PH-responsive slow-release bacteriostatic agent for in-situ inhibition of generation of acidic mine wastewater and preparation method of pH-responsive slow-release bacteriostatic agent

Abstract

The invention discloses a pH-responsive slow-release bacteriostatic agent for in-situ inhibition of generation of acidic mine wastewater and a preparation method thereof, and belongs to the technical field of mine pollution remediation. Preparation raw materials are selected as follows: sorbic acid (SA), aminated mesoporous silica (NH2-MSN) and polyacrylic resin IV (PAR). Sorbic acid in the bacteriostatic agent has good bacteriostatic efficacy, and aminated mesoporous silica is used as a slow-release material, so that the bacteriostatic durability and stability of the bacteriostatic agent are improved. According to the invention, the polyacrylic resin IV is used as an outer layer blocking molecule, and has excellent pH response property.

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 acid mine wastewater, a pH-responsive slow-release antibacterial agent for in-situ inhibiting the generation of acid mine wastewater, and a preparation method thereof. Background Art

[0002] my country is rich in metal mineral resources. With the frequent occurrence of energy crises and the increasing status of energy, my country has continued to increase its efforts to develop existing mine resources, which has caused a series of serious ecological and environmental problems. After mining, a large amount of tailings and abandoned mines will be formed. Acid mine drainage (AMD) is the low pH, high concentration of heavy metals and sulfates formed by the catalytic oxidation of metal sulfides (such as pyrite) in tailings or abandoned mines under the joint action of air, water and microorganisms.

[0003] The current AMD control technologies mainly include two categories: end-of-pipe control technology and source control technology. Source control technology is to analyze and study the production pathways of AMD, and inhibit the formation of AMD by blocking oxygen, passivating minerals, and inhibiting the activity of acid-producing microorganisms. It mainly includes covering method, neutralization method, antibacterial method, etc.

[0004] The antibacterial method is one of the most commonly used methods for source control of acid mine drainage, as it is easy to operate, low cost, and good economy. However, in actual engineering applications, antibacterial agents are easily lost or degraded due to changes in environmental and climatic conditions. In order to ensure long-term stability, a large amount of antibacterial agents must be used, which is likely to produce drug-resistant genes and has a low utilization rate. In addition, current research on antibacterial agents mainly focuses on preparation and performance, and has not yet considered the response of performance 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 selects sorbic acid (SA), amino mesoporous silica (NH2-MSN) and polyacrylic acid resin IV (PAR) as antibacterial agent, sustained-release material and outer blocking molecule, respectively, optimizes and prepares a new type of pH-responsive sustained-release antibacterial agent, conducts release kinetics research, reveals the sustained-release mechanism, and provides a theoretical basis and technical support for the practical application of pH-responsive antibacterial agents in acid mine drainage treatment.

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

[0007] The 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 invention is to provide a method for preparing a pH-responsive slow-release antibacterial agent for in-situ treatment of acidic mine wastewater.

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

[0010] The present invention analyzes the key influencing factors of the oxidation and dissolution of pyrite by Af bacteria, and finds that the change of pH will significantly affect the oxidation and dissolution of pyrite by Af bacteria. As the pH value decreases, the growth activity of the microorganism is better, the promoting effect on the oxidation and dissolution of pyrite is greater, and the oxidation rate of pyrite is higher. Therefore, a special pH-responsive slow-release antibacterial agent is designed, and the antibacterial agent exerts corresponding release behavior and effect through the change of environmental pH to achieve long-term regulation and reduce the promoting effect of microorganisms on the oxidation and dissolution of pyrite.

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

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

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

[0014] (1) Preparation of mesoporous silica nanomaterials: dissolving a template in water, heating and magnetically stirring to obtain a mixed solution; dropping a silicon source into the mixed solution, stirring and reacting, centrifuging, and drying and calcining the obtained solid product to obtain a mesoporous silica nanomaterial (MSN);

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

[0016] (3) Sorbic acid (SA) was loaded into amino-modified mesoporous silica nanomaterials by impregnation method to obtain antibacterial materials (NH2-MSN@SA);

[0017] (4) Polyacrylic acid resin IV (PAR) was added to ethanol to completely dissolve it, and then magnesium stearate was added to prepare a pH-responsive sustained-release antibacterial agent (PAR / NH2-MSN@SA) by solvent evaporation method.

[0018] In some embodiments, the template 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 comprises:

[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, and then the mixed solution was heated to 80°C and magnetically stirred for 10 min; 5.00 mL of tetraethyl orthosilicate was added dropwise to the mixed solution and stirred for 2 h. After a white precipitate appeared, the mixture was centrifuged at 5000 r / min for 5 min; the obtained lower layer solid product was washed three times with ultrapure water and ethanol in turn, dried at 60°C for 12 h, and then calcined at 550°C for 5 h to obtain a mesoporous silica nanomaterial.

[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] Take 500 mg of the mesoporous silica nanomaterial prepared in step (1), disperse it in 50 mL of ultrapure water, add 300 μL of acetic acid, add 200 μL of 3-aminopropyltriethoxysilane (APTS), stir at room temperature for 24 h, and centrifuge at 5000 r / min for 5 min; take the lower layer of solid product, wash it with ultrapure water and ethanol three times in sequence, and place it at 60 ° C under vacuum to obtain amino-modified mesoporous silica nanomaterial.

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

[0028] The amino 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 with adsorption, filter, wash, and dry to obtain NH2-MSN loaded with SA, recorded as NH2-MSN@SA.

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

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

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

[0034] Weigh 3.0 g of polyacrylic acid resin IV and dissolve it in 200 mL of ethanol, then add 2.0 g of magnesium stearate 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), pour it into 200 mL of deionized water, heat and stir to completely dissolve it, cool it to room temperature, and adjust the solution pH to 10.0 to obtain a PVA solution;

[0037] The mixed emulsion was added dropwise into the PVA solution, and the mixture was continuously stirred 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; dropping a silicon source into 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) are 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 nanomaterials;

[0042] (3) ultrasonically dispersing the amino mesoporous silica nanomaterial obtained in step (2) in a sorbic acid solution, placing it in a constant temperature shaker for shaking to saturate the nanomaterial with adsorption, filtering, washing, and drying 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 amination through a post-grafting method to obtain NH2-MSN, so that the surface of the MSN is positively charged in a neutral or acidic environment, thereby improving the stability of the antibacterial material and enhancing the adhesion of the antibacterial material.

[0049] In view of the acidic pH value of acid mine drainage, SA with good antibacterial effect and low cost under acidic conditions was selected as the loading object. Since the modified MSN carries -NH2 and is positively charged, it can better interact with SA with negatively charged carboxyl groups through electrostatic adsorption and molecular free diffusion, so that SA is adsorbed to the surface and inside of NH2-MSN.

[0050] PAR with an acidic responsiveness range that matches the pH of general acidic mine wastewater was selected as the plugging material. The surface charge of NH2-MSN is negative after loading SA, and PAR has a positively charged tertiary amino group, which can better wrap NH2-MSN@SA. The pH responsiveness of PAR / NH2-MSN@SA is mainly due to the fact that the nitrogen atom on the tertiary amino group in the PAR molecular chain contains a lone pair of electrons, which will be protonated under acidic conditions (pH<5), and the solubility is enhanced. When the pH is high, the PAR molecular chain is in a curled state, wrapping the NH2-MSN loaded with SA, blocking the surface mesoporous structure, and preventing it from releasing SA.

[0051] When the pH-responsive slow-release antibacterial agent is applied to acid mine drainage, when the pH value of the early AMD is high (pH>5) and there is no microorganism such as Af bacteria promoting 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- The pH value of AMD decreases rapidly, and when the pH value is low, the sustained-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 carry positive charges, 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 be slowly released. + The higher the concentration, the faster PAR dissolves and the more SA is released, thereby inhibiting the growth activity of microorganisms such as Af bacteria and reducing the promotion of 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 variation graph;

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

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

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

[0057] Figure 5 This is the effect of material ratio on SA adsorption;

[0058] Figure 6 This is the effect of initial pH on adsorption capacity;

[0059] Figure 7 The release performance diagram of pH-responsive sustained-release antibacterial agent at different pH (oscillation);

[0060] Figure 8 The release performance diagram of pH-responsive sustained-release antibacterial agent at different pH (no oscillation);

[0061] Fig. 9 The release rate diagram of pH-responsive sustained-release antibacterial agent at different pH;

[0062] Fig.10 It is the release kinetics fitting curve diagram of pH-responsive sustained-release antibacterial agent (zero-order release kinetics);

[0063] Fig.11 It is the release kinetics fitting curve diagram of pH-responsive sustained-release antibacterial agent (first-order release kinetics);

[0064] Fig.12 The release kinetics fitting curve of pH-responsive sustained-release antibacterial agent (Higuchi model);

[0065] Fig.13 The release kinetics fitting curve of pH-responsive sustained-release antibacterial agent (Korsmeyer-Peppas model);

[0066] Fig.14 This is a diagram of the simulation experiment device;

[0067] Fig.15 This is the graph of the changes in pH and ORP of the leachate;

[0068] Fig.16 This is a graph showing the changes in the total iron ion and sulfate ion concentrations in the leachate. DETAILED DESCRIPTION

[0069] The present invention is further described below in conjunction with specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form a new embodiment. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0070] The specific conditions not specified in the examples were carried out according to conventional conditions or conditions recommended by the manufacturer. All reagents and instruments used were conventional products obtained from commercial channels unless otherwise specified.

[0071]

[0072]

[0073] The pyrite samples used in the examples were all taken from abandoned mines in Dashu mining area, Xuyong County, Luzhou City, Sichuan Province. The raw ore was broken with a hammer to remove mineral impurities, and then the sample was further crushed with a ball mill, and finally ground with an agate mortar and passed through a 200-mesh sieve.

[0074] The ground pyrite powder is pretreated as follows:

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

[0076] (2) adding anhydrous ethanol and ultrasonically cleaning for three times to remove some water-insoluble oxidation products such as SO formed on the surface of pyrite during grinding;

[0077] (3) Wash three times in oxygen-free ultrapure water to remove residual HCl and some inorganic salt ions generated during the washing process;

[0078] (4) After vacuum drying at 50°C, seal and store until use.

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

[0080] The Acidithiobacillus ferrooxidans used in the examples was purchased from China General Microbiological Culture Collection Center (CGMCC) with a strain number of 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 is determined using the "Electrode Method for Determination of pH Value of Water Quality" (HJ 1147-2020);

[0083] ORP was determined using the “Determination of Redox Potential Potentiometric Method” (SL 94-1994);

[0084] The total iron ion concentration was determined by the o-phenanthroline spectrophotometric method (trial implementation) (HJ / T 345-2007);

[0085] Sulfate ion is determined by the “Barium Chromate Spectrophotometry (Trial)” (HJ / T 342-2007).

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

[0087] Take 1mL of the solution to be tested in a 25mL stoppered colorimetric tube, add 5mL of water, then add 1mL of 0.5% potassium dichromate solution and 1mL of 0.15mol / L sulfuric acid, and shake well. Heat in a boiling water bath for 5min, add 2mL of 0.5% thiobarbituric acid solution, and shake well. Heat in a boiling water bath for another 10min, take out and quickly cool with cold water, add water to the scale, and shake well. Use a 1cm colorimetric dish and blank solution as reference, measure the absorbance at 530nm, and calculate the SA content according to the standard curve.

[0088] Example 1: Determination of Minimum Inhibitory Concentration

[0089] SA antibacterial agent 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 Fe) 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) to the bottle, three parallels in each group, the control group is filled up to 100mL with 9K culture medium, sealed with sealing film, and cultured at 30℃, 150r / min constant temperature shaking, and regularly sampled to determine the Fe 2+ Concentration, calculate Fe 2+ The minimum concentration of SA was determined by the oxidation inhibition rate.

[0090] Fe of Af bacteria under the treatment of SA inhibitor with 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 2+ The oxidation speed is fast, and it is basically completely oxidized 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+ The oxidation was very slow, with less than 10% of Fe 2+The results showed that the addition of SA at a concentration of 10 mg / L or more could effectively inhibit the growth of Af bacteria and reduce the demand for Fe. 2+ of oxidation.

[0091] The inhibitory effect of antibacterial agents on Af bacteria is generally measured by Fe 2+ It is expressed by the concentration change. That is: I = (AB) / C. Among them, I is the inhibition rate; A is the Fe 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 remained high, 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 the addition of SA at a concentration of 10 mg / L or more could effectively inhibit the activity and growth of Af bacteria and reduce the oxidation inhibition rate of Fe 2+ of 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, heat the mixed solution to 80℃ and stir magnetically for 10min. Take 5.00mL of tetraethyl orthosilicate (tetraethyl silicate) and add it dropwise to the mixed solution, stir for 2h, centrifuge at 5000r / min for 5min after a white precipitate appears, pour out the supernatant, wash the lower solid product with ultrapure water and ethanol three times in turn, and place it at 60℃ and vacuum dry for 12h to obtain CTAB-MSN. Finally, calcine in a muffle furnace at 550℃ for 5h to remove the template CTAB in the mesopores, and obtain MSN;

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

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

[0097] Take 50 mg NH2-MSN and ultrasonically disperse it in 30 mL 3 g / L SA solution, adjust the pH to 5, place it in a constant temperature shaker at 30 ° C and oscillate for 40 h to saturate the NH2-MSN nanomaterial with adsorption, filter, wash and dry to obtain NH2-MSN loaded with SA, recorded as NH2-MSN@SA.

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

[0099] Weigh 3.0g PAR and add it to a beaker containing 200mL ethanol. Ultrasonicate for 30min to completely dissolve it, and then add 2.0g magnesium stearate. Weigh 2.0g of the prepared sustained-release antibacterial agent NH2-MSN@SA and ultrasonically disperse it in 100mL ultrapure water. Add it to the above ethanol mixed solution and continue stirring to form a mixed emulsion. Take 3.0g polyvinyl alcohol (PVA) and pour it into a beaker containing 200mL deionized water. Heat and stir to completely dissolve it, cool to room temperature, and adjust the solution pH to 10.0 to ensure that the NH2-MSN@SA wrapped in PAR has no holes. Add the mixed emulsion dropwise to the PVA solution, and continue stirring at medium and high speed at room temperature to evaporate all the organic solvents. After standing, centrifuge, wash the solid product with appropriate amounts of deionized water and n-hexane, and dry 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, and the effect of different APTS addition amounts on the loading of SA on NH2-MSNs was investigated. Figure 3 As shown. Compared with unmodified MSN, the adsorption of SA by MSN modified by APTS is significantly improved after modification. This is due to the interaction between the positive charge on the surface of NH2-MSN and the negative charge on the surface of SA after modification. The number of positive charge groups on the surface of MSN increases after modification by APTS, which has an electrostatic adsorption effect with the negative charge groups on the surface of SA. Adding too much APTS does not significantly increase the adsorption of SA by MSN. When 200μL of APTS is added, the adsorption effect of SA is better, about 180.74mg / g. The results show that the adsorption effect of SA by MSN modified by APTS is better, and the adsorption effect of SA is more ideal when 200μL of APTS is added.

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

[0103] Weigh a certain amount of SA and dissolve it in a mixed solution of ultrapure water / ethanol to a constant volume of 100 mL. Add a certain amount of NH2-MSN and 30 mL of SA solution to a 50 mL centrifuge tube, with a mass ratio of SA: NH2-MSN = 2:1. After sealing, place the centrifuge tube horizontally in a constant temperature oscillator at 30°C and 150 r / min for 60 hours; filter and collect the filtrate for load determination. The SA concentrations used were 1, 3, 5, 7, and 9 g / L, respectively, with three parallels in each group.

[0104] The research results are as follows Figure 4 As shown, when the initial concentration of SA 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 concentration of SA 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 during the adsorption of 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 loading capacity of SA. 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 ultrapure water / ethanol mixed solution, dilute to 1L, add a certain mass of NH2-MSN and 30mL SA solution in a 50mL centrifuge tube, seal it and place the centrifuge tube horizontally in a constant temperature oscillator at 30℃ and 150r / min for 60h; filter and collect the filtrate to measure the loading capacity. The input mass ratios of SA and SiO2 are 2:1, 1:1 and 1:2, respectively, and three parallels are used in each group.

[0107] The results are as follows Figure 5 As shown. With the increase of the input ratio of the carrier material NH2-MSN, its loading capacity for SA is negatively correlated. When the input mass ratio of SA and NH2-MSN is 2:1, the SA loaded per unit mass of NH2-MSN is the highest, which is about 254 mg / g. This may be because the specific surface area, pore size and pore volume of NH2-MSN itself are relatively fixed, and it has a certain loading capacity for SA molecules. When the loading of NH2-MSN on SA is higher than its own drug loading capacity, the loading capacity will weaken with the increase of NH2-MSN input.

[0108] Example 5: Effect of Solution pH on the Loading Amount of pH-responsive Slow-release Antibacterial Agent

[0109] Accurately weigh 5g of SA and dissolve it in ultrapure water / ethanol mixed solution, dilute to 1L, add 75mgNH2-MSN and 30mL SA solution in a 50mL centrifuge tube, adjust the pH of each group to 2, 5, and 8, and run three parallel tests in each group. After sealing, place the centrifuge tube horizontally in a constant temperature oscillator at 30℃ and 150r / min for 60h; collect the filtrate by filtration and measure the loading capacity.

[0110] The results of the research 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 NH2-MSN on SA, which is about 268.37 mg / g. Lower or higher solution pH is not conducive to the adsorption of NH2-MSN on SA. Solution pH not only affects the surface potential and the state of surface groups of NH2-MSN, but also affects the molecular structure of SA. SA solution contains slightly acidic functional groups carboxyl groups, which will be 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 group will be deprotonated, so that SA carries a negative charge and 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 mixed solution, dilute to 1L, add 75mgNH2-MSN and 30mLSA solution in a 50mL centrifuge tube. After sealing, place the centrifuge tube horizontally in a constant temperature oscillator at 30℃ and 150r / min for a certain period of time; filter and collect the filtrate for loading capacity determination. The selected oscillation times are 12h, 24h, 36h, 48h and 60h, respectively, to determine the adsorption saturation time of NH2-MSN on SA.

[0113] Through the adsorption of different initial SA concentrations, different feed ratios and different solution pH, it can be observed that the adsorption of SA by NH2-MSN reaches equilibrium at about 48 hours. When the initial SA concentration is 5g / L, the added mass ratio of SA to NH2-MSN is 2:1, the solution pH is 5, and the loading time is 48h, the SA antibacterial agent adsorbed by NH2-MSN is the largest, and the adsorption amount at this time is about 268.37mg / g, and the loading rate is 16.76%.

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

[0115] Weigh 50 mg of dry PAR / NH2-MSN@SA and add it to a dialysis bag with a molecular weight of 14000 and a cut-off of 15 cm. Add 5 mL of aqueous solutions with different pH values ​​(1, 5, 3, 5, 7) to it. After clamping the two ends, add the dialysis bag to 100 mL of aqueous solutions with corresponding pH values. Oscillate at a constant temperature and low speed for 7 days at 30°C for sustained release (one group oscillates, and one group does not oscillate). Take samples at regular intervals and replenish the aqueous solution with the corresponding pH value. The absorbance of SA is measured by ultraviolet spectrophotometer, and the cumulative release rate Ri of SA antibacterial agent at different times is calculated.

[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 in 7 days is only about 17.45%. This is because the NH2-MSN@SA microspheres wrapped by 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 group in the PAR molecule, 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 most is released at a pH of 1.5, with a cumulative release rate of about 81% in 7 days ( Figure 7 ). And compared with the non-oscillating group ( Figure 8 ), the oscillation group released more SA (about 10%), indicating that the hydraulic impact in the actual mining environment can accelerate the release of the slow-release antibacterial agent. And there was no sudden release of SA during the whole process, indicating that the pH-responsive slow-release antibacterial agent has good stability.

[0117] 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. Fig. 9 It can be seen that when the environmental pH is greater than 5.5, the release rate of the SA antibacterial agent is slow. When the pH is 7, the cumulative release rate and average release rate of the sustained-release antibacterial agent in 120 hours are 17.45% and 1.23ug / (g·h), respectively. When the pH is 1, the cumulative release rate and average release rate of the sustained-release antibacterial agent in 120 hours are 80.12% and 5.85ug / (g·h), respectively, indicating that the SA concentration released by the sustained-release antibacterial agent in a low pH environment is greater and the average release rate is faster. This further shows that the sustained-release antibacterial agent exhibits a certain pH response ability.

[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 constant drug release rate that does not change with time. The release of drugs in the zero-order release model can be expressed by the following formula:

[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] It is directly proportional to each other and 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 index.

[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, four different drug release models were used to fit the release behavior of the sustained-release antibacterial agents in the oscillation group. 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 index n in the Korsmeyer-Peppas equation can represent the release mechanism of the drug. For microspheres, when n>0.85, the skeleton dissolution mechanism is dominant, which is especially suitable for preparations with unclear release mechanisms. The release curves at different pH also have a good fit to the Korsmeyer-Peppas equation. When pH is 1.5, n=0.56; when pH is 3, n=0.59; when pH is 5, n=0.57, all between 0.43 and 0.85, which is a non-Fickian release mechanism, with two behaviors, diffusion and dissolution. This shows that the pH-responsive coating material PAR dissolves under acidic conditions, causing the "gateway" blocked in the NH2-MSN@SA pores to open, and then SA is slowly released from the pores and microspheres. When pH is 7, n=0.39, which is less than 0.43, is a Fickian release mechanism, dominated by diffusion. At this time, it is mainly NH2-MSN@SA that is not coated by PAR that releases a small amount of SA. The results showed that after amino modification and PAR coating, NH2-MSN@SA exhibited good sustained-release ability and certain pH responsiveness, which provided a new idea for the design of pH-responsive sustained-release antibacterial agents.

[0138] Example 9: Application simulation of pH-responsive sustained-release antibacterial agent in inhibiting pyrite biooxidation

[0139] The actual mine environment was simulated by column experiments. The glass columns were filled with pyrite sand, and leaching was carried out 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 agents on the biological oxidation of pyrite in the actual environment.

[0140] Preferably, a flow rate of 0.5 mL / min is 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 the pH-responsive slow-release antibacterial agent in actual environments.

[0141] Simulation experimental device such as Fig.14 As shown. The inner diameter of the glass column is 8 cm and the height is 50 cm. 10 cm of sand and gravel, 30 cm of pyrite, and 10 cm of sand and gravel are filled from top to bottom, and 2.5 L of non-sterile AMD is circulated for leaching. In order to increase the contact area between AMD and minerals and prevent AMD from flowing vertically through the column due to gravity, the AMD leaching solution containing leaching microorganisms passes through sand and gravel, minerals and sand and gravel from bottom to top, then flows out from the top and is collected by the leaching solution 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 pH-responsive slow-release antibacterial agent were added to the biological group, and only 10% of Af bacterial solution was added to the biological group. The leaching time was set to 20 days, during which samples were taken from the leaching liquid collection tank every other day to measure the pH, ORP, total iron ion concentration, sulfate ion concentration and other indicators of the leaching liquid.

[0143] The pH and ORP changes of the leaching solution are as follows: Fig.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 gentle, and the ORP also showed the same trend, rising slowly to rapidly rising and finally tending to gentle. In the group with 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 a long-term and efficient effect of inhibiting the biological oxidation of sulfide minerals.

[0144] The total iron ion (Fe 3+ and Fe 2+ The sum of the concentration of sulfate ions) and the concentration of sulfate ions Fig.16 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 the slow-release antibacterial agent, the total iron ion 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 55.4 and 405.6 mg / L were respectively, and 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 new type of pH-responsive slow-release antibacterial agent is prepared, which can inhibit the biological oxidation of pyrite for a long time, so as to reduce 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) using an impregnation method to load sorbic acid into an amino-modified mesoporous silica nanomaterial to obtain an antibacterial material; (4) Add polyacrylic acid resin IV into ethanol to completely dissolve it, then add magnesium stearate, and use the solvent volatilization method to prepare 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 cetyltrimethylammonium bromide or cetyltrimethylammonium chloride, preferably cetyltrimethylammonium bromide (CTAB); In step (1), the silicon source is one or more of tetraethyl orthosilicate, propyl orthosilicate or butyl orthosilicate, preferably tetraethyl orthosilicate (TEOS).

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 2M sodium hydroxide solution, mixed, and then heated to 80°C and magnetically stirred for 10 min; 5.00 mL of ethyl orthosilicate was added dropwise to the mixed solution and stirred for 2 h. After a white precipitate appeared, the mixture was centrifuged at 5000 r / min for 5 min; the obtained lower layer solid product was washed three times with ultrapure water and ethanol in turn, dried at 60°C for 12 h, and then calcined at 550°C for 5 h to obtain a mesoporous silica nanomaterial.

4. The method according to claim 1, characterized in that: Step (2) comprises 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: Take 500 mg of the mesoporous silica nanomaterial prepared in step (1), disperse it in 50 mL of ultrapure water, add 300 μL of acetic acid, add 200 μL of 3-aminopropyltriethoxysilane (APTS), stir at room temperature for 24 h, and centrifuge at 5000 r / min for 5 min; take the lower layer of solid product, wash it with ultrapure water and ethanol three times in sequence, and place it at 60 ° C. Vacuum dry to obtain amino-modified mesoporous silica nanomaterial.

6. The method according to claim 1, characterized in that: Step (3) comprises the following steps: The amino 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: Take 50 mg of the amino-modified mesoporous silica nanomaterial prepared in step (2) and ultrasonically disperse it in 30 mL of 3-5 g / L sorbic acid solution, adjust the pH to 5, place it in a 30° C. constant temperature shaker and oscillate for 40-48 hours to saturate the nanomaterial with adsorption, filter, wash, and dry to obtain the amino-modified mesoporous silica nanomaterial loaded with sorbic acid.

8. The method according to claim 1, characterized in that Step (4) comprises the following steps: The polyacrylic acid resin IV is dissolved in ethanol, and then magnesium stearate is added to obtain an ethanol mixed solution; then an antibacterial material is added to form a mixed emulsion; the mixed emulsion is added to a polyvinyl alcohol solution, and the solid product is washed and dried to obtain a pH-responsive sustained-release antibacterial agent; Preferably, step (4) specifically includes: Weigh 3.0 g of polyacrylic acid resin IV and dissolve it in 200 mL of ethanol, then add 2.0 g of magnesium stearate 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, pour into 200 mL of deionized water, heat and stir to completely dissolve it, cool to room temperature, adjust the pH of the solution to 10.0, and obtain a polyvinyl alcohol solution; The mixed emulsion was added dropwise into the polyvinyl alcohol solution, and the mixture was continuously stirred 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 wastewater generation, characterized in that: Prepared by the following method: (1) dissolving the template in water, heating and stirring to obtain a mixed solution; dropping a silicon source into 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) using an impregnation method to load sorbic acid into an amino-modified mesoporous silica nanomaterial to obtain an antibacterial material; (4) Add polyacrylic acid resin IV into ethanol to completely dissolve it, then add magnesium stearate, and use the solvent volatilization method to prepare a pH-responsive sustained-release antibacterial agent.

10. A method for preparing a pH-responsive slow-release antibacterial agent for in-situ inhibition of acid mine wastewater generation, 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) using an impregnation method to load sorbic acid into an amino-modified mesoporous silica nanomaterial to obtain an antibacterial material; (4) Add polyacrylic acid resin IV into ethanol to completely dissolve it, then add magnesium stearate, and use the solvent volatilization method to prepare a pH-responsive sustained-release antibacterial agent.

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