A porous biochar adsorbent based on synergistic modification of polyphosphonic acid compounds with alkali and a preparation method and application thereof

Abstract

The present application relates to a kind of porous biochar adsorbent based on polyphosphonic acid compound and alkali synergistic modification and its preparation method and application.The method includes: biomass powder is mixed with polyphosphonic acid compound solution and impregnated and dried, then is pyrolyzed first, obtains polyphosphonic acid modified biochar;Polyphosphonic acid modified biochar is mixed with alkali solution and impregnated and dried, then is pyrolyzed second, finally is pickled, washed with water and dried, and porous biochar adsorbent based on polyphosphonic acid compound and alkali synergistic modification is prepared.The porous biochar adsorbent obtained in the present application has ultra-high specific surface area and abundant micro-mesoporous hierarchical structure, surface is rich in phosphorus functional group (C-O-P and O-P), and for water body, ring ciprofloxacin, paracetamol and tetracycline and other drug and personal care product pollutants show excellent adsorption capacity and removal efficiency, suitable for pharmaceutical wastewater, medical sewage and trace new pollutants in surface water deep purification, with significant application prospect.

Description

Technical Field

[0001] This invention relates to the field of adsorption materials technology, and in particular to a porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and alkali, its preparation method and application. Background Technology

[0002] Pharmaceuticals and personal care products (PPCPs), as emerging pollutants (ECs), are frequently detected in water bodies, posing potential risks to the ecological environment and human health. Adsorption is considered an effective removal method due to its simplicity, low cost, and lack of secondary pollution. Biochar, with its wide availability, renewability, and ease of modification, has become a highly regarded adsorption material.

[0003] However, raw biochar typically suffers from drawbacks such as small specific surface area, underdeveloped pore structure, and limited surface functional groups, resulting in low adsorption capacity for pollutants like ciprofloxacin, acetaminophen, and tetracycline. Existing modification methods mainly include single chemical modifications (such as KOH and H3PO4) or physical activation, but these often fail to significantly increase the specific surface area while simultaneously constructing a mesoporous structure suitable for macromolecular diffusion and introducing targeted surface functional groups. For example, while conventional KOH treatment can increase the number of micropores and specific surface area to some extent, the improvement is limited and still not conducive to the diffusion and adsorption of macromolecular pollutants. Phosphoric acid modification can introduce phosphorus-containing functional groups and promote mesopore formation, but its increase in total specific surface area is limited. Therefore, developing a porous biochar adsorbent that integrates the advantages of multiple modifications and possesses ultra-high specific surface area, well-developed hierarchical pore structure, and abundant phosphorus-containing functional groups is of great significance for the efficient removal of pharmaceutical and personal care product pollutants such as ciprofloxacin, acetaminophen, and tetracycline from water bodies.

[0004] In summary, in order to solve one or more of the technical problems mentioned above, it is necessary to provide a porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and alkali, as well as its preparation method and application. Summary of the Invention

[0005] To address one or more technical problems existing in the prior art, this invention provides a porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and alkali, and its preparation method. This invention provides a simple, low-cost, and high-adsorption-performance method for preparing a porous biochar adsorbent synergistically modified with polyphosphonic acid compounds and alkali, as well as the application of this porous biochar adsorbent in the efficient adsorption and removal of new pollutants in water. The porous biochar adsorbent obtained by this invention possesses an ultra-high specific surface area and a rich micro-mesoporous hierarchical structure, with a surface rich in phosphorus functional groups (COP and OP). It exhibits excellent adsorption capacity and removal efficiency for pollutants such as ciprofloxacin, acetaminophen, and tetracycline from pharmaceuticals and personal care products in water, and is suitable for the deep purification of trace new pollutants in pharmaceutical wastewater, medical wastewater, and surface water, showing significant application prospects.

[0006] The present invention provides a method for preparing a porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and alkali, the method comprising the following steps: (1) The biomass powder was mixed with a polyphosphonic acid compound solution, impregnated and dried, and then subjected to a first pyrolysis to obtain polyphosphonic acid modified biochar; (2) The polyphosphonic acid modified biochar was mixed with an alkaline solution, impregnated and dried, then subjected to a second pyrolysis, and finally acid washing, water washing and drying to obtain a porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compound and alkali.

[0007] Preferably, in step (1): the biomass powder is obtained by washing, cutting, drying, crushing and sieving lignocellulosic biomass; preferably, the lignocellulosic biomass is one or more of agricultural and forestry waste, grass leaves and wood materials, more preferably, the lignocellulosic biomass is one or more of corn cobs, straw, grass leaves, fruit shells and wood materials, and even more preferably, the lignocellulosic biomass is corn straw.

[0008] Preferably, in step (1): the polyphosphonic acid compound solution contains one or more of the following: hexamethylenediaminetetramethylenephosphonic acid, hexamethylenediaminetetramethylenephosphonate, 1-hydroxyethylidene-1,1-diphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonate, inositol hexaphosphate, and inositol hexaphosphate.

[0009] Preferably, in step (1): the mass concentration of the polyphosphonic acid compound in the polyphosphonic acid compound solution is 5-20%, preferably 15%; the mass ratio of the biomass powder to the polyphosphonic acid compound solution is 1:(4~6); and / or the mixing and impregnation time is 2~6h.

[0010] Preferably, in step (2): the alkali in the alkaline solution is sodium hydroxide and / or potassium hydroxide; the concentration of the alkaline solution is 0.5~1.5 mol / L; the mass ratio of the polyphosphonic acid modified biochar to the alkali in the alkaline solution is 1:(2~5); and / or the mixing and impregnation time is 0.5~1.5 h.

[0011] Preferably, the first pyrolysis and / or the second pyrolysis are carried out under an inert atmosphere; the temperature of the first pyrolysis is 400~600℃ and the time is 1~3h; and / or the temperature of the second pyrolysis is 600~800℃ and the time is 1~3h.

[0012] Preferably, the porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and alkali has a specific surface area ≥2200 m². 2 / g; and / or the porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and base has a maximum adsorption capacity of ≥500 mg / g for ciprofloxacin in aqueous solution, a maximum adsorption capacity of ≥250 mg / g for paracetamol, and a maximum adsorption capacity of ≥500 mg / g for tetracycline.

[0013] In a second aspect, the present invention provides a porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and alkali, prepared by the preparation method described in the first aspect of the present invention.

[0014] In a third aspect, the present invention provides the application of porous biochar adsorbents based on the synergistic modification of polyphosphonic acid compounds and alkali, prepared by the preparation method described in the first aspect, in the adsorption and removal of quinolone antibiotics, tetracyclic antibiotics, aniline drugs and / or other drug and personal care product pollutants in water.

[0015] In a fourth aspect, the present invention provides a method for adsorbing and removing pharmaceutical and personal care product contaminants from water bodies. The method involves adding a porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and alkali, prepared by the preparation method described in the first aspect of the present invention, to water bodies containing ciprofloxacin, acetaminophen, and / or tetracycline for adsorption treatment.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: (1) This invention proposes a novel synergistic modification strategy of “pretreatment with polyphosphonic acid compound followed by alkali activation”. By using polyphosphonic acid compound as a phosphorus source, it reacts with biomass in the first pyrolysis stage and utilizes its high decomposition temperature to achieve the gradual release of phosphate groups, so that COP bonds are slowly formed during carbonization. This avoids the excessive cross-linking or structural damage caused by the rapid reaction of traditional phosphoric acid, thus preserving the integrity of the carbon matrix and creating favorable conditions for subsequent alkali activation. On this basis, alkali solution mixing and impregnation and second pyrolysis (i.e. alkali activation) are carried out. The key is that the alkali activation process is not simply pore-forming, but by precisely controlling the reaction conditions (such as the amount of alkali, the temperature and time of alkali solution mixing and impregnation), the alkali and some COP bonds are controlled to break, thereby moderately weakening the binding force between phosphate particles and carbon surface, causing some phosphate particles to fall off. This not only removes excess deposits that may block the pores, but also helps to retain the uniformly dispersed phosphorus-containing active sites (COP). This invention creatively utilizes this mechanism to partially detach phosphate particles originally attached to the surface of biochar due to the breakage of their bonds. This not only removes agglomerates that clog the pores but also avoids the complete loss of overall phosphorus function, achieving unblocking and optimization of the pore structure. Simultaneously, the remaining COP functional groups are redistributed on the carbon surface and maintain a uniform coverage, forming a stable functional thin layer dominated by phosphorus-containing active sites. The deep etching effect of the alkali further develops abundant micropores, which, together with the mesopores left after the phosphate particles detach, construct a well-developed hierarchical pore structure, ultimately yielding a porous biochar adsorbent with extremely high specific surface area, good pore connectivity, and a uniformly loaded COP functional group surface. This is completely different from existing technologies that involve "alkali treatment followed by phosphoric acid modification," leading to pore blockage, uneven phosphorus doping distribution in a "one-step" method, or simply using phosphoric acid modification or alkali treatment modification. It solves the technical challenge of simultaneously achieving high specific surface area and uniform loading of phosphorus-containing functional groups.

[0017] (2) The present invention has a synergistic effect. The polyphosphonic acid pretreatment not only introduces phosphorus-containing functional groups (COP functional groups and / or OP functional groups, etc.) which are beneficial to electrostatic interaction and complexation, but also pre-constructs a mesoporous framework with the gas and intermediate products generated by its thermal decomposition. The subsequent alkali activation efficiently etches a large number of micropores on this framework and further expands the specific surface area. The two work together to achieve the precise construction of a multi-level pore structure of "mesoporous guidance and micropore creation". The porous biochar adsorbent prepared by the present invention has both ultra-high specific surface area and a suitable proportion of mesopores with larger molecular size. At the same time, the surface is rich in phosphorus-containing and oxygen-containing functional groups. It synergistically adsorbs pollutants such as ciprofloxacin, acetaminophen and tetracycline through multiple mechanisms such as pore filling, π-π conjugation, hydrogen bonding and electrostatic attraction. The adsorption capacity is significantly higher than that of most biochar-based adsorbents reported in the present invention.

[0018] (3) The raw materials used in this invention are green and the preparation process is simple. For example, waste corn stalks can be used as raw materials to realize the high-value utilization of waste. The two-step pyrolysis process is simple and easy to scale up. The porous biochar adsorbent prepared by this invention has an ultra-high specific surface area and a rich micro-mesoporous hierarchical structure. The surface is rich in phosphorus functional groups. It exhibits excellent adsorption capacity and removal efficiency for drugs and personal care product pollutants such as ciprofloxacin, acetaminophen and tetracycline in water. It is suitable for the deep purification of trace new pollutants in pharmaceutical wastewater, medical wastewater and surface water. It has wide applicability. The adsorbent is stable under different water quality conditions and has significant application prospects. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 These are SEM images of the biochar adsorbents prepared in Examples 1, 4, and 5 of this invention; A is an SEM image of corn straw biochar; B is an SEM image of the biochar adsorbent prepared in Comparative Example 5, b is a magnified view; C is an SEM image of the biochar adsorbent prepared in Comparative Example 4, c is a magnified view; D is an SEM image of the porous biochar adsorbent prepared in Example 1, d is a magnified view; E is an SEM-EDS image of the surface of the porous biochar adsorbent sample prepared in Example 1. Figure 2 This is a TEM image of the biochar adsorbent prepared in Example 1 of the present invention; Figure 3 The results show the adsorption performance of biochar adsorbents prepared in Examples 1, 4, and 5 of this invention on ciprofloxacin. A is a comparison of the adsorption capacity of different materials, B is the effect of the dosage of the sample in Example 1 on the removal rate and the unit adsorption capacity, C is a comparison of the adsorption capacity of each material at different pH values, and D is the anti-ion interference ability of the sample in Example 1 in adsorbing ciprofloxacin. Figure 4 These are the nitrogen adsorption-desorption curves and pore size distribution diagrams of the porous biochar adsorbent prepared in Example 1 of this invention; A is the nitrogen adsorption-desorption curve, and B is the pore size distribution curve. Figure 5 These are XPS comparison images of the biochar adsorbents prepared in Example 1 and Comparative Example 4 of the present invention; A is the fine XPS P2p spectrum of the biochar adsorbent prepared in Comparative Example 4, and B is the fine XPS P2p spectrum of the porous biochar adsorbent prepared in Example 1. Figure 6 This is the XPS total spectrum of the biochar adsorbents prepared in Examples 1, 4, and 5 of this invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0022] The present invention provides a method for preparing a porous biochar adsorbent (hereinafter referred to as porous biochar adsorbent) based on the synergistic modification of polyphosphonic acid compounds and alkali, the method comprising the following steps: (1) The biomass powder was mixed with a polyphosphonic acid compound solution, impregnated and dried, and then subjected to a first pyrolysis to obtain polyphosphonic acid modified biochar; (2) The polyphosphonic acid modified biochar is mixed with an alkaline solution, impregnated and dried, then subjected to a second pyrolysis, and finally acid-washed, water-washed and dried to obtain a porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compound and alkali; In this invention, the mixed impregnation refers to impregnating the biomass powder with the polyphosphonic acid compound solution or the polyphosphonic acid modified biochar with the alkaline solution by stirring, that is, by stirring to make the solution penetrate evenly. This invention does not specify the stirring speed, for example, it can be 100~800 r / min. The mixed impregnation can be carried out in an environment of room temperature of 15~35℃; In this invention, step (1) The drying conditions in step (2), including drying before the second pyrolysis and drying after water washing, can be, for example, drying to constant weight at 60-100°C. This invention does not specifically limit the acid washing and water washing; those skilled in the art can choose conventionally. In this invention, the acid washing is, for example, as follows: first, soaking the sample in deionized water (mass ratio of sample to deionized water is 1:5) for 30 minutes, then filtering and rinsing three times with deionized water; subsequently, adding the obtained sample back into deionized water, and slowly adding 1 mol / L hydrochloric acid (dropping rate 1-2 drops / second) under stirring until no more bubbles are generated in the system. After adding 1 mol / L hydrochloric acid (the amount added is 10-20% of the total amount of the previously slowly added hydrochloric acid), soaking for 6 hours, and then filtering, the acid-washed sample is obtained. The water washing involves washing the acid-washed sample with deionized water until neutral.

[0023] During the research and development of this invention, it was discovered that the preparation of porous biochar adsorbents currently faces the common problem of difficulty in simultaneously achieving high specific surface area and uniform COP functional group loading. For example, the method of "first alkali activation, then phosphoric acid modification" usually uses phosphoric acid or phosphate as the phosphorus source and performs secondary modification on biochar that has already been activated by alkali and has a high specific surface area. Due to the extremely high reactivity of phosphoric acid, it is very easy to undergo violent dehydration condensation with the carbon surface during subsequent pyrolysis, resulting in local excessive cross-linking and the generation of a large number of amorphous or crystalline phosphate deposits. These products often physically block the pore inlets in particulate form, resulting in a significant decrease in specific surface area. Furthermore, phosphorus is distributed very unevenly on the surface, making it difficult to form a continuous and stable COP functional layer, and the utilization rate of adsorption sites is low. For example, the "one-step co-carbonization" method, which directly mixes phosphoric acid or phosphate with biomass to complete carbonization and phosphorus doping in one step, can introduce phosphorus in the early stage of carbon framework formation. However, because phosphoric acid reacts rapidly, it is easy to react with biomass at low temperatures, destroying the original microstructure and inhibiting the development of pores in the later stage. At the same time, the strong acidity of phosphoric acid can catalyze the over-carbonization of components such as sugars, generating dense, non-porous carbon. Although the final material contains phosphorus, it has a low specific surface area, closed pore structure, high mass transfer resistance, and deeply buried active sites, making it difficult to effectively contact pollutants. Moreover, it is generally believed that once phosphorus modification is completed, subsequent strong alkali treatment will inevitably destroy phosphorus-containing functional groups. Therefore, structural regulation after the introduction of phosphorus is generally avoided, which restricts the development of high-performance phosphorus-functionalized biochar.

[0024] To address this technical challenge, this invention proposes a novel synergistic modification strategy of "pretreatment with polyphosphonic acid compounds followed by alkali activation." By using polyphosphonic acid compounds as a phosphorus source, they react with biomass in the first pyrolysis stage. The high decomposition temperature of these compounds allows for the gradual release of phosphate groups, enabling the slow formation of COP bonds during carbonization. This avoids the excessive cross-linking or structural damage caused by the rapid reaction of traditional phosphoric acid, thus preserving the integrity of the carbon matrix and creating favorable conditions for subsequent alkali activation. Based on this, an alkaline solution mixing and impregnation followed by a second pyrolysis (i.e., alkali activation) is then performed. The key is that this alkali activation process is not simply about creating pores, but rather about precisely controlling the reaction conditions (such as the amount of alkali, the temperature and time of alkaline solution mixing and impregnation) to cause the alkali to break some of the COP bonds in a controlled manner. This moderately weakens the binding force between the phosphate particles and the carbon surface, causing some particles to detach. This not only removes excess deposits that may clog the pores but also better preserves the uniformly dispersed phosphorus-containing functional groups (COP and / or OP). This invention creatively utilizes this mechanism to partially detach phosphate particles originally attached to the surface of biochar due to the breakage of their bonds. This not only removes agglomerates that clog the pores but also avoids the complete loss of overall phosphorus function, achieving unblocking and optimization of the pore structure. Simultaneously, the remaining COP functional groups are redistributed on the carbon surface and maintain a uniform coverage, forming a stable functional thin layer dominated by phosphorus-containing active sites. The deep etching effect of the alkali further develops abundant micropores, which, together with the mesopores left after the phosphate particles detach, construct a well-developed hierarchical pore structure, ultimately yielding a porous biochar adsorbent with extremely high specific surface area, good pore connectivity, and a uniformly loaded COP functional group surface. This is completely different from existing technologies that involve "alkali treatment followed by phosphoric acid modification," leading to pore blockage, uneven phosphorus doping distribution in a "one-step" method, or simply using phosphoric acid modification or alkali treatment modification. It solves the technical challenge of simultaneously achieving high specific surface area and uniform loading of phosphorus-containing functional groups.

[0025] According to some preferred embodiments, in step (1): the biomass powder is obtained by washing, cutting, drying, crushing and sieving lignocellulosic biomass; specifically, for example, the lignocellulosic biomass is washed and cut into blocks, and then the blocks are dried, crushed and sieved to obtain biomass powder with a particle size of less than 40 mesh (i.e., it can pass through a 40-mesh sieve); the present invention does not specifically limit the washing, cutting, drying, crushing and sieving, which are conventional techniques in the field; preferably, the lignocellulosic biomass is one or more of agricultural and forestry waste, grass leaves and wood materials, more preferably, the lignocellulosic biomass is one or more of corn cobs, straw, grass leaves, fruit shells and wood materials, and even more preferably, the lignocellulosic biomass is corn straw.

[0026] According to some specific embodiments, the preparation of the porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and alkali includes: washing and cutting lignocellulosic biomass into blocks, then drying, crushing and sieving the blocks to obtain biomass powder with a particle size of less than 40 mesh (i.e., passing through a 40-mesh sieve); mixing and impregnating the biomass powder with a polyphosphonic acid compound solution and drying it, then subjecting it to a first pyrolysis to obtain polyphosphonic acid modified biochar; mixing and impregnating the polyphosphonic acid modified biochar with an alkali solution and drying it, then subjecting it to a second pyrolysis, and finally acid washing, water washing and drying to obtain the porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and alkali.

[0027] In this invention, the polyphosphonic acid compound is a polyphosphonic acid compound with a high pyrolysis temperature, such as hexamethylenediaminetetramethylenephosphonic acid (salt), 1-hydroxyethylidene-1,1-diphosphonic acid (salt), and inositol hexaphosphate (salt).

[0028] According to some preferred embodiments, in step (1): the polyphosphonic acid compound solution contains one or more of the following: hexamethylenediaminetetramethylenephosphonic acid, hexamethylenediaminetetramethylenephosphonate, 1-hydroxyethylidene-1,1-diphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonate, inositol hexaphosphate, and inositol hexaphosphate. This invention has found that using these polyphosphonic acid compounds, compared to using inorganic phosphoric acid or phosphate modified and then activated with alkali, significantly improves the specific surface area and adsorption performance. The possible reason is that this invention uses polyphosphonic acid compounds with slow-release properties to replace traditional highly reactive inorganic phosphoric acid. In the first pyrolysis stage, the polyphosphonic acid compounds gradually decompose and release phosphate groups, which is more conducive to the in-situ, gradual construction of COP bonds. This avoids premature cross-linking or pore blockage of the precursor caused by the violent reaction of inorganic phosphoric acid, effectively preserving the structural integrity and adjustability of the carbon matrix, allowing the alkali to fully react with the carbon matrix during alkali activation to generate sufficient micropores. Based on this, alkaline solution mixing and impregnation followed by a second pyrolysis are performed, causing controlled breakage of some COP bonds by the alkali. This moderately weakens the binding force between phosphate particles and the carbon surface, promoting the detachment of some particles. This process not only removes excess deposits that may clog pores but also better preserves uniformly dispersed phosphorus-containing active sites. Simultaneously, the moderate etching of the carbon matrix by the alkali further develops micropores, which, together with the mesopores formed by desorption, construct a well-developed hierarchical porous structure, significantly improving specific surface area and pore connectivity. Meanwhile, the stable COP functional groups generated in situ from polyphosphonic acid are preserved and fully exposed, forming a uniformly distributed functional thin layer of phosphorus-containing active sites (COP thin layer). Therefore, this invention achieves the synergistic integration of high specific surface area, excellent mass transfer channels, and high content of COP functional sites (the phosphorus-containing functional groups in this invention are mainly COP functional groups), overcoming the technical defects of traditional phosphoric acid modification, such as uneven phosphorus distribution or increased clogging caused by "alkali modification first, then phosphoric acid modification" and the destruction of COP bond construction by "phosphoric acid modification first, then alkali modification".

[0029] According to some preferred embodiments, in step (1): the mass concentration (i.e., mass percentage) of the polyphosphonic acid compound in the polyphosphonic acid compound solution is 5-20% (e.g., 5%, 10%, 15% or 20%), preferably 15%; the mass ratio of the biomass powder to the polyphosphonic acid compound solution is 1:(4~6) (e.g., 1:4, 1:5 or 1:6); and / or the mixing and impregnation time is 2~6h (e.g., 2, 3, 4, 5 or 6h), preferably 4h.

[0030] According to some more preferred embodiments, in step (1), the mass ratio of the biomass powder to the polyphosphonic acid compound contained in the polyphosphonic acid compound solution is 1:(0.6~0.8) (e.g. 1:0.6, 1:0.7, 1:0.75 or 1:0.8); the mixing and impregnation time is 2~6h.

[0031] According to some preferred embodiments, in step (2): the alkali contained in the alkaline solution is sodium hydroxide and / or potassium hydroxide, preferably potassium hydroxide; the concentration of the alkaline solution is 0.5~1.5 mol / L (e.g. 0.5, 0.8, 1, 1.2 or 1.5 mol / L); in this invention, the alkaline solution is an alkaline aqueous solution; the mass ratio of the polyphosphonic acid modified biochar to the alkali contained in the alkaline solution is 1:(2~5) (e.g. 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5 or 1:5), preferably 1:4; and / or the mixing and impregnation time is 0.5~1.5 h (e.g. 0.5, 0.8 or 1 h).

[0032] In step (2), it is preferable that the mass ratio of the polyphosphonic acid modified biochar to the alkali contained in the alkaline solution is 1:(2~5), and the mixing and impregnation time is 0.5~1.5h. This ensures efficient activation while avoiding excessive etching. Under these ratio and time conditions, the alkali can fully wet and penetrate the pore structure of the polyphosphonic acid modified biochar. During the second pyrolysis process, it reacts controllably with some inactive or weakly bound COP bonds, moderately weakening the connection between the phosphate or pyrophosphate aggregates deposited on the pore openings or surface and the carbon skeleton, causing them to partially detach, thereby releasing the pore blockage, clearing the mass transfer channels, and significantly improving the specific surface area and pore connectivity of the porous biochar adsorbent material. At the same time, due to the moderate impregnation time, the interaction time between the alkali and the carbon matrix is ​​limited, avoiding the collapse of the carbon skeleton or the destruction of active sites caused by deep etching, thus allowing the originally masked carbon matrix to be fully activated. The buried COP functional sites are exposed, forming a uniformly distributed phosphorus-containing active functional thin layer. This invention found that if the proportion of alkali is too low, the activation intensity is insufficient, making it difficult to effectively remove phosphate deposits that clog the pores, resulting in poor pore development and limited improvement in specific surface area. If the proportion of alkali is too high, the alkali will etch the carbon skeleton too violently, not only causing excessive expansion of micropores or even pore wall rupture, leading to structural instability, but also attacking the already formed stable COP bonds, resulting in a large loss of phosphorus-containing active functional sites. If the impregnation time is too short, the alkali solution cannot be fully distributed into the material, resulting in uneven activation and local blockage. If the time is too long, the reaction between alkali and carbon and phosphate tends to be violent and uncontrollable, aggravating carbon loss and destruction of phosphorus-containing active functional sites, ultimately leading to the deterioration of the pore structure, decrease in specific surface area, and decline in adsorption performance of the porous biochar adsorbent material.

[0033] According to some preferred embodiments, the first pyrolysis and / or the second pyrolysis are carried out in an inert atmosphere (e.g., a nitrogen atmosphere and / or an argon atmosphere); in this invention, preferably, the inert atmosphere is nitrogen and / or argon, and the flow rate of nitrogen and / or argon is 100-300 mL / min; the temperature of the first pyrolysis is 400-600°C (e.g., 400°C, 450°C, 500°C, 550°C or 600°C), preferably 500°C, and the time is 1-3 hours (e.g., 1, 2 or 3 hours), preferably 2 hours; and / or the temperature of the second pyrolysis is 600-800°C (e.g., 600°C, 650°C, 700°C, 750°C or 800°C), preferably 700°C, and the time is 1-3 hours (e.g., 1, 2 or 3 hours), preferably 2 hours; in this invention, the heating rate to the first pyrolysis temperature and / or the second pyrolysis temperature can be, for example, 3-10°C / min, preferably 5°C / min.

[0034] In step (1), the present invention preferably controls the mass ratio of biomass powder to polyphosphonic acid compound at 1:(0.6~0.8), the mixing and impregnation time at 2~6 h, and the first pyrolysis temperature at 400~600 °C for 1~3 h. The present invention has found that these process conditions are also key to ensuring that polyphosphonic acid is efficiently anchored in the carbon skeleton and forms COP bonds. Within this ratio range, polyphosphonic acid can fully penetrate into the biomass and react appropriately with the active sites in the biomass to achieve uniform distribution at the molecular level, while avoiding excessive aggregation due to excessive dosage. The impregnation time is sufficient to ensure the full adsorption and distribution of polyphosphonic acids (PPAs) on the surface and within the pores of biomass. Too short a time will result in uneven PPA distribution, leading to localized enrichment or insufficient coverage, affecting the continuity and uniformity of COP bonds. Too long a time may cause partial dissolution of easily degradable components in the biomass, weakening the precursor structure strength and increasing the risk of structural collapse during subsequent pyrolysis, which is detrimental to the construction of a stable carbon skeleton. The temperature and time of the first pyrolysis stage synergistically control the decomposition and fixation process of PPAs. When the pyrolysis temperature is too low, PPAs undergo dehydration condensation. Insufficient pyrolysis results in a low COP bond formation rate; excessively high pyrolysis temperature (>600℃) leads to the easy loss of phosphate groups in the form of gaseous phosphorus oxides, resulting in severe phosphorus loss. At the same time, excessive graphitization or densification of the carbon skeleton leads to a significant reduction in surface functional groups. Inappropriate control of the process conditions in step (1) will weaken the effective expansion of pores and the removal of inactive phosphorus species during subsequent alkali activation, making it difficult to achieve the synergistic construction of a high specific surface area and uniformly exposed COP functional layer, ultimately seriously affecting the structural performance and adsorption performance of porous biochar adsorbents.

[0035] According to some preferred embodiments, the second pyrolysis involves heating to 600-800°C at a heating rate of 3-10°C / min for 1-3 hours, followed by rapid cooling to 300-400°C at a cooling rate of 15-30°C / min. In this invention, this method is more preferred for the second pyrolysis, as it further enhances the pore structure development and surface functional stability of the porous biochar adsorbent. The second pyrolysis stage, heating to 600-800°C at a rate of 3-10°C / min for 1-3 hours, allows for sufficient and effective interaction between the alkali, carbon framework, and phosphate species. The controlled etching and reconstruction reaction effectively expands the microporous structure and promotes an increase in specific surface area. Subsequently, rapid cooling to 300-400℃ at 15~30℃ / min can quickly cross the temperature window where phosphate grains are prone to migration and aggregation after the high-temperature reaction, effectively inhibiting their recrystallization and agglomeration behavior during the slow cooling process, thereby maintaining the openness of the pores and the high dispersion of phosphorus-containing active sites (such as COP). This is beneficial for obtaining porous biochar adsorbents with higher specific surface area, better pore size distribution and richer stable functional sites, significantly enhancing the adsorption capacity and removal effect of target pollutants.

[0036] According to some preferred embodiments, the specific surface area of ​​the porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and alkali is ≥2200 m². 2 / g; The porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and bases prepared in this invention has a multi-level pore structure with both micropores and mesopores, and its surface contains phosphorus-containing functional groups in the form of COP and / or OP bonds and / or the maximum adsorption capacity of the porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and bases for ciprofloxacin in aqueous solution is ≥500mg / g, the maximum adsorption capacity for paracetamol is ≥250mg / g, and the maximum adsorption capacity for tetracycline is ≥500mg / g.

[0037] According to some preferred embodiments, the porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and alkali has an ultra-high specific surface area and a well-developed microporous-mesoporous hierarchical pore structure, with a specific surface area ≥2900 m². 2 / g; The surface was successfully modified with phosphorus-containing functional groups (such as OP, COP functional groups, etc.); The porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and alkali exhibits excellent adsorption performance for new pollutants such as ciprofloxacin in aqueous solution, with a maximum adsorption capacity of over 750 mg / g, which is much higher than that of biochar modified by single alkali or single inorganic phosphoric acid or polyphosphonic acid compounds. Moreover, it can maintain good adsorption effect in a wide pH range and various actual water matrixes.

[0038] In a second aspect, the present invention provides a porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and alkali, prepared by the preparation method described in the first aspect of the present invention.

[0039] In a third aspect, this invention provides the application of a porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and alkali, prepared by the method described in the first aspect, in the adsorption and removal of quinolone antibiotics, tetracyclic antibiotics, aniline drugs and / or other drug and personal care product pollutants from water. For example, the porous biochar adsorbent can be used to treat wastewater, surface water, groundwater or drinking water containing fluoroquinolone antibiotics such as ciprofloxacin, aniline compounds such as acetaminophen and tetracyclic compounds such as tetracycline, and is particularly suitable for the deep removal of trace antibiotics from hospital wastewater, pharmaceutical wastewater and effluent from urban sewage treatment plants.

[0040] In a fourth aspect, the present invention provides a method for adsorbing and removing pharmaceutical and personal care product contaminants from water bodies. The method involves adding a porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and alkali, prepared by the preparation method described in the first aspect of the present invention, to water bodies containing ciprofloxacin, acetaminophen, and / or tetracycline for adsorption treatment.

[0041] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise specified, all raw materials used in the embodiments of the present invention and comparative examples can be obtained commercially or synthesized by existing methods.

[0042] Example 1 ① After washing the corn stalks, cut them into blocks, then dry, crush and sieve the blocks to obtain biomass powder with a particle size of less than 40 mesh (i.e., it can pass through a 40-mesh sieve).

[0043] ② Biomass powder is mixed with a polyphosphonic acid compound solution (inositol hexaphosphate solution), impregnated, and dried. Then, it undergoes a first pyrolysis and is naturally cooled to room temperature to obtain polyphosphonic acid modified biochar. The polyphosphonic acid compound solution contains 15% polyphosphonic acid compound (inositol hexaphosphate) by mass. The mass ratio of biomass powder to the polyphosphonic acid compound solution is 1:5. The mixing and impregnation are carried out under stirring at a speed of 200 r / min for 4 hours. The drying is performed at 80°C to constant weight. The first pyrolysis is carried out by heating to 500°C at a rate of 5°C / min for 2 hours under a nitrogen atmosphere at a flow rate of 200 mL / min. The natural cooling is performed with continuous nitrogen flow at a flow rate of 200 mL / min.

[0044] ③ The polyphosphonic acid-modified biochar was mixed with an alkaline solution, impregnated, and dried (at 80°C to constant weight). It then underwent a second pyrolysis, naturally cooled to room temperature, and finally acid-washed, water-washed, and dried (at 80°C to constant weight) to obtain a porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and alkali. The alkali in the alkaline solution was potassium hydroxide; the concentration of the alkaline solution (containing potassium hydroxide) was 1 mol / L; the mass ratio of the polyphosphonic acid-modified biochar to the alkali in the alkaline solution was 1:4; the mixing and impregnation were carried out under stirring at a speed of 200 r / min for 1 hour; the second pyrolysis was performed by heating to 700°C at a rate of 5°C / min for 2 hours under a nitrogen atmosphere at a flow rate of 200 mL / min; and the natural cooling was carried out under continuous nitrogen flow at a flow rate of 200 mL / min.

[0045] Example 2 Example 2 is basically the same as Example 1, except that: In step ②, the polyphosphonic acid compound solution used is hexamethylenediaminetetramethylenephosphonic acid solution.

[0046] Example 3 Example 3 is basically the same as Example 1, except that: In step ②, the polyphosphonic acid compound solution used is a 1-hydroxyethylidene-1,1-diphosphonic acid solution.

[0047] Example 4 Example 4 is basically the same as Example 1, except that: In step ②, the polyphosphonic acid compound solution contains a polyphosphonic acid compound (inositol hexaphosphate) with a mass concentration of 5%; the mass ratio of the biomass powder to the polyphosphonic acid compound solution is 1:6; the mixing and impregnation are carried out under stirring conditions, the stirring speed is 200 r / min, the mixing and impregnation time is 6 h, the drying is dried at 80 °C to constant weight, and the first pyrolysis is carried out by heating to 600 °C at a heating rate of 5 °C / min for 1 h, the first pyrolysis is carried out under a nitrogen atmosphere, and the nitrogen flow rate is 200 mL / min.

[0048] In step ③, the concentration of the alkaline solution (containing potassium hydroxide) is 0.5 mol / L; the mass ratio of the polyphosphonic acid modified biochar to the alkali contained in the alkaline solution is 1:5; the mixing and impregnation are carried out under stirring conditions, the stirring speed is 200 r / min, the mixing and impregnation time is 1.5 h, the second pyrolysis is carried out by heating to 800℃ at a heating rate of 5℃ / min for 1 h, the second pyrolysis is carried out under a nitrogen atmosphere, and the nitrogen flow rate is 200 mL / min.

[0049] Example 5 Example 5 is basically the same as Example 1, except that: In step ②, the polyphosphonic acid compound solution contains a polyphosphonic acid compound (inositol hexaphosphate) with a mass concentration of 20%; the mass ratio of the biomass powder to the polyphosphonic acid compound solution is 1:4; the mixing and impregnation are carried out under stirring conditions, the stirring speed is 200 r / min, the mixing and impregnation time is 2 h, the drying is dried at 80°C to constant weight, and the first pyrolysis is carried out by heating to 400°C at a heating rate of 5°C / min for 3 h, the first pyrolysis is carried out under a nitrogen atmosphere, and the nitrogen flow rate is 200 mL / min.

[0050] In step ③, the concentration of the alkaline solution (containing potassium hydroxide) is 2 mol / L; the mass ratio of the polyphosphonic acid modified biochar to the alkali contained in the alkaline solution is 1:2; the mixing and impregnation are carried out under stirring conditions, the stirring speed is 200 r / min, the mixing and impregnation time is 0.5 h, the second pyrolysis is carried out by heating to 600℃ at a heating rate of 5℃ / min for 3 h, the second pyrolysis is carried out under a nitrogen atmosphere, and the nitrogen flow rate is 200 mL / min.

[0051] Example 6 Example 6 is basically the same as Example 1, except that: ② The biomass powder is mixed with a polyphosphonic acid compound solution (inositol hexaphosphate solution), impregnated, and dried. Then, it undergoes a first pyrolysis and is naturally cooled to room temperature to obtain polyphosphonic acid modified biochar. The polyphosphonic acid compound solution contains 15% polyphosphonic acid compound (inositol hexaphosphate) by mass. The amount of polyphosphonic acid compound solution used is such that the mass ratio of the biomass powder to the inositol hexaphosphate contained in the polyphosphonic acid compound solution is 1:0.4. The mixing and impregnation are carried out under stirring at a speed of 200 r / min for 1 hour. The drying is carried out at 80°C to constant weight. The first pyrolysis is carried out by heating to 300°C at a rate of 5°C / min for 2 hours under a nitrogen atmosphere at a flow rate of 200 mL / min. The natural cooling is carried out under continuous nitrogen flow at a flow rate of 200 mL / min.

[0052] Example 7 Example 7 is basically the same as Example 1, except that: ② Biomass powder is mixed with a polyphosphonic acid compound solution (inositol hexaphosphate solution), impregnated, and dried. Then, it undergoes a first pyrolysis and is naturally cooled to room temperature to obtain polyphosphonic acid modified biochar. The polyphosphonic acid compound solution contains 15% polyphosphonic acid compound (inositol hexaphosphate) by mass. The amount of polyphosphonic acid compound solution used is such that the mass ratio of biomass powder to inositol hexaphosphate in the polyphosphonic acid compound solution is 1:1. The mixing and impregnation are carried out under stirring at a speed of 200 r / min for 8 hours. The drying is carried out at 80°C to constant weight. The first pyrolysis is performed by heating to 700°C at a rate of 5°C / min for 2 hours under a nitrogen atmosphere at a flow rate of 200 mL / min. The natural cooling is carried out under continuous nitrogen flow at a flow rate of 200 mL / min.

[0053] Example 8 Example 8 is basically the same as Example 1, except that: ③ The polyphosphonic acid-modified biochar was mixed with an alkaline solution, impregnated, and dried (at 80°C to constant weight). It then underwent a second pyrolysis, naturally cooled to room temperature, and finally acid-washed, water-washed, and dried (at 80°C to constant weight) to obtain a porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and alkali. The alkali in the alkaline solution was potassium hydroxide; the concentration of the alkaline solution (containing potassium hydroxide) was 1 mol / L; the mass ratio of the polyphosphonic acid-modified biochar to the alkali in the alkaline solution was 1:1; the mixing and impregnation were carried out under stirring at a speed of 200 r / min for 10 min; the second pyrolysis was performed by heating to 700°C at a rate of 5°C / min for 2 h under a nitrogen atmosphere at a flow rate of 200 mL / min; and the natural cooling was carried out under continuous nitrogen flow at a flow rate of 200 mL / min.

[0054] Example 9 Example 9 is basically the same as Example 1, except that: ③ The polyphosphonic acid-modified biochar was mixed with an alkaline solution, impregnated, and dried (at 80°C to constant weight). Then, it underwent a second pyrolysis, naturally cooled to room temperature, and finally acid-washed, water-washed, and dried (at 80°C to constant weight) to obtain a porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and alkali. The alkali in the alkaline solution was potassium hydroxide; the concentration of the alkaline solution (containing potassium hydroxide) was 1 mol / L; the mass ratio of the polyphosphonic acid-modified biochar to the alkali in the alkaline solution was 1:6; the mixing and impregnation were carried out under stirring at a speed of 200 r / min for 6 h; the second pyrolysis was performed by heating to 700°C at a rate of 5°C / min for 2 h under a nitrogen atmosphere at a flow rate of 200 mL / min; and the natural cooling was carried out under continuous nitrogen flow at a flow rate of 200 mL / min.

[0055] Example 10 Example 10 is basically the same as Example 1, except that: ③ The polyphosphonic acid-modified biochar was mixed with an alkaline solution, impregnated, and dried (at 80°C to constant weight). It then underwent a second pyrolysis, naturally cooled to room temperature, and finally acid-washed, water-washed, and dried (at 80°C to constant weight) to obtain a porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and alkali. The alkali in the alkaline solution was potassium hydroxide; the concentration of the alkaline solution (containing potassium hydroxide) was 1 mol / L; the mass ratio of the polyphosphonic acid-modified biochar to the alkali in the alkaline solution was 1:4; the mixing and impregnation were carried out under stirring conditions. The rotation speed is 200 r / min, the mixing and impregnation time is 1 h, the second pyrolysis is to heat to 700°C at a heating rate of 5°C / min and pyrolyze for 2 h, and then rapidly cool to 400°C at a cooling rate of 20°C / min. The second pyrolysis is carried out under a nitrogen atmosphere with a nitrogen flow rate of 200 mL / min. In this embodiment, after rapidly cooling to 400°C at a cooling rate of 20°C / min, natural cooling to room temperature is carried out. The natural cooling is carried out under continuous nitrogen supply with a nitrogen flow rate of 200 mL / min.

[0056] Comparative Example 1 ① After washing the corn stalks, cut them into blocks, then dry, crush and sieve the blocks to obtain biomass powder with a particle size of less than 40 mesh (i.e., it can pass through a 40-mesh sieve).

[0057] ② A mixture of biomass powder, polyphosphonic acid compound solution (inositol hexaphosphate solution), and alkaline solution is impregnated and dried. The mixture is then pyrolyzed, naturally cooled to room temperature, and finally acid-washed, water-washed, and dried (at 80°C to constant weight) to obtain a modified biochar adsorbent. The polyphosphonic acid compound solution contains 15% polyphosphonic acid compound (inositol hexaphosphate) by mass. The mass ratio of biomass powder to the polyphosphonic acid compound solution is 1:5. The concentration of the alkaline solution (containing potassium hydroxide) is 1 mol / L. The mass ratio of the biomass powder to the alkali in the alkaline solution is 1:4; the mixing and impregnation are carried out under stirring conditions at a stirring speed of 200 r / min, the mixing and impregnation time is 4 h, the drying is carried out at 80 °C to constant weight, the pyrolysis is carried out by heating to 500 °C at a heating rate of 5 °C / min for 2 h, the pyrolysis is carried out under a nitrogen atmosphere at a nitrogen flow rate of 200 mL / min, and the natural cooling is carried out under continuous nitrogen supply at a nitrogen flow rate of 200 mL / min.

[0058] Comparative Example 2 ① After washing the corn stalks, cut them into blocks, then dry, crush and sieve the blocks to obtain biomass powder with a particle size of less than 40 mesh (i.e., it can pass through a 40-mesh sieve).

[0059] ② The biomass powder is mixed with a polyphosphonic acid compound solution (inositol hexaphosphate solution) and an alkaline solution, impregnated, and dried. Then, it is pyrolyzed, naturally cooled to room temperature, and finally acid-washed, water-washed, and dried (at 80°C to constant weight) to obtain a modified biochar adsorbent. The polyphosphonic acid compound solution contains 15% polyphosphonic acid compound (inositol hexaphosphate) by mass. The mass ratio of the biomass powder to the polyphosphonic acid solution is 1:5. The alkaline solution contains potassium hydroxide. The concentration of the alkaline solution (containing potassium hydroxide) is... The concentration is 1 mol / L; the mass ratio of the biomass powder to the alkali in the alkaline solution is 1:4; the mixing and impregnation are carried out under stirring conditions at a stirring speed of 200 r / min, the mixing and impregnation time is 1 h, the drying is carried out at 80℃ to constant weight, the pyrolysis is carried out by heating to 700℃ at a heating rate of 5℃ / min for 2 h, the pyrolysis is carried out under a nitrogen atmosphere at a nitrogen flow rate of 200 mL / min, and the natural cooling is carried out under continuous nitrogen supply at a nitrogen flow rate of 200 mL / min.

[0060] In Comparative Examples 1 and 2 of this invention, polyphosphonic acid and alkali were used for simultaneous modification, which resulted in mutual interference in the modification process, leading to very poor results and a significant decrease in adsorption capacity.

[0061] Comparative Example 3 Comparative Example 3 is basically the same as Example 1, except that: ② The biomass powder was mixed with and impregnated with a phosphoric acid solution and dried, then subjected to a first pyrolysis and naturally cooled to room temperature to obtain phosphoric acid modified biochar; the phosphoric acid solution contained 15% phosphoric acid by mass; the mass ratio of the biomass powder to the phosphoric acid solution was 1:5; the mixing and impregnation were carried out under stirring at a speed of 200 r / min for 4 h; the drying was carried out at 80 °C to constant weight; the first pyrolysis was carried out by heating to 500 °C at a heating rate of 5 °C / min for 2 h; the first pyrolysis was carried out under a nitrogen atmosphere at a flow rate of 200 mL / min; the natural cooling was carried out under continuous nitrogen supply at a flow rate of 200 mL / min; this comparative example uses this phosphoric acid modified biochar to replace the polyphosphonic acid modified biochar in Example 1 for subsequent steps ③.

[0062] This comparative example uses phosphoric acid for modification, followed by alkali activation treatment. The specific surface area obtained in this comparative example is low, and the adsorption performance decreases by more than 50%.

[0063] Comparative Example 4 ① After washing the corn stalks, cut them into blocks, then dry, crush and sieve the blocks to obtain biomass powder with a particle size of less than 40 mesh (i.e., it can pass through a 40-mesh sieve).

[0064] ② Biomass powder was mixed with a polyphosphonic acid compound solution (inositol hexaphosphate solution), impregnated, and dried. The mixture was then pyrolyzed, naturally cooled to room temperature, washed with water (deionized water until neutral), and dried (at 80°C to constant weight) to obtain polyphosphonic acid-modified biochar as a porous biochar adsorbent. The polyphosphonic acid compound solution contained 15% polyphosphonic acid compound (inositol hexaphosphate) by mass. The mass ratio of biomass powder to the polyphosphonic acid compound solution was 1:5. The mixing and impregnation were carried out under stirring at a speed of 200 r / min for 4 hours. The drying was carried out at 80°C to constant weight. The pyrolysis was performed by heating to 500°C at a rate of 5°C / min for 2 hours under a nitrogen atmosphere at a flow rate of 200 mL / min. The natural cooling was carried out under continuous nitrogen flow at a flow rate of 200 mL / min.

[0065] Comparative Example 4 only used inositol hexaphosphate for modification, and the specific surface area of ​​the resulting polyphosphonic acid-modified biochar was reduced to only 348 m². 2 / g, with a pore volume of only 0.27cm³. 3 / g, the adsorption capacity decreases by about 60%-70%, because the porous biochar adsorbent lacks micropores in its structure.

[0066] Comparative Example 5 ① After washing the corn stalks, cut them into blocks, then dry, crush and sieve the blocks to obtain biomass powder with a particle size of less than 40 mesh (i.e., it can pass through a 40-mesh sieve).

[0067] ② The biomass powder is mixed with an alkaline solution, impregnated, and dried (at 80°C to constant weight). Then, it undergoes pyrolysis, natural cooling to room temperature, and finally acid washing, water washing, and drying (at 80°C to constant weight) to prepare a porous biochar adsorbent. The alkaline solution contains potassium hydroxide; the concentration of the alkaline solution (containing potassium hydroxide) is 1 mol / L; the mass ratio of the biomass powder to the alkaline solution is 1:4; the mixing and impregnation are carried out under stirring at a speed of 200 r / min for 1 hour; the pyrolysis is performed by heating to 700°C at a rate of 5°C / min for 2 hours under a nitrogen atmosphere at a flow rate of 200 mL / min; and the natural cooling is carried out under continuous nitrogen flow at a flow rate of 200 mL / min.

[0068] The porous biochar adsorbent prepared in Comparative Example 5 was activated only with potassium hydroxide, resulting in a specific surface area reduction to 1800 m². 2 / g, with a pore volume of only 0.84cm³. 3 / g, the adsorption capacity decreased significantly, and the porous biochar adsorbent structure lacks mesoporous and COP functional layers.

[0069] Comparative Example 6 ① After washing the corn stalks, cut them into blocks, then dry, crush and sieve the blocks to obtain biomass powder with a particle size of less than 40 mesh (i.e., it can pass through a 40-mesh sieve).

[0070] ② The biomass powder is mixed with an alkaline solution, impregnated, and dried (drying at 80℃ to constant weight), then subjected to a first pyrolysis and naturally cooled to room temperature to obtain alkaline-activated biochar; the alkaline solution contains potassium hydroxide; the concentration of the alkaline solution (containing potassium hydroxide) is 1 mol / L; the mass ratio of the biomass powder to the alkaline solution is 1:4; the mixing and impregnation are carried out under stirring conditions, the stirring speed is 200 r / min, the mixing and impregnation time is 1 h, the pyrolysis is carried out by heating to 700℃ at a heating rate of 5℃ / min for 2 h, the pyrolysis is carried out under a nitrogen atmosphere, the nitrogen flow rate is 200 mL / min, and the natural cooling is carried out under continuous nitrogen supply, the nitrogen flow rate is 200 mL / min.

[0071] ③ The alkali-activated biochar was mixed with a polyphosphonic acid compound solution (inositol hexaphosphate solution), impregnated, and dried (drying at 80°C to constant weight). Then, it underwent a second pyrolysis, naturally cooled to room temperature, and was washed with water (deionized water until neutral) and dried (at 80°C to constant weight) to obtain a modified biochar adsorbent. The polyphosphonic acid compound solution contained 15% polyphosphonic acid compound (inositol hexaphosphate) by mass. The mass ratio of the alkali-activated biochar to the polyphosphonic acid compound solution was 1:5. The mixing and impregnation were carried out under stirring at a speed of 200 r / min for 4 hours. The second pyrolysis was performed by heating to 500°C at a rate of 5°C / min for 2 hours under a nitrogen atmosphere at a flow rate of 200 mL / min. The natural cooling was carried out under continuous nitrogen flow at a flow rate of 200 mL / min.

[0072] In this comparative example, the biochar adsorbent was first activated with alkali and then modified with inositol hexaphosphate, resulting in a decrease in the specific surface area of ​​the modified biochar adsorbent to only 500 m². 2 / g, with a pore volume of only 0.42cm³. 3 / g, the adsorption capacity decreases by about 50-60%, the micropores are blocked, and there are fewer surface active sites.

[0073] Comparative Example 7 Comparative Example 7 is basically the same as Example 1, except that: ③ The polyphosphonic acid-modified biochar was mixed with an alkaline solution and impregnated for 6 hours, then washed multiple times with deionized water until neutral, and then dried at 80°C to constant weight to obtain an alkaline-treated modified biochar adsorbent; the alkaline solution contained potassium hydroxide; the concentration of the alkaline solution (containing potassium hydroxide) was 1 mol / L; the ratio of the amount of polyphosphonic acid-modified biochar to the amount of alkaline solution contained in the alkaline solution was 500 mg: 0.05 mol; the mixing and impregnation were carried out under stirring conditions, and the stirring speed was 200 r / min.

[0074] Comparative Example 8 ① After washing the corn stalks, cut them into blocks, then dry, crush and sieve the blocks to obtain biomass powder with a particle size of less than 40 mesh (i.e., it can pass through a 40-mesh sieve).

[0075] ② Weigh 5g of biomass powder and 5g of citric acid and grind them in an agate mortar until they are evenly mixed. Place the ground mixture into a crucible. Then place it in a muffle furnace and heat it to 500℃ and maintain it for 3 hours. Grind the pyrolysis sample appropriately and package it for later use.

[0076] ③ Take 500 mg of sample and stir it in 50 mL of 1 mol / L NaOH solution with a magnetic stirrer for 6 h. Then wash it several times with deionized water until neutral. Place it in an 80℃ forced-air drying oven and dry it to constant weight to obtain alkali-treated modified biochar adsorbent. Finally, grind it evenly, package it, dry it and store it for later use.

[0077] The specific surface area, pore volume, and adsorption performance (maximum adsorption capacity) of the biochar adsorbents finally prepared in each embodiment and comparative example were tested, and the results are shown in Table 1. The adsorption performance test was conducted by treating 1000 mL of water containing 100 mg / L ciprofloxacin (50 mg), 1000 mL of water containing 100 mg / L paracetamol (50 mg), and 1000 mL of water containing 100 mg / L tetracycline (50 mg) at 25 °C. After adsorption equilibrium was reached, the adsorption capacity (maximum adsorption capacity) results were measured, and the results are shown in Table 1.

[0078] Table 1 In Table 1, the symbol "-" indicates that the performance metric was not tested.

[0079] SEM images of the biochar adsorbents prepared in Examples 1, 4, and 5 of this invention are shown below. Figure 1As shown; A is a SEM image of corn straw biochar. In this invention, the preparation of corn straw biochar is as follows: ① After washing the corn straw, it is cut into blocks, and then the blocks are dried, crushed, and sieved to obtain biomass powder with a particle size of less than 40 mesh (i.e., it can pass through a 40-mesh sieve). ② The biomass powder is subjected to a first pyrolysis and a second pyrolysis, and then naturally cooled to room temperature to obtain corn straw biochar; the first pyrolysis is carried out by heating to 500℃ at a heating rate of 5℃ / min for 2 hours, and the first pyrolysis is carried out under a nitrogen atmosphere with a nitrogen flow rate of 200 mL / min; the second pyrolysis is carried out by heating to 700℃ at a heating rate of 5℃ / min for 2 hours, and the second pyrolysis is carried out under a nitrogen atmosphere with a nitrogen flow rate of 200 mL / min; the natural cooling is carried out under continuous nitrogen supply with a nitrogen flow rate of 200 mL / min. Figure 1 E in the image represents the SEM-EDS image of the porous biochar adsorbent sample prepared in Example 1, showing the distribution of each element on the material surface. It demonstrates that the distribution of P and C elements is similar, both being relatively uniformly distributed on the surface without significant accumulation to form particles. The TEM image of the porous biochar adsorbent prepared in Example 1 of this invention is shown below. Figure 2 As shown, from Figure 2 It can be seen that the porous biochar adsorbent sample prepared in Example 1 has a porous structure and abundant mesopores. Figure 1 Combination Figure 2 The TEM images show that P is relatively uniformly distributed on the material surface; the adsorption performance test results of the biochar adsorbents prepared in Examples 1, 4, and 5 of this invention for ciprofloxacin are as follows: Figure 3 As shown, from Figure 3 The results from B show that, when the porous biochar adsorbent prepared by this invention adsorbs and removes pharmaceutical and personal care product pollutants (such as ciprofloxacin) from water, the preferred dosage is 40-120 mg / L; from Figure 3 Results C and D show that the porous biochar adsorbent prepared by this invention has excellent resistance to acid and alkali interference and ion interference. The nitrogen adsorption-desorption curves and pore size distribution diagrams of the porous biochar adsorbent prepared in Example 1 of this invention are shown below. Figure 4 As shown, Figure 4 This also demonstrates that the porous biochar adsorbent prepared by this invention has a multi-level pore structure with both micropores and mesopores; XPS comparison images of the biochar adsorbents prepared in Example 1 and Comparative Example 4 of this invention are shown below. Figure 5 As shown; from Figure 5The results demonstrate that alkali activation causes the biochar adsorbent to shift from being dominated by phosphorus-containing functional groups (OP) to being dominated by COP. This is primarily because the alkali causes controlled breakage of some COP bonds, thereby moderately weakening the binding force between phosphate particles and the carbon surface, promoting the detachment of some phosphate particles (after the phosphate particles detach, both OP and COP functional groups decrease, with OP decreasing more significantly). This not only removes excess deposits that might clog the pores but also better preserves the uniformly dispersed phosphorus-containing active functional groups (COP); and further... Figure 1 , Figure 2 and Figure 5 Combining Figure B with the above, it can be seen that P mainly exists as a COP layer uniformly spread and bonded to the material surface. The XPS spectra of the biochar adsorbents prepared in Examples 1, 4, and 5 of this invention are shown below. Figure 6 As shown, from Figure 6 Comparison of XPS total spectra of various materials proves that the surface P content increases significantly after modification with polyphosphonic acid, and then the P content decreases significantly after alkali activation.

[0080] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and alkali, characterized in that, The method includes the following steps: (1) The biomass powder was mixed with a polyphosphonic acid compound solution, impregnated and dried, and then subjected to a first pyrolysis to obtain polyphosphonic acid modified biochar; (2) The polyphosphonic acid modified biochar was mixed with an alkaline solution, impregnated and dried, then subjected to a second pyrolysis, and finally acid washing, water washing and drying to obtain a porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compound and alkali.

2. The preparation method according to claim 1, characterized in that, In step (1): The biomass powder is obtained from lignocellulosic biomass through washing, cutting, drying, crushing and sieving; Preferably, the lignocellulosic biomass is one or more of agricultural and forestry waste, grass leaves, and wood materials; more preferably, the lignocellulosic biomass is one or more of corn cobs, straw, grass leaves, fruit shells, and wood materials; and even more preferably, the lignocellulosic biomass is corn straw.

3. The preparation method according to claim 1, characterized in that, In step (1): The polyphosphonic acid compound solution contains one or more of the following: hexamethylenediaminetetramethylenephosphonic acid, hexamethylenediaminetetramethylenephosphonate, 1-hydroxyethylidene-1,1-diphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonate, inositol hexaphosphate, and inositol hexaphosphate.

4. The preparation method according to claim 1, characterized in that, In step (1): The polyphosphonic acid compound solution contains a polyphosphonic acid compound with a mass concentration of 5-20%, preferably 15%; The mass ratio of the biomass powder to the polyphosphonic acid compound solution is 1:(4~6); and / or The mixing and impregnation time is 2-6 hours.

5. The preparation method according to claim 1, characterized in that, In step (2): The alkaline solution contains sodium hydroxide and / or potassium hydroxide; The concentration of the alkaline solution is 0.5~1.5 mol / L; The mass ratio of the polyphosphonic acid-modified biochar to the alkali contained in the alkaline solution is 1:(2~5); and / or The mixing and impregnation time is 0.5~1.5h.

6. The preparation method according to claim 1, characterized in that: The first pyrolysis and / or the second pyrolysis are carried out under an inert atmosphere; The first pyrolysis is performed at a temperature of 400~600℃ for a time of 1~3 hours; and / or The second pyrolysis temperature is 600~800℃, and the time is 1~3h.

7. The preparation method according to claim 1, characterized in that: The porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and alkali has a specific surface area ≥2200 m². 2 / g; and / or The porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and alkali has a maximum adsorption capacity of ≥500 mg / g for ciprofloxacin in aqueous solution, a maximum adsorption capacity of ≥250 mg / g for paracetamol, and a maximum adsorption capacity of ≥500 mg / g for tetracycline.

8. A porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and alkali, prepared by the method according to any one of claims 1 to 7.

9. The use of the porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and alkali prepared by any one of claims 1 to 7 in the adsorption and removal of quinolone antibiotics, tetracyclic antibiotics, aniline drugs and / or other drug and personal care product pollutants in water.

10. A method for adsorbing and removing pharmaceutical and personal care product contaminants from water, characterized in that, The method is as follows: adding a porous biochar adsorbent based on the synergistic modification of polyphosphonic acid compounds and alkali, prepared by any one of claims 1 to 7, to water containing ciprofloxacin, acetaminophen, and / or tetracycline for adsorption treatment.

Images