Composite particle for repairing polluted water body as well as preparation method and application of composite particle

Abstract

The invention relates to composite particles for repairing polluted water and a preparation method and application of the composite particles, and belongs to the technical field of environmental functional materials and water pollution governing. Through double chemical modification of acrylic acid grafting and glutaraldehyde crosslinking, a sodium alginate / chitosan charcoal carrier is modified into a high-strength pH-responsive intelligent carrier, and the composite particles are used for repairing the polluted water. And then the plant growth-promoting bacteria and sodium percarbonate are compounded and granulated. After being added, the carrier can effectively resist SPC initial oxidation impact, protect the activity of thalli, intelligently release PGPB along with the change of pH, accurately link and deepen the oxidative degradation process, and realize efficient and deep mineralization of pollutants. Experiments show that the microbial protection rate of the material is greater than 95%, the 72-hour phenol mineralization rate reaches 85%, and the material is remarkably superior to that of a traditional method. According to the invention, the problem of compatibility between the oxidant and microorganisms is solved, and a new technology is provided for efficient and green water body remediation.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional materials and water pollution control technology, and relates to a composite particle for remediating polluted water bodies, its preparation method, and its application. Background Technology

[0002] With industrial development, the treatment of recalcitrant organic pollutants (such as phenol, petroleum hydrocarbons, and antibiotics) in water bodies has become a major environmental challenge. Sodium percarbonate (SPC), as a solid hydrogen peroxide source, is often used in advanced oxidation processes due to its safety, low cost, and buffering capacity. However, its use alone has problems such as incomplete oxidation, low mineralization rate, and the potential generation of toxic intermediate products. Plant growth promoters (PGPB) can degrade various organic compounds and promote ecological restoration, making it an environmentally friendly bioremediation method. However, its activity is easily inhibited in high-concentration pollutants and oxidative stress environments.

[0003] In existing technologies, attempts to combine SPC with PGPB often employ stepwise addition or simple physical mixing. Stepwise addition is cumbersome, and residual oxidants and intermediate products from the oxidation stage may continuously inhibit the activity of subsequently added microorganisms. Simple physical mixing, on the other hand, can lead to the rapid release of reactive oxygen species from SPC in the initial stage, directly killing PGPB and causing the bioremediation function to fail. Although some studies have used carriers such as sodium alginate / chitosan@biochar (SA / CS@BC) to immobilize microorganisms to resist biotoxicity, when these traditional carriers are combined with strong oxidants such as SPC to construct integrated materials, significant drawbacks are exposed: First, the ionic cross-linking network formed by calcium ions has low mechanical strength and is easily damaged under oxidation and fluid shear, providing limited protection for microorganisms; second, the carrier function is passive and cannot intelligently regulate the release behavior of microorganisms according to changes in the chemical environment (such as pH) during the remediation process, resulting in poor spatiotemporal coordination between the two key stages of "oxidative pretreatment" and "biodegradation," leading to low synergistic efficiency.

[0004] Therefore, developing an integrated repair material that can actively protect and intelligently regulate, thereby achieving deep, efficient, and seamless synergy between chemical oxidation and biodegradation, is a technological bottleneck that urgently needs to be overcome in this field. Summary of the Invention

[0005] This invention provides a composite particle for remediating polluted water bodies, its preparation method, and its application. The core of this invention lies in constructing an intelligent functionalized carrier with both high strength and pH responsiveness through dual chemical modification of the carrier. This precisely solves the compatibility problem between SPC (sodium percarbonate) and PGPB (plant growth promoter), and achieves sequential synergy of their remediation functions.

[0006] Technical solution: A method for preparing composite particles for remediating polluted water bodies, comprising the following steps:

[0007] S1. The biochar is subjected to acid oxidation treatment to obtain oxidized biochar;

[0008] S2. Sodium alginate and acrylic acid are graft copolymerized under the action of an initiator to obtain carboxylated sodium alginate.

[0009] S3. Oxidized biochar, carboxylated sodium alginate, chitosan and plant growth-promoting bacteria solution are mixed and added dropwise into a cross-linking bath containing calcium ions and glutaraldehyde to solidify and form gel microspheres. After post-treatment, functionalized composite carriers are obtained.

[0010] S4. The dried functionalized composite carrier microspheres are mixed with sodium percarbonate and pH buffer and granulated to obtain composite particles.

[0011] Furthermore, the specific operation of S1 is as follows:

[0012] Biochar powder was added to a mixture of concentrated nitric acid and concentrated sulfuric acid and refluxed at 70°C for 5 hours; washed until neutral and dried at 105°C to obtain oxidized biochar; wherein the volume ratio of concentrated nitric acid to concentrated sulfuric acid was 3:1.

[0013] Furthermore, the specific operation of S2 is as follows:

[0014] Sodium alginate was dissolved in water, acrylic acid was added, nitrogen gas was passed through, potassium persulfate was added, and the reaction was carried out at 65°C for 4 hours. The product was precipitated and washed with ethanol and freeze-dried to obtain carboxylated sodium alginate. The ratio of sodium alginate, acrylic acid, water and potassium sulfate was 2g:(2.2-5.5)mL:98mL:0.03g. The grafting rate of the added acrylic acid grafted to modify sodium alginate was controlled at 40%-60%.

[0015] Furthermore, the specific operations of S3 are as follows:

[0016] First, carboxylated sodium alginate and chitosan were dissolved in acetic acid solution, then oxidized biochar was added and ultrasonically dispersed; then plant growth-promoting bacteria suspension was added and mixed in an ice bath; the mixture was dropped into a cross-linking bath containing CaCl2 and glutaraldehyde (glutaraldehyde was used as a covalent cross-linking agent), cross-linked for a period of time, the microspheres were collected, washed with PBS, and freeze-dried to obtain the functionalized composite carrier.

[0017] The crosslinking bath contained glutaraldehyde at a volume concentration of 0.5%-1.5%, CaCl2 at a concentration of 0.1M, and plant growth-promoting bacteria suspension containing Bacillus subtilis.

[0018] Furthermore, the specific operation of S4 is as follows:

[0019] The dried functionalized composite carrier, sodium percarbonate, and sodium bicarbonate-sodium citrate buffer were mixed and granulated into 2.0-3.0 mm wet particles using 3% PVA solution as a binder. The particles were then dried in a fluidized bed at 40°C to obtain composite particles for remediating polluted water bodies.

[0020] The mass ratio of the functionalized composite carrier, sodium percarbonate, and sodium bicarbonate-sodium citrate buffer is (15-30):(60-80):5; in the sodium bicarbonate-sodium citrate buffer, the mass ratio of sodium bicarbonate to sodium citrate is 4:1.

[0021] The composite particles prepared according to the preparation method have a particle size of 1.5~3.0 mm, wherein the functionalized composite carrier microspheres account for 15%~30% of the total mass of the particles, sodium percarbonate accounts for 60%~80%, and the remainder is a pH buffer (sodium bicarbonate and sodium citrate buffer).

[0022] The composite particles can be used to prepare remediation agents for water bodies contaminated by phenolic compounds, petroleum hydrocarbons, or polycyclic aromatic hydrocarbons; in application, the composite particles are added to the contaminated water body to be remediated.

[0023] Compared with the prior art, the technical solution provided by this invention brings the following significant and verifiable advancements:

[0024] (1) Breakthrough in carrier mechanical properties: By introducing a glutaraldehyde covalent cross-linking network, the wet mechanical strength of the functionalized composite carrier of the present invention is increased to more than 3 times that of the traditional calcium ion cross-linked carrier (from about 0.08 N / ball to about 0.25 N / ball), which greatly enhances the physical stability and durability of the material in actual water applications.

[0025] (2) The compatibility problem has been fundamentally solved: In an oxidative stress environment simulating the presence of SPC, the 24-hour protection rate of the carrier of the present invention against PGPB exceeds 95%, while the protection rate of traditional ion-crosslinked carriers is only 40%-60%. This conclusively proves that the rigid covalent network constructed by chemical modification and the intelligent shrinkage behavior of pH-responsive gel produce a synergistic protective effect, ensuring the activity of microorganisms.

[0026] (3) Significantly enhanced remediation efficiency and mineralization depth: In a comparative experiment treating 500 mg / L phenol-simulated wastewater, the composite particles of this invention achieved near-complete degradation of pollutants (>99%) within 72 hours, with a total organic carbon (TOC) removal rate of 85%, indicating that the pollutants were thoroughly mineralized. The final mineralization degree was about 13 percentage points higher than that of the unmodified carrier system and more than 45 percentage points higher than that of the simple physical mixing method, which strongly verifies the high efficiency of the "oxidation-biology" intelligent relay synergistic mechanism.

[0027] (4) Environmentally friendly and easy to use: All major components of the system are biodegradable or environmentally friendly. The granular form is easy to store, transport and add. The entire process from oxidation pretreatment to deep biological remediation can be completed in one operation. It is suitable for the remediation of rivers, industrial wastewater tailwater and other scenarios. Attached Figure Description

[0028] Figure 1 The diagram shows the structure of the composite particles prepared in Example 1 and the flowchart of the synergistic repair mechanism.

[0029] Figure 2 This is a comparison graph showing the change of phenol concentration over time during the repair process between Example 1 and each comparative example.

[0030] Figure 3 The bar chart shows the total organic carbon (TOC) removal rates of Example 1 and the comparative examples after 72 hours of remediation. Detailed Implementation

[0031] The technical solution of the present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited to the embodiments described.

[0032] In the following examples and comparative examples, the plant growth-promoting bacteria solution was a solution containing Bacillus subtilis, which was purchased from Baosai Plasmid Culture Company. Sodium alginate, chitosan, biochar powder, and PVA were purchased from Yixing Aladdin Chemical Trading Co., Ltd.

[0033] Example 1: Preparation of functionalized composite carrier and repair particles.

[0034] Step 1: Preparation of Oxidized Biochar (O-BC): Add 10g of biochar powder to 150mL of a mixture of concentrated nitric acid and concentrated sulfuric acid (3:1, v / v), and reflux at 70℃ for 5 hours. Wash until neutral and dry at 105℃. The mass fraction of concentrated sulfuric acid is 98%; the mass fraction of concentrated nitric acid is 65%.

[0035] Step 2, Preparation of carboxylated sodium alginate (SA-g-AA): Dissolve 2g of sodium alginate in 98mL of water, add 4mL of acrylic acid, purge with nitrogen, then add 0.03g of potassium persulfate, and react at 65℃ for 4 hours. The product is precipitated and washed with ethanol, lyophilized, and the grafting rate is measured to be approximately 52%.

[0036] Step 3: Preparation of the functionalized composite carrier (F-HPM): First, dissolve 0.5g SA-g-AA and 0.3g chitosan in 20mL of 2% acetic acid solution (containing 2g acetic acid per 100mL of solution). Then add 0.3g O-BC and disperse by ultrasonication. Finally, add 4mL of high-concentration PGPB bacterial suspension (5×10⁻⁶).9 (CFU / mL) Mix in an ice bath. Add the mixture dropwise to a coagulation bath (crosslinking bath) containing 0.1M CaCl2 and 1.0% (v / v) glutaraldehyde, and crosslink for 30 minutes. Collect the microspheres, wash with PBS, and freeze-dry.

[0037] Step 4: Granulation of integrated composite particles: Dry F-HPM microspheres, sodium percarbonate, and sodium bicarbonate-sodium citrate buffer (sodium bicarbonate to sodium citrate mass ratio of 4:1) are mixed at a mass ratio of 25:70:5. Using a 3% PVA solution (polyvinyl alcohol solution, containing 3 g PVA per 100 mL) as a binder, wet particles of 2.0-3.0 mm are granulated and dried in a fluidized bed at 40℃ to obtain composite particles for remediating polluted water bodies.

[0038] Figure 1 The diagram shows the structure of the composite particles prepared in Example 1 and the flowchart of the synergistic repair mechanism. Figure 1 It contains two parts. (A) is a schematic diagram of the composite particle structure, showing the SPC core and the functionalized composite carrier layer surrounding it; (B) is a flowchart of the synergistic mechanism, which is shown in three stages: ① SPC slow-release oxidation, carrier shrinkage protection; ② pH rise, carrier swelling; ③ PGPB release, biodegradation.

[0039] Example 2: Verification of acrylic acid grafting ratio.

[0040] The only difference from Example 1 is step 2: 2.2 mL of acrylic acid was added, and other conditions remained unchanged. The final grafting rate was approximately 32%.

[0041] Example 3: Verification of acrylic acid grafting ratio.

[0042] The only difference from Example 1 is step 2: 5.5 mL of acrylic acid was added, and other conditions remained unchanged. The final grafting rate was approximately 68%.

[0043] Example 4: Verification of glutaraldehyde crosslinking concentration.

[0044] The only difference from Example 1 is step 3: the volume concentration of glutaraldehyde in the crosslinking bath is 0.5%, while other conditions remain unchanged.

[0045] Example 5: Verification of glutaraldehyde crosslinking concentration.

[0046] The only difference from Example 1 is step 3: the volume concentration of glutaraldehyde in the crosslinking bath is 1.5%, while other conditions remain unchanged.

[0047] Example 6: Verification of the ratio of carrier to oxidant.

[0048] The only difference from Example 1 is step 4: F-HPM microspheres, sodium percarbonate, and buffer are mixed and granulated at a mass ratio of 15:80:5, while other conditions remain unchanged.

[0049] Example 7: Verification of the ratio of carrier to oxidant.

[0050] The only difference from Example 1 is step 4: F-HPM microspheres, sodium percarbonate, and buffer are mixed and granulated at a mass ratio of 30:65:5, while other conditions remain unchanged.

[0051] Comparative Example 1: Physical mixing and granulation of SPC with free PGPB bacterial powder.

[0052] The specific preparation steps are as follows:

[0053] Step 1, Preparation of mycelium powder:

[0054] Take 4 mL of high-concentration PGPB bacterial suspension (5×10 9 (CFU / mL, bacterial strain same as in Example 1), centrifuge to collect bacterial cells, wash with sterile physiological saline, freeze-dry, and grind to obtain PGPB freeze-dried bacterial powder.

[0055] Step 2, Physical mixing and granulation:

[0056] Weigh out 7.0 g of sodium percarbonate and the PGPB freeze-dried bacterial powder obtained in step 1 (equivalent to 2×10⁻⁶ g / kg). 10 The following ingredients were mixed thoroughly in a mortar: CFU (Cellular Fuel Cell Count) and sodium bicarbonate-sodium citrate buffer (mass ratio 4:1). A 3% PVA solution was added dropwise as a binder and stirred until a plastic wet material was formed. The wet material was extruded into wet granules with a particle size of 2.0–3.0 mm using a granulator, and then dried in a fluidized bed at 40°C to constant weight to obtain physically mixed remediation granules.

[0057] The mass ratio of each component is: sodium percarbonate : PGPB freeze-dried bacterial powder : buffer = 70 : 2.5 : 5. (Note: The bacterial powder mass is approximately 0.25 g based on the actual weight after freeze-drying. To ensure the same bacterial quantity as in Example 1, the actual bacterial powder mass is based on the weight after freeze-drying.)

[0058] Comparative Example 2: Using ordinary SA / CS (ungrafted) and biochar, crosslinking was performed only with 0.1M CaCl2, and the rest was the same as in the Example.

[0059] The specific preparation steps are as follows:

[0060] Step 1, Carrier Preparation: First, dissolve 0.5g of SA (sodium alginate) and 0.3g of chitosan in 20mL of 2% acetic acid solution. Then add 0.3g of biochar and disperse by ultrasonication. Next, add 4mL of high-concentration PGPB bacterial suspension (5×10⁻⁶). 9 (CFU / mL) and mix in an ice bath. Add the mixture dropwise to a cross-linking bath containing 0.1 M CaCl2 and cross-link for 30 minutes. Collect the microspheres, wash with PBS, and freeze-dry.

[0061] Step 2, Granulation: Dry microspheres, sodium percarbonate, and sodium bicarbonate-sodium citrate buffer (4:1) are mixed at a mass ratio of 25:70:5. Using 3% PVA solution as a binder, the mixture is granulated into 2.0-3.0 mm wet particles and dried in a fluidized bed at 40°C to obtain composite particles.

[0062] Comparative Example 3: SA / CS and O-BC were used, with crosslinking only using 0.1M CaCl2 (no grafting and glutaraldehyde), and the rest was the same as in Example 1.

[0063] The specific preparation steps are as follows:

[0064] Step 1, Carrier Preparation: First, dissolve 0.5g SA (sodium alginate) and 0.3g chitosan in 20mL of 2% acetic acid solution. Then add 0.3g O-BC and disperse by ultrasonication. Next, add 4mL of high-concentration PGPB bacterial suspension (5×10⁻⁶). 9 (CFU / mL) Mix in an ice bath. Add the mixture dropwise to a cross-linking bath containing 0.1 M CaCl2 and cross-link for 30 minutes. Collect the microspheres, wash with PBS, and freeze-dry.

[0065] Step 2, Granulation: Dry microspheres, sodium percarbonate, and sodium bicarbonate-sodium citrate buffer (4:1) are mixed at a mass ratio of 25:70:5. Using 3% PVA solution as a binder, the mixture is granulated into 2.0-3.0 mm wet particles and dried in a fluidized bed at 40°C to obtain composite particles.

[0066] The differences in key performance between the examples and the comparative examples were tested using the following methods:

[0067] (1) Mechanical strength test: Take an appropriate amount of freeze-dried functionalized composite carrier (F-HPM) microspheres, soak them in phosphate buffered saline (PBS, pH 7.0), and let them stand in a refrigerator at 4℃ for 12 hours to allow them to fully swell, thus obtaining wet gel microspheres. Use a micro universal testing machine to perform compression tests on a single intact wet gel microsphere at a constant loading rate (1 mm / min), and record the maximum force (N) that the microspheres can withstand before rupture, in order to characterize the wet mechanical strength of the carrier.

[0068] (2) Cell protection rate test: The final composite particle materials prepared by each example and comparative example containing an equal amount of PGPB (pre-calibrated by plate count method) were placed in an inorganic salt medium containing SPC (1 g / L) and incubated for 24 hours in a constant temperature shaker (e.g., 30°C, 150 rpm). Subsequently, the materials were recovered, and the viable colony forming units (CFU) were determined by the standard plate count method. The protection rate (viable CFU / initial CFU × 100%) was calculated by comparing with the initial dosage.

[0069] (3) Remediation Efficiency Test: A 500 mg / L phenol-simulated wastewater was prepared as the target pollutant system. The final composite particulate materials prepared in each example and comparative example were added to it to ensure that the equivalent SPC concentration in the system was 1 g / L. The reaction system was placed in a constant temperature shaker (e.g., 30°C, 120 rpm) for remediation reaction. Samples were taken at regular intervals, and the phenol concentration was analyzed by high performance liquid chromatography (HPLC) to calculate the degradation rate. After 72 hours of reaction, the total organic carbon (TOC) content was measured, and the TOC removal rate was calculated to evaluate the mineralization depth.

[0070] The test results are as follows:

[0071] Table 1 Summary of Experimental Data

[0072]

[0073] (1) Mechanical strength: The wet single-sphere compressive strength was tested using a miniature universal testing machine. In Example 1, F-HPM was approximately 0.25 N, and in Comparative Example 2, it was approximately 0.08 N.

[0074] (2) Cell protection rate: Each material containing an equal amount of cells was added to an inorganic salt medium containing SPC (1 g / L), shaken for 24 hours, and then recovered and counted. The protection rate of Example 1 was >95%, Comparative Example 2 was about 40%, and Comparative Example 3 was about 60%.

[0075] (3) Remediation efficacy: Each material (equivalent to 1 g / L SPC) was added to 500 mg / L phenol simulated wastewater and monitored for 72 hours. Figure 2 This is a comparison graph showing the change of phenol concentration over time during the repair process between Example 1 and each comparative example. Figure 3 The bar chart shows the total organic carbon (TOC) removal rates of Example 1 and the comparative examples after 72 hours of remediation. In Example 1, the phenol degradation rate was >99%, and the TOC removal rate was 85%; in Comparative Example 1, the degradation rate was approximately 70% (stagnating after 24 hours), and the TOC removal rate was approximately 40%; in Comparative Example 2, the degradation rate was approximately 90%, and the TOC removal rate was approximately 65%; and in Comparative Example 3, the degradation rate was approximately 94%, and the TOC removal rate was approximately 72%.

[0076] The data above clearly demonstrate that this dual chemical modification strategy has brought about a qualitative improvement in key performance indicators.

[0077] This invention utilizes a dual chemical modification process—acrylic acid grafting and glutaraldehyde crosslinking—to transform a sodium alginate / chitosan@biochar carrier into a high-strength, pH-responsive smart carrier for immobilizing plant growth promoters (PGPB), which is then granulated with sodium percarbonate (SPC). After addition, this carrier effectively resists the initial oxidative shock of SPC, protecting bacterial activity, and intelligently releases PGPB in response to pH changes, precisely connecting and deepening the oxidative degradation process to achieve efficient and deep mineralization of pollutants. Experiments show that this material achieves a microbial protection rate of over 95% and a 72-hour phenol mineralization rate (TOC removal) of 85%, significantly superior to traditional methods. This invention solves the compatibility problem between oxidants and microorganisms, providing a new technology for efficient and green water remediation.

[0078] As described above, although the invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the invention itself. Various changes in form and detail may be made without departing from the spirit and scope of the invention.

Claims

1. A method for preparing composite particles for remediating polluted water bodies, characterized in that, Includes the following steps: S1. The biochar is subjected to acid oxidation treatment to obtain oxidized biochar; S2. Sodium alginate and acrylic acid are graft copolymerized under the action of an initiator to obtain carboxylated sodium alginate. S3. Oxidized biochar, carboxylated sodium alginate, chitosan and plant growth-promoting bacteria solution are mixed and added dropwise into a cross-linking bath containing calcium ions and glutaraldehyde to solidify and form gel microspheres. After post-treatment, functionalized composite carriers are obtained. S4. The dried functionalized composite carrier microspheres are mixed with sodium percarbonate and pH buffer and granulated to obtain composite particles.

2. The preparation method according to claim 1, characterized in that, The specific operation of S1 is as follows: Biochar powder was added to a mixture of concentrated nitric acid and concentrated sulfuric acid and refluxed at 70°C for 5 hours; washed until neutral and dried at 105°C to obtain oxidized biochar. The volume ratio of concentrated nitric acid to concentrated sulfuric acid is 3:

1.

3. The preparation method according to claim 1, characterized in that, The specific operation of S2 is as follows: Sodium alginate was dissolved in water, then acrylic acid was added, nitrogen gas was passed through, potassium persulfate was added, and the reaction was carried out at 65°C for 4 hours. The product was precipitated and washed with ethanol and freeze-dried to obtain carboxylated sodium alginate. The ratio of sodium alginate, acrylic acid, water, and potassium sulfate used is 2g:(2.2-5.5)mL:98mL:0.03g.

4. The preparation method according to claim 1, characterized in that, The specific operation of S3 is as follows: First, carboxylated sodium alginate and chitosan were dissolved in acetic acid solution, then oxidized biochar was added and ultrasonically dispersed; then plant growth-promoting bacteria suspension was added and mixed in an ice bath; the mixture was dropped into a cross-linking bath containing CaCl2 and glutaraldehyde, cross-linked for a period of time, the microspheres were collected, washed with PBS and freeze-dried to obtain the functionalized composite carrier. The volume concentration of glutaraldehyde in the crosslinking bath was 0.5%-1.5%; the concentration of CaCl2 was 0.1M.

5. The preparation method according to claim 1, characterized in that, The specific operation of S4 is as follows: The dried functionalized composite carrier, sodium percarbonate, and sodium bicarbonate-sodium citrate buffer were mixed and granulated into 2.0-3.0 mm wet particles using 3% PVA solution as a binder. The particles were then dried in a fluidized bed at 40°C to obtain composite particles for remediating polluted water bodies. The mass ratio of the functionalized composite carrier, sodium percarbonate, and sodium bicarbonate-sodium citrate buffer is (15-30):(60-80):5; in the sodium bicarbonate-sodium citrate buffer, the mass ratio of sodium bicarbonate to sodium citrate is 4:

1.

6. Composite particles prepared by any of the preparation methods described in claims 1-5.

7. The composite particles prepared according to claim 6, characterized in that, The composite particles have a particle size of 1.5~3.0 mm, wherein the functionalized composite carrier microspheres account for 15%~30% of the total mass of the particles, sodium percarbonate accounts for 60%~80%, and the remainder is a pH buffer.

8. The application of the composite particles according to claim 6 in the preparation of remediation agents for water bodies contaminated by phenolic compounds, petroleum hydrocarbons or polycyclic aromatic hydrocarbons.

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