Method for preparing artificial planting soil from red mud and application

Abstract

The invention relates to the technical field of red mud treatment, in particular to artificial planting soil, a method for preparing the artificial planting soil from red mud and application of the artificial planting soil. Red mud is strongly alkaline and cannot be directly used as planting soil. The method comprises the following steps: curing red mud by using cement, preparing a porous light foam slurry from a mixed slurry by using a soil structure restorer, curing, crushing and granulating to obtain porous light artificial soil particles with strength, adjusting the pH value of the particles by using a phosphoric acid soaking method, and finally obtaining the artificial planting soil meeting the planting soil standard. Compared with traditional open-air stockpiling, the method has the advantages that the red mud can be effectively reutilized at low cost and prepared into the planting soil for plant growth.

Description

Technical Field

[0001] The invention relates to the technical field of red mud treatment, and in particular to artificial planting soil, a method for preparing the artificial planting soil by using red mud, and applications of the artificial planting soil. Background Art

[0002] Red mud is an industrial solid waste discharged after alumina is extracted from bauxite. It can be divided into sintering red mud, Bayer red mud and combined red mud (i.e. sintering and Bayer combined) according to its production method. my country's annual alumina production exceeds 1 million tons, and 1 to 2 tons of red mud are produced for every ton of alumina produced. With the expansion of the aluminum industry and the reduction of aluminum ore grade, the output of red mud will increase year by year.

[0003] At present, most red mud is simply treated and then stored in open-air piles by alumina plants near dams. This not only occupies a large amount of land resources, but also causes serious pollution to the surrounding atmosphere, water, soil, microorganisms and other environments. In addition, long-term accumulation treatment poses a safety hazard to the local environment. Summary of the invention

[0004] The purpose of the present invention is to provide an artificial planting soil, a method for preparing the artificial planting soil using red mud, and the application of the artificial planting soil. The present invention can not only alleviate the safety and environmental problems caused by the large amount of red mud accumulation, but also realize the low-carbon value-added utilization of red mud in artificial soil materials.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing artificial planting soil using red mud, comprising the following steps:

[0007] mixing red mud, cement and water to obtain a mixed slurry;

[0008] Physically foaming the soil structure restoration agent to form prefabricated foam to obtain a foamy soil structure restoration liquid;

[0009] The foamed soil structure recovery liquid is mixed with the mixed slurry, and the obtained foamed slurry is cured and then crushed and granulated to obtain artificial soil particles;

[0010] soaking the artificial soil particles in a phosphoric acid solution, filtering, and obtaining modified artificial soil particles;

[0011] The modified artificial soil particles are mixed with organic matter to obtain artificial planting soil.

[0012] Preferably, the mass of the red mud is 20-30% of the total mass of the red mud and cement.

[0013] Preferably, the water-to-solid mass ratio in the mixed slurry is 0.5-0.6:1.

[0014] Preferably, based on the total weight of the soil structure restoration agent being 100%, the soil structure restoration agent comprises the following components in percentage by weight: 0.1 to 1 wt% surfactant, 0.1 to 1 wt% foam stabilizer, 0.05 to 1 wt% enhancer, and the balance being water;

[0015] The foam stabilizer comprises one or more of nano kaolin, nano bentonite, nano silicon dioxide, nano attapulgite and nano montmorillonite;

[0016] The reinforcing agent includes cellulose and / or cellulose derivatives.

[0017] Preferably, the mass of the soil structure restoration agent in the foamed soil structure restoration liquid is 6-8% of the total mass of the red mud and cement in the mixed slurry.

[0018] Preferably, the mass concentration of the phosphoric acid solution is 1-5%, the number of immersions is 3-5 times, and the duration of each immersion is independently 4-6 hours.

[0019] Preferably, the mass content of organic matter in the artificial planting soil is 15-20%.

[0020] Preferably, the curing is natural curing, and the time of the natural curing is 14 to 28 days.

[0021] The present invention provides artificial planting soil prepared by the method described in the above scheme.

[0022] The present invention provides the use of the artificial planting soil described in the above scheme in plant planting.

[0023] The invention provides a method for preparing artificial planting soil by using red mud, comprising the following steps: mixing red mud, cement and water to obtain a mixed slurry; physically foaming a soil structure restoration agent to form prefabricated foam to obtain a foamy soil structure restoration liquid; mixing the foamy soil structure restoration liquid with the mixed slurry, and crushing and granulating the obtained foam slurry after curing to obtain artificial soil particles; soaking the artificial soil particles in a phosphoric acid solution, filtering to obtain modified artificial soil particles; and mixing the modified artificial soil particles with organic matter to obtain artificial planting soil.

[0024] Red mud itself is highly alkaline and cannot be used directly as planting soil. The present invention uses cement to solidify red mud, uses a soil structure restorer to prepare the mixed slurry into a porous and lightweight foam slurry, obtains strong porous and lightweight artificial soil particles through curing, crushing and granulation, and then adjusts the pH of the particles by soaking in phosphoric acid, and finally obtains artificial planting soil that meets the planting soil standards. Compared with traditional open-air storage, the present invention can effectively recycle red mud at a lower cost to prepare it into planting soil that can be used for plant growth.

[0025] The entire preparation process of the present invention is simple, cement can make the artificial planting soil form strong particles, and adding a soil structure restorer can improve the water absorption, water retention and air permeability of the artificial planting soil, making it more suitable for plant growth. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Photo of different plants growing in red mud artificial planting soil. DETAILED DESCRIPTION

[0027] The present invention provides a method for preparing artificial planting soil using red mud, comprising the following steps:

[0028] mixing red mud, cement and water to obtain a mixed slurry;

[0029] Physically foaming the soil structure restoration agent to form prefabricated foam to obtain a foamy soil structure restoration liquid;

[0030] The foamed soil structure recovery liquid is mixed with the mixed slurry, and the obtained foamed slurry is cured and then crushed and granulated to obtain artificial soil particles;

[0031] soaking the artificial soil particles in a phosphoric acid solution, filtering, and obtaining modified artificial soil particles;

[0032] The modified artificial soil particles are mixed with organic matter to obtain artificial planting soil.

[0033] The invention mixes red mud, cement and water to obtain mixed slurry.

[0034] Before the mixing, the present invention preferably cleans, dries and grinds the red mud. In the present invention, the particle size of the red mud after grinding is preferably less than 1 mm. The present invention has no other special requirements for the red mud.

[0035] In the present invention, the cement is preferably PO42.5 cement. The use of PO42.5 cement in the present invention is conducive to ensuring the strength of the artificial planting soil.

[0036] In the present invention, the mass of the red mud is preferably 20-30% of the total mass of the red mud and cement. In a specific embodiment, the mass of the red mud can be 20%, 23%, 25%, 28% or 30% of the total mass of the red mud and cement.

[0037] In the present invention, the mass of the water preferably satisfies the water-to-solid mass ratio in the mixed slurry of 0.5 to 0.6:1.

[0038] The present invention has no special requirements for the mixing process, and any method known in the art that can mix uniformly can be used.

[0039] The present invention physically foams the soil structure restoration agent to form prefabricated foam to obtain foamy soil structure restoration liquid.

[0040] In the present invention, the soil structure restoration agent preferably comprises the following components in percentage by weight: 0.1-1 wt% surfactant, 0.1-1 wt% foam stabilizer, 0.05-1 wt% enhancer, and the balance water.

[0041] Based on the total weight of the soil structure restoration agent as 100%, the soil structure restoration agent provided by the present invention includes 0.1-1wt% of a surfactant; in a specific embodiment of the present invention, the content of the surfactant may be 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt% or 0.7wt%. In the present invention, the surfactant preferably includes one or more of alkyl glycosides, saponins, fatty alcohol polyoxyethylene ethers, α-olefin sulfonates, fatty alcohol polyoxyethylene ether sulfates, fatty alcohol polyoxyethylene ether carboxylates, soapberry saponins, betulin, lupeol, γ-sitosterol, betaine, coconut oil amide acetate, palmitamidopropyl ethylenediamine and oenothermide, and more preferably alkyl glycosides. In the present invention, the functions of surfactants include: (1) surfactant molecular structure: surfactant molecules have two parts: hydrophilic (polar) and hydrophobic (non-polar). The hydrophilic part is usually composed of polar groups (such as carboxyl, sulfonic acid or amino groups), and the hydrophobic part is usually a long-chain hydrocarbon group; (2) reducing surface tension: when the surfactant is dissolved in water, its molecules will be arranged at the interface between water and air, with the hydrophilic end facing the water phase and the hydrophobic end facing the air phase. This arrangement can significantly reduce the surface tension of water, making it easier for water to form foam; (3) forming a monolayer: on the water surface, the surfactant molecules will form a monolayer of monolayers. This membrane structure can stabilize air bubbles and make them less likely to break; (4) formation of foam: when the aqueous solution is mechanically agitated or air is injected, the air will be wrapped in the surfactant molecule layer to form bubbles. Since the surfactant reduces the surface tension of water, these bubbles can exist relatively stably.

[0042] Taking the total weight of the soil structure restoration agent as 100%, the soil structure restoration agent provided by the present invention includes 0.1-1wt% of a foam stabilizer. In a specific embodiment of the present invention, the content of the foam stabilizer can be 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt% or 0.7wt%. In the present invention, the foam stabilizer preferably includes one or more of nano-kaolin, nano-bentonite, nano-silicon dioxide, nano-attapulgite and nano-montmorillonite, more preferably nano-silicon dioxide. In the present invention, the particle size of the foam stabilizer is preferably 40-100nm, more preferably 50-80nm. In the present invention, taking nano kaolin as an example, the effects of the foam stabilizer include: (1) particle size and distribution: nano kaolin and the like have extremely small particle size and large specific surface area, which allows them to be evenly distributed in the liquid, thereby increasing the viscosity of the liquid and reducing the rate of bubble rupture; (2) enhancing foam stability: nano kaolin particles and the like form a network structure on the bubble surface or in the foam. The presence of these particles can increase the mechanical strength of the foam and prevent the merging and rupture of the bubbles; (3) improving the rheology of the liquid: the addition of nano kaolin and the like can improve the rheological properties of the liquid, making the liquid more viscous, thereby making the foam more stable and reducing the foam rupture caused by the fluidity of the liquid; (4) adsorption: nano kaolin particles and the like can be adsorbed on the gas-liquid interface of the foam, thereby increasing the interfacial tension of the foam and further stabilizing the foam structure.

[0043] Taking the total weight of the soil structure restoration agent as 100%, the soil structure restoration agent provided by the present invention includes 0.05-1% of the reinforcing agent, preferably 0.05-0.8wt%. In a specific embodiment of the present invention, the content of the reinforcing agent can be 0.05wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt% or 0.7wt%. In the present invention, the reinforcing agent includes cellulose and / or cellulose derivatives. In the present invention, the cellulose derivative preferably includes methyl cellulose. In the present invention, the relative molecular weight of the cellulose is preferably 50000-300000, more preferably 100000-200000. In the present invention, the relative molecular weight of the methyl cellulose is preferably 50000-300000, more preferably 100000-200000. In the present invention, taking cellulose as an example, the effects of the enhancer include: (1) increasing the viscosity of the solution: cellulose is a high molecular polymer that can form a high viscosity solution in water. The high viscosity solution can slow down the flow rate of the liquid in the bubble film, thereby reducing the rupture and merging of the foam and improving the stability of the foam; (2) forming a network structure: cellulose molecular chains can form a three-dimensional network structure in the aqueous solution. This structure can effectively surround and support the bubbles, prevent the merging of bubbles and the discharge of liquid, thereby extending the life of the foam; (3) adsorption at the gas-liquid interface: cellulose molecules can be adsorbed on the gas-liquid interface of the bubbles to form a dense protective film. This layer of film can increase the elasticity and toughness of the bubble membrane and reduce the damage to the bubbles caused by external stress; (4) Prevent bubble merging: Cellulose can effectively prevent bubble merging by increasing the strength of the foam liquid membrane, that is, the membrane between the bubbles breaks and forms larger bubbles, thus maintaining the fineness and uniformity of the foam; (5) Improve the rheological properties of the foam: The presence of cellulose in the solution increases the yield stress and elastic modulus of the solution, which makes the foam show better elastic recovery under the action of external force, thereby resisting the collapse and deformation of the foam.

[0044] The present invention has no special requirements on the preparation method of the soil structure restoring agent, and the components can be directly mixed evenly.

[0045] In the present invention, the role of the soil structure restoring agent is to improve the soil structure so that it can retain water, be breathable, and reduce soil compressibility.

[0046] The present invention has no special requirements for the implementation process of the physical foaming, and the physical foaming process known in the art can be used. In the present invention, the physical foaming multiple is preferably 20 to 30 times; the physical foaming to a foam density is preferably 60 to 80 g / L, the foam 1 hour sedimentation distance is preferably 20 to 30 mm, and the 1 hour water bleeding rate is 30 to 50%.

[0047] After obtaining the mixed slurry and the foamy soil structure recovery liquid, the present invention mixes the foamy soil structure recovery liquid with the mixed slurry to obtain the foamy slurry.

[0048] In the present invention, the mass of the soil structure restoration agent in the foamed soil structure restoration liquid is 6-8% of the total mass of red mud and cement in the mixed slurry. In a specific embodiment, it can be 6%, 7% or 8%.

[0049] In the present invention, the mixing is preferably performed under stirring conditions.

[0050] After obtaining the foam slurry, the present invention cures the foam slurry and then crushes and granulates the foam slurry to obtain artificial soil particles.

[0051] In the present invention, the curing is preferably natural curing; the time of the natural curing is preferably 14 to 28 days, and in a specific embodiment, it can be 14 days, 16 days, 20 days, 24 days or 28 days. In the present invention, it is preferred to first perform natural curing in the mold for 1 to 2 days, and then remove the mold to continue natural curing. In the present invention, the function of the curing is to accelerate the hardening of the soil so that it reaches the designed strength.

[0052] The present invention has no special requirements for the crushing and granulation, as long as the mass proportion of the particles with a particle size of 0.05-4 mm in the artificial soil particles exceeds 60%; more preferably, the mass proportion of the particles with a particle size of less than 0.05 mm in the artificial soil particles is 5-10%, the mass proportion of the particles with a particle size of 0.05-4 mm is 65-80%, and the mass proportion of the particles with a particle size of >4 mm is 15-30%.

[0053] The mass of particles with a diameter of 0.05-0.1 mm accounts for 10-15%, the mass of particles with a diameter of 0.1-2 mm accounts for 55-65%, and the mass of particles with a diameter of 2-4 mm accounts for 35-20%.

[0054] After obtaining the artificial soil particles, the present invention soaks the artificial soil particles in a phosphoric acid solution and filters the solution to obtain modified artificial soil particles.

[0055] In the present invention, the mass concentration of the phosphoric acid solution is preferably 1-5%. In a specific embodiment, the mass concentration of the phosphoric acid solution can be 1%, 2%, 3%, 4% or 5%. In the present invention, the number of immersions is preferably 3-5 times, and the time of each immersion is independently preferably 4-6 hours. In the present invention, the phosphoric acid solution is preferably replaced after each immersion. The present invention has no special requirements for the amount of phosphorus solution used for each immersion, as long as the artificial soil particles can be immersed. The present invention reduces the alkalinity of red mud by immersing it in phosphoric acid solution, making it suitable for plant growth. In the present invention, after the filtration, it is preferred to further include naturally drying the obtained modified artificial soil particles.

[0056] After obtaining the modified artificial soil particles, the present invention mixes the modified artificial soil particles with organic matter to obtain artificial planting soil.

[0057] In the present invention, the organic matter can provide the nutrients required for plant growth. The present invention has no special requirements for the specific type of the organic matter, and any organic matter familiar to those skilled in the art can be used. For example, it can be animal fermented fertilizer or plant humus, and those skilled in the art can add it according to the growth habits of plants. In the present invention, the amount of organic matter added is preferably 15-20% of the artificial planting soil; in a specific embodiment, the amount of organic matter added can be 15%, 16%, 17%, 18%, 19% or 20% of the artificial planting soil.

[0058] The present invention provides artificial planting soil prepared by the above scheme.

[0059] The artificial planting soil has good water absorption, water retention and air permeability and is suitable for plant growth.

[0060] The present invention provides the use of the artificial planting soil described in the above scheme in plant planting.

[0061] In the present invention, the plant preferably includes Pilea spathulata, Magnoliopsis truncatula or Strelitzia ovata.

[0062] The artificial planting soil provided by the present invention, the method for preparing the artificial planting soil using red mud, and the application of the artificial planting soil are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0063] The composition of the soil structure restoration agent used in the following examples is as follows:

[0064] Surfactant 0.2wt%, foam stabilizer 0.1wt%, enhancer 0.1wt%, balance water;

[0065] The surfactant is alkyl polyglycoside, the foam stabilizer is nano silicon dioxide, and the enhancer is methyl cellulose.

[0066] Example 1

[0067] The dried and ground red mud with a particle size of less than 1 mm and PO42.5 cement were mixed and stirred in a stirring pot at a mass ratio of 7:3, and then the corresponding weight of water was added at a water-solid ratio of 0.5 and stirred evenly. The soil structure restoration agent (the mass of the soil structure restoration agent was 6% of the total mass of the red mud and cement) was foamed by a foaming machine and then injected into the stirring pot. After stirring evenly and stably, the foam slurry was poured into a mold, and crushed after natural curing for 28 days to obtain artificial soil particles with a particle size of 0.05-4 mm accounting for more than 60% (specific particle size distribution is shown in Table 1), and then the artificial soil particles were immersed in a phosphoric acid solution with a mass concentration of 5%, and the phosphoric acid solution was replaced every 6 hours. The soaking was repeated 3 times, filtered out, and dried naturally to obtain modified artificial soil particles; 20% of plant humus and 80% of the modified artificial soil particles were mixed evenly to make red mud artificial planting soil, and a total of 3 soil samples were prepared.

[0068] The 28-day strength of the red mud artificial soil block before crushing in Example 1 is about 5 MPa, and the particle size distribution of the red mud artificial soil particles obtained by crushing is shown in Table 1 below, which meets the requirements of the specification (General Technical Standard for Three-Dimensional Greening Cultivation Substrates T / CABEE 005-2020).

[0069] Table 1 Particle size distribution of red mud artificial planting soil

[0070] <0.05mm 0.05-4mm >4mm Specification requirements ≤15％ ≥35％ ≤50％ Particle size distribution 5％ 75％ 20％

[0071] The indicators of the obtained artificial soil particles are shown in Table 2 below, which meet the physical and chemical indicators of roof greening cultivation substrates in the specification (General Technical Standard for Three-Dimensional Greening Cultivation Substrates T / CABEE 005-2020) and are suitable for plant growth.

[0072] Table 2 Physical and chemical indicators of artificial red mud planting soil

[0073]

[0074]

[0075] Plant growth conditions are shown in Table 3 and Figure 1 shown.

[0076] Table 3 Growth of plants planted in artificial red mud planting soil

[0077] Plant species Survival rate (%) Seed germination index (%) Growth potential Pilea 100 86 Good growth Goldfish Flower 100 90 Good growth Elymus dahliae 98 83 Good growth

[0078] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing artificial planting soil using red mud, characterized in that: The following steps are involved: mixing red mud, cement and water to obtain a mixed slurry; Physically foaming the soil structure restoration agent to form prefabricated foam to obtain a foamy soil structure restoration liquid; The foamed soil structure recovery liquid is mixed with the mixed slurry, and the obtained foamed slurry is cured and then crushed and granulated to obtain artificial soil particles; soaking the artificial soil particles in a phosphoric acid solution, filtering, and obtaining modified artificial soil particles; The modified artificial soil particles are mixed with organic matter to obtain artificial planting soil.

2. The method according to claim 1, characterized in that The mass of the red mud is 20-30% of the total mass of the red mud and cement.

3. The method according to claim 1 or 2, characterized in that: The water-to-solid mass ratio in the mixed slurry is 0.5-0.6:

1.

4. The method according to claim 1, characterized in that: Taking the total weight of the soil structure restoration agent as 100%, the soil structure restoration agent comprises the following components in percentage by weight: 0.1-1 wt% surfactant, 0.1-1 wt% foam stabilizer, 0.05-1 wt% enhancer, and the balance water; The foam stabilizer comprises one or more of nano kaolin, nano bentonite, nano silicon dioxide, nano attapulgite and nano montmorillonite; The reinforcing agent includes cellulose and / or cellulose derivatives.

5. The method according to claim 1 or 4, characterized in that: The mass of the soil structure restoration agent in the foamy soil structure restoration liquid is 6-8% of the total mass of the red mud and cement in the mixed slurry.

6. The method according to claim 1, characterized in that The mass concentration of the phosphoric acid solution is 1-5%, the number of immersions is 3-5 times, and the duration of each immersion is independently 4-6 hours.

7. The method according to claim 1, characterized in that The mass content of organic matter in the artificial planting soil is 15-20%.

8. The method according to claim 1, characterized in that: The curing is natural curing, and the time of the natural curing is 14 to 28 days.

9. The artificial planting soil prepared by the method according to any one of claims 1 to 8.

10. Use of the artificial planting soil according to claim 9 in plant planting.

Images