Modified aluminum red mud material and application thereof

Abstract

The application discloses a modified aluminum red mud material and application thereof, and belongs to the field of metallurgical solid waste recycling. The material preparation steps are as follows: aluminum red mud is dried and crushed, a complex modifier is sprayed to obtain an intermediate, a neutralization solidification liquid is added for neutralization treatment, and the modified aluminum red mud material is obtained after natural ventilation; the complex modifier is prepared by ammination and modification of a copolymer base liquid with a polybasic carboxylic acid; the neutralization solidification liquid is prepared by double-acid activation, sodium aluminosilicate reaction and chelation dispersion; and the two cooperate to realize alkaline neutralization and deep heavy metal solidification. The preparation process of the application is carried out at normal temperature, reagents are uniformly contacted through a nano spray gun, the pH of the modified material is stably weak alkaline, the heavy metal leaching amount is lower than the hazardous waste standard, the hazardous solid waste is converted into general industrial solid waste, the material can be used as a road subgrade, a building material and a fly ash substitute, the process has strong universality, is suitable for industrialization popularization, and has environmental protection and resource utilization values.

Description

Technical Field

[0001] This invention relates to the field of metallurgical solid waste recycling, specifically to a modified aluminum red mud material and its application. Background Technology

[0002] Aluminum red mud is a highly alkaline industrial solid waste generated during alumina production. It typically contains a large amount of residual alkali and various heavy metal components. Due to its high water content (28%-40%), strong alkalinity, and high viscosity, its long-term storage and disposal in block form not only occupies a large amount of land resources but also poses serious environmental risks such as soil alkalization and heavy metal pollution of groundwater.

[0003] Currently, the main technologies for treating aluminum red mud include acid neutralization, salting out, and high-temperature roasting. However, existing methods generally suffer from high treatment costs, high energy consumption, and significant risks of secondary pollution. For example, traditional wet neutralization requires a large amount of acidic reagents and easily generates saline wastewater; while high-temperature roasting can solidify heavy metals to some extent, it is energy-intensive and requires significant equipment investment, making large-scale industrial application difficult. Furthermore, conventional modification processes often result in uneven absorption of modifiers and incomplete reactions due to the high moisture content and uneven particle size of aluminum red mud, leading to unstable product performance that fails to meet the application requirements of building materials, soil remediation, and other fields.

[0004] Therefore, there is an urgent need to develop a modified aluminum red mud material and its applications. Summary of the Invention

[0005] To address the problems mentioned in the background section, this invention provides a modified aluminum red mud material and its applications.

[0006] In a first aspect, the present invention provides a modified aluminum red mud material, which is prepared by the following method:

[0007] Step S1: Dry the aluminum red mud to obtain dried aluminum red mud;

[0008] Step S2: The dried aluminum red mud is pulverized to obtain pulverized aluminum red mud;

[0009] Step S3: Spray a complexing modifier onto the pulverized aluminum red mud to obtain a modified aluminum red mud intermediate;

[0010] Step S4: Spray neutralizing and curing liquid onto the modified aluminum red mud intermediate for neutralization treatment. After natural ventilation, the modified aluminum red mud material is obtained.

[0011] Furthermore, the drying process in step S1 is as follows: the blocky aluminum red mud is dried to a moisture content of 8%-10%.

[0012] Furthermore, the pulverization process in step S2 is as follows: the dried aluminum red mud is pulverized to a particle size of 80-120 mesh.

[0013] Furthermore, in step S3, the spraying is performed using a nano-scale spray gun;

[0014] Furthermore, in step S3, the amount of complexing modifier used is 8%-12% of the mass of the pulverized aluminum red mud.

[0015] Furthermore, in step S4, the specific conditions for the neutralization process are as follows:

[0016] The neutralizing and curing liquid is sprayed using a nano-level spray gun while being stirred. The stirring speed is 60 rpm to 120 rpm and the stirring time is 20 min to 40 min.

[0017] Furthermore, in step S4, the amount of neutralizing and curing liquid sprayed is 8%-15% of the mass of the modified aluminum red mud intermediate.

[0018] Furthermore, in step S4, natural ventilation is carried out for 24-48 hours to reduce the moisture content to below 5%.

[0019] Furthermore, the preparation method of the complexing modifier is as follows:

[0020] Step A1: Heat deionized water to 45℃-55℃, add maleic anhydride, acrylamide and ammonium persulfate, and stir the reaction under nitrogen protection for 2h-3h to obtain copolymer base liquid;

[0021] Step A2: Add tetraethylenepentamine and triethanolamine to the copolymer base solution, adjust the pH to 8.0-9.0, heat to 65℃-75℃, and react for 1.5h-2.5h to obtain the complex intermediate;

[0022] Step A3: Cool the complexation intermediate to 40-50℃, add dropwise an aqueous solution containing sodium citrate and sodium gluconate, add solid acid, stir at a constant temperature for 30-60 minutes, and after cooling, obtain the complexation modifier.

[0023] Furthermore, in the preparation process of the complexing modifier, the specific components by weight are as follows: maleic anhydride 18-22 parts, acrylamide 12-16 parts, ammonium persulfate 0.4-0.6 parts, tetraethylenepentamine 9-11 parts, triethanolamine 6-8 parts, an aqueous solution containing sodium citrate and sodium gluconate 16.5-20.5 parts, solid acid 1-2 parts, and deionized water 160-210 parts.

[0024] Furthermore, the aqueous solution containing sodium citrate and sodium gluconate is composed of the following components by weight: 4-5 parts sodium citrate, 2.5-3.5 parts sodium gluconate, and 10-12 parts deionized water.

[0025] Furthermore, the solid acid is selected from any one of tartaric acid, oxalic acid, and boric acid.

[0026] Furthermore, the preparation method of the neutralizing and curing liquid is as follows:

[0027] Step B1: Add deionized water to the reaction vessel, heat to 40-45℃, add phosphoric acid, stir for 5-8 minutes, then add oxalic acid and stir until completely dissolved to obtain acidic mixture A;

[0028] Step B2: Maintain 40℃-45℃, add sodium aluminosilicate to mixture A while stirring, and continue stirring for 40min-60min after the addition is complete to obtain mixture B;

[0029] Step B3: Cool the mixture B to 25℃-30℃, add sodium bisulfate, and stir until completely dissolved; then add lignin sulfonate and stir for 20min-30min to obtain mixture C;

[0030] Step B4: Add disodium ethylenediaminetetraacetate to mixture C, stir until completely dissolved, let stand for 0.5-1 hour to mature, filter, and obtain neutralized and cured solution.

[0031] Furthermore, in the preparation process of the neutralization and curing liquid, the specific components of each material by weight are as follows: 80-120 parts deionized water, 5-10 parts phosphoric acid, 3-6 parts oxalic acid, 10-18 parts sodium aluminosilicate, 3-6 parts sodium bisulfate, 4-8 parts lignin sulfonate, and 1-3 parts disodium ethylenediaminetetraacetate.

[0032] Secondly, the present invention provides an application of modified alumina red mud material in roadbed materials, building materials, or fly ash substitutes.

[0033] The beneficial effects of this invention are:

[0034] This invention solves the problems of incomplete alkaline neutralization and poor heavy metal curing in existing aluminum red mud modification processes by employing a synergistic system of complexing modifier and neutralizing curing liquid. The complexing modifier is prepared by amination modification and polycarboxylic acid complexation modification of copolymer base liquid, which can form a complex layer on the surface of aluminum red mud particles to achieve in-situ capture of heavy metals. Combined with the synergistic activation of dual acids and the strong chelation of EDTA in the neutralizing curing liquid, deep curing of heavy metals is achieved. At the same time, the acidic system of the neutralizing curing liquid precisely neutralizes the strong alkalinity of aluminum red mud, so that the pH of the modified material is stable in the weakly alkaline range. This overcomes the shortcomings of traditional acid neutralization methods, which can only reduce alkali and are prone to over-neutralization or incomplete neutralization, and effectively avoids the environmental risks of soil alkalization and secondary leaching of heavy metals.

[0035] The modification process employed in this invention is carried out entirely at room temperature, and the complexing modifier and neutralizing curing liquid are uniformly sprayed using a nano-scale spray gun. This solves the problems of high energy consumption and large equipment investment in existing high-temperature calcination modification processes, as well as the uneven absorption and incomplete reaction of modifiers caused by uneven material mixing in conventional wet modification processes. The pulverized aluminum red mud has a uniform particle size, which can fully adsorb the complexing modifier. Combined with the process of spraying and stirring simultaneously, the complexing modifier, neutralizing curing liquid, and aluminum red mud particles are fully contacted and react completely. This ensures the stability of the modified product's performance, significantly reduces production energy consumption and process costs, and eliminates the need for large amounts of acidic reagents, avoiding the secondary pollution problem of saline wastewater generated by traditional wet neutralization. This makes it more suitable for large-scale industrial applications.

[0036] The modified aluminum red mud material prepared by this invention not only realizes the transformation of aluminum red mud from highly alkaline hazardous solid waste to general industrial solid waste, but also solves the problems of limited application scenarios and low resource utilization rate of existing modified red mud products. The modified material has lower corrosivity and heavy metal leaching toxicity than the national hazardous waste identification standards, and forms a stable granular structure, which can be directly used as roadbed material, building material or fly ash substitute, realizing the high-value resource utilization of aluminum red mud. At the same time, the modification process adopted by this invention has strong versatility and can provide feasible solutions for the harmless and resource-based treatment of various industrial solid wastes and soil-like solid wastes, effectively alleviating the land occupation and environmental pollution problems caused by solid waste stockpiling, and meeting the industrial development needs of resource recycling. Detailed Implementation

[0037] To make the embodiments of the present invention easier to understand, the present invention will be described in detail below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not limited to the application scope of the present invention.

[0038] The nano-level spray gun used in this invention is a T-AGPZ spray gun, brand name Devilbiss, part number T-AGPZ-S9-Z1-1.0-TCH, purchased from Naco Coating Equipment (Suzhou) Co., Ltd.

[0039] Example 1

[0040] A method for preparing modified aluminum red mud material, comprising the following steps:

[0041] The preparation method of the complexing modifier is as follows:

[0042] By weight, take 18 parts maleic anhydride, 12 parts acrylamide, 0.4 parts ammonium persulfate, 9 parts tetraethylenepentamine, 6 parts triethanolamine, 16.5 parts an aqueous solution containing sodium citrate and sodium gluconate, 1 part tartaric acid, and 160 parts deionized water; wherein, the aqueous solution containing sodium citrate and sodium gluconate consists of 4 parts sodium citrate, 2.5 parts sodium gluconate, and 10 parts deionized water by weight.

[0043] Step A1: Heat deionized water to 45°C, add maleic anhydride, acrylamide and ammonium persulfate, and stir the reaction under nitrogen protection for 2 hours to obtain copolymer base liquid;

[0044] Step A2: Add tetraethylenepentamine and triethanolamine to the copolymer base solution, adjust the pH to 8.0, heat to 65°C, and react for 1.5 h to obtain the complex intermediate;

[0045] Step A3: Cool the complexation intermediate to 40°C, and add an aqueous solution containing sodium citrate and sodium gluconate dropwise while stirring. Control the dropwise addition time to be completed within 20 minutes, and control the stirring speed to 100 rpm during the dropwise addition. After the dropwise addition is completed, add tartaric acid and stir at a constant temperature for 30 minutes. Then cool naturally to room temperature to obtain the complexation modifier.

[0046] The preparation method of the neutralizing and curing liquid is as follows:

[0047] By weight, take 80 parts deionized water, 5 parts phosphoric acid, 3 parts oxalic acid, 10 parts sodium aluminosilicate, 3 parts sodium bisulfate, 4 parts lignin sulfonate, and 1 part disodium ethylenediaminetetraacetate.

[0048] Step B1: Add deionized water to the reaction vessel, heat to 40°C, add phosphoric acid, stir for 5 minutes, then add oxalic acid, stir for 5 minutes until completely dissolved, to obtain acidic mixture A;

[0049] Step B2: Keep the temperature at 40°C, add sodium aluminosilicate to mixture A while stirring. After adding the sodium aluminosilicate, continue stirring and reacting for 40 minutes to obtain mixture B.

[0050] Step B3: Cool the mixture B to 25°C; add sodium bisulfate and stir for 5 minutes until completely dissolved; then add lignin sulfonate, controlling the addition time to be completed within 5 minutes, and continue stirring for 20 minutes to obtain mixture C;

[0051] Step B4: Add disodium ethylenediaminetetraacetate to mixture C and stir at room temperature for 10 minutes until completely dissolved; then let it stand for 0.5 hours to mature; after maturation, filter with a 200-mesh filter cloth to remove trace amounts of insoluble matter and obtain the neutralized and cured solution.

[0052] Step S1: Take block-shaped aluminum red mud and dry it in an oven at 105℃ until the moisture content is 8% to obtain dried aluminum red mud;

[0053] Step S2: Put the dried aluminum red mud into a vertical mill and grind it to a particle size of 80 mesh to obtain the ground aluminum red mud;

[0054] Step S3: Using a nano-spray gun, the complexing modifier is evenly sprayed onto the pulverized aluminum red mud within 10 minutes; the amount of complexing modifier is 8% of the mass of the pulverized aluminum red mud; the mixture is continuously stirred during the spraying process at a speed of 60 rpm, and stirred for another 10 minutes after the spraying is completed to obtain the modified aluminum red mud intermediate.

[0055] Step S4: Using a nano-level spray gun, the neutralizing and curing liquid is evenly sprayed onto the modified aluminum red mud intermediate within 12 minutes; the amount of neutralizing and curing liquid added is 8% of the mass of the modified aluminum red mud intermediate; during the spraying process, the mixture is stirred at a speed of 60 rpm for 20 minutes; then it is placed in a ventilated place for natural ventilation for 24 hours to reduce its moisture content to 4.9%, thus obtaining the modified aluminum red mud material.

[0056] Example 2

[0057] A method for preparing modified aluminum red mud material, comprising the following steps:

[0058] The preparation method of the complexing modifier is as follows:

[0059] By weight, take 20 parts maleic anhydride, 14 parts acrylamide, 0.5 parts ammonium persulfate, 10 parts tetraethylenepentamine, 7 parts triethanolamine, 18.5 parts an aqueous solution containing sodium citrate and sodium gluconate, 1.5 parts oxalic acid, and 180 parts deionized water; wherein, the aqueous solution containing sodium citrate and sodium gluconate consists of 4.5 parts sodium citrate, 3 parts sodium gluconate, and 11 parts deionized water by weight.

[0060] Step A1: Heat deionized water to 50°C, add maleic anhydride, acrylamide and ammonium persulfate, and stir the reaction under nitrogen protection for 2.5 h to obtain copolymer base liquid;

[0061] Step A2: Add tetraethylenepentamine and triethanolamine to the copolymer base solution, adjust the pH to 8.5, heat to 70℃ and react for 2 hours to obtain the complex intermediate;

[0062] Step A3: Cool the complexation intermediate to 45°C, and add an aqueous solution containing sodium citrate and sodium gluconate dropwise while stirring. Control the dropwise addition time to be completed within 25 minutes, and control the stirring speed at 150 rpm during the dropwise addition. After the dropwise addition is completed, add oxalic acid and stir at a constant temperature for 45 minutes. Then cool naturally to room temperature to obtain the complexation modifier.

[0063] The preparation method of the neutralizing and curing liquid is as follows:

[0064] By weight, take 100 parts deionized water, 7 parts phosphoric acid, 4.5 parts oxalic acid, 15 parts sodium aluminosilicate, 4.5 parts sodium bisulfate, 6 parts lignin sulfonate, and 2 parts disodium ethylenediaminetetraacetate.

[0065] Step B1: Add deionized water to the reaction vessel, heat to 42°C, add phosphoric acid, stir for 6.5 min, then add oxalic acid, stir for 7 min until completely dissolved, to obtain acidic mixture A;

[0066] Step B2: Keep the temperature at 42°C, add sodium aluminosilicate to mixture A while stirring. After adding the sodium aluminosilicate, continue stirring and reacting for 50 minutes to obtain mixture B.

[0067] Step B3: Cool the mixture B to 27°C; add sodium bisulfate and stir for 7 minutes until completely dissolved; then add lignin sulfonate, controlling the addition time to be completed within 7.5 minutes, and continue stirring for 25 minutes to obtain mixture C;

[0068] Step B4: Add disodium ethylenediaminetetraacetate to mixture C and stir at room temperature for 12 minutes until completely dissolved; then let it stand for 0.75 hours to mature; after maturation, filter with a 250-mesh filter cloth to remove trace amounts of insoluble matter and obtain the neutralized and cured solution.

[0069] Step S1: Take block-shaped aluminum red mud and dry it in an oven at 107℃ until the moisture content is 9% to obtain dried aluminum red mud;

[0070] Step S2: Put the dried aluminum red mud into a vertical mill and grind it to a particle size of 100 mesh to obtain the ground aluminum red mud;

[0071] Step S3: Using a nano-spray gun, the complexing modifier is evenly sprayed onto the pulverized aluminum red mud within 12 minutes; the amount of complexing modifier is 10% of the mass of the pulverized aluminum red mud; the mixture is continuously stirred during the spraying process at a speed of 80 rpm, and stirring is continued for 12 minutes after the spraying is completed to obtain the modified aluminum red mud intermediate.

[0072] Step S4: Using a nano-level spray gun, the neutralizing and curing liquid is evenly sprayed onto the modified aluminum red mud intermediate within 15 minutes; the amount of neutralizing and curing liquid added is 12% of the mass of the modified aluminum red mud intermediate; during the spraying process, the mixture is stirred at a speed of 90 rpm for 30 minutes; then it is placed in a ventilated place for natural ventilation for 32 hours to reduce its moisture content to 3.6%, thus obtaining the modified aluminum red mud material.

[0073] Example 3

[0074] A method for preparing modified aluminum red mud material, comprising the following steps:

[0075] The preparation method of the complexing modifier is as follows:

[0076] By weight, take 22 parts maleic anhydride, 16 parts acrylamide, 0.6 parts ammonium persulfate, 11 parts tetraethylenepentamine, 8 parts triethanolamine, 20.5 parts an aqueous solution containing sodium citrate and sodium gluconate, 2 parts tartaric acid, oxalic acid or boric acid, and 210 parts deionized water; wherein, the aqueous solution containing sodium citrate and sodium gluconate consists of 5 parts sodium citrate, 3.5 parts sodium gluconate and 12 parts deionized water by weight.

[0077] Step A1: Heat deionized water to 55°C, add maleic anhydride, acrylamide and ammonium persulfate, and stir the reaction for 3 hours under nitrogen protection to obtain copolymer base liquid;

[0078] Step A2: Add tetraethylenepentamine and triethanolamine to the copolymer base solution, adjust the pH to 9.0, and heat to 75°C for 2.5 h to obtain the complex intermediate;

[0079] Step A3: Cool the complexation intermediate to 50°C, and add an aqueous solution containing sodium citrate and sodium gluconate dropwise while stirring. Control the dropwise addition time to be completed within 30 minutes, and control the stirring speed to 200 rpm during the dropwise addition. After the dropwise addition is completed, add oxalic acid and stir at a constant temperature for 60 minutes. Then cool naturally to room temperature to obtain the complexation modifier.

[0080] The preparation method of the neutralizing and curing liquid is as follows:

[0081] By weight, take 120 parts of deionized water, 10 parts of phosphoric acid, 6 parts of oxalic acid, 18 parts of sodium aluminosilicate, 6 parts of sodium bisulfate, 8 parts of lignin sulfonate, and 3 parts of disodium ethylenediaminetetraacetate.

[0082] Step B1: Add deionized water to the reaction vessel, heat to 45°C, add phosphoric acid, stir for 8 minutes, then add oxalic acid, stir for 10 minutes until completely dissolved, to obtain acidic mixture A;

[0083] Step B2: Keep at 45℃, add sodium aluminosilicate to mixture A while stirring. After the addition is complete, continue stirring and react for 60 minutes to obtain mixture B.

[0084] Step B3: Cool the mixture B to 30°C; add sodium bisulfate and stir for 10 minutes until completely dissolved; then add lignin sulfonate, controlling the addition time to be completed within 10 minutes, and continue stirring for 30 minutes to obtain mixture C;

[0085] Step B4: Add disodium ethylenediaminetetraacetate to mixture C and stir at room temperature for 15 minutes until completely dissolved; then let it stand and mature for 1 hour; after maturation, filter with a 300-mesh filter cloth to remove trace amounts of insoluble matter and obtain the neutralized and cured solution.

[0086] Step S1: Take block-shaped aluminum red mud and dry it in an oven at 110℃ until the moisture content is 10% to obtain dried aluminum red mud;

[0087] Step S2: Put the dried aluminum red mud into a vertical mill and grind it to a particle size of 120 mesh to obtain the ground aluminum red mud;

[0088] Step S3: Using a nano-spray gun, the complexing modifier is evenly sprayed onto the pulverized aluminum red mud within 15 minutes; the amount of complexing modifier is 12% of the mass of the pulverized aluminum red mud; the mixture is continuously stirred during the spraying process at a speed of 100 rpm, and stirred for another 15 minutes after the spraying is completed to obtain the modified aluminum red mud intermediate.

[0089] Step S4: Using a nano-level spray gun, the neutralization and curing liquid is evenly sprayed onto the modified aluminum red mud intermediate within 20 minutes; the amount of neutralization and curing liquid added is 15% of the mass of the modified aluminum red mud intermediate; during the spraying process, the mixture is stirred at a speed of 120 rpm for 40 minutes; then it is placed in a ventilated place for natural ventilation for 48 hours to reduce its moisture content to below 2.1%, thus obtaining the modified aluminum red mud material.

[0090] Comparative Example 1

[0091] Compared with Example 1, in step S3, the "complexing modifier" was replaced with an equal mass of "complexing intermediate". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, the modified aluminum red mud material was obtained.

[0092] Comparative Example 2

[0093] Compared with Example 1, in step S3, the "complexing modifier" was replaced with an equal mass of "copolymer base liquid". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, the modified aluminum red mud material was obtained.

[0094] Comparative Example 3

[0095] Compared with Example 1, in step S4, the "neutralizing curing liquid" was replaced with an equal mass of "mixed liquid C". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, the modified aluminum red mud material was obtained.

[0096] Comparative Example 4

[0097] Compared with Example 1, in step S4, the "neutralizing curing liquid" was replaced with an equal mass of "mixed liquid B". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, the modified aluminum red mud material was obtained.

[0098] Comparative Example 5

[0099] Compared with Example 1, in step S4, the "neutralizing curing liquid" was replaced with an equal mass of "mixed liquid A". All other steps and parameters are the same. This comparative example will not be repeated. Finally, the modified aluminum red mud material was obtained.

[0100] Performance testing

[0101] The modified aluminum red mud materials prepared in Examples 1-3 and Comparative Examples 1-5 were subjected to performance testing, and the results are recorded in Table 1.

[0102] Testing methods for modified aluminum red mud materials:

[0103] 1. Leachate preparation method

[0104] The sample leachate was prepared according to the "Solid Waste Leaching Toxicity Leaching Method - Sulfuric Acid and Nitric Acid Method" (HJ / T 299-2007). The modified aluminum red mud sample was accurately weighed and placed in a 2L extraction bottle. A sulfuric acid and nitric acid extraction solvent (concentrated sulfuric acid to concentrated nitric acid mass ratio 2:1) with a liquid-to-solid ratio of 10:1 (L / kg) was added, with a pH of 3.20±0.05. The extraction bottle was fixed on a shaking device and shaken at 30±2 r / min for 18h±2h. After shaking, the sample was allowed to stand for 15 min, filtered through medium-speed quantitative filter paper, and the leachate was collected for subsequent analysis.

[0105] 2. pH Measurement Method

[0106] The pH value of the leachate was determined according to the standard "Determination of Corrosivity of Solid Waste by Glass Electrode Method" (GB / T 15555.12-1995).

[0107] 3. Method for determining hexavalent chromium

[0108] The content of hexavalent chromium in the leachate was determined according to the standard "Determination of Hexavalent Chromium in Solid Waste by Diphenylcarbazide Spectrophotometric Method" (GB / T 15555.4-1995).

[0109] 4. Methods for determining heavy metal elements (lead, cadmium, total chromium)

[0110] The contents of lead, cadmium, and total chromium in the leachate were determined in accordance with the standard "Determination of 22 Metallic Elements in Solid Waste by Inductively Coupled Plasma Atomic Emission Spectrometry" (HJ 781-2016).

[0111] 5. Methods for determining mercury and arsenic

[0112] The contents of mercury and arsenic in the leachate were determined according to the standard "Determination of Mercury, Arsenic, Selenium, Bismuth and Antimony in Solid Waste by Microwave Digestion Atomic Fluorescence Method" (HJ 702-2014).

[0113] Note: The standard limits are based on Article 3.1 of the "Identification Standard for Hazardous Waste: Corrosivity Identification" (GB 5085.1-2007) and the "Identification Standard for Hazardous Waste: Leaching Toxicity Identification" (GB 5085.3-2007).

[0114] Table 1: Test Results of Modified Alumina Red Mud Materials

[0115]

[0116] Note: ND indicates not detected.

[0117] As shown in Table 1, the modified aluminum red mud materials prepared in Examples 1-3 of this invention exhibit excellent performance in terms of corrosion control and inhibition of heavy metal leaching toxicity. All test indicators are lower than the limits specified in the "Identification Standard for Hazardous Waste", which is significantly better than Comparative Examples 1-5.

[0118] Data from Example 1 and Comparative Example 1 show that in Comparative Example 1, the complexing modifier was replaced with an equal mass of complexing intermediate in step S3. Due to the lack of polycarboxylic acid complexation by sodium citrate and sodium gluconate, and the pH adjustment function of tartaric acid, the in-situ complexing ability of the complexing modifier for heavy metals in aluminum red mud decreased. Detection data showed that the pH value of Comparative Example 1 was significantly higher than that of Example 1, still exhibiting strong alkalinity; simultaneously, the arsenic leaching amount was significantly higher than that of Example 1, the hexavalent chromium leaching amount was close to the standard limit, and heavy metals such as lead and cadmium changed from undetectable to detectable. Overall, the modification effect was significantly inferior to that of Example 1.

[0119] Data from Example 1 and Comparative Example 2 show that in Comparative Example 2, the complexing modifier was replaced with an equal mass of copolymer base liquid in step S3. Due to the lack of amino and hydroxyl functional groups introduced by amination modification, the chelating ability of the copolymer for heavy metals decreased significantly. Test data showed that the pH value of Comparative Example 2 was significantly higher, the arsenic leaching amount was significantly higher than that of Example 1, the hexavalent chromium leaching amount was close to the limit, and the total chromium leaching amount was significantly higher than that of Example 1, confirming the key role of amination modification in enhancing the heavy metal capture ability of the complexing modifier.

[0120] Data from Example 1 and Comparative Example 3 show that in Comparative Example 3, the neutralizing and curing solution was replaced with an equal mass of mixed solution C in step S4. Due to the lack of EDTA's strong chelating effect on heavy metals and the synergistic effect between lignin sulfonate and EDTA, the heavy metal curing effect was significantly deteriorated. Test data showed that the pH value of Comparative Example 3 was significantly increased, the leaching amount of hexavalent chromium exceeded the standard limit, the leaching amount of arsenic was significantly higher than in Example 1, and the levels of lead, cadmium, and total chromium were all significantly increased. The product could no longer meet the safety requirements for general industrial solid waste, fully demonstrating the indispensable role of EDTA in the chelation and curing of heavy metals.

[0121] Data from Example 1 and Comparative Example 4 show that in Comparative Example 4, the neutralizing curing solution was replaced with an equal mass of mixture B in step S4. Due to the lack of dispersion and cross-linking effects of lignin sulfonate, the uniformity of penetration of the neutralizing curing solution into the pulverized aluminum red mud decreased, leading to incomplete local reactions. Test data showed that although the pH value of Comparative Example 4 was slightly higher than that of Example 1, the arsenic leaching amount was significantly higher, and the leaching amounts of hexavalent chromium and total chromium were also significantly increased, confirming the important role of lignin sulfonate in improving the dispersion uniformity and completeness of the curing solution.

[0122] Data from Example 1 and Comparative Example 5 show that in Comparative Example 5, the neutralizing and curing liquid was replaced with an equal mass of mixture A in step S4. This was due to the lack of active Al provided by sodium aluminosilicate. 3+ Due to the dispersion and cross-linking effects of monosilicic acid and silicate ions, as well as the subsequent chelation and curing effects of lignin sulfonate and EDTA, the neutralization and curing solution can only achieve preliminary acid-base neutralization of aluminum red mud, and cannot achieve deep curing of heavy metals and cross-linking nucleation between particles. Test data show that the pH value of Comparative Example 5 is still significantly higher than that of Example 1; at the same time, the leaching amounts of arsenic, hexavalent chromium, and total chromium are all significantly higher than those of Example 1, and heavy metals such as lead and cadmium have changed from undetectable to detectable. This fully demonstrates the necessity of the synergistic effect of the components in the neutralization and curing solution of this invention for achieving precise control of the alkalinity of aluminum red mud and efficient curing of heavy metals.

[0123] In summary, this invention achieves effective neutralization of the alkalinity of aluminum red mud and deep curing of heavy metals through a multi-level design involving amination modification of the complexing modifier, enhancement through complexation with polycarboxylic acids, and synergistic activation of the neutralizing curing liquid by dual acids, dispersion and crosslinking with lignin sulfonate, and chelation curing with EDTA. The treated modified aluminum red mud material has a pH value reduced to the weakly alkaline range, and the heavy metal leaching amount is far below the national standard limit. It is transformed from a strongly alkaline hazardous solid waste into general industrial solid waste, showing broad application prospects in roadbed materials, building materials, and other fields.

[0124] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A modified aluminum red mud material, characterized in that, It is prepared by the following method: Step S1: Dry the aluminum red mud to obtain dried aluminum red mud; Step S2: The dried aluminum red mud is pulverized to obtain pulverized aluminum red mud; Step S3: Spray a complexing modifier onto the pulverized aluminum red mud to obtain a modified aluminum red mud intermediate; Step S4: Spray neutralizing and curing liquid onto the modified aluminum red mud intermediate for neutralization treatment. After natural ventilation, the modified aluminum red mud material is obtained. The preparation method of the complexing modifier is as follows: Step A1: Heat deionized water to 45℃-55℃, add maleic anhydride, acrylamide and ammonium persulfate, and stir the reaction under nitrogen protection for 2h-3h to obtain copolymer base liquid; Step A2: Add tetraethylenepentamine and triethanolamine to the copolymer base solution, adjust the pH to 8.0-9.0, heat to 65℃-75℃, and react for 1.5h-2.5h to obtain the complex intermediate; Step A3: Cool the complexation intermediate to 40-50℃, add dropwise an aqueous solution containing sodium citrate and sodium gluconate, add solid acid, stir at a constant temperature for 30-60 minutes, and after cooling, obtain the complexation modifier; In the preparation process of the complexing modifier, the materials are as follows by weight: maleic anhydride 18-22 parts, acrylamide 12-16 parts, ammonium persulfate 0.4-0.6 parts, tetraethylenepentamine 9-11 parts, triethanolamine 6-8 parts, aqueous solution containing sodium citrate and sodium gluconate 16.5-20.5 parts, solid acid 1-2 parts, and deionized water 160-210 parts; The preparation method of the neutralizing and curing liquid is as follows: Step B1: Add deionized water to the reaction vessel, heat to 40-45℃, add phosphoric acid, stir for 5-8 minutes, then add oxalic acid and stir until completely dissolved to obtain acidic mixture A; Step B2: Maintain 40℃-45℃, add sodium aluminosilicate to mixture A while stirring, and continue stirring for 40min-60min after the addition is complete to obtain mixture B; Step B3: Cool the mixture B to 25℃-30℃, add sodium bisulfate, and stir until completely dissolved; Then add lignin sulfonate and stir for 20-30 minutes to obtain mixture C; Step B4: Add disodium ethylenediaminetetraacetate to mixture C, stir until completely dissolved, let stand for 0.5h-1h, filter, and obtain neutralized and cured solution; In the preparation of the neutralization and curing liquid, the specific materials are as follows by weight: 80-120 parts deionized water, 5-10 parts phosphoric acid, 3-6 parts oxalic acid, 10-18 parts sodium aluminosilicate, 3-6 parts sodium bisulfate, 4-8 parts lignin sulfonate, and 1-3 parts disodium ethylenediaminetetraacetate.

2. The modified alumina red mud material according to claim 1, characterized in that, The aqueous solution containing sodium citrate and sodium gluconate is composed of the following components by weight: 4-5 parts sodium citrate, 2.5-3.5 parts sodium gluconate, and 10-12 parts deionized water.

3. The modified alumina red mud material according to claim 1, characterized in that, The solid acid is selected from any one of tartaric acid, oxalic acid, and boric acid.

4. The modified alumina red mud material according to claim 1, characterized in that, In step S3, the amount of complexing modifier used is 8%-12% of the mass of the pulverized aluminum red mud.

5. The modified alumina red mud material according to claim 1, characterized in that, In step S4, the amount of neutralizing and curing liquid sprayed is 8%-15% of the mass of the modified aluminum red mud intermediate.

6. The application of the modified alumina red mud material according to any one of claims 1-5 in roadbed materials, building materials or fly ash substitutes.

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