Red mud-based environmental remediation material and preparation method thereof

Abstract

The invention discloses a red-mud-based environmental remediation material, and relates to the technical field of environmental remediation materials. The red mud-based environmental remediation material is prepared by mixing modified red mud powder, modified zeolite, biochar, nanoscale zero-valent iron, biogel and an auxiliary additive according to the mass ratio of (50-55): (10-15): (12-16): (5-8): (10-15): (8-10), the modified red mud powder is lanthanum nitrate modified red mud powder, and the biogel is formed by copolymerizing polylactic acid and an epoxy compound in an inorganic alkali aqueous solution. The auxiliary additive is one of microbial powder and a lime compound; the modified red mud powder and the nanoscale zero-valent iron are used in cooperation, the repair capacity of the material is further improved by means of the high reducibility and heavy metal adsorption capacity of the nanoscale zero-valent iron on the basis that the adsorption capacity of the red mud is improved, and meanwhile the charcoal can also adsorb certain organic pollutants.

Description

Technical Field

[0001] The invention relates to the technical field of environmental restoration materials, and in particular to a red mud-based environmental restoration material and a preparation method thereof. Background Art

[0002] Red mud is industrial solid waste discharged when the aluminum industry extracts alumina. It is called red mud because it contains a large amount of iron oxide and its appearance is similar to red soil. With the development of the aluminum industry and the reduction of the grade of bauxite ore, the amount of red mud will become larger and larger. Red mud is an alkaline substance. With the flushing of rainwater, the alkali in the red mud will be dissolved. It contains a large amount of heavy metals and harmful substances, causing serious pollution to the environment.

[0003] At present, red mud is mostly used in environmental remediation materials after being treated with acid to remove heavy metals and other harmful substances. Existing red mud-based environmental remediation materials only perform some simple grinding or modification on the red mud to improve its adsorption effect. Although this method can improve the ability of red mud to adsorb heavy metals, its functionality is still relatively simple and needs to be used in combination with other functional materials for environmental management. At the same time, it is necessary to reasonably control the matching ratio to achieve the best environmental remediation effect, which is relatively cumbersome. Therefore, the present invention proposes a red mud-based environmental remediation material and a preparation method to solve the problems existing in the prior art. Summary of the invention

[0004] In view of the above problems, the purpose of the present invention is to provide a red mud-based environmental remediation material and a preparation method. The red mud-based environmental remediation material and the preparation method use modified red mud powder and nano zero-valent iron in combination, and on the basis of improving the adsorption capacity of red mud for heavy metal ions and pollutants, the strong reducibility and heavy metal adsorption capacity of nano zero-valent iron are used to further improve the remediation capacity of the material, and at the same time, biochar can also adsorb certain organic pollutants;

[0005] Modified zeolite can absorb water and nutrients and release them slowly at the same time, reducing the rate of water or nutrient loss in the environment. Auxiliary additives can adapt different targeted substances to different remediation objects, fundamentally changing the environmental ecology and enhancing the functionality of the material for environmental remediation.

[0006] To achieve the purpose of the present invention, the present invention is implemented through the following technical scheme: a red mud-based environmental remediation material, which is prepared by mixing modified red mud powder, modified zeolite, biochar, nano zero-valent iron, biogel and auxiliary additives, the mass ratio of the modified red mud powder, modified zeolite, biochar, nano zero-valent iron, biogel and auxiliary additives is 50-55:10-15:12-16:5-8:10-15:8-10, the modified red mud powder is prepared from lanthanum nitrate modified red mud powder, and the biogel is prepared by copolymerizing polylactic acid and epoxy compound mixed in an inorganic alkali aqueous solution.

[0007] A further improvement is that the auxiliary additive is one of microbial powder and lime complex, the epoxy compound is one of propylene oxide, epichlorohydrin and 1,2-butylene oxide, and the inorganic alkali aqueous solution is one of potassium hydroxide, sodium bicarbonate and potassium bicarbonate.

[0008] A further improvement is that the lime composite is prepared by mixing lime powder, potassium aluminum sulfate dodecahydrate and polyferric sulfate, wherein the mass ratio of lime powder, potassium aluminum sulfate dodecahydrate and polyferric sulfate is 60-70:20-25:15-20.

[0009] A method for preparing a red mud-based environmental restoration material comprises the following steps:

[0010] Step 1, modification of red mud, first using a diluted acid solution to acid-leach the red mud, then filtering it out, rinsing it with deionized water and drying it, then adding it to a lanthanum nitrate solution for static adsorption, and finally filtering it out, drying it and performing low-temperature roasting to obtain modified red mud powder;

[0011] Step 2, preparation of modified zeolite, first grinding the zeolite with a nano grinder, then treating it with acid and alkali solutions in sequence, and finally washing it with deionized water and drying it to obtain the modified zeolite;

[0012] Step 3: premixing the base material, first adding the modified red mud powder, modified zeolite and biochar into a stirring tank for mixing and stirring to obtain a premixed base material;

[0013] Step 4: preparing the binder by mixing the polylactic acid and the epoxy compound, and then adding the mixture into an inorganic alkali aqueous solution for copolymerization, and then extracting the polymer, washing it with ethanol, and mixing it with nano zero-valent iron to obtain the binder;

[0014] Step 5: Mixing and molding. The premixed base material and the binder are mixed and stirred to obtain a mixed material. The auxiliary additives are then added thereto, mixed, and poured into a molding device for molding and drying to obtain an environmental remediation material.

[0015] The further improvement is that: the diluted acid solution in the step 1 is one of 1 mol / L hydrochloric acid, 0.1 mol / L sulfuric acid and 0.1 mol / L nitric acid, and after acid leaching and rinsing, it is dried at 120°C for 1 hour and crushed to 200 mesh; the concentration of the lanthanum nitrate solution is 0.1 mol / L, and the mass ratio of red mud to lanthanum nitrate solution is 5:1; the standing time is 12 hours, and after filtering out, it is dried at 105°C for 2 hours, and then low-temperature roasted at 300°C for 1 hour.

[0016] A further improvement is that in step 2, an aqueous solution of ethylenediaminetetraacetic acid is first used for heating and acid leaching, then an aqueous solution of sodium hydroxide is used for heating and alkali treatment, and finally a disodium ethylenediaminetetraacetic acid solution is used for heating and pickling and then drying; after acid leaching, alkali treatment and pickling, distilled water is used for rinsing and drying.

[0017] Further improvements are: the concentration of the ethylenediaminetetraacetic acid aqueous solution is 0.18 mol / L; the concentration of the sodium hydroxide aqueous solution is 0.9 mol / L; the concentration of the disodium ethylenediaminetetraacetic acid aqueous solution is 0.11 mol / L; and the drying condition is drying at 130° C. for 4.5 hours.

[0018] Further improvements are: the biochar in step three is obtained by pyrolyzing rice husks and straw under anaerobic conditions at 500°C for 2 hours, and the nano zero-valent iron in step four is obtained by adding iron salt to sodium borohydride for reduction reaction, adding hexadecyltrimethylammonium bromide and polyvinylpyrrolidone for mixed reaction, centrifugally separating, washing and drying.

[0019] A further improvement is that in the step 4, the copolymerization mass ratio of polylactic acid, epoxy compound and inorganic alkali aqueous solution is 1:8:2, the concentration of the inorganic alkali aqueous solution is 5-8 mol / L, and the ethanol concentration is 95 wt%.

[0020] The beneficial effects of the present invention are as follows: the present invention uses modified red mud powder in combination with nano zero-valent iron, and on the basis of improving the adsorption capacity of red mud for heavy metal ions and pollutants, the strong reducibility and heavy metal adsorption capacity of nano zero-valent iron are used to further improve the repair capacity of the material, and at the same time, biochar can also adsorb certain organic pollutants;

[0021] Modified zeolite can absorb water and nutrients and release them slowly at the same time, reducing the rate of water or nutrient loss in the environment. Auxiliary additives can adapt different targeted substances to different remediation objects, fundamentally changing the environmental ecology and enhancing the functionality of the material for environmental remediation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention is a flow chart of the preparation method. DETAILED DESCRIPTION

[0023] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with examples. The examples are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

[0024] Example 1

[0025] according to Figure 1 As shown, this embodiment provides a red mud-based environmental remediation material, which is prepared by mixing modified red mud powder, modified zeolite, biochar, nano zero-valent iron, biogel and auxiliary additives in a mass ratio of 50:10:15:5:10:10, wherein the modified red mud powder is prepared from lanthanum nitrate-modified red mud powder, and the biogel is prepared by copolymerizing polylactic acid and propylene oxide in a potassium hydroxide aqueous solution; the auxiliary additive is microbial powder, which is directly purchased and contains nitrogen-fixing bacteria, phosphate-solubilizing bacteria, potassium-solubilizing bacteria and other bacteria that are beneficial to plant growth.

[0026] The nitrogen-fixing bacteria, phosphate-solubilizing bacteria and potassium-solubilizing bacteria are round brown nitrogen-fixing bacteria, micrococcus and silicate bacteria, respectively; round brown nitrogen-fixing bacteria was purchased from China Center for Type Culture Collection with the accession number of CCTCC NO: M2016110; silicate bacteria was purchased from China Center for Type Culture Collection of Wuhan University with the accession number of CCTCC No.M200040; micrococcus was purchased from General Microbiology Center of China Microorganism Culture Collection with the accession number of CGMCC No.7778.

[0027] A method for preparing a red mud-based environmental restoration material comprises the following steps:

[0028] Step 1, modification of red mud, first use 1 mol / L hydrochloric acid to acid-leach the red mud, then filter it out, rinse it with deionized water, dry it at 120°C for 1 hour and crush it to 200 mesh, then add it to a 0.1 mol / L lanthanum nitrate solution and let it stand for adsorption for 12 hours, wherein the mass ratio of red mud to lanthanum nitrate solution is 5:1, finally filter it out, dry it at 105°C for 2 hours and low-temperature roast it at 300°C for 1 hour to obtain modified red mud powder.

[0029] Step 2, preparation of modified zeolite, first grinding the zeolite with a nano grinder, then treating it with acid and alkali solutions in sequence, and finally washing it with deionized water and drying it to obtain the modified zeolite;

[0030] Specifically, a 0.18 mol / L ethylenediaminetetraacetic acid aqueous solution is first used for oil bath heating at 95°C for acid immersion treatment, then a 0.9 mol / L sodium hydroxide aqueous solution is used for oil bath heating at 95°C for alkali treatment, and finally a 0.11 mol / L disodium ethylenediaminetetraacetic acid solution is used for oil bath heating at 95°C for acid washing and then drying; after acid immersion, alkali treatment and acid washing, distilled water is used for rinsing and dried at 130°C for 4.5 hours.

[0031] Step 3: premixing the base material, first adding the modified red mud powder, modified zeolite and biochar into a stirring tank for mixing and stirring to obtain a premixed base material;

[0032] The biochar was obtained by pyrolysis of rice husk and straw at 500℃ under anaerobic conditions for 2h.

[0033] Step 4: preparing the binder by mixing polylactic acid and propylene oxide, and then adding them into a 5 mol / L potassium hydroxide aqueous solution for copolymerization, then extracting the polymer, washing it with 12 mol / L ethanol, and mixing it with nano zero-valent iron to obtain a binder;

[0034] The copolymerization mass ratio of polylactic acid, propylene oxide and potassium hydroxide aqueous solution is 1:8:2; the nano zero-valent iron is prepared by adding iron salt to sodium borohydride for reduction reaction, adding hexadecyltrimethylammonium bromide and polyvinylpyrrolidone for mixed reaction, centrifugation separation, washing and drying.

[0035] Step 5, mixing and molding treatment, mixing and stirring the premixed base material and the binder to obtain a mixed material, then adding microbial powder into the mixed material, pouring the mixture into a molding device, molding and drying, and obtaining an environmental remediation material.

[0036] The environmental remediation material in this embodiment is prepared for soil contaminated by heavy metals. While adsorbing and removing heavy metals, microbial powder is used to increase the number of nitrogen-fixing, phosphate-dissolving and potassium-dissolving bacteria in the soil, and modified zeolite is used to fundamentally repair the soil environment. The increase in microbial flora improves the self-generation ability of soil nutrients, reduces the application of chemical nutrients, and protects the structure of the soil.

[0037] Example 2

[0038] according to Figure 1 As shown, this embodiment provides a red mud-based environmental remediation material, which is prepared by mixing modified red mud powder, modified zeolite, biochar, nano zero-valent iron, biogel and auxiliary additives in a mass ratio of 55:10:12:5:10:8, wherein the modified red mud powder is prepared from red mud powder modified by lanthanum nitrate, and the biogel is prepared by copolymerizing polylactic acid and epichlorohydrin in a potassium bicarbonate aqueous solution.

[0039] The auxiliary additive is a lime compound, which is prepared by mixing lime powder, potassium aluminum sulfate dodecahydrate and polyferric sulfate, wherein the mass ratio of lime powder, potassium aluminum sulfate dodecahydrate and polyferric sulfate is 65:20:15.

[0040] A method for preparing a red mud-based environmental restoration material comprises the following steps:

[0041] Step 1, modification of red mud, first use 0.1 mol / L nitric acid to acid-leach the red mud, then filter it out, rinse it with deionized water, dry it at 120°C for 1 hour and crush it to 200 mesh, then add it into 0.1 mol / L lanthanum nitrate solution and let it stand for adsorption for 12 hours, wherein the mass ratio of red mud to lanthanum nitrate solution is 5:1, finally filter it out, dry it at 105°C for 2 hours and low-temperature roast it at 300°C for 1 hour to obtain modified red mud powder.

[0042] Step 2, preparation of modified zeolite, first grinding the zeolite with a nano grinder, then treating it with acid and alkali solutions in sequence, and finally washing it with deionized water and drying it to obtain the modified zeolite;

[0043] Specifically, a 0.18 mol / L ethylenediaminetetraacetic acid aqueous solution is first used for oil bath heating at 95°C for acid immersion treatment, then a 0.9 mol / L sodium hydroxide aqueous solution is used for oil bath heating at 95°C for alkali treatment, and finally a 0.11 mol / L disodium ethylenediaminetetraacetic acid solution is used for oil bath heating at 95°C for acid washing and then drying; after acid immersion, alkali treatment and acid washing, distilled water is used for rinsing and dried at 130°C for 4.5 hours.

[0044] Step 3: premixing the base material, first adding the modified red mud powder, modified zeolite and biochar into a stirring tank for mixing and stirring to obtain a premixed base material;

[0045] The biochar was obtained by pyrolysis of rice husk and straw in a mixture ratio of 1:2 at 500°C under anaerobic conditions for 2 h.

[0046] Step 4: Mixing and preparing the binder: first, polylactic acid and epichlorohydrin are mixed, and then added into a 7 mol / L potassium bicarbonate aqueous solution for copolymerization reaction; then, the polymer is extracted, washed with 12 mol / L ethanol, and then mixed with nano zero-valent iron to obtain a binder;

[0047] The copolymerization mass ratio of polylactic acid, epichlorohydrin and potassium bicarbonate aqueous solution is 1:8:2; nano zero-valent iron is prepared by adding iron salt to sodium borohydride for reduction reaction, adding hexadecyltrimethylammonium bromide and polyvinylpyrrolidone for mixed reaction, centrifugation separation, washing and drying.

[0048] Step 5: Mixing and molding. The premixed base material and the binder are mixed and stirred to obtain a mixed material. The lime compound is then added thereto, mixed, and poured into a molding device for molding and drying to obtain an environmental remediation material.

[0049] The environmental remediation material in this embodiment is prepared for water bodies polluted by heavy metals. While using modified red mud powder and nano zero-valent iron to adsorb and reduce heavy metal pollution, pollutants are adsorbed by biochar, and at the same time, lime complexes are used to adsorb and flocculate pollutants in the water. The dual treatment effectively improves the remediation effect of the water environment.

[0050] The following is a comparison of the treatment experiments of the materials in Example 1 and Example 2 with commercially available heavy metal contaminated soil treatment materials, heavy metal contaminated water treatment materials and single modified red mud materials. The commercially available heavy metal contaminated soil treatment material is Woyuan heavy metal passivator (soil conditioner), the heavy metal contaminated water treatment material is Kaidefei KDF055 (water treatment material), and the modification method of the single modified red mud material is the same as the modification treatment method of the present application. Then, the materials prepared in Example 1, the commercially available soil conditioner and the single modified red mud material are used to treat the heavy metal contaminated soil. The material prepared in Example 2, commercially available water treatment materials and a single modified red mud material were used to treat heavy metal contaminated water bodies. The remediation materials were applied in equal weights and volumes to contaminated soil and water bodies. The soil was mixed and moistened by spreading and waiting for 15-20 days. The water was stirred and left to stand for 2-3 days. Finally, the content of heavy metals and pollutants in the soil and water bodies was detected. The results are shown in Tables 1 and 2 below. Comprehensive pollutants refer to other pollutants that affect soil and water bodies except heavy metal pollution elements. Nutrient content refers to the comprehensive content of nitrogen, phosphorus and potassium in the soil that can be absorbed and utilized by plants.

[0051] Table 1 Heavy metal contaminated soil treatment experiment

[0052]

[0053]

[0054] It can be seen from Table 1 above that the embodiment of the present application has better adsorption capacity for heavy metals and comprehensive pollutants than the single use of modified red mud. This is because nano zero-valent iron and other adsorptive substances are also added in the present application, which can effectively adsorb harmful substances and repair the soil ecological environment. The increased microbial powder decomposition produces nutrients to further increase the nutrient content in the repaired soil.

[0055] Table 2 Heavy metal pollution water treatment experiment

[0056]

[0057] It can be seen from Table 2 above that the heavy metal content in the water body after treatment with the repair material in Example 2 is significantly reduced, and the amount of reduction is much greater than the traditional use of a single modified red mud and traditional water treatment materials. The adsorption effect is good, and the effect of water environment treatment is significantly improved.

[0058] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A red mud-based environmental restoration material, Features: The environmental restoration material is prepared by mixing modified red mud powder, modified zeolite, biochar, nano zero-valent iron, biogel and auxiliary additives, wherein the mass ratio of the modified red mud powder, modified zeolite, biochar, nano zero-valent iron, biogel and auxiliary additives is 50-55:10-15:12-16:5-8:10-15:8-10, the modified red mud powder is prepared from lanthanum nitrate modified red mud powder, and the biogel is prepared by copolymerizing polylactic acid and epoxy compounds in an inorganic alkali aqueous solution.

2. A red mud-based environmental restoration material according to claim 1, Features: The auxiliary additive is one of microbial powder and lime complex, the epoxy compound is one of propylene oxide, epichlorohydrin and 1,2-butylene oxide, and the inorganic alkali aqueous solution is one of potassium hydroxide, sodium bicarbonate and potassium bicarbonate.

3. A red mud-based environmental restoration material according to claim 2, Features: The lime composite is prepared by mixing lime powder, potassium aluminum sulfate dodecahydrate and polyferric sulfate, wherein the mass ratio of lime powder, potassium aluminum sulfate dodecahydrate and polyferric sulfate is 60-70:20-25:15-20.

4. A method for preparing a red mud-based environmental remediation material, It is characterized in that The following steps are involved: Step 1, modification of red mud, firstly using a diluted acid solution to acid-leach the red mud, filtering out the red mud, rinsing it with deionized water and drying it, then adding it to a lanthanum nitrate solution for static adsorption, finally filtering out the red mud, drying it and performing low-temperature roasting to obtain modified red mud powder; Step 2, preparation of modified zeolite, first grinding the zeolite, then treating it with an acid solution and an alkali solution in sequence, and finally washing it with deionized water and drying it to obtain the modified zeolite; Step 3: premixing the base material, firstly mixing the modified red mud powder, the modified zeolite and the biochar to obtain a premixed base material; Step 4: preparing the binder by mixing the polylactic acid and the epoxy compound, and then adding the mixture into an inorganic alkali aqueous solution for copolymerization, and then extracting the polymer, washing it with ethanol, and mixing it with nano zero-valent iron to obtain the binder; Step 5: Mixing and molding treatment: the premixed base material and the binder are mixed and stirred to obtain a mixed material, and then auxiliary additives are added thereto, mixed, molded and dried to obtain an environmental remediation material.

5. A method for preparing a red mud-based environmental restoration material according to claim 4, Features: The diluted acid solution in the step 1 is one of 1 mol / L hydrochloric acid, 0.1 mol / L sulfuric acid and 0.1 mol / L nitric acid. After acid leaching and rinsing, it is dried at 120°C for 1 hour and crushed to 200 meshes. The concentration of the lanthanum nitrate solution is 0.1 mol / L, and the mass ratio of red mud to lanthanum nitrate solution is 5:

1. The standing time is 12 hours, and after filtering, it is dried at 105°C for 2 hours, and then low-temperature roasted at 300°C for 1 hour.

6. A method for preparing a red mud-based environmental restoration material according to claim 4, Features: Specifically, the step 2 includes first using an aqueous solution of ethylenediaminetetraacetic acid for heating and acid leaching, then using an aqueous solution of sodium hydroxide for heating and alkali treatment, and finally using a disodium ethylenediaminetetraacetic acid solution for heating and pickling and then drying; after the acid leaching, alkali treatment and pickling, distilled water is used for rinsing and drying.

7. The method for preparing a red mud-based environmental restoration material according to claim 6, Features: The concentration of the ethylenediaminetetraacetic acid aqueous solution is 0.18 mol / L; the concentration of the sodium hydroxide aqueous solution is 0.9 mol / L; the concentration of the disodium ethylenediaminetetraacetic acid aqueous solution is 0.11 mol / L; and the drying condition is drying at 130° C. for 4.5 hours.

8. The method for preparing a red mud-based environmental restoration material according to claim 4, Features: The biochar in step three is obtained by pyrolyzing rice husks and straw under anaerobic conditions at 500° C. for 2 hours. The nano zero-valent iron in step four is obtained by adding iron salt to sodium borohydride for reduction reaction, adding hexadecyltrimethylammonium bromide and polyvinylpyrrolidone for mixed reaction, centrifugally separating, washing and drying.

9. The method for preparing a red mud-based environmental restoration material according to claim 4, Features: In the step 4, the copolymerization reaction mass ratio of polylactic acid, epoxy compound and inorganic alkali aqueous solution is 1:8:2, the concentration of inorganic alkali aqueous solution is 5-8 mol / L, and the concentration of ethanol is 95wt%.

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