Solid-waste-based filling material for improving leaching rate of heavy metals and preparation method of solid-waste-based filling material

Abstract

The invention provides a solid waste-based filling material for improving the leaching rate of heavy metals and a preparation method thereof, and the filling material comprises the following raw materials in parts by weight: 40-60 parts of Bayer process red mud, 40-60 parts of fly ash, 10-20 parts of desulfurized gypsum, 5-8 parts of nano-hydroxyapatite, 4-6 parts of a pumping agent and 30-60 parts of water. The pumping agent is prepared by compounding an organic silicon polycarboxylic acid water reducing agent, polymaleic acid and sulfydryl modified cellulose according to the mass ratio of (4-6): 3: (10-12), and the sulfydryl modified cellulose is prepared by a method comprising the following steps: dissolving carboxymethyl cellulose in water, adding an amino thiol compound, adjusting the pH value, adding an activating agent and an activating auxiliary agent, and controlling the temperature to react, so as to obtain the sulfydryl modified cellulose. After the reaction is finished, adding acetone until no precipitate is generated, filtering, washing and drying to obtain sulfydryl modified cellulose; the heavy metal leaching performance of the filling material is improved by introducing hydroxyapatite which can be subjected to precipitation reaction with heavy metal and can also adsorb the heavy metal.

Description

Technical Field

[0001] The present invention belongs to the technical field of filling materials, and in particular relates to a solid waste-based filling material for improving heavy metal leaching rate and a preparation method thereof. Background Art

[0002] As the demand for mineral resources continues to expand, a large number of goafs generated by mining development are very likely to cause engineering safety and ecological environmental problems. At present, the main methods for managing goafs are filling method, collapse method, closure method and regional relocation. Among them, the filling method uses filling materials to fill the goaf to effectively control the ground pressure and prevent surface collapse. The state encourages all regions to give priority to the filling method for goaf treatment. Grouting filling is one of the most widely used filling methods because of its relatively simple construction process, light equipment and easy operation, strong adaptability to complex environments, no influence of weather and seasons, and the ability to complete filling operations in a relatively short time.

[0003] The materials used for grouting mainly include red mud, fly ash, slag, cement and other cementitious materials, and some admixtures are also included as needed, such as water reducing agent, setting regulator, early strength agent, etc. It can be seen that grouting can not only absorb the solid waste from power plants, steel mills, metal smelters, etc., and reduce the pressure of solid waste discharge, but also effectively reduce the surface subsidence caused by mining, and achieve the coordinated development of mining resources and environment.

[0004] The patent previously applied by the applicant (application number 2024118343993) discloses a solid waste-based filling material and its preparation method, which uses Bayer red mud and fly ash as the main gelling materials. Under the action of a pumping agent compounded with an alkali activator, a silicone polycarboxylic acid water-reducing agent, polymaleic acid, and water-soluble cellulose in a mass ratio of 3-5:3-5:10, the filling material can have excellent pumping performance and can also achieve optimal mechanical properties. Due to the lack of substances that can absorb heavy metals, or have strong complexing ability for heavy metals or other substances that can form precipitation in the filling material, the heavy metal leaching rate of the filling material is relatively high. Although polymaleic acid in the raw material of the pumping agent has a certain heavy metal complexing ability, there are a large number of competitive ions such as calcium ions, aluminum ions, iron ions, etc. in the filling material system, and in order to improve the pumpability, the surface of the red mud particles is coated with a thick and stable solvated water film, which greatly reduces the possibility of heavy metal ions forming complexes or entering the lattice to solidify. Therefore, it is necessary to further improve it to reduce the leaching rate of heavy metal ions without compromising the original performance. Summary of the invention

[0005] In order to solve the problem of high heavy metal ion leaching rate, the present invention improves the heavy metal leaching performance of the filling material by introducing hydroxyapatite into the filling material, which can not only react with heavy metals for precipitation but also adsorb heavy metals.

[0006] In order to achieve the above purpose, the following technical solutions are adopted:

[0007] A solid waste-based filling material for improving heavy metal leaching rate comprises the following raw materials in parts by weight: 40-60 parts of Bayer red mud, 40-60 parts of fly ash, 10-20 parts of desulfurized gypsum, 5-8 parts of nano-hydroxyapatite, 4-6 parts of pumping agent, and 30-60 parts of water, wherein the pumping agent is a compound of organosilicon polycarboxylic acid water reducer, polymaleic acid, and mercapto-modified cellulose in a mass ratio of 4-6:3:10-12, and the mercapto-modified cellulose is prepared by a method comprising the following steps: dissolving carboxymethyl cellulose in water, adding an aminothiol compound, adjusting the pH, adding an activator and an activation aid, reacting at a controlled temperature, adding acetone after the reaction is completed until no precipitation is generated, filtering, washing, and drying to obtain the mercapto-modified cellulose.

[0008] The mass volume ratio of the carboxymethyl cellulose to water is 3-5g:100mL. The aminothiol compound is selected from one or a combination of two or more of dithiobutylamine, β-mercaptoethylamine, 3-mercapto-1-propylamine, and 4-aminobutane-1-thiol; preferably dithiobutylamine. The degree of substitution of the carboxymethyl cellulose is 0.65-0.95, and the weight average molecular weight is 50,000-100,000. The amount of the aminothiol compound is 10-20wt% of the carboxymethyl cellulose, preferably 15-20wt%. The pH is adjusted to 4-6 with 3-5mol / L hydrochloric acid. The temperature control is to control the temperature at 20-40°C. The reaction time is 2-10h. The amount of the activator is 5-10wt% of the carboxymethyl cellulose, and the amount of the activation aid is 2-6wt% of the carboxymethyl cellulose. The activator is selected from one or a combination of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and 1-cyclohexyl-3-(2-morpholinoethyl)carbodiimide (CMC). The activation aid is selected from one or a combination of two or more of N-hydroxysuccinimide, 1-hydroxybenzotriazole, 3,4-dihydro-3-hydroxy-4-oxo-1,2,3-phenylpropanetriazine, 1-hydroxy-7-azabenzotriazole, and N-hydroxysulfosuccinimide. The washing is performed by washing with acetone and water alternately for 1-3 times, and the drying is performed at 60-80°C to constant weight.

[0009] The nano-hydroxyapatite has an average particle size of 10-50 nm and a specific surface area of ​​30-100 m 2 / g.

[0010] Nano-hydroxyapatite has a smaller particle size and a larger specific surface area. The added nano-hydroxyapatite will compete with Bayer red mud, fly ash and other particles to adsorb the pumping agent, reduce the distribution uniformity and effective adsorption amount of the pumping agent on the surface of other particles, weaken its water reduction and dispersion effects, and lead to reduced pumping performance. In order not to affect the pumping performance, the amount of pumping agent needs to be increased accordingly.

[0011] The relative molecular mass of the polymaleic acid is 600-1000.

[0012] The organosilicon polycarboxylate water reducer is prepared by a method comprising the following steps:

[0013] In an inert atmosphere, unsaturated carboxylic acid monomers, polyethylene glycol monoallyl ether and unsaturated silane monomers are used as polymerization monomers, an oxidation / reduction system initiator is used as the initiator, and under the action of a chain transfer agent, an aqueous solution free radical polymerization method is used to obtain the product.

[0014] The mass ratio of the unsaturated carboxylic acid monomer, polyethylene glycol monoallyl ether and unsaturated silane monomer is 1.5-2:2-4:0.8-1.

[0015] The unsaturated carboxylic acid monomer is selected from one or a combination of two or more of acrylic acid, methacrylic acid, fumaric acid, maleic anhydride and itaconic acid.

[0016] The number average molecular weight of the polyethylene glycol monoallyl ether is 1500-2400.

[0017] The unsaturated silane monomer is selected from one or a combination of two or more of triisopropylsilyl acrylate, acryloxytrimethylsilane, and acryloxymethyltrimethylsilane.

[0018] The polymerization temperature is 30-60°C and the polymerization reaction time is 1-3h. The mass fraction of the polymerized monomer in the aqueous solution is 40-60wt%. The amount of the reducing agent in the oxidation / reduction system is 0.5-1wt% of the mass of the carboxylic acid monomer, the polyethylene glycol monoallyl ether, and the silane monomer, and the reducing agent is selected from one or a combination of two or more of ascorbic acid, sodium sulfite, sodium hypophosphite, glucose, and bleaching powder. The amount of the oxidizing agent is 0.5-1wt% of the mass of the carboxylic acid monomer, the polyethylene glycol monoallyl ether, and the silane monomer, and is selected from one or a combination of two or more of hydrogen peroxide, ammonium persulfate, and potassium persulfate. The amount of the chain transfer agent is 0.3-0.5wt% of the mass of the carboxylic acid monomer, the polyethylene glycol monoallyl ether, and the silane monomer, and is selected from one or a combination of two or more of thioglycolic acid, 3-mercaptopropionic acid, and mercaptoethanol.

[0019] The fly ash is selected from one of Class I fly ash and Class II fly ash, or a combination of the two.

[0020] The present invention also provides a method for preparing the solid waste-based filling material for improving heavy metal leaching rate, comprising the following steps:

[0021] The Bayer red mud, fly ash, desulfurized gypsum and nano-hydroxyapatite are uniformly mixed to obtain a mixture 1, a pumping agent and water are uniformly mixed to obtain a mixture 2, and the mixture 1 and the mixture 2 are uniformly mixed to obtain a solid waste-based filling material.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The invention improves the heavy metal leaching performance of the filling material by introducing hydroxyapatite which can not only react with the heavy metal to precipitate but also adsorb the heavy metal into the filling material. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with specific embodiments, but is not limited to the contents of the specification. Unless otherwise specified, the "parts" described in the embodiments of the present invention are all parts by weight. The reagents used are all commercially available reagents in the art.

[0025] Carboxymethyl cellulose product number E012219, MW90000, degree of substitution DS=0.7, purchased from Anaiji Chemical.

[0026] The average particle size of nano-hydroxyapatite is 20nm and the specific surface area is 50m 2 / g, purchased from Wuhan Lanabai Pharmaceutical Chemical Co., Ltd.

[0027] Polyethylene glycol monoallyl ether 2400 (number average molecular weight 2400) and polyethylene glycol monoallyl ether 1500 (number average molecular weight 1500) were purchased from Hai'an Petrochemical Plant, Jiangsu Province.

[0028] Polymaleic acid with relative molecular weight of 600 and 1000 were purchased from Sinochem.

[0029] Bayer red mud and Class I fly ash were purchased from Hebei Wenfeng New Materials Co., Ltd.; desulfurized gypsum was purchased from Shangqiu Tianyuan Desulfurized Gypsum Co., Ltd. The oxide compositions of the above three raw materials are shown in Table 1:

[0030] Table 1 Raw material oxide composition

[0031]

[0032]

[0033] Example 1

[0034] 1) Dissolve 50g of carboxymethyl cellulose E012219 in 1000mL of water, add 10g of dithiobutylamine, adjust the pH to 4 with 3mol / L hydrochloric acid, add 5g of activator 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 1g of activating aid N-hydroxysuccinimide, control the temperature at 20°C for 7h, add acetone after the reaction until no precipitation is produced, filter, wash with acetone and water alternately for 3 times, and dry at 80°C to constant weight to obtain thiol-modified cellulose.

[0035] 2) Under a nitrogen atmosphere, 200 g of acrylic acid, 200 g of polyethylene glycol monoallyl ether 2400, 80 g of triisopropyl acrylate, and 1.4 g of potassium persulfate were added to 720 g of water, and the temperature was raised to 60 ° C to mix the monomer solution evenly. After 30 minutes, a solution of 2.8 g of ascorbic acid, 0.84 g of mercaptoethanol, and 3.36 g of water was added dropwise, and the polymerization reaction was carried out for 3 hours. After the reaction, the pH was adjusted to 7 with sodium hydroxide, and the water was removed by distillation under reduced pressure to obtain a silicone polycarboxylic acid water reducer with a weight average molecular weight of 124,000.

[0036] 3) 60 g of Bayer red mud, 40 g of grade I fly ash, 10 g of desulfurized gypsum, and 8 g of nano-hydroxyapatite are mixed evenly to obtain mixture 1; 6 g of a pumping agent prepared by mixing organosilicon polycarboxylic acid water reducer, polymaleic acid with a relative molecular mass of 1000, and mercapto-modified cellulose in a mass ratio of 6:3:12 and 38 g of water are mixed evenly to obtain mixture 2; mixture 1 and mixture 2 are mixed evenly to obtain a solid waste-based filling material.

[0037] Example 2

[0038] The rest is the same as Example 1, except that in step 1), an equal amount of 4-aminobutane-1-thiol is used to replace dithiobutylamine.

[0039] Example 3

[0040] The rest is the same as Example 1, except that in step 1), the amount of dithiobutylamine used is 5 g.

[0041] Example 4

[0042] The rest is the same as Example 1, except that in step 3), the amount of nano-hydroxyapatite used is 5 g.

[0043] Example 5

[0044] The rest is the same as Example 1, except that in step 3), the amount of pumping agent used is 4 g.

[0045] Example 6

[0046] The rest is the same as Example 1, except that in step 3), the pumping agent is compounded with an organosilicon polycarboxylic acid water reducer, polymaleic acid with a relative molecular mass of 1000, and mercapto-modified cellulose in a mass ratio of 6:3:10.

[0047] Example 7

[0048] 1) Dissolve 50g of carboxymethyl cellulose E012219 in 1000mL of water, add 10g of dithiobutylamine, adjust the pH to 4 with 3mol / L hydrochloric acid, add 5g of activator 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 1g of activating aid N-hydroxysuccinimide, control the temperature at 20°C for 7h, add acetone after the reaction until no precipitation is produced, filter, wash with acetone and water alternately for 3 times, and dry at 80°C to constant weight to obtain thiol-modified cellulose.

[0049] 2) Under a nitrogen atmosphere, 200 g of acrylic acid, 200 g of polyethylene glycol monoallyl ether 1500, 80 g of triisopropyl acrylate, and 1.4 g of potassium persulfate were added to 720 g of water, and the temperature was raised to 60 ° C to mix the monomer solution evenly. After 30 minutes, a solution of 2.8 g of ascorbic acid, 0.84 g of mercaptoethanol, and 3.36 g of water was added dropwise, and the polymerization reaction was carried out for 3 hours. After the reaction, the pH was adjusted to 7 with sodium hydroxide, and the water was removed by distillation under reduced pressure to obtain a silicone polycarboxylic acid water reducer with a weight average molecular weight of 124,000.

[0050] 3) 40 g of Bayer red mud, 60 g of grade I fly ash, 10 g of desulfurized gypsum, and 8 g of nano-hydroxyapatite are mixed evenly to obtain mixture 1; 6 g of a pumping agent prepared by mixing organosilicon polycarboxylic acid water reducer, polymaleic acid with a relative molecular mass of 600, and mercapto-modified cellulose in a mass ratio of 4:3:12 and 38 g of water are mixed evenly to obtain mixture 2; mixture 1 and mixture 2 are mixed evenly to obtain a solid waste-based filling material.

[0051] Comparative Example 1

[0052] The rest is the same as Example 1, except that in step 3), nano hydroxyapatite is not added.

[0053] Comparative Example 2

[0054] 1) Under nitrogen atmosphere, 200g acrylic acid, 200g polyethylene glycol monoallyl ether 2400, 80g triisopropyl acrylate, and 1.4g potassium persulfate were added to 720g water, and the temperature was raised to 60°C to mix the monomer solution evenly. After 30min, a solution of 2.8g ascorbic acid, 0.84g mercaptoethanol, and 3.36g water was added dropwise, and the polymerization reaction was carried out for 3h. After the reaction, the pH was adjusted to 7 with sodium hydroxide, and water was removed by distillation under reduced pressure to obtain a silicone polycarboxylic acid water reducer with a weight average molecular weight of 124,000.

[0055] 2) 60 g of Bayer red mud, 40 g of grade I fly ash, 10 g of desulfurized gypsum, and 8 g of nano-hydroxyapatite are mixed evenly to obtain mixture 1; 6 g of a pumping agent prepared by mixing silicone polycarboxylic acid water reducer, polymaleic acid with a relative molecular mass of 1000, and carboxymethyl cellulose E012219 in a mass ratio of 6:3:12 and 38 g of water are mixed evenly to obtain mixture 2; mixture 1 and mixture 2 are mixed evenly to obtain a solid waste-based filling material.

[0056] That is, compared with Example 1, carboxymethyl cellulose E012219 is not modified with thiol groups.

[0057] Application Examples

[0058] The filling materials prepared in the above examples and comparative examples were subjected to the following performance tests:

[0059] 1. Fluidity: Refer to Appendix A.0.2 Fluidity Test in the standard GB / T 50448-2008 Technical Specification for Cement-based Grouting Materials, which requires that the initial expansion be ≥290mm, the 30min fluidity retention value be ≥260mm, and the initial fluidity and 30min fluidity retention value be recorded.

[0060] 2. Water seepage performance: Test with reference to the water seepage test standard in GB / T 50080-2002 Concrete mixture performance test method standard.

[0061] 3. Compressive strength: Tested in accordance with GB / T 50081-2002 Practical Standard for Test Methods of Mechanical Properties of Ordinary Concrete.

[0062] 4. Environmental toxicity leaching risk test: refer to the methods and steps of the national standard "Solid Waste Leaching Toxicity Leaching Method Horizontal Oscillation Method" (HJ557-2009), and use inductively coupled plasma mass spectrometer (ICP-MS) to determine the harmful ion content in the leaching solution.

[0063] Table 2 Performance test results

[0064]

[0065] Table 3 Performance test results

[0066]

[0067] It can be seen from the performance test results in Tables 2 and 3 that the leaching rate of heavy metal ions can be reduced without impairing the original performance of the filling material by adding hydroxyapatite, modifying the carboxymethyl cellulose with thiol groups, and appropriately adjusting the amount of the pumping agent.

[0068] It can be clearly seen from Examples 1-3, 6 and Comparative Example 2 that mercapto-modified cellulose has a significant effect on the leaching of divalent heavy metals. The possible reason is that mercapto-modified cellulose can form a transfer channel for divalent heavy metal ions in the solvated water film, and accurately transport the divalent heavy metal ions to the active sites of cementitious materials such as red mud and fly ash for fixation.

[0069] From Example 1, Example 4 and Comparative Example 1, it can be seen that nano-hydroxyapatite has excellent solidification ability for heavy metals in the filling material. From Example 1, Comparative Example 1 and Comparative Example 2, it can be seen that nano-hydroxyapatite and the mercapto-modified cellulose in the pumping agent have the effect of synergistically reducing the leaching rate of heavy metal ions.

[0070] The above detailed description is a specific description of one feasible embodiment of the present invention. The embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not deviate from the present invention should be included in the scope of the technical solution of the present invention.

Claims

1. A solid waste-based filling material for improving heavy metal leaching rate, characterized in that: The invention comprises the following raw materials in parts by weight: 40-60 parts of Bayer red mud, 40-60 parts of fly ash, 10-20 parts of desulfurized gypsum, 5-8 parts of nano-hydroxyapatite, 4-6 parts of pumping agent and 30-60 parts of water. The pumping agent is a compound of organosilicon polycarboxylic acid water reducer, polymaleic acid and mercapto-modified cellulose in a mass ratio of 4-6:3:10-12. The mercapto-modified cellulose is prepared by a method comprising the following steps: dissolving carboxymethyl cellulose in water, adding aminothiol compounds, adjusting pH, adding activators and activation aids, reacting at controlled temperature, adding acetone after the reaction is completed until no precipitation is generated, filtering, washing and drying to obtain mercapto-modified cellulose.

2. The solid waste-based filling material for improving heavy metal leaching rate according to claim 1, characterized in that: The aminothiol compound is selected from one or a combination of two or more of dithiobutylamine, β-mercaptoethylamine, 3-mercapto-1-propylamine, and 4-aminobutane-1-thiol; preferably dithiobutylamine; the carboxymethyl cellulose has a degree of substitution of 0.65-0.95 and a weight average molecular weight of 50,000-100,000.

3. The solid waste-based filling material for improving heavy metal leaching rate according to claim 1, characterized in that: The amount of the aminothiol compound used is 10-20wt% of the carboxymethyl cellulose, preferably 15-20wt%; the mass volume ratio of the carboxymethyl cellulose to water is 3-5g:100mL.

4. The solid waste-based filling material for improving heavy metal leaching rate according to claim 1, characterized in that: The amount of the activator is 5-10wt% of the carboxymethyl cellulose, and the amount of the activation aid is 2-6wt% of the carboxymethyl cellulose; the activator is selected from one or a combination of two of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 1-cyclohexyl-3-(2-morpholinoethyl)carbodiimide; the activation aid is selected from one or a combination of two or more of N-hydroxysuccinimide, 1-hydroxybenzotriazole, 3,4-dihydro-3-hydroxy-4-oxo-1,2,3-phenylpropanetriazine, 1-hydroxy-7-azabenzotriazole, and N-hydroxysulfosuccinimide.

5. The solid waste-based filling material for improving heavy metal leaching rate according to claim 1, characterized in that: The pH is adjusted to 4-6 using 3-5 mol / L hydrochloric acid; the temperature is controlled at 20-40° C.; and the reaction time is 2-10 h.

6. The solid waste-based filling material for improving heavy metal leaching rate according to claim 1, characterized in that: The nano-hydroxyapatite has an average particle size of 10-50 nm and a specific surface area of ​​30-100 m 2 / g.

7. The solid waste-based filling material for improving heavy metal leaching rate according to claim 1, characterized in that: The relative molecular mass of the polymaleic acid is 600-1000.

8. The solid waste-based filling material for improving heavy metal leaching rate according to claim 1, characterized in that: The organosilicon polycarboxylate water reducer is prepared by a method comprising the following steps: In an inert atmosphere, unsaturated carboxylic acid monomers, polyethylene glycol monoallyl ether and unsaturated silane monomers are used as polymerization monomers, an oxidation / reduction system initiator is used as the initiator, and under the action of a chain transfer agent, an aqueous solution free radical polymerization method is used to obtain the product.

9. The solid waste-based filling material for improving heavy metal leaching rate according to claim 1, characterized in that: The mass ratio of the unsaturated carboxylic acid monomer, polyethylene glycol monoallyl ether, and unsaturated silane monomer is 1.5-2:2-4:0.8-1; the unsaturated carboxylic acid monomer is selected from one or a combination of two or more of acrylic acid, methacrylic acid, fumaric acid, maleic anhydride, and itaconic acid; the number average molecular weight of the polyethylene glycol monoallyl ether is 1500-2400; the unsaturated silane monomer is selected from one or a combination of two or more of triisopropylsilyl acrylate, acryloxytrimethylsilane, and acryloxymethyltrimethylsilane.

10. The method for preparing a solid waste-based filling material for improving heavy metal leaching rate according to any one of claims 1 to 9, characterized in that: The steps include: The Bayer red mud, fly ash, desulfurized gypsum and nano-hydroxyapatite are uniformly mixed to obtain a mixture 1, a pumping agent and water are uniformly mixed to obtain a mixture 2, and the mixture 1 and the mixture 2 are uniformly mixed to obtain a solid waste-based filling material.

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