Preparation method of high-strength heavy metal cured geopolymer based on lead-zinc tailings

Abstract

The invention discloses a preparation method of a high-strength heavy metal cured geopolymer based on lead-zinc tailings, and belongs to the technical field of solid waste resource utilization and heavy metal pollution treatment. The lead-zinc tailings, the fly ash, the diatomite and the alkali activator are used as raw materials, and the three action mechanisms of mesoporous adsorption-chemical bonding-structure enhancement of the diatomite are utilized, so that the curing efficiency and stability of heavy metal residues contained in the lead-zinc tailings are improved, and the risk to the ecological environment is greatly reduced; the fly ash is used as a core aluminum-silicon raw material, is rich in active SiO2 and Al2O3, is dissolved under the action of alkali to generate a geopolymer gel skeleton, and is a main source of strength; the lead-zinc tailings serve as an auxiliary silicon-aluminum source and aggregate, part of active ingredients of the lead-zinc tailings participate in the reaction, meanwhile, unreacted particles play a role in filling micro aggregate, and particle composition is optimized; and the alkali activator provides a high-alkalinity environment, aluminosilicate active components in other raw materials are dissolved, and finally the high-strength geopolymer is generated through an alkali excitation reaction.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of solid waste resource utilization and heavy metal pollution control, and particularly relates to a preparation method of high-strength heavy metal solidified geopolymer based on lead-zinc tailings. BACKGROUND

[0002] During the exploitation of lead-zinc ore resources, the uneven equipment level and mineral processing technology of mining enterprises can lead to low comprehensive utilization rate of mineral resources, and cause a large amount of lead-zinc tailings to be stacked. Long-term stacking of lead-zinc tailings can cause serious heavy metal pollution to the surrounding ecological environment, and the traditional solidification technology has the problems of low strength and high leaching risk. Therefore, how to resourcefully utilize lead-zinc tailings waste and reduce the heavy metal pollution to the ecological environment has become a current research hotspot.

[0003] Geopolymer is a cement-like cementitious material generated by polycondensation of silicon-aluminum raw materials, which has a three-dimensional network structure formed by alternating bonding of [SiO4] tetrahedron and [AlO4] tetrahedron through shared oxygen atoms, and can fix heavy metals through physical wrapping and chemical bonding dual mechanisms. Compared with OPC (ordinary Portland cement), geopolymer cementitious material has the advantages of high strength, high toughness, low shrinkage and low thermal conductivity, good wear resistance, good acid and alkali corrosion resistance, etc., and can be widely applied in fields such as construction, mining, chemical industry, road engineering and nuclear industry.

[0004] Chinese patent CN119504164A discloses a lead-zinc tailings ceramsite and a preparation method thereof, the main raw materials of which are lead-zinc tailings, limestone tailings, active mullite nano powder, glass micro powder and dry sludge powder, and the strength is 6.8-9.8 MPa. Chinese patent CN118666567A discloses a preparation method of lead-zinc tailings-based sintered brick and the lead-zinc tailings-based sintered brick, the main raw materials of which are lead-zinc tailings, clay and glass powder, and the compressive strength is 26-38 MPa. Chinese patent CN118026598A discloses a method for solidifying lead-zinc tailings through geopolymerization, the main raw materials of which are lead-zinc tailings, metakaolin and alkaline activator, and the compressive strength is less than 30 MPa. However, the compressive strength of the geopolymer prepared by using lead-zinc tailings in the above-mentioned existing patents is less than 40 MPa.

[0005] Therefore, how to utilize lead-zinc tailings to prepare high-strength geopolymer while realizing long-term stable solidification of heavy metals has become a technical problem to be solved in the field. SUMMARY

[0006] To solve the above technical problems, the present application provides a preparation method of high-strength heavy metal solidified geopolymer based on lead-zinc tailings.

[0007] To achieve the above object, the application provides the following technical solutions.

[0008] The application provides a high-strength heavy metal solidified geopolymer based on lead-zinc tailings, raw materials including geopolymer precursors and alkali activators.

[0009] The geopolymer precursors include lead-zinc tailings 50%-65%, fly ash 20%-30% and diatomite 10%-15% by mass percentage.

[0010] The alkali activator is used in an amount of 25%-35% of the mass of the geopolymer precursors.

[0011] Further, the lead-zinc tailings include the following components: SiO2 45-60wt.%, CaO 5-12wt.%, Fe2O3 5-15wt.%, Al2O3 8-12wt.%, PbO 0.5-3wt.% and ZnO 1-5wt.%.

[0012] Further, the diatomite is calcined diatomite, which is obtained by calcining diatomite at 300-500℃ for 2-4h.

[0013] Further, the fly ash is high-calcium fly ash, and the content of CaO in the high-calcium fly ash is 15-30wt.%.

[0014] Further, the alkali activator is a mixed solution of sodium hydroxide and water glass.

[0015] The application also provides a preparation method of the high-strength heavy metal solidified geopolymer based on lead-zinc tailings, which comprises the following steps:

[0016] 1) Dry mixing lead-zinc tailings, fly ash and diatomite to obtain geopolymer precursors;

[0017] 2) Adding alkali activators to the geopolymer precursors, and stirring to obtain a slurry;

[0018] 3) Casting and curing the slurry to obtain the high-strength heavy metal solidified geopolymer based on lead-zinc tailings.

[0019] Further, in step 1), the lead-zinc tailings and fly ash further include the step of grinding the lead-zinc tailings and fly ash to D50≤20μm before dry mixing.

[0020] The diatomite further includes the step of grinding the diatomite to D50≤20μm and then calcining at 300-500℃ for 2-4h before dry mixing.

[0021] Further, in step 2), the preparation method of the alkali activator is as follows: sodium hydroxide is dissolved in water to prepare a sodium hydroxide solution with a concentration of 10-12 mol / L; and water glass is added into the sodium hydroxide solution according to a sodium silicate modulus of 2.0-2.5, and then stirring and aging are performed to obtain the alkali activator.

[0022] Further, in step 2), the fluidity of the slurry is 160-180 mm.

[0023] Further, in step 3), the curing includes steam curing and sealed curing performed in sequence.

[0024] The temperature of the steam curing is 80±5℃, the relative humidity is ≥95%, and the time is 24 h.

[0025] The temperature of the sealed curing is 25±2℃, and the time is 7 days.

[0026] Compared with the prior art, the present application has the following advantages and technical effects:

[0027] The present application uses lead-zinc tailings, fly ash, diatomite and alkali activator as raw materials, and utilizes the triple action mechanism of diatomite mesoporous adsorption-chemical bonding-structure enhancement to improve the solidification efficiency and stability of the heavy metal residues contained in the lead-zinc tailings, thereby greatly reducing the risk to the ecological environment; the fly ash, as the core aluminosilicate raw material, is rich in active SiO2 and Al2O3, and generates a geopolymer gel skeleton after being dissolved under the action of alkali, which is the main source of strength; the lead-zinc tailings serve as auxiliary silicon-aluminum source and aggregate, part of the active components of which participate in the reaction, and the unreacted particles play the role of micro-aggregate filling to optimize the particle size distribution; and the alkali activator provides a high-alkali environment, dissolves the aluminosilicate active components in other raw materials, and finally generates high-strength geopolymer through alkali activation reaction.

[0028] The high-strength heavy metal solidification geopolymer based on lead-zinc tailings provided by the present application can efficiently immobilize Pb 2 + , Cd 2+ , Cu 2+ and other heavy metals in the lead-zinc tailings, and compared with the traditional lead-zinc tailings solidification method, the method of the present application can realize long-term stable solidification of heavy metals, and can still maintain its long-term stability even under complex environmental conditions.

[0029] The high-strength heavy metal solidification geopolymer based on lead-zinc tailings provided by the present application can achieve a compressive strength of more than 40 MPa, has good durability, the used materials are easy to obtain, can significantly improve the resource utilization rate of lead-zinc tailings, and reduce the adverse effects on the ecological environment. BRIEF DESCRIPTION OF DRAWINGS

[0030] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application, illustrate the preferred embodiment of the application and assist in

[0031] Figure 1 SEM images of the high-strength heavy metal solidified geopolymer based on lead-zinc tailings prepared for Example 1. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be apparently and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without any creative work fall within the protection scope of the present application.

[0033] In order to make the above objectives, characteristics and advantages of the present application more apparent, comprehensible and easier to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0034] The embodiment of the present application provides a high-strength heavy metal solidified geopolymer based on lead-zinc tailings, raw materials including geopolymer precursor and alkali activator;

[0035] The geopolymer precursor includes lead-zinc tailings 50%-65%, fly ash 20%-30% and diatomite 10%-15% by mass percentage; further preferably, lead-zinc tailings 55%-60%, fly ash 25%-30% and diatomite 14%-15%.

[0036] The alkali activator is used in an amount of 25%-35% of the mass of the geopolymer precursor, and further preferably 30%-35%.

[0037] In the preferred embodiment, the lead-zinc tailings include the following components: SiO2 45-60wt.%, CaO 5-12wt.%, Fe2O3 5-15wt.%, Al2O3 8-12wt.%, PbO 0.5-3wt.% and ZnO 1-5wt.%.

[0038] In a preferred embodiment, the diatomite is calcined diatomite; the calcined diatomite is obtained by calcining diatomite at 300-500℃ for 2-4h. The main purpose of calcining diatomite in the present application is to remove the organic matter and bound water inside diatomite, while increasing its specific surface area and surface silanol (Si-OH) density, thereby enhancing its adsorption capacity for heavy metal ions and reactivity in alkali-activated systems. The calcination temperature is a key factor affecting the performance of diatomite: when the calcination temperature is lower than 300℃, the removal of organic matter and bound water is not complete, and the activity and specific surface area of diatomite are limitedly improved; when the calcination temperature is higher than 500℃, the amorphous SiO2 of diatomite will transform into crystalline state, leading to the collapse of its unique mesoporous structure, a sharp decrease in specific surface area, and a large reduction in surface silanol, thereby losing its adsorption activity and reactivity. Therefore, the calcination temperature is strictly controlled between 300-500℃ in the present application to achieve the best balance between removing impurities, maintaining mesoporous structure, and maximizing surface activity. By calcining, the organic matter in diatomite is removed and its mesoporous channels are opened, the calcination increases the degree of amorphization of diatomite, the specific surface area is increased to ≥150m 2 / g, the surface silanol (Si-OH) density is improved, and the adsorption capacity for heavy metal ions and reactivity in alkali-activated systems are significantly enhanced.

[0039] In a preferred embodiment, the fly ash is high-calcium fly ash, and the content of CaO in the high-calcium fly ash is 15-30wt.%. The use of high-calcium fly ash in the present application can generate more calcium silicate gel, significantly improving the strength of geopolymer.

[0040] In a preferred embodiment, the alkali activator is a mixed solution of sodium hydroxide and water glass.

[0041] The present application also provides a preparation method of the high-strength heavy metal solidified geopolymer based on lead-zinc tailings according to the above technical solution, which comprises the following steps:

[0042] 1) Dry mixing lead-zinc tailings, fly ash and diatomite to obtain a geopolymer precursor; diatomite is dry mixed with lead-zinc tailings and fly ash at the same time to ensure uniform dispersion of diatomite as heavy metal adsorption sites network;

[0043] 2) Adding an alkali activator to the geopolymer precursor and stirring to obtain a slurry;

[0044] 3) Casting and curing the slurry to obtain the high-strength heavy metal solidified geopolymer based on lead-zinc tailings.

[0045] In a preferred embodiment, in step 1), the lead-zinc tailings and fly ash further comprise a step of grinding the lead-zinc tailings and fly ash to D50≤20μm before dry mixing.

[0046] In the preferred embodiment, the lead-zinc tailings are ground to D50≤20μm, specifically: the lead-zinc tailings are dried at 60℃-80℃ for 10h-12h, then placed in a ball mill and ground at a speed of 60±6rpm-80±8rpm for 80min-90min to obtain lead-zinc tailings powder with D50≤20μm.

[0047] In the preferred embodiment, the fly ash is ground to D50≤20μm, specifically: the fly ash is placed in a ball mill and ground at a speed of 60±6rpm-80±8rpm for 50-60min to obtain fly ash with D50≤20μm.

[0048] In the preferred embodiment, in step 1), the diatomite further comprises a step of grinding the diatomite to D50≤20μm before dry mixing, and then calcining at 300℃-500℃ for 2h-4h; the temperature of the calcination is further preferably 350℃-450℃, and the time of the calcination is further preferably 2h-3.5h. The present application exposes the active SiO2 surface of diatomite by grinding, and after the grinding-calcination treatment, the three mechanisms of mesoporous adsorption (physical), Si-O-M + bonding (chemical), and C-S-H gel filling (structural reinforcement) simultaneously improve the heavy metal solidification rate and the geopolymer strength.

[0049] In the preferred embodiment, in step 2), the preparation method of the alkali activator is: dissolving sodium hydroxide in water to prepare a sodium hydroxide solution with a concentration of 10-12mol / L; adding water glass to the sodium hydroxide solution according to a sodium silicate modulus of 2.0-2.5, and stirring and aging to obtain the alkali activator; the time of stirring and aging is 24h.

[0050] In the preferred embodiment, in step 2), the fluidity of the slurry is 160-180mm.

[0051] In the preferred embodiment, in step 3), the casting is specifically: pouring the slurry into a steel mold with a size of 40×40×40mm 3 , and then performing vibration degassing; the vibration frequency of the vibration degassing is 50Hz, and the time of the vibration degassing is 30s.

[0052] In the preferred embodiment, in step 3), the curing comprises steam curing and sealed curing performed in sequence; the temperature of the steam curing is 80±5℃, the relative humidity is ≥95%, and the time is 24h; the temperature of the sealed curing is 25±2℃, and the time is 7 days.

[0053] In the embodiment of the present application, room temperature refers to "25±2℃".

[0054] The raw materials in the embodiments of the present application are all purchased through the market route unless otherwise specified.

[0055] Embodiment 1

[0056] A high-strength heavy metal solidified geopolymer based on lead-zinc tailings, which is composed of a geopolymer precursor and an alkali activator; the geopolymer precursor is composed of 60% of lead-zinc tailings, 25% of high-calcium fly ash, and 15% of diatomite by mass percentage; the amount of the alkali activator is 30% of the mass of the geopolymer precursor; the composition of the lead-zinc tailings is: SiO2 50.2 wt.%, CaO 10.7 wt.%, Fe2O3 10.5 wt.%, Al2O3 11.8 wt.%, PbO 1.5 wt.%, and ZnO 3.5 wt.%, and the rest is inevitable impurities and trace components; the content of CaO in the high-calcium fly ash is 22.3 wt.%;

[0057] The preparation method of the above high-strength heavy metal solidified geopolymer based on lead-zinc tailings, the specific steps are as follows:

[0058] 1) The lead-zinc tailings in Linzhi, Tibet, are dried at 60℃ for 12h and then ground in a ball mill at a speed of 60±6rpm for 90min to obtain lead-zinc tailings powder with D50=15μm, which is recorded as raw material A;

[0059] 2) The high-calcium fly ash is ground in a ball mill at a speed of 60±6rpm for 60min to obtain high-calcium fly ash with D50=10μm, which is recorded as raw material B;

[0060] 3) The diatomite in Ali, Tibet, is ground in a ball mill at a speed of 50±5rpm for 40min to obtain diatomite powder with D50=18μm, which is then calcined at 350℃ for 2h to obtain calcined diatomite, which is recorded as raw material C;

[0061] 4) 120g of raw material A, 50g of raw material B, and 30g of raw material C are stirred and dry-mixed for 8min to obtain a geopolymer precursor, which is recorded as mixture D;

[0062] 5) Sodium hydroxide particles are dissolved in deionized water to prepare a sodium hydroxide solution with a concentration of 10mol / L, and water glass is added to the obtained sodium hydroxide solution according to a sodium silicate modulus of 2.0 and stirred and aged for 24h to obtain an alkali activator, which is recorded as mixed solution E;

[0063] 6) 60g of mixed solution E is added to mixture D, and then the slurry is stirred in a stirrer until the flow degree of the slurry is 160mm;

[0064] 7) The slurry prepared in step 6) is poured into a 40×40×40mm 3The steel mold was vibrated and degassed (frequency 50 Hz, time 30 s), followed by steam curing (80±5℃, humidity≥95%, 24 h), re-sealed curing (25±2℃, 7 days), and the high-strength heavy metal solidified geopolymer based on lead-zinc tailings was obtained after demolding, which was recorded as geopolymer F.

[0065] Figure 1 SEM image of the high-strength heavy metal solidified geopolymer based on lead-zinc tailings prepared in Example 1. From Figure 1 It can be seen that the geopolymer presents a dense and uniform microstructure. The diatomite particles after calcination pretreatment are tightly wrapped and bridged by a large amount of geopolymer gel, the interface between the two is blurred and well combined, and no obvious cracks or pores are observed. This indicates that the diatomite has successfully integrated into the geopolymer three-dimensional network, and its abundant mesoporous structure provides a good adhesion and filling space for the gel phase, while the gel phase effectively blocks the pore channels of the diatomite. This uniform and dense "diatomite-gel" composite structure microscopically explains the principle of the material having a high compressive strength of more than 40 MPa, and provides a stable physical wrapping and chemical bonding environment for the solidification of heavy metal ions.

[0066] Example 2

[0067] A high-strength heavy metal solidified geopolymer based on lead-zinc tailings, which is composed of a geopolymer precursor and an alkali activator; the geopolymer precursor is composed of 55% lead-zinc tailings, 30% high-calcium fly ash, and 15% diatomite by mass percentage; the amount of alkali activator is 35% of the mass of the geopolymer precursor; the composition of the lead-zinc tailings is: SiO2 52.8wt.%, CaO 9.1wt.%, Fe2O3 11.3wt.%, Al2O3 10.5wt.%, PbO 1.9wt.%, and ZnO 4.1wt.%, and the rest is unavoidable impurities and trace components; the content of CaO in the high-calcium fly ash is 25.6wt.%;

[0068] The preparation method of the above high-strength heavy metal solidified geopolymer based on lead-zinc tailings, the specific steps are as follows:

[0069] 1) The lead-zinc tailings from Shannan, Tibet were dried at 80℃ for 12h and then ground in a ball mill at a speed of 80±8rpm for 80min to obtain lead-zinc tailings powder with D50=10μm, which was recorded as raw material G;

[0070] 2) The high-calcium fly ash was ground in a ball mill at a speed of 80±8rpm for 50min to obtain high-calcium fly ash with D50=8μm, which was recorded as raw material H;

[0071] 3) Put the diatomite from Nagqu, Tibet into a ball mill and grind for 35 min at a speed of 55±5 rpm to obtain diatomite powder with D50=15 μm, then calcine at 400℃ for 3 h to obtain calcined diatomite, denoted as raw material I;

[0072] 4) Stir and dry mix 110 g of raw material G, 60 g of raw material H and 30 g of raw material I for 10 min to obtain a geopolymer precursor, denoted as mixture J;

[0073] 5) Dissolve sodium hydroxide particles in deionized water to obtain a sodium hydroxide solution with a concentration of 12 mol / L, add water glass to the obtained sodium hydroxide solution according to a sodium silicate modulus of 2.5 and stir and age for 24 h to obtain an alkali activator, denoted as mixed solution K;

[0074] 6) Add 70 g of mixed solution K to mixture J, then stir in a stirrer until the slurry flowability is 180 mm;

[0075] 7) Put the slurry obtained in step 6) into a steel mold with dimensions of 40×40×40 mm 3 , perform vibration and exhaust (frequency 50 Hz, time length 30 s), then perform steam curing (80±5℃, humidity≥95%, 24 h), then perform sealed curing (25±2℃, 7 days), and after demolding, a high-strength heavy metal solidified geopolymer based on lead-zinc tailings is obtained, denoted as geopolymer L.

[0076] Example 3

[0077] A high-strength heavy metal solidified geopolymer based on lead-zinc tailings, which is composed of a geopolymer precursor and an alkali activator; the geopolymer precursor is composed of 55.85% of lead-zinc tailings, 29.25% of high-calcium fly ash and 14.9% of diatomite by mass percentage; the amount of the alkali activator is 34.04% of the mass of the geopolymer precursor; the composition of the lead-zinc tailings is: SiO2 55.5 wt.%, CaO 7.3 wt.%, Fe2O3 9.2 wt.%, Al2O3 12.4 wt.%, PbO 2.5 wt.% and ZnO 3.0 wt.%, and the rest is unavoidable impurities and trace components; the content of CaO in the high-calcium fly ash is 19.8 wt.%;

[0078] The preparation method of the above high-strength heavy metal solidified geopolymer based on lead-zinc tailings, the specific steps are as follows:

[0079] 1) Dry the lead-zinc tailings from Nyingchi, Tibet at 70℃ for 10 h, then put them into a ball mill and grind for 85 min at a speed of 70±7 rpm to obtain lead-zinc tailings powder with D50=12 μm, denoted as raw material M;

[0080] 2) The high-calcium fly ash was placed in a ball mill and ground at a speed of 70 ± 7 rpm for 55 min to obtain high-calcium fly ash with a D50 of 9 μm, denoted as raw material N;

[0081] 3) The diatomite from Ali, Tibet was placed in a ball mill and ground at a speed of 60 ± 5 rpm for 30 min to obtain diatomite powder with a D50 of 12 μm, which was then calcined at 450 °C for 3.5 h to obtain calcined diatomite, denoted as raw material O;

[0082] 4) 105 g of raw material M, 55 g of raw material N, and 28 g of raw material O were stirred and dry-mixed for 10 min to obtain a geopolymer precursor, denoted as mixture P;

[0083] 5) Sodium hydroxide particles were dissolved in deionized water to obtain a sodium hydroxide solution with a concentration of 11 mol / L, and water glass was added to the obtained sodium hydroxide solution according to a sodium silicate modulus of 2.3 and stirred and aged for 24 h to obtain an alkali activator, denoted as mixed solution Q;

[0084] 6) 64 g of mixed solution Q was added to mixture P, and then the slurry was stirred in a blender until the slurry flow degree was 170 mm;

[0085] 7) The slurry prepared in step 6) was poured into a 40 × 40 × 40 mm 3 steel mold, and vibration and exhaust (frequency 50 Hz, time 30 s) were performed, followed by steam curing (80 ± 5 °C, humidity ≥ 95%, 24 h), and then sealed curing (25 ± 2 °C, 7 days). After demolding, a high-strength heavy metal solidified geopolymer based on lead-zinc tailings was obtained, denoted as geopolymer R.

[0086] The high-strength heavy metal solidified geopolymer based on lead-zinc tailings in Examples 1-3 was subjected to compressive strength test (referring to GB / T 17671-2021) and heavy metal ion (Pb 2+ , Cd 2+ , Cu 2+ ) toxicity leaching experiment (referring to GB 5085.3-2007 and HJ 557-2010), and the results are shown in Table 1.

[0087] Table 1

[0088]

[0089] As can be seen from Table 1, the compressive strength of the high-strength heavy metal solidified geopolymer based on lead-zinc tailings provided by the present application can reach above 43.2 MPa, and the leaching concentration of heavy metal ions Pb 2+ , Cd 2+ , Cu 2+ is low, realizing efficient immobilization of heavy metal ions in lead-zinc tailings and strength improvement of geopolymer.

[0090] The polymer F obtained in Example 1 was subjected to the following environmental tests:

[0091] Acid-etching environment: soaking in H2SO4 solution with pH=3 for 30 days; the result showed that the compressive strength retention rate was 85.2%, and the Pb 2+ The leaching concentration was 0.15 mg / L (lower than the limit value of 0.25 mg / L specified in GB 5085.3-2007);

[0092] Freeze-thaw cycle: 50 cycles of -20℃ (4h)→20℃ (4h); the result showed that the mass loss rate was 2.8%, and the strength retention rate was 89.5%.

[0093] Comparative Example 1

[0094] A method for curing lead-zinc tailings through geopolymeric reaction, comprising the following steps:

[0095] (1) Kaolin ore (the mass content of kaolin in the ore was 97%) was calcined at 750℃ for 2h, and then was ground in a ball mill at a rotation speed of 50±5 rpm for 6h to obtain metakaolin powder (denoted as raw material M) with D90 of 58.35μm;

[0096] (2) Lead-zinc tailings blocks were dried at 40℃ for 24h, and then were ground in a ball mill at a rotation speed of 50±5 rpm for 1h to obtain lead-zinc tailings;

[0097] (3) 60g of metakaolin powder (raw material M) was added to 240g of lead-zinc tailings, and mixed in a ball mill at a rotation speed of 50±5 rpm for 15min to obtain a uniformly mixed mixture;

[0098] (4) The mixture prepared in step (3) was added to 150g of water glass solution with a modulus of 1.0 and a sodium silicate content of 18wt%, and was stirred in a standard cement paste stirrer at a slow speed (rotation speed of 140±5 rpm and revolution speed of 62±5 rpm) for 2min, and then was stirred at a fast speed (rotation speed of 285±10 rpm and revolution speed of 125±10 rpm) for 3min to prepare a flowable slurry, and the molar ratio of Na2O to Al2O3 in the flowable slurry was 1.1;

[0099] (5) The flowable slurry prepared in step (4) was transferred into a mold with a size of 20×20×20mm 3 for curing and shaping, and was demolded after curing in a curing box with a temperature of 40±2℃ and a relative humidity of 95% for 8h to obtain a hardened lead-zinc tailings cured body.

[0100] The hardened lead-zinc tailings cured body obtained in Comparative Example 1 was subjected to the following environmental tests:

[0101] Acid etching environment: immersed in H2SO4 solution with pH=3 for 30 days; the result shows that the compressive strength retention rate is only 58.3%, Pb 2+ The leaching reaches 0.42mg / L (significantly higher than the limit value 0.25mg / L stipulated in GB5085.3-2007).

[0102] Comparative Example 2

[0103] A geopolymer based on lead-zinc tailings, which is composed of geopolymer precursor and alkali activator; according to mass percentage, the geopolymer precursor is composed of lead-zinc tailings 60%, high calcium fly ash 10% and diatomite 30%; the amount of alkali activator is 30% of the mass of geopolymer precursor; the others are the same as Example 1.

[0104] Comparative Example 3

[0105] A geopolymer based on lead-zinc tailings, which is composed of geopolymer precursor and alkali activator; according to mass percentage, the geopolymer precursor is composed of lead-zinc tailings 60%, high calcium fly ash 35% and diatomite 5%; the amount of alkali activator is 30% of the mass of geopolymer precursor; the others are the same as Example 1.

[0106] Comparative Example 4

[0107] A geopolymer based on lead-zinc tailings, which is composed of geopolymer precursor and alkali activator; according to mass percentage, the geopolymer precursor is composed of lead-zinc tailings 40%, high calcium fly ash 45% and diatomite 15%; the amount of alkali activator is 30% of the mass of geopolymer precursor; the others are the same as Example 1.

[0108] Comparative Example 5

[0109] A high-strength heavy metal solidification geopolymer based on lead-zinc tailings, which is different from Example 1 in that in step 3), diatomite from Tibet Ali region is calcined at 550℃ for 2h; the others are the same as Example 1.

[0110] Comparative Example 6

[0111] The composition of the high-strength heavy metal solidification geopolymer based on lead-zinc tailings is the same as Example 1.

[0112] The preparation method of the above high-strength heavy metal solidification geopolymer based on lead-zinc tailings, the specific steps are:

[0113] Steps 1)-3) are the same as Example 1.

[0114] 4) Dissolve sodium hydroxide particles in deionized water to prepare a sodium hydroxide solution with a concentration of 10 mol / L, add water glass to the obtained sodium hydroxide solution to a sodium silicate modulus of 2.0, and stir and age for 24 h to obtain an alkali activator;

[0115] 5) Add 120 g of raw material A, 50 g of raw material B, 30 g of raw material C, and 60 g of the alkali activator to a blender, and stir in the blender until the slurry has a fluidity of 160 mm;

[0116] 6) Pour the slurry prepared in step 5) into a 40x40x40 mm 3 steel mold, perform vibration and exhaust (frequency 50 Hz, time length 30 s), then perform steam curing (80±5℃, humidity≥95%, 24 h), and then perform sealed curing (25±2℃, 7 days), to obtain a high-strength heavy metal solidified geopolymer based on lead-zinc tailings after demolding.

[0117] The heavy metal (Pb 2 + , Cd 2+ , Cu 2+ ) ion toxicity leaching experiments of the geopolymer based on lead-zinc tailings in Comparative Examples 2-6 were performed, and the results are shown in Table 2.

[0118] Table 2

[0119]

[0120] As can be seen from Table 2, the comprehensive performance of the geopolymer obtained in all the comparative examples is significantly poorer than that of the geopolymer of the present application. Specifically, the compressive strength of the geopolymer of all the comparative examples fails to reach 40 MPa, and the heavy metal ion leaching concentration is significantly higher. This result fully proves that only under the synergistic effect of the raw material ratio, specific pretreatment process of diatomite, and optimized mixing time sequence defined in the present application, can the balance between high strength and efficient heavy metal solidification be achieved.

[0121] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any changes or replacements easily thought of by those skilled in the art within the technical scope disclosed in the present application should be encompassed within the protection scope of the present application.

Claims

1. A high-strength heavy metal solidification geopolymer based on lead-zinc tailings, characterized in that, The raw materials include geopolymer precursors and alkali activators; By mass percentage, the geopolymer precursor comprises 50%-65% lead-zinc tailings, 20%-30% fly ash, and 10%-15% diatomite; The amount of the alkaline activator is 25%-35% of the mass of the geopolymer precursor.

2. The high-strength heavy metal solidification geopolymer based on lead-zinc tailings according to claim 1, characterized in that, The lead-zinc tailings comprise the following components: SiO2 45-60 wt.%, CaO 5-12 wt.%, Fe2O3 5-15 wt.%, Al2O3 8-12 wt.%, PbO 0.5-3 wt.%, and ZnO 1-5 wt.%.

3. The high-strength heavy metal solidification geopolymer based on lead-zinc tailings according to claim 1, characterized in that, The diatomaceous earth is calcined diatomaceous earth; the calcined diatomaceous earth is obtained by calcining diatomaceous earth at 300℃-500℃ for 2h-4h.

4. The high-strength heavy metal solidification geopolymer based on lead-zinc tailings according to claim 1, characterized in that, The fly ash is high-calcium fly ash, and the CaO content in the high-calcium fly ash is 15-30 wt.%.

5. The high-strength heavy metal solidification geopolymer based on lead-zinc tailings according to claim 1, characterized in that, The alkaline activator is a mixed solution of sodium hydroxide and water glass.

6. A method for preparing a high-strength heavy metal solidified geopolymer based on lead-zinc tailings as described in any one of claims 1-5, characterized in that, Includes the following steps: 1) Dry-mix lead-zinc tailings, fly ash, and diatomaceous earth to obtain geopolymer precursors; 2) Add an alkaline activator to the geopolymer precursor and stir to obtain a slurry; 3) The slurry is poured and cured to obtain the high-strength heavy metal solidified geopolymer based on lead-zinc tailings.

7. The preparation method according to claim 6, characterized in that, In step 1), before dry mixing, the lead-zinc tailings and fly ash are further ground to D50≤20μm respectively. Before dry mixing, the diatomaceous earth is further ground to D50≤20μm and then calcined at 300℃-500℃ for 2h-4h.

8. The preparation method according to claim 6, characterized in that, In step 2), the alkaline activator is prepared by dissolving sodium hydroxide in water to prepare a sodium hydroxide solution with a concentration of 10-12 mol / L; adding water glass to the sodium hydroxide solution according to a sodium silicate modulus of 2.0-2.5, and aging the solution by stirring to obtain the alkaline activator.

9. The preparation method according to claim 6, characterized in that, In step 2), the fluidity of the slurry is 160-180 mm.

10. The preparation method according to claim 6, characterized in that, In step 3), the curing includes sequential steam curing and sealing curing; The steam curing temperature is 80±5℃, the relative humidity is ≥95%, and the time is 24h; The temperature for the sealed curing process is 25±2℃, and the time is 7 days.

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