid ligands, hydroxyoxime-containing polymers, and phosphonic acid-containing polymers; The chelated functional layer is constructed via a combined route of surface activation-initiated polymerization / click reaction-ligand immobilization, wherein the surface activation is selected from one or more of plasma treatment, persulfate oxidation, ozone / ultraviolet treatment, and alkali treatment.

4. The functionalized porous alumina ceramic microspheres according to claim 1, characterized in that: The ceramic microspheres are further loaded with a trapping layer, which is a metal-organic framework (MOF), a layered bimetallic hydroxide (LDH), a metal oxide / hydroxide nanosheet, or a composite thereof; wherein the MOF is selected from ZIF-8, ZIF-67, UiO-66, or derivatives thereof; the LDH is selected from NiFe-LDH, MgAl-LDH, and CoAl-LDH; and the metal oxide / hydroxide nanosheet is selected from one or more of FeOOH, MnO2, TiO2, and ZrO2.

5. A method for preparing functionalized porous alumina ceramic microspheres, characterized in that, Specifically as follows: Step 1: Mix aluminum oxide powder or boehmite sol with polymer binder, pore-forming agent, and dispersant in an organic solvent to obtain a dropping solution; introduce the dropping solution into a non-solvent coagulation bath by dropping, spraying, or microfluidic methods to cause phase separation / phase transfer and form a porous spherical preform; Step 2: Wash and dry the porous spherical preform, then perform hot degreasing and sinter at 1100–1650℃ to obtain alumina ceramic microsphere substrate with a through-hole multi-level pore structure. Step 3: Construct a chelated functional layer on the surface of the alumina ceramic microsphere substrate.

6. The method for preparing functionalized porous alumina ceramic microspheres according to claim 5, characterized in that: The polymeric binder mentioned in step 1 is selected from one or more of polyethersulfone (PES), polyvinylidene fluoride (PVDF), polyvinylpyrrolidone (PVP), and polyacrylonitrile (PAN). The organic solvent is one or more of N-methylpyrrolidone (NMP), dimethylformamide (DMF), and dimethylacetamide (DMAc); The solid content of the drop solution is 20–65 wt%, the drop temperature is 10–40℃, the coagulation bath temperature is 10–40℃, the drop height is 2–30 cm, the needle inner diameter is 0.1–2.0 mm, and the coagulation bath residence time is 0.2–6 h, so as to achieve solvent-non-solvent exchange and phase separation. The amount of the pore-forming agent is 1 to 40 wt% of the mass of the solid aluminum oxide. The non-solvent is water or a water / alcohol mixture; wherein the volume ratio of water to alcohol in the water / alcohol mixture is 90:10 to 10:90, and the alcohol is ethanol or isopropanol.

7. The method for preparing functionalized porous alumina ceramic microspheres according to claim 5, characterized in that: Step 2: The heating rate for hot degreasing is 0.5–5℃ / min, the degreasing temperature is 400–800℃, and the holding time is 0.5–6 h; the sintering temperature is 1200–1650℃, and the holding time is 0.5–6 h.

8. The method for preparing functionalized porous alumina ceramic microspheres according to claim 5, characterized in that: The chelating functional layer mentioned in step 3 includes an adhesion base layer and a chelating ligand layer. The adhesion base layer is a polydopamine layer, and the adhesion base layer is prepared by dispersing the alumina ceramic microspheres in an aminomethane buffer solution with a pH of 8.0–9.0, adding dopamine hydrochloride, and stirring for 1–24 h to allow polydopamine to self-aggregate and deposit on the outer surface of the microspheres and the inner wall of the pores. The concentration of dopamine hydrochloride is 0.2–5.0 g / L, the solid-liquid ratio is 1:20–500 g / mL, and the reaction temperature is 10–35℃. The chelating functional layer described in step 3 involves covalently grafting ligands containing thiol or amine groups onto the polydopamine layer via Michael addition / Schiff base reaction; or introducing a chelating ligand layer containing hydroxyoxime / phosphonic acid side chains via surface-initiated in-situ polymerization; wherein the thiol-containing ligands are cysteamine, mercaptoethylamine, 3-mercaptopropionic acid, or mercaptoacetic acid; and the amine-containing ligands are polyethyleneimine (PEI), polyamines, or amino acid derivatives.

9. The application of functionalized porous alumina ceramic microspheres in the adsorption of heavy metal ions in aqueous solution, characterized in that, The heavy metal ions include lead (Pb²). + , cadmium Cd² + Mercury (Hg²) + Copper Cu² + Zinc (Zn²) + , NickelNi² + Chromium Cr(III) / Cr(VI), Arsenic As(III) / As(V), Silver Ag + One or more of them.

10. A method for adsorbing and recovering heavy metal ions, characterized in that, include: Step 1: Functionalized porous alumina ceramic microspheres are contacted with an aqueous solution containing heavy metal ions for adsorption; Step 2: Solid-liquid separation yields metal-loaded microspheres; Step 3: Desorption and regeneration are achieved by at least one of the following methods: acid washing, complexing agent elution, salt solution replacement, or electrochemical regeneration, and the heavy metal ions are recovered; Step 4: Reuse the regenerated microspheres in Step 1.