CN114768759B - K monoatomic doped biomass charcoal adsorption material, preparation method and application - Google Patents

Abstract

K single-atom doped biomass charcoal adsorption material, preparation method and application thereof, and application of material to environmental concentration (0.3 mug/L) in water body<c<1 μg/L) perfluorooctanoic acid (PFOS) and perfluorooctane sulfonic acid (PFOS) to achieve high-efficiency adsorption removal. The K single-atom doped coconut shell carbon adsorption material is prepared by taking dry coconut shells and KOH as precursors through a curing-induction calcination method. Doping of K monoatoms can change the local charge density of the substrate, and an effective electron migration channel is constructed; the non-equivalent double-site synergism of K monoatoms and adjacent C can obviously strengthen BC-K ₁ Adsorption capacity and adsorption stability to PFOA and PFOS. The invention adsorbs the environmental concentration PFOA and PFOS in deionized water, tap water and lake water in a dynamic adsorption system, the adsorption rate reaches more than 96%, and the concentration of target pollutants in the effluent can be maintained below 70 ng/L.

Description

K monoatomic doped biomass charcoal adsorption material, preparation method and application

Technical Field

The invention belongs to the technical field of environmental engineering, and particularly relates to innovation of an efficient adsorption method for perfluorinated compounds with environmental concentration in water by using the material, and relates to a K single-atom doped biomass charcoal adsorption material, a preparation method and application.

Background

Perfluorinated compounds in water are typical persistent organic pollutants, which severely threaten the ecological environment and human health. The United States Environmental Protection Agency (USEPA) has set the upper health recommended value limit for the two typical perfluoro compounds perfluorooctanoic acid (PFOS) and perfluorooctane sulfonic acid (PFOS) to 70ng/L (C) in total in potable water _PFOA+PFOS <70 ng/L), as in the prior art: USEPA, face sheet PFOA&PFOS drinking water health advisories,2016.https:// www.epa.gov/groundwater-and-drinking-water/drinking-water-health-advisories- pfoa-andpfosThe method comprises the steps of carrying out a first treatment on the surface of the Furthermore, the European Union is also formulating FPOA and PFOS safety in drinking waterFull limit. Although Fenton, electrochemical oxidation, electroflocculation and other treatment technologies have better degradation performance on high-concentration FPOA and PFOS, the treatment technology has better degradation performance on environmental concentration (0.3 mug/L<c<1 mug/L) has limited degradation capability of FPOA and PFOS, is difficult to meet the standard requirement of drinking water quality, and contains a large amount of short-chain perfluorinated compounds, so that the aim of complete removal and mineralization cannot be achieved. Prior art [ Arvaniti, o.s.; stasinakis, a.s., review on the occurrence, fate and removal of perfluorinated compounds during wastewater treatment. Sci.total environ.2015,524-525,81-92; pierpaoli, M.; szopinska, m.; wilk, b.k.; sobaszek, m.; luczkiewicz, a.; bogdanawicz, r.; fudala-Ksialek, S., electrochemical oxidation of PFOA and PFOS in landfill leachates at low and highly boron-noted diamond electrodes J.Hazard. Mater.2021,403, 123606; santos, a.; rodriguez, s.; pardo, F.; romero, A., use of Fenton reagent combined with humic acids for the removal of PFOA from contaminated water. Sci. Total environ.2016,563-564,657-663.]Compared with the water treatment technology, the adsorption method is a treatment technology capable of meeting strict requirements of drinking water quality standards. In recent years, some research has focused on the synthesis of novel organic polymer adsorbents to remove concentrations<FPOA, PFOS and perfluorocompound alternatives at 1 μg/L, as in the prior art: xiao, l.; ling, y; alsbaie, a.; li, C; helbling, d.e.; dichtel, w.r., beta-cyclodextrin polymer network sequesters perfluorooctanoic acid at environmentally relevant concentrations.j.am.chem.soc.2017,139, 7689-7692; in addition, for example, ateia et al (Ateia, M.; arifuzzaman, M.; pellizzeri, S.; attia, M.F.; tharayil, N.; anker, J.N.; karafil, T.; cationic polymer for selective romval of GenX and short-chain PFAS from surface waters and wastewaters at ng/L levels.Water Res.2019,163, 114874.) designed the selective removal of short chain perfluorinated compounds by cationic polymers with full consideration of background organics and anionic influencing factors in the aqueous environment. However, the above-mentioned adsorbent is generally in the structure of organic molecules or metal components containing N, S element, and there is a risk of leaching during use. At the same time, the materials also have synthesis workComplicated process, low adsorption rate or adsorption capacity, etc. Carbon-based adsorption materials are widely applied to the field of wastewater treatment, but the adsorption materials related to the previous research cannot realize effective adsorption on PFOA and PFOS with environmental concentration (CN 112028052 A;CN 112191229 A;CN 111318272 A;CN 111013539 A;CN 110339817 A;CN 109289775 A;CN 109046240 A;CN 105597698 A;CN 102681429A). Thus, it is desirable to functionalize it to enhance removal of perfluorocarbons at ambient concentrations.

Monoatomic catalysts are widely studied in the catalytic field by their unique properties. The isolated metal atoms are stably present by chemical bonds with the substrate material. The monoatomic structure can effectively change the local charge density of the catalytic material, so that the part has charging characteristics and can adsorb target substances, and the method is the first step of catalytic reaction. Jakub et al (Jakub, z.; hulva, j.; meier, m.; bliem, r.; kraushofer, f.; setvin, m.; schmid, m.; diebold, u.; franchini, c.; parkinson, g.s.; local structure and coordination define adsorption in a model Ir) ₁ /Fe ₃ O ₄ single-atom catalyst. Angew. Chem.2019,131, 14099-14106.) studied that CO is in Ir ₁ /Fe ₃ O ₄ (001) The adsorption process at the interface, which has a large impact on the subsequent oxidation reaction rate. Thus, monoatomic materials can act as a potential adsorbent. At present, in the field of wastewater treatment, no research on directly adsorbing target pollutants by using monoatomic materials is available.

Disclosure of Invention

In order to solve the problem that the prior art cannot effectively remove the environmental concentration PFOA and PFOS in a water body, K monoatoms are introduced into a biomass charcoal substrate to construct non-equivalent double adsorption sites to form an effective electron transfer channel, so that the charge transfer capacity is enhanced, the adsorption performance of the material is further improved to realize effective adsorption of target pollutants, and the invention discloses a K monoatom doped biomass charcoal adsorption material, a preparation method and application thereof, wherein the technical scheme is as follows:

k monoatomic doped biomass charcoal adsorption material, wherein the adsorption material is in a dynamic adsorption systemThe PFOA and PFOS in the environment concentration in deionized water, tap water and lake water are effectively adsorbed, the adsorption rate is over 96 percent, and the target pollutant concentration in the effluent is maintained below 70 ng/L; the method is characterized in that: k monoatoms exist on the surface of the material in the form of K-O coordination bonds; meanwhile, the non-equivalent double-site structure formed by the K single atom and the adjacent C atom can obviously strengthen the BC-K by the synergistic effect of the non-equivalent double-site structure formed by the K single atom and the adjacent C ₁ Adsorption capacity and adsorption stability to PFOA and PFOS.

The invention also discloses a preparation method of the K monatomic doped biomass charcoal adsorption material, which comprises the K monatomic doped coconut shell charcoal adsorption material as claimed in claim 1, and is characterized in that: the method comprises the following steps:

step 1: preparing KOH solution with a certain concentration by deionized water, putting the dried coconut shell and KOH into the KOH solution according to a certain mass ratio, and stirring at room temperature;

step 2: the solution is put into a baking oven, baked at a certain temperature and cured; then taking out the coconut shells from the reaction liquid, putting the coconut shells into a crucible, and baking and drying the coconut shells in an oven at a certain temperature until the coconut shells are completely dried;

step 3: taking out the crucible from the oven, weighing KOH with certain mass, pouring the KOH into the bottom of the crucible, placing the dried cured coconut shell on the KOH, placing the crucible into a tube furnace, and adding the dried cured coconut shell into N ₂ Calcining in atmosphere, heating up in a gradient way at a certain heating rate, respectively maintaining the temperature at different temperature points for reacting for a certain time, naturally cooling to room temperature after the reaction is finished, and taking out;

step 4: preparing an HCl aqueous solution with a certain concentration, crushing the calcined coconut shell carbon material, pouring the crushed coconut shell carbon material into the HCl aqueous solution, standing, performing suction filtration, and leaching with deionized water until the pH value of the leaching solution is=7;

step 5: drying the material after suction filtration in a drying oven to obtain K single-atom doped coconut shell carbon (BC-K) ₁ )。

The invention also discloses a removal method applied to removing the PFOA and PFOS in the water body, which comprises the following steps:

step 1: BC-K ₁ Grinding the material, sieving with 40 mesh sieve, sieving to obtain powderAdding the adsorbent into a filtering column with the diameter of 0.8cm, filling the filtering column, adding sand filter plates before and after the filtering column to prevent the adsorbent from leaking, fixing a cock, and placing the adsorbent into a dynamic adsorption test system;

step 2: the testing temperature is 25 ℃, deionized water, tap water and lake water are selected to prepare 0.3-1.0 mug/L PFOA and PFOS mixed solution, namely the mass ratio of PFOA to PFOS is 10:1-1:10, and BC-K is used ₁ The dynamic adsorption system of (2) can maintain stable water quality, the total content of PFOA and PFOS in the water is between 10 and 60ng/L, and under the dynamic adsorption condition, the adsorption capacity of the adsorption material to 0.3 to 1.0 mug/L PFOA and PFOS can respectively reach 200mg _PFOA /g _BC-K1 And 150mg _PFOS /g _BC-K1 。

The beneficial effects are that:

the biomass adopted in the invention adopts coconut shells, on one hand, the coconut shells are wide in source and low in cost, on the other hand, cellulose is taken as a framework in the structure, lignin is taken as a filler, and after lignin is removed in the curing treatment process, the cellulose framework is reserved, so that a multistage pore structure can be effectively formed in the calcination stage; meanwhile, the cellulose skeleton structure is favorable for anchoring K monoatoms, and experiments show that other biomasses such as straw, wood dust and the like cannot exist in the structure, so that the effect is poor.

In the method, K monoatomic doping of the coconut shell carbon adsorption material is adopted for the first time to realize the environmental concentration (0.3 mug/L) in the water body<c<1. Mu.g/L) PFOA and PFOS removal. In the step 1, the coconut shell is cured by using KOH solution, so that the proportion of main components such as cellulose, hemicellulose, lignin and the like in the coconut shell component can be changed, and the pore structure of the material in the calcination process can be regulated and controlled. In addition, in the calcination process, the KOH additionally added can provide a molten reaction environment for curing the coconut shell, and induce oxygen-containing functional groups to be doped on the surface of the coconut shell carbon to form sites capable of capturing monoatomic K; after capturing the K monoatoms, a stable coordination structure is formed, which can also increase the stability of oxygen-containing functional groups on the surface of the coconut carbon. Through structural characterization means such as an X-ray near-edge absorption structure, an X-ray photoelectron spectroscopy, a spherical aberration correction scanning electron microscope, an in-situ infrared spectroscopy and the like, the K single atom is confirmed to be on the coconut carbon substrateAnd forming a surface. Comparison with a control group (BC) to which KOH had not been added during calcination, shows that BC-K ₁ The content of O and K elements is 10 times and 5 times that of BC. This also shows that the doping of K single atoms forms a stable coordination structure, and can effectively fix the oxygen-containing functional group structure on the surface of the coconut shell carbon. Constructing BC-K according to the structural characterization result ₁ And (3) a structural model, namely calculating the adsorption energy of different sites of the material to PFOA and PFOS through a density functional theory. The two-site structure formed by the single atom K and the adjacent C was found to have the highest adsorption energy for the target contaminant. On the basis, the adsorption of the PFOA and the BC-K before and after PFOS by the adsorption site is further calculated ₁ The differential charge density change and the bard charge migration condition of the structure show that doping of single atom K can obviously change the local charge density of the BC substrate, and an effective charge migration channel is constructed; meanwhile, adjacent C atoms can also provide a charge transfer channel for the BC substrate in the adsorption process, so that the non-equivalent double-site synergism of single-atom K and adjacent C can obviously strengthen the BC-K ₁ Adsorption capacity and adsorption stability to PFOA and PFOS. The curing-KOH induced calcination method provided by the invention has the advantages of simple process flow, low raw material cost, no toxic and harmful metal and organic matter components, and is a functional coconut shell carbon adsorption material method easy for industrial production, and the material can realize high-efficiency and low-consumption removal of the environmental concentration PFOA and PFOS in the water body.

Drawings

FIG. 1 is a schematic diagram of a dynamic adsorption system according to the present invention;

in the figure: the water inlet water tank (1), the peristaltic pump (2), the baffle plug (3) with the sand filter element, the adsorption column (4) and the water outlet water tank (5).

Detailed Description

The following describes the embodiments of the present invention in detail with reference to the technical scheme and the accompanying drawings.

The K monoatomic doped biomass charcoal adsorption material is used for effectively adsorbing the environmental concentrations PFOA and PFOS in deionized water, tap water and lake water in a dynamic adsorption system, wherein the adsorption rate is more than 96%, and the target pollutant concentration in the effluent is maintained below 70 ng/L; the method is characterized in that: the material isK monoatoms exist on the surface and are in the form of K-O coordination bonds; meanwhile, the non-equivalent double-site structure formed by the K single atom and the adjacent C atom can obviously strengthen the BC-K by the synergistic effect of the non-equivalent double-site structure formed by the K single atom and the adjacent C ₁ Adsorption capacity and adsorption stability to PFOA and PFOS.

Based on the K single-atom doped biomass charcoal adsorption material, the invention discloses a preparation method of the K single-atom doped biomass charcoal adsorption material, which is characterized by comprising the following steps of: the method comprises the following steps:

step 1: preparing a KOH solution with the concentration of 1-4mol/L by using deionized water, putting the dried coconut shell into the KOH solution, and stirring for 12-24 hours at room temperature, wherein the mass ratio of the coconut shell to the KOH is 2:1-1:3; when the KOH concentration is lower than 1mol/L, lignin components in coconut shells cannot be effectively removed; when the KOH concentration is higher than 4mol/L, excessive KOH can cause excessive hydrolysis of cellulose components in coconut shells, and influence subsequent monoatomic loading and product adsorption performance.

Step 2: the solution is put into a baking oven, baked at a certain temperature and cured; then taking out the coconut shells from the reaction liquid, putting the coconut shells into a crucible, and baking and drying the coconut shells in an oven at a certain temperature until the coconut shells are completely dried; the step 2 further comprises the following steps: the solution is put into a baking oven, baked at 50-90 ℃ for 24-72 hours, then the coconut shell is taken out from the reaction liquid, put into a crucible and dried in the baking oven at 60 ℃. When the reaction temperature is less than 50 ℃ or the reaction time is less than 24 hours, the curing process is insufficient, lignin is incompletely hydrolyzed, and the adsorption performance of the product is affected; when the reaction temperature is higher than 90 ℃ or the reaction time is longer than 72 hours, the cellulose structure in the coconut shell is damaged by hydrolysis, and the subsequent monatomic load and the product adsorption performance are affected.

Step 3: taking out the crucible from the oven, weighing KOH with certain mass, pouring the KOH into the bottom of the crucible, placing the dried cured coconut shell on the KOH, placing the crucible into a tube furnace, and adding the dried cured coconut shell into N ₂ Calcining in atmosphere, heating up in a gradient way at a certain heating rate, respectively maintaining the temperature at different temperature points for reacting for a certain time, naturally cooling to room temperature after the reaction is finished, and taking out; the mass ratio of the cured coconut shell to KOH is 10:1-5:1;

the step 3 further comprises: placing the crucible into a tube furnace, and adding the crucible into N ₂ Calcining in atmosphere, heating at 1-5deg.C/min, gradient heating, respectively reacting at 300, 500, 700 and 1000 deg.C for 0.5-1 hr, naturally cooling to room temperature after reaction, and taking out. KOH added before calcination in the step can be melted at high temperature, so that a reaction atmosphere of molten alkali is provided, and the formation of a monoatomic structure and the rearrangement of a coconut shell carbon structure are promoted. If the KOH addition amount is too large before calcination, the microcosmic appearance of the coconut shell carbon in the calcination stage is damaged, and single atoms cannot be stably loaded; if the KOH addition amount before calcination is too small, the molten alkali reaction atmosphere cannot be provided, and the monoatomic load is too small. The gradient heating in the calcination process is to fully carry out the reaction of each stage, wherein 300 ℃ is the oxygen-containing functional group in the coconut shell to fully crack, 500 ℃ is the preliminary carbonization process of the material, 700 ℃ is the single-atom loading stage assisted by molten KOH, and the final 1000 ℃ is the morphology regulation and carbon structure rearrangement stage.

Step 4: preparing an aqueous solution of HCl with the concentration of 0.1-0.5mol/L, crushing the calcined material, pouring the crushed material into the aqueous solution of HCl, standing for 12h, and adding KOH in the molar ratio of 6:5 according to the molar quantity of HCl before calcining in the step 1. Suction filtration, rinsing with deionized water until the pH of the rinse solution=7. In the step, the concentration of the HCl aqueous solution is too low, so that KOH residues in the coconut shell carbon material structure are not thoroughly removed, and the excessive HCl can cause water consumption in the subsequent washing step.

Step 5: drying the material after suction filtration in a drying oven to obtain K single-atom doped coconut shell carbon (BC-K) ₁ )。

The K single-atom doped coconut shell carbon adsorption material prepared by the preparation method of the K single-atom doped biomass carbon adsorption material is applied to removal of the concentration PFOA and PFOS in the water body; the method comprises the following steps:

step 1: BC-K ₁ Grinding the materials, sieving with a 40-mesh screen, adding the sieved powder into a filtering column with the diameter of 0.8cm, filling the filtering column, adding sand filter plates before and after the filtering column to prevent the adsorbent from leaking, fixing a cock, and placing into a dynamic adsorption test system;

step 2: testing temperature 25 deg.C, selecting deionized waterPreparing mixed solution of PFOA and PFOS with the mass ratio of 0.3-1.0 mug/L of water, tap water and lake water, namely PFOA and PFOS being 10:1-1:10, and using BC-K ₁ As shown in fig. 1, the inlet water is put into an inlet water tank (1), is sent into an adsorption column (4) with a sand filter element baffle plug (3) through a peristaltic pump (2), and finally flows into an outlet water tank (5). The water quality can be kept stable, and the total content of PFOA and PFOS in the water is between 10 and 60 ng/L; under the dynamic adsorption condition, the adsorption capacity of the adsorption material to 0.3-1.0 mug/L PFOA and PFOS can reach 200mg respectively _PFOA /g _BC-K1 And 150mg _PFOS /g _BC-K1 。

Example 1

K single-atom doped biomass charcoal adsorption material preparation:

200mL of 3mol/L KOH solution was prepared with deionized water, and 20g of dried coconut husk was placed in KOH solution and stirred at room temperature for 24h. Afterwards, the solution was put into an oven, at 60 ℃, and cured for 72 hours. Taking out coconut shell from reaction liquid, placing into crucible, drying in oven at 60deg.C, weighing cured coconut shell to 15g, pouring 2g KOH into bottom of crucible, placing dried cured coconut shell onto KOH, placing crucible into tube furnace, adding water into water, adding water, stirring, cooling, and drying to obtain the final product ₂ Calcining in atmosphere, heating at a heating rate of 5 ℃/min, heating in a gradient way, respectively reacting at the maintained temperatures of 300, 500, 700 and 1000 ℃ for 1h, naturally cooling to room temperature after the reaction is finished, and taking out. 130mL of 0.5mol/L aqueous HCl solution was prepared, the calcined material was crushed, poured into the aqueous HCl solution, and allowed to stand for 12 hours. Suction filtration, rinsing with deionized water until the pH of the rinse solution=7. Drying the material after suction filtration in a drying oven at 60 ℃ to obtain K single-atom doped coconut shell carbon (BC-K) ₁ -2). Respectively selecting 1.5g and 3g KOH as KOH addition amount in the induction calcination process, and obtaining corresponding K single-atom doped coconut shell carbon (BC-K) by other preparation methods and unchanged addition proportion ₁ -1.5 and BC-K ₁ -3)。

The K monoatomic load of different KOH addition amounts in the induction calcination process is examined through the characterization means such as a transmission electron microscope, an X-ray near-edge absorption structure, an X-ray photoelectron spectrum, an in-situ Fourier transform infrared spectrum, element analysis, an electron spin resonance spectrum and the likeInfluencing the situation, too low a KOH dosage (BC-K ₁ -1.5) the loading of K monoatoms and the content of O element in the structure can be greatly reduced, but the pore structure of the material surface and BC-K ₁ -2 are substantially identical. While too high an amount of KOH addition (BC-K) ₁ -3) increasing the loading of K monoatoms, but with a large change in the pore structure, significantly less porosity and microporous structure, and BC-K ₁ -3 ratio of yield BC-K ₁ -2 reduction by 30%. Thus, the BC-K is selected subsequently ₁ -2 as adsorbing material for PFOA and PFOS.

Example 2

The adsorption method of the environmental concentration PFOA/PFOS in deionized water comprises the following steps: 1. Mu.g/L PFOA and PFOS were prepared separately with deionized water, BC-K was prepared ₁ Grinding-2 material, sieving with 40 mesh sieve, adding the sieved powder into a filter column with diameter of 0.8cm, filling the filter column, adding sand filter plates before and after the filter column to prevent the adsorbent from leaking, fixing a cock, placing into a dynamic adsorption test system at 25deg.C, respectively taking 1 μg/L PFOA and PFOS deionized water as water inlet, and using BC-K ₁ -2 dynamic adsorption system removal, continuously running for 48 hours, taking 50mL of water per hour as a test sample, filtering the test sample by a 0.22 mu m filter membrane, placing the test sample in a plastic sample bottle, evaporating dry water at 60 ℃, eluting the sample bottle by 2mL of HPLC grade methanol, repeatedly flushing for 3 times, and reserving the test sample as an instrument for testing.

The PFOA and PFOS concentration are measured by ultra-high performance liquid chromatography, and the result shows that the PFOA and PFOS adsorption rate is over 96% per hour in the dynamic adsorption process for 48 hours.

The PFOA/PFOS adsorption performance comparison test shows that under the same test condition, the adsorption rate of PFOA and PFOS under the environment concentration by the two adsorption materials is 0 in the dynamic adsorption process for 48 hours, and effective removal cannot be realized by selecting the commercially produced coconut shell carbon adsorption material and activated carbon as a comparison group.

Example 3

The adsorption method of the environmental concentration PFOA and PFOS in tap water and lake water comprises the following steps: preparing a mixed solution of PFOA and PFOS with total concentration of 1 μg/L (PFOA to PFOS mass content ratio of 1:1) with tap water and lake water respectively, and adding BC-K ₁ -2 grinding the material, sieving with a 40 mesh screen, sievingAdding the powder into a filtering column with diameter of 0.8cm, filling the filtering column, adding sand filter plates before and after the filtering column to prevent the adsorbent from leaking, fixing a cock, placing into a dynamic adsorption test system at 25deg.C, respectively taking 1 μg/L PFOA and PFOS mixed tap water solution and lake water solution as water inlet, and using BC-K ₁ And 2, removing the dynamic adsorption system, continuously running for 48 hours, taking 50mL of water per hour as a test sample, filtering the test sample by using a 0.22 mu m filter membrane, placing the test sample into a plastic sample bottle, evaporating dry water at 60 ℃, eluting the sample bottle by using 2mL of ultrapure water, repeatedly flushing for 3 times, and extracting organic matters in the test sample by using a solid phase extraction method for remaining the test.

The PFOA and PFOS concentration are measured by ultra-high performance liquid chromatography, and the result shows that the PFOA and PFOS adsorption rate is more than 98% per hour in the dynamic adsorption process for 48 hours.

The invention provides a preparation method of a K single-atom doped biomass charcoal adsorption material, which is applied to removal of environmental concentration PFOA and PFOS in a water body. The method is characterized in that cheap dry coconut shells are used as raw materials, a KOH-induced calcination method is adopted to reconstruct the surface structure of the coconut shell carbon, so that monoatomic anchoring sites are formed, and KOH is also a reaction precursor of monoatomic K. K monoatoms in the adsorption material structure can change the local electronic structure of the substrate, and a charge migration channel is constructed, so that the charge migration capacity is enhanced. In the process of adsorbing PFOA and PFOS, K monoatoms and C atoms adjacent to the K monoatoms can form non-equivalent double sites, so that the adsorption capacity and adsorption stability of the material on target pollutants are further enhanced, and the high-efficiency removal of the environmental concentration PFOA and PFOS in a water body is realized.

According to the invention, coconut shells are used as precursors, a KOH induction calcination method is adopted, surface structural rearrangement is induced in the calcination carbonization process of the coconut shells, and meanwhile, oxygen-containing groups are doped to form K monoatomic anchoring sites, and K monoatomic is captured and the coordination structure of the K monoatomic is stabilized, so that the K monoatomic doped coconut shell carbon adsorption material is prepared. Through structural characterization and theoretical calculation, a non-equivalent double-site adsorption theory is provided, an adsorption mechanism of the material is disclosed, and efficient removal of environmental concentration PFOA and PFOS in a water body is realized.

The foregoing has shown and described the basic principles, principal features and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present invention, and various changes and modifications may be made therein without departing from the spirit and scope of the invention, which is defined by the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (1)

1. The application of the K single-atom doped biomass charcoal adsorption material is characterized in that the K single-atom doped biomass charcoal adsorption material effectively adsorbs the environmental concentration PFOA and PFOS in tap water or lake water in a dynamic adsorption system, the adsorption rate reaches more than 96%, and the target pollutant concentration in effluent is maintained below 70 ng/L; k monoatoms exist on the surface of the adsorption material in the form of K-O coordination bonds; meanwhile, a non-equivalent double-site structure is formed by a K single atom and an adjacent C atom, the synergistic effect of the non-equivalent double-site structure formed by the K single atom and the adjacent C atom remarkably strengthens the adsorption capacity and the adsorption stability of the adsorption material to PFOA and PFOS, and the environmental concentration C is 0.3 mug/L < C <1 mug/L; the preparation method of the adsorption material is characterized by comprising the following steps:

step 1: preparing a KOH solution with the concentration of 1-4mol/L by using deionized water, putting the dried coconut shell into the KOH solution, and stirring for 12-24 hours at room temperature, wherein the mass ratio of the coconut shell to the KOH is (2:1) - (1:3);

step 2: placing the stirred solution into a baking oven, baking at 50-90 ℃ for curing for 24-72 hours, taking out the coconut shells from the reaction liquid, placing the coconut shells into a crucible, and drying in the baking oven at 60 ℃ to form cured coconut shells;

step 3: taking out the crucible from the oven, weighing KOH with certain mass, pouring the KOH into the bottom of the crucible, placing cured coconut shells on the KOH, placing the crucible into a tube furnace, and adding the crucible into N ₂ Calcining in atmosphere, wherein the temperature rising rate is 1-5 ℃/min, the gradient heating is carried out, the reaction is carried out at the respective maintaining temperatures of 300, 500, 700 and 1000 ℃ for 0.5-1h, the reaction is naturally cooled to room temperature after the reaction is finished, and the calcined coconut shell carbon material is taken out; the mass ratio of the cured coconut shell to KOH is 7.5:1;

step 4: preparing an aqueous solution with the concentration of 0.1-0.5mol/LHCl, crushing the calcined coconut shell carbon material, pouring the crushed coconut shell carbon material into an aqueous solution of HCl, standing for 12 hours, carrying out suction filtration, and leaching with deionized water until the pH value of the leaching solution is=7;

step 5: and (3) putting the leached material into a drying oven for drying to obtain the K single-atom doped biomass charcoal.