Biochar-loaded red mud adsorbing material as well as preparation method and application thereof

Abstract

The invention discloses a biochar-loaded red mud adsorbing material and a preparation method and application thereof, and belongs to the technical field of biochar materials, and the biochar adsorbing material loaded with red mud particles is obtained by pyrolyzing peanut shell powder impregnated with red mud. Red mud is loaded on the surface of biochar, the specific surface area and the number of surface functional groups of the adsorption material are increased, the adsorption performance and the adsorption selectivity of the biochar are improved, red mud particles are effectively dispersed through the stable carbon structure of the biochar, the total adsorption sites of the adsorption material are increased, and therefore the strength structure and the adsorption efficiency of the red mud are improved; further, rapid and massive absorption of lead ions is realized, and excellent performance is shown in efficient lead removal in industrial wastewater.

Description

Technical Field

[0001] This invention relates to the field of biochar materials technology, specifically to a biochar-supported red mud adsorbent material, its preparation method, and its application. Background Technology

[0002] Heavy metal pollution generally refers to the introduction of naturally occurring heavy metals from the Earth's crust into the environment by human and natural activities, leading to a surge in heavy metal levels in aquatic and terrestrial environments. Human activities are the primary cause of heavy metal pollution, including the mining and smelting of heavy metal minerals and the discharge of waste gas, wastewater, and solid waste from related chemical industries. Heavy metals are inorganic substances and extremely difficult to degrade by microorganisms, thus easily accumulating in the environment. Once ingested or exposed to the human body, they form stable chemical substances with proteins and enzymes, interfering with normal metabolic activities and endangering human health. Lead, as a harmful metal, can cause harm to the human body even at extremely low concentrations, and lead ions discharged from heavy industrial wastewater can negatively impact aquatic ecosystems. Therefore, developing an efficient, low-cost, and environmentally friendly technology for treating heavy metal pollution is urgently needed.

[0003] Currently, methods for removing heavy metals from wastewater include chemical precipitation, membrane separation, ion exchange, electrodialysis, and phytoremediation. However, each of these methods has its own limitations in application. Compared with other treatment technologies, adsorption has advantages such as simple operation, high adsorption efficiency, and no secondary pollution, making it one of the most widely used methods for removing heavy metals from wastewater.

[0004] Due to its porous structure, large specific surface area, and unique physicochemical properties, biochar is feasible and applicable for treating heavy metal pollution. Studies have found that biochar can effectively adsorb and fix heavy metal ions in wastewater. However, the adsorption-fixation effect of raw biochar is limited by the structure and composition of the raw materials. Faced with complex pollution situations in real-world environments, raw biochar often fails to achieve the expected remediation effect. To improve the applicability and treatment efficiency of biochar, more and more domestic and international experts and scholars are seeking different methods to modify biochar. Currently, the mainstream modification methods include physical modification, chemical modification, and magnetic modification. However, these modification methods require a large amount and variety of external reagents, generate excess waste liquid, easily cause secondary environmental pollution, have cumbersome operation processes, and high manufacturing costs, limiting the practical application of adsorption materials. Therefore, this invention provides a biochar-supported red mud adsorption material, its preparation method, and its application. Summary of the Invention

[0005] This invention provides a biochar-supported red mud adsorbent material, its preparation method, and its application. It effectively solves the technical problems of secondary environmental pollution caused by excess waste liquid generated during existing biochar modification, complex modification process, and high cost, which limit the practical application of adsorbent materials. At the same time, it provides a biochar-supported red mud adsorbent material that can rapidly adsorb large quantities of lead ions from industrial wastewater.

[0006] The first objective of this invention is to provide a method for preparing a biochar-supported red mud adsorbent material, characterized by comprising the following steps:

[0007] Water is added to red mud powder and stirred to obtain a red mud suspension. Fruit shell powder is added to the red mud suspension and stirred at 18-26°C. The mixture is then filtered and dried to obtain pretreated fruit shell powder.

[0008] The pretreated fruit shell powder was pyrolyzed at 600-750°C in a protective atmosphere and then cooled in the furnace to obtain red mud modified biochar.

[0009] In a preferred embodiment, the mass ratio of the red mud powder to the fruit shell powder is 1:1 to 10.

[0010] In a preferred embodiment, the ratio of red mud powder to water is 1g: 50-300mL.

[0011] In a preferred embodiment, the red mud powder is passed through an 18-mesh sieve, and the fruit shell powder is passed through a 10-mesh sieve.

[0012] In one preferred embodiment, the shell includes peanut shells, walnut shells, or melon seed shells.

[0013] In a preferred embodiment, the heating rate is 10°C / min.

[0014] In a preferred embodiment, the pyrolysis time is 2 to 4 hours.

[0015] The second objective of this invention is to provide a biochar-supported red mud adsorbent material prepared by the above-described preparation method.

[0016] The third objective of this invention is to provide an application of the above-mentioned biochar-supported red mud adsorbent material in the removal of heavy metal ions from wastewater, characterized in that the biochar-supported red mud adsorbent material is added to wastewater containing heavy metal ions and adsorbed by shaking at 25°C and 180 rpm for 4 hours.

[0017] In a preferred embodiment, the amount of biochar-supported red mud adsorbent material added is 0.1 g / 35 mL, the pH value of the wastewater containing heavy metal ions is 6, and the concentration of heavy metal ions is 20-200 mg / L.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] (1) The present invention provides a biochar-supported red mud adsorbent material, its preparation method and application. The present invention obtains a biochar-supported red mud particle-based adsorbent material by pyrolyzing peanut shell powder after red mud impregnation. The loading of red mud on the surface of biochar increases the specific surface area and the number of surface functional groups of the adsorbent material, thereby improving the adsorption performance and adsorption selectivity of biochar. The stable carbon structure of biochar effectively disperses the red mud particles, increases the total adsorption sites of the adsorbent material, thereby improving the strength structure and adsorption efficiency of red mud, thus realizing the rapid and large-scale absorption of lead ions, and showing excellent performance in the efficient removal of lead from industrial wastewater.

[0020] (2) The method for modifying red mud biochar provided by the present invention is a mineral adsorbent modification method, which eliminates the use of chemical agents, does not generate excess polluting liquid during the preparation process, and has no environmental by-products; the pre-modification treatment of the material is completed by simple mechanical physical stirring, which greatly simplifies the operation steps and improves the practical applicability of the adsorbent material compared with the traditional modification method; the biochar-supported red mud adsorbent material provided by the present invention adopts the in-situ modification co-pyrolysis method, which, apart from the necessary biomass mass loss during the pyrolysis process, basically does not generate additional biomass loss due to the separation of the material, and belongs to non-destructive modification.

[0021] (3) This invention uses agricultural waste fruit shells and industrial waste red mud as raw materials. The preparation method and operation process are simple, realizing the reuse of waste resources and having high economic, environmental and social benefits. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the preparation process of the biochar-supported red mud adsorbent material of the present invention.

[0023] Figure 2 The graph shows the adsorption capacity and lead ion removal rate of the biochar-supported red mud adsorbent materials prepared in Examples 1-3 of this invention for lead ions in wastewater.

[0024] Figure 3 The graph shows the adsorption capacity and lead ion removal rate of the biochar-supported red mud adsorbent materials prepared in Examples 2, 2 and 3 of this invention for lead ions in wastewater.

[0025] Figure 4 The graph shows the adsorption capacity and lead ion removal rate of lead ions in wastewater by the biochar-supported red mud adsorbent materials prepared in Examples 6-8 and the biochar adsorbent material in Comparative Example 1.

[0026] Figure 5Adsorption isotherms of the biochar-supported red mud adsorbent materials prepared in Examples 6-8 and the biochar adsorbent material in Comparative Example 1 in wastewater with different lead ion concentrations.

[0027] Figure 6 X-ray diffraction analysis diagrams of the biochar-supported red mud adsorbent materials prepared in Examples 6-8 of this invention and the biochar adsorbent material in Comparative Example 1.

[0028] Figure 7 Fourier transform infrared spectra of the biochar-supported red mud adsorbent materials prepared in Examples 6-8 of this invention and the biochar adsorbent material in Comparative Example 1.

[0029] Figure 8 The images shown are scanning electron microscope (SEM) images of the biochar-supported red mud adsorbent materials prepared in Examples 6-8 and the biochar adsorbent material of Comparative Example 1. Image A shows the biochar adsorbent material of Comparative Example 1; Image B shows the biochar-supported red mud adsorbent material of Example 6; Image C shows the biochar-supported red mud adsorbent material of Example 7; and Image D shows the biochar-supported red mud adsorbent material of Example 8. Detailed Implementation

[0030] To enable those skilled in the art to better understand and implement the technical solutions of this invention, the invention will be further described below with reference to specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the invention. Unless otherwise specified, the following test methods and detection methods are conventional methods; unless otherwise specified, the reagents and raw materials are commercially available.

[0031] Example 1

[0032] A method for preparing a biochar-supported red mud adsorbent material includes the following steps:

[0033] S1. Wash the waste peanut shells, place them in an oven, and dry them at 80°C to a constant weight to obtain dried peanut shells. Crush them using a pulverizer and pass them through a 10-mesh sieve to obtain peanut shell powder.

[0034] After the red mud was air-dried, it was passed through an 18-mesh sieve to obtain red mud powder. 2g of red mud powder was added to a beaker containing 400mL of deionized water and stirred at 25℃ and 1750rpm for 30min to obtain a stable red mud suspension.

[0035] S2, take 10g of peanut shell powder and mix it with red mud suspension, stir at 25℃ and 870rpm for 60min, filter out excess water immediately after stirring, and dry at 60℃ to constant weight to obtain pretreated peanut shell powder.

[0036] S3. Place 10g of pretreated peanut shell powder in a quartz boat, then place the boat into a tube furnace. Open the nitrogen cylinder pressure reducing valve and adjust the nitrogen pressure to 0.3MPa. Pre-ventilate for 10 minutes to expel as much air as possible from the tube and create an oxygen-deficient environment. Set the final carbonization temperature of the tube furnace to 700℃, with a heating rate of 10℃ / min. Pyrolysis is performed at 700℃ for 2 hours. After pyrolysis, continue purging with nitrogen until room temperature is reached, yielding the biochar-supported red mud adsorbent material (RMBC400).

[0037] Example 2

[0038] A method for preparing biochar-supported red mud adsorbent material, such as Figure 1 As shown, it includes the following steps:

[0039] S1. Wash the waste peanut shells, place them in an oven, and dry them at 80°C to a constant weight to obtain dried peanut shells. Crush them using a pulverizer and pass them through a 10-mesh sieve to obtain peanut shell powder.

[0040] After the red mud was air-dried, it was passed through an 18-mesh sieve to obtain red mud powder. 2g of red mud powder was added to a beaker containing 500mL of deionized water and stirred at 25℃ and 1750rpm for 30min to obtain a stable red mud suspension.

[0041] S2, take 10g of peanut shell powder and mix it with red mud suspension, stir at 25℃ and 870rpm for 60min, filter out excess water immediately after stirring, and dry at 60℃ to constant weight to obtain pretreated peanut shell powder.

[0042] S3. Place 10g of pretreated peanut shell powder in a quartz boat, put the boat into a tube furnace, and then open the nitrogen cylinder pressure reducing valve to adjust the nitrogen pressure to 0.5MPa. Pre-ventilate for 10 minutes to expel as much air as possible from the tube and create an oxygen-deficient environment. Set the final carbonization temperature of the tube furnace to 700℃, with a heating rate of 10℃ / min, and pyrolyze at 700℃ for 2 hours. After pyrolysis, continue to purge with nitrogen until room temperature is reached, thus obtaining biochar-supported red mud adsorbent material (RMBC500) or (700RMBC).

[0043] Example 3

[0044] A method for preparing a biochar-supported red mud adsorbent material includes the following steps:

[0045] S1. Wash the waste peanut shells, place them in an oven, and dry them at 80°C to a constant weight to obtain dried peanut shells. Crush them using a pulverizer and pass them through a 10-mesh sieve to obtain peanut shell powder.

[0046] After the red mud was air-dried, it was passed through an 18-mesh sieve to obtain red mud powder. 2g of red mud powder was added to a beaker containing 600mL of deionized water and stirred at 25℃ and 1750rpm for 30min to obtain a stable red mud suspension.

[0047] S2, take 10g of peanut shell powder and mix it with red mud suspension, stir at 25℃ and 870rpm for 60min, filter out excess water immediately after stirring, and dry at 60℃ to constant weight to obtain pretreated peanut shell powder.

[0048] S3. Place 10g of pretreated peanut shell powder in a quartz boat, then place the boat into a tube furnace. Open the nitrogen cylinder pressure reducing valve and adjust the nitrogen pressure to 0.4MPa. Pre-ventilate for 10 minutes to expel as much air as possible from the tube and create an oxygen-deficient environment. Set the final carbonization temperature of the tube furnace to 700℃, with a heating rate of 10℃ / min. Pyrolysis is performed at 700℃ for 2 hours. After pyrolysis, continue purging with nitrogen until room temperature is reached, yielding the biochar-supported red mud adsorbent material (RMBC600).

[0049] Example 4

[0050] A method for preparing a biochar-supported red mud adsorbent material includes the following steps:

[0051] S1. Wash the waste peanut shells, place them in an oven, and dry them at 80°C to a constant weight to obtain dried peanut shells. Crush them using a pulverizer and pass them through a 10-mesh sieve to obtain peanut shell powder.

[0052] After the red mud was air-dried, it was passed through an 18-mesh sieve to obtain red mud powder. 2g of red mud powder was added to a beaker containing 500mL of deionized water and stirred at 25℃ and 1750rpm for 30min to obtain a stable red mud suspension.

[0053] S2, take 10g of peanut shell powder and mix it with red mud suspension, stir at 25℃ and 870rpm for 60min, filter out excess water immediately after stirring, and dry at 60℃ to constant weight to obtain pretreated peanut shell powder.

[0054] S3. Place 10g of pretreated peanut shell powder in a quartz boat, then place the boat into a tube furnace. Open the nitrogen cylinder pressure reducing valve and adjust the nitrogen pressure to 0.5MPa. Pre-ventilate for 10 minutes to expel as much air as possible from the tube and create an oxygen-deficient environment. Set the final carbonization temperature of the tube furnace to 600℃, with a heating rate of 10℃ / min. Pyrolysis is performed at 600℃ for 2 hours. After pyrolysis, continue purging with nitrogen until room temperature is reached, yielding the biochar-supported red mud adsorbent material (600RMBC).

[0055] Example 5

[0056] A method for preparing a biochar-supported red mud adsorbent material includes the following steps:

[0057] S1. Wash the waste peanut shells, place them in an oven, and dry them at 80°C to a constant weight to obtain dried peanut shells. Crush them using a pulverizer and pass them through a 10-mesh sieve to obtain peanut shell powder.

[0058] After the red mud was air-dried, it was passed through an 18-mesh sieve to obtain red mud powder. 2g of red mud powder was added to a beaker containing 500mL of deionized water and stirred at 25℃ and 1750rpm for 30min to obtain a stable red mud suspension.

[0059] S2, take 10g of peanut shell powder and mix it with red mud suspension, stir at 25℃ and 870rpm for 60min, filter out excess water immediately after stirring, and dry at 60℃ to constant weight to obtain pretreated peanut shell powder.

[0060] S3. Place 10g of pretreated peanut shell powder in a quartz boat, then place the boat into a tube furnace. Open the nitrogen cylinder pressure reducing valve and adjust the nitrogen pressure to 0.3MPa. Pre-ventilate for 10 minutes to expel as much air as possible from the tube and create an oxygen-deficient environment. Set the final carbonization temperature of the tube furnace to 750℃, with a heating rate of 10℃ / min. Pyrolysis is performed at 750℃ for 2 hours. After pyrolysis, continue purging with nitrogen until room temperature is reached, yielding the biochar-supported red mud adsorbent material (750RMBC).

[0061] Example 6 (Red mud powder to peanut shell powder mass ratio is 1:1)

[0062] A method for preparing a biochar-supported red mud adsorbent material includes the following steps:

[0063] S1. Wash the waste peanut shells, place them in an oven, and dry them at 80°C to a constant weight to obtain dried peanut shells. Crush them using a pulverizer and pass them through a 10-mesh sieve to obtain peanut shell powder.

[0064] After the red mud was air-dried, it was passed through an 18-mesh sieve to obtain red mud powder. 10g of red mud powder was added to a beaker containing 500mL of deionized water and stirred at 25℃ and 1750rpm for 30min to obtain a stable red mud suspension.

[0065] S2, take 10g of peanut shell powder and mix it with red mud suspension, stir at 25℃ and 870rpm for 60min, filter out excess water immediately after stirring, and dry at 60℃ to constant weight to obtain pretreated peanut shell powder.

[0066] S3. Place 10g of pretreated peanut shell powder in a quartz boat, put the boat into a tube furnace, and then open the nitrogen cylinder pressure reducing valve to adjust the nitrogen pressure to 0.4MPa. Pre-ventilate for 10 minutes to expel as much air as possible from the tube and create an oxygen-deficient environment. Set the final carbonization temperature of the tube furnace to 700℃, the heating rate to 10℃ / min, and pyrolyze at 700℃ for 2 hours. After pyrolysis, continue to purge with nitrogen until room temperature is reached, thus obtaining the biochar-supported red mud adsorbent material (RMBC1).

[0067] Example 7 (Red mud powder to peanut shell powder mass ratio is 1:2)

[0068] A method for preparing a biochar-supported red mud adsorbent material includes the following steps:

[0069] S1. Wash the waste peanut shells, place them in an oven, and dry them at 80°C to a constant weight to obtain dried peanut shells. Crush them using a pulverizer and pass them through a 10-mesh sieve to obtain peanut shell powder.

[0070] After the red mud was air-dried, it was passed through an 18-mesh sieve to obtain red mud powder. 5g of red mud powder was added to a beaker containing 500mL of deionized water and stirred at 25℃ and 1750rpm for 30min to obtain a stable red mud suspension.

[0071] S2, take 10g of peanut shell powder and mix it with red mud suspension, stir at 25℃ and 870rpm for 60min, filter out excess water immediately after stirring, and dry at 60℃ to constant weight to obtain pretreated peanut shell powder.

[0072] S3. Place 10g of pretreated peanut shell powder in a quartz boat, then place the boat into a tube furnace. Open the nitrogen cylinder pressure reducing valve and adjust the nitrogen pressure to 0.5MPa. Pre-ventilate for 10 minutes to expel as much air as possible from the tube and create an oxygen-deficient environment. Set the final carbonization temperature of the tube furnace to 700℃, with a heating rate of 10℃ / min. Pyrolysis is performed at 700℃ for 2 hours. After pyrolysis, continue purging with nitrogen until room temperature is reached, yielding the biochar-supported red mud adsorbent material (RMBC2).

[0073] Example 8 (Red mud powder to peanut shell powder mass ratio is 1:10)

[0074] A method for preparing a biochar-supported red mud adsorbent material includes the following steps:

[0075] S1. Wash the waste peanut shells, place them in an oven, and dry them at 80°C to a constant weight to obtain dried peanut shells. Crush them using a pulverizer and pass them through a 10-mesh sieve to obtain peanut shell powder.

[0076] After the red mud was air-dried, it was passed through an 18-mesh sieve to obtain red mud powder. 1g of red mud powder was added to a beaker containing 500mL of deionized water and stirred at 25℃ and 1750rpm for 30min to obtain a stable red mud suspension.

[0077] S2, take 10g of peanut shell powder and mix it with red mud suspension, stir at 25℃ and 870rpm for 60min, filter out excess water immediately after stirring, and dry at 60℃ to constant weight to obtain pretreated peanut shell powder.

[0078] S3. Place 10g of pretreated peanut shell powder in a quartz boat, then place the boat into a tube furnace. Open the nitrogen cylinder pressure reducing valve and adjust the nitrogen pressure to 0.3MPa. Pre-ventilate for 10 minutes to expel as much air as possible from the tube and create an oxygen-deficient environment. Set the final carbonization temperature of the tube furnace to 700℃, with a heating rate of 10℃ / min. Pyrolysis is performed at 700℃ for 2 hours. After pyrolysis, continue purging with nitrogen until room temperature is reached, yielding the biochar-supported red mud adsorbent material (RMBC3).

[0079] To further illustrate the technical effects of the present invention, comparative examples are also provided, as follows:

[0080] Comparative Example 1

[0081] The difference compared to Example 6 is that the mass ratio of red mud powder to peanut shell powder is 0:10.

[0082] A method for preparing biochar adsorbent material includes the following steps:

[0083] S1. Wash the waste peanut shells, place them in an oven, and dry them at 80°C to a constant weight to obtain dried peanut shells. Crush them using a pulverizer and pass them through a 10-mesh sieve to obtain peanut shell powder.

[0084] S2, place 10g of peanut shell powder in a quartz boat, put the quartz boat into a tube furnace, and then open the nitrogen cylinder pressure reducing valve to adjust the nitrogen pressure to 0.4MPa. Pre-ventilate for 10 minutes to expel as much air as possible from the tube and create an oxygen-deficient environment. Set the final carbonization temperature of the tube furnace to 700℃, the heating rate to 10℃ / min, and pyrolyze at 700℃ for 2 hours. After pyrolysis, continue to purge with nitrogen until room temperature is reached, thus obtaining the biochar adsorbent material (BC).

[0085] Comparative Example 2

[0086] The difference compared to Example 2 is that the final carbonization temperature of the tubular furnace is adjusted to 300°C.

[0087] A method for preparing a biochar-supported red mud adsorbent material includes the following steps:

[0088] S1. Wash the waste peanut shells, place them in an oven, and dry them at 80°C to a constant weight to obtain dried peanut shells. Crush them using a pulverizer and pass them through a 10-mesh sieve to obtain peanut shell powder.

[0089] After the red mud was air-dried, it was passed through an 18-mesh sieve to obtain red mud powder. 2g of red mud powder was added to a beaker containing 500mL of deionized water and stirred at 25℃ and 1750rpm for 30min to obtain a stable red mud suspension.

[0090] S2, take 10g of peanut shell powder and mix it with red mud suspension, stir at 25℃ and 870rpm for 60min, filter out excess water immediately after stirring, and dry at 60℃ to constant weight to obtain pretreated peanut shell powder.

[0091] S3. Place 10g of pretreated peanut shell powder in a quartz boat, put the boat into a tube furnace, and then open the nitrogen cylinder pressure reducing valve to adjust the nitrogen pressure to 0.5MPa. Pre-aerate for 10 minutes to create an oxygen-deficient environment by purging as much air as possible from the tube. Set the final carbonization temperature of the tube furnace to 300℃, with a heating rate of 10℃ / min, and pyrolyze at 300℃ for 2 hours. After pyrolysis, continue to purge with nitrogen until room temperature is reached, thus obtaining the biochar-supported red mud adsorbent material (300RMBC).

[0092] Comparative Example 3

[0093] The difference compared to Example 2 is that the final carbonization temperature of the tubular furnace is adjusted to 500°C.

[0094] A method for preparing a biochar-supported red mud adsorbent material includes the following steps:

[0095] S1. Wash the waste peanut shells, place them in an oven, and dry them at 80°C to a constant weight to obtain dried peanut shells. Crush them using a pulverizer and pass them through a 10-mesh sieve to obtain peanut shell powder.

[0096] After the red mud was air-dried, it was passed through an 18-mesh sieve to obtain red mud powder. 2g of red mud powder was added to a beaker containing 500mL of deionized water and stirred at 25℃ and 1750rpm for 30min to obtain a stable red mud suspension.

[0097] S2, take 10g of peanut shell powder and mix it with red mud suspension, stir at 25℃ and 870rpm for 60min, filter out excess water immediately after stirring, and dry at 60℃ to constant weight to obtain pretreated peanut shell powder.

[0098] S3. Place 10g of pretreated peanut shell powder in a quartz boat, then place the boat into a tube furnace. Open the nitrogen cylinder pressure reducing valve and adjust the nitrogen pressure to 0.5MPa. Pre-ventilate for 10 minutes to expel as much air as possible from the tube and create an oxygen-deficient environment. Set the final carbonization temperature of the tube furnace to 500℃, with a heating rate of 10℃ / min. Pyrolysis is performed at 500℃ for 2 hours. After pyrolysis, continue purging with nitrogen until room temperature is reached, yielding the biochar-supported red mud adsorbent material (500RMBC).

[0099] The biochar-supported red mud adsorbents prepared in each example and comparative example were applied to adsorb lead ions from wastewater. The specific process is as follows: 0.1 g of the biochar-supported red mud adsorbents prepared in Examples 1-3 were weighed into 50 mL centrifuge tubes. 35 mL of a 100 mg / L lead ion solution was added to each centrifuge tube. The pH was adjusted to 6 using 0.1 M dilute nitric acid and dilute sodium hydroxide solution. The three centrifuge tubes were simultaneously placed in a water bath constant-temperature shaker and shaken at 25°C and 180 rpm for 6 hours. After shaking, the solution was filtered through a 0.45 μm syringe filter membrane. The filtered solution was placed in a 10 mL centrifuge tube (acidified with 5% HNO3), and its concentration was detected by ICP-OES. The adsorption capacity and removal rate of lead ions were calculated using Equations 1 and 2. Three parallel experiments were set up for each sample, and the average value was taken. The results are as follows: Figure 2 and Figure 3 As shown.

[0100] Adsorption capacity formula:

[0101] Removal rate formula:

[0102] q e The adsorption capacity of red mud-modified biochar for heavy metal ions at adsorption equilibrium is mg / g; C0 is the initial concentration of heavy metal ions in the solution, mg / L; Ce is the concentration of heavy metal ions in the solution at equilibrium, mg / L; V is the solution volume, L; M is the mass of red mud-modified biochar, g; η is the removal rate of heavy metal ions, %.

[0103] The adsorption capacity and removal rate of lead ions in wastewater by biochar-supported red mud adsorbents prepared from red mud suspensions of different concentrations are shown in the figure below. Figure 2 As shown. By Figure 2It can be seen that for a lead ion solution with a concentration of 100 mg / L, the adsorption capacity of the biochar-supported red mud adsorbent material (RMBC500) in Example 2 reached 32.56 mg / g, with a removal rate of 93.0%; the adsorption capacities of the biochar-supported red mud adsorbent material (RMBC400) in Example 1 and the biochar-supported red mud adsorbent material (RMBC600) in Example 3 were 31.77 mg / g and 29.78 mg / g, respectively, with removal rates of 90.7% and 85.1%, respectively. Therefore, the concentration of red mud in the red mud suspension also has a certain influence on the adsorption performance of the adsorbent material for lead ions.

[0104] The adsorption capacity and removal rate of lead ions in wastewater by biochar-supported red mud adsorbents prepared at different pyrolysis temperatures are shown in the following figures. Figure 3 As shown. Since the biochar-supported red mud adsorbent materials prepared in Examples 2, 4, and 5 have similar adsorption capacity and removal rate for lead ions in wastewater, only examples are used here. Figure 3 It can be seen that for a lead ion solution with a concentration of 100 mg / L, the adsorption capacity and removal rate of lead ions increase with increasing pyrolysis temperature. The 700 RMBC prepared in Example 2 showed the best adsorption effect, with an adsorption capacity of 32.56 mg / g and a removal rate of 93.0%. The adsorption capacities of the 300 RMBC prepared in Comparative Example 2 and the 500 RMBC prepared in Comparative Example 3 were 21.33 mg / g and 27.14 mg / g, respectively, with removal rates of 60.9% and 77.5%, respectively. Therefore, the pyrolysis temperature adopted in this invention improves the adsorption capacity and effective removal of lead ions from wastewater by the biochar-supported red mud adsorbent material.

[0105] The biochar-supported red mud adsorbent materials prepared in Examples 6-8 and the biochar adsorbent material prepared in Comparative Example 1 were applied to adsorb lead ions from wastewater. The specific process is as follows: 0.1 g of each adsorbent material from the examples and the comparative example were weighed into 50 mL centrifuge tubes. 35 mL of solutions with lead ion concentrations of 20 mg / L, 50 mg / L, 100 mg / L, 200 mg / L, 400 mg / L, 600 mg / L, and 800 mg / L were added to each centrifuge tube. The pH was adjusted to 6 using 0.1 M dilute nitric acid and dilute sodium hydroxide solution. All four centrifuge tubes were simultaneously placed in a water bath constant-temperature shaker and shaken at 25°C and 180 rpm for 6 hours. After shaking, the solution was filtered through a 0.45 μm syringe filter membrane. The filtered solution was placed in a 10 mL centrifuge tube (acidified with 5% HNO3), and its concentration was detected using ICP-OES. The adsorption capacity and removal rate were calculated. Three parallel experiments were set up for each sample, and the average value was taken.

[0106] Langmuir isotherm model equations:

[0107] Freundlich isotherm model equations:

[0108] K L q represents the Langmuir model adsorption constant, in L / mg; m The maximum adsorption capacity of red mud-modified biochar is mg / g; K F denoted as the Freundlich model adsorption constant; 1 / n represents the strength of adsorption or surface heterogeneity, indicating the relative energy distribution and the heterogeneity of adsorption sites. When 0 < 1 / n < 1, adsorption is favorable; when 1 / n > 1, adsorption is unfavorable; and when 1 / n = 1, the adsorption process is irreversible.

[0109] The adsorption capacity and removal rate of lead ions in wastewater by biochar-supported red mud adsorbents prepared with different mass ratios of red mud powder and peanut shell powder are shown in the figure below. Figure 4 As shown. By Figure 4 It can be seen that for heavy metal lead solutions with a concentration range of 20–800 mg / L, the maximum adsorption capacities of the biochar-supported red mud adsorbent materials (RMBC1, RMBC2, and RMBC3) in Examples 6, 7, and 8 are 80.25 mg / g, 64.34 mg / g, and 58.01 mg / g, respectively. These are 1.90 times, 1.52 times, and 1.37 times higher than the maximum adsorption capacity of the biochar adsorbent material (BC) in Comparative Example 1, which is 42.23 mg / g. Furthermore, the removal rate curves show that the removal rate of RMBC1 is greater than that of RMBC2, RMBC3, and BC.

[0110] The experimental results were fitted using the Langmuir isotherm model equation (Equation 3) and the Freundlich isotherm model equation (Equation 4), and the results are as follows: Figure 5 As shown in Table 1. From Figure 5 As shown in Table 1, the Langmuir isotherm provides the best fit, with a goodness of fit R0. 2 All values ​​were above 0.90, and the fitted theoretical maximum adsorption capacity was close to the actual maximum adsorption capacity, indicating that the adsorption process of the biochar-supported red mud adsorbent material prepared in this invention can be better described by the Langmuir isotherm. Therefore, appropriately increasing the proportion of red mud, i.e., increasing the mass ratio of red mud to peanut shells, helps to improve the adsorption effect of lead ions based on biochar-supported red mud adsorbent material. For the biochar-supported red mud adsorbent material of this invention, the optimal mass ratio is 1:1.

[0111] Table 1. Fitting parameters for adsorption isotherms

[0112]

[0113] The adsorption effect of the biochar-supported red mud adsorbent material prepared in Example 6 on lead ions in wastewater at different adsorption times was investigated. The specific process is as follows: 0.1 g of the biochar-supported red mud adsorbent material RMBC1 prepared in Example 6 was weighed into 50 mL centrifuge tubes. 35 mL of a lead ion concentration of 250 mg / L was added to each centrifuge tube. The pH was adjusted to 6 using 0.1 M dilute nitric acid and dilute sodium hydroxide solution. The four centrifuge tubes were simultaneously placed in a water bath constant temperature shaker and shaken at 25℃ and 180 rpm for 5, 30, 60, 120, 240, 480, and 720 min, respectively. After shaking, the solution was filtered through a 0.45 μm syringe filter membrane. The filtered solution was placed in a 10 mL centrifuge tube (acidified with 5% HNO3), and its concentration was detected by ICP-OES. The adsorption capacity and removal rate were calculated. Three parallel experiments were set up for each sample, and the average value was taken.

[0114] Calculations show that the adsorption capacities of the biochar-supported red mud adsorbent RMBC1 prepared in Example 6 were 69.2 mg / g, 72.1 mg / g, and 73.6 mg / g at 240 min, 480 min, and 720 min, respectively, with almost constant adsorption capacities and removal rates around 80%. In contrast, the adsorption capacities of RMBC1 at 5 min, 30 min, 60 min, and 120 min were 25.6 mg / g, 35.7 mg / g, 40.3 mg / g, and 51.0 mg / g, respectively, with removal rates of 29.3%, 40.8%, 46.1%, and 58.3%. Therefore, it can be seen that the RMBC1 in this invention reaches equilibrium with an initial lead ion solution of 250 mg / g after 4 hours, and the lead ion concentration does not change significantly thereafter.

[0115] X-ray diffraction analysis comparison diagrams of the biochar-supported red mud adsorbent materials prepared in Examples 6-8 of this invention and the biochar adsorbent material prepared in Comparative Example 1 are shown below. Figure 6 As shown. By Figure 6 It can be seen that, compared with the biochar-supported red mud adsorbent materials prepared in Examples 7 and 8 and the biochar adsorbent material prepared in Comparative Example 1, RMBC1 prepared in Example 6 is closer to the spectral morphology of red mud. Moreover, as the proportion of red mud increases, the two broad peaks of the unique carbon morphology of biochar adsorbent material BC become more gradual, and the broad peaks are basically not visible in the spectrum of RMBC1. As the proportion of red mud increases, the characteristic peaks of red mud also appear more and more obviously on the biochar-supported red mud adsorbent material, indicating that red mud can improve the crystal properties of biochar.

[0116] Fourier transform infrared (FTIR) comparison images of the biochar-supported red mud adsorbent materials prepared in Examples 6-8 of this invention and the biochar adsorbent material prepared in Comparative Example 1 are shown below. Figure 7 As shown. By Figure 7It can be seen that at 987cm -1 The modified biochar from red mud exhibited vibrational bands characteristic of red mud, namely Si-O-Si and Al-O-Si, at a depth of 688 cm⁻¹. -1 and 570cm -1 The absorption peaks of Si-O / Al-O and Si-O-Al bonds and the 460 cm⁻¹ -1 The Fe-O vibrational peaks are located nearby. These vibrational peaks become more pronounced with increasing red mud content, indicating a higher red mud content loaded on the biochar material. The vibrational peak shape of RMBC1 is most similar to that of red mud. At 2080 cm⁻¹... -1 The biochar and amorphous CO3 on the left and right 2- The absorption peaks were all retained on the red mud-modified biochar; the biochar at 867 cm⁻¹ was also observed. -1 Nearby CO3 2 - Vibration absorption peak and red mud at 885cm -1 Nearby CO3 2- Vibrational absorption peaks overlap on red mud-modified biochar.

[0117] Scanning electron microscope (SEM) comparison images of the biochar-supported red mud adsorbent materials prepared in Examples 6-8 of this invention and the biochar adsorbent material prepared in Comparative Example 1 are shown below. Figure 8 As shown. By Figure 8 It can be seen that the BC surface prepared in Comparative Example 1 is relatively smooth and has abundant pores, with a predominantly layered and network-like morphology in some areas. In contrast, the red mud successfully adhered to the surface and surrounding area of ​​the RMBC2 prepared in Example 7 and the RMBC3 prepared in Example 8, but the loading was relatively small, with scattered distribution on the material surface, and a clear biochar structure was visible. From the RMBC1 material prepared in Example 6, it can be seen that a large amount of red mud adhered to the biochar surface, and the original sheet-like and porous structure of the biochar was not obvious, with almost no exposed surface area. Therefore, the preparation method provided by this invention has a good modification effect on biochar, and the red mud can be loaded relatively uniformly on the surface of the biochar material.

[0118] In summary, the biochar-supported red mud adsorbent material provided by this invention increases the specific surface area and the number of surface functional groups of the adsorbent material by loading red mud onto the surface of biochar, thereby improving the adsorption performance and selectivity of biochar. The stable carbon structure of biochar effectively disperses the red mud particles, increasing the total adsorption sites of the adsorbent material, thus improving the strength structure and adsorption efficiency of red mud, and achieving rapid and large-scale absorption of lead ions. It also exhibits excellent performance in the efficient removal of lead from industrial wastewater.

[0119] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a biochar-supported red mud adsorbent material, characterized in that, Includes the following steps: Water is added to red mud powder and stirred to obtain a red mud suspension. Fruit shell powder is added to the red mud suspension and stirred at 18-26°C. The mixture is then filtered and dried to obtain pretreated fruit shell powder. The pretreated fruit shell powder was pyrolyzed at 600–750°C under a protective atmosphere and then cooled to obtain red mud modified biochar.

2. The preparation method according to claim 1, characterized in that, The mass ratio of red mud powder to fruit shell powder is 1:1 to 10.

3. The preparation method according to claim 1, characterized in that, The ratio of red mud powder to water is 1g:50-300mL.

4. The preparation method according to claim 1, characterized in that, The red mud powder passes through an 18-mesh sieve, and the fruit shell powder passes through a 10-mesh sieve.

5. The preparation method according to claim 1, characterized in that, The shells include peanut shells, walnut shells, or melon seed shells.

6. The preparation method according to claim 1, characterized in that, The heating rate is 10°C / min.

7. The preparation method according to claim 1, characterized in that, The pyrolysis time is 2 to 4 hours.

8. A biochar-supported red mud adsorbent material prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the biochar-supported red mud adsorbent material according to claim 8 in the removal of heavy metal ions from wastewater, characterized in that, The biochar-supported red mud adsorbent material was added to wastewater containing heavy metal ions and adsorbed by shaking.

10. The application according to claim 9, characterized in that, The amount of biochar-supported red mud adsorbent material added is 0.1 g / 35 mL, the pH value of the wastewater containing heavy metal ions is 6, and the concentration of heavy metal ions is 20-200 mg / L.

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