A pH-responsive slow-release bacteriostatic agent for inhibiting generation of acid mine drainage in situ and a preparation method thereof

Abstract

The application discloses a pH-responsive slow-release bacteriostatic agent for in-situ inhibition of generation of acid mine drainage and a preparation method thereof, and belongs to the technical field of mine pollution remediation. The preparation raw materials are selected to include sorbic acid (SA), amino-modified mesoporous silica (NH2-MSN) and polyacrylic resin IV (PAR). The sorbic acid in the bacteriostatic agent has good bacteriostatic efficiency, and the amino-modified mesoporous silica is used as a slow-release material to improve the persistence and stability of the bacteriostatic efficiency. The polyacrylic resin IV is used as an outer blocking molecule, and has excellent pH response properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of mine pollution remediation, and specifically relates to an in-situ treatment method for acidic mine wastewater, a pH-responsive slow-release antibacterial agent for in-situ inhibiting the generation of acidic mine wastewater, and a preparation method thereof. Background Art

[0002] my country is rich in metal mineral resources. With frequent energy crises and the increasing importance of energy, my country has continuously intensified its efforts to develop existing mineral resources, triggering a series of serious ecological and environmental problems. Mining operations generate large amounts of tailings and abandoned mines. Acid mine drainage (AMD) is formed when metal sulfides (such as pyrite) in tailings or abandoned mines are catalytically oxidized by air, water, and microorganisms, resulting in low-pH, high-concentration heavy metals and sulfates.

[0003] Current AMD control technologies fall into two main categories: end-of-pipe control and source control. Source control analyzes the pathways of AMD production and inhibits its formation by blocking oxygen, passivating minerals, and suppressing the activity of acid-producing microorganisms. These methods primarily include covering, neutralization, and antibacterial methods.

[0004] Bacteriostatic treatment is one of the most commonly used methods for source control of acid mine drainage, due to its ease of use, low cost, and economical nature. However, in actual engineering applications, antibacterial agents are susceptible to loss or degradation due to fluctuating environmental and climatic conditions. To ensure long-term stability, large quantities of these agents must be used, which can lead to the development of resistance genes and low utilization rates. Furthermore, current research on antibacterial agents primarily focuses on their preparation and performance, without considering their responsiveness to environmental conditions. Summary of the Invention

[0005] Based on the analysis of the promoting effect of microorganisms on the oxidative dissolution of pyrite and the key influencing factors, the present invention selected sorbic acid (SA), amino-modified mesoporous silica (NH2-MSN), and polyacrylic resin IV (PAR) as an antibacterial agent, a sustained-release material, and an outer-layer blocking molecule, respectively, and optimized the preparation of a new pH-responsive sustained-release antibacterial agent. Release kinetics studies were carried out to reveal the sustained-release mechanism, providing a theoretical basis and technical support for the practical application of pH-responsive antibacterial agents in the treatment of acidic mine drainage.

[0006] One of the objects of the present invention is to provide an in-situ treatment method for acid mine drainage.

[0007] A second object of the present invention is to provide a pH-responsive slow-release antibacterial agent for in-situ treatment of acidic mine wastewater.

[0008] The third object of the present application is to provide a preparation method of a pH-responsive slow-release bacteriostatic agent for in-situ treatment of acid mine drainage.

[0009] In order to achieve the above-mentioned objects of the present application, the following technical solutions are adopted:

[0010] The present application analyzes the key influencing factors of A.f bacteria in oxidizing and dissolving pyrite, and finds that the change of pH value can significantly affect the oxidation and dissolution of pyrite by A.f bacteria. With the decrease of pH value, the growth activity of microorganisms is better, the promotion effect of oxidation and dissolution of pyrite is greater, and the oxidation rate of pyrite is higher. Therefore, a special pH-responsive slow-release bacteriostatic agent is designed, which can release and play a role through the change of environmental pH value to achieve long-term regulation and reduction of the promotion effect of microorganisms on the oxidation and dissolution of pyrite.

[0011] In a first aspect, the present application provides an in-situ treatment method of acid mine drainage, comprising:

[0012] A new type of pH-responsive slow-release bacteriostatic agent is prepared, which can inhibit the biological oxidation of pyrite for a long time by using the pH-responsive slow-release bacteriostatic agent to reduce acid mine drainage from the source;

[0013] The preparation method of the pH-responsive slow-release bacteriostatic agent comprises the following steps:

[0014] (1) Preparation of mesoporous silica nanomaterials: dissolve the template agent in water, heat and magnetically stir to obtain a mixed solution; add the silicon source dropwise to the mixed solution for stirring reaction, centrifugation, and dry and calcine the obtained solid product to obtain mesoporous silica nanomaterials (MSN);

[0015] (2) Preparation of amino-modified mesoporous silica nanomaterials: the mesoporous silica nanomaterials are modified by post-grafting method, washed with ultrapure water and ethanol, and dried to obtain amino-modified mesoporous silica nanomaterials (NH2-MSN);

[0016] (3) The sorbic acid (SA) is loaded in the amino-modified mesoporous silica nanomaterials by impregnation method to obtain the bacteriostatic material (NH2-MSN@SA);

[0017] (4) The polyacrylic resin IV (PAR) is added to ethanol to completely dissolve, then magnesium stearate is added, and the pH-responsive slow-release bacteriostatic agent (PAR / NH2-MSN@SA) is prepared by solvent evaporation method.

[0018] In some embodiments, the template agent in step (1) is one or more of cetyltrimethylammonium bromide or cetyltrimethylammonium chloride, preferably cetyltrimethylammonium bromide (CTAB).

[0019] In some embodiments, the silicon source in step (1) is one or more of tetraethyl orthosilicate, propyl orthosilicate, or butyl orthosilicate, preferably tetraethyl orthosilicate (TEOS).

[0020] In some embodiments, the calcination temperature in step (1) is 500-600° C., and the calcination time is 4-6 hours.

[0021] In some embodiments, step (1) specifically includes:

[0022] 1.0 g of hexadecyltrimethylammonium bromide was dissolved in 480 mL of ultrapure water, added to 3.5 mL of 2M sodium hydroxide solution, mixed well, and then heated to 80°C and magnetically stirred for 10 minutes; 5.00 mL of ethyl orthosilicate was added dropwise to the mixed solution and stirred for 2 hours. After a white precipitate appeared, the mixture was centrifuged at 5000 r / min for 5 minutes; the obtained lower layer solid product was washed three times with ultrapure water and ethanol in sequence, dried at 60°C for 12 hours, and then calcined at 550°C for 5 hours to obtain mesoporous silica nanomaterials.

[0023] In some embodiments, step (2) comprises the following steps:

[0024] The mesoporous silica nanomaterial obtained in step (1) is dispersed in water, acetic acid and 3-aminopropyltriethoxysilane (APTS) are added, stirred at room temperature, centrifuged, and the lower layer of solid product is removed, washed, and dried to obtain the amino-modified mesoporous silica nanomaterial.

[0025] In some embodiments, step (2) specifically includes:

[0026] 500 mg of the mesoporous silica nanomaterial prepared in step (1) was dispersed in 50 mL of ultrapure water, 300 μL of acetic acid was added, 200 μL of 3-aminopropyltriethoxysilane (APTS) was added, stirred at room temperature for 24 h, and centrifuged at 5000 r / min for 5 min; the lower layer of solid product was removed and washed three times with ultrapure water and ethanol in sequence, and dried in vacuum at 60°C to obtain amino-modified mesoporous silica nanomaterial.

[0027] In some embodiments, step (3) comprises the following steps:

[0028] The amino-modified mesoporous silica nanomaterial obtained in step (2) is ultrasonically dispersed in a sorbic acid solution, placed in a constant temperature shaker for oscillation to saturate the nanomaterial with adsorption, filtered, washed, and dried to obtain an antibacterial material.

[0029] In some embodiments, step (3) specifically includes:

[0030] Take 50 mg of NH2-MSN prepared in step (2) and ultrasonically disperse it in 30 mL of 3-5 g / L SA solution, adjust the pH to 5, place it in a constant temperature shaker at 30°C and oscillate for 40-48 h to saturate the nanomaterial adsorption, filter, wash, and dry to obtain SA-loaded NH2-MSN, which is recorded as NH2-MSN@SA.

[0031] In some embodiments, step (4) comprises the following steps:

[0032] Polyacrylic acid resin IV is dissolved in ethanol, and then magnesium stearate is added (to slow down the dissolution rate of the core material from the microspheres and avoid sudden release) to obtain an ethanol mixed solution; then an antibacterial material is added to form a mixed emulsion; the mixed emulsion is added to the PVA solution, and the solid product is washed and dried to obtain a pH-responsive sustained-release antibacterial agent.

[0033] In some embodiments, step (4) specifically includes:

[0034] 3.0 g of polyacrylic acid resin IV was weighed and dissolved in 200 mL of ethanol, and then 2.0 g of magnesium stearate was added to obtain an ethanol mixed solution;

[0035] Weigh 2.0 g of the antibacterial material and ultrasonically disperse it in 100 mL of ultrapure water. Add it to the above ethanol mixed solution and continue stirring to form a mixed emulsion.

[0036] Weigh 3.0 g of polyvinyl alcohol (PVA) (emulsifier, which makes the material form microspheres) and pour it into 200 mL of deionized water. Heat and stir to completely dissolve it. Cool it to room temperature and adjust the pH of the solution to 10.0 to obtain a PVA solution.

[0037] The mixed emulsion was added dropwise to the PVA solution, stirred continuously at medium to high speed at room temperature and then centrifuged. The solid product was washed with deionized water and n-hexane and dried to obtain a pH-responsive sustained-release antibacterial agent.

[0038] In a second aspect, the present invention provides a pH-responsive slow-release antibacterial agent for in-situ inhibition of the generation of acidic mine wastewater, which is prepared by the above-mentioned preparation method.

[0039] The preparation method of the pH-responsive sustained-release antibacterial agent comprises the following steps:

[0040] (1) Preparation of mesoporous silica nanomaterials: dissolving a template in water, heating and magnetically stirring to obtain a mixed solution; adding a silicon source dropwise to the mixed solution, stirring and reacting, centrifuging, and drying and calcining the obtained solid product to obtain a mesoporous silica nanomaterial (MSN);

[0041] (2) Preparation of amino-modified mesoporous silica nanomaterials: The mesoporous silica nanomaterials obtained in step (1) were dispersed in water, acetic acid and 3-aminopropyltriethoxysilane (APTS) were added, stirred at room temperature, centrifuged, and the lower solid product was removed, washed, and dried to obtain the amino-modified mesoporous silica nanomaterials;

[0042] (3) ultrasonically dispersing the amino-modified mesoporous silica nanomaterial obtained in step (2) in a sorbic acid solution, placing the solution in a constant temperature shaker to oscillate the nanomaterial to saturate adsorption, filtering, washing, and drying the solution to obtain an antibacterial material;

[0043] (4) Dissolving polyacrylic acid resin IV in ethanol, and then adding magnesium stearate to obtain an ethanol mixed solution; then adding an antibacterial material to form a mixed emulsion; adding the mixed emulsion to the PVA solution, washing and drying the solid product to obtain a pH-responsive sustained-release antibacterial agent.

[0044] In a third aspect, the present invention provides a method for preparing a pH-responsive slow-release antibacterial agent for in situ inhibition of the generation of acidic mine wastewater.

[0045] The specific contents of the second and third aspects are the same as those of the first aspect and will not be repeated here.

[0046] Beneficial effects:

[0047] The present invention uses SA as an antibacterial agent, NH2-MSN as a slow-release material, and PAR as an outer blocking molecule to prepare a pH-responsive slow-release antibacterial agent. The slow-release effect has good responsiveness to the environmental pH, and the pH-responsive slow-release antibacterial agent can inhibit the biological oxidation of pyrite for a long time.

[0048] In the present invention, MSN is modified by amino modification through a post-grafting method to obtain NH2-MSN, so that its surface carries a positive charge in a neutral or acidic environment, thereby improving the stability of the antibacterial material and enhancing the adhesion of the antibacterial material.

[0049] Given the acidic pH of acid mine drainage, SA, which exhibits excellent antibacterial properties under acidic conditions and is low-cost, was selected as the loading agent. Since modified MSN carries a positive charge due to the -NH2 residue, it interacts better with the negatively charged carboxyl groups of SA through electrostatic adsorption and molecular diffusion, allowing SA to be adsorbed onto the surface and interior of the NH2-MSN.

[0050] PAR, whose acidic responsiveness range matches the pH of typical acidic mine wastewater, was selected as the plugging material. The surface charge of NH2-MSN loaded with SA is negative, and the positively charged tertiary amino groups of PAR are able to better encapsulate NH2-MSN@SA. The pH responsiveness of PAR / NH2-MSN@SA is primarily due to the lone pair of electrons on the nitrogen atom of the tertiary amino group in the PAR molecular chain. Under slightly acidic conditions (pH < 5), it undergoes protonation, enhancing its solubility. At higher pH, the PAR molecular chains curl up, encapsulating the SA-loaded NH2-MSN and blocking the surface mesoporous structure, preventing the release of SA.

[0051] When the pH-responsive slow-release antibacterial agent is applied to acid mine drainage, in the early stage of AMD, when the pH value is high (pH>5) and there is no microorganism such as Af bacteria to promote the oxidation and dissolution of sulfide minerals, the pH-responsive encapsulating material PAR swells and still encapsulates NH2-MSN@SA, and SA will not be released from NH2-MSN. Under the promotion of oxidation and dissolution of microorganisms such as Af bacteria, a large amount of H + 、Fe 3+ and SO4 2- etc., which rapidly reduces the pH value of AMD. When the pH value is low, the slow-release antibacterial agent begins to respond to the change of pH value and release. At this time, H + The concentration is high, so that the tertiary amino groups on the PAR structure are positively charged, and there is repulsion between the molecules. The PAR molecular chain stretches out, and water molecules gradually enter the PAR. At this time, the PAR slowly dissolves and SA begins to slowly release. And H + The higher the concentration, the faster PAR dissolves and the more SA is released, which in turn inhibits the growth activity of microorganisms such as Af bacteria and reduces the promoting effect on the oxidative dissolution of sulfide minerals.

[0052] The microspheres have good thermal stability, and in actual application, the sustained-release antibacterial agent will not be destroyed by changes in ambient temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 Fe at different SA inhibitor concentrations 2+ Concentration change graph;

[0054] Figure 2 Fe at 96h under different SA antibacterial agent concentrations 2+ Concentration and oxidation inhibition rate change diagram;

[0055] Figure 3 The adsorption diagram of SA by NH2-MSN under different APTS modification conditions;

[0056] Figure 4 Figure 2 is the SA adsorption diagram at different concentrations;

[0057] Figure 5 Figure for the effect of material ratio on SA adsorption amount;

[0058] Figure 6 Figure for the effect of initial pH on adsorption amount;

[0059] Figure 7 Figure for the release performance of pH-responsive slow-release bacteriostatic agent at different pH (oscillation);

[0060] Figure 8 Figure for the release performance of pH-responsive slow-release bacteriostatic agent at different pH (non-oscillation);

[0061] Figure 9 Figure for the release rate of pH-responsive slow-release bacteriostatic agent at different pH;

[0062] Figure 10 Figure for the release kinetics fitting curve of pH-responsive slow-release bacteriostatic agent (zero-order release kinetics);

[0063] Figure 11 Figure for the release kinetics fitting curve of pH-responsive slow-release bacteriostatic agent (first-order release kinetics);

[0064] Figure 12 Figure for the release kinetics fitting curve of pH-responsive slow-release bacteriostatic agent (Higuchi model);

[0065] Figure 13 Figure for the release kinetics fitting curve of pH-responsive slow-release bacteriostatic agent (Korsmeyer-Peppas model);

[0066] Figure 14 Figure for the simulation experiment device;

[0067] Figure 15 Figure for the change of leaching solution pH and ORP;

[0068] Figure 16 Figure for the change of total iron ion and sulfate ion concentration in leaching solution. DETAILED DESCRIPTION

[0069] Hereinafter, the present application will be further described in conjunction with specific embodiments. It should be noted that, under the premise of no conflict, each embodiment described below or each technical feature can be combined with any other embodiment or technical feature to form a new embodiment. Obviously, the described embodiments are part of, but not all of the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0070] Unless otherwise specified in the examples, the specific conditions were carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used were conventional products obtained through commercial channels, unless otherwise specified.

[0071]

[0072]

[0073] The pyrite samples used in the examples were all taken from the abandoned mine of Dashu mining area in Xuyong County, Luzhou, Sichuan Province. The raw ore was crushed with a hammer, and the mineral impurities were removed. Then the sample was further crushed with a ball mill, and finally ground with an agate mortar and sieved through a 200 mesh screen.

[0074] The ground pyrite powder was pretreated according to the following steps:

[0075] (1) The pyrite powder was ultrasonically cleaned in 6 mol / L HCl solution for 3 times to remove some inorganic impurities that can be dissolved by acid;

[0076] (2) Ultrasonic cleaning with anhydrous ethanol for 3 times to remove some water-insoluble oxidation products such as SO4 on the surface of pyrite formed during grinding;

[0077] (3) Cleaning in anaerobic ultrapure water for 3 times to remove residual HCl and some inorganic salt ions generated during cleaning;

[0078] (4) Vacuum drying at 50°C and sealing for storage before use.

[0079] The AMD stock solution water used in the examples was collected from the abandoned mine water of Dashu mining area in Xuyong County, Luzhou, Sichuan Province.

[0080] The Acidithiobacillus ferrooxidans used in the examples was purchased from the China General Microbiological Culture Collection Center (CGMCC), with strain number 1.6359.

[0081] The determination methods of pH, ORP, total iron ion concentration and sulfate ion concentration involved in the following examples are as follows:

[0082] pH was determined by "Determination of pH value of water electrode method" (HJ 1147-2020);

[0083] ORP was determined by "Determination of oxidation-reduction potential by potential measurement method" (SL 94-1994);

[0084] Total iron ion concentration was determined by "O-phenanthroline spectrophotometric method (trial)" (HJ / T 345-2007);

[0085] Sulfate ion was determined using the Barium Chromate Spectrophotometric Method (Trial) (HJ / T 342-2007).

[0086] The SA determination method in the embodiment is as follows:

[0087] Place 1 mL of the test solution in a 25 mL stoppered colorimetric tube. Add 5 mL of water, then 1 mL of 0.5% potassium dichromate solution and 1 mL of 0.15 mol / L sulfuric acid, and shake well. Heat in a boiling water bath for 5 minutes. Add 2 mL of 0.5% thiobarbituric acid solution and shake well. Heat in a boiling water bath for another 10 minutes. Remove the tube and quickly cool it with cold water. Add water to the mark and shake well. Measure the absorbance at 530 nm using a 1 cm cuvette with the blank solution as a reference. Calculate the SA content using the standard curve.

[0088] Example 1: Determination of Minimum Inhibitory Concentration

[0089] SA antibacterial solutions with concentrations of 0.1, 1, 5, 10, 20, and 50 mg / L were prepared, and no antibacterial agent was added to the blank group (CK). 50 mL of sterilized 9K culture medium, 30 mL of filter-sterilized 44.7 g / L ferrous sulfate heptahydrate solution (containing 9 g / L FeCl2) were added to a 250 mL sterilized conical flask. 2+ ), add 10% Af bacterial solution, and then add 10mL of SA antibacterial solution of different concentrations (0.1, 1, 5, 10, 20, 50mg / L) into the bottle respectively, with 3 parallels in each group. The control group was filled up to 100mL with 9K culture medium, sealed with sealing film, and cultured at 30℃ and 150r / min constant temperature shaking. Samples were taken regularly to determine the Fe 2+ Concentration, calculate Fe 2+ The minimum addition concentration of SA was determined by the oxidation inhibition rate.

[0090] Fe of Af bacteria under the treatment of SA inhibitor at concentrations of 0.1, 1, 5, 10, 20, and 50 mg / L 2+ The change of concentration Figure 1 As shown. 2+ The initial concentration of Fe was 9 g / L. When no SA treatment was added and the SA concentration was 0.5 and 1 mg / L, Fe 2+ The oxidation speed is fast and is basically complete in about 96 hours. When the SA concentration is 5 mg / L, Fe 2+ The concentration was 5.46 g / L, indicating that SA inhibited the activity of some Af bacteria and slowed down the growth of Fe 2+ When the SA concentration is greater than or equal to 10 mg / L, Fe 2+ Oxidation was very slow, with less than 10% of Fe 2+The results showed that after adding SA at a concentration of 10 mg / L or more, the growth activity of Af bacteria could be effectively inhibited, and the Fe 2+ oxidation.

[0091] The inhibitory effect of antibacterial agents on Af bacteria is generally measured by Fe 2+ It is expressed as the concentration change. That is: I = (AB) / C. Where I is the inhibition rate; A is the Fe after treatment with the antibacterial agent. 2+ concentration; B is the blank control Fe 2+ concentration; C is the initial Fe 2+ Concentration. Figure 2 It can be seen that when the experiment was carried out for 96 hours, the Fe 2+ The concentration dropped from the initial 9.0 g / L to 0, and the solution was observed to change from the initial light green to reddish brown, and a large amount of yellow precipitate was produced, indicating that the Af bacteria grew rapidly and converted Fe 2+ All oxidized to Fe 3+ , and yellow jarosite precipitate was generated. In the treatment with SA antibacterial agent concentration greater than or equal to 5 mg / L, Fe 2+ The concentration has always maintained a high value, indicating that SA can effectively kill or inhibit the activity of Af bacteria and thus slow down the growth of Fe 2+ When the concentration of SA reaches a certain value, as the concentration of SA increases, its effect on Fe 2+ The oxidation inhibition rate of Fe 2+ The oxidation inhibition rate of Fe 2+ The oxidation inhibition rate of Fe 2+ The results showed that after adding SA at a concentration of 10 mg / L or more, the activity and growth of Af bacteria could be effectively inhibited, and the oxidation inhibition rate of Fe could be reduced. 2+ oxidation.

[0092] Preparation Example: Preparation of pH-responsive sustained-release antibacterial agent

[0093] (1) Preparation of amino-modified mesoporous SiO2 nanomaterials (NH2-MSN):

[0094] Dissolve 1.0g of hexadecyltrimethylammonium bromide (CTAB) in 480mL of ultrapure water, add 3.5mL of 2M NaOH solution, mix well, and heat the mixture to 80°C with magnetic stirring for 10min. Add 5.00mL of tetraethyl orthosilicate (tetraethyl silicate) dropwise to the mixture and stir for 2h. After a white precipitate appears, centrifuge at 5000r / min for 5min, discard the supernatant, and wash the lower solid product with ultrapure water and ethanol three times in sequence. Place it under vacuum and dry it at 60°C for 12h to obtain CTAB-MSN. Finally, calcinate it in a muffle furnace at 550°C for 5h to remove the template CTAB in the mesopores, thus obtaining MSN.

[0095] 500mg of MSN was dispersed in 50mL of ultrapure water, 300μL of acetic acid was added, and 0, 100, 250, 500, and 1000μL APTS were added, respectively. After stirring at room temperature for 24h, the mixture was centrifuged at 5000r / min for 5min, the supernatant was discarded, and the lower solid product was washed three times with ultrapure water and ethanol in sequence. The solid product was then placed in a vacuum dryer at 60°C to obtain amino-modified mesoporous SiO2 nanomaterials (NH2-MSN). The effect of different APTS addition amounts (0, 100, 250, 500, and 1000μL) on the loading of sorbic acid on NH2-MSN was investigated.

[0096] (2) Preparation of sustained-release antibacterial agent:

[0097] 50 mg of NH2-MSN was ultrasonically dispersed in 30 mL of 3 g / L SA solution, the pH was adjusted to 5, and the solution was placed in a constant temperature shaker at 30 °C and shaken for 40 h to saturate the adsorption of NH2-MSN nanomaterials. The solution was then filtered, washed, and dried to obtain NH2-MSN loaded with SA, which was designated as NH2-MSN@SA.

[0098] (3) Preparation of PAR / NH2-MSN@SA:

[0099] 3.0 g of PAR was weighed and added to a beaker containing 200 mL of ethanol. Ultrasonication was performed for 30 minutes to completely dissolve the solution, followed by the addition of 2.0 g of magnesium stearate. 2.0 g of the prepared sustained-release antibacterial agent, NH2-MSN@SA, was ultrasonically dispersed in 100 mL of ultrapure water. This solution was then added to the ethanol mixture and stirred continuously to form a mixed emulsion. 3.0 g of polyvinyl alcohol (PVA) was poured into a beaker containing 200 mL of deionized water. Heat and stirring were performed to completely dissolve the solution. The solution was cooled to room temperature and the pH of the solution was adjusted to 10.0 to ensure that the PAR-coated NH2-MSN@SA had no holes. The mixed emulsion was then added dropwise to the PVA solution with continuous stirring at medium-high speed at room temperature to evaporate the organic solvent. After standing, the solution was centrifuged. The solid product was washed with appropriate amounts of deionized water and n-hexane and dried to obtain PAR / NH2-MSN@SA microspheres.

[0100] Example 2: Effect of APTS addition on NH2-MSN loading SA

[0101] 0, 100, 200, 500, and 1000 μL of APTS were added to modify MSNs by amino groups to explore the effect of different APTS addition amounts on the loading of SA on NH2-MSNs. Figure 3 As shown in the figure, compared with unmodified MSNs, the adsorption of SA by MSNs modified with APTS after amination was significantly improved. This is attributed to the interaction between the positive surface charge of the NH2-MSNs after amination and the negative surface charge of SA. The increased positively charged groups on the MSN surface after amination create an electrostatic adsorption effect with the negatively charged groups on the SA surface. Adding excessive amounts of APTS did not significantly increase the adsorption of SA by MSNs. When 200 μL of APTS was added, the adsorption of SA was optimal, reaching approximately 180.74 mg / g. These results indicate that the adsorption of SA by MSNs after amination is more effective, and the adsorption of SA is even more ideal when 200 μL of APTS is added.

[0102] Example 3: Effect of initial SA concentration on the loading amount of pH-responsive sustained-release antibacterial agent

[0103] A certain amount of SA was weighed and dissolved in an ultrapure water / ethanol mixture to a volume of 100 mL. A certain amount of NH₂-MSN and 30 mL of SA solution were added to a 50 mL centrifuge tube at a mass ratio of SA:NH₂-MSN of 2:1. The tube was sealed and placed horizontally in a thermostatic oscillator at 30°C and 150 rpm for 60 hours. The filtrate was collected by filtration and the loading capacity was determined. The SA concentrations used were 1, 3, 5, 7, and 9 g / L, with triplicate replicates for each group.

[0104] The research results are as follows Figure 4 As shown in the figure, when the initial SA concentration is 1 and 3 g / L, the SA adsorbed by NH2-MSN is approximately 164.21 and 191.69 mg / g, respectively. When the initial SA concentration is 5-9 g / L, NH2-MSN adsorbs more SA, which is about 251.94-264.72 mg / g. When the initial concentration is 7 and 9 g / L, the amount of adsorbed SA increases very little. This is because NH2-MSN will experience adsorption equilibrium in the process of adsorbing SA antibacterial agent molecules. Within a certain concentration range, the higher the concentration of SA solution, the more conducive it is for SA molecules to enter the pores and interior of NH2-MSN. Therefore, appropriately increasing the SA concentration can greatly increase the SA loading capacity. Based on cost savings, the initial concentration is set to 5 g / L.

[0105] Example 4: Effect of feed ratio on loading amount of pH-responsive sustained-release antibacterial agent

[0106] Accurately weigh 5g of SA and dissolve it in an ultrapure water / ethanol mixture to 1L. Add a predetermined amount of NH2-MSN and 30mL of SA solution to a 50mL centrifuge tube. Seal the tube and place it horizontally in a thermostatic oscillator at 30°C and 150 rpm for 60 hours. Filter and collect the filtrate for loading determination. The SA:SiO2 input mass ratios were 2:1, 1:1, and 1:2, respectively, and three replicates were performed for each group.

[0107] The results are as follows Figure 5 As shown in the figure, the SA loading capacity of the carrier material increases with the proportion of NH2-MSN input. When the mass ratio of SA to NH2-MSN input is 2:1, the SA loading per unit mass of NH2-MSN is the highest, approximately 254 mg / g. This is likely due to the relatively fixed specific surface area, pore size, and pore volume of NH2-MSN, which has a certain loading capacity for SA molecules. When the SA loading of NH2-MSN exceeds its own drug-loading capacity, the loading capacity decreases with increasing NH2-MSN input.

[0108] Example 5: Effect of Solution pH on the Loading Amount of pH-Response Slow-Release Antibacterial Agents

[0109] Accurately weigh 5g of SA and dissolve it in an ultrapure water / ethanol mixture. The volume was adjusted to 1L. In a 50mL centrifuge tube, 75mg of NH2-MSN and 30mL of SA solution were added. The pH values ​​were adjusted to 2, 5, and 8, respectively. Three replicates were run in each group. After sealing, the centrifuge tube was placed horizontally in a thermostatic oscillator at 30°C and 150 rpm for 60 hours. The filtrate was collected by filtration and the loading capacity was determined.

[0110] The experimental results of the study are as follows Figure 6 As shown. The results show that compared with solution pH 2 or 8, pH 5 is more conducive to the adsorption of SA by NH2-MSN, at which point the adsorption amount is around 268.37 mg / g. Lower or higher solution pH is not conducive to the adsorption of SA by NH2-MSN. Solution pH not only affects the surface potential and the state of surface groups of NH2-MSN, but also the molecular structure of SA. SA solution contains slightly acidic functional groups such as carboxyl groups, which are protonated at low pH, causing SA to aggregate and precipitate. As the pH continues to increase, the adsorption amount first increases and then decreases. When the solution pH increases, the carboxyl groups are deprotonated, causing SA to carry a negative charge, which will repel each other. At the same time, the alkaline environment may affect the structure of NH2-MSN.

[0111] Example 6: Effect of loading time on the loading amount of pH-responsive sustained-release antibacterial agent

[0112] Accurately weigh 5g of SA and dissolve it in an ultrapure water / ethanol mixture. The volume was then adjusted to 1L. 75mg of NH2-MSN and 30mL of SA solution were then added to a 50mL centrifuge tube. After sealing, the centrifuge tube was placed horizontally in a thermostatic oscillator at 30°C and 150 rpm for a specified period of time. The filtrate was collected by filtration and the loading capacity was determined. Oscillation times of 12, 24, 36, 48, and 60 hours were used to determine the adsorption saturation time of NH2-MSN on SA.

[0113] Adsorption of SA by NH2-MSN at different initial SA concentrations, feed ratios, and solution pH values ​​revealed that SA adsorption by NH2-MSN reached equilibrium around 48 hours. When the initial SA concentration was 5 g / L, the SA to NH2-MSN addition ratio was 2:1, the solution pH was 5, and the loading time was 48 hours, NH2-MSN adsorbed the maximum SA antibacterial agent, with an adsorption capacity of approximately 268.37 mg / g and a loading rate of 16.76%.

[0114] Example 7: Release performance of pH-responsive sustained-release antibacterial agent at different pH

[0115] 50 mg of dried PAR / NH2-MSN@SA was weighed and added to a 14,000 molecular weight dialysis bag with a 15 cm cutoff. 5 mL of aqueous solutions with different pH values ​​(1, 5, 3, 5, and 7) were then added. After clamping both ends, the bag was added to 100 mL of aqueous solutions with the corresponding pH values. The bag was then shaken at a constant temperature of 30°C for 7 days for sustained release (one group was shaken and the other group was not shaken). Samples were taken at regular intervals and replenished with aqueous solutions of the corresponding pH values. The absorbance of SA was measured by UV spectrophotometry, and the cumulative release rate (Ri) of the SA antibacterial agent was calculated at different times.

[0116] The release behavior of PAR / NH2-MSN@SA in aqueous solutions with different pH values ​​was analyzed by release experiments, and the cumulative release rate of SA antibacterial agent within 7 days was calculated. Figure 7 and Figure 8 As shown. In a neutral environment, the release rate of the SA antibacterial agent is very slow, and the cumulative release rate over 7 days is only about 17.45%. This is because the NH2-MSN@SA microspheres wrapped with PAR are in a swollen state, and PAR blocks most of the mesoporous structure of NH2-MSN, resulting in a relatively slow release of SA. In an acidic environment, due to the protonation of the tertiary amine groups in the PAR molecules, its hydrophilicity increases, the outer coating PAR of the PAR / NH2-MSN@SA microspheres dissolves, and SA is gradually released from the mesopores of NH2-MSN. Therefore, it can be seen that when the pH is less than 5, the sustained-release antibacterial agent has an obvious release, and the release is the most at a pH of 1.5, with a cumulative release rate of about 81% over 7 days ( Figure 7 ). And compared with the non-oscillating group ( Figure 8 Compared to the oscillation group, the pH-responsive slow-release antibacterial agent released more SA (approximately 10%), indicating that hydraulic shock in a real mining environment can accelerate the release of the slow-release antibacterial agent. Furthermore, there was no sudden release of SA throughout the entire process, indicating the good stability of the pH-responsive slow-release antibacterial agent.

[0117] In order to further explore the pH-responsive release behavior of PAR / NH2-MSN@SA, the cumulative release rate and release rate of the sustained-release antibacterial agent in aqueous solution with a pH range of 1 to 7 were determined over 120 h. Figure 9 As can be seen, when the environmental pH is greater than 5.5, the release rate of the SA antibacterial agent is slow. At a pH of 7, the cumulative release rate and average release rate of the sustained-release antibacterial agent over 120 hours are 17.45% and 1.23 μg / (g·h), respectively. At a pH of 1, the cumulative release rate and average release rate of the sustained-release antibacterial agent over 120 hours are 80.12% and 5.85 μg / (g·h), respectively. This indicates that the SA concentration released by the sustained-release antibacterial agent is higher and the average release rate is faster in a low pH environment. This further demonstrates that the sustained-release antibacterial agent exhibits a certain pH-responsiveness.

[0118] Example 8: Study on the release kinetics of pH-responsive sustained-release antibacterial agents

[0119] In order to explore the sustained-release mechanism of PAR / NH2-MSN@SA, the release behavior of the sustained-release antibacterial agent was fitted and analyzed using zero-order release kinetics, first-order release kinetics, Korsmeyer-Peppas model and Higuchi model.

[0120] (1) Zero-order release model: refers to a model in which the drug release rate is constant and does not change with time. The release of the drug in the zero-order release model can be expressed as follows:

[0121]

[0122] Where: —Cumulative release percentage of drug at time t; K0—release rate constant of zero-order release model.

[0123] (2) First-order release model: refers to the release rate and the active ingredient of the drug

[0124] is directly proportional, which can be expressed by the following formula:

[0125]

[0126] Where: a—drug concentration; k—release rate constant of the first-order release model.

[0127] (3) Korsmeyer-Peppas model: An equation proposed by Korsmeyer et al. to describe the release of drugs from sustained-release dosage forms:

[0128]

[0129] Where: K is the release rate constant of the Korsmeyer-Peppas model; n is the diffusion exponent.

[0130] (4) Higuchi model: A mathematical model proposed by Higuchi et al. for the sustained release of water-soluble active substances and similar preparations from semisolid or solid matrices:

[0131]

[0132] Where: KH—release rate constant of Higuchi model; w—Higuchi model coefficient.

[0133] According to the release curves of pH-responsive sustained-release antibacterial agents at different pH values, in order to explore the sustained-release mechanism of PAR / NH2-MSN@SA, the release behavior of the sustained-release antibacterial agents in the oscillation group was fitted and analyzed using four different drug release models. The fitting results are shown in Figure 10-13 And Table 1.

[0134] Table 1 Release kinetics related parameters

[0135]

[0136]

[0137] According to the fitting analysis results in Table 1, the release curves of NH2-MSN@SA in solutions with different pH values ​​have the highest fitting degree for the first-order release kinetic mechanism, R 2The value is closest to 1. The release exponent n in the Korsmeyer-Peppas equation can represent the drug release mechanism. For microspheres, when n > 0.85, the skeleton dissolution mechanism is dominant, making it particularly suitable for formulations with unclear release mechanisms. Release curves at different pH levels also fit the Korsmeyer-Peppas equation well: n = 0.56 at pH 1.5, n = 0.59 at pH 3, and n = 0.57 at pH 5, all ranging from 0.43 to 0.85, indicating a non-Fickian release mechanism characterized by both diffusion and dissolution. This suggests that the pH-responsive coating material PAR dissolves under acidic conditions, opening the "gateway" blocked in the NH2-MSN@SA pores and allowing SA to slowly be released from the pores and the microsphere interior. At pH 7, n = 0.39, less than 0.43, indicating a Fickian release mechanism dominated by diffusion. At this point, the release of a small amount of SA is primarily from NH2-MSN@SA not coated by PAR. The results showed that after amino modification and PAR coating, NH2-MSN@SA exhibited good sustained-release ability and certain pH responsiveness, providing a new idea for the design of pH-responsive sustained-release antibacterial agents.

[0138] Example 9: Simulation of the application of pH-responsive slow-release antibacterial agent in inhibiting pyrite biooxidation

[0139] A column experiment was conducted to simulate the actual mine environment. Pyrite sand was filled in the glass column and leached using actual mine water. The pH, ORP, total iron ion concentration and sulfate ion concentration of the leachate were measured to explore the inhibitory effect of pH-responsive slow-release antibacterial agent on the bio-oxidation of pyrite in the actual environment.

[0140] Preferably, a flow rate of 0.5 mL / min was selected as the flow rate for exploring the slow-release performance of the slow-release antibacterial agent. The flow rate selected in the simulation experiment more realistically reflects the hydraulic conditions for the slow release of the pH-responsive slow-release antibacterial agent in abandoned mines. The results of the column test have corresponding guiding significance for the application of pH-responsive slow-release antibacterial agents in actual environments.

[0141] Simulation experimental device such as Figure 14 As shown. The glass column has an inner diameter of 8 cm and a height of 50 cm. From top to bottom, it is filled with 10 cm of gravel, 30 cm of pyrite, and then 10 cm of gravel. 2.5 L of non-sterile AMD is circulated for leaching. To increase the contact area between AMD and the mineral and prevent AMD from flowing vertically through the column due to gravity, the AMD leachate containing the leaching microorganisms is passed from bottom to top through the gravel, mineral, and gravel before flowing out of the top and being collected in a leachate collection tank.

[0142] The application simulation was set up in two groups: the experimental group was added with 10% (concentration of 1×10 7cells / mL) of Af bacterial solution and 500 mg of a pH-responsive slow-release antibacterial agent were added. Only 10% of the Af bacterial solution was added to the biological group. The leaching period was set to 20 days, during which samples were collected from the leachate collection tank every other day to measure indicators such as pH, ORP, total iron ion concentration, and sulfate ion concentration.

[0143] The pH and ORP changes of the leachate are as follows: Figure 15 . In the case where no slow-release inhibitor was added (biological group), the pH showed a downward trend from slow to rapid and then to a gentle decline, and the ORP also showed the same trend, rising slowly to a rapid rise and finally tending to a gentle decline. In the group with the slow-release inhibitor (experimental group), the growth and reproduction of Af bacteria were inhibited by the continuous release of SA inhibitor during the experiment. During the experimental period, the pH and ORP values ​​changed less. ORP can reflect the redox characteristics of the system. The larger the ORP value, the stronger the oxidizing property of the system, and vice versa. The results show that the prepared slow-release inhibitor can effectively inhibit the growth activity of Af bacteria for a long time, thereby reducing the oxidative dissolution of pyrite, and has the effect of long-term and high-efficiency inhibition of the biological oxidation of sulfide minerals.

[0144] The total iron ions (Fe 3+ and Fe 2+ The sum of) and sulfate ion concentration changes as Figure 16 As shown. Total iron ions, SO4 2- The changes in concentration showed similar results to those of pH and ORP. In the group without the addition of slow-release antibacterial agent, the total iron ions and SO4 2- The concentrations of total iron ions and SO4 were 169.7 and 1012.1 mg / L respectively. When the slow-release antibacterial agent was added, the total iron ions and SO4 2- The concentrations of pyrite and iron ions were 55.4 and 405.6 mg / L, respectively. The leaching rates of total iron ions and sulfate ions were reduced by 67.35% and 59.92%, respectively. It can be seen that the prepared slow-release antibacterial agent can effectively inhibit the growth activity of Af bacteria for a long time, thereby inhibiting the oxidation and dissolution of pyrite, reducing the total iron ions and SO4 2- It can effectively inhibit the biological oxidation of sulfide minerals for a long time.

Claims

1. A method for in-situ treatment of acid mine drainage, characterized in that: The following steps are involved: A pH-responsive slow-release antibacterial agent is prepared, which can inhibit the biological oxidation of pyrite for a long time, thereby reducing acid mine drainage from the source; The preparation method of the pH-responsive sustained-release antibacterial agent comprises: (1) dissolving the template in water, heating and stirring to obtain a mixed solution; Adding a silicon source dropwise to the mixed solution, stirring, centrifuging, and drying and calcining the obtained solid product to obtain a mesoporous silica nanomaterial; (2) aminated the mesoporous silica nanomaterial by a post-grafting method, washing, and drying to obtain the aminated mesoporous silica nanomaterial; (3) Sorbic acid is loaded into amino-modified mesoporous silica nanomaterials by an impregnation method to obtain an antibacterial material; (4) dissolving polyacrylic acid resin IV in ethanol, and then adding magnesium stearate to obtain an ethanol mixed solution; then adding an antibacterial material to form a mixed emulsion; adding the mixed emulsion to a polyvinyl alcohol solution, washing and drying the solid product to obtain a pH-responsive sustained-release antibacterial agent.

2. The method according to claim 1, characterized in that In step (1), the template agent is one or more of hexadecyltrimethylammonium bromide and hexadecyltrimethylammonium chloride; In step (1), the silicon source is one or more of ethyl orthosilicate, propyl orthosilicate or butyl orthosilicate.

3. The method according to claim 2, characterized in that Step (1) specifically includes: 1.0 g of hexadecyltrimethylammonium bromide was dissolved in 480 mL of ultrapure water, added to 3.5 mL of 2 M sodium hydroxide solution, mixed well, and then heated to 80°C and magnetically stirred for 10 minutes; 5.00 mL of ethyl orthosilicate was dropwise added to the mixed solution and stirred for 2 hours. After a white precipitate appeared, the mixture was centrifuged at 5000 r / min for 5 minutes; the obtained lower layer solid product was washed three times with ultrapure water and ethanol in sequence, dried at 60°C for 12 hours, and then calcined at 550°C for 5 hours to obtain mesoporous silica nanomaterials.

4. The method according to claim 1, wherein Step (2) includes the following steps: The mesoporous silica nanomaterial obtained in step (1) is dispersed in water, acetic acid and 3-aminopropyltriethoxysilane (APTS) are added, stirred at room temperature, centrifuged, and the lower layer of solid product is removed, washed, and dried to obtain the amino-modified mesoporous silica nanomaterial.

5. The method according to claim 4, characterized in that Step (2) specifically includes: 500 mg of the mesoporous silica nanomaterial prepared in step (1) was dispersed in 50 mL of ultrapure water, 300 μL of acetic acid was added, 200 μL of 3-aminopropyltriethoxysilane (APTS) was added, and the mixture was stirred at room temperature for 24 h and centrifuged at 5000 r / min for 5 min. The lower layer of solid product was removed and washed three times with ultrapure water and ethanol in sequence, and dried in vacuum at 60 °C to obtain amino-modified mesoporous silica nanomaterial.

6. The method according to claim 1, wherein: Step (3) includes the following steps: The amino-modified mesoporous silica nanomaterial obtained in step (2) is ultrasonically dispersed in a sorbic acid solution, placed in a constant temperature shaker for oscillation to saturate the nanomaterial with adsorption, filtered, washed, and dried to obtain an antibacterial material.

7. The method according to claim 3, characterized in that Step (3) specifically includes: 50 mg of the amino-modified mesoporous silica nanomaterial prepared in step (2) was ultrasonically dispersed in 30 mL of a 3-5 g / L sorbic acid solution, the pH was adjusted to 5, and the solution was placed in a 30°C constant temperature shaker and shaken for 40-48 h to saturate the nanomaterial with adsorption. The solution was then filtered, washed, and dried to obtain an amino-modified mesoporous silica nanomaterial loaded with sorbic acid.

8. The method according to claim 1, characterized in that Step (4) specifically includes: 3.0 g of polyacrylic acid resin IV was weighed and dissolved in 200 mL of ethanol, and then 2.0 g of magnesium stearate was added to obtain an ethanol mixed solution; Weigh 2.0 g of the antibacterial material and ultrasonically disperse it in 100 mL of ultrapure water. Add it to the above ethanol mixed solution and continue stirring to form a mixed emulsion. Weigh 3.0 g of polyvinyl alcohol and pour it into 200 mL of deionized water. Heat and stir to completely dissolve it. Cool it to room temperature and adjust the pH of the solution to 10.0 to obtain a polyvinyl alcohol solution. The mixed emulsion was added dropwise to the polyvinyl alcohol solution, stirred continuously at medium to high speed at room temperature and then centrifuged. The solid product was washed with deionized water and n-hexane and dried to obtain a pH-responsive sustained-release antibacterial agent.

9. A pH-responsive slow-release antibacterial agent for in-situ inhibition of acid mine drainage, characterized in that: Prepared by the following method: (1) dissolving the template in water, heating and stirring to obtain a mixed solution; adding a silicon source dropwise to the mixed solution, stirring, centrifuging, and drying and calcining the obtained solid product to obtain a mesoporous silica nanomaterial; (2) aminated the mesoporous silica nanomaterial by a post-grafting method, washing, and drying to obtain the aminated mesoporous silica nanomaterial; (3) Sorbic acid is loaded into amino-modified mesoporous silica nanomaterials by an impregnation method to obtain an antibacterial material; (4) Polyacrylic acid resin IV was added to ethanol to completely dissolve it, and then magnesium stearate was added to prepare a pH-responsive sustained-release antibacterial agent using a solvent evaporation method.

10. A method for preparing a pH-responsive slow-release antibacterial agent for in-situ inhibition of acid mine drainage, comprising the following steps: (1) dissolving the template in water, heating and stirring to obtain a mixed solution; Adding a silicon source dropwise to the mixed solution, stirring, centrifuging, and drying and calcining the obtained solid product to obtain a mesoporous silica nanomaterial; (2) aminated the mesoporous silica nanomaterial by a post-grafting method, washing, and drying to obtain the aminated mesoporous silica nanomaterial; (3) Sorbic acid is loaded into amino-modified mesoporous silica nanomaterials by an impregnation method to obtain an antibacterial material; (4) Polyacrylic acid resin IV was added to ethanol to completely dissolve it, and then magnesium stearate was added to prepare a pH-responsive sustained-release antibacterial agent using a solvent evaporation method.

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