CN112661193B - Method for simultaneously preparing binary and ternary high-performance composite aerogel by using iron tailings - Google Patents

Abstract

The invention discloses a method for preparing binary and ternary high-performance composite aerogel by using iron tailings, which comprises the following steps: mixing iron tailings and sodium hydroxide, carrying out alkali fusion activation, cooling, washing with deionized water for solid-liquid separation, standing and layering washing liquor, separating supernatant from lower-layer mixed liquor, adding an acid catalyst under an alkaline condition, standing and aging to obtain wet gel, carrying out solvent replacement on the wet gel, and drying under normal pressure to obtain the binary and ternary composite aerogel. The invention takes the iron tailings as raw materials, has low price, wide sources, mild preparation conditions, simple process and low equipment requirement, is easy to realize industrialized preparation, and can simultaneously obtain binary and magnetic ternary composite silicon-based aerogel; the tap density of the prepared aerogel is less than 0.20g/cm³Wherein the specific surface areas of the binary aerogel and the ternary aerogel can reach 986m respectively²G and 612m²The adsorption capacity to methylene blue is more than 300 mg/g.

Description

Simultaneous preparation of binary and ternary high-performance composite aerogels from iron tailings

technical field

The invention relates to a method for simultaneously preparing binary and ternary composite aerogels by using iron tailings as raw materials, and belongs to the field of aerogel preparation.

Background technique

_SiO2 aerogel is a nanomaterial with a three-dimensional network porous structure composed of nano-scale silica particles, with high specific surface area, extremely low density, and low room temperature thermal conductivity. It has good application prospects in many fields such as thermal insulation, adsorption, CO ₂ isolation, catalyst carrier, aerospace and so on. The main preparation process of silica aerogel usually includes two typical steps of sol-gel and drying, which are respectively used to form and maximize the three-dimensional structure of the gel, so as to finally obtain aerogel products. Ethyl orthosilicate (TEOS) is a silicon source to obtain silica aerogel through supercritical drying, but there are still many challenges in technology and application, such as the high price of TEOS silicon source, and the strict requirements of supercritical drying equipment. Therefore, in order to overcome the above shortcomings, it is of great practical significance to find a cheaper silicon source and a simpler drying method.

Iron tailings are wastes after beneficiation and are the main component of industrial solid wastes. At present, the comprehensive utilization rate of tailings in my country is only 7%, and the stockpiled iron tailings amount to more than one billion tons, accounting for nearly 1/3 of the total tailings stockpiled. Therefore, the comprehensive recovery and utilization of iron tailings has been widely concerned by the whole society. Generally speaking, the content of silica, alumina, iron oxide, magnesium oxide and calcium oxide in iron tailings is the largest, and the rest are a small amount of associated element oxides. At present, the utilization of iron tailings is mainly in tailings recycling In terms of beneficiation, goaf filling in mining areas, tailings building materials, soil conditioners, etc., although these methods can solve some of the tailings stockpiling problems quantitatively, they are still related to more market-competitive high value-added products. It needs to be studied and promoted, which is not conducive to the efficient utilization of iron tailings. Silica in iron tailings is a natural source of silicon. After alkali treatment, it can be extracted as a raw material for the preparation of high value-added silica aerogels, which can improve the comprehensive utilization of iron tailings while achieving green ecological development. efficiency. At the same time, alumina and iron oxide in the tailings are also potential raw materials for the preparation of aerogels. Usually, the content of these valuable elements is relatively low, and separate purification or utilization involves complicated processes and high costs. Therefore, the present invention proposes to use them as necessary. The components remain in the aerogel and are compounded with silica to prepare a composite aerogel, which has the effect of synergistic gain functionalization. There are few reports on the preparation of aerogel by using silica in tailings. Publication No. CN108658130A discloses a method for simultaneously preparing iron oxide and silica aerogel from iron tailings. The method includes pickling Iron extraction and alkali melting extraction of silicon are used to obtain iron source and silicon source respectively, but the problem of combining the two to prepare composite materials is not solved; Publication No. CN109133072A discloses an ultra-fast preparation of hydrophobic silica using iron tailings as raw material The method of aerogel, publication number CN109012517A discloses a method for preparing composite silicon-based aerogel with iron tailings as raw material, although the above method obtains alumina and silica to a certain extent through the process of alkali melting However, due to the low initial alkali melting temperature, the iron oxide is still retained in the alkali slag, and the iron oxide in the tailings cannot be extracted to prepare the iron oxide/silica aerogel composite material.

SUMMARY OF THE INVENTION

In view of the technical problems existing in the prior art, the technical problem to be solved by the present invention is to provide a method for simultaneously preparing binary and ternary high-performance composite aerogels by using iron tailings, using solid waste iron tailings as raw materials , low price, wide source, mild preparation conditions, simple process, low equipment requirements, easy to realize industrial preparation, and can simultaneously obtain binary composite aerogel and ternary magnetic composite aerogel. The tap density of the prepared aerogel is less than 0.20g/ ^cm3 , and the average pore size is 5.25-8.67nm, and the specific surface area of the binary composite aerogel can reach ^986m2 /g, which can be used as an excellent carrier catalyst. The specific surface area of the magnetic composite aerogel can reach 600m ² /g, the adsorption capacity of methylene blue is more than 300mg/g, the adsorption performance is excellent and the separation is easy, both of which have good application potential.

In order to solve the above-mentioned technical problems, the technical scheme adopted in the present invention is:

The method for simultaneously preparing binary and ternary high-performance composite aerogels from iron tailings includes the following steps: (1) using iron tailings as raw materials, uniformly mixing with powdered sodium hydroxide, and placing them in a muffle furnace , cooling to room temperature after the heating and heat preservation reaction is completed, the obtained mixture is rinsed with deionized water for 4-10 times and the washing liquid is collected; (2) the washing liquid obtained in step (1) is placed in a container and allowed to stand for 10-60 until the washing liquid is clearly stratified, suck out the supernatant liquid with a pipette, add an acidic catalyst to the upper supernatant liquid and the mixed liquid of the lower layer respectively, and adjust the pH of the washing liquid to 9-10.5 respectively, and let stand until the massive gel is formed. The gels are respectively taken out and placed in deionized water to continue aging for 12-24 hours to obtain wet gels, and the deionized water is replaced 3-6 times during the aging process; (3) the wet gels obtained in step (2) are placed in replacement Perform solvent replacement in the solvent solution for 12-24 hours, and replace the fresh replacement agent solution every 2-6 hours to completely remove water and other residual reagents in the wet gel; (4) Replace the solvent replacement in step (3) with the The wet gels are respectively taken out and dried under normal pressure to obtain the binary composite aerogel and the ternary magnetic composite aerogel.

Iron tailings are in powder form with a particle size of more than 50 mesh, and contain silicon dioxide, aluminum oxide, iron oxide, magnesium oxide, calcium oxide, potassium oxide and sodium oxide.

In step (1), the mass ratio of iron tailings and sodium hydroxide is 1:1-3, and the water consumption of each rinse of the mixture after cooling is 1:20-100 (grams) for the ratio of the mass of the mixture to the volume of water. /ml), the operating temperature is room temperature.

In step (1), the heating temperature is 700-900° C., and the holding time is 1-5 hours.

In step (2), the acid catalyst used is that the supernatant liquid selects phosphoric acid, nitric acid, hydrochloric acid, sulfuric acid or citric acid solution catalytic gel, the mass fraction of the acid solution used is 2-15%, and the lower layer mixed solution selects phosphoric acid, nitric acid, Hydrochloric acid, sulfuric acid or citric acid solution is combined with pure tartaric acid or pure ascorbic acid to catalyze the gel, the mass fraction of the acid solution used is 2-15%, and the mass ratio of tartaric acid, ascorbic acid and other acids is 1:1-1:5.

In step (3), the used displacer is one or more selected from ethanol, tert-butanol, acetone, methanol, and ethylene glycol, and the dosage for each time is to at least completely immerse the wet gel.

The method of atmospheric drying in step (3) is to put the wet gel in an open container, seal it with a plastic wrap, and open 5-30 holes on the plastic wrap, and the hole size is 1×1 mm, so as to control the humidity during the drying process. The drying rate of the gel can reduce the collapse of the gel skeleton. Finally, the container is placed in an oven and dried at 50-150 ° C for 24-72 hours until the wet gel is completely dry.

The tap density of the binary composite aerogel and the ternary magnetic composite aerogel obtained in step (4) is 0.158-0.194 g/cm ³ , the specific surface area is 320-986 m ² /g, and the average pore size is 5.25-8.67 nm, the adsorption capacity of the two for the typical dye methylene blue can reach 322 mg/g and 354 mg/g, respectively.

The beneficial effects of the present invention are:

1. The present invention only uses iron tailings as raw materials, has the advantages of wide source, low price, green environmental protection and non-toxicity, meets the development requirements of national energy conservation and emission reduction, and simultaneously utilizes the own iron oxide and alumina in iron tailings. The preparation of composite materials is realized, and silicon-aluminum and silicon-aluminum-iron composite aerogels with high specific surface area and high adsorption performance are obtained, which effectively improves the functionality and added value of the product.

2. The present invention effectively converts iron oxide in iron tailings to ferrite through high-temperature alkali melting treatment, and realizes the conversion of insoluble iron to soluble iron. , solvent replacement and drying at atmospheric pressure to obtain Al-Si binary composite aerogel and Al-Si-Fe ternary magnetic composite aerogel in one step. At the same time, silica aerogel is synergistically enhanced by alumina and iron oxide. The silicon-alumina binary composite aerogel has a well-developed pore structure, the specific surface area can reach 986m ² /g, and the adsorption capacity of methylene blue exceeds 300mg/g. It can also exceed 600m ² /g. The catalytic oxidation of iron oxide makes its adsorption capacity for methylene blue close to or even higher than that of silicon-aluminum binary composite aerogel, exceeding 350mg/g, showing excellent adsorption potential. The gelation process and the reduction effect of organic acids, the iron oxide in the ternary magnetic composite aerogel is magnetic, mainly exists in the form of magnetic γ iron oxide, without the need to add additional magnetic substances, one-step realization of the magnetic functionalization of the iron source in the tailings , making the ternary magnetic composite aerogel material easier to separate.

3. The process used in the present invention requires no additional silicon source, no ion exchange, no surface modification, no supercritical drying, and no magnetic additives. Only the effective components in the iron tailings are used to achieve self-composite reinforcement of aerogels, and the preparation conditions are simple. Mild, low equipment requirements, low energy consumption, energy saving and environmental protection, it also puts forward new ideas for the utilization of solid waste resources, and is easy to industrialize production.

Description of drawings

Fig. 1 is the process flow diagram of the present invention;

Fig. 2 is embodiment 3 lotion standing and layering effect diagram;

Fig. 3 is embodiment 3 ternary magnetic composite aerogel (left) and binary composite aerogel physical map;

Fig. 4 is the magnetic display diagram of embodiment 3 ternary magnetic composite aerogel;

5 is a SEM-EDS image of the composite aerogel of Example 3;

Fig. 6 is embodiment 3 composite aerogel XRD pattern;

7 is the nitrogen adsorption isotherm of the composite aerogel of Example 3.

Detailed ways

The technical solutions of the present invention are further described below through specific embodiments. It should be understood by those skilled in the art that the embodiments are only for helping the understanding of the present invention, and should not be regarded as a specific limitation of the present invention.

Example 1

A method for simultaneously preparing binary and ternary high-performance composite aerogels by utilizing iron tailings, the specific preparation steps are as follows: (1) powdered iron tailings with a size of more than 50 meshes and powdered sodium hydroxide in a mass ratio of 1 : 1 Put it into the crucible and mix it evenly, put the crucible into the muffle furnace, set the heating rate of the muffle furnace to be 5 ℃/min, heat it to 700 ℃ and keep it for 4 hours to obtain the iron tailings and sodium hydroxide after the reaction. The mixture was washed four times with deionized water at a solid mass to liquid volume ratio of 1:20 to obtain a washing solution.

(2) After standing for 30 minutes, the lotion was obviously stratified, and the supernatant was drawn into other glass containers. Add 5% hydrochloric acid + ascorbic acid (mass ratio 2:1) into two containers respectively, adjust the liquid in the container to pH=9.1, and let the liquid in the two containers stand until a bulk gel is formed.

(3) The two bulk gels were taken out and immersed in deionized water respectively and aged at room temperature for 16 hours to obtain wet gels, during which the deionized water was replaced 3 times.

(4) The aged wet gel was taken out and immersed in 90 mL of ethanol solvent for 20 hours, during which the solvent was replaced three times to completely remove water and residual reagents in the pores of the wet gel.

(5) Remove the wet gel from the replacement solvent and place it in a 500ml beaker, seal the mouth of the container with plastic wrap and tie 4 small holes in the plastic wrap, and wet the gel obtained from the supernatant under normal pressure. The gel is dried at 85° C. and kept for 36 hours, and the wet gel obtained from the lower mixed solution is kept at 110° C. for 36 hours to dry, and the binary composite aerogel and the ternary magnetic composite aerogel can be obtained.

Example 2

A method for simultaneously preparing binary and ternary high-performance composite aerogels by utilizing iron tailings, the specific preparation steps are as follows: (1) powdered iron tailings with a size of more than 50 meshes and powdered sodium hydroxide in a mass ratio of 1 : 2 Put it into the crucible and mix it evenly, put the crucible into the muffle furnace, set the heating rate of the muffle furnace to be 5 ℃/min, heat to 780 ℃ and keep the temperature for 3.5 hours to obtain the iron tailings and sodium hydroxide after the reaction. The mixture was washed 6 times with deionized water at a solid mass to liquid volume ratio of 1:30 to obtain a washing solution.

(2) After standing for 40 minutes, the lotion is obviously stratified, and the supernatant is drawn into other glass containers. The mass fraction of 5% sulfuric acid + ascorbic acid (mass ratio 2:1) was added to the two containers respectively to adjust the liquid in the container to pH=9.3, and the liquid in the two containers was allowed to stand until a bulk gel was formed.

(3) The two bulk gels were taken out and immersed in deionized water respectively and aged at room temperature for 20 hours to obtain wet gels, during which the deionized water was replaced 4 times.

(4) The aged wet gel was taken out and immersed in 100 mL of methanol solvent for 22 hours, during which the solvent was replaced 5 times to completely remove water and residual reagents in the pores of the wet gel.

(5) Remove the wet gel from the replacement solvent and place it in a 500ml beaker, seal the mouth of the beaker with plastic wrap and poke 8 small holes on the plastic wrap, and wet the gel obtained from the supernatant under normal pressure. The gel is kept dry at 80° C. for 48 hours, and the wet gel obtained from the lower mixed solution is kept at 120° C. for 48 hours to dry, and the binary composite aerogel and the ternary magnetic composite aerogel can be obtained.

Example 3

A method for simultaneously preparing binary and ternary high-performance composite aerogels by utilizing iron tailings, the specific preparation steps are as follows: (1) powdered iron tailings with a size of more than 50 meshes and powdered sodium hydroxide in a mass ratio of 1 : 2.5 Put it into the crucible and mix it evenly, put the crucible into the muffle furnace, set the heating rate of the muffle furnace to be 5 ℃/min, heat it to 850 ℃ and keep it for 3 hours to obtain the iron tailings and sodium hydroxide after the reaction. The mixture was washed 8 times with deionized water at a solid mass to liquid volume ratio of 1:40 to obtain a washing solution.

(2) After standing for 50 minutes, the washing liquid is obviously layered, and the supernatant liquid is drawn into other glass containers, and phosphoric acid + tartaric acid (mass ratio 3:1) with a mass fraction of 10% is added to the two containers respectively. Medium liquid pH = 9.7, and the liquids in both containers were allowed to stand until the distribution formed a bulk gel.

(3) The two bulk gels were taken out and immersed in deionized water respectively and aged at room temperature for 18 hours to obtain wet gels, during which the deionized water was replaced 5 times.

(4) The aged wet gel was taken out and immersed in 120 mL of ethylene glycol solvent for 24 hours, during which the solvent was replaced 7 times to completely remove water and residual reagents in the pores of the wet gel.

(5) Take out the wet gel from the replacement solvent and place it in a 500ml beaker, seal the mouth of the beaker with plastic wrap and tie 12 small holes in the plastic wrap, and wet the gel obtained from the supernatant under normal pressure. The gel is dried at 75° C. and kept for 60 hours, and the wet gel obtained from the lower mixed solution is kept at 120° C. for 60 hours to dry, and the binary composite aerogel and the ternary magnetic composite aerogel can be obtained.

Example 4

A method for simultaneously preparing binary and ternary high-performance composite aerogels by utilizing iron tailings, the specific preparation steps are as follows: (1) powdered iron tailings with a size of more than 50 meshes and powdered sodium hydroxide in a mass ratio of 1 : 3 put it into the crucible and mix it evenly, put the crucible into the muffle furnace, set the heating rate of the muffle furnace to be 5 ℃/min, heat it to 900 ℃ and keep it for 2.5 hours to obtain the iron tailings and sodium hydroxide after the reaction. The mixture is washed 8 times with deionized water at a solid mass to liquid volume ratio of 1:50 to obtain a washing solution.

(2) After standing for 58 minutes, the lotion was obviously stratified, and the supernatant was drawn into other glass containers. Add 15% citric acid + tartaric acid (mass ratio 3:1) into two containers respectively to adjust the pH of the liquid in the container to 10.2, and leave the liquid in the two containers to stand until the distribution forms a bulk gel.

(3) The two bulk gels were taken out and immersed in deionized water respectively and aged at room temperature for 15 hours to obtain wet gels, during which the deionized water was replaced 7 times.

(4) The aged wet gel was taken out and immersed in 140 mL of tert-butanol solvent for 21 hours, during which the solvent was replaced 6 times to completely remove water and residual reagents in the pores of the wet gel.

(5) Take out the wet gel from the replacement solvent and place 500 ml in a beaker, seal the mouth of the beaker with plastic wrap and tie 18 small holes in the plastic wrap, and then wet the gel obtained from the supernatant under normal pressure. The gel is dried at 70° C. and kept for 72 hours, and the wet gel obtained from the lower mixed solution is kept at 130° C. for 72 hours to dry, and the binary composite aerogel and the ternary magnetic composite aerogel can be obtained.

Table 1

From Table 1, it can be concluded that the specific surface area of the product varies greatly according to the different types of acid catalysts actually used. This is because the concentration and type of acid have certain effects on the formation of binary composite aerogels and ternary magnetic composite aerogels. Under the catalysis of medium and strong acid, the skeleton structure of the colloid is relatively complete. In the drying process, the displacer with small surface tension will not cause a large skeleton to collapse, so as to maintain good pore structure. For the ternary magnetic composite aerogel, the presence of iron will make the colloid affected by the doping of iron oxide during the formation process, resulting in a decrease in the specific surface area of the final aerogel product, but the excellent catalytic oxidation effect of iron oxide It can significantly improve the adsorption and purification effect of ternary aerogel on methylene blue dye, so that the ternary aerogel still has a high adsorption capacity of methylene blue in the case of low specific surface area, and it is magnetic and easy to separate. It is difficult to generate under the conditions, so it is very necessary to increase the alkali melting temperature to above 700 °C and appropriately increase the NaOH ratio in the alkali melting stage.

Claims (6)

1. The method for simultaneously preparing the binary and ternary high-performance composite aerogel by using the iron tailings is characterized by comprising the following steps of: (1) uniformly mixing iron tailings serving as a raw material with powder sodium hydroxide, placing the mixture in a muffle furnace, heating, preserving heat, reacting completely, cooling to room temperature, heating at the temperature of 700-900 ℃, preserving heat for 1-5 hours, washing the obtained mixture for 4-10 times with deionized water, and collecting washing liquid; (2) placing the washing liquid obtained in the step (1) in a container, standing for 10-60 minutes until the washing liquid is obviously layered, sucking out the supernatant liquid by using a suction pipe, respectively adding an acidic catalyst into the supernatant liquid and the lower layer mixed liquid, respectively adjusting the pH value to 9-10.5, standing until block-shaped gel is formed, respectively taking out the gel, placing the gel in deionized water, continuously aging for 12-24 hours to obtain wet gel, and replacing the deionized water for 3-6 times in the aging process; (3) respectively placing the wet gel obtained in the step (2) in a displacer solution for 12-24 hours to perform solvent displacement, and replacing fresh displacer solution every 2-6 hours to completely remove water and other residual reagents in the wet gel; (4) and (4) respectively taking out the wet gel after the solvent replacement in the step (3), and drying at normal pressure to obtain the binary composite aerogel and the ternary magnetic composite aerogel.

2. The method for preparing binary and ternary high performance composite aerogels according to claim 1, characterized in that: the iron tailings are powder and contain silicon dioxide, aluminum oxide, iron oxide, magnesium oxide, calcium oxide, potassium oxide and sodium oxide.

3. The method for preparing binary and ternary high performance composite aerogels according to claim 1, characterized in that: in the step (1), the mass ratio of the iron tailings to the sodium hydroxide is 1:1-3, the water consumption for flushing the cooled mixture each time is 1 g: 20-100 ml, and the operation temperature is room temperature.

4. The method for preparing binary and ternary high performance composite aerogels according to claim 1, characterized in that: in the step (2), the used acidic catalyst is a gel catalyzed by phosphoric acid, nitric acid, hydrochloric acid, sulfuric acid or citric acid solution selected from the supernatant, the mass fraction of the used acid solution is 2-15%, the mixed solution of the lower layer is a gel catalyzed by phosphoric acid, nitric acid, hydrochloric acid, sulfuric acid or citric acid solution matched with pure tartaric acid or pure ascorbic acid, the mass fraction of the used acid solution is 2-15%, and the mass ratio of tartaric acid, ascorbic acid and other acids is 1: 1-1: 5.

5. the method for preparing binary and ternary high performance composite aerogels according to claim 1, characterized in that: in the step (3), the used displacer is one or more of ethanol, tertiary butanol, acetone, methanol and glycol, and the dosage of each time is that the wet gel is at least completely immersed.

6. The method for preparing binary and ternary high performance composite aerogels according to claim 1, characterized in that: the normal pressure drying method in the step (3) is to put the wet gel into an open container, seal the container by using a preservative film, open 5-30 holes with the size of 1x1mm on the preservative film so as to regulate and control the drying rate of the wet gel in the drying process and reduce the collapse of a gel framework, and finally place the container in an oven to be dried for 24-72 hours at the temperature of 50-150 ℃ until the wet gel is completely dried.

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