Lead-zinc-manganese tailing heavy metal ion curing product and curing method

Abstract

The invention discloses a lead-zinc-manganese tailing heavy metal ion curing product and a curing method, and belongs to the technical field of heavy metal tailing treatment. The curing product comprises basic magnesium sulfate cement and acid-sensitive microcapsules; the acid-sensitive microcapsule is prepared by coating a compound microorganism functional system with Ca < 2 + > cross-linked sodium alginate; the composite microbial functional system comprises a bacterial suspension, quaternized chitosan and organic modified nano clay; the bacterial suspension comprises a microbial strain and EPS secreted by the microbial strain. The method has the advantages of being green, controllable and suitable for on-site in-situ treatment and building material recycling.

Description

Technical Field

[0001] The present invention belongs to the technical field of heavy metal tailings treatment, relates to a heavy metal tailings treatment method, and in particular to a lead, zinc and manganese tailings heavy metal ion solidification product and a solidification method. Background Art

[0002] Heavy metal pollution has become a global environmental concern, particularly in the mining, beneficiation, and smelting processes of non-ferrous metal ores. Lead and zinc ores in my country are generally of low grade, with lead and zinc contents typically less than 2.0%. Therefore, flotation is required to improve the grade. However, this process produces a large amount of tailings, which account for over 98% of the total raw ore, posing enormous pressure for their treatment and disposal. Currently, tailings are mostly stored in slag ponds, which not only consume significant land resources but also pose safety and environmental risks such as dam failure and heavy metal leaching. Once heavy metal ions enter surrounding water bodies and soil, they pose a serious threat to the ecological environment and the health of residents.

[0003] Lead-zinc ore tailings have a complex composition, mainly containing CaO (up to 50-52%), SiO2, Fe2O3, Al2O3, MgO and other inorganic mineral components, and are also enriched with various heavy metal ions such as Cu, Pb, Zn, Cr, Cd, etc., which are highly toxic and mobile. Similar problems are also widely found in manganese mining areas. As high-grade ores are gradually depleted, low-grade manganese tailings are piled up in large quantities, with an annual growth rate of millions of tons. 2+ The concentration far exceeds the soil background value, and the problem of heavy metal pollution is becoming increasingly serious.

[0004] Tailings solidification treatment technology fixes heavy metal ions in insoluble, stable structures through physical or chemical reactions, thereby reducing their activity and mobility. It is widely used for the safe disposal and reuse of tailings resources. Currently, commonly used solidification methods include cement solidification, asphalt solidification, polymer solidification, geopolymer solidification, and their combination. Cement solidification technology is widely adopted due to its relatively low cost and mature process. Its basic mechanism is to encapsulate tailings particles or precipitate and fix heavy metal ions through hydration products. However, its solidification depth is limited and it is easily affected by impurities in the tailings, posing a certain risk of secondary release.

[0005] For example, patent ZL 201710706558.5 discloses a method for making bricks by mixing tailings sand with ordinary Portland cement. Although the process is simple, its heavy metal solidification ability is insufficient and the long-term stability of the product is poor. For another example, the autoclaved asphalt tailings brick process disclosed in ZL201410570689.1 improves some performance, but the equipment investment is large, the process is complex, and there are environmental risks such as the release of volatile organic compounds (VOCs), which is not conducive to promotion and application.

[0006] Therefore, developing a new curing technology has important application value. Summary of the Invention

[0007] The present invention provides a lead-zinc-manganese tailings heavy metal ion solidification product and a solidification method, so as to overcome the defects of the prior art.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] In the first aspect, the present invention provides a lead-zinc-manganese tailings heavy metal ion solidification product, comprising basic magnesium sulfate cement (BMSC) and acid-sensitive microcapsules; the acid-sensitive microcapsules are 2+ A cross-linked sodium alginate-coated composite microbial functional system is prepared; the composite microbial functional system includes a bacterial suspension, quaternized chitosan (QCS) and organically modified nanoclay (OMNC); the bacterial suspension includes a microbial strain and EPS (exopolysaccharide) secreted by the strain.

[0010] To optimize the above technical solutions, specific measures taken also include:

[0011] Furthermore, the preparation method of the bacterial suspension includes the following steps: S1, inoculating the microbial strain into a modified Luria-Bertani medium, culturing to the logarithmic growth phase, filtering, centrifuging, and obtaining a bacterial liquid; S2, inoculating the bacterial liquid obtained in S1 into an inorganic salt medium containing lead, zinc, and manganese ions, using a gradient increasing acclimation method to perform heavy metal tolerance acclimation culture, filtering, centrifuging, and obtaining a dominant bacterial liquid; S3, adding an inducer to the dominant bacterial liquid for expansion to obtain the bacterial suspension.

[0012] Furthermore, in S1 of the bacterial suspension preparation method, the modified Luria-Bertani medium includes 4-6 g / L yeast extract, 8-12 g / L peptone, 8-12 g / L glucose, 8-12 g / L sodium chloride, 0.5-1.5 g / L dipotassium hydrogen phosphate, 0.2-0.8 g / L potassium dihydrogen phosphate, 0.1-0.5 g / L magnesium sulfate (MgSO4·7H2O), 0.01-0.05 g / L ferrous sulfate (FeSO4·7H2O), 0.01-0.05 g / L calcium chloride (CaCl2·2H2O) and water; the culture conditions are: 28-32°C, 150-200 r / min shaking incubator for 44-50 hours;

[0013] After S1 culture, the EPS secretion can reach 120-150 mg / L, and the cell density OD 600The specific method of filtration and centrifugation after the culture is completed is as follows: filtering through four layers of sterile gauze and a 100 μm filter to remove bacterial aggregates and suspended impurities, centrifuging at 3000 rpm for 10 minutes to settle bacterial aggregates and precipitate, and taking the supernatant as the bacterial solution;

[0014] In S2, the inorganic salt culture medium includes 1500-1800 mg / L of ammonium nitrate, 1800-2000 mg / L of potassium nitrate, 150-200 mg / L of potassium dihydrogen phosphate, 400-500 mg / L of calcium chloride (CaCl2·2H2O), 350-400 mg / L of magnesium sulfate heptahydrate (MgSO4·7H2O), and water; the initial concentration of lead ions is 8-12 mg / L, the initial concentration of zinc ions is 3-7 mg / L, and the initial concentration of manganese ions is 1-5 mg / L; the acclimation culture conditions are 28-30°C, static culture or shaking culture at 50-70 r / min for 48-72 hours per cycle, and continuous culture for 5-10 cycles, with the concentrations of lead, zinc, and manganese ions increasing by 10-20% in each cycle;

[0015] The specific methods of filtration and centrifugation after S2 acclimation and cultivation are the same as those in S1;

[0016] In S3, the inducer is one or more of trehalose, fructose, and chitosan oligosaccharide, and the addition amount is 0.1-0.3% (w / v); the expansion time is 20-30h;

[0017] After S3 expansion, EPS production increased by more than 40%, and the cell density OD 600 >1.5, under scanning electron microscopy, the thickness of the EPS layer on the strain surface was above 800 nm, and the Zeta potential was above -25 mV.

[0018] Furthermore, the microbial strain is one or more of Bacillus pasteurianus, Bacillus mucilaginosus, Desulfovibrio, Bacillus polymyxa, Bacillus subtilis, and Staphylococcus epidermidis.

[0019] Furthermore, the preparation method of the quaternized chitosan is as follows: dissolving chitosan in an acetic acid solution to obtain a chitosan solution; slowly adding 2,3-epoxypropyltrimethylammonium chloride (GTMAC) dropwise, reacting at 40-60° C. for 7-9 hours; adjusting the pH to neutral, adding ethanol, allowing to stand, and drying the precipitate to obtain the quaternized chitosan;

[0020] The chitosan is chitosan with a deacetylation degree of ≥90%; the concentration of the acetic acid solution is 1-3% (v / v); the concentration of the chitosan solution is 1-3% (w / v); and the mass ratio of 2,3-epoxypropyltrimethylammonium chloride to chitosan is 1:2-5.

[0021] The substitution degree of the obtained quaternized chitosan is 60-70% as determined by nuclear magnetic resonance, and the molecular weight is 50,000-100,000 as determined by gel permeation chromatography.

[0022] Furthermore, the preparation method of the organic modified nanoclay is as follows: dispersing sodium bentonite in water to obtain a suspension; stirring at 50-70° C. and slowly adding a cetyltrimethylammonium bromide (CTAB) solution; reacting for 1.5-2.5 hours, centrifuging, washing with water until there is no bromide ion (detected by AgNO3), drying and grinding, and passing through a 200-mesh sieve to obtain the organic modified nanoclay;

[0023] The cation exchange capacity (CEC) of the sodium bentonite is 80-100 mmol / 100 g; the concentration of the suspension is 3-7% (w / v); and the amount of cetyltrimethylammonium bromide added is 1-2 times the cation exchange capacity.

[0024] The interlayer spacing of organic modified nanoclay is ≥3.5nm and the specific surface area is ≥800m 2 / g.

[0025] Furthermore, the preparation method of the acid-sensitive microcapsules is as follows: the composite microbial functional system is uniformly mixed with a sodium alginate solution to form an aqueous phase; the aqueous phase is dripped into a CaCl2 solution by a dropwise method, and stirred to form spherical calcium alginate gel microcapsules; after the colloid is stabilized, sodium carboxymethyl cellulose is added to adjust the viscosity to 50-100 mPa·s, sterilized by passing through a 0.45 μm filter membrane, and centrifuged to obtain the acid-sensitive microcapsules;

[0026] In the composite microbial functional system, the mass ratio of quaternized chitosan to organically modified nanoclay is 1-3:1, the amount of bacterial suspension added is 5-15% of the total mass of the composite microbial functional system; the concentration of the sodium alginate solution is 1-3% (w / v); the volume ratio of the composite microbial functional system to the sodium alginate solution is 1:1-3; the concentration of the CaCl2 solution is 3-7% (w / v); the stirring condition is 250-350 rpm; and the amount of sodium carboxymethyl cellulose added is 0.1-0.3% (w / v).

[0027] The particle size of the finally obtained acid-sensitive microcapsules is 300 to 500 μm.

[0028] In a second aspect, the present invention also provides a method for solidifying heavy metal ions in lead, zinc and manganese tailings using the above-mentioned solidified product, adding the basic magnesium sulfate cement, acid-sensitive microcapsules and water to the tailings to be treated, stirring evenly to form a slurry; pouring the slurry into a mold or an underground mine, and vibrating the slurry using an inserted vibrating rod or a flat vibrator to ensure density, and solidifying in a natural environment; covering the solidified body with a straw bag or film and naturally curing it.

[0029] To optimize the above technical solutions, specific measures taken also include:

[0030] Furthermore, the tailings are one or more of lead tailings, zinc tailings, and manganese tailings; the tailings are first crushed or ground to a particle size of less than 0.16 mm, and then the slurry is prepared;

[0031] The basic magnesium sulfate cement comprises magnesium oxide, magnesium sulfate heptahydrate and an organic acid salt admixture; the magnesium oxide is produced by calcining industrial by-product magnesium hydroxide at 700-900° C., and the active magnesium oxide content is 50-80%; the molar ratio of magnesium oxide to magnesium sulfate heptahydrate is 4-10:1; the organic acid salt admixture is one or more of tartaric acid, citric acid and sodium gluconate, and the added amount is 0.1-2% of the mass of the magnesium oxide;

[0032] The mass ratio of tailings, basic magnesium sulfate cement and water is 50-300:100:30-100, and the dosage of acid-sensitive microcapsules is 5-10% of the mass of basic magnesium sulfate cement.

[0033] Furthermore, the stirring conditions are 300-800 r / min and the time is 3-10 min; the natural curing time is at least 3-14 days; and the solidified body is used to fill abandoned mines, make drainage ditch slope protection boards or tailings pond landfill reclamation projects.

[0034] The beneficial effects of the present invention are as follows: the present invention provides a lead, zinc and manganese tailings heavy metal ion solidification product and solidification method, by performing heavy metal gradient acclimation and induction enhancement on the high-efficiency EPS secretion strain, compounding it with quaternized chitosan and organic modified nanoclay, and using sodium alginate-Ca 2+ Acid-sensitive microcapsules were prepared by gel system and added into BMSC and tailings slurry to achieve delayed release and targeted response under the pH evolution and pollutant release conditions of cement hydration process, and synergistically complete the adsorption, complexation, precipitation and crystal wrapping of heavy metal ions, thereby achieving the purpose of Pb in tailings. 2+ 、Zn 2+ 、Mn 2+ It can effectively, stably and long-term solidify harmful ions, and has the advantages of being green, controllable, and suitable for on-site treatment and resource utilization of building materials.

[0035] Specifically, the first stage of the curing method is the initial hydration induction period (0 to 6 hours), during which magnesium oxide rapidly hydrates, the cement pH rises sharply to 12 to 13, and SO4 2- The ions are completely dissolved, the heavy metals in the tailings are not released in large quantities, the acid-sensitive microcapsules are closed, and the system is in a high-alkaline unstable stage. Specifically, magnesium oxide rapidly hydrates and releases OH-, causing the pH of the system to rise to 12-13, providing an alkaline environment to induce the subsequent formation of 5·1·7 crystals; the physical dissolution of magnesium sulfate heptahydrate leads to SO42- The ions are completely dissolved, providing ion precursors for subsequent crystallization and adjusting the early ionic strength; organic acid salt admixtures and Mg 2+ Forming complexes, controlling the rapid precipitation of Mg(OH)2, reducing the risk of local supersaturation, delaying premature hydration, optimizing crystal size distribution, and partially complexing Pb 2+ / Zn 2+ , initial slow release of heavy metal activity; Pb in tailings 2+ 、Zn 2+ 、Mn 2+ It mainly exists in the form of low-solubility minerals such as carbonates, sulfides, and oxides. In the initial high-alkaline environment (pH>12), heavy metal ions are prompted to form hydroxide precipitation. Therefore, the concentration of free heavy metal ions is extremely low and will not induce the release of acid-sensitive microcapsules, providing a delayed protection window for microorganisms; Sodium alginate-Ca 2+ Cross-linking forms a shell structure that is dense and stable in a high alkaline environment, protecting the microbial strains inside.

[0036] The second stage of the solidification method is the crystal formation-cementation nucleation period (6 hours to 3 days). During this stage, the pH drops to 10-11, 5·1·7 crystals are gradually generated, heavy metal ions in local areas are slowly released, microcapsules are locally ruptured, and the composite microbial functional system starts to respond. Specifically, BMSC hydrates to form needle-rod-shaped 5·1·7 crystals, which constitute a primary structural framework. This framework wraps the tailings and organic acid salt admixtures, enhancing the stability of the interface structure. However, in the boundary area where the crystal wrapping is incomplete and pore water is retained, the heavy metals in the tailings are slowly dissolved due to the decrease in micro-region pH and the complexation of organic acids, releasing free ions, resulting in local enrichment of heavy metals. The replacement of heavy metal ions in the microcapsules triggers the rupture of acid-sensitive microcapsules, releasing the composite microbial functional system. The microbial strains in the composite microbial functional system secrete EPS, which can adsorb heavy metal ions. At the same time, the metabolic product CO2 of the microbial strain generates CO3 in an alkaline environment. 2- , reacts with heavy metal ions to form carbonate precipitates; QCS reacts with Pb(OH)3 - The anions combine to form a flocculant complex, providing an attachment interface for microbial strains and enhancing the cement interface adhesion; OMNC undergoes ion exchange adsorption with heavy metal ions, improving the density of the slurry and regulating the micromorphology of the hydration structure.

[0037] The third stage of the solidification method is the structural density-long-term consolidation period (3 to 28 days). During this stage, the pH is stabilized at 8 to 9, the crystal skeleton network matures, the microbial strains are fully activated, and the composite microbial functional system reacts synergistically to form multiple fixed structures. Specifically, the 5·1·7 crystals continue to grow and intertwine and wrap the tailings and reaction residues to form a dense mineralized skeleton, effectively sealing heavy metal ions. At the same time, the crystal lattice will embed some heavy metal ions; the microbial strains secrete a large amount of EPS to form bio-micelles and chelate heavy metals, while continuously generating CO3 2- Heavy metals are precipitated, and the microbial-EPS mineralized network structure can enhance the anti-permeability and sealing performance; QCS and EPS synergistically cross-link to enhance the structural adhesion, density and stability, while EPS continues to chelate residual heavy metal ions to improve long-term anti-leaching performance; OMNC is fixed on the crystal surface or in the gaps, continuously adsorbing residual heavy metal ions, forming a "physical blocking + ion interception" double-layer defense line; the remaining shells of acid-sensitive microcapsules participate in pore filling and promote interface micro-repair. At the same time, water infiltration in the crack area will also activate the microbial strains, which secrete colloids and mineral precipitation to fill the cracks, achieve "secondary self-healing" and restore structural stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a flow chart of the preparation and solidification method of the lead-zinc-manganese tailings heavy metal ion solidification product of the present invention. DETAILED DESCRIPTION

[0039] The present invention will be further described below with reference to specific embodiments.

[0040] Example 1

[0041] This embodiment provides a lead-zinc-manganese tailings heavy metal ion solidification product and solidification method. The preparation and solidification methods of the solidified product are as follows:

[0042] (1) Cultivation of microbial strains: Bacillus subtilis was selected and inoculated into a modified Luria-Bertani medium (yeast extract: 4 g / L, peptone: 10 g / L, glucose: 8 g / L, sodium chloride: 10 g / L, dipotassium hydrogen phosphate: 1 g / L, potassium dihydrogen phosphate: 0.2 g / L, magnesium sulfate (MgSO4·7H2O): 0.1 g / L, ferrous sulfate (FeSO4·7H2O): 0.01 g / L, calcium chloride (CaCl2·2H2O): 0.01 g / L). The culture was carried out at 30±2°C and 180 r / min in a shaking incubator for 48 h to allow the strain to enter the logarithmic growth phase. At this time, the exopolysaccharide secretion amount could reach 140 mg / L, and the bacterial density OD 600The concentration of the culture medium was about 0.8. After the culture was completed, the bacterial solution was filtered through four layers of sterile gauze and a 100 μm filter to remove bacterial clumps and suspended impurities. The bacterial clumps and precipitates were then precipitated at 3000 rpm for 10 minutes, and the supernatant was taken for later use.

[0043] (2) Acclimation of dominant bacteria, expansion and induction of EPS secretion: The bacterial solution obtained in step (1) was inoculated into a culture medium containing inorganic salts and heavy metal ions (ammonium nitrate: 1600 mg / L, potassium nitrate: 1800 mg / L, potassium dihydrogen phosphate: 165 mg / L, calcium chloride (CaCl2·2H2O): 400 mg / L, magnesium sulfate heptahydrate: (MgSO4·7H2O): 360 mg / L), and the initial concentration was set to 10 mg / L Pb 2+ 、5mg / L Zn 2+ 、3mg / L Mn 2+ , heavy metal tolerance domestication was performed using a gradient incremental domestication method. Each domestication cycle was 72h. After the bacteria grew stably, the concentrations of the three heavy metal ions were increased by about 15% (±5%), and 8 rounds were performed continuously. The culture temperature of the entire domestication process was controlled at 30±2°C, and the process was carried out under low-speed oscillation (60r / min). The strains were filtered and centrifuged using the same method as step (1), and finally the dominant strains with high EPS production capacity in a high-concentration heavy metal system were screened. After the domestication was completed, 0.1% (w / v) fructose was added to the bacterial solution, and the culture was continued for 24h to further stimulate the EPS metabolic pathway, thereby increasing the EPS secretion by 45% and obtaining a high-concentration bacterial suspension (OD 600 =1.2).

[0044] (3) Chitosan with a deacetylation degree of 90% was dissolved in a 2% (v / v) acetic acid solution to prepare a 2% (w / v) chitosan solution. 2,3-Epoxypropyltrimethylammonium chloride was then slowly added dropwise at a mass ratio of 1:2 to chitosan. The mixture was reacted at 50°C for 8 h. After the reaction, the pH was adjusted to neutral with a NaOH solution, precipitated with ethanol, and dried under vacuum to obtain quaternized chitosan. The degree of substitution was determined to be 66% by nuclear magnetic resonance, and the molecular weight was determined to be 80,000 by gel permeation chromatography.

[0045] (4) 50 g of sodium bentonite (CEC = 80 mmol / 100 g) was dispersed in 1 L of deionized water (5% w / v) and stirred at 60°C for 30 min. Cetyltrimethylammonium bromide (CTAB, the amount added was 1.2 times that of CEC) was slowly added and stirred for 2 h. After centrifugation (3000 rpm, 10 min), the mixture was washed with water three times (until there was no white precipitate when AgNO3 was added to the filtrate), dried at 60°C for 12 h, and ground through a 200 mesh sieve to obtain a granular material with an interlayer spacing of 3.5 nm and a specific surface area of ​​800 m 2 / g of organically modified nanoclay.

[0046] (5) Construction of a composite microbial functional system: A high-concentration bacterial suspension was mixed with quaternized chitosan and organically modified nanoclay (the mass ratio of quaternized chitosan to organically modified nanoclay was 1:1, and the amount of bacterial suspension added was 10% of the total system) to form a composite microbial functional system. The composite system was then mixed evenly with a 2% (w / v) sodium alginate solution at a volume ratio of 1:1 to form an aqueous phase. The mixed solution was dripped into a 5% (w / v) CaCl2 solution using a dropwise method. The mixture was stirred at 300 rpm magnetically to form spherical calcium alginate gel microcapsules. After the colloid stabilized, 0.1% (w / v) sodium carboxymethyl cellulose was added to adjust the viscosity to 80 mPa·s. The microcapsules were sterilized by passing through a 0.45 μm filter membrane and collected by centrifugation to form acid-sensitive microcapsules with a particle size of 450 μm.

[0047] (6) Tailings pretreatment: crush or grind the lead-zinc-manganese tailings (mass ratio of 3:1:2) and take 200 parts of the lead-zinc-manganese tailings by mass.

[0048] (7) Preparation of solidified slurry: 100 parts of basic magnesium sulfate cement (the molar ratio of magnesium oxide to magnesium sulfate heptahydrate is 4:1, and the amount of tartaric acid added is 0.5% of the mass of magnesium oxide) and 60 parts of water are added to the pretreated tailings. Acid-sensitive microcapsules are added at 8% of the mass of cement. The mixture is stirred in a twin-shaft mixer for 5 minutes at a speed of 500 r / min to form a uniform slurry.

[0049] (8) Molding and curing: Pour the evenly stirred mixed slurry into a pre-prepared mold or underground mine, vibrate the slurry with an inserted vibrating rod to ensure density, and solidify it in a natural environment.

[0050] (9) Curing: Cover the solidified body with straw bags and cure naturally for 12 days.

[0051] Example 2

[0052] This embodiment provides a lead-zinc-manganese tailings heavy metal ion solidification product and solidification method. The preparation and solidification methods of the solidified product are as follows:

[0053] (1) Cultivation of microbial strains: Bacillus subtilis and Desulfovibrio spp. (volume ratio of 1:1) were selected and inoculated into a modified Luria-Bertani medium (yeast extract: 5 g / L, peptone: 11 g / L, glucose: 10 g / L, sodium chloride: 12 g / L, dipotassium hydrogen phosphate: 0.8 g / L, potassium dihydrogen phosphate: 0.4 g / L, magnesium sulfate (MgSO4·7H2O): 0.2 g / L, ferrous sulfate (FeSO4·7H2O): 0.03 g / L, calcium chloride (CaCl2·2H2O): 0.04 g / L). The culture was carried out at 30±2°C and 180 r / min in a shaking incubator for 48 h to allow the strain to enter the logarithmic growth phase. At this time, the exopolysaccharide secretion amount could reach 145 mg / L and the bacterial density OD 600 The concentration of the culture medium was about 0.9. After the culture was completed, the bacterial solution was filtered through four layers of sterile gauze and a 100 μm filter to remove bacterial clumps and suspended impurities. The bacterial clumps and precipitates were then precipitated at 3000 rpm for 10 minutes, and the supernatant was taken for later use.

[0054] (2) Acclimation of dominant bacteria, expansion and induction of EPS secretion: The bacterial solution obtained in step (1) was inoculated into a culture medium containing inorganic salts and heavy metal ions (ammonium nitrate: 1700 mg / L, potassium nitrate: 1900 mg / L, potassium dihydrogen phosphate: 180 mg / L, calcium chloride (CaCl2·2H2O): 400 mg / L, magnesium sulfate heptahydrate: (MgSO4·7H2O): 360 mg / L), and the initial concentration was set to 10 mg / L Pb 2+ 、5mg / L Zn 2+ 、3mg / L Mn 2+ , heavy metal tolerance domestication was performed using a gradient increasing domestication method. Each domestication cycle was 72h. After the bacteria grew stably, the concentrations of the three heavy metal ions were increased by about 15% (±5%) respectively, and this was repeated for 5 rounds. The culture temperature of the entire domestication process was controlled at 30±2°C, and the process was carried out under low-speed oscillation (60r / min). The strains were filtered and centrifuged using the same method as step (1), and finally the dominant strains with high EPS production capacity in a high-concentration heavy metal system were screened. After the domestication was completed, 0.2% (w / v) trehalose was added to the bacterial solution, and the culture was continued for 24h to further stimulate the EPS metabolic pathway, thereby increasing the EPS secretion by 50%, and obtaining a high-concentration bacterial suspension (OD 600 =1.2).

[0055] (3) Chitosan with a deacetylation degree of 93% was dissolved in a 2% (v / v) acetic acid solution to prepare a 2% (w / v) chitosan solution. 2,3-Epoxypropyltrimethylammonium chloride was then slowly added dropwise at a mass ratio of 1:3 to chitosan. The mixture was reacted at 50°C for 8 h. After the reaction, the pH was adjusted to neutral with a NaOH solution, precipitated with ethanol, and dried under vacuum to obtain quaternized chitosan. The degree of substitution was determined to be 63% by nuclear magnetic resonance, and the molecular weight was determined to be 92,000 by gel permeation chromatography.

[0056] (4) 50 g of sodium bentonite (CEC = 85 mmol / 100 g) was dispersed in 1 L of deionized water (5% w / v) and stirred at 60 ° C for 30 min; hexadecyltrimethylammonium bromide (CTAB, the amount added was 1.5 times that of CEC) was slowly added and stirred for 2 h; centrifuged (3000 rpm, 10 min) and washed with water three times (until there was no white precipitate when AgNO3 was added to the filtrate), dried at 60 ° C for 12 h, and ground through a 200 mesh sieve to obtain a granular material with an interlayer spacing of 4.2 nm and a specific surface area of ​​850 m 2 / g of organically modified nanoclay.

[0057] (5) Construction of a composite microbial functional system: A high-concentration bacterial suspension was mixed with quaternized chitosan and organically modified nanoclay (the mass ratio of quaternized chitosan to organically modified nanoclay was 2:1, and the amount of bacterial suspension added was 15% of the total system) to form a composite microbial functional system. The composite system was then mixed evenly with a 2% (w / v) sodium alginate solution at a volume ratio of 1:1 to form an aqueous phase. The mixture was dripped into a 5% (w / v) CaCl2 solution using a dropwise method. The mixture was stirred at 300 rpm magnetically to form spherical calcium alginate gel microcapsules. After the colloid stabilized, 0.1% (w / v) sodium carboxymethyl cellulose was added to adjust the viscosity to 80 mPa·s. The microcapsules were sterilized by passing through a 0.45 μm filter membrane and collected by centrifugation to form acid-sensitive microcapsules with a particle size of 450 μm.

[0058] (6) Tailings pretreatment: crush or grind the lead-zinc-manganese tailings (mass ratio of 3:1:2) and take 200 parts of the lead-zinc-manganese tailings by mass.

[0059] (7) Preparation of solidified slurry: 100 parts of basic magnesium sulfate cement (the molar ratio of magnesium oxide to magnesium sulfate heptahydrate is 7:1, and the amount of citric acid added is 1% of the mass of magnesium oxide) and 80 parts of water are added to the pretreated tailings, and acid-sensitive microcapsules are added at 7.5% of the mass of cement. The mixture is stirred in a twin-shaft mixer for 4 minutes at a speed of 450 r / min to form a uniform slurry.

[0060] (8) Molding and curing: Pour the evenly stirred mixed slurry into a pre-prepared mold or underground mine, vibrate the slurry with an inserted vibrating rod to ensure density, and solidify it in a natural environment.

[0061] (9) Curing: Cover the solidified body with straw bags and cure naturally for 12 days.

[0062] Example 3

[0063] This embodiment provides a lead-zinc-manganese tailings heavy metal ion solidification product and solidification method. The preparation and solidification methods of the solidified product are as follows:

[0064] (1) Culture of microbial strains: Bacillus polymyxa and Bacillus subtilis (volume ratio of 1:2) were selected and inoculated into a modified Luria-Bertani medium (yeast extract: 6 g / L, peptone: 11.5 g / L, glucose: 11 g / L, sodium chloride: 10 g / L, dipotassium hydrogen phosphate: 0.8 g / L, potassium dihydrogen phosphate: 0.8 g / L, magnesium sulfate (MgSO4·7H2O): 0.4 g / L, ferrous sulfate (FeSO4·7H2O): 0.04 g / L, calcium chloride (CaCl2·2H2O): 0.04 g / L). The culture was carried out at 30±2°C and 180 r / min in a shaking incubator for 48 h to allow the strain to enter the logarithmic growth phase. At this time, the exopolysaccharide secretion amount could reach 145 mg / L and the bacterial density OD 600 The concentration of the culture medium was about 1.1. After the culture was completed, the bacterial solution was filtered through four layers of sterile gauze and a 100 μm filter to remove bacterial clumps and suspended impurities. The bacterial clumps and precipitates were then precipitated at 3000 rpm for 10 minutes, and the supernatant was taken for later use.

[0065] (2) Acclimation of dominant bacteria, expansion and induction of EPS secretion: The bacterial solution obtained in step (1) was inoculated into a culture medium containing inorganic salts and heavy metal ions (ammonium nitrate: 1800 mg / L, potassium nitrate: 2000 mg / L, potassium dihydrogen phosphate: 180 mg / L, calcium chloride (CaCl2·2H2O): 480 mg / L, magnesium sulfate heptahydrate: (MgSO4·7H2O): 380 mg / L), and the initial concentration was set to 10 mg / L Pb 2+ 、5mg / L Zn 2+ 、3mg / L Mn 2+, heavy metal tolerance domestication was performed using a gradient incremental domestication method. Each domestication cycle was 72h. After the bacteria grew stably, the concentrations of the three heavy metal ions were increased by about 15% (±5%), and 10 rounds were performed continuously. The culture temperature of the entire domestication process was controlled at 30±2°C, and the process was carried out under low-speed oscillation (60r / min). The strains were filtered and centrifuged using the same method as step (1), and finally the dominant strains with high EPS production capacity under high-concentration heavy metal systems were screened. After the domestication was completed, 0.3% (w / v) chitosan oligosaccharides were added to the bacterial solution, and the culture was continued for 24h to further stimulate the EPS metabolic pathway, thereby increasing the EPS secretion by 55% and obtaining a high-concentration bacterial suspension (OD 600 =1.9).

[0066] (3) Chitosan with a deacetylation degree of 95% was dissolved in a 2% (v / v) acetic acid solution to prepare a 2% (w / v) chitosan solution. 2,3-Epoxypropyltrimethylammonium chloride was then slowly added dropwise at a mass ratio of 1:4 to chitosan. The mixture was reacted at 50°C for 8 h. After the reaction, the pH was adjusted to neutral with a NaOH solution, precipitated with ethanol, and dried under vacuum to obtain quaternized chitosan. The degree of substitution was determined to be 65% by nuclear magnetic resonance, and the molecular weight was determined to be 90,000 by gel permeation chromatography.

[0067] (4) 50 g of sodium bentonite (CEC = 90 mmol / 100 g) was dispersed in 1 L of deionized water (5% w / v) and stirred at 60 ° C for 30 min; hexadecyltrimethylammonium bromide (CTAB, the addition amount is 1.8 times that of CEC) was slowly added and stirred for 2 h; centrifuged (3000 rpm, 10 min) and washed with water three times (until there is no white precipitate when AgNO3 is added to the filtrate), dried at 60 ° C for 12 h, and ground through a 200 mesh sieve to obtain a granular material with an interlayer spacing of 4.5 nm and a specific surface area of ​​900 m 2 / g of organically modified nanoclay.

[0068] (5) Construction of a composite microbial functional system: A high-concentration bacterial suspension was mixed with quaternized chitosan and organically modified nanoclay (the mass ratio of quaternized chitosan to organically modified nanoclay was 3:1, and the amount of bacterial suspension added was 5% of the total system) to form a composite microbial functional system. The composite system was then mixed evenly with a 2% (w / v) sodium alginate solution at a volume ratio of 1:1 to form an aqueous phase. The mixed solution was dripped into a 5% (w / v) CaCl2 solution using a dropwise method. The mixture was stirred at 300 rpm magnetically to form spherical calcium alginate gel microcapsules. After the colloid stabilized, 0.3% (w / v) sodium carboxymethyl cellulose was added to adjust the viscosity to 80 mPa·s. The microcapsules were sterilized by passing through a 0.45 μm filter membrane and collected by centrifugation to form acid-sensitive microcapsules with a particle size of 450 μm.

[0069] (6) Tailings pretreatment: crush or grind the lead-zinc-manganese tailings (mass ratio of 3:1:2) and take 250 parts of the lead-zinc-manganese tailings by mass.

[0070] (7) Preparation of solidified slurry: 100 parts of basic magnesium sulfate cement (the molar ratio of magnesium oxide to magnesium sulfate heptahydrate is 8:1, and the amount of tartaric acid added is 2% of the mass of magnesium oxide) and 90 parts of water are added to the pretreated tailings. Acid-sensitive microcapsules are added at a rate of 7.5% of the mass of cement. The mixture is stirred in a twin-shaft mixer for 7 minutes at a speed of 700 r / min to form a uniform slurry.

[0071] (8) Molding and curing: Pour the evenly stirred mixed slurry into a pre-prepared mold or underground mine, vibrate the slurry with a flat vibrator to ensure density, and solidify it in a natural environment.

[0072] (9) Curing: Cover the solidified body with straw bags and cure naturally for 14 days.

[0073] Example 4

[0074] This embodiment provides a lead-zinc-manganese tailings heavy metal ion solidification product and solidification method. The preparation and solidification methods of the solidified product are as follows:

[0075] (1) Culture of microbial strains: Staphylococcus epidermidis was selected and inoculated into a modified Luria-Bertani medium (yeast extract: 5 g / L, peptone: 12 g / L, glucose: 12 g / L, sodium chloride: 12 g / L, dipotassium hydrogen phosphate: 1.2 g / L, potassium dihydrogen phosphate: 0.6 g / L, magnesium sulfate (MgSO4·7H2O): 0.3 g / L, ferrous sulfate (FeSO4·7H2O): 0.05 g / L, calcium chloride (CaCl2·2H2O): 0.04 g / L). The culture was carried out at 30±2°C and 180 r / min in a shaking incubator for 48 h to allow the strain to enter the logarithmic growth phase. At this time, the exopolysaccharide secretion amount could reach 150 mg / L and the bacterial density OD 600 The concentration of the culture medium was about 1.0. After the culture was completed, the bacterial solution was filtered through four layers of sterile gauze and a 100 μm filter to remove bacterial clumps and suspended impurities. The bacterial clumps and precipitates were then precipitated at 3000 rpm for 10 minutes, and the supernatant was collected for later use.

[0076] (2) Acclimation of dominant bacteria, expansion and induction of EPS secretion: The bacterial solution obtained in step (1) was inoculated into a culture medium containing inorganic salts and heavy metal ions (ammonium nitrate: 1650 mg / L, potassium nitrate: 1850 mg / L, potassium dihydrogen phosphate: 185 mg / L, calcium chloride (CaCl2·2H2O): 460 mg / L, magnesium sulfate heptahydrate: (MgSO4·7H2O): 370 mg / L), and the initial concentration was set to 10 mg / L Pb2+ 、5mg / L Zn 2+ 、3mg / L Mn 2+ , heavy metal tolerance domestication was performed using a gradient increasing domestication method. Each domestication cycle was 72h. After the bacteria grew stably, the concentrations of the three heavy metal ions were increased by about 15% (±5%) respectively, and 9 rounds were performed continuously. The culture temperature of the entire domestication process was controlled at 30±2°C, and the process was carried out under low-speed oscillation (60r / min). The strains were filtered and centrifuged using the same method as step (1), and finally the dominant strains with high EPS production capacity in a high-concentration heavy metal system were screened. After the domestication was completed, 0.2% (w / v) trehalose and 0.1% (w / v) fructose were added to the bacterial solution, and the culture was continued for 24h to further stimulate the EPS metabolic pathway, thereby increasing the EPS secretion by 66% and obtaining a high-concentration bacterial suspension (OD 600 =1.8).

[0077] (3) Chitosan with a deacetylation degree of 90% was dissolved in a 2% (v / v) acetic acid solution to prepare a 2% (w / v) chitosan solution. 2,3-Epoxypropyltrimethylammonium chloride was then slowly added dropwise at a mass ratio of 1:2 to chitosan. The mixture was reacted at 50°C for 8 h. After the reaction, the pH was adjusted to neutral with a NaOH solution, precipitated with ethanol, and dried under vacuum to obtain quaternized chitosan. The degree of substitution was determined to be 62% by nuclear magnetic resonance, and the molecular weight was determined to be 60,000 by gel permeation chromatography.

[0078] (4) 50 g of sodium bentonite (CEC = 95 mmol / 100 g) was dispersed in 1 L of deionized water (5% w / v) and stirred at 60 ° C for 30 min; hexadecyltrimethylammonium bromide (CTAB, the addition amount is 1.5 times that of CEC) was slowly added and stirred for 2 h; centrifuged (3000 rpm, 10 min) and washed with water three times (until there is no white precipitate when AgNO3 is added to the filtrate), dried at 60 ° C for 12 h, and ground through a 200 mesh sieve to obtain a granular material with an interlayer spacing of 4 nm and a specific surface area of ​​820 m 2 / g of organically modified nanoclay.

[0079] (5) Construction of a composite microbial functional system: A high-concentration bacterial suspension was mixed with quaternized chitosan and organically modified nanoclay (the mass ratio of quaternized chitosan to organically modified nanoclay was 1.5:1, and the amount of bacterial suspension added was 12% of the total system) to form a composite microbial functional system. The composite system was then mixed evenly with a 2% (w / v) sodium alginate solution at a volume ratio of 1:1 to form an aqueous phase. The mixed solution was dripped into a 5% (w / v) CaCl2 solution using a dropwise method. The mixture was stirred at 300 rpm magnetically to form spherical calcium alginate gel microcapsules. After the colloid stabilized, 0.2% (w / v) sodium carboxymethyl cellulose was added to adjust the viscosity to 80 mPa·s. The microcapsules were sterilized by passing through a 0.45 μm filter membrane and collected by centrifugation to form acid-sensitive microcapsules with a particle size of 450 μm.

[0080] (6) Tailings pretreatment: crush or grind the lead-zinc-manganese tailings (mass ratio of 1:2:1) and take 180 parts of the lead-zinc-manganese tailings by mass.

[0081] (7) Preparation of solidified slurry: 100 parts of basic magnesium sulfate cement (the molar ratio of magnesium oxide to magnesium sulfate heptahydrate is 5:1, and the amount of citric acid added is 0.5% of the mass of magnesium oxide) and 70 parts of water are added to the pretreated tailings. Acid-sensitive microcapsules are added at 6% of the mass of cement. The mixture is stirred in a twin-shaft mixer for 8 minutes at a speed of 650 r / min to form a uniform slurry.

[0082] (8) Molding and curing: Pour the evenly stirred mixed slurry into a pre-prepared mold or underground mine, vibrate the slurry with an inserted vibrating rod to ensure density, and solidify it in a natural environment.

[0083] (9) Curing: Cover the solidified body with straw bags and cure naturally for 11 days.

[0084] Example 5

[0085] This embodiment provides a lead-zinc-manganese tailings heavy metal ion solidification product and solidification method. The preparation and solidification methods of the solidified product are as follows:

[0086] (1) Culture of microbial strains: Bacillus epipastoris, Bacillus mucilaginosus and Staphylococcus epidermidis (volume ratio of 1:1:1) were selected and inoculated into a modified Luria-Bertani medium (yeast extract: 6 g / L, peptone: 11 g / L, glucose: 10 g / L, sodium chloride: 12 g / L, dipotassium hydrogen phosphate: 0.7 g / L, potassium dihydrogen phosphate: 0.6 g / L, magnesium sulfate (MgSO4·7H2O): 0.3 g / L, ferrous sulfate (FeSO4·7H2O): 0.05 g / L, calcium chloride (CaCl2·2H2O): 0.05 g / L). The culture was carried out at 30±2℃ and 180 r / min in a shaking incubator for 48 h to allow the strain to enter the logarithmic growth phase. At this time, the exopolysaccharide secretion amount could reach 150 mg / L and the bacterial density OD 600 The concentration of the culture medium was about 1.2. After the culture was completed, the bacterial solution was filtered through four layers of sterile gauze and a 100 μm filter to remove bacterial clumps and suspended impurities. The bacterial clumps and precipitates were then precipitated at 3000 rpm for 10 minutes, and the supernatant was taken for later use.

[0087] (2) Acclimation of dominant bacteria, expansion and induction of EPS secretion: The bacterial solution obtained in step (1) was inoculated into a culture medium containing inorganic salts and heavy metal ions (ammonium nitrate: 180650 mg / L, potassium nitrate: 2000 mg / L, potassium dihydrogen phosphate: 200 mg / L, calcium chloride (CaCl2·2H2O): 500 mg / L, magnesium sulfate heptahydrate: (MgSO4·7H2O): 400 mg / L), and the initial concentration was set to 10 mg / L Pb. 2+ 、5mg / L Zn 2+ 、3mg / L Mn 2+ , heavy metal tolerance domestication was performed using a gradient increasing domestication method. Each domestication cycle was 72h. After the bacteria grew stably, the concentrations of the three heavy metal ions were increased by about 15% (±5%) respectively, and 7 rounds were performed continuously. The culture temperature of the entire domestication process was controlled at 30±2°C, and the process was carried out under low-speed oscillation (60r / min). The strains were filtered and centrifuged using the same method as step (1), and finally the dominant strains with high EPS production capacity in a high-concentration heavy metal system were screened. After the domestication was completed, 0.3% (w / v) trehalose was added to the bacterial solution, and the culture was continued for 24h to further stimulate the EPS metabolic pathway, thereby increasing the EPS secretion by 566% and obtaining a high-concentration bacterial suspension (OD 600 =1.87).

[0088] (3) Chitosan with a deacetylation degree of 90% was dissolved in a 2% (v / v) acetic acid solution to prepare a 2% (w / v) chitosan solution. 2,3-Epoxypropyltrimethylammonium chloride was then slowly added dropwise at a mass ratio of 1:5 to chitosan. The mixture was reacted at 50°C for 8 h. After the reaction, the pH was adjusted to neutral with a NaOH solution, precipitated with ethanol, and dried under vacuum to obtain quaternized chitosan. The degree of substitution was determined to be 60% by nuclear magnetic resonance, and the molecular weight was determined to be 60,000 by gel permeation chromatography.

[0089] (4) 50 g of sodium bentonite (CEC = 100 mmol / 100 g) was dispersed in 1 L of deionized water (5% w / v) and stirred at 60 °C for 30 min. Cetyltrimethylammonium bromide (CTAB, the amount added was twice that of CEC) was slowly added and stirred for 2 h. After centrifugation (3000 rpm, 10 min), the mixture was washed with water three times (until there was no white precipitate when AgNO3 was added to the filtrate), dried at 60 °C for 12 h, and ground through a 200 mesh sieve to obtain a granular material with an interlayer spacing of 5.5 nm and a specific surface area of ​​900 m 2 / g of organically modified nanoclay.

[0090] (5) Construction of a composite microbial functional system: A high-concentration bacterial suspension was mixed with quaternized chitosan and organically modified nanoclay (the mass ratio of quaternized chitosan to organically modified nanoclay was 1:2, and the amount of bacterial suspension added was 8% of the total system) to form a composite microbial functional system.

[0091] (6) Tailings pretreatment: crush or grind the lead-zinc-manganese tailings (mass ratio of 2:1:2) and take 200 parts of the lead-zinc-manganese tailings by mass.

[0092] (7) Preparation of solidified slurry: 130 parts of basic magnesium sulfate cement (the molar ratio of magnesium oxide to magnesium sulfate heptahydrate is 7:1, and the amount of sodium gluconate added is 1.5% of the mass of magnesium oxide) and 80 parts of water are added to the pretreated tailings, and the composite microbial functional system is added at 8% of the mass of cement. The mixture is stirred for 6 minutes at a speed of 550 r / min using a twin-shaft mixer to form a uniform slurry.

[0093] (8) Molding and curing: Pour the evenly stirred mixed slurry into a pre-prepared mold or underground mine, vibrate the slurry with an inserted vibrating rod to ensure density, and solidify it in a natural environment.

[0094] (9) Curing: Cover the solidified body with a film and allow it to cure naturally for 14 days.

[0095] Example 6

[0096] This embodiment provides a lead-zinc-manganese tailings heavy metal ion solidification product and solidification method. The preparation and solidification methods of the solidified product are as follows:

[0097] (1) Culture of microbial strains: Desulfovibrio spp. and Bacillus polymyxa were selected (volume ratio of 2:1) and inoculated into a modified Luria-Bertani medium (yeast extract: 8 g / L, peptone: 12 g / L, glucose: 10 g / L, sodium chloride: 11 g / L, dipotassium hydrogen phosphate: 0.9 g / L, potassium dihydrogen phosphate: 0.8 g / L, magnesium sulfate (MgSO4·7H2O): 0.4 g / L, ferrous sulfate (FeSO4·7H2O): 0.04 g / L, calcium chloride (CaCl2·2H2O): 0.05 g / L). Culture was carried out at 30±2°C and 180 r / min in a shaking incubator for 48 h to allow the strain to enter the logarithmic growth phase. At this time, the exopolysaccharide secretion amount could reach 160 mg / L and the bacterial density OD 600 The concentration of the culture medium was about 1.0. After the culture was completed, the bacterial solution was filtered through four layers of sterile gauze and a 100 μm filter to remove bacterial clumps and suspended impurities. The bacterial clumps and precipitates were then precipitated at 3000 rpm for 10 minutes, and the supernatant was collected for later use.

[0098] (2) Acclimation of dominant bacteria, expansion and induction of EPS secretion: The bacterial solution obtained in step (1) was inoculated into a culture medium containing inorganic salts and heavy metal ions (ammonium nitrate: 1900 mg / L, potassium nitrate: 1850 mg / L, potassium dihydrogen phosphate: 190 mg / L, calcium chloride (CaCl2·2H2O): 480 mg / L, magnesium sulfate heptahydrate: (MgSO4·7H2O): 380 mg / L), and the initial concentration was set to 10 mg / L Pb 2+ 、5mg / L Zn 2+ 、3mg / LMn 2+ , heavy metal tolerance domestication was performed using a gradient increasing domestication method. Each domestication cycle was 72h. After the bacteria grew stably, the concentrations of the three heavy metal ions were increased by about 15% (±5%) respectively, and 9 rounds were performed continuously. The culture temperature of the entire domestication process was controlled at 30±2°C, and the process was carried out under low-speed oscillation (60r / min). The strains were filtered and centrifuged using the same method as step (1), and finally the dominant strains with high EPS production capacity in a high-concentration heavy metal system were screened. After the domestication was completed, 0.15% (w / v) trehalose and 0.15% (w / v) chitosan oligosaccharides were added to the bacterial solution, and the culture was continued for 24h to further stimulate the EPS metabolic pathway, thereby increasing the EPS secretion by 60%, and obtaining a high-concentration bacterial suspension (OD 600 =1.8).

[0099] (3) Chitosan with a deacetylation degree of 98% was dissolved in a 2% (v / v) acetic acid solution to prepare a 2% (w / v) chitosan solution. 2,3-Epoxypropyltrimethylammonium chloride was then slowly added dropwise at a mass ratio of 1:5 to chitosan. The mixture was reacted at 50°C for 8 h. After the reaction, the pH was adjusted to neutral with a NaOH solution, precipitated with ethanol, and dried under vacuum to obtain quaternized chitosan. The degree of substitution was determined to be 60% by nuclear magnetic resonance, and the molecular weight was determined to be 70,000 by gel permeation chromatography.

[0100] (4) 50 g of sodium bentonite (CEC = 90 mmol / 100 g) was dispersed in 1 L of deionized water (5% w / v) and stirred at 60 ° C for 30 min; hexadecyltrimethylammonium bromide (CTAB, the addition amount was 1.8 times that of CEC) was slowly added and stirred for 2 h; centrifuged (3000 rpm, 10 min) and washed with water three times (until there was no white precipitate when AgNO3 was added to the filtrate), dried at 60 ° C for 12 h, and ground through a 200 mesh sieve to obtain a granular material with an interlayer spacing of 4.5 nm and a specific surface area of ​​880 m 2 / g of organically modified nanoclay.

[0101] (5) Construction of a composite microbial functional system: A high-concentration bacterial suspension was mixed with quaternized chitosan and organically modified nanoclay (the mass ratio of quaternized chitosan to organically modified nanoclay was 1:3, and the amount of bacterial suspension added was 10% of the total system) to form a composite microbial functional system. The composite system was then mixed evenly with a 2% (w / v) sodium alginate solution at a volume ratio of 1:1 to form an aqueous phase. The mixed solution was dripped into a 5% (w / v) CaCl2 solution using a dropwise method. The mixture was stirred at 300 rpm magnetically to form spherical calcium alginate gel microcapsules. After the colloid stabilized, 0.1% (w / v) sodium carboxymethyl cellulose was added to adjust the viscosity to 80 mPa·s. The microcapsules were sterilized by passing through a 0.45 μm filter membrane and collected by centrifugation to form acid-sensitive microcapsules with a particle size of 450 μm.

[0102] (6) Tailings pretreatment: crush or grind the lead-zinc-manganese tailings (mass ratio of 1:1:1) and take 150 parts of the lead-zinc-manganese tailings by mass.

[0103] (7) Preparation of solidified slurry: 100 parts of basic magnesium sulfate cement (the molar ratio of magnesium oxide to magnesium sulfate heptahydrate is 6:1, and the amount of tartaric acid and citric acid added is 1% of the mass of magnesium oxide) and 60 parts of water are added to the pretreated tailings. Acid-sensitive microcapsules are added at 9% of the mass of cement. The mixture is stirred in a twin-shaft mixer for 5 minutes at a speed of 550 r / min to form a uniform slurry.

[0104] (8) Molding and curing: Pour the evenly stirred mixed slurry into a pre-prepared mold or underground mine, vibrate the slurry with a flat vibrator to ensure density, and solidify it in a natural environment.

[0105] (9) Curing: Cover the solidified body with a film and allow it to cure naturally for 10 days.

[0106] Comparative Example 1

[0107] This comparative example provides a lead-zinc-manganese tailings heavy metal ion solidification product and solidification method. The preparation and solidification methods of the solidified product are as follows:

[0108] (1) Take 100 parts of lead tailings powder (mass ratio is 1:1:1) by mass and grind it to a particle size of less than 0.16 mm for later use.

[0109] (2) Add 100 parts of P.O42.5 ordinary Portland cement and 50 parts of water, mix them at one time, stir at a speed of 300 r / min, and stir for 3 minutes to prepare a slurry.

[0110] (3) Pour the slurry into the mold, vibrate it to make it dense using an inserted vibrating rod, and solidify it in a natural environment.

[0111] (4) Cover with straw bags and allow to cure naturally for 7 days.

[0112] Comparative Example 2

[0113] This comparative example provides a lead-zinc-manganese tailings heavy metal ion solidification product and solidification method. The preparation and solidification methods of the solidified product are as follows:

[0114] (1) 50 g of sodium bentonite (CEC = 80-100 mmol / 100 g) was dispersed in 1 L of deionized water (5% w / v) and stirred at 60 °C for 30 min. Hexadecyltrimethylammonium bromide (CTAB, 1.2 times the amount of CEC) was slowly added and stirred for 2 h. The mixture was centrifuged (3000 rpm, 10 min) and washed with water three times (until no white precipitate was obtained when AgNO3 was added to the filtrate). The mixture was dried at 60 °C for 12 h and ground through a 200 mesh sieve to obtain an organically modified nanoclay with an interlayer spacing of 3.5 nm. 0.3 L of the 10% (w / v) nanoclay suspension was directly taken.

[0115] (2) Grind 200 parts of zinc tailings powder to a particle size of less than 0.1 mm for later use.

[0116] (3) Add 100 parts of basic magnesium sulfate cement (the molar ratio of magnesium oxide to magnesium sulfate heptahydrate is 6:1, and the amount of sodium gluconate added is 1% of the mass of magnesium oxide), 70 parts of water, and 0.3 L of organic modified nanoclay suspension; mix for 4 minutes at a speed of 450 r / min using a twin-shaft mixer.

[0117] (4) Pour into the mold, vibrate with a flat vibrator, and allow to solidify naturally.

[0118] (5) Cover with film and allow to cure naturally for 10 days.

[0119] Comparative Example 3

[0120] This comparative example provides a lead-zinc-manganese tailings heavy metal ion solidification product and solidification method. The preparation and solidification methods of the solidified product are as follows:

[0121] (1) Bacillus pasteurianus was selected and inoculated into a modified Luria-Bertani medium (yeast extract: 5 g / L, peptone: 10 g / L, glucose: 10 g / L, NaCl: 10 g / L, K2HPO4: 0.6 g / L, KH2PO4: 0.4 g / L, MgSO4·7H2O: 0.2 g / L, FeSO4·7H2O: 0.03 g / L, CaCl2·2H2O: 0.01 g / L); cultured at 30 ± 2 °C, 180 rpm, and shaken for 48 h until the OD 600 =1.8 (logarithmic growth period), EPS secretion 130mg / L.

[0122] (2) With 10 mg / L Pb 2+ 、5mg / L Zn 2+ 、3mg / L Mn 2+ Starting with an inorganic salt culture medium (NH4NO3: 1650mg / L, KNO3: 1900mg / L, KH2PO4: 160mg / L, CaCl2·2H2O: 420mg / L, MgSO4·7H2O: 350mg / L), the heavy metal tolerance acclimation was performed using a gradient increment acclimation method. Each round of acclimation lasted 48 hours. After the bacteria grew stably, the concentrations of the three heavy metal ions were increased by about 15% respectively, and 8 rounds were performed continuously. The culture temperature of the entire acclimation process was controlled at 30±2℃ and carried out under low-speed shaking (60r / min). The final tolerance concentration reached 40mg / L Pb 2+ 、20mg / L Zn 2+ 、12mg / L Mn 2+ After acclimation, 0.2% (w / v) chitosan oligosaccharide inducer was added to the bacterial suspension and cultured until the viable bacterial count of the bacterial suspension reached 1.2×10 8 CFU / mL, and EPS secretion increased by 45% (reaching 180 mg / L).

[0123] (3) Only 1 L (volume ratio 1 part) of the acclimated bacterial suspension was taken without mixing it with quaternized chitosan and organically modified nanoclay, and the free bacterial suspension was used directly.

[0124] (3) Take 150 parts of lead, zinc and manganese tailings powder (mass ratio is 1:1:1) and grind it to a particle size of less than 0.16 mm for later use.

[0125] (4) Add 100 parts of basic magnesium sulfate cement (the molar ratio of magnesium oxide to magnesium sulfate heptahydrate is 5:1), 50 parts of bacterial suspension, and 55 parts of water; use one-time stirring, the stirring time is 5 minutes, and the speed is 500r / min.

[0126] (5) Pour the evenly stirred slurry into a mold, vibrate it to make it dense using an inserted vibrating rod, and solidify it under natural conditions.

[0127] (6) Cover with straw bags and allow to cure naturally for 14 days.

[0128] The performance tests were performed on the cured products of the embodiments and comparative examples, and the results are shown in Table 1.

[0129] Table 1 Test properties of cured products of various embodiments and comparative examples

[0130]

[0131] The results showed that comparative examples 1 and 2 seriously exceeded the standards in terms of zinc and manganese, especially, indicating that the use of a single silicate or BMSC system could not effectively encapsulate or stabilize heavy metals, while all examples were better than the standard limits in terms of the leaching concentrations of lead, zinc and manganese ions. The negatively charged EPS secreted by the microbial strains in the composite microbial functional system captured heavy metal ions through electrostatic adsorption and complexation, the positively charged groups and network structure of the quaternized chitosan fixed heavy metals through electrostatic adsorption and physical encapsulation, and the high specific surface area and negative charge of the organically modified nanoclay enriched heavy metals through ion exchange and surface adsorption. The three synergistically formed an "adsorption-encapsulation-fixation" composite barrier, which is the core mechanism for reducing the leaching concentration.

[0132] In Comparative Example 3, basic magnesium sulfate cement solidified lead, zinc, and manganese tailings with the addition of microbial strains. The solidified body had certain pores on its surface, resulting in high heavy metal leaching. The presence of the microbial strains failed to significantly enhance the leaching inhibition effect of the solidified body, but instead resulted in a decrease in strength. Examples 1 to 4 and 6 all introduced acid-sensitive microcapsules encapsulating a composite microbial functional system, and the 28-day compressive strength generally exceeded 50 MPa, much higher than the comparative example. The EPS secreted by the microbial strains, the bioflocculation properties, and the chitosan-clay worked together to improve the slurry structure and hydration product density, which was also the key to the strength improvement. In Example 5, no microcapsules were used for encapsulation, and the compressive strength was slightly lower than 50 MPa. The leaching concentration of heavy metal ions was higher than that of the other examples, but still lower than the comparative example data, indicating the lack of the cementing and strengthening effect of the microcapsules.

[0133] In Example 3, BMSC (MgO and MgSO4·7H2O molar ratio 6:1) was used to combine with the composite system, and the compressive strength reached 55 MPa, indicating that appropriate magnesium oxide activity and ratio adjustment can help provide a denser and more stable hydration structure, providing a good bearing matrix for the composite system.

[0134] In all examples, lead ion concentrations were below 5 mg / L, zinc ion concentrations were below 100 mg / L, and manganese ion concentrations were also maintained below 5 mg / L. These values ​​are well below the upper limits specified in the national standard GB / T 30810-2014, "Determination of Leachable Heavy Metals in Cement Mortar." This demonstrates that this system is suitable for resource-based solidification and treatment of complex, multi-source tailings, and has a promising foundation for engineering application.

[0135] In the present invention, unless otherwise specified, the scientific and technical terms used herein have the meanings commonly understood by those skilled in the art. In addition, the reagents, materials and operating procedures used herein are those widely used in the corresponding fields.

[0136] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A heavy metal ion solidified product of lead, zinc and manganese tailings, characterized by: Including basic magnesium sulfate cement and acid-sensitive microcapsules; The acid-sensitive microcapsules are 2+ A cross-linked sodium alginate-coated composite microbial functional system was prepared; The composite microbial functional system includes bacterial suspension, quaternized chitosan and organic modified nanoclay; The bacterial suspension comprises microbial strains and EPS secreted therefrom.

2. The lead-zinc-manganese tailings heavy metal ion solidified product according to claim 1, characterized in that: The preparation method of the bacterial suspension comprises the following steps: S1. Inoculate the microbial strain into a modified Luria-Bertani medium, culture until the logarithmic growth phase, filter, and centrifuge to obtain a bacterial solution; S2. Inoculate the bacterial solution obtained in S1 into an inorganic salt medium containing lead, zinc, and manganese ions, perform heavy metal tolerance acclimation culture using a gradient acclimation method, filter, and centrifuge to obtain a dominant bacterial solution; S3. Add an inducer to the dominant bacterial solution for expansion to obtain the bacterial suspension.

3. The lead-zinc-manganese tailings heavy metal ion solidified product according to claim 2, characterized in that: In S1 of the bacterial suspension preparation method, the modified Luria-Bertani medium comprises 4-6 g / L yeast extract, 8-12 g / L peptone, 8-12 g / L glucose, 8-12 g / L sodium chloride, 0.5-1.5 g / L dipotassium hydrogen phosphate, 0.2-0.8 g / L potassium dihydrogen phosphate, 0.1-0.5 g / L magnesium sulfate, 0.01-0.05 g / L ferrous sulfate, 0.01-0.05 g / L calcium chloride, and water; and the culture conditions are: 28-32° C., 150-200 rpm shaking incubator for 44-50 hours; In S2, the inorganic salt culture medium includes 1500-1800 mg / L ammonium nitrate, 1800-2000 mg / L potassium nitrate, 150-200 mg / L potassium dihydrogen phosphate, 400-500 mg / L calcium chloride, 350-400 mg / L magnesium sulfate heptahydrate, and water; the initial concentration of lead ions is 8-12 mg / L, the initial concentration of zinc ions is 3-7 mg / L, and the initial concentration of manganese ions is 1-5 mg / L; the acclimation culture conditions are 28-30° C., static culture or shaking culture at 50-70 rpm for 48-72 hours per cycle, and continuous culture for 5-10 cycles, with the concentrations of lead, zinc, and manganese ions increasing by 10-20% each cycle; In S3, the inducer is one or more of trehalose, fructose, and chitosan oligosaccharide, and the addition amount is 0.1-0.3% (w / v); and the expansion time is 20-30 hours.

4. The lead-zinc-manganese tailings heavy metal ion solidified product according to claim 1, characterized in that: The microbial strain is one or more of Bacillus pasteurianus, Bacillus mucilaginosus, Desulfovibrio, Bacillus polymyxa, Bacillus subtilis, and Staphylococcus epidermidis.

5. The lead-zinc-manganese tailings heavy metal ion solidified product according to claim 1, characterized in that: The preparation method of the quaternized chitosan comprises: dissolving chitosan in an acetic acid solution to obtain a chitosan solution; slowly adding 2,3-epoxypropyltrimethylammonium chloride dropwise, and reacting at 40 to 60° C. for 7 to 9 hours to obtain the quaternized chitosan; The chitosan is chitosan with a deacetylation degree of ≥90%; The concentration of the acetic acid solution is 1 to 3% (v / v); the concentration of the chitosan solution is 1 to 3% (w / v); The mass ratio of 2,3-epoxypropyltrimethylammonium chloride to chitosan is 1:2-5.

6. The lead-zinc-manganese tailings heavy metal ion solidified product according to claim 1, characterized in that: The preparation method of the organic modified nanoclay is as follows: dispersing sodium bentonite in water to obtain a suspension; stirring at 50-70° C., slowly adding a cetyltrimethylammonium bromide solution; reacting for 1.5-2.5 hours to obtain the organic modified nanoclay; The cation exchange capacity of the sodium bentonite is 80 to 100 mmol / 100 g; the concentration of the suspension is 3 to 7% (w / v); The added amount of the hexadecyltrimethylammonium bromide is 1 to 2 times the cation exchange capacity.

7. The lead-zinc-manganese tailings heavy metal ion solidified product according to claim 1, characterized in that: The preparation method of the acid-sensitive microcapsules comprises: uniformly mixing the composite microbial functional system with a sodium alginate solution to form an aqueous phase; dripping the aqueous phase into a CaCl2 solution and stirring to form spherical calcium alginate gel microcapsules; adding sodium carboxymethyl cellulose to adjust the viscosity to 50-100 mPa·s, filtering, and centrifuging to obtain the acid-sensitive microcapsules; In the composite microbial functional system, the mass ratio of quaternized chitosan to organically modified nanoclay is 1 to 3:1, and the amount of bacterial suspension added is 5 to 15% of the total mass of the composite microbial functional system; The concentration of the sodium alginate solution is 1 to 3% (w / v); the volume ratio of the composite microbial functional system to the sodium alginate solution is 1:1 to 3; The concentration of the CaCl2 solution is 3-7% (w / v); the stirring condition is 250-350 rpm; The added amount of sodium carboxymethyl cellulose is 0.1-0.3% (w / v).

8. A method for solidifying heavy metal ions in lead, zinc and manganese tailings using the solidified product according to any one of claims 1 to 7, characterized in that: Adding the basic magnesium sulfate cement, acid-sensitive microcapsules and water to the tailings to be treated, stirring evenly to form a slurry; Pour the slurry into a mold or an underground pit, vibrate the slurry to ensure density, and solidify it in a natural environment; Cover the solidified body with straw bags or film and allow it to cure naturally.

9. The method for solidifying heavy metal ions in lead, zinc and manganese tailings according to claim 8, wherein: The tailings are one or more of lead tailings, zinc tailings, and manganese tailings; The tailings are first crushed or ground to a particle size of less than 0.16 mm before preparing the slurry; The basic magnesium sulfate cement comprises magnesium oxide, magnesium sulfate heptahydrate and an organic acid salt admixture; the molar ratio of magnesium oxide to magnesium sulfate heptahydrate is 4 to 10:1; the organic acid salt admixture is one or more of tartaric acid, citric acid and sodium gluconate, and the addition amount is 0.1 to 2% of the mass of magnesium oxide; The mass ratio of tailings, basic magnesium sulfate cement and water is 50-300:100:30-100, and the dosage of acid-sensitive microcapsules is 5-10% of the mass of basic magnesium sulfate cement.

10. The method for solidifying heavy metal ions in lead, zinc and manganese tailings according to claim 8, wherein: The stirring condition is 300-800 r / min and the time is 3-10 min; The natural curing time is at least 3 to 14 days; The solidified body is used for filling abandoned mines, making slope protection boards for sewage ditches or for landfill and reclamation projects of tailings ponds.

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