A method for preparing an adsorbent using landfill leachate and red mud, and products and applications thereof

Abstract

The application discloses a method for preparing an adsorbent by using landfill leachate and red mud, and comprises the following steps: (1) mixing the landfill leachate and the red mud uniformly to obtain organic mixed red mud, and then performing roasting treatment on the organic mixed red mud to obtain roasting mud; (2) mixing fly ash and the roasting mud uniformly, and then performing grinding to obtain roasting mixed powder mud; (3) mixing the landfill leachate and the roasting mixed powder mud uniformly, performing granulation, and then standing to obtain raw material particles; and (4) performing hydrothermal reaction on the raw material particles, wherein the hydrothermal liquid is the landfill leachate, after the hydrothermal reaction is completed, solid-liquid separation is performed, the particles after the hydrothermal reaction are dried, and the adsorbent is obtained. The application realizes the resource utilization of industrial waste, and the treatment process is simple; by coupling the roasting and the hydrothermal reaction of the mixed landfill leachate and the red mud, the adsorbent with high adsorption performance is prepared, and the highest mercury adsorption capacity and the highest cadmium adsorption capacity can reach 237 mg / g and 188 mg / g respectively.

Description

A method for preparing adsorbents using landfill leachate and red mud, the products thereof, and their applications. Technical Field

[0001] This invention relates to the resource utilization of industrial waste, and more particularly to a method for preparing adsorbents using landfill leachate and red mud, as well as the products and applications thereof. Background Technology

[0002] Landfill leachate, also known as landfill leaching, is wastewater that seeps out during the landfilling process due to the decomposition of organic matter in the waste, rainwater leaching, and groundwater soaking. Organic matter in the waste decomposes under the action of microorganisms, producing a large amount of water. In addition, rainwater and groundwater also mix with the water in the waste through the landfill cover and waste layer, forming leachate. This leachate typically contains large amounts of organic matter, ammonia nitrogen, humic substances, and various microorganisms, characterized by its complex composition and high concentration. The environmental hazards of landfill leachate cannot be ignored. Organic matter and nutrients in the leachate, once released into water bodies, consume dissolved oxygen, leading to water quality deterioration and affecting the survival of aquatic organisms. Once pollutants in the leachate enter the environment, they can cause long-term damage to organisms through the food chain amplification effect. Improperly treated landfill leachate can also pollute soil and groundwater, altering soil structure and properties, affecting crop growth and quality, polluting groundwater, and threatening the safety of drinking water.

[0003] Red mud, a solid waste generated during alumina production, is produced in enormous quantities and is difficult to treat, posing a serious threat to the ecological environment and human health. With the rapid development of the alumina industry, the discharge of red mud has increased year by year. The dumping of red mud not only requires a large amount of land but may also lead to the degradation of land resources. Harmful substances in red mud can easily seep into the soil during dumping, leading to soil alkalization. These harmful substances can also enter water bodies through rainwater runoff and infiltration, causing water pollution. Highly alkaline red mud residue entering water bodies raises the pH value, disrupting the ecological balance of the water. The alkalinity of red mud can also disrupt the normal physiological activities of plant roots, affecting nutrient absorption and leading to stunted plant growth or even death.

[0004] Resource recovery and high-value utilization of industrial waste are essential for solving resource constraints and achieving sustainable development. However, existing waste treatment processes are costly and prone to secondary pollution. Therefore, developing efficient, economical, and environmentally friendly landfill leachate treatment technologies is crucial for protecting the ecological environment and human health. Red mud is difficult to remove due to its high concentration of chemical alkalis, fluorine, aluminum, and other impurities, making its harmless utilization challenging. Therefore, minimizing the production and harmful effects of red mud and achieving multi-channel, large-scale resource recovery is urgently needed. This will reduce its environmental impact and transform red mud into a valuable resource, enabling its secondary use and comprehensive application in environmental remediation to generate greater value. Summary of the Invention

[0005] Objective of the Invention: To address the above problems, this invention proposes a method for preparing adsorbents using landfill leachate and red mud. Another objective of this invention is to use the prepared adsorbent for the adsorption of heavy metal ions. This achieves the resource utilization of industrial waste, with a simple treatment method, and the prepared adsorbent can achieve highly efficient adsorption of heavy metal ions.

[0006] Technical solution: The present invention provides a method for preparing an adsorbent using landfill leachate and red mud, comprising the following steps:

[0007] (1) Mix the landfill leachate and red mud, stir evenly to obtain organic mixed red mud, and then roast the organic mixed red mud to obtain roasted mud material.

[0008] (2) Mix fly ash and calcining mud, stir evenly, grind into powder, and obtain calcining mixed mud powder.

[0009] (3) Mix the landfill leachate and the roasted mixed mud, stir evenly, granulate, and let stand to obtain raw material granules;

[0010] (4) Place the raw material granules in a water bath for hydrothermal reaction. The hydrothermal liquid is landfill leachate. After the hydrothermal reaction is completed, the solid and liquid are separated. The granules obtained after hydrothermal reaction are dried to obtain the adsorbent.

[0011] Furthermore, in step (1), the calcination temperature is 325–950℃, preferably 400–800℃, the adsorption capacity of the adsorbent for cadmium is higher than 174 mg / g, and the adsorption capacity for mercury is higher than 221 mg / g; the calcination time is 0.5–5.5 hours.

[0012] Furthermore, the liquid-to-solid ratio of the landfill leachate and red mud in step (1) is 0.3 to 0.6:1 mL / g.

[0013] Furthermore, in step (2), the mass ratio of fly ash to calcined mud is 7.5–60:100, preferably 15–45:100, and the adsorbent adsorption capacity for cadmium is higher than 180 mg / g, and the adsorption capacity for mercury is higher than 230 mg / g.

[0014] Furthermore, in step (3), the liquid-to-solid ratio of the landfill leachate and the roasted mixed sludge is 0.25–0.45:1 mL / g; after granulation, it is left to stand for 6–24 hours.

[0015] Furthermore, in step (4), the temperature of the hydrothermal reaction is 135-275℃, preferably 150-250℃, the adsorption capacity of the adjuvant for cadmium is higher than 185mg / g, and the adsorption capacity for mercury is higher than 235mg / g; the hydrothermal reaction time is 2-6 hours.

[0016] The present invention also provides an adsorbent prepared by the method and its application in the adsorption of heavy metal ions.

[0017] Reaction Mechanism: When landfill leachate and red mud are mixed, organic pollutants, ammonia nitrogen, and phosphorus pollutants in the leachate are adsorbed into the red mud particles during stirring, promoting the dissolution of some iron, aluminum, magnesium, calcium, and other elements in the red mud. The organic-blended red mud is then roasted. Under high temperature, the organic pollutants in the landfill leachate decompose, producing water vapor, small-molecule organic acids, carbon dioxide, and other substances. The water vapor and small-molecule organic acids further promote the dissolution of iron, magnesium, and aluminosilicates in the red mud. Simultaneously, under high temperature, ammonia nitrogen decomposes, promoting the combination of chloride ions in the landfill leachate with iron, aluminum, magnesium, and other elements in the red mud through charge balance, forming soluble chlorides. Phosphorus pollutants in the landfill leachate decompose upon heating, transforming into inorganic phosphates and combining with iron, magnesium, aluminum, and other elements to form mixed phosphate minerals. When landfill leachate and calcined sludge are mixed, the organic pollutants, ammonia nitrogen, and phosphorus pollutants in the leachate during mixing and granulation can promote hydration and geopolymerization reactions in fly ash and calcined sludge through water reduction, weak acid activation, and hydration enhancement. This process forms an adsorbent aluminosilicate mineral structure, in which organic pollutants, ammonia nitrogen, phosphorus pollutants, and other soluble salts such as iron, aluminum, magnesium, and calcium are adsorbed into the products of hydration and geopolymerization. During the hydrothermal reaction, the aluminosilicate minerals undergo chemical reactions and structural rearrangement, forming a new aluminosilicate vermiculite structure through condensation. The formed aluminosilicate is mixed with phosphate minerals, and simultaneously, organic pollutants, ammonia nitrogen, phosphorus pollutants, and other soluble salts such as iron, aluminum, magnesium, and calcium are adsorbed between the structural layers, thereby changing the charge balance and binding force between the layers and enhancing the adsorption performance of the adsorbent. Simultaneously, during the hydrothermal reaction, some organic pollutants undergo carbon chain breakage, forming small-molecule organic acid anions that are adsorbed into the aluminosilicate vermiculite structure. Some iron, aluminum, and magnesium elements undergo hydrolysis and polymerization reactions to generate polyaluminum ferromagnesia coagulant. This polyaluminum ferromagnesia coagulant is then incorporated into the hydration products, geopolymers, and aluminosilicate vermiculite structure, forming an adsorbent material with high adsorption performance.

[0018] Beneficial effects: Compared with the prior art, the significant advantages of the present invention are: (1) The raw materials required by the present invention are widely available and easy to obtain. Landfill leachate, red mud and fly ash are all industrial wastes, realizing the resource utilization of industrial waste and turning waste into treasure; (2) The present invention realizes the preparation of high adsorption performance adsorbent materials by coupling and mixing landfill leachate and red mud calcination and hydrothermal reaction. The adsorbent formed can achieve a maximum adsorption capacity of 237 mg / g mercury and 188 mg / g cadmium; (3) The present invention has a simple processing process, low processing cost and no secondary pollution. Attached Figure Description

[0019] Figure 1 is a flowchart of the present invention. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] Raw material source and composition description

[0022] Landfill leachate: The landfill leachate used in the experiment was obtained from Zhuji Sanfeng Environmental Energy Co., Ltd. The concentrated landfill leachate of this batch had a COD concentration of 3639 mg / L, a total phosphorus concentration of 294 mg / L, and an ammonia nitrogen concentration of 1062 mg / L.

[0023] Red mud: The red mud was provided by an aluminum company in Zibo, Shandong. The main components tested included: 40.1% Fe2O3, 26.2% Al2O3, 13.5% SiO2, 11.5% Na2O, 6.42% TiO2, 0.546% CaO, 0.326% SO3 and other components (unavoidable impurities and loss on ignition).

[0024] Fly ash: sourced from the Taicang Power Plant of Huaneng International Power Development Corporation, mainly comprising 43.21% SiO2, 27.08% Al2O3, 15.62% Fe2O3, 6.58% CaO, 3.42% TiO2, 1.43% SO3, 1.04% K2O, 0.63% Na2O and other components (unavoidable impurities and loss on ignition).

[0025] Example 1: Effect of calcination temperature on the adsorption performance of the adsorbent

[0026] As shown in Figure 1, landfill leachate and red mud were mixed at a liquid-to-solid ratio of 0.3:1 mL / g and stirred evenly to obtain organic-blended red mud. The organic-blended red mud was then roasted to obtain roasted mud material, with a roasting time of 0.5 hours and roasting temperatures of 325℃, 350℃, 375℃, 400℃, 600℃, 800℃, 850℃, 900℃, and 950℃. Fly ash and roasted mud material were mixed at a mass ratio of 15:100, stirred evenly, and ground into powder to obtain roasted mixed mud powder. Landfill leachate and roasted mixed mud powder were mixed at a liquid-to-solid ratio of 0.25:1 mL / g, stirred evenly, granulated, and allowed to stand for 6 hours to obtain raw material granules. The raw material granules were placed in a water bath for hydrothermal reaction. The hydrothermal liquid was landfill leachate, the hydrothermal temperature was 150℃, and the hydrothermal time was 2 hours. Solid-liquid separation was performed, and the granules obtained after hydrothermal treatment were dried to obtain the adsorbent.

[0027] Adsorption test: The adsorbent and the simulated solution prepared above were mixed at a solid-liquid ratio of 1:1 g / L, stirred at 120 rpm for half an hour, and centrifuged at 5000 rpm for 5 minutes to obtain the supernatant and the separation slurry. The initial concentration of cadmium and mercury in the simulated solution was 500 mg / L and 500 mg / L respectively. The simulated solution was obtained by dissolving 500 mg of cadmium nitrate and 500 mg of mercuric nitrate in 1 L of deionized water.

[0028] Determination of heavy metal ion concentration: The concentrations of cadmium and mercury in the supernatant were determined according to the "Determination of 32 Elements in Water by Inductively Coupled Plasma Atomic Emission Spectrometry" (HJ 776).

[0029] The test results of this embodiment are shown in Table 1.

[0030] Table 1 Effect of calcination temperature on the adsorption performance of the adsorbent

[0031]

[0032] As shown in Table 1, when the roasting temperature is below 400℃ (as shown in Table 1, roasting temperatures = 375℃, 350℃, 325℃, and even lower values ​​not listed in Table 1), the low roasting temperature leads to incomplete reaction of the organic-blended red mud, resulting in a significant decrease in the adsorption capacity of the prepared adsorbent for cadmium and mercury as the roasting temperature decreases. When the roasting temperature is between 400℃ and 800℃ (as shown in Table 1, roasting temperatures = 400℃, 600℃, and 800℃), the organic-blended red mud is roasted, and the organic pollutants in the landfill leachate decompose under high temperature conditions, producing water vapor, small-molecule organic acids, carbon dioxide, and other substances. The generated water vapor and small-molecule organic acids can further promote the dissolution of iron, magnesium, and aluminosilicates in the red mud. Meanwhile, under high-temperature conditions, ammonia nitrogen decomposes thermally, promoting the combination of chloride ions in the landfill leachate with elements such as iron, aluminum, and magnesium in the red mud through charge balance, forming soluble chlorides. Phosphorus pollution in the landfill leachate decomposes thermally, transforming into inorganic phosphates and combining with elements such as iron, magnesium, and aluminum to form mixed phosphate minerals. Ultimately, the prepared adsorbents exhibited adsorption capacities for cadmium exceeding 174 mg / g and for mercury exceeding 221 mg / g. When the calcination temperature exceeds 800℃ (as shown in Table 1, calcination temperatures = 850℃, 900℃, 950℃, and higher values ​​not listed in Table 1), the excessively high calcination temperature leads to over-burning and coking of the material, causing a significant decrease in the adsorption capacities for cadmium and mercury of the prepared adsorbents with further increases in calcination temperature.

[0033] Therefore, considering both benefits and costs, a calcination temperature of 400–800℃ is most conducive to improving the adsorption performance of the prepared adsorbent. Furthermore, it should be noted that while the prepared adsorbent can already achieve high adsorption of cadmium and mercury at calcination temperatures of 325–950℃, thus fulfilling the purpose of this invention, a calcination temperature of 400–800℃ results in a larger adsorption capacity and superior technical performance. Therefore, 400–800℃ is a more optimal temperature range, not the only acceptable range.

[0034] Example 2: Effect of the mass ratio of fly ash to calcined sludge on the adsorption performance of the adsorbent

[0035] Landfill leachate and red mud were mixed at a liquid-to-solid ratio of 0.45:1 mL / g and stirred evenly to obtain organic-blended red mud. The organic-blended red mud was then roasted to obtain roasted mud material, with a roasting time of 3 hours and a roasting temperature of 800℃. Fly ash and roasted mud material were mixed at mass ratios of 7.5:100, 10:100, 12.5:100, 15:100, 30:100, 45:100, 50:100, 55:100, and 60:100, stirred evenly, and ground into powder to obtain roasted mixed powder mud. Landfill leachate and roasted mixed powder mud were mixed at a liquid-to-solid ratio of 0.35:1 mL / g, stirred evenly, granulated, and allowed to stand for 15 hours to obtain raw material pellets. Raw material pellets are placed in a water bath for hydrothermal reaction. The hydrothermal solution is landfill leachate. The hydrothermal temperature is 200℃ and the hydrothermal time is 4 hours. Solid-liquid separation is performed, and the pellets obtained after hydrothermal treatment are dried to obtain the adsorbent.

[0036] The adsorption test and the determination of heavy metal ion concentration were the same as in Example 1. The test results of this example are shown in Table 2.

[0037] Table 2. Effect of the mass ratio of fly ash and calcined sludge on the adsorption performance of the adsorbent.

[0038]

[0039] As shown in Table 2, when the mass ratio of fly ash to calcined clay is less than 15:100 (as shown in Table 2, when the mass ratio of fly ash to calcined clay is 12.5:100, 10:100, 7.5:100, and even lower ratios not listed in Table 2), less fly ash is added, the amount of aluminosilicate incorporated is reduced, and the efficiency of hydration and geopolymerization reactions decreases. As a result, the adsorption capacity of the prepared adsorbent for cadmium and mercury decreases significantly as the mass ratio of fly ash to calcined clay decreases. When the mass ratio of fly ash to calcined sludge is 15–45:100 (as shown in Table 2, where the mass ratios are 15:100, 30:100, and 45:100), the organic pollutants, ammonia nitrogen, and phosphorus pollutants in the landfill leachate during mixing and granulation can promote hydration and geopolymerization reactions in the fly ash and calcined sludge through water reduction, weak acid activation, and hydration enhancement. This results in the formation of an adsorbent aluminosilicate mineral structure, where organic pollutants, ammonia nitrogen, phosphorus pollutants, and other soluble salts such as iron, aluminum, magnesium, and calcium are adsorbed into the hydration and geopolymerization products. Ultimately, the prepared adsorbents exhibit adsorption capacities exceeding 180 mg / g for cadmium and exceeding 230 mg / g for mercury. When the mass ratio of fly ash to calcined clay is higher than 45:100 (as shown in Table 2, when the mass ratio of fly ash to calcined clay is 50:100, 55:100, 60:100, and higher ratios not listed in Table 2), excessive addition of fly ash and excessive incorporation of aluminosilicates lead to the rapid formation of the aluminosilicate vermiculite structure. Consequently, the adsorption capacity of the prepared adsorbent for cadmium and mercury decreases significantly with further increases in the mass ratio of fly ash to calcined clay.

[0040] Therefore, considering both benefits and costs, a fly ash to calcined sludge mass ratio of 15–45:100 is most advantageous for improving the adsorption performance of the prepared adsorbent. It should also be noted that while a fly ash to calcined sludge mass ratio of 7.5–60:100 already achieves high adsorption capacity for cadmium and mercury, thus fulfilling the purpose of this invention, a mass ratio of 15–45:100 results in a larger adsorption capacity and superior technical performance. Therefore, 15–45:100 is a more optimal mass ratio range, not the only acceptable range.

[0041] Example 3: Effect of hydrothermal temperature on the adsorption performance of the adsorbent

[0042] Landfill leachate and red mud were mixed at a liquid-to-solid ratio of 0.6:1 mL / g and stirred evenly to obtain organic-blended red mud. The organic-blended red mud was then roasted to obtain roasted mud material, with a roasting time of 5.5 hours and a roasting temperature of 800℃. Fly ash and roasted mud material were mixed at a mass ratio of 45:100, stirred evenly, and ground into powder to obtain roasted mixed mud powder. Landfill leachate and roasted mixed mud powder were mixed at a liquid-to-solid ratio of 0.45:1 mL / g, stirred evenly, granulated, and allowed to stand for 24 hours to obtain raw material granules. The raw material granules were placed in a water bath for hydrothermal reaction. The hydrothermal liquid was landfill leachate, and the hydrothermal temperatures were 135℃, 140℃, 145℃, 150℃, 200℃, 250℃, 260℃, 270℃, and 275℃, with a hydrothermal time of 6 hours. Solid-liquid separation was performed, and the granules obtained after hydrothermal treatment were dried to obtain the adsorbent.

[0043] The adsorption test and the determination of heavy metal ion concentration were the same as in Example 1. The test results of this example are shown in Table 3.

[0044] Table 3 Effect of hydrothermal temperature on the adsorption performance of the adsorbent

[0045]

[0046] As shown in Table 3, when the hydrothermal temperature is below 150℃ (e.g., 145℃, 140℃, 135℃, and lower values ​​not listed in Table 3), the low hydrothermal temperature leads to insufficient reaction between fly ash, calcined sludge, and landfill leachate, resulting in a significant decrease in the adsorption capacity of the prepared adsorbent for cadmium and mercury as the hydrothermal temperature decreases. When the hydrothermal temperature is between 150℃ and 250℃ (e.g., 150℃, 200℃, and 250℃ in Table 3), during the hydrothermal reaction, aluminosilicate minerals undergo chemical reactions and structural rearrangement, forming new aluminosilicate vermiculite structures through condensation. The formed aluminosilicate is mixed with phosphate minerals, and simultaneously adsorbs organic pollutants, ammonia nitrogen and phosphorus pollutants, and other soluble salts such as iron, aluminum, magnesium, and calcium between the structural layers, thereby changing the charge balance and binding force between the layers and enhancing the adsorption performance of the adsorbent material. Simultaneously, during the hydrothermal reaction, some organic pollutants undergo carbon chain breakage, forming small-molecule organic acid anions that are adsorbed into the aluminosilicate vermiculite structure. Some iron, aluminum, and magnesium elements undergo hydrolysis and polymerization reactions, generating polyaluminum ferromagnesium chloride (PACMC) coagulant. This PACMC coagulant is mixed with the hydration products, geopolymer products, and the aluminosilicate vermiculite structure, forming an adsorbent material with high adsorption performance. Ultimately, the prepared adsorbents exhibit adsorption capacities for cadmium exceeding 185 mg / g and mercury exceeding 235 mg / g. When the hydrothermal temperature exceeds 250℃ (as shown in Table 3, hydrothermal temperatures = 260℃, 270℃, 275℃, and higher values ​​not listed in Table 3), the excessively high temperature leads to rapid formation of the aluminosilicate vermiculite structure and rapid mineralization and decomposition of organic matter. Consequently, the adsorption capacities for cadmium and mercury in the prepared adsorbents decrease significantly with further increases in hydrothermal temperature.

[0047] Therefore, considering both benefits and costs, a hydrothermal temperature of 150–250°C is most conducive to improving the adsorption performance of the prepared adsorbent. Furthermore, it should be noted that while the prepared adsorbent can already achieve high adsorption of cadmium and mercury at a hydrothermal temperature of 135–275°C, thus fulfilling the purpose of this invention, a hydrothermal temperature of 150–250°C results in a larger adsorption capacity and superior technical performance. Therefore, 150–250°C is a more optimal hydrothermal temperature range, not the only acceptable range.

[0048] The effect of different processes on the adsorption performance of the prepared adsorbent (comparative example)

[0049] The process of this invention is as follows: Landfill leachate and red mud are mixed at a liquid-to-solid ratio of 0.6:1 mL / g and stirred evenly to obtain organically blended red mud. The organically blended red mud is then calcined to obtain calcined mud material, with a calcination time of 5.5 hours and a calcination temperature of 800℃. Fly ash and calcined mud material are mixed at a mass ratio of 45:100, stirred evenly, and ground into powder to obtain calcined mixed powder mud. Landfill leachate and calcined mixed powder mud are mixed at a liquid-to-solid ratio of 0.45:1 mL / g, stirred evenly, granulated, and allowed to stand for 24 hours to obtain raw material granules. The raw material granules are placed in a water bath for hydrothermal reaction. The hydrothermal liquid is landfill leachate, the hydrothermal temperature is 250℃, and the hydrothermal time is 6 hours. Solid-liquid separation is performed, and the granules obtained after hydrothermal treatment are dried to obtain the adsorbent.

[0050] Comparative Process 1 (omitting the step of mixing landfill leachate and red mud): Red mud is roasted to obtain roasted mud material, with a roasting time of 5.5 hours and a roasting temperature of 800℃. Fly ash and roasted mud material are mixed at a mass ratio of 45:100, stirred evenly, and ground into powder to obtain roasted mixed mud powder. Landfill leachate and roasted mixed mud powder are mixed at a liquid-to-solid ratio of 0.45:1mL / g, stirred evenly, granulated, and allowed to stand for 24 hours to obtain raw material granules. The raw material granules are placed in a water bath for hydrothermal reaction. The hydrothermal liquid is landfill leachate, the hydrothermal temperature is 250℃, and the hydrothermal time is 6 hours. Solid-liquid separation is performed, and the granules obtained after hydrothermal treatment are dried to obtain the adsorbent.

[0051] Comparative Process 2 (using pure water as the hydrothermal fluid): Landfill leachate and red mud were mixed at a liquid-to-solid ratio of 0.6:1 mL / g and stirred evenly to obtain organically blended red mud. The organically blended red mud was then roasted to obtain roasted mud material, with a roasting time of 5.5 hours and a roasting temperature of 800℃. Fly ash and roasted mud material were mixed at a mass ratio of 45:100, stirred evenly, and ground into powder to obtain roasted mixed mud powder. Landfill leachate and roasted mixed mud powder were mixed at a liquid-to-solid ratio of 0.45:1 mL / g, stirred evenly, granulated, and allowed to stand for 24 hours to obtain raw material granules. The raw material granules were placed in a water bath for hydrothermal reaction using pure water at a temperature of 250℃ for 6 hours. Solid-liquid separation was performed, and the granules obtained after hydrothermal treatment were dried to obtain the adsorbent.

[0052] The adsorption test and the determination of heavy metal ion concentration were the same as in Example 1. The test results of this example are shown in Table 4.

[0053] Table 4. Effects of different processes on the adsorption performance of the prepared adsorbents.

[0054]

[0055] As shown in Table 4, the adsorbents prepared by the process of the present invention have significantly greater adsorption capacities for cadmium and mercury than those prepared by comparative processes 1 and 2, and are higher than the sum of the two.

Claims

1. A method for preparing an adsorbent using landfill leachate and red mud, characterized in that, Includes the following steps: (1) Mix the landfill leachate and red mud to obtain organic mixed red mud, and then roast the organic mixed red mud to obtain roasted mud material; (2) Mix the fly ash and roasted mud material, grind them to obtain roasted mixed powder mud; (3) Mix the landfill leachate and roasted mixed powder mud, granulate them, and let them stand to obtain raw material particles; (4) Perform a hydrothermal reaction on the raw material particles, the hydrothermal liquid is landfill leachate, after the hydrothermal reaction is completed, the solid and liquid are separated, and the particles obtained after hydrothermal reaction are dried to obtain adsorbent; the COD mass concentration of the landfill leachate is 3639 mg / L, the total phosphorus concentration is 294 mg / L, and the ammonia nitrogen concentration is 1062 mg / L.

2. The method according to claim 1, characterized in that, The roasting temperature in step (1) is 325~950℃.

3. The method according to claim 2, characterized in that, The roasting temperature in step (1) is 400~800℃.

4. The method according to claim 1, characterized in that, The mass ratio of fly ash to calcined mud in step (2) is 7.5~60:

100.

5. The method according to claim 4, characterized in that, The mass ratio of fly ash to calcined mud in step (2) is 15~45:

100.

6. The method according to claim 1, characterized in that, In step (4), the hydrothermal temperature is 135~275℃.

7. The method according to claim 6, characterized in that, In step (4), the hydrothermal temperature is 150~250℃.

8. The method according to claim 1, characterized in that, The liquid-to-solid ratio of landfill leachate and red mud in step (1) is 0.3~0.6:1mL / g, and the liquid-to-solid ratio of landfill leachate and roasted mixed mud powder in step (3) is 0.25~0.45:1mL / g.

9. The adsorbent prepared by the method according to any one of claims 1 to 8.

10. The application of the adsorbent according to claim 9 in the adsorption of heavy metal ions.

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