Preparation method and application of zeolite-carbon composite material

Abstract

The invention relates to a preparation method of a zeolite-carbon composite material. The preparation method comprises the following steps: 1) pretreating fly ash; 2) mixing the pretreated fly ash and solid alkali according to a mass ratio of 1: (0.2-5), calcining at a high temperature of 900 DEG C for 1-12 hours, cooling, crushing and sieving to obtain a zeolite precursor; (3) mixing the biochar and the zeolite precursor according to the mass ratio of 0.02-0.1, adding alkali liquor, uniformly stirring, and reacting for 0.5-5 hours at the temperature of 30-60 DEG C to obtain a mixture; and 4) putting the mixture obtained in the step 3) into a reaction kettle, heating for 12-36 hours at 70-100 DEG C, carrying out hydrothermal reaction, washing the product to be neutral after the reaction is ended, and drying to obtain the zeolite-carbon composite material.The zeolite-carbon composite material has an obvious remediation effect on underground water polluted by high-concentration ammonia nitrogen, petroleum and derivatives thereof at the periphery of a landfill.

Description

Technical Field

[0001] The invention belongs to the technical field of restoration of groundwater contaminated sites, and specifically relates to the preparation and application of a zeolite-carbon composite material. Background Art

[0002] With the rapid development of the petrochemical industry at home and abroad, the discharge of solid wastes such as alkaline wet oxidation slag has been increasing. For these slags, the current mainstream treatment method is direct landfill. The petrochemical solid slag waste buried underground will cause shallow groundwater pollution problems to varying degrees, mainly ammonia nitrogen and petroleum and its derivatives. In order to prevent the landfill slag from polluting shallow groundwater, it is usually necessary to set up an impermeable layer in the landfill. However, with the increase in landfill volume and landfill time, the impermeable effect of the impermeable layer gradually deteriorates, causing the leakage of harmful leachate and the spread of pollutants, thus posing a serious threat to the groundwater in the landfill and its surrounding areas. For the leachate generated by the landfill, reverse osmosis, catalytic oxidation, biological methods and other methods are generally used for treatment. These treatment methods require a lot of cost and time, and often bring secondary pollution. The low temperature, high salt, and high concentration of ammonia nitrogen in the groundwater of the landfill also restrict the use of many conventional treatment processes.

[0003] At present, the groundwater ammonia nitrogen treatment processes that are widely studied and applied mainly include adsorption, ion exchange, biological denitrification, etc. The treatment processes for petroleum derivative pollutants mainly include adsorption, microbial method and ozone oxidation, etc. The adsorption method is simple and easy to recycle. The commonly used ammonia nitrogen adsorption materials at home and abroad are mainly bentonite, limestone, zeolite, etc., among which zeolite is the most common adsorption material. Zeolite has the characteristics of high porosity and large specific surface area, and has strong selective adsorption and exchange capacity for ammonia nitrogen.

[0004] CN108786722A discloses a composite adsorption material and a preparation method thereof. The composite material comprises 5%-50% coal fly ash, 10%-50% activated carbon and 5%-60% nano-analcite. The specific surface area of ​​the prepared composite adsorption material is 300-1500m 2 / g, pore volume is 0.3-1.5cm 3 / g, the pore size increases from small to large and the distribution is diversified. This composite adsorbent material can effectively adsorb and remove a wide variety of organic and inorganic pollutants with different properties in industrial wastewater.

[0005] CN108786721A discloses a composite adsorption material and a preparation method thereof, which comprises 5%-50% coal fly ash, 10%-50% activated carbon and 10%-60% eutectic of analcime and mordenite, based on the weight of the composite adsorption material. The fly ash and the eutectic are connected to each other by activated carbon. The specific surface area of ​​the composite adsorption material is 300-1800m 2 / g, preferably 800-1600m 2 / g, pore volume is 0.3-1.5cm 3 / g. This composite adsorption material has micropores, mesopores and macropores, and can adsorb a wide range of organic pollutants and heavy metal ions in wastewater. Summary of the invention

[0006] In order to efficiently and cost-effectively treat the groundwater contaminated by the seepage water in the landfill, the present invention discloses a zeolite-carbon composite material, the equilibrium adsorption capacity of the composite material for ammonia nitrogen and petroleum and its derivatives can reach 24.23 mg / g and 254.92 mg / g, and the groundwater contaminated by ammonia nitrogen and petroleum can be dynamically repaired for a long time and efficiently, and the removal rate of ammonia nitrogen can reach more than 90% when finally applied to simulate the contaminated groundwater in the landfill. The petroleum and its derivatives described in the present invention are hydrocarbons contained in petroleum, and organic compounds such as carboxylic acids, heterocyclic compounds, ethers, esters, alcohols, aldehydes, ketones, etc. produced in the production and discharge process of petrochemical industry.

[0007] A method for preparing a zeolite-carbon composite material comprises the following steps: 1) Pretreatment of fly ash; 2) The pretreated fly ash is mixed with solid alkali in a mass ratio of 1:0.2-5, calcined at 900°C for 1-12h, and then crushed and sieved after cooling to obtain a zeolite precursor; 3) Mix the biochar and the zeolite precursor in a mass ratio of 0.02-0.1, add alkali solution, stir evenly, react at 30-60°C for 0.5-5h to obtain a mixture; 4) The mixture obtained in step 3) is placed in a reactor and heated at 70-100° C. for 12-36 hours for hydrothermal reaction. After the reaction is completed, the product is washed with water until neutral and dried to obtain a zeolite-carbon composite material.

[0008] The pretreatment in step 1) includes crushing, screening, washing and drying. The screening is to control the particle size of fly ash below 200 mesh; the washing is to wash with water for 1-5 times; and the drying is maintained at 90-110° C. for 12-24 hours.

[0009] In step 2), the solid alkali is one or more of sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate; preferably sodium carbonate or sodium bicarbonate, and the mass ratio of the pretreated fly ash to the solid alkali is 1:0.5-2; the calcination is carried out under closed conditions; the high-temperature calcination adopts programmed stage heating, and the heating time is 120-240min.

[0010] Step 3) The raw material of the biochar is one of crop straw, tree branches and leaves, wood, corn cobs, etc. The raw material of the biochar is calcined at 500-900°C for 1-12h, taken out, acid-washed, washed with water to neutrality and dried at a temperature of 100-120°C to obtain the biochar.

[0011] The mixing in step 3) is carried out under stirring, preferably under ultrasonic stirring.

[0012] The alkali solution in step 3) is one of sodium hydroxide and potassium hydroxide, and its concentration is 1-5 mol / L; preferably, the mass ratio of biochar to zeolite precursor is 0.02-0.07, and most preferably 0.04-0.05, and the alkali solution concentration is 2-3 mol / L.

[0013] After the hydrothermal reaction in step 4) is completed, the sample is washed with water for 5-10 times until it becomes neutral, and dried at 100-110°C for later use.

[0014] As one aspect of the present invention, it relates to a zeolite-carbon composite material prepared by the method.

[0015] As one aspect of the present invention, it relates to the application of a zeolite-carbon composite material in groundwater polluted by high concentration of ammonia nitrogen and petroleum and its derivatives.

[0016] The ammonia nitrogen concentration of the groundwater contaminated by high concentration ammonia nitrogen is greater than 500 mg·L -1 , more preferably greater than 1400 mg·L -1 ; Petroleum and its derivatives concentration greater than 500 mg·L -1 , more preferably greater than 1000 mg·L -1 The salt concentration of the groundwater contaminated with high concentrations of ammonia nitrogen is 1-2wt%, more preferably 1.5-2wt%; the temperature of the groundwater contaminated with high concentrations of ammonia nitrogen is 0-25°C, more preferably 5-15°C.

[0017] As another aspect of the present invention, it relates to a method for treating contaminated groundwater around a landfill, using the above-mentioned zeolite-carbon composite material.

[0018] The mineral crystal phase of the zeolite-carbon composite material gradually changes from a metastable phase to a stable phase, the pore structure is irregular, the flake particles accumulate to form slit pores, and there is a mesopore capillary condensation phenomenon. NH4 + The optimal adsorption pore size is in the range of 0-5nm, and the zeolite-carbon composite material has a large number of micropores in this range, which is more conducive to the adsorption of NH4 + The biochar attached to the surface is conducive to the adsorption of petroleum and its derivatives. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the SEM image of fly ash; Figure 2 This is the SEM image of the zeolite carbon composite material. DETAILED DESCRIPTION

[0020] The technical solution and application of the present invention will be clearly and completely described below through embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0021] Example 1 The preparation method of zeolite carbon composite material comprises the following steps: 1) pre-treating fly ash, wherein the pre-treatment comprises crushing, screening, washing and drying, wherein the screening is to control the particle size of fly ash to be below 200 mesh; the washing is to wash with water for 5 times; and the drying is to maintain at 90°C for 24 hours; 2) the pre-treated fly ash is evenly mixed with Na2CO3 in a ratio of 1:1 and then put into a 150mL crucible, and then put into a muffle furnace, and calcine at a high temperature of 900°C for 2 hours, and then after heating, continuous heating and cooling to room temperature, the mixture is mixed with Na2CO3 in a ratio of 1:1 and then put into a 150mL crucible, and then put into a muffle furnace, and calcine at a high temperature of 900°C for 2 hours. After that, the alkali-melted block fly ash is put into a crusher to break it up and sieve it to obtain a granular zeolite precursor; 3) The pre-prepared corn straw biochar is mixed with the zeolite precursor, a certain amount of deionized water and NaOH are added, and stirred evenly; ultrasonic treatment is performed at 45°C for a certain time; the ratio of biochar to zeolite addition is 0.02; the NaOH concentration is 2moL / L; 4) After the ultrasonic treatment, the prepared sample is poured into a polytetrafluoroethylene liner, placed in a reactor, and heated at 90°C for 24h for hydrothermal reaction. After the reaction, the sample is taken out, washed with water until neutral, and dried at 105°C for standby use to obtain a zeolite-carbon composite material.

[0022] Example 2 The preparation method of zeolite carbon composite material comprises the following steps: 1) pre-treating fly ash, wherein the pre-treatment comprises crushing, screening, washing and drying, wherein the screening is to control the particle size of fly ash to be below 200 mesh; the washing is to wash with water for 5 times; and the drying is to be maintained at 90°C for 24 hours; 2) the pre-treated fly ash is mixed with Na2CO3 in a ratio of 1:1 and then put into a 150mL crucible, and then put into a muffle furnace, and calcined at a high temperature of 900°C for 2 hours, and after heating, continuous heating and cooling to room temperature, , put the alkali-melted block fly ash into a crusher, crush it, and sieve it to obtain a granular zeolite precursor; 3) Mix the pre-prepared corn straw biochar with the zeolite precursor, add a certain amount of deionized water and NaOH, and stir evenly; ultrasonicate at 45℃ for a certain time; the ratio of biochar to zeolite is 0.045; the NaOH concentration is 2moL / L; 4) After the ultrasonication, pour the prepared sample into a polytetrafluoroethylene liner, put it into a reactor, and heat it at 90℃ for 24h for hydrothermal reaction. After the reaction, take out the sample, wash it with water until it is neutral, and dry it at 105℃ for standby use to obtain a zeolite-carbon composite material.

[0023] Example 3 The preparation method of zeolite carbon composite material comprises the following steps: 1) pre-treating fly ash, wherein the pre-treatment comprises crushing, screening, washing and drying, wherein the screening is to control the particle size of fly ash to be below 200 mesh; the washing is to wash with water for 5 times; and the drying is to maintain at 90°C for 24 hours; 2) the pre-treated fly ash is evenly mixed with Na2CO3 in a ratio of 1:1 and then put into a 150mL crucible, and then put into a muffle furnace, and calcine at a high temperature of 900°C for 2 hours, and then after heating, continuous heating and cooling to room temperature, the mixture is mixed with Na2CO3 in a ratio of 1:1 and then put into a 150mL crucible, and then put into a muffle furnace, and calcine at a high temperature of 900°C for 2 hours. After that, the alkali-melted block fly ash is put into a pulverizer to break it up and sieve it to obtain a granular zeolite precursor; 3) The pre-prepared corn straw biochar is mixed with the zeolite precursor, a certain amount of deionized water and NaOH are added, and stirred evenly; ultrasonic treatment is performed at 45°C for a certain time; the biochar to zeolite addition ratio is 0.07; the NaOH concentration is 2moL / L; 4) After the ultrasonic treatment, the prepared sample is poured into a polytetrafluoroethylene liner, placed in a reactor, and heated at 90°C for 24h for hydrothermal reaction. After the reaction, the sample is taken out, washed with water until neutral, and dried at 105°C for standby use to obtain a zeolite-carbon composite material.

[0024] Example 4 The preparation method of zeolite carbon composite material comprises the following steps: 1) pre-treating fly ash, wherein the pre-treatment comprises crushing, screening, washing and drying, wherein the screening is to control the particle size of fly ash to be below 200 mesh; the washing is to wash with water for 5 times; and the drying is to be maintained at 90°C for 24 hours; 2) the pre-treated fly ash is mixed with Na2CO3 in a ratio of 1:1 and then put into a 150mL crucible, and then put into a muffle furnace, and calcined at a high temperature of 900°C for 2 hours, and after heating, continuous heating and cooling to room temperature, , put the alkali-melted block fly ash into a crusher and crush it, sieve it, and get the granular zeolite precursor; 3) mix the pre-prepared corn straw biochar with the zeolite precursor, add a certain amount of deionized water and NaOH, stir evenly; ultrasonicate at 45℃ for a certain time; the ratio of biochar to zeolite is 0.02; the NaOH concentration is 2.5moL / L; 4) after the ultrasonication, pour the prepared sample into a polytetrafluoroethylene liner, put it into a reactor, and heat it at 90℃ for 24h for hydrothermal reaction. After the reaction, take out the sample, wash it with water until it is neutral, and dry it at 105℃ for standby to get the zeolite-carbon composite material.

[0025] Example 5 The preparation method of zeolite carbon composite material comprises the following steps: 1) pre-treating fly ash, wherein the pre-treatment comprises crushing, screening, washing and drying, wherein the screening is to control the particle size of fly ash to be below 200 mesh; the washing is to wash with water for 5 times; and the drying is to be kept at 90°C for 24 hours; 2) the pre-treated fly ash is mixed with Na2CO3 in a ratio of 1:1 and then put into a 150mL crucible, and then put into a muffle furnace, and calcined at a high temperature of 900°C for 2 hours. After heating, continuous heating and cooling to room temperature, Put the alkali-melted block fly ash into a crusher and crush it, sieve it, and get the granular zeolite precursor; 3) Mix the pre-prepared corn straw biochar with the zeolite precursor, add a certain amount of deionized water and NaOH, stir evenly; ultrasonicate at 45℃ for a certain time; the ratio of biochar to zeolite is 0.045; the NaOH concentration is 2.5moL / L; 4) After the ultrasonication, pour the prepared sample into a polytetrafluoroethylene liner, put it into a reactor, and heat it at 90℃ for 24h for hydrothermal reaction. After the reaction, take out the sample, wash it with water until it is neutral, and dry it at 105℃ for use to get the zeolite-carbon composite material.

[0026] Example 6 The preparation method of zeolite carbon composite material comprises the following steps: 1) pre-treating fly ash, wherein the pre-treatment comprises crushing, screening, washing and drying, wherein the screening is to control the particle size of fly ash to be below 200 mesh; the washing is to wash with water for 5 times; and the drying is to be maintained at 90°C for 24 hours; 2) the pre-treated fly ash is mixed with Na2CO3 in a ratio of 1:1 and then put into a 150mL crucible, and then put into a muffle furnace, and calcined at a high temperature of 900°C for 2 hours, and after heating, continuous heating and cooling to room temperature, , put the alkali-melted block fly ash into a crusher, crush it, and sieve it to obtain a granular zeolite precursor; 3) Mix the pre-prepared corn straw biochar with the zeolite precursor, add a certain amount of deionized water and NaOH, and stir evenly; ultrasonicate at 45℃ for a certain time; the ratio of biochar to zeolite is 0.07; the NaOH concentration is 2.5moL / L; 4) After the ultrasonication, pour the prepared sample into a polytetrafluoroethylene liner, put it into a reactor, and heat it at 90℃ for 24h for hydrothermal reaction. After the reaction, take out the sample, wash it with water until it is neutral, and dry it at 105℃ for standby use to obtain a zeolite-carbon composite material.

[0027] Example 7 The preparation method of zeolite carbon composite material comprises the following steps: 1) pre-treating fly ash, wherein the pre-treatment comprises crushing, screening, washing and drying, wherein the screening is to control the particle size of fly ash to be below 200 mesh; the washing is to wash with water for 5 times; and the drying is to maintain at 90°C for 24 hours; 2) the pre-treated fly ash is evenly mixed with Na2CO3 in a ratio of 1:1 and then put into a 150mL crucible, and then put into a muffle furnace, and calcine at a high temperature of 900°C for 2 hours, and then after heating, continuous heating and cooling to room temperature, the mixture is mixed with Na2CO3 in a ratio of 1:1 and then put into a 150mL crucible, and then put into a muffle furnace, and calcine at a high temperature of 900°C for 2 hours. After that, the alkali-melted block fly ash is put into a crusher to break it up and sieve it to obtain a granular zeolite precursor; 3) The pre-prepared corn straw biochar is mixed with the zeolite precursor, a certain amount of deionized water and NaOH are added, and stirred evenly; ultrasonic treatment is performed at 45°C for a certain time; the ratio of biochar to zeolite addition is 0.02; the NaOH concentration is 3moL / L; 4) After the ultrasonic treatment, the prepared sample is poured into a polytetrafluoroethylene liner, placed in a reactor, and heated at 90°C for 24h for hydrothermal reaction. After the reaction, the sample is taken out, washed with water until neutral, and dried at 105°C for standby use to obtain a zeolite-carbon composite material.

[0028] Example 8 The preparation method of zeolite carbon composite material comprises the following steps: 1) pre-treating fly ash, wherein the pre-treatment comprises crushing, screening, washing and drying, wherein the screening is to control the particle size of fly ash to be below 200 mesh; the washing is to wash with water for 5 times; and the drying is to be maintained at 90°C for 24 hours; 2) the pre-treated fly ash is mixed with Na2CO3 in a ratio of 1:1 and then put into a 150mL crucible, and then put into a muffle furnace, and calcined at a high temperature of 900°C for 2 hours, and after heating, continuous heating and cooling to room temperature, , put the alkali-melted block fly ash into a crusher, crush it, and sieve it to obtain a granular zeolite precursor; 3) Mix the pre-prepared corn straw biochar with the zeolite precursor, add a certain amount of deionized water and NaOH, and stir evenly; ultrasonicate at 45℃ for a certain time; the ratio of biochar to zeolite is 0.045; the NaOH concentration is 3moL / L; 4) After the ultrasonication, pour the prepared sample into a polytetrafluoroethylene liner, put it into a reactor, and heat it at 90℃ for 24h for hydrothermal reaction. After the reaction, take out the sample, wash it with water until it is neutral, and dry it at 105℃ for use to obtain a zeolite-carbon composite material.

[0029] Example 9 The preparation method of zeolite carbon composite material comprises the following steps: 1) pre-treating fly ash, wherein the pre-treatment comprises crushing, screening, washing and drying, wherein the screening is to control the particle size of fly ash to be below 200 mesh; the washing is to wash with water for 5 times; and the drying is to maintain at 90°C for 24 hours; 2) the pre-treated fly ash is evenly mixed with Na2CO3 in a ratio of 1:1 and then put into a 150mL crucible, and then put into a muffle furnace, and calcine at a high temperature of 900°C for 2 hours, and then after heating, continuous heating and cooling to room temperature, the mixture is mixed with Na2CO3 in a ratio of 1:1 and then put into a 150mL crucible, and then put into a muffle furnace, and calcine at a high temperature of 900°C for 2 hours. After that, the alkali-melted block fly ash is put into a crusher to break it up and sieve it to obtain a granular zeolite precursor; 3) The pre-prepared corn straw biochar is mixed with the zeolite precursor, a certain amount of deionized water and NaOH are added, and stirred evenly; ultrasonic treatment is performed at 45°C for a certain time; the ratio of biochar to zeolite addition is 0.07; the NaOH concentration is 3moL / L; 4) After the ultrasonic treatment, the prepared sample is poured into a polytetrafluoroethylene liner, placed in a reactor, and heated at 90°C for 24h for hydrothermal reaction. After the reaction is completed, the sample is taken out, washed with water until neutral, and dried at 105°C for standby use to obtain a zeolite-carbon composite material.

[0030] The equilibrium adsorption capacity of ammonia nitrogen and petroleum and its derivatives in ordinary groundwater by the zeolite carbon composite materials obtained in Examples 1-9 is shown in Table 1.

[0031] Table 1 NaOH concentration / (mol·L-1) Carbon to Ash Ratio Ammonia nitrogen saturated adsorption capacity / (mg·g-1) Saturated adsorption capacity of petroleum and its derivatives / (mg·g-1) Example 1 2 0.02 22.12 213.14 Example 2 2 0.045 20.19 234.76 Example 3 2 0.07 17.35 246.32 Example 4 2.5 0.02 20.23 221.13 Example 5 2.5 0.045 24.23 254.92 Example 6 2.5 0.07 19.27 257.45 Example 7 3 0.02 18.25 208.88 Example 8 3 0.045 19.05 236.16 Example 9 3 0.07 17.67 252.26 From the performance evaluation results of the embodiment, it can be seen that the concentration of sodium hydroxide selected in Example 5 is 2.5 mol·L-1 The zeolite carbon composite material obtained under the process condition of carbon-ash ratio of 0.045 has the highest unit adsorption capacity for ammonia nitrogen and petroleum and its derivatives, which can reach 24.23 and 254 mg·g, respectively. -1 .

[0032] 2.5 mol·L -1 The zeolite carbon composite material with NaOH and carbon-ash ratio of 0.045 was added into the high-salinity (salinity 2wt%) high-concentration ammonia nitrogen and petroleum and its derivatives contaminated groundwater in the simulated landfill area for adsorption test.

[0033] Comparative Example 1 The average particle size of the fly ash is 150 mesh, and the rest is the same as in Example 5.

[0034] Comparative Example 2 In step 2), no solid base is added, and the rest is the same as in Example 5.

[0035] Comparative Example 3 In step 3), no alkali solution treatment is used, and the hydrothermal reaction is directly carried out. The rest is the same as in Example 5.

[0036] Comparative Example 4 The mass ratio of biochar to zeolite precursor is 0.01, and the rest is the same as in Example 5.

[0037] Sand tank remediation tests were conducted using high-concentration ammonia nitrogen and petroleum and its derivatives contaminated groundwater simulating high salt (salinity 2wt%) in the landfill area, and the results are shown in Table 2. The specific surface area and pore volume of the zeolite-carbon composite material synthesized in Example 5 were increased by 1.3 and 4.64 times respectively compared with the original fly ash. The zeolite-carbon composite material of Example 5 has the best remediation effect, and the adsorption rate of ammonia nitrogen and crude oil and its derivatives can reach more than 90%.

[0038] Table 2 Specific surface area / (m2·g-1) Pore ​​volume / (cm3·g-1) Ammonia nitrogen saturated adsorption capacity / (mg·g-1) Ammonia nitrogen adsorption rate / (%) Adsorption amount of crude oil and its derivatives / (mg·g-1) Adsorption rate of crude oil and its derivatives / (%) Example 5 115.21 0.144 24.23 90.56 221.13 91.44 Comparative Example 1 88.25 0.031 12.53 48.23 74.141 34.65 Comparative Example 2 99.31 0.041 13.26 54.64 83.159 43.58 Comparative Example 3 97.53 0.034 10.64 30.22 103.24 52.16 Comparative Example 4 98.68 0.052 16.88 84.63 171.326 84.63 Figure 1 and Figure 2 These are the microscopic surface morphologies of fly ash and zeolite carbon composites. The smooth spheres of varying sizes in the fly ash have been transformed into fauveite and rose-like sodium stone forms, and the biochar attached to its surface can be clearly observed, which makes the surface of the material uneven and has a larger specific surface area and pores than fly ash.

[0039] Under high-salinity conditions, the concentrations of sodium, calcium, and magnesium ions in groundwater are very high. The high external ion concentration makes the zeolite body resistant to NH4 +The ion exchange of -N is inhibited, and the adsorption effect on crude oil and its derivatives is low. However, through the simulated adsorption experiment, it can be seen that the zeolite carbon composite material still has a relatively obvious ammonia nitrogen adsorption performance when used under high salt.

[0040] The present invention has been described in detail above using general instructions and specific embodiments, but conventional improvements based on the present invention are obvious to those skilled in the art. These modifications or improvements made without departing from the spirit of the present invention are all within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a zeolite-carbon composite material, comprising the following steps: 1) Pretreatment of fly ash; 2) The pretreated fly ash is mixed with solid alkali in a mass ratio of 1:0.2-5, calcined at 900°C for 1-12h, and then crushed and sieved after cooling to obtain a zeolite precursor; 3) Mix the biochar and the zeolite precursor in a mass ratio of 0.02-0.1, add alkali solution, stir evenly, react at 30-60°C for 0.5-5h to obtain a mixture; 4) The mixture obtained in step 3) is placed in a reactor and heated at 70-100° C. for 12-36 hours for hydrothermal reaction. After the reaction is completed, the product is washed with water until neutral and dried to obtain a zeolite-carbon composite material.

2. The method according to claim 1, characterized in that The pretreatment in step 1) includes crushing, screening, washing and drying. The screening is to control the particle size of fly ash below 200 mesh; the washing is to wash with water for 1-5 times; and the drying is maintained at 90-110° C. for 12-24 hours.

3. The method according to claim 1, characterized in that In step 2), the solid alkali is one or more of sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate; preferably sodium carbonate or sodium bicarbonate, and the mass ratio of the pretreated fly ash to the solid alkali is 1:0.5-2; the calcination is carried out under closed conditions; the high temperature 900°C calcination adopts programmed stage heating, and the heating time is 120-240min.

4. The method according to claim 1, characterized in that Step 3) The raw material of the biochar is one of crop straw, tree branches and leaves, wood, corn cobs, etc. The raw material of the biochar is calcined at 500-900°C for 1-12h, taken out, acid-washed, washed with water to neutrality and dried at a temperature of 100-120°C to obtain the biochar.

5. The method according to claim 1, characterized in that The mixing in step 3) is carried out under stirring, preferably under ultrasonic stirring; the alkali solution in step 3) is one of sodium hydroxide and potassium hydroxide, and its concentration is 1-5 mol / L; preferably, the mass ratio of biochar to zeolite precursor is 0.02-0.07, most preferably 0.04-0.05, and the concentration of the alkali solution is 2-3 mol / L.

6. The method according to claim 1, characterized in that After the hydrothermal reaction in step 4) is completed, the sample is washed with water for 5-10 times until it becomes neutral, and dried at 100-110°C for later use.

7. A zeolite-carbon composite material prepared by the method according to any one of claims 1 to 7.

8. Use of the zeolite-carbon composite material prepared by the method according to any one of claims 1 to 7 in groundwater polluted by high concentrations of ammonia nitrogen and petroleum and its derivatives.

9. The use according to claim 8, characterized in that The ammonia nitrogen concentration of the groundwater contaminated by high concentration ammonia nitrogen is greater than 500 mg·L -1 , more preferably greater than 1400 mg·L -1 ; Petroleum and its derivatives concentration greater than 500 mg·L -1 , more preferably greater than 1000 mg·L -1 The salt concentration of the groundwater contaminated with high concentrations of ammonia nitrogen is 1-2wt%, more preferably 1.5-2wt%; the temperature of the groundwater contaminated with high concentrations of ammonia nitrogen is 0-25°C, more preferably 5-15°C.

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