A conductive wood-based filter, its preparation method and application

Abstract

This invention provides a conductive wood-based filter, its preparation method, and its application, belonging to the field of water treatment technology. The invention provides a conductive wood-based filter comprising a wood matrix and nano-carbon material grafted with nano-zero-valent iron (ZVI) onto the surface and pores of the wood matrix. The conductive wood-based filter provided by this invention enables uniform dispersion of ZVI nanoparticles on the filter surface, solving the problems of easy agglomeration and difficult recovery of ZVI nanoparticles, and the ZVI nanoparticles possess a large effective specific surface area. The use of nano-carbon material combined with ZVI nanoparticles solves the problem of high electron transfer resistance during the ZVI nanoparticle reaction. When the conductive wood-based filter of this invention is used to filter water containing Cr(VI), the reaction is carried out in cathode mode by applying an electric field, which effectively alleviates the oxidation and passivation of ZVI nanoparticles, ensuring operational stability and improving reaction efficiency.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a conductive wood-based filter, its preparation method, and its application. Background Technology

[0002] Water pollution is a pressing global environmental problem that urgently needs to be addressed. Common pollutants in water mainly include organic pollutants and heavy metal pollutants. Unlike organic pollutants, heavy metal pollutants cannot be degraded and can accumulate through the food chain, increasing in concentration by hundreds or even tens of thousands of times, ultimately posing a serious threat to human health. Hexavalent chromium (Cr(VI)) is a heavy metal pollutant that can exist stably in the aquatic environment, is easily absorbed and accumulated by living organisms, and has very strong carcinogenic and mutagenic effects, classifying it as a Group 1 carcinogen. Chromium is widely used in industries such as electroplating, leather making, and mining, generating large amounts of Cr(VI)-containing wastewater. Furthermore, improper treatment of this industrial wastewater allows large amounts of Cr(VI)-containing pollutants to enter the aquatic environment, causing Cr(VI) pollution problems in natural water bodies and posing a serious threat to the ecological environment and human health.

[0003] Removing Cr(VI) from water has always been an important research direction in the field of environmental water treatment. Currently, the main method for removing Cr(VI) from water is to first reduce Cr(VI) to the less toxic Cr(III), and then remove it through processes such as precipitation or adsorption. Studies have found that nano-zero-valent iron has excellent reducing and adsorption capabilities for Cr(VI), and due to its environmentally friendly characteristics, it shows broad research prospects in the field of Cr(VI) detoxification and removal.

[0004] However, nano-zero valent iron has the problems of easy particle agglomeration and high resistance to electron transfer during the reaction process; moreover, the powder material also faces the disadvantage of difficult recycling in practical applications; in addition, due to its small particle size and high reactivity, nano-zero valent iron is prone to react with water and oxygen, forming an iron oxide passivation layer on the particle surface, which hinders the electron transfer between zero valent iron particles and pollutants, causing its treatment performance to drop sharply. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a conductive wood-based filter, its preparation method, and its application. The conductive wood-based filter provided by this invention can avoid the problems of agglomeration of nano-zero valent iron and high electron transfer resistance, and can also effectively alleviate the oxidation and passivation of nano-zero valent iron, and is easy to recycle.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] The present invention provides a conductive wood-based filter, comprising a wood matrix and nano-carbon material grafted with zero-valent iron on the surface and within the pores of the wood matrix.

[0008] Preferably, the nano-carbon material includes one or more of graphene oxide, carbon nanotubes, and carbon quantum dots; the nano-zero valent iron accounts for 0.1 to 10 wt% of the nano-carbon material; and the loading of the nano-zero valent iron-grafted nano-carbon material on the wood matrix is ​​0.05 to 10 wt%.

[0009] This invention provides a method for preparing the conductive wood-based filter described above, comprising the following steps:

[0010] The wood matrix is ​​mixed with an alkaline solution and modified by alkaline treatment to obtain a modified wood matrix.

[0011] The nano-carbon material is mixed with an oxidizing acid and subjected to oxidation treatment to obtain carboxylated nano-carbon material;

[0012] The carboxylated carbon nanomaterials were dispersed in an aqueous solution containing ferrous ions and grafted to obtain Fe. 2+ Dispersion of grafted carboxylated carbon nanomaterials;

[0013] Using the modified wood matrix to treat the Fe 2+ The grafted carboxylated nanocarbon material dispersion was filtered, and the filtered modified wood matrix was then impregnated in the Fe... 2+ In the grafted carboxylated carbon nanomaterial dispersion, Fe 2+ Grafted carboxylated carbon nanomaterials are dispersed onto the surface and within the pores of a wood matrix to obtain Fe-loaded nanomaterials. 2+ A filter made of grafted carboxylated carbon nanomaterials;

[0014] The load Fe 2+ The filter of grafted carboxylated nanocarbon material is subjected to reduction treatment, Fe 2+ It is reduced to nano-zero valent iron to obtain the conductive wood-based filter.

[0015] Preferably, the wood matrix includes a natural wood matrix; the temperature of the alkali treatment modification is below the boiling point of the alkali solution; the time of the alkali treatment modification is 10 min to 24 h; and the temperature of the oxidation treatment is 100 to 140 °C, and the time is 2 to 36 h.

[0016] Preferably, the aqueous solution containing ferrous ions includes an aqueous solution of ferrous chloride, an aqueous solution of ferrous sulfate, or an aqueous solution of ferrous nitrate; the mass ratio of the carboxylated carbon nanomaterial to the volume ratio of the aqueous solution containing ferrous ions is (20-2000) mg: 1 L.

[0017] Preferably, the filtration flow rate is 0.01–2.0 mL / (min·cm). 2 The immersion temperature is 20–60°C, and the immersion time is 0.5–48 h.

[0018] Preferably, the reduction treatment includes thermal reduction treatment, room temperature reducing agent reduction treatment, or hydrothermal reduction treatment.

[0019] This invention provides the application of the conductive wood-based filter described in the above-described scheme or the conductive wood-based filter prepared by the above-described preparation method in filtering water containing Cr(VI).

[0020] The present invention provides the application described in the above scheme. The method for filtering water containing Cr(VI) includes the following steps: constructing an electrochemical assisted filtration system with a conductive wood-based filter as the cathode and a metal mesh as the anode, and passing the water containing Cr(VI) through the conductive wood-based filter under the condition of applying an electric field.

[0021] Preferably, the metal mesh comprises titanium, stainless steel or platinum; the operating voltage of the conductive wood-based filter is -0.5 to -5.0V.

[0022] This invention provides a conductive wood-based filter, comprising a wood matrix and nano-carbon material grafted with nano-zero-valent iron loaded on the surface and within the pores of the wood matrix. The conductive wood-based filter provided by this invention enables uniform dispersion of nano-zero-valent iron on the filter surface, solving the problems of easy agglomeration and difficult recovery of nano-zero-valent iron, and possesses a large number of effective active sites; the use of nano-carbon material combined with nano-zero-valent iron solves the problem of high electron transfer resistance during the reaction of nano-zero-valent iron.

[0023] The conductive wood-based filter of the present invention is used to filter water containing Cr(VI). By applying an electric field to carry out the reaction in cathode mode, the oxidation and passivation of nano-zero-valent iron can be effectively alleviated, ensuring its operational stability and improving the reaction efficiency.

[0024] Furthermore, the wood matrix used in this invention is a natural wood matrix, which is energy-saving and environmentally friendly, and has naturally developed water channels. Nano-carbon materials grafted with nano-zero valent iron are loaded in situ onto the surface and pores of the wood matrix. The filtration mode can improve the mass transfer efficiency of the water treatment process and improve the treatment efficiency. Detailed Implementation

[0025] The present invention provides a conductive wood-based filter, comprising a wood matrix and nano-carbon material grafted with zero-valent iron on the surface and within the pores of the wood matrix.

[0026] In this invention, the nano-carbon material preferably includes one or more of graphene oxide, carbon nanotubes, and carbon quantum dots. In this invention, the nano-zero-valent iron preferably accounts for 0.1–10 wt% of the nano-carbon material, more preferably 0.5–5 wt%, and even more preferably 1–4 wt%; the loading amount of the nano-zero-valent iron-grafted nano-carbon material in the wood matrix is ​​preferably 0.05–10 wt%, more preferably 1–7 wt%, and even more preferably 2–4.5 wt%.

[0027] The conductive wood-based filter provided by this invention enables uniform dispersion of nano-zero valent iron on the filter, solving the problems of easy agglomeration and difficult recovery of nano-zero valent iron, and has a large number of effective active sites; by using nano-carbon materials to combine with nano-zero valent iron, the problem of high electron transfer resistance during the reaction of nano-zero valent iron is solved.

[0028] This invention provides a method for preparing the conductive wood-based filter described above, comprising the following steps:

[0029] The wood matrix is ​​mixed with an alkaline solution and modified by alkaline treatment to obtain a modified wood matrix.

[0030] The nano-carbon material is mixed with an oxidizing acid and subjected to oxidation treatment to obtain carboxylated nano-carbon material;

[0031] The carboxylated carbon nanomaterials were dispersed in an aqueous solution containing ferrous ions and grafted to obtain Fe. 2+ Dispersion of grafted carboxylated carbon nanomaterials;

[0032] Using the modified wood matrix to treat the Fe 2+ The grafted carboxylated nanocarbon material dispersion was filtered, and the filtered modified wood matrix was then impregnated in the Fe... 2+ In the grafted carboxylated carbon nanomaterial dispersion, Fe 2+ Grafted carboxylated carbon nanomaterials are dispersed onto the surface and within the pores of a wood matrix to obtain Fe-loaded nanomaterials. 2+ A filter made of grafted carboxylated carbon nanomaterials;

[0033] The load Fe 2+ The filter of grafted carboxylated nanocarbon material is subjected to reduction treatment, Fe 2+ It is reduced to nano-zero valent iron to obtain the conductive wood-based filter.

[0034] Unless otherwise specified, all materials and equipment used in this invention are commercially available products in the field.

[0035] This invention involves mixing a wood matrix with an alkaline solution and then subjecting it to alkaline treatment modification to obtain a modified wood matrix.

[0036] In this invention, the wood matrix preferably comprises a natural wood matrix; the natural wood matrix preferably comprises a hardwood matrix.

[0037] In this invention, the wood matrix is ​​preferably obtained by cutting and cleaning wood to remove impurities. Preferably, the cutting is done by cutting the wood into slices perpendicular to the wood's growth direction; the cleaning is preferably done by soaking in deionized water to remove impurities. This invention does not have specific requirements regarding the number of cleaning cycles, as long as the wood is thoroughly cleaned.

[0038] In this invention, the alkaline solution preferably comprises an aqueous solution of sodium hydroxide, potassium hydroxide, or calcium hydroxide; the concentration of the alkaline solution is preferably 1–30 wt%, more preferably 3–18 wt%, and even more preferably 5–12 wt%. In this invention, the temperature for alkaline treatment modification is preferably below the boiling point of the alkaline solution, more preferably ≥30℃ and ≤ the boiling point of the alkaline solution; the time for alkaline treatment modification is preferably 10 min–24 h, more preferably 2–15 h, and even more preferably 5–10 h. This invention does not have particular requirements on the amount of alkaline solution used, as long as the alkaline treatment modification reaction is sufficient. In this invention, the volume ratio of the wood matrix to the oxidizing acid is preferably (20–100) cm³. 3 (100–600) mL, more preferably (30–70) cm 3 (200-400) mL, more preferably (40-50) cm 3 (250-350) mL. This invention modifies wood through alkali treatment, which removes lignin and other impurities and facilitates the fixation of nano-carbon materials grafted with nano-zero valent iron onto the surface and pores of the wood matrix.

[0039] The wood matrix used in this invention is a natural wood matrix, which is energy-saving and environmentally friendly, and has naturally developed water channels. Nano-carbon materials grafted with nano-zero valent iron are loaded in situ onto the surface and pores of the wood matrix. The filtration mode can improve the mass transfer efficiency of the water treatment process and improve the treatment efficiency.

[0040] After the alkali treatment modification is completed, the resulting wood is preferably rinsed and dried sequentially with deionized water. In this invention, the rinsing is preferably performed until the pH of the washing solution is neutral; the drying is preferably performed by natural drying.

[0041] This invention involves mixing nano-carbon materials with oxidizing acids and subjecting them to oxidation treatment to obtain carboxylated nano-carbon materials.

[0042] In this invention, the oxidizing acid preferably includes concentrated nitric acid and / or concentrated sulfuric acid. This invention does not have specific requirements for the concentration of the acid solution, as long as it has oxidizing properties. In this invention, the concentration of the oxidizing acid is preferably ≥5M. In this invention, the oxidation treatment temperature is preferably 100–140℃, more preferably 110–135℃, and even more preferably 115–125℃; the oxidation treatment time is preferably 2–36 h, more preferably 3–18 h, and even more preferably 5–12 h. In this invention, the amount of the oxidizing acid must be excessive to ensure that the oxidation reaction proceeds fully. In this invention, the mass ratio of the nano-carbon material to the volume ratio of the oxidizing acid is preferably (0.1–1) g : (100–2000) mL, more preferably (0.2–0.8) g : (200–1000) mL, and even more preferably (0.3–0.6) g : (400–800) mL. This invention does not have specific requirements regarding the volume ratio of the concentrated nitric acid and concentrated sulfuric acid mixture; a volume ratio well-known in the art can be used. This invention enables the carboxylation of nano-carbon materials through oxidation treatment, facilitating subsequent Fe... 2+ Grafted onto carbon nanomaterials.

[0043] After the oxidation treatment is completed, the resulting nano-carbon material is preferably washed and freeze-dried sequentially. In this invention, the washing is preferably performed until the pH of the washing solution is neutral. This invention does not have special requirements for the freeze-drying procedure and parameters; they can be set according to the type of nano-carbon material.

[0044] After obtaining the carboxylated carbon nanomaterials, the present invention disperses the carboxylated carbon nanomaterials in an aqueous solution containing ferrous ions and performs a grafting reaction to obtain Fe. 2+ Dispersion of grafted carboxylated carbon nanomaterials.

[0045] In this invention, the aqueous solution containing ferrous ions preferably includes an aqueous solution of ferrous chloride, ferrous sulfate, or ferrous nitrate; the concentration of the aqueous solution containing ferrous ions is preferably 0.02–0.15 M, more preferably 0.03–0.12 M, and even more preferably 0.05–0.1 M. In this invention, the mass ratio of the carboxylated carbon nanomaterial to the volume ratio of the aqueous solution containing ferrous ions is preferably (20–2000) mg:1 L, more preferably (50–1500) mg:1 L, and even more preferably (100–500) mg:1 L. In this invention, the grafting reaction is preferably carried out under ultrasonic conditions; this invention does not have particular requirements for the power and time of the ultrasound, as long as it can disperse the carboxylated carbon nanomaterial in the aqueous solution containing ferrous ions. This invention enables ferrous ions to be grafted onto the carboxyl groups of the carboxylated carbon nanomaterial through a grafting reaction.

[0046] The Fe was obtained2+ After grafting the carboxylated nanocarbon material dispersion and the modified wood matrix, the present invention utilizes the modified wood matrix to target the Fe... 2+ The grafted carboxylated nanocarbon material dispersion was filtered, and the filtered modified wood matrix was then impregnated in the Fe... 2+ In the grafted carboxylated carbon nanomaterial dispersion, Fe 2+ Grafted carboxylated carbon nanomaterials are dispersed onto the surface and within the pores of a wood matrix to obtain Fe-loaded nanomaterials. 2+ A filter made of grafted carboxylated carbon nanomaterials.

[0047] In this invention, the preferred filtration flow rate is 0.01–2.0 mL / (min·cm). 2 (), more preferably 0.02–1.5 mL / (min·cm) 2 More preferably, it is 0.05–1.2 mL / (min·cm). 2 In this invention, the immersion temperature is preferably 20–60°C, more preferably 25–55°C, and even more preferably 30–45°C; the immersion time is preferably 0.5–48 h, more preferably 5–35 h, and even more preferably 8–25 h. In this invention, the Fe… 2+ The preferred volume ratio of the grafted carboxylated nanocarbon material dispersion to the modified wood matrix is ​​(2-100) mL:1 cm⁻¹. 3 A further preferred ratio is (3-50) mL: 1 cm 3 More preferably, the ratio is (5-10) mL: 1 cm 3 .

[0048] After the immersion is completed, the present invention preferably removes the resulting filter and allows it to air dry.

[0049] The load Fe was obtained 2+ Following the application of grafted carboxylated carbon nanomaterials to a filter, the present invention will load the Fe... 2+ The filter of grafted carboxylated nanocarbon material is subjected to reduction treatment, Fe 2+ It is reduced to nano-zero valent iron to obtain the conductive wood-based filter.

[0050] In this invention, the reduction treatment preferably includes thermal reduction treatment, room temperature reducing agent reduction treatment, or hydrothermal reduction treatment. When thermal reduction treatment is used, it is preferably carried out in a tube furnace under the protection of a mixed atmosphere of nitrogen and hydrogen (the volume ratio of nitrogen to hydrogen is 98:2); the temperature of the thermal reduction treatment is preferably 500°C; and the time of the thermal reduction treatment is preferably 60–120 min, more preferably 70–110 min, and even more preferably 80–95 min.

[0051] When using a room-temperature reducing agent for reduction treatment, the present invention does not limit the type of reducing agent, as long as it can reduce the oxidized nano-carbon material and ferrous ions. Specifically, the reducing agent can be hydrazine hydrate or sodium borohydride. In the embodiments of the present invention, the reducing agent is specifically sodium borohydride; the concentration of the reducing agent is preferably 0.5 mM. The present invention does not have special requirements for the method of room-temperature reducing agent reduction treatment, and methods well known in the art can be used. In the embodiments of the present invention, specifically, the Fe-loaded material is reduced by filtering a sodium borohydride solution. 2+ The filter with grafted carboxylated carbon nanomaterials undergoes reduction treatment.

[0052] When hydrothermal reduction treatment is used, the preferred temperature for the hydrothermal reduction treatment is 120°C, and the preferred time is 12 hours.

[0053] This invention can reduce and fix oxidized nano-carbon materials onto the surface and pores of a wood matrix through reduction treatment, while the grafted ferrous ions are reduced to nano-zero ferrous iron.

[0054] This invention provides the application of the conductive wood-based filter described in the above-described scheme or the conductive wood-based filter prepared by the above-described preparation method in filtering water containing Cr(VI).

[0055] In this invention, the method for filtering Cr(VI)-containing water preferably includes the following steps: constructing an electrochemically assisted filtration system using a conductive wood-based filter as the cathode and a metal mesh as the anode, and passing the Cr(VI)-containing water through the conductive wood-based filter under an applied electric field; the metal mesh preferably comprises titanium, stainless steel, or platinum; the operating voltage of the conductive wood-based filter is -0.5 to -5.0V, more preferably -1 to -4.5V, and even more preferably -2 to -3.5V. In this invention, the conductive wood-based filter is preferably suitable for treating Cr(VI)-containing water with a concentration of 5 to 30 ppm, more preferably 6 to 25 ppm, and even more preferably 10 to 20 ppm. In this invention, the operating flow rate of the Cr(VI)-containing water through the conductive wood-based filter is preferably 0.2 to 2.5 mL / min, more preferably 0.5 to 2 mL / min. The present invention preferably uses a pump to pass water containing Cr(VI) through a conductive wood-based filter, so that Cr(VI) in the water is reduced to low-toxicity Cr(III) and adsorbed on the material to achieve removal.

[0056] The conductive wood-based filter of the present invention is used to filter water containing Cr(VI). By applying an electric field to carry out the reaction in cathode mode, the oxidation and passivation of nano-zero-valent iron can be effectively alleviated, ensuring its operational stability and improving the reaction efficiency.

[0057] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, provides a conductive wood-based filter, its preparation method, and its application, but these descriptions should not be construed as limiting the scope of protection of the present invention.

[0058] Example 1

[0059] Cut natural paulownia wood into 2cm thick slices along its perpendicular growth direction, with an area of ​​20cm². 2 After being cleaned with deionized water, the material was immersed in a 5 wt.% sodium hydroxide solution (300 mL) for alkali treatment at 40°C for 8 hours. After removal, the material was washed with deionized water to remove residual alkali and then allowed to dry naturally to obtain the modified paulownia wood matrix.

[0060] 0.2 g of carbon nanotubes were dispersed in a 10 M, 200 mL concentrated sulfuric acid solution for oxidation treatment. The oxidation treatment was carried out by reflux at 120 °C for 6 h. After washing, the carbon nanotubes were freeze-dried to obtain carboxylated carbon nanotubes.

[0061] The carboxylated carbon nanotubes were ultrasonically dispersed in a 0.1 M ferrous chloride solution and grafted to obtain Fe. 2+ A grafted carboxylated carbon nanotube dispersion, wherein the mass ratio of the carboxylated carbon nanotubes to the volume of the 0.1M ferrous chloride solution is 100 mg: 1 L;

[0062] Using the modified paulownia wood matrix, at a rate of 0.05 mL / (min·cm) 2) The flow rate of the Fe200 mL 2+ The grafted carboxylated carbon nanotube dispersion was filtered, and then the filtered modified paulownia wood matrix was impregnated in the Fe... 2+ The grafted carboxylated carbon nanotubes were reacted at a constant temperature of 40°C for 10 hours to allow Fe... 2+ Grafted carboxylated carbon nanomaterials are dispersed onto the surface and within the pores of a wood matrix. After the reaction, the material is removed and allowed to air dry to obtain Fe-loaded nanomaterials. 2+ A filter made of grafted carboxylated carbon nanotubes;

[0063] The load Fe 2+ The grafted carboxylated carbon nanotubes were filtered through a 0.5 mM, 50 mL sodium borohydride solution to allow the carboxylated carbon nanotubes and grafted Fe... 2+ The process was repeated to obtain a conductive paulownia wood-based filter 1.

[0064] Application Example 1

[0065] An electrochemical-assisted filtration system was constructed using a conductive paulownia wood-based filter 1 as the cathode and a titanium mesh as the anode. Water containing Cr(VI) was then pumped through the conductive paulownia wood-based filter under an applied electric field. The system treated an aqueous solution containing 10 ppm of Cr(VI) at an operating voltage of -1V and a flow rate of 1 mL / min. The overall treatment effect during a 5-hour operation is shown in Table 1.

[0066] Application Example 2

[0067] The steps are the same as in Application Example 1, except that the operating voltage is -2V.

[0068] Application Comparative Example 1

[0069] The steps are the same as in Application Example 1, except that no electric field is applied.

[0070] Application Comparative Example 2

[0071] The steps are the same as in Application Example 1, except that no electric field is applied and an unmodified paulownia wood matrix with carbon nanotubes and nano-zero valent iron is used as the cathode.

[0072] Table 1 shows the processing effects of application examples 1-2 and comparative examples 1-2.

[0073] serial number sample Voltage / V Removal rate / % Application Example 1 Paulownia wood-based filter 1 -1 95.1 Application Example 2 Paulownia wood-based filter 1 -2 99.8 Application Comparative Example 1 Paulownia wood-based filter 1 0 78.7 Application Comparative Example 2 Paulownia wood matrix 0 23.5

[0074] As can be seen from Table 1, under the condition of applying an electric field, the removal rate of 10 ppm Cr(VI) aqueous solution treated by the paulownia wood-based filter of the present invention is greater than that without applying an electric field, with the highest removal rate reaching 99.8%. Under the condition of not applying an electric field, the removal rate of 10 ppm Cr(VI) aqueous solution treated by the paulownia wood-based filter of the present invention is much greater than that of paulownia wood matrix without modified carbon nanotubes and nano-zero valent iron.

[0075] Example 2

[0076] Natural linden wood is cut into 3cm thick slices along its perpendicular growth direction, resulting in a wood surface area of ​​15cm². 2 After being cleaned with deionized water, the material was immersed in a 5 wt.% 300 mL potassium hydroxide solution for alkali treatment at a temperature of 55°C for 5 hours. After removal, the material was washed with deionized water to remove residual alkali and then allowed to dry naturally to obtain the modified linden wood matrix.

[0077] 0.1 g of graphene oxide was dispersed in 10 M, 200 mL concentrated sulfuric acid solution (molar concentration) for oxidation treatment. The oxidation treatment was carried out by reflux at 120 °C for 4 h. After washing, the graphene oxide was freeze-dried to obtain carboxylated graphene oxide.

[0078] The carboxylated graphene oxide was ultrasonically dispersed in a 0.05M ferrous sulfate solution for grafting to obtain Fe. 2+ A grafted carboxylated graphene oxide dispersion, wherein the mass ratio of the carboxylated graphene oxide to the volume of the 0.05M ferrous sulfate solution is 100 mg: 1 L;

[0079] Using the modified linden wood matrix, at 0.02 mL / (min·cm) 2 The flow rate of 350 ml of the Fe 2+ The grafted carboxylated graphene oxide dispersion was filtered, and then the filtered modified linden wood matrix was impregnated in the Fe... 2+ The grafted carboxylated graphene oxide dispersion was reacted at a constant temperature of 40°C for 12 hours to allow Fe... 2+ Grafted carboxylated graphene oxide is dispersed onto the surface and within the pores of a wood matrix. After the reaction, it is removed and allowed to air dry to obtain Fe-loaded graphene oxide. 2+ A filter grafted with carboxylated graphene oxide;

[0080] The load Fe 2+ The filter of grafted carboxylated graphene oxide was subjected to thermal reduction treatment in a tube furnace under a nitrogen and hydrogen mixed atmosphere (the volume ratio of nitrogen to hydrogen was 98:2). The thermal reduction treatment was carried out at a temperature of 500°C for 60 minutes, so that the carboxylated graphene oxide and the grafted Fe... 2+ The process was repeated to obtain conductive linden wood-based filter 2.

[0081] Application Example 3

[0082] An electrochemical-assisted filtration system was constructed using a conductive linden wood-based filter 2 as the cathode and a stainless steel mesh as the anode. Water containing Cr(VI) was then pumped through the conductive linden wood-based filter under an applied electric field. The system treated an aqueous solution containing 10 ppm of Cr(VI) at an operating voltage of -1V and a flow rate of 0.5 mL / min. The overall treatment effect during the 8-hour operation is shown in Table 2.

[0083] Application Example 4

[0084] The steps are the same as in Application Example 3, except that the operating voltage is -2V.

[0085] Application Comparative Example 3

[0086] The steps are the same as in Application Example 3, except that no electric field is applied.

[0087] Application Comparative Example 4

[0088] The steps are the same as in Application Example 3, except that no electric field is applied and an unmodified graphene and nano-zero valent iron linden wood matrix is ​​used as the cathode.

[0089] Table 2 shows the processing effects of application examples 3-4 and comparative examples 3-4.

[0090] serial number sample Voltage / V Removal rate / % Application Example 3 Linden wood-based filter 2 -1 92.6 Application Example 4 Linden wood-based filter 2 -2 99.4 Application Comparative Example 3 Linden wood-based filter 2 0 82.5 Application Comparative Example 4 Linden wood matrix 0 16.9

[0091] As can be seen from Table 2, under the condition of applying an electric field, the removal rate of 10 ppm Cr(VI) aqueous solution treated by the linden wood-based filter of the present invention is greater than that under the condition of not applying an electric field, with the highest removal rate reaching 99.4%; under the condition of not applying an electric field, the removal rate of 10 ppm Cr(VI) aqueous solution treated by the linden wood-based filter of the present invention is much greater than that of linden wood matrix without modified graphene and nano-zero valent iron.

[0092] Example 3

[0093] Cut natural balsa wood into 3.5cm thick slices, each 20cm in area, perpendicular to its growth direction. 2 After being cleaned with deionized water, the material was immersed in a 5 wt.% 400 mL calcium hydroxide solution for alkali treatment at a temperature of 65°C for 3 hours. After removal, the material was washed with deionized water to remove residual alkali and then allowed to dry naturally to obtain the modified balsa wood matrix.

[0094] 0.5 g of multi-walled carbon nanotubes were dispersed in 12 M, 300 mL concentrated nitric acid solution (molar concentration) for oxidation treatment. The oxidation treatment was carried out by reflux at 130 °C for 6 h. After washing, the carbon nanotubes were freeze-dried to obtain carboxylated multi-walled carbon nanotubes.

[0095] Carboxylated multi-walled carbon nanotubes were ultrasonically dispersed in a 0.05 M ferrous sulfate solution and grafted to obtain Fe... 2+ A dispersion of grafted carboxylated multi-walled carbon nanotubes, wherein the mass ratio of the carboxylated multi-walled carbon nanotubes to the volume ratio of 0.05M ferrous sulfate solution is 50 mg: 1 L;

[0096] Using the modified balsa wood matrix, at 0.01 mL / (min·cm) 2 The flow rate of 500 mL of the Fe 2+ The grafted carboxylated multi-walled carbon nanotube dispersion was filtered, and then the filtered modified balsa wood matrix was impregnated in the Fe... 2+ The grafted carboxylated multi-walled carbon nanotubes were reacted at a constant temperature of 55°C for 8 hours to allow Fe... 2+ Grafted carboxylated multi-walled carbon nanotubes were dispersed onto the surface and within the pores of a wood matrix. After the reaction, the nanotubes were removed and allowed to air dry to obtain Fe-loaded nanotubes. 2+ A filter made of grafted carboxylated multi-walled carbon nanotubes;

[0097] The load Fe 2+The filter with grafted carboxylated multi-walled carbon nanotubes was subjected to a hydrothermal reaction (120℃, 12h) to allow the carboxylated multi-walled carbon nanotubes and grafted Fe... 2+ The process was repeated to obtain a conductive balsa wood-based filter 3.

[0098] Application Example 5

[0099] An electrochemical-assisted filtration system was constructed using a conductive balsa wood-based filter 3 as the cathode and a titanium mesh as the anode. Water containing Cr(VI) was then pumped through the conductive balsa wood-based filter under an applied electric field. The system treated an aqueous solution containing 20 ppm of Cr(VI) at an operating voltage of -1V and a flow rate of 2.0 mL / min. The overall treatment effect during the 4-hour operation is shown in Table 3.

[0100] Application Example 6

[0101] The steps are the same as in Application Example 5, except that the operating voltage is -2V.

[0102] Application Comparative Example 5

[0103] The steps are the same as in Application Example 5, except that no electric field is applied.

[0104] Application Comparative Example 6

[0105] The steps are the same as in Application Example 5, except that no electric field is applied and an unmodified multi-walled carbon nanotube and nano-zero valent iron balsa wood matrix is ​​used as the cathode.

[0106] Table 3 shows the treatment effects of application examples 5-6 and comparative examples 5-6.

[0107] serial number sample Voltage / V Removal rate / % Application Example 5 Balsa wood-based filter 3 -1 97.6 Application Example 6 Balsa wood-based filter 3 -2 99.7 Application Comparative Example 5 Balsa wood-based filter 3 0 88.1 Application Comparative Example 6 Balsa wood matrix 0 36.3

[0108] As can be seen from Table 3, under the condition of applying an electric field, the removal rate of 20 ppm Cr(VI) aqueous solution treated by the balsa wood-based filter of the present invention is greater than that without applying an electric field, with the highest removal rate reaching 99.7%. Under the condition of not applying an electric field, the removal rate of 20 ppm Cr(VI) aqueous solution treated by the balsa wood-based filter of the present invention is much greater than that of balsa wood matrix without modified multi-walled carbon nanotubes and nano-zero valent iron.

[0109] 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. A conductive wood-based filter, comprising a wood matrix and nano-carbon material grafted with zero-valent iron and loaded on the surface and pores of the wood matrix; The nanomaterials include one or more of graphene oxide, carbon nanotubes, and carbon quantum dots; the nano-zero valent iron accounts for 0.1~10 wt% of the nanomaterials; the loading of the nano-zero valent iron-grafted nanomaterials on the wood matrix is ​​0.05~10 wt%. The method for preparing the conductive wood-based filter includes the following steps: The wood matrix is ​​mixed with an alkaline solution and modified by alkaline treatment to obtain a modified wood matrix. The nano-carbon material is mixed with an oxidizing acid and subjected to oxidation treatment to obtain carboxylated nano-carbon material; The carboxylated carbon nanomaterials were dispersed in an aqueous solution containing ferrous ions and grafted to obtain Fe. 2+ Dispersion of grafted carboxylated carbon nanomaterials; Using the modified wood matrix to treat the Fe 2+ The grafted carboxylated nanocarbon material dispersion was filtered, and the filtered modified wood matrix was then impregnated in the Fe... 2+ In the grafted carboxylated carbon nanomaterial dispersion, Fe 2+ Grafted carboxylated carbon nanomaterials are dispersed onto the surface and within the pores of a wood matrix to obtain Fe-loaded nanomaterials. 2+ A filter made of grafted carboxylated carbon nanomaterials; The load Fe 2+ The filter of grafted carboxylated nanocarbon material is subjected to reduction treatment, Fe 2+ The conductive wood-based filter is obtained by reducing it to nano-zero valent iron. The mass ratio of the nano-carbon material to the volume ratio of the oxidizing acid is (0.1~1)g:(100~2000)mL; The oxidation treatment is carried out at a temperature of 100~140℃ for a time of 2~36h; The mass ratio of the carboxylated carbon nanomaterial to the volume ratio of the ferrous ion-containing aqueous solution is (20~2000) mg: 1 L.

2. The method for preparing the conductive wood-based filter according to claim 1, comprising the following steps: The wood matrix is ​​mixed with an alkaline solution and modified by alkaline treatment to obtain a modified wood matrix. The nano-carbon material is mixed with an oxidizing acid and subjected to oxidation treatment to obtain carboxylated nano-carbon material; The carboxylated carbon nanomaterials were dispersed in an aqueous solution containing ferrous ions and grafted to obtain Fe. 2+ Dispersion of grafted carboxylated carbon nanomaterials; Using the modified wood matrix to treat the Fe 2+ The grafted carboxylated nanocarbon material dispersion was filtered, and the filtered modified wood matrix was then impregnated in the Fe... 2+ In the grafted carboxylated carbon nanomaterial dispersion, Fe 2+ Grafted carboxylated carbon nanomaterials are dispersed onto the surface and within the pores of a wood matrix to obtain Fe-loaded nanomaterials. 2+ A filter made of grafted carboxylated carbon nanomaterials; The load Fe 2+ The filter of grafted carboxylated nanocarbon material is subjected to reduction treatment, Fe 2+ The conductive wood-based filter is obtained by reducing it to nano-zero valent iron. The mass ratio of the nano-carbon material to the volume ratio of the oxidizing acid is (0.1~1)g:(100~2000)mL; The oxidation treatment is carried out at a temperature of 100~140℃ for a time of 2~36h; The mass ratio of the carboxylated carbon nanomaterial to the volume ratio of the ferrous ion-containing aqueous solution is (20~2000) mg: 1 L.

3. The preparation method according to claim 2, characterized in that, The wood matrix includes a natural wood matrix; the temperature of the alkali treatment modification is below the boiling point of the alkali solution; and the time of the alkali treatment modification is 10 min to 24 h.

4. The preparation method according to claim 2, characterized in that, The aqueous solution containing ferrous ions includes ferrous chloride aqueous solution, ferrous sulfate aqueous solution, or ferrous nitrate aqueous solution.

5. The preparation method according to claim 2 or 4, characterized in that, The filtration flow rate is 0.01~2.0 mL / (min·cm). 2 The immersion temperature is 20~60℃, and the time is 0.5~48h.

6. The preparation method according to claim 2, characterized in that, The reduction treatment includes thermal reduction treatment, room temperature reducing agent reduction treatment, or hydrothermal reduction treatment.

7. The application of the conductive wood-based filter according to claim 1 or the conductive wood-based filter prepared by the preparation method according to any one of claims 2 to 6 in filtering water containing Cr(VI).

8. The application according to claim 7, characterized in that, The method for filtering water containing Cr(VI) includes the following steps: constructing an electrochemical assisted filtration system using a conductive wood-based filter as the cathode and a metal mesh as the anode, and passing the water containing Cr(VI) through the conductive wood-based filter under the condition of an applied electric field.

9. The application according to claim 8, characterized in that, The metal mesh may be made of titanium, stainless steel or platinum; the operating voltage of the conductive wood-based filter is -0.5 to -5.0V.