Method for preparing load type nano zero-valent iron from Anshan type iron tailings

Abstract

The invention discloses a method for preparing load type nano zero-valent iron by using Anshan type iron tailings, which comprises the following steps: dispersing coffee grounds A in water, sealing and stirring I, cooling to normal temperature, and carrying out vacuum filtration to obtain an extracting solution and coffee grounds B; adding a mixture of orange peel, shaddock peel and orange peel into the extracting solution, and sealing and stirring II to obtain a green reducing solution; the ground Anshan type iron tailing powder is placed in a crucible A, coffee grounds B are placed in a crucible B, roasting is conducted, and pretreated Anshan type iron tailings are obtained; the pretreated Anshan type iron tailings are placed in a sulfuric acid solution, sealed stirring is conducted, the pH is adjusted to be lower than 2.5, and an iron solution and leaching residues are obtained; drying the leaching residues, adding sodium hydroxide, roasting, adding water and a phosphoric acid solution to adjust the pH value to 7.5-8.5 to form hydrogel, aging and drying to obtain silicon dioxide aerogel; and putting the silicon dioxide aerogel into the diluted iron solution, stirring in an inert atmosphere, dropwise adding the green reduction solution, reacting, freezing and drying to obtain the load type nano zero-valent iron.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization technology, specifically involving a method for preparing supported nano-zero-valent iron using Anshan-type iron tailings. Background Technology

[0002] The large-scale stockpiling of Anshan-type iron ore tailings poses severe environmental pressure and safety hazards, and its high-value-added resource utilization remains a challenge in the field. On the other hand, nano-zero-valent iron, which holds great potential in water pollution control, is limited in practical application due to its inherent defects of easy agglomeration and oxidation. While existing loading technologies can partially alleviate this problem, the carriers used (such as activated carbon) are expensive and have limited functionality. It is worth noting that Anshan-type iron ore tailings are rich in components such as silica, making them ideal raw materials for preparing porous carriers, but existing technologies have not fully utilized this characteristic. Therefore, this invention aims to solve these two major challenges synergistically, providing a method for preparing low-cost, high-performance loaded nano-zero-valent iron from iron tailings, simultaneously achieving the dual goals of solid waste resource utilization and the development of new environmentally friendly materials.

[0003] CN 108911599B discloses a method for simultaneously preparing iron oxide and silica aerogel pads from iron tailings. The method uses iron tailings as raw material, which is successively ground, pulverized, and activated by high-temperature roasting. The activated iron tailings powder is mixed with hydrochloric acid and stirred to obtain filter residue and filtrate. The filter residue is mixed with sodium hydroxide particles, roasted, and then dissolved in water for heating and reaction. After passing through a cation exchange resin, the solution is adjusted to neutral with ammonia solution and then impregnated with glass fiber felt. The glass fiber felt is repeatedly squeezed to ensure uniform distribution of silica sol within it. After standing and gelling, a gel pad is obtained. This pad is then aged, subjected to solvent exchange, and surface modification to obtain a hydrophobic silica aerogel pad. The filtrate is adjusted to a slightly alkaline pH with ammonia, filtered after standing, and dried to obtain iron oxide nanoparticles. This method does not disclose the technical solution of using silica aerogel prepared from iron tailings as a carrier to load nano-zero valent iron, nor does it involve the method of using biomass extract as a green reducing agent to prepare nano-zero valent iron. It has the problems of insufficient depth of resource utilization of silicon and iron elements in iron tailings and failure to achieve the preparation of higher value-added nano-zero valent iron materials. Summary of the Invention

[0004] To address the aforementioned issues, this invention provides a method for preparing supported nano-zero-valent iron using Anshan-type iron tailings. This method transforms two types of solid waste—Anshan-type iron tailings and biomass waste such as coffee grounds / fruit peels—into high-value environmental remediation materials, achieving a qualitative leap from "waste" to "product." It provides a novel, high-value-added technological path for solid waste resource utilization. By using natural products extracted from coffee grounds, orange peels, etc., as reducing agents, it completely replaces the high-cost and toxic strong chemical reducing agents such as sodium borohydride used in traditional methods, eliminating the use of hazardous chemicals at the source and making the entire preparation process safer and more environmentally friendly.

[0005] According to one aspect of the present invention, a method for preparing supported nano-zero-valent iron using Anshan-type iron tailings is provided, comprising the following steps:

[0006] Step 1, Preparation of green reducing solution: Disperse coffee grounds A in water, seal and stir I, cool to room temperature and then vacuum filter to obtain extract A and coffee grounds B; add a mixture of orange peel, grapefruit peel and tangerine peel to extract A, seal and stir II, vacuum filter to obtain extract B, and concentrate by rotary evaporation to obtain green reducing solution; Step 2, Pretreatment of Anshan-type iron tailings: Place the ground Anshan-type iron tailings powder in crucible A, place the coffee grounds B obtained in step 1 in crucible B, and roast to obtain pretreated Anshan-type iron tailings. The roasting of coffee grounds is to provide a reducing atmosphere during the tailings magnetization roasting process. Step 3, Preparation of iron solution: The pretreated Anshan-type iron tailings obtained in Step 2 are placed in sulfuric acid solution I, sealed and stirred, sulfuric acid solution II is added dropwise to adjust the pH to below 2.5, and vacuum filtered to obtain iron solution and leaching residue; Step 4, Preparation of silica aerogel: The leaching residue obtained in step 3 is placed in an oven for drying, sodium hydroxide is added and then calcined, water is added and stirred, phosphoric acid solution is added to adjust the pH to 7.5~8.5 to form a hydrogel, aged and dried to obtain silica aerogel; Step 5, Preparation of supported nano-zero valent iron: Dilute the iron solution obtained in step 3, place the silica aerogel prepared in step 4 into the diluted iron solution, stir under an inert atmosphere, add the green reducing solution obtained in step 1 dropwise, centrifuge after the reaction is complete, freeze and dry the obtained solid to obtain supported nano-zero valent iron.

[0007] Based on the above technical solution, the mass-volume ratio of coffee grounds A to water in step 1 is 200~400g:500~900ml; The conditions for sealed stirring I in step 1 are as follows: The temperature of the sealed stirring I is 80~100℃; The time for the sealed stirring I is 1~2 hours; In step 1, the mass ratio of orange peel, grapefruit peel, and tangerine peel in the mixture is 2:2:1. The mass ratio of extract A to the mixture of orange peel, grapefruit peel and tangerine peel in step 1 is 5~10:1~3; The conditions for sealed stirring II in step 1 are as follows: The temperature of the sealed stirring II is 60~80℃; The sealing stirring time II is 1~2 hours.

[0008] Based on the above technical solution, the coffee grounds A are selected from coffee shops and have a moisture content of 40-45%.

[0009] Based on the above technical solution, the composition of the iron tailings in Anshan City mentioned in step 2 is as follows: 21.1%~32.8% Fe2O3, 62.5%~74.2% SiO2, 1.4%~1.8% Al2O3, 1.0%~1.1% CaO, 0.2%~0.4% K2O, 1.1%~1.3% MgO, and 0.75%~0.77% Na2O; The pretreatment of Anshan-type iron tailings in step 2 is as follows: Grind the Anshan-type iron tailings to 200 mesh and place them in crucible A. Place coffee grounds B in crucible B and place them parallel in a muffle furnace. Roast at 700~900℃ for 3~5 hours, seal and cool to room temperature. Grind the roasted Anshan-type iron tailings to 200 mesh again to obtain the pretreated Anshan-type iron tailings. The parallel placement is to ensure that the iron tailings are fully roasted.

[0010] Based on the above technical solution, the preparation of the iron solution in step 3 is as follows: 40-60g of pretreated Anshan-type iron tailings is placed in 200-500ml of sulfuric acid solution I with a pH of 0.6-1.0, and stirred in a sealed container at 35-38℃ for 6-24h. Every 1h, 20% sulfuric acid solution II is added dropwise to adjust the pH to below 2.5. The mixture is then vacuum filtered to obtain the iron solution and leaching residue.

[0011] Based on the above technical solution, the preparation of silica aerogel in step 4 is as follows: 20-40g of leaching residue is placed in an oven at 60℃ and dried for 6-12h. After adding 20-40g of sodium hydroxide, it is calcined at 650-800℃ for 2-5h. 100-200ml of water is added and stirred for 30-90min. A 15-25% phosphoric acid solution is added to adjust the pH to 7.5-8.5 to form a hydrogel. The hydrogel is aged in water and ethanol at room temperature for 36-48h and dried at 60℃ to constant weight to obtain silica aerogel.

[0012] Based on the above technical solution, the preparation of the supported nano-zero valent iron in step 5 is as follows: dilute the iron solution obtained in step 3 by 10-20 times, place the silica aerogel in the diluted iron solution, stir under an inert atmosphere, add green reducing solution dropwise, react at 21-25℃ for 6-24h, centrifuge, freeze the obtained solid at -20--18℃ for 24-48h, and dry in a freeze dryer at -60--50℃ for 24-48h to obtain supported nano-zero valent iron; The mass-to-volume ratio of the silica aerogel, the diluted iron solution, and the green reducing solution is 1~1.2g:10~50ml:10~250ml, wherein the iron ion concentration in the diluted iron solution is 0.03~0.07mol / L.

[0013] Beneficial effects (1) The technical solution disclosed in this invention successfully transforms two types of solid waste—Anshan-style iron tailings and biomass waste such as coffee grounds / fruit peels—into high-value environmental remediation materials. This achieves a qualitative change from "waste" to "product," providing a new, high-value-added technical path for the resource utilization of solid waste; (2) Compared with the traditional method of using commercial carriers (such as activated carbon) and chemical reducing agents (such as sodium borohydride), the technical solution disclosed in this invention uses iron tailings with almost zero cost as iron and silicon sources and common biomass waste as reducing agents. The raw material cost is extremely low, which greatly reduces the preparation threshold of high-performance nano zero-valent iron and lays the foundation for its large-scale production and practical engineering application. (3) The technical solution disclosed in this invention uses silica aerogel prepared from iron tailings leaching residue as a carrier. It has a high specific surface area and porous structure, which provides abundant loading sites for the generation of nano-zero valent iron and effectively prevents the migration and aggregation of nanoparticles. (4) The technical solution disclosed in this invention uses natural products extracted from coffee grounds, orange peels and the like as reducing agents, which completely replaces the high-cost and toxic strong chemical reducing agents such as sodium borohydride in traditional methods. This eliminates the use of high-risk chemicals from the source, making the entire preparation process safer and more environmentally friendly, and in line with the principles of green chemistry. Detailed Implementation

[0014] To make the objectives and technical solutions of this invention clearer, the following embodiments are provided for further explanation. However, the scope of protection of this invention is not limited to these embodiments; the embodiments are merely for illustrative purposes. Those skilled in the art should understand that any changes or equivalent substitutions that do not depart from the concept of this invention are included within the scope of protection of this invention.

[0015] Unless otherwise specified, all reagents and raw materials used in this invention are obtained through purchase.

[0016] The present invention provides a method for preparing supported nano-zero-valent iron using Anshan-type iron tailings in the specific embodiments section, comprising the following steps: Step 1, Preparation of green reducing solution: Disperse coffee grounds A in water, seal and stir I, cool to room temperature and then vacuum filter to obtain extract A and coffee grounds B; add a mixture of orange peel, grapefruit peel and tangerine peel to extract A, seal and stir II, vacuum filter to obtain extract B, and concentrate by rotary evaporation to obtain green reducing solution; Step 2, Pretreatment of Anshan-type iron tailings: Place the ground Anshan-type iron tailings powder in crucible A, place the coffee grounds B obtained in step 1 in crucible B, and roast to obtain pretreated Anshan-type iron tailings. Step 3, Preparation of iron solution: The pretreated Anshan-type iron tailings obtained in Step 2 are placed in sulfuric acid solution I, sealed and stirred, sulfuric acid solution II is added dropwise to adjust the pH to below 2.5, and vacuum filtered to obtain iron solution and leaching residue; Step 4, Preparation of silica aerogel: The leaching residue obtained in step 3 is placed in an oven for drying, sodium hydroxide is added and then calcined, water is added and stirred, phosphoric acid solution is added to adjust the pH to 7.5~8.5 to form a hydrogel, aged and dried to obtain silica aerogel; Step 5, Preparation of supported nano-zero valent iron: Dilute the iron solution obtained in step 3, place the silica aerogel prepared in step 4 into the diluted iron solution, stir under an inert atmosphere, add the green reducing solution obtained in step 1 dropwise, centrifuge after the reaction is complete, freeze and dry the obtained solid to obtain supported nano-zero valent iron.

[0017] Based on the above technical solution, the mass-volume ratio of coffee grounds A to water in step 1 is 200~400g:500~900ml; The conditions for sealed stirring I in step 1 are as follows: The temperature of the sealed stirring I is 80~100℃; The time for the sealed stirring I is 1~2 hours; In step 1, the mass ratio of orange peel, grapefruit peel, and tangerine peel in the mixture is 2:2:1. The mass ratio of extract A to the mixture of orange peel, grapefruit peel and tangerine peel in step 1 is 5~10:1~3; The conditions for sealed stirring II in step 1 are as follows: The temperature of the sealed stirring II is 60~80℃; The sealing stirring time II is 1~2 hours.

[0018] Based on the above technical solution, the coffee grounds A are selected from coffee shops and have a moisture content of 40-45%.

[0019] Based on the above technical solution, the composition of the iron tailings in Anshan City mentioned in step 2 is as follows: 21.1%~32.8% Fe2O3, 62.5%~74.2% SiO2, 1.4%~1.8% Al2O3, 1.0%~1.1% CaO, 0.2%~0.4% K2O, 1.1%~1.3% MgO, and 0.75%~0.77% Na2O; The pretreatment of Anshan-type iron tailings in step 2 is as follows: grind the Anshan-type iron tailings to 200 mesh and place them in crucible A, place coffee grounds B in crucible B, place them parallel in a muffle furnace, roast at 700~900℃ for 3~5 hours, seal and cool to room temperature, grind the roasted Anshan-type iron tailings to 200 mesh again to obtain the pretreated Anshan-type iron tailings.

[0020] Based on the above technical solution, the preparation of the iron solution in step 3 is as follows: 40-60g of pretreated Anshan-type iron tailings is placed in 200-500ml of sulfuric acid solution I with a pH of 0.6-1.0, and stirred in a sealed container at 35-38℃ for 6-12h. A 20% sulfuric acid solution II is added dropwise to adjust the pH to below 2.5. The mixture is then vacuum filtered to obtain the iron solution and leaching residue.

[0021] Based on the above technical solution, the preparation of silica aerogel in step 4 is as follows: 20-40g of leaching residue is placed in a 60℃ oven and dried for 6-12h. After adding 20-40g of sodium hydroxide, it is calcined at 650-800℃ for 2-5h. 100-200ml of water is added and stirred for 30-90min. A 15%-25% phosphoric acid solution is added to adjust the pH to 7.5-8.5 to form a hydrogel. The hydrogel is aged in water and ethanol at room temperature for 36-48h and dried at 60℃ to constant weight to obtain silica aerogel.

[0022] Based on the above technical solution, the preparation of the supported nano-zero valent iron in step 5 is as follows: dilute the iron solution obtained in step 3 by 10-20 times, place the silica aerogel in the diluted iron solution, stir under an inert atmosphere, add green reducing solution dropwise, react at 21-25℃ for 6-24h, centrifuge, freeze at -20--18℃ for 24-48h, and dry in a freeze dryer at -60--50℃ for 24-48h to obtain supported nano-zero valent iron.

[0023] The mass-to-volume ratio of the silica aerogel, the diluted iron solution, and the green reducing solution is 1~1.2g:10~50ml:10~250ml, wherein the iron ion concentration in the diluted iron solution is 0.03~0.07mol / L.

[0024] Example 1 A method for preparing supported nano-zero-valent iron using Anshan-type iron tailings, specifically as follows: Step (1): Place 200g of coffee grounds A (purchased from a coffee shop) in a beaker, add 500mL of ultrapure water, seal and stir at 80℃ for 1h, cool to room temperature and then vacuum filter to obtain extract A. Place the separated coffee grounds in a 60℃ oven and dry at a constant temperature for 6h to obtain coffee grounds B. Add 300g of a mixture of orange peel, grapefruit peel and tangerine peel (mass ratio of orange peel, grapefruit peel and tangerine peel is 2:2:1) to extract A, seal and heat at 60℃ for 1h, then vacuum filter to obtain extract B. Place extract B in a rotary evaporator and evaporate at 35℃ until the volume of extract B is concentrated to 100mL to obtain green reducing solution.

[0025] Step (2): Grind 50g of Anshan-type iron tailings to 200 mesh and place it in crucible A; place 100g of coffee grounds B from step (1) in crucible B; place crucible A and crucible B in parallel in a muffle furnace for roasting at 700℃ for 3.5h; after roasting, seal and cool to room temperature; take out the iron tailings from crucible A and grind them again to 200 mesh to obtain pretreated Anshan-type iron tailings.

[0026] Step (3): Take 40g of the pretreated Anshan-type iron tailings described in step (2) into a beaker, add 200mL of sulfuric acid solution with pH=0.6, seal the beaker and place it in a magnetically stirred water bath, heat to 35℃, stir for 8h, monitor the pH of the solution every 1h during the period, add 20% sulfuric acid dropwise to adjust the pH of the solution so that the pH value of the solution is always below 2.5; after the stirring is finished, vacuum filter the mixture in the beaker to obtain iron solution and leaching residue; Step (4): Place the leaching residue from step (3) in a 60°C oven and dry for 6 hours. Take 20g of the dried leaching residue and mix it with 20g of sodium hydroxide. Place the mixture in a muffle furnace and calcine for 3 hours at a temperature of 650°C. Take 30g of the calcined mixture in a beaker and add 100mL of ultrapure water. Place the beaker in a magnetic stirrer and stir for 60 minutes. During stirring, add a 15% phosphoric acid solution to the beaker to adjust the pH of the solution to 8.0. Stop stirring to form a hydrogel. Place 100g of the hydrogel in 500ml of ultrapure water and age for 24 hours. Then, age it in 500ml of anhydrous ethanol for 48 hours. Place the aged hydrogel in a 60°C drying oven and dry to constant weight to obtain silica aerogel. Step (5): Dilute the iron solution obtained in step (3) by 10 times, place 5g of the silica aerogel obtained in step (4) in 200ml of the diluted iron solution, stir at a constant speed under an inert gas atmosphere (nitrogen), add 300ml of the green reducing solution described in step (1) dropwise, react at 25℃ for 12h, centrifuge at high speed, freeze the obtained solid at -18℃ for 24h, and dry it in a freeze dryer at -60℃ for 24h to obtain supported nano-zero valent iron. The specific surface area of ​​the obtained supported nano-zero valent iron is 629m². 2 / g, the total iron content in the supported nano-zero valent iron is 97.4%.

[0027] Example 2 A method for preparing supported nano-zero-valent iron using Anshan-type iron tailings, specifically as follows: Step (1): Place 200g of coffee grounds A in a beaker, add 500mL of ultrapure water, seal and stir at 80℃ for 1.5h, cool to room temperature and then vacuum filter to obtain extract A. Place the separated coffee grounds in a 60℃ oven and dry at a constant temperature for 8h to obtain coffee grounds B. Add 300g of a mixture of orange peel, grapefruit peel and tangerine peel (mass ratio of orange peel, grapefruit peel and tangerine peel is 2:2:1) to extract A, seal and heat at 60℃ for 1.5h, then vacuum filter to obtain extract B. Place extract B in a rotary evaporator and evaporate at 35℃ until the volume of extract B is concentrated to 100mL to obtain green reducing solution.

[0028] Step (2): Grind 50g of Anshan-type iron tailings to 200 mesh and place it in crucible A; place 100g of coffee grounds B from step (1) in crucible B; place crucible A and crucible B in parallel in a muffle furnace for roasting at 750℃ for 3.5h; after roasting, seal and cool to room temperature; remove the iron tailings from crucible A and grind them again to 200 mesh to obtain pretreated Anshan-type iron tailings.

[0029] Step (3): Take 40g of the pretreated Anshan-type iron tailings described in step (2) into a beaker, add 200mL of sulfuric acid solution with pH=0.6, seal the beaker and place it in a magnetic stirring water bath, heat to 35℃, stir for 12h, monitor the pH of the solution every 1h during the period, add 20% sulfuric acid dropwise to adjust the pH of the solution so that the pH value of the solution is always below 2.5; after the stirring is finished, vacuum filter the mixture in the beaker to obtain iron solution and leaching residue.

[0030] Step (4): Place the leaching residue obtained in step (3) in a 60℃ oven and dry for 6 hours. Take 20g of the dried leaching residue and mix it with 20g of sodium hydroxide. Place it in a muffle furnace and calcine for 4 hours at a calcine temperature of 650℃. Take 30g of the calcined mixture in a beaker, add 100mL of ultrapure water, and place the beaker in a magnetic stirrer and stir for 60min. During the stirring process, add a 15% phosphoric acid solution to the beaker to adjust the pH of the solution in the beaker to 8.5. Stop stirring to form a hydrogel. Place 100g of the hydrogel in 500ml of ultrapure water and age for 24 hours. Then place it in 500ml of anhydrous ethanol and age for 48 hours. Place the aged hydrogel in a 60℃ drying oven and dry to constant weight to obtain silica aerogel.

[0031] Step (5): Dilute the iron solution obtained in step (3) by 10 times, place 5g of the silica aerogel obtained in step (4) in 100ml of the diluted iron solution, stir at a constant speed under an inert gas atmosphere (nitrogen), add 150ml of the green reducing solution described in step (1) dropwise, react at 25℃ for 6h, centrifuge at high speed, freeze the obtained solid at -18℃ for 24h, and dry it in a freeze dryer at -60℃ for 24h to obtain supported nano-zero valent iron. The specific surface area of ​​the obtained supported nano-zero valent iron is 502m². 2 / g, the total iron content in the supported nano zero-valent iron is 98.2%.

[0032] Example 3 A method for preparing supported nano-zero-valent iron using Anshan-type iron tailings, specifically as follows: Step (1): Place 200g of coffee grounds A in a beaker, add 500mL of ultrapure water, seal and stir at 80℃ for 2h, cool to room temperature and then vacuum filter to obtain extract A. Place the separated coffee grounds in a 60℃ oven and dry at a constant temperature for 6h to obtain coffee grounds B. Add 300g of a mixture of orange peel, grapefruit peel and tangerine peel (mass ratio of orange peel, grapefruit peel and tangerine peel is 2:2:1) to extract A, seal and heat at 60℃ for 2h, then vacuum filter to obtain extract B. Place extract B in a rotary evaporator and rotary evaporate at 35℃ until the volume of extract B is concentrated to 100mL to obtain green reducing solution.

[0033] Step (2): Grind 50g of Anshan-type iron tailings to 200 mesh and place it in crucible A; place 100g of coffee grounds B from step (1) in crucible B; place crucible A and crucible B in parallel in a muffle furnace for roasting at 750℃ for 3.5h; after roasting, seal and cool to room temperature; remove the iron tailings from crucible A and grind them again to 200 mesh to obtain pretreated Anshan-type iron tailings.

[0034] Step (3): Take 40g of the pretreated Anshan-type iron tailings described in step (2) into a beaker, add 200mL of sulfuric acid solution with pH=0.6, seal the beaker and place it in a magnetic stirring water bath, heat to 35℃, stir for 24h, monitor the pH of the solution every 1h during the period, add 20% sulfuric acid dropwise to adjust the pH of the solution so that the pH value of the solution is always below 2.5; after the stirring is finished, vacuum filter the mixture in the beaker to obtain iron solution and leaching residue.

[0035] Step (4): Place the leaching residue obtained in step (3) in a 60℃ oven and dry for 8 hours. Take 20g of the dried leaching residue and mix it with 20g of sodium hydroxide. Place it in a muffle furnace and calcine for 4 hours at a calcine temperature of 800℃. Take 30g of the calcined mixture in a beaker, add 100mL of ultrapure water, and place the beaker in a magnetic stirrer and stir for 90min. During the stirring process, add a 20% phosphoric acid solution to the beaker to adjust the pH of the solution in the beaker to 8.0. Stop stirring to form a hydrogel. Place 100g of the hydrogel in 500ml of ultrapure water and age for 24 hours. Then place it in 500ml of anhydrous ethanol and age for 48 hours. Place the aged hydrogel in a 60℃ drying oven and dry to constant weight to obtain silica aerogel.

[0036] Step (5): Dilute the iron solution obtained in step (3) by 15 times, place 5g of the silica aerogel described in step (4) in 50ml of the diluted iron solution, stir at a constant speed under an inert gas atmosphere (nitrogen), add 100ml of the green reducing solution described in step (1) dropwise, react at 25℃ for 6h, centrifuge at high speed, freeze the obtained solid at -18℃ for 24h, and dry it in a freeze dryer at -60℃ for 24h to obtain supported nano-zero valent iron. The specific surface area of ​​the obtained supported nano-zero valent iron is 489m². 2 / g, the total iron content in the supported nano zero-valent iron is 99.3%.

[0037] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing supported nano-zero-valent iron using Anshan-type iron tailings, characterized in that, Includes the following steps: Step 1, Preparation of green reducing solution: Disperse coffee grounds A in water, seal and stir I, cool to room temperature and then vacuum filter to obtain extract A and coffee grounds B; add a mixture of orange peel, grapefruit peel and tangerine peel to extract A, seal and stir II, vacuum filter to obtain extract B, and concentrate by rotary evaporation to obtain green reducing solution; Step 2, Pretreatment of Anshan-type iron tailings: Place the ground Anshan-type iron tailings powder in crucible A, place the coffee grounds B obtained in step 1 in crucible B, and roast to obtain pretreated Anshan-type iron tailings. Step 3, Preparation of iron solution: The pretreated Anshan-type iron tailings obtained in Step 2 are placed in sulfuric acid solution I, sealed and stirred, sulfuric acid solution II is added dropwise to adjust the pH to below 2.5, and vacuum filtered to obtain iron solution and leaching residue; Step 4, Preparation of silica aerogel: The leaching residue obtained in step 3 is placed in an oven for drying, sodium hydroxide is added and then calcined, water is added and stirred, phosphoric acid solution is added to adjust the pH to 7.5~8.5 to form a hydrogel, aged and dried to obtain silica aerogel; Step 5, Preparation of supported nano-zero valent iron: Dilute the iron solution obtained in step 3, place the silica aerogel prepared in step 4 into the diluted iron solution, stir under an inert atmosphere, add the green reducing solution obtained in step 1 dropwise, after the reaction is complete, centrifuge, freeze, and dry to obtain supported nano-zero valent iron.

2. The method according to claim 1, characterized in that, In step 1, the mass-to-volume ratio of coffee grounds A to water is 200~400g:500~900ml; The conditions for sealed stirring I in step 1 are as follows: The temperature of the sealed stirring I is 80~100℃; The sealing and stirring time is 1-2 hours.

3. The method according to claim 1, characterized in that, In step 1, the mass ratio of orange peel, grapefruit peel, and tangerine peel in the mixture is 2:2:

1. The mass ratio of extract A to the mixture of orange peel, grapefruit peel and tangerine peel in step 1 is 5~10:1~3.

4. The method according to claim 1, characterized in that, The conditions for sealed stirring II in step 1 are as follows: The temperature of the sealed stirring II is 60~80℃; The time for the sealed stirring II is 1~2 hours; The moisture content of the coffee grounds A is 40-45%.

5. The method according to claim 1, characterized in that, The composition of the iron tailings from Anshan City mentioned in step 2 is as follows: 21.1%~32.8% Fe2O3, 62.5%~74.2% SiO2, 1.4%~1.8% Al2O3, 1.0%~1.1% CaO, 0.2%~0.4% K2O, 1.1%~1.3% MgO, and 0.75%~0.77% Na2O; The pretreatment of Anshan-type iron tailings in step 2 is as follows: grind the Anshan-type iron tailings to 200 mesh and place them in crucible A, place coffee grounds B in crucible B, place them parallel in a muffle furnace, roast at 700~900℃ for 3~5 hours, seal and cool to room temperature, grind the roasted Anshan-type iron tailings to 200 mesh again to obtain the pretreated Anshan-type iron tailings.

6. The method according to claim 1, characterized in that, The preparation of the iron solution in step 3 is as follows: 40-60g of pretreated Anshan-type iron tailings is placed in 200-500ml of sulfuric acid solution I with a pH of 0.6-1.0, and stirred in a sealed container at 35-38℃ for 6-24h. Every 1h, 20% sulfuric acid solution II is added dropwise to adjust the pH to below 2.

5. The mixture is then vacuum filtered to obtain the iron solution and leaching residue.

7. The method according to claim 1, characterized in that, The preparation of silica aerogel in step 4 is as follows: 20-40g of leaching residue is placed in an oven at 60℃ and dried for 6-12h. 20-40g of sodium hydroxide is added and calcined at 650-800℃ for 2-5h. 100-200ml of water is added and stirred for 30-90min. A 15%-25% phosphoric acid solution is added to adjust the pH to 7.5-8.5 to form a hydrogel. The hydrogel is aged in water and ethanol at room temperature for 36-48h and dried at 60℃ to constant weight to obtain silica aerogel.

8. The method according to claim 1, characterized in that, The preparation of the supported nano-zero valent iron in step 5 is as follows: the iron solution obtained in step 3 is diluted 10-20 times, the silica aerogel is placed in the diluted iron solution, stirred under an inert atmosphere, green reducing solution is added dropwise, and the reaction is carried out at 21-25℃ for 6-24h. After centrifugation, the mixture is frozen at -20--18℃ for 24-48h and dried in a freeze dryer at -60--50℃ for 24-48h to obtain the supported nano-zero valent iron. The mass-to-volume ratio of the silica aerogel, the diluted iron solution, and the green reducing solution is 1~1.2g:10~50ml:10~250ml, wherein the iron ion concentration in the diluted iron solution is 0.03~0.07mol / L.

9. The method according to claim 1, characterized in that, The specific surface area of ​​the supported nano-zero valent iron obtained in step 5 is 450~650 m². 2 / g, with an active iron content of 90.7~99.5%.