A lignin-based iron-carbon composite material, its preparation method and application

Abstract

This invention belongs to the field of advanced oxidation treatment technology for organic polluted water, specifically relating to a lignin-based iron-carbon composite material, its preparation method, and its application. The lignin-based iron-carbon composite material provided by this invention comprises lignin-based porous carbon and nanoparticles supported on the surface and pores of the lignin-based porous carbon; the nanoparticles are iron carbide coated with zero-valent iron; the lignin-based porous carbon has a porous graphitized carbon structure. This lignin-based iron-carbon composite material can effectively adsorb benzene series compounds and their complex pollutants in water, and can also act as a catalyst to activate persulfate for efficient and stable removal of benzene series compounds and their complex pollutants from water.

Description

Technical Field

[0001] This invention belongs to the field of advanced oxidation treatment technology for organic polluted water bodies, specifically relating to a lignin-based iron-carbon composite material, its preparation method, and its application. Background Technology

[0002] Benzene compounds are typical volatile organic pollutants found in groundwater contaminated with petroleum hydrocarbons and other organic pollutants. They often form complex pollution with polycyclic aromatic hydrocarbons (PAHs), chlorobenzene, and other aromatic compounds, posing a serious threat to human health and the ecological environment. Specifically, benzene compounds, PAHs, and chlorobenzene are aromatic compounds with a benzene ring as their core structure. They are highly toxic and volatile, and ingestion or inhalation can damage the kidneys, liver, and nervous system, and may even pose potential carcinogenic, teratogenic, and mutagenic hazards. Therefore, there is an urgent need to develop green and efficient technologies for the remediation of benzene compounds and their complex organic pollutants in groundwater.

[0003] Currently, the main technologies used to treat benzene series compounds and their complex pollutants in groundwater include in-situ thermal desorption, adsorption, microbial remediation, and advanced oxidation technologies. Among these, advanced oxidation technologies are characterized by high efficiency and thoroughness, being green and low-carbon, having a wide range of applications, and low equipment requirements. Traditional homogeneous iron-based transition metal homogeneous activation systems suffer from drawbacks such as severe non-productive side reactions, a narrow pH range, easy formation of iron sludge, and insufficient long-term effectiveness, resulting in low removal efficiency of benzene series compounds and their complex pollutants in water. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a lignin-based iron-carbon composite material, its preparation method and application. The lignin-based iron-carbon composite material provided by the present invention can effectively adsorb benzene series compounds and their complex pollutants in water, and can also act as a catalyst to activate persulfate to efficiently and stably remove benzene series compounds and their complex pollutants from water.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a lignin-based iron-carbon composite material, comprising lignin-based porous carbon and nanoparticles supported on the surface and pores of the lignin-based porous carbon; The nanoparticles are iron carbide coated with zero-valent iron. The lignin-based porous carbon has a porous graphitized carbon structure.

[0006] Preferably, the specific surface area of ​​the lignin-based iron-carbon composite material is 138~340 m². 2 / g, pore volume is 0.05~0.1cm³ 3 / g; the particle size of the iron carbide coated with zero-valent iron is 10~100nm.

[0007] This invention also provides a method for preparing the lignin-based iron-carbon composite material described in the above technical solution, comprising the following steps: A lignin-containing solution, inorganic iron salt, and inorganic zinc salt were mixed, allowed to stand and age, and then the solid and liquid were separated to obtain a precipitate. The precipitate was calcined in a protective gas to obtain the lignin-based iron-carbon composite material.

[0008] Preferably, the lignin is alkaline lignin.

[0009] Preferably, the concentration of lignin in the lignin-containing solution is 5~20 g / L.

[0010] Preferably, the molar ratio of Fe in the inorganic iron salt to Zn in the inorganic zinc salt is 1:1~5.

[0011] Preferably, the calcination includes sequentially performing low-temperature calcination and high-temperature calcination; the low-temperature calcination temperature is 350~550℃, and the holding time is 1~2h; the high-temperature calcination temperature is 900~1000℃, and the holding time is 1~4h.

[0012] Preferably, the heating rate from room temperature to the low-temperature calcination temperature is 5~10℃ / min; the heating rate from the low-temperature calcination temperature to the high-temperature calcination temperature is 2~5℃ / min.

[0013] The present invention also provides the application of the lignin-based iron-carbon composite material described in the above technical solution or the lignin-based iron-carbon composite material prepared by the preparation method described in the above technical solution in the treatment of benzene series compounds and their composite pollutants in water bodies; The applications include: using lignin-based iron-carbon composite materials to adsorb benzene compounds and their complex pollutants in water; or using lignin-based iron-carbon composite materials to activate persulfate to degrade benzene compounds and their complex pollutants in water.

[0014] Preferably, the benzene series compounds and their complex pollutants include one or more of benzene, p-xylene, chlorobenzene, and naphthalene; the concentration of each pollutant in the water body is independently 1~10 mg / L; the concentration of persulfate in the water body containing benzene series compounds and their complex pollutants is 1~10 mM; and the concentration of the lignin-based iron-carbon composite material in the water body containing benzene series compounds and their complex pollutants is 0.4~4 g / L.

[0015] This invention provides a lignin-based iron-carbon composite material, comprising lignin-based porous carbon and nanoparticles supported on the surface and pores of the lignin-based porous carbon; the nanoparticles are iron carbide coated with zero-valent iron; the lignin-based porous carbon has a porous graphitized carbon structure. The lignin-based iron-carbon composite material provided by this invention has a porous graphitized carbon structure and exhibits strong adsorption capacity for benzene compounds and other organic pollutants (chlorobenzene, naphthalene). Furthermore, it possesses multiple active sites in graphitized carbon, zero-valent iron, and iron carbide, which can activate persulfate to generate sulfate radicals, hydroxyl radicals, singlet oxygen, and other strong oxidizing substances, effectively degrading benzene compounds and their complex pollutants in water. Zero-valent iron alone readily undergoes a direct dissolution reaction with water, causing iron dissolution and resulting in the loss of iron reaction sites. In this invention, the iron carbide coating zero-valent iron in the porous carbon pores provides good protection for the zero-valent iron and can effectively prevent the loss of iron reaction sites through water dissolution reaction. Furthermore, the strong adsorption effect of porous carbon is more conducive to the efficient and continuous activation of persulfate degradation of various organic pollutants. Attached Figure Description

[0016] Figure 1 A scanning electron microscope image of the lignin-based iron-carbon composite material prepared in Example 1; Figure 2 Transmission electron microscopy image of the lignin-based iron-carbon composite material prepared in Example 1; Figure 3 The XRD pattern of the lignin-based iron-carbon composite material prepared in Example 1; Figure 4 The images show the effect of lignin-based iron-carbon composite material prepared in Example 1 on the removal of benzene series compounds and their composite pollutants by activated persulfate. Among them, (a) is the benzene-p-xylene composite system, (b) is the benzene-chlorobenzene composite system, (c) is the benzene-naphthalene composite system, and (d) is the single pollutant system. Detailed Implementation

[0017] This invention provides a lignin-based iron-carbon composite material, comprising lignin-based porous carbon and nanoparticles supported on the surface and pores of the lignin-based porous carbon; The nanoparticles are iron carbide coated with zero-valent iron. The lignin-based porous carbon has a porous graphitized carbon structure.

[0018] Unless otherwise specified, the present invention does not have special requirements on the source of raw materials used, and commercially available products well known to those skilled in the art can be used.

[0019] In one embodiment, the specific surface area of ​​the lignin-based iron-carbon composite material is 138~340 m². 2 / g, pore volume is 0.05~0.1cm³ 3 / g; the particle size of the iron carbide coated with zero-valent iron is 10~100nm; the total iron content in the lignin-based iron-carbon composite material is 59.7wt%.

[0020] Lignin, rich in functional groups, can tightly complex metal ions (iron) through coordination bonds, facilitating the formation of stable iron-carbon composite materials. Furthermore, during the composite material preparation process, the tightly bound iron-based metal simultaneously catalyzes the graphitization and defect transformation of lignin, enabling it to engage in π-π and hydrophobic interactions with aromatic pollutants such as benzene compounds, polycyclic aromatic hydrocarbons, and chlorobenzene, thereby enhancing the adsorption, enrichment, and subsequent degradation and removal of these pollutants. The lignin-based iron-carbon composite material provided by this invention can serve as a catalyst for activating persulfate, achieving highly efficient removal of benzene compounds and their complex pollutants from water bodies (groundwater).

[0021] This invention also provides a method for preparing the lignin-based iron-carbon composite material described in the above technical solution, comprising the following steps: A lignin-containing solution, inorganic iron salt, and inorganic zinc salt were mixed, allowed to stand and age, and then the solid and liquid were separated to obtain a precipitate. The precipitate was calcined in a protective gas to obtain the lignin-based iron-carbon composite material.

[0022] This invention involves mixing a lignin-containing solution, an inorganic iron salt, and an inorganic zinc salt, allowing them to stand and age, and then separating the solid and liquid phases to obtain a precipitate.

[0023] In one embodiment, the lignin is alkaline lignin; the inorganic iron salt includes one or more of ferric nitrate, ferric sulfate, and ferric chloride, with ferric nitrate being the specific embodiment; the inorganic zinc salt includes one or more of zinc nitrate, zinc sulfate, and zinc chloride, with zinc nitrate being the specific embodiment.

[0024] Lignin is the only renewable aromatic resource in nature, possessing abundant aromatic functional groups (phenolic hydroxyl groups), which facilitates its tight complexation with metal ions (ferric ions). The resulting iron-carbon composite materials exhibit high stability and low iron leaching during material application. Furthermore, the carbonization products of lignin are highly graphitized, which can enhance the adsorption, enrichment, degradation, and removal of aromatic organic pollutants (benzene compounds).

[0025] The lignin described in this invention is alkaline lignin, which exhibits excellent dispersibility and solubility in water. This facilitates thorough mixing with metal ions (iron ions) during the preparation of iron-carbon composite materials, forming a homogeneous aqueous solution. Consequently, the zero-valent iron and other nanoparticles in the resulting iron-carbon composite material are also uniformly dispersed, resulting in materials with high stability and activity. Although many biomass materials in the natural environment have a lignin content exceeding 30% (such as coconut shells, walnut shells, pine wood, oak, and bamboo), the lignin in these natural biomass typically has poor water solubility and contains many impurities, negatively impacting the performance of the final iron-carbon composite material. Therefore, the alkaline lignin used in this invention cannot be directly replaced by other biomass materials with high lignin content.

[0026] Ordinary lignin is usually a byproduct dissolved during the papermaking and pulping process, obtained through simple acid precipitation and washing. Basic lignin, on the other hand, is often obtained by maintaining an alkaline environment or by further alkaline treatment of ordinary lignin. Basic lignin has higher purity, smaller molecular weight, and excellent water solubility, which is beneficial for the thorough mixing of basic lignin with metal ions such as iron during the preparation of iron-carbon composites, forming a homogeneous aqueous solution. This facilitates the uniform distribution of iron-based nanoparticles in the final iron-carbon composite material.

[0027] In one embodiment, the concentration of lignin in the lignin-containing solution is 5~20 g / L, and in a specific embodiment it is 8 g / L; the concentration of inorganic iron salt in the lignin-containing solution is 3~9 g / L, and in a specific embodiment it is 8 g / L; the molar ratio of Fe in the inorganic iron salt to Zn in the inorganic zinc salt is 1:1~5, and in a specific embodiment it is 1:1.

[0028] When the lignin concentration is too low, the zero-valent iron-coated iron carbide nanoparticles in the composite material tend to agglomerate; when the lignin concentration is too high, the zero-valent iron / iron carbide nanoparticles tend to be distributed in excessive carbon pore structures. Both hinder the contact reaction between the active sites of iron-based metals and pollutants or oxidants, ultimately reducing the overall reactivity of the material.

[0029] The higher the molar ratio of Fe to Zn and the lower the zinc content, the fewer pore structures are in the final material. As a result, iron carbide-coated zero-valent iron nanoparticles are more likely to aggregate, reducing the reactivity of lignin-based iron-carbon composites.

[0030] As one embodiment, the method for preparing the lignin-containing solution is as follows: dissolve lignin in water and perform a first stirring to obtain a lignin-containing solution; the temperature of the first stirring is room temperature, the speed is 100~300 rpm, in a specific embodiment it is 300 rpm, the time is 0.5~3h, in a specific embodiment it is 1~2h; the water is ultrapure water.

[0031] In one embodiment, the mixing of the lignin-containing solution, inorganic iron salt, and inorganic zinc salt is as follows: the inorganic iron salt and inorganic zinc salt are dissolved in the lignin-containing solution, and a second stirring is performed; the temperature of the second stirring is room temperature, the speed is 100~300 rpm, in a specific embodiment it is 300 rpm, and the time is 0.5~3h, in a specific embodiment it is 1~2h.

[0032] In one implementation method, the static aging time is 8-12 hours, and in a specific embodiment, it is 10-12 hours. The purpose of static aging overnight is to convert the metal ions (iron, zinc) complexed with lignin into metal oxides, so that they can form a precipitate together with lignin and undergo subsequent calcination reactions.

[0033] In one implementation, the solid-liquid separation is centrifugation; the centrifugation speed is 4000~10000 rpm, 5000 rpm in a specific embodiment, and the time is 10~30 min, 10~20 min in a specific embodiment.

[0034] In one embodiment, after solid-liquid separation, the method further includes: washing, drying, grinding into powder, and sieving the precipitate obtained from the solid-liquid separation to obtain powder; the washing is water washing; the reagent used for water washing is ultrapure water; the number of washing cycles is 3 to 5 times, specifically 3 times in this embodiment; the drying temperature is 60 to 80°C, specifically 80°C in this embodiment, and the drying time is 6 to 12 hours, specifically 12 hours in this embodiment; the drying is vacuum drying; the vacuum degree of the vacuum drying is 0.001 to 0.01 Pa, specifically 0.01 Pa in this embodiment; the sieve used for sieving has an aperture of 100 to 200 mesh, specifically 200 mesh in this embodiment; the particle size range of the powder is 74 to 175 μm, specifically 74 μm in this embodiment. Smaller powder particle size is more conducive to the carbonization reaction of lignin catalyzed by iron ions and the formation of nano-zero valent iron and iron carbide during subsequent calcination; however, if the powder particle size is too small, zero valent iron and iron carbide will easily agglomerate, which will ultimately reduce the activity of the composite material.

[0035] After obtaining the precipitate, the present invention calcines the precipitate in a protective gas to obtain the lignin-based iron-carbon composite material.

[0036] In one embodiment, the protective gas is nitrogen; the calcination includes sequential low-temperature calcination and high-temperature calcination; the low-temperature calcination temperature is 350~550℃, specifically 400~550℃ in this embodiment, and the holding time is 1~2h, specifically 1h in this embodiment; the heating rate from room temperature to the low-temperature calcination temperature is 5~10℃ / min, specifically 5℃ / min in this embodiment; the high-temperature calcination temperature is 900~1000℃, specifically 950℃ in this embodiment, and the holding time is 1~4h, specifically 1h in this embodiment; the heating rate from the low-temperature calcination temperature to the high-temperature calcination temperature is 2~5℃ / min, specifically 5℃ / min in this embodiment.

[0037] Calcination temperature has a decisive influence on the graphitization of lignin and the formation of zero-valent iron coated with iron carbide. Under low-temperature conditions (<550℃), lignin often transforms into amorphous carbon, with lower degrees of graphitization and aromatization, and weaker catalytic activity of the carbon structure. Conversely, carbon structures formed under high-temperature calcination conditions have higher degrees of graphitization and aromatization, exhibiting stronger adsorption and catalytic activity. Zero-valent iron and iron carbide are also usually formed at temperatures above 600℃, and zinc volatilization temperature is 907℃. Therefore, in order to generate a multi-level porous structure through zinc volatilization, the second-stage calcination temperature needs to be above 900℃.

[0038] Sufficient calcination time is beneficial for the carbonization of lignin and the formation of zero-valent iron / iron carbide, but excessive calcination time can easily cause the collapse of the carbon pore structure and the agglomeration of zero-valent iron / nano-iron carbide particles. Stepwise calcination is also to prevent the continuous and violent reaction of iron and carbon components during one-step calcination from causing the collapse of the carbon structure and the agglomeration of metal nanoparticles, thereby avoiding the loss of effective active sites in the final composite material.

[0039] The main elemental composition of the material obtained in this invention includes carbon and iron, and its morphology consists of nano-sized zero-valent iron particles coated with iron carbide supported on a porous carbon carrier. Zinc volatilizes during calcination, thereby creating a porous structure within the carbon carrier.

[0040] The beneficial effects of this invention are as follows: (1) The preparation method of the lignin-based iron-carbon composite material of the present invention is a two-step process of impregnation combined with high-temperature pyrolysis, which is simple to operate and does not introduce harmful chemical reagents.

[0041] (2) Under high-temperature calcination conditions, the resulting composite material has a porous carbon-supported iron carbide-coated zero-valent iron structure, which makes the composite material highly stable in water and effectively activates persulfate degradation of various organic pollutants. The main function of zinc nitrate is to utilize the volatilization of zinc during high-temperature calcination to create a porous structure in the carbon structure, resulting in no zinc in the final material. During high-temperature calcination at nitrogen atmosphere and above 900℃, lignin is gradually carbonized, and the carbon reduces iron oxide to zero-valent iron and iron carbide. Iron carbide is a product of the deep reaction between zero-valent iron and carbon, and it easily exists between the zero-valent iron and carbon structure in the form of a zero-valent iron coating shell. Zero-valent iron alone is prone to direct dissolution reaction with water, causing iron dissolution and loss of iron reaction sites. In this invention, the zero-valent iron coated with iron carbide on the porous carbon surface and in the pores has a good protective effect on zero-valent iron, which can effectively prevent the loss of iron reaction sites through water dissolution reaction. Furthermore, the strong adsorption effect of porous carbon is more conducive to the efficient and continuous activation of the material to degrade various organic pollutants by persulfate.

[0042] (3) The carbon carrier precursor for the composite material is lignin, which is widely available and environmentally friendly.

[0043] (4) The lignin-based iron-carbon composite material prepared by the present invention has multiple active sites such as graphitized carbon, zero-valent iron, and iron carbide, which can efficiently and rapidly activate persulfate to generate a variety of strong oxidizing substances such as sulfate radicals, hydroxyl radicals, and singlet oxygen. Therefore, it has a strong reactivity to benzene, p-xylene, chlorobenzene, naphthalene and their composite pollutants, and has a strong ability to activate persulfate to efficiently degrade a variety of composite pollutants such as benzene-p-xylene, benzene-chlorobenzene, and benzene-naphthalene.

[0044] The present invention also provides the application of the lignin-based iron-carbon composite material described in the above technical solution or the lignin-based iron-carbon composite material prepared by the preparation method described in the above technical solution in the treatment of benzene series compounds and their composite pollutants in water bodies; The applications include: using lignin-based iron-carbon composite materials to adsorb benzene compounds and their complex pollutants in water; or using lignin-based iron-carbon composite materials to activate persulfate to degrade benzene compounds and their complex pollutants in water.

[0045] As one implementation method, the application includes the following steps: A lignin-based iron-carbon composite material was added to water bodies containing benzene series compounds and their complex pollutants for treatment. Alternatively, persulfate and lignin-based iron-carbon composite materials can be added sequentially to water bodies containing benzene series compounds and their complex pollutants for treatment; The lignin-based iron-carbon composite material is the lignin-based iron-carbon composite material described in the above technical solution or the lignin-based iron-carbon composite material prepared by the preparation method described in the above technical solution.

[0046] In one embodiment, the benzene series compounds and their complex pollutants include one or more of benzene, p-xylene, chlorobenzene, and naphthalene, specifically benzene and p-xylene, or benzene and chlorobenzene, or benzene and naphthalene; the concentration of each pollutant in the water body is independently 1~10 mg / L, specifically 10 mg / L; the persulfate includes sodium persulfate and / or potassium persulfate, specifically potassium persulfate; the persulfate in the water body containing benzene series compounds and their complex pollutants... The concentration of the lignin-based iron-carbon composite material is 1~10mM, and in a specific embodiment it is 4mM; the concentration of the lignin-based iron-carbon composite material in water containing benzene series compounds and their composite pollutants is 0.4~4g / L, and in a specific embodiment it is 0.4g / L; the treatment time is 1~2h, and in a specific embodiment it is 1.5~2h; the treatment is carried out under constant temperature and oscillation conditions; the treatment temperature is 15~30℃, and in a specific embodiment it is 25℃; the oscillation rate is 100~300rpm, and in a specific embodiment it is 150rpm.

[0047] As one implementation method, the adsorption and removal rate of p-xylene, chlorobenzene, and naphthalene in water by using lignin-based iron-carbon composite materials is over 85% during the adsorption of benzene series compounds and their composite pollutants in water; the removal efficiency of single benzene series compounds is over 95% and the removal efficiency of composite pollutants of benzene series compounds is over 90% during the activation of persulfate degradation in water by lignin-based iron-carbon composite materials.

[0048] The lignin-based iron-carbon composite material of this invention has a porous graphitized carbon structure and has a strong adsorption capacity for benzene, p-xylene and other benzene series compounds, as well as other organic pollutants such as chlorobenzene and naphthalene. Furthermore, it can activate persulfate to generate a variety of strong oxidizing substances such as sulfate radicals, hydroxyl radicals, and singlet oxygen, effectively oxidizing and degrading the above-mentioned pollutants as well as other organic pollutants such as chlorinated hydrocarbons and phenols.

[0049] The lignin-based iron-carbon composite material provided by this invention has the advantages of high removal rate and low cost in adsorbing and activating persulfate to remove benzene series compounds and their complex pollutants, and has a good application prospect in the remediation of groundwater complex pollution.

[0050] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0051] Example 1 Alkaline lignin (purchased from Maclean's Reagent Company, L832292, CAS: 8068-05-1) was dissolved in ultrapure water and stirred at 25°C and 300 rpm for 1 h to obtain a lignin-containing solution with a concentration of 8 g / L. Ferric nitrate nonahydrate and zinc nitrate hexahydrate were dissolved in the lignin-containing solution and stirred at 25°C and 300 rpm for 1 h to obtain a lignin solution with a Fe to Zn molar ratio of 1:1, wherein the concentration of ferric nitrate was 8 g / L. The resulting solution was allowed to stand for 12 h. After centrifugation at 5000 rpm for 10 min at room temperature, the precipitate was collected, washed three times with ultrapure water, dried at 80℃ and a vacuum of 0.01 Pa for 12 h, ground into powder, and passed through a 200-mesh sieve to obtain powder. The powder was placed in a tube furnace and calcined at 550℃ for 1 h under a nitrogen atmosphere at a heating rate of 5℃ / min, followed by calcination at 950℃ for 1 h at a heating rate of 5℃ / min, finally yielding a lignin-based iron-carbon composite material with a specific surface area of ​​138~340 m². 2 / g, pore volume is 0.05~0.1cm³ 3 / g, the particle size of iron carbide coated with zero-valent iron is 10~100nm, and the total iron content is 59.7wt%.

[0052] Application of lignin-based iron-carbon composite materials in the degradation of benzene series compounds and their complex pollutants in groundwater by activated persulfate: Application Example 1 Add 19.8 mL of groundwater sample containing 10 mg / L benzene, p-xylene, chlorobenzene or naphthalene and 8 mg of the lignin-based iron-carbon composite material prepared in Example 1 to a 22 mL glass bottle, then add 200 μL of potassium persulfate to make its initial concentration 4 mM; the glass bottle is protected from light by sealing it in a black bag and placed in a constant temperature shaking oven at 150 rpm and 25 °C for 2 h.

[0053] Application Example 2 Add 19.8 mL of groundwater sample containing benzene-p-xylene, benzene-chlorobenzene, or benzene-naphthalene, and 8 mg of the lignin-based iron-carbon composite material prepared in Example 1 to a 22 mL glass bottle. The concentration of each pollutant in the water is 10 mg / L. Then add 200 μL of potassium persulfate to make its initial concentration 4 mM. The glass bottle is protected from light by sealing it with a black bag and placed in a constant temperature shaking oven at 150 rpm and 25 °C for 2 h.

[0054] Comparative Application Example 1 The difference from Application Example 1 is that the groundwater samples containing 10 mg / L benzene, p-xylene, chlorobenzene or naphthalene respectively are replaced with groundwater samples containing 10 mg / L perfluorooctanoic acid, trichloroethylene or 1,4-dioxane respectively.

[0055] Application of lignin-based iron-carbon composite materials in the adsorption and removal of benzene series compounds and their complex pollutants: Application Example 3 Add 20 mL of groundwater sample containing 10 mg / L benzene, p-xylene, chlorobenzene or naphthalene and 8 mg of iron-carbon composite material to a 22 mL glass bottle respectively; protect the glass bottle from light by sealing it with a black bag, place it in a constant temperature shaking incubator, rotate at 150 rpm, set the temperature to 25℃, and react for 2 h.

[0056] Application Example 4 Add 20 mL of groundwater sample containing benzene-p-xylene, benzene-chlorobenzene, or benzene-naphthalene complex pollution and 8 mg of iron-carbon composite material to a 22 mL glass bottle. The concentration of each pollutant in the water sample is 10 mg / L. The glass bottle is protected from light by sealing it with a black bag and placed in a constant temperature shaking incubator at 150 rpm and 25°C for 2 hours.

[0057] Comparative Application Example 2 The difference from Application Example 3 is that the groundwater samples containing 10 mg / L benzene, p-xylene, chlorobenzene or naphthalene respectively are replaced with groundwater samples containing 10 mg / L perfluorooctanoic acid, trichloroethylene or 1,4-dioxane respectively.

[0058] Performance testing (1) The scanning electron microscopy and transmission electron microscopy characterization results of the lignin-based iron-carbon composite material prepared in Example 1 are as follows: Figure 1 and 2 As shown.

[0059] from Figure 1 and 2 As can be seen, the spherical zero-valent iron particles are coated with a shell. The zero-valent iron coated with iron carbide is mainly supported on the surface and pores of porous carbon. The porous carbon support supports core-shell spherical iron-containing particles with a particle size range of 10~100nm.

[0060] (2) The XRD pattern of the lignin-based iron-carbon composite material prepared in Example 1 is as follows: Figure 3 As shown, the original lignin-based iron-carbon composite material before the reaction is the lignin-based iron-carbon composite material after the reaction, which is the result of the activated persulfate degradation of pollutants.

[0061] from Figure 3It can be seen that the iron phase of the lignin-based iron-carbon composite material is mainly zero-valent iron and iron carbide. Therefore, the structure of the obtained material is porous carbon-supported iron carbide coated with nano-zero-valent iron.

[0062] (3) The oxidative degradation removal effects of pollutants in Examples 1 and 2 are shown in Table 1 and Table 2. Figure 4 As shown, (a) is a benzene-p-xylene complex system, (b) is a benzene-chlorobenzene complex system, (c) is a benzene-naphthalene complex system, and (d) is a single pollution system.

[0063] Table 1. Oxidative degradation and removal efficiency of pollutants in Application Examples 1 and 2

[0064] As shown in Table 1 and Figure 4 As shown, the lignin-based iron-carbon composite activated persulfate exhibits a removal efficiency of over 95% for single benzene compounds; particularly, it can simultaneously achieve highly efficient removal of benzene-p-xylene, benzene-chlorobenzene, and benzene-naphthalene complex pollutants in water: after 2 hours of oxidative degradation, the removal rate of each pollutant in the complex pollution system can reach over 90%, comparable to the pollutant removal rate of a single pollution system. The lignin-based iron-carbon composite activated persulfate shows an oxidative degradation removal rate of less than 60% for trichloroethylene and 1,4-dioxane, and virtually no degradation ability for perfluorooctanoic acid (PFOA). The lignin-based iron-carbon composite activated persulfate demonstrates significantly excellent degradation performance for aromatic organic pollutants such as benzene, p-xylene, chlorobenzene, and naphthalene, while exhibiting poor degradation performance for non-aromatic organic pollutants such as trichloroethylene, 1,4-dioxane, and PFOA.

[0065] (4) The adsorption and removal effects of pollutants in Examples 3 and 4 are shown in Table 2.

[0066] Table 2 Adsorption and removal efficiency of pollutants in Application Examples 3 and 4

[0067] As shown in Table 2, the lignin-based iron-carbon composite material exhibits adsorption and removal rates of over 85% for individual xylene, chlorobenzene, and naphthalene, and a removal rate of 57.35% for benzene. Simultaneously, the composite material can achieve highly efficient adsorption and removal of xylene, chlorobenzene, and naphthalene in benzene-p-xylene, benzene-chlorobenzene, and benzene-naphthalene complex pollution in groundwater: after 2 hours of adsorption, the removal rates for xylene, chlorobenzene, and naphthalene remain above 85%. However, the adsorption effect on perfluorooctanoic acid, trichloroethylene, and 1,4-dioxane is weak, with removal rates all below 25%.

[0068] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. The application of lignin-based iron-carbon composite materials in the treatment of benzene series compounds and their complex pollutants in water bodies, characterized in that, The applications include: using lignin-based iron-carbon composite materials to adsorb benzene compounds and their complex pollutants in water; or using lignin-based iron-carbon composite materials to activate persulfate to degrade benzene compounds and their complex pollutants in water; wherein the benzene compounds and their complex pollutants include one or more of benzene, p-xylene, chlorobenzene, and naphthalene. The lignin-based iron-carbon composite material includes lignin-based porous carbon and nanoparticles loaded on the surface and pores of the lignin-based porous carbon. The nanoparticles are iron carbide coated with zero-valent iron. The lignin-based porous carbon has a porous graphitized carbon structure; The preparation method of the lignin-based iron-carbon composite material includes the following steps: A lignin-containing solution, inorganic iron salt, and inorganic zinc salt were mixed, allowed to stand and age, and then the solid and liquid were separated to obtain a precipitate. The precipitate was calcined in a protective gas to obtain the lignin-based iron-carbon composite material; The molar ratio of Fe in the inorganic iron salt to Zn in the inorganic zinc salt is 1:1~5; The inorganic zinc salt is zinc nitrate; The calcination includes sequential low-temperature calcination and high-temperature calcination; the low-temperature calcination temperature is 350~550℃, and the holding time is 1~2h; the high-temperature calcination temperature is 900~1000℃, and the holding time is 1~4h.

2. The application according to claim 1, characterized in that, The specific surface area of ​​the lignin-based iron-carbon composite material is 138~340 m². 2 / g, pore volume is 0.05~0.1cm³ 3 / g; the particle size of the iron carbide coated with zero-valent iron is 10~100nm.

3. The application according to claim 1, characterized in that, The lignin is alkaline lignin.

4. The application according to claim 3, characterized in that, The concentration of lignin in the lignin-containing solution is 5~20 g / L.

5. The application according to claim 1, characterized in that, The heating rate from room temperature to the low-temperature calcination temperature is 5~10℃ / min; the heating rate from the low-temperature calcination temperature to the high-temperature calcination temperature is 2~5℃ / min.

6. The application according to claim 1, characterized in that, The concentration of each pollutant in the water containing benzene series compounds and their composite pollutants is 1~10 mg / L; the concentration of persulfate in the water containing benzene series compounds and their composite pollutants is 1~10 mM; and the concentration of the lignin-based iron-carbon composite material in the water containing benzene series compounds and their composite pollutants is 0.4~4 g / L.

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