Alkaline slow-release filler for neutralizing acid mine wastewater and preparation method of alkaline slow-release filler

Abstract

The invention discloses an alkaline slow-release filler for neutralizing acid mine wastewater and a preparation method thereof, and relates to the technical field of sewage treatment.The alkaline slow-release filler is 5-15 mm in particle size and comprises an inner core and a shell, and the mass of the shell is 10-15% of that of the inner core; according to the alkaline slow-release filler for neutralizing the acidic mine wastewater and the preparation method thereof, linear controllable release of alkaline ions is realized through core-shell structure design, the pH value of the wastewater can be maintained to be 6-9 for more than 6 months, and the problem that heavy metal removal of a traditional material is not comprehensive is solved; the shell is high in mechanical strength and not easy to disintegrate in water, the neutralization reaction is mild, the amount of generated chemical sludge is reduced compared with that of a traditional method, and the risk of secondary pollution is reduced; the whole preparation process is simple; the finished product has uniform particle size, can be directly filled in treatment facilities such as a reaction column and an ecological infiltration bed, and is suitable for treatment of acid mine wastewater with different scales and different water qualities.

Description

TECHNICAL FIELD

[0001] The present application relates to sewage treatment technology, in particular to an alkaline slow-release filler for neutralizing acid mine drainage and a preparation method thereof. BACKGROUND

[0002] Acid mine drainage (AMD) is a typical pollutant generated in mining activities, with a pH value usually below 4 and containing high concentrations of heavy metal ions (such as iron, manganese, copper, zinc, etc.) and thallium (TI) with high toxicity and strong migration, causing serious harm to water bodies, soil and ecosystems. Traditional neutralization treatment methods include direct addition of alkaline substances such as lime and sodium hydroxide, but these methods have problems such as too fast neutralization rate, easy to cause local pH too high, generate a large amount of sludge, and secondary pollution. In addition, the flow and composition of acid mine drainage fluctuate greatly, and traditional methods are difficult to achieve stable and efficient treatment.

[0003] Slow-release filler technology can extend the neutralization effect, reduce the addition frequency, and reduce the operating cost by controlling the release rate of alkaline substances. Existing slow-release fillers are mostly made by mixing a single alkaline substance (such as calcium oxide) with a binder, but have defects such as unstable release rate, easy to be cemented, clogged, and insufficient heavy metal adsorption capacity, resulting in incomplete heavy metal precipitation and poor slow-release effect. Therefore, it is a technical requirement in the field to develop a filler that can simultaneously achieve alkaline slow-release and heavy metal adsorption. SUMMARY

[0004] The purpose of the present application is to provide an alkaline slow-release filler for neutralizing acid mine drainage and a preparation method thereof, to solve the defects of poor slow-release effect and insufficient heavy metal adsorption capacity in the prior art.

[0005] In order to achieve the above-mentioned purpose, the present application provides the following technical scheme: an alkaline slow-release filler for neutralizing acid mine drainage, the filler is of core-shell structure, the particle size is 5-15 mm, including an inner core and an outer shell, the mass of the outer shell is 10-15% of the mass of the inner core;

[0006] The inner core raw materials include, by weight: 25-40 parts of calcium oxide, 15-25 parts of magnesium hydroxide, 5-10 parts of sulfide, 8-15 parts of pore-forming agent, 3-8 parts of treatment agent, and 1-3 parts of deionized water;

[0007] The outer shell raw materials include, by weight: 20-30 parts of hydrophobically modified water-based polymer, 10-18 parts of nano diatomite, 12-20 parts of iron-manganese oxide modified attapulgite, 1-2 parts of dispersant, and 30-40 parts of deionized water.

[0008] Further, the processing agent is a composite powder of ferrous sulfide and hydroxyapatite, and the mass ratio of the ferrous sulfide to the hydroxyapatite is 1-2:1.

[0009] Further, the shell has a microporous network structure, and the pore size ranges from 0.1 to 1 μm.

[0010] Further, the pore-forming agent is at least one of NaCl crystals, sucrose, and starch, and the particle size ranges from 100 to 200 meshes; and the sulfide is at least one of sodium sulfide, potassium sulfide, and calcium sulfide.

[0011] Further, the hydrophobically modified water-based polymer is polyvinyl acetate-acrylic acid copolymer, and the dispersant is sodium dodecyl benzene sulfonate or polyethylene glycol.

[0012] A preparation method of an alkaline slow-release filler for neutralizing acid mine wastewater, which is suitable for preparing the alkaline slow-release filler for neutralizing acid mine wastewater, comprises the following steps:

[0013] S1, the calcium oxide, magnesium hydroxide, sulfide, pore-forming agent, and processing agent are weighed according to the mass fraction, dry-mixed in a mixer at a speed of 300-500 r / min for 30 minutes, then deionized water is added, and the mixing is continued for 5-8 minutes to prepare core wet particles with a water content of 15-20%, the core wet particles are dried at 60-80℃ for 2 hours to obtain solidified core particles;

[0014] S2, the attapulgite is calcined at 500-600℃ for 2-3 hours, then added to an iron-manganese mixed salt solution, the pH is adjusted to 7.5-8.5, and the solution is stirred at a constant temperature of 60-70℃ for 4-6 hours, then filtered, washed, dried at 80-100℃ to a constant weight, and ground to 200-300 meshes to obtain iron-manganese oxide modified attapulgite;

[0015] S3, the polyvinyl acetate-acrylic acid copolymer, nano diatomite, iron-manganese oxide modified attapulgite, dispersant, and deionized water are placed in a high-speed dispersion machine, and dispersed at a speed of 800-1000 r / min for 30-40 minutes to obtain a composite shell slurry;

[0016] S4, the solidified core particles are placed in a fluidized bed coater, and the composite shell slurry is sprayed to obtain coated particles;

[0017] S5, the coated particles are first dried at 80-90℃ for 2 hours, then solidified at 95-100℃ for 1 hour, cooled to room temperature, and sieved to obtain alkaline slow-release fillers with a particle size of 5-15 mm.

[0018] Further, the Fe2+ and Mn2+ in the iron-manganese mixed salt solution in S2 are in a mass ratio of 1:1-2. 3+Concentration of 0.1-0.2mol / L, Mn 2+ Concentration of 0.05-0.1mol / L.

[0019] Further, the fluidized bed coating machine of S4 has an air inlet temperature of 40-50 DEG C, an atomization pressure of 0.2-0.4 MPa, and a bed temperature of 35-40 DEG C.

[0020] Further, the nozzle pressure is 0.2-0.5 MPa and the bed temperature is 60-80 DEG C when the spray composite shell slurry is sprayed in S4.

[0021] Further, the environmental humidity during the solidification of S5 for 1 hour is ≤40% RH.

[0022] Compared with the prior art, the alkaline slow-release filler for neutralizing acid mine wastewater and the preparation method thereof provided by the application can achieve linear controllable release of alkaline ions through core-shell structure design, do not need to be frequently added, can maintain the pH of wastewater at 6-9 for more than 6 months, and avoid pipeline fouling and heavy metal redissolution caused by local overalkalization.

[0023] The treatment agent and the outer shell iron-manganese oxide modified palygorskite can remove TI, As, Cd, Pb, Cr 6+ and other heavy metals, solving the problem of incomplete heavy metal removal of traditional materials; the outer shell is composed of hydrophobically modified polymers and nano diatomite, has high mechanical strength, and is not easy to disintegrate in water; and the neutralization reaction is mild, the amount of chemical sludge generated is reduced compared with traditional methods, and the risk of secondary pollution is reduced.

[0024] The whole preparation process is simple; the finished product has uniform particle size and can be directly filled in treatment facilities such as reaction columns and ecological infiltration beds, and is suitable for acid mine wastewater treatment of different scales and different water qualities. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can also be obtained by those skilled in the art according to these drawings.

[0026] Figure 1 The alkaline slow-release filler provided in the embodiments of the present application has the overall preparation process schematic diagram. DETAILED DESCRIPTION

[0027] In order to make those skilled in the art better understand the technical solutions of the present application, the present application will be further described in detail with reference to the drawings.

[0028] Embodiment one:

[0029] An alkaline slow-release filler for neutralizing acid mine drainage, the filler is a core-shell structure with a particle size of 5-15 mm, including a core and a shell, the mass of the shell is 10-15% of the mass of the core;

[0030] The core raw materials include, by weight parts: calcium oxide 25-40 parts, magnesium hydroxide 15-25 parts, sulfide 5-10 parts, pore-forming agent 8-15 parts, treatment agent 3-8 parts, deionized water 1-3 parts;

[0031] The shell raw materials include, by weight parts: hydrophobically modified water-based polymer 20-30 parts, nano diatomite 10-18 parts, iron-manganese oxide modified attapulgite 12-20 parts, dispersant 1-2 parts, deionized water 30-40 parts.

[0032] Calcium oxide CaO reacts with H + in AMD (CaO+2H + =Ca 2+ +H2O), rapidly increasing the pH of the wastewater, and is the main substance for neutralizing acidity; Ca 2+ generated by the reaction can combine with SO4 2- in the wastewater to generate CaSO4 precipitate, reducing the concentration of sulfate in the water body; in cooperation with magnesium hydroxide, it avoids the sudden rise in pH caused by a single alkaline substance.

[0033] Magnesium hydroxide Mg(OH)2 has lower solubility than calcium oxide, and reacts with H + at a slower rate (Mg(OH)2+2H + =Mg 2+ +2H2O), prolonging the alkaline release period and avoiding excessive local pH; after the initial neutralization by calcium oxide, OH - is continuously released to maintain the wastewater pH stable in the standard range of 6-9, and the generated Mg 2+ is non-toxic and will not cause secondary pollution to the water body.

[0034] Sulfide (at least one of sodium sulfide, potassium sulfide, and calcium sulfide) provides S 2- , which reacts with highly toxic heavy metals (such as Tl + , Cd 2+ , Pb 2+ ) in AMD to generate extremely insoluble sulfide precipitates (such as Tl2S, CdS, with solubility product Ksp<10 -20 ), achieving permanent fixation of heavy metals; it has a special effect on Tl + , which is difficult to remove by traditional neutralization methods, and solves the core pain point of thallium pollution in AMD; in cooperation with the treatment agent, it expands the range of heavy metal removal (such as covering both cationic heavy metals and Cr 6+ ).

[0035] FeS in the treatment agent (ferrous sulfide-hydroxyapatite composite powder, mass ratio 1-2:1) can supplement S 2- , strengthen the sulfide precipitation of Tl + , Pb 2+ ; at the same time, Fe 2+ can reduce Cr 6+ to Cr 3+ (Cr2O7 2- +6Fe 2+ +14H + =2Cr 3+ +6Fe 3+ +7H2O), facilitating subsequent precipitation; hydroxyapatite (Ca 10 (PO4)6(OH)2) can fix residual heavy metal ions through ion exchange (such as Ca 2+ exchange with Cd 2+ , Pb 2+ ) and adsorption, especially the adsorption capacity for Cd 2+ can reach 50-80mg / g; the formed heavy metal-apatite complex has very high stability, which can avoid the resolubilization of heavy metals caused by environmental pH fluctuation.

[0036] The pore-forming agent (at least one of NaCl crystals, sucrose, and starch, 100-200 mesh) constructs a porous structure, and in the preparation process, the pore-forming agent leaves pores through "drying volatilization (sucrose, starch)" or "water body dissolution (NaCl)", so that the inner core forms a connected microporous network (pore size mainly concentrated in 1-10μm); the porous structure expands the contact area of AMD with alkaline substances and heavy metal fixatives, which not only ensures sufficient neutralization reaction, but also avoids the "wrapping effect" of the inner core, so that the active ingredients cannot be released; by adjusting the amount of pore-forming agent (8-15 parts), the porosity can be fine-tuned, and then the release speed of OH - and S 2- can be controlled to match the flow fluctuation of AMD.

[0037] Deionized water (1-3 parts) is used as a wetting agent to make the solid components (such as calcium oxide and magnesium hydroxide) of the inner core form a plastic wet particle, which is convenient for subsequent drying and solidification; deionized water is used instead of tap water to prevent impurities such as Cl - and HCO3 - in water from reacting with the inner core components (such as CaO and HCO3 - to form CaCO3 to block the pores), ensuring the stability of the inner core function.

[0038] The film layer formed by the hydrophobically modified water-based polymer (polyvinyl acetate-acrylic acid copolymer) has hydrophobicity, which can slow down the penetration speed of water molecules in AMD to the inner core, and then control the release speed of OH- , S 2- release rate, the filler neutralization effect is extended to more than 6 months; resistant to acid corrosion (not easily degraded in AMD with pH = 3-4), and good compatibility with nano diatomite, modified attapulgite, forming a continuous and uniform shell layer; as a binder, nano diatomite, modified attapulgite and other particles are bonded together to ensure that the shell does not easily fall off during the fluidized bed coating process.

[0039] Nano diatomite (10-18 parts) itself has a porous structure, and after compounding with polymers, a "nano-micron" multi-level pore is formed in the shell, which allows AMD to slowly penetrate (ensures continuous reaction of the core) and avoids rapid dissolution of the core components; the porous structure provides a large number of adsorption sites that can adsorb small heavy metal precipitates (such as Fe(OH)3, Mn(OH)2 flocs) suspended in AMD, reducing the turbidity of the effluent; filled in the polymer film layer, equivalent to a "skeleton", improving the impact resistance and wear resistance of the shell, avoiding the disintegration of the filler during transportation or use.

[0040] Iron-manganese oxide modified attapulgite (12-20 parts) Iron-manganese oxide (such as Fe2O3, MnO2) in it: through oxidation-adsorption, remove Cr 6+ (MnO2 can oxidize Cr 3+ to Cr 6+ , then adsorb, Fe2O3 directly adsorbs Cr 6+ , As 3+ (oxidized to As 5+ , then forms FeAsO4 precipitate); attapulgite itself has a layered structure and high specific surface area, which can adsorb Pb 2+ , Zn 2+ and other heavy metals through ion exchange; the fibrous structure of attapulgite can prevent the filler from caking and plugging during use due to particle agglomeration; stable performance in a wide pH range (3-10), can adapt to fluctuations in AMD water quality.

[0041] Dispersant (sodium dodecylbenzenesulfonate or polyethylene glycol, 1-2 parts) can reduce the agglomeration force between nano diatomite and modified attapulgite particles when preparing the composite shell slurry, making the slurry uniformly dispersed (avoiding nozzle blockage during spraying); ensuring that each component of the shell is evenly coated on the surface of the core during the fluidized bed coating process, avoiding local shell layer being too thick (leading to slow release) or too thin (leading to fast release); improving the interfacial bonding force between the polymer and the mineral filler, reducing cracks in the shell during drying and curing.

[0042] In summary, the core calcium oxide and magnesium hydroxide provide alkaline substances, the shell polymer and nanometer diatomite control the release rate, realizing "fast neutralization of initial acidity + long-term maintenance of stable pH"; the core sulfide and the treatment agent realize preliminary precipitation of heavy metals, the shell iron-manganese oxide modified attapulgite realizes deep interception, solving the removal problem of "conventional heavy metals + highly toxic thallium, chromium" in AMD; the core pore-forming agent and the shell nanometer diatomite construct a double structure of "core porous mass transfer-shell microporous slow release", which not only ensures sufficient reaction, but also prolongs the service life; at the same time, the shell polymer + mineral filler improves the mechanical strength, avoiding the disintegration and blockage of the filler.

[0043] Each component realizes the core advantages of "neutralization efficiency, slow release, long-acting, complete heavy metal removal, mechanical stability" through clear functional division and synergistic effect, solving the technical defects of traditional AMD treatment methods.

[0044] Embodiment two:

[0045] The embodiment provides a technical scheme based on embodiment one: a basic slow-release filler for neutralizing acid mine wastewater, the filler is a core-shell structure, the particle size is 10mm, and the filler comprises a core and a shell, the mass of the shell is 13% of the mass of the core.

[0046] The core raw materials are calcium oxide 35 parts, magnesium hydroxide 18 parts, calcium sulfide 7 parts, pore-forming agent (sucrose + starch, mass ratio 1:1, particle size 180 meshes) 10 parts, treatment agent (ferrous sulfide and hydroxyapatite, mass ratio 1.8:1) 6 parts and deionized water 2 parts; the shell raw materials are polyvinyl acetate-acrylic acid copolymer 28 parts, nanometer diatomite 12 parts, iron-manganese oxide modified attapulgite 18 parts, polyethylene glycol 1.8 parts and deionized water 38 parts; wherein the shell is a microporous network structure, and the pore size is 0.6 microns.

[0047] Embodiment three:

[0048] Please refer to Figure 1 The embodiment provides a technical scheme based on embodiment one: a preparation method of a basic slow-release filler for neutralizing acid mine wastewater, which is suitable for preparing a basic slow-release filler for neutralizing acid mine wastewater, and comprises the following steps:

[0049] S1, the core raw materials are weighed according to the proportion, put into a mixing machine to dry mix at 400r / min for 30min, and then deionized water is added to continue mixing for 7min to prepare core wet particles with a moisture content of 18%; the core wet particles are dried at 70 DEG C for 2h to obtain solidified core particles.

[0050] S2, the attapulgite is calcined at 550 DEG C for 2.5h, and then an iron-manganese mixed salt solution (Fe 3+ concentration 0.15mol / L, Mn2+ The concentration of the solution was adjusted to 0.08 mol / L, and the pH was adjusted to 8.0. The mixture was stirred at 65°C for 5 hours. After filtration and washing, the mixture was dried at 90°C until the weight was constant. The mixture was ground to 250 mesh to obtain the iron-manganese oxide modified attapulgite.

[0051] S3, the shell raw material was put into a high-speed dispersion machine and dispersed at 900 r / min for 35 min to prepare a composite shell layer slurry.

[0052] S4, the inner core particles were placed in a fluidized bed coating machine (inlet air temperature 45°C, atomization pressure 0.3 MPa, bed temperature 38°C), and the composite shell layer slurry was sprayed at a nozzle pressure of 0.35 MPa and a bed temperature of 70°C. The coating mass of the outer shell was controlled to be 12% of the inner core.

[0053] S5, the coated particles were first dried at 85°C for 2 hours, and then cured at 98°C (ambient humidity 35% RH) for 1 hour. After cooling to room temperature, the particles were sieved to obtain basic slow-release fillers with a particle size of 8-12 mm.

[0054] Example Four:

[0055] The present embodiment provides a technical solution based on Examples Two and Three: performance detection experiment of the basic slow-release filler for neutralizing acid mine wastewater.

[0056] Through the performance detection experiment, the basic slow-release effect, heavy metal removal capacity and mechanical stability of the basic slow-release filler were verified.

[0057] Experimental water sample: simulated acid mine wastewater (pH=3.5, containing Fe 3+ 50mg / L, Mn 2+ 20mg / L, Tl + 0.5mg / L, Cd 2 + 1mg / L, Cr 6+ 2mg / L).

[0058] 1. Basic slow-release performance test:

[0059] Two groups of reaction columns (φ10cm×100cm) were filled with 5L of the filler of Example Two (experimental group) and 5L of traditional calcium oxide filler (control group), respectively. The simulated acid mine wastewater was continuously fed at a flow rate of 10L / h, and the pH value of the effluent was monitored daily. The time interval during which the pH value was maintained in the range of 6-9 was recorded. The basic release rate of the filler (calculated based on the OH - release amount) was calculated every month for a continuous period of 6 months.

[0060] The specific experimental results are shown in the following table:

[0061] Detection time pH of effluent in experimental group pH of effluent in control group Experimental group OH - Release rate (mg / (L.d)) Control OH - Release rate (mg / (L.d)) 1st month 7.8±0.2 8.5±0.5 125±5 350±15 3rd month 7.5±0.3 5.2±0.4 110±4 85±8 6th month 7.0±0.2 3.8±0.3 95±3 15±2

[0062] The experimental group is stable at pH 6-9 for more than 6 months, the alkaline release rate linearly decays, and there is no sudden drop phenomenon; the control group is only maintained at pH 6-9 for 1.5 months, the pH of the effluent is less than 6 after 3 months, the alkaline release is suddenly high in the early stage and rapidly decays in the later stage.

[0063] 2. Heavy metal removal performance test:

[0064] After the simulated wastewater is introduced into the above two groups of reaction columns and stable operation for 7 days, the effluent water samples are collected; the concentrations of Fe 3+ , Mn 2+ , Tl + , Cd 2+ , and Cr 6+ in the effluent are detected by atomic absorption spectrophotometry, and the removal rates are calculated; the heavy metal removal rates are detected once a month for 3 months to verify the long-term performance.

[0065] The specific experimental results are shown in the following table, heavy metal removal performance (stable operation for 7 days):

[0066] Heavy metal ions Concentration in influent (mg / L) Concentration in effluent in experimental group (mg / L) Concentration in effluent in control group (mg / L) Removal rate in experimental group (%) Removal rate in control group (%) Fe 3+ ]]> 50 0.25±0.03 1.5±0.1 99.5 97.0 Mn 2+ ]] 20 0.3±0.05 3.2±0.2 98.5 84.0 Tl + ]]> 0.5 0.005±0.001 0.15±0.02 99.0 70.0 Cd 2+ ]]> 1 0.01±0.002 0.2±0.03 99.0 80.0 Cr 6+ ]]> 2 0.05±0.005 0.5±0.04 97.5 75.0

[0067] After continuous operation for 3 months, the removal rates of each heavy metal in the experimental group still remain greater than or equal to 95%, and the removal rates in the control group decrease to 60%-85%.

[0068] 3. Mechanical stability test:

[0069] 50 fillers of Example 2 are taken and placed in a beaker containing 10 L of deionized water, and stirred at 100 r / min for 30 days; the disintegration of the fillers is observed every day, and the un-disintegrated particles are sieved after the end of the test, and the integrity rate is calculated; the compressive strength of the fillers before and after soaking is tested by an electronic universal testing machine (10 fillers are tested in each group, and the average value is taken).

[0070] The specific experimental results are shown in the following table, mechanical stability:

[0071] Detection index Initial state After 30 days of soaking Filler completeness rate (%) - 98±1 Compressive strength (MPa) 5.2±0.3 4.8±0.2

[0072] The integrity rate of the traditional calcium oxide filler in the control group is only 65% after soaking for 7 days, the compressive strength decreases to 1.5±0.3 MPa, and obvious disintegration occurs.

[0073] 4. Sludge production test:

[0074] The core-shell structure alkaline slow-release filler prepared in Example 2 of the present application and the traditional single calcium oxide filler are respectively used to treat 100 L of simulated acid mine wastewater (pH = 3.5, containing Fe 3+ 50 mg / L, Mn 2+ 20 mg / L, Tl +0.5 mg / L, Cd 2+ 1 mg / L, Cr 6+ 2 mg / L) was neutralized, and after the reaction was completely terminated, the mixed system was left to stand for 24 h to allow the solid-phase product generated by the reaction to fully settle. Subsequently, quantitative filter paper (pore size 0.45 pm) was used to perform suction filtration on the system, the entire filter residue was collected and transferred to a constant temperature drying oven, dried at 105°C until the constant weight (continuous 2 times weighing difference ≤0.1 g), the dry weight of the sludge was weighed by a high-precision electronic balance (accuracy 0.001 g), and finally the sludge production per unit volume of wastewater was calculated.

[0075] After the experimental group (core-shell structure filler) treated 100 L of simulated wastewater, the dry weight of the sludge was 125 ± 5 g, and the sludge production per unit volume of wastewater was 1.25 g / L. After the control group (traditional calcium oxide filler) treated the same volume of simulated wastewater, the dry weight of the sludge was 350 ± 10 g, and the sludge production per unit volume was 3.5 g / L. Calculation showed that the sludge production of the experimental group was reduced by 64.3% compared with the control group.

[0076] The core-shell structure alkaline slow-release filler, with its unique core-shell layered design and multi-component synergistic effect, exhibits excellent alkaline slow-release performance: the hydrophobic modified polymer of the outer shell and the nano diatomite microporous network can precisely control the release rate of the alkaline substance in the inner core, so that the pH value of acid mine wastewater can be stably maintained in the standard interval of 6-9 for more than 6 months, completely solving the technical pain point of traditional calcium oxide fillers, which have no slow-release barrier, resulting in a rapid increase in alkalinity in the early stage and a rapid decline in the later stage.

[0077] The filler can remove high-toxicity heavy metal ions such as Tl, Cd, Cr 6+ , which are difficult to remove by traditional methods, with a removal rate of more than 97.5%, and in a continuous 3-month long-term operation test, the heavy metal removal rate did not decrease significantly, and the long-term purification effect was significantly better than that of traditional single alkaline fillers. At the same time, the outer shell of the filler is formed by a dense structure of polyvinyl acetate-acrylic acid copolymer and nano diatomite, iron-manganese oxide modified attapulgite, with outstanding mechanical stability. After 30 days of water immersion test, there was no obvious disintegration or damage, the compressive strength decreased from 5.2 ± 0.3 MPa to 4.8 ± 0.2 MPa, with a decrease of only 7.7%, which can adapt to various dynamic water treatment conditions. In addition, due to the linear and slow release of the alkaline substance (calcium oxide + magnesium hydroxide) in the inner core, the neutralization reaction process is mild and controllable, avoiding the violent reaction and large amount of by-products generated by traditional methods due to the rapid release of alkalinity, ultimately reducing the sludge production by more than 60% compared with traditional neutralization methods, greatly reducing the sludge disposal cost and secondary pollution risk, and meeting the green environmental protection requirements of mine wastewater treatment.

[0078] The foregoing merely illustrates some exemplary embodiments of the application, and it will be appreciated that those skilled in the art will be able to devise various modifications without departing from the spirit and scope of the application. The appended drawings and description are illustrative only, and are not intended to be limiting.

Claims

1. An alkaline slow-release packing for neutralizing acid mine drainage, characterized in that, The filler is a core-shell structure with a particle size of 5-15 mm, including an inner core and an outer shell, and the mass of the outer shell is 10-15% of the mass of the inner core; The inner core raw material includes, by weight fraction, 25-40 parts of calcium oxide, 15-25 parts of magnesium hydroxide, 5-10 parts of sulfide, 8-15 parts of pore-forming agent, 3-8 parts of treatment agent, and 1-3 parts of deionized water; The outer shell raw material includes, by weight fraction, 20-30 parts of hydrophobically modified water-based polymer, 10-18 parts of nano diatomite, 12-20 parts of iron-manganese oxide modified attapulgite, 1-2 parts of dispersant, and 30-40 parts of deionized water.

2. The alkaline slow release infill for neutralizing acid mine drainage water as claimed in claim 1, wherein, The treatment agent is a composite powder of ferrous sulfide and hydroxyapatite, and the mass ratio of ferrous sulfide to hydroxyapatite is 1-2:

1.

3. An alkaline slow release filler for neutralizing acid mine drainage water as claimed in claim 2, wherein, The outer shell has a microporous network structure with a pore size ranging from 0.1 to 1 μm.

4. The alkaline slow release infill for neutralizing acid mine drainage water according to claim 3, characterized in that, The pore-forming agent is at least one of NaCl crystals, sucrose, and starch, with a particle size of 100-200 mesh; the sulfide is at least one of sodium sulfide, potassium sulfide, and calcium sulfide.

5. An alkaline slow release filler for neutralizing acid mine drainage water as claimed in claim 4, wherein, The hydrophobically modified water-based polymer is polyvinyl acetate-acrylic acid copolymer; and the dispersant is sodium dodecyl benzene sulfonate or polyethylene glycol.

6. A method for preparing an alkaline slow-release packing for neutralizing acid mine drainage, characterized by, It is suitable for preparing the alkaline slow-release filler for neutralizing acidic mine wastewater according to claim 5, comprising the following steps: S1, the mass fraction of calcium oxide, magnesium hydroxide, sulfide, pore-forming agent and treatment agent is taken, and the mixture is dry-mixed in a mixer at a speed of 300-500 r / min for 30 minutes, then deionized water is added and mixed for another 5-8 minutes to obtain inner core wet particles with a moisture content of 15-20%, and the inner core wet particles are dried at 60-80°C for 2 hours to obtain solidified inner core particles; S2, the attapulgite is calcined at 500-600°C for 2-3h, then added to the iron-manganese mixed salt solution, adjusted to pH 7.5-8.5, stirred at constant temperature 60-70°C for 4-6h, filtered, washed, dried at 80-100°C to constant weight, ground to 200-300 mesh to obtain iron-manganese oxide modified attapulgite; S3, the polyvinyl acetate-acrylic acid copolymer, nano diatomite, iron-manganese oxide modified attapulgite, dispersant and deionized water are placed in a high-speed disperser and dispersed at a speed of 800-1000 r / min for 30-40 min to obtain a composite shell slurry; S4, the solidified inner core particles are placed in a fluidized bed coater, and the composite shell slurry is sprayed to obtain coated particles; S5, the coated particles are first dried at 80-90°C for 2 hours, then solidified at 95-100°C for 1 hour, cooled to room temperature, and sieved to obtain alkaline slow-release filler with a particle size of 5-15 mm.

7. A process for the preparation of an alkaline slow release filler for neutralizing acid mine drainage water as claimed in claim 6, wherein, In the iron-manganese mixed salt solution described in S2, Fe 3+ The concentration is 0.1-0.2 mol / L, Mn 2+ The concentration is 0.05-0.1 mol / L.

8. A process for the preparation of an alkaline slow release filler for neutralizing acid mine drainage water as claimed in claim 6, wherein, The inlet air temperature of the fluidized bed coater in S4 is 40-50°C, the atomization pressure is 0.2-0.4 MPa, and the bed temperature is 35-40°C; the coated particles in S4 have an outer shell with a mass of 10-15% of the mass of the inner core.

9. A process for the preparation of an alkaline slow release filler for neutralizing acid mine drainage water as claimed in claim 6, wherein, The nozzle pressure is 0.2-0.5 MPa and the bed temperature is 60-80°C when the composite shell slurry is sprayed in S4.

10. A process for the preparation of an alkaline slow release filler for neutralizing acid mine drainage water as claimed in claim 6, wherein, The environment humidity during solidification for 1 hour in S5 is ≤40%RH.

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