Biochar composite material as well as preparation method and application thereof

Abstract

The invention discloses a biochar composite material and a preparation method and application thereof, and the preparation method comprises the following steps: drying and crushing a biomass material, and carbonizing to obtain a biomass carbide; crushing and grinding the biomass carbide, uniformly mixing the crushed and ground biomass carbide with the recycled thermoplastic plastic, and then crushing and hot-press molding the blend; carbonizing the shaped biochar / plastic composite material again to obtain a composite carbide; and activating the composite carbide with high-pressure water vapor, and drying to obtain the biochar composite material. The biochar composite material prepared by the method disclosed by the invention is low in cost, high in adsorption capacity, moldable, good in durability and capable of adapting to adsorption of metal ions with various concentrations.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage purification, and particularly relates to a biochar composite material, a preparation method thereof, and an application thereof. Background Art

[0003] At present, the technologies for heavy metal separation and extraction include chemical methods and physical methods. Chemical methods such as chemical adsorption method, electrolysis method, chelation method, etc. Although the chemical adsorption method is simple to operate, it is not suitable for the separation and extraction of heavy metal ions in dilute solutions; the electrolysis method is suitable for the treatment of electrolytic wastewater, but not suitable for treating heavy metal ion wastewater with low concentration; the chelation method realizes removal by adding a heavy metal capturer to form a chelate with heavy metal ions. Although its efficiency is high, the operation cost is high. Physical methods such as ion exchange method, membrane separation method, solvent extraction method, adsorption method, etc. Although the ion exchange method has good effects, the cost is high; the membrane separation method is mainly suitable for small-batch wastewater treatment, and the treatment efficiency is not high; the solvent extraction method requires a large amount of extractant, resulting in an increase in cost.

[0004] The adsorption method uses adsorbents (such as zeolite, montmorillonite, carbon materials, etc.) to adsorb heavy metals in wastewater. This method is simple to operate and has a high removal efficiency. Among them, biochar materials derived from plants such as bagasse, fruit shells, wood powder, rice bran, etc. are materials with low cost and high adsorption efficiency, and can adapt to the adsorption of metal ions at various concentrations. However, the loss of the adsorbent is relatively large, and the recycling ability and durability are often poor; moreover, the shrinkage rate of plant-derived biomass after carbonization is relatively large, and it is difficult to form various shapes. Summary of the Invention

[0005] To overcome the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a biochar composite material, a preparation method thereof, and an application thereof. The biochar composite material prepared by this method has low cost, strong adsorption ability, can be formed, and has good durability, and can adapt to the adsorption of metal ions at various concentrations.

[0006] The present invention is realized through the following technical solutions:

[0007] A preparation method of a biochar composite material includes the following steps:

[0008] S1: Dry and crush the biomass material, and then carbonize it to obtain a biomass carbide;

[0009] S2: After crushing and grinding the biomass carbide, mix it evenly with recycled thermoplastic plastic, and then break the blend and hot press it into shape to obtain a shaped biochar / plastic composite material;

[0010] S3: Carbonize the shaped biochar / plastic composite material again to obtain a composite carbide;

[0011] S4: Activate the composite carbide with high-pressure steam and then dry it to obtain the biochar composite material.

[0012] Furthermore, in the above step S1, the biomass material is derived from the biomass of trees or crops, preferably the biomass resources of tropical and subtropical broad-leaved forest leaves such as eucalyptus and banyan trees, or tropical crops such as sugarcane. Such biomass resources have well-developed pores, and their biochar can retain a rich and well-developed pore structure, with strong adsorption capacity for metal ions. Preferably, the biomass material is selected from one or more of banyan tree leaves, eucalyptus leaves, sugarcane bagasse, water hyacinth, wood powder, rice bran, and rice straw.

[0013] Furthermore, in the above step S1, the moisture content of the biomass material after drying is less than 20%, preferably less than 10%.

[0014] Furthermore, in the above step S1, the particle size of the crushed biomass material is 1 - 10 mm.

[0015] Furthermore, in the above step S1, the carbonization is carried out in a protective atmosphere. The protective atmosphere can be a nitrogen or argon atmosphere. The time for passing the protective gas is 5 - 30 min, preferably 10 - 20 min. The flow rate of the protective gas is 1 - 100 ml / min, preferably 2 - 50 ml / min. The carbonization is carried out by heating to 300 - 700 °C at a rate of 5 - 10 °C / min and holding for 30 - 300 min.

[0016] Furthermore, in the above step S2, the biomass carbide is crushed and ground to a particle size of 0.15 - 0.25 mm to reduce the content of macroporous biochar. The equipment for crushing and grinding can be a cooking machine, a traditional Chinese medicine crusher, a planetary ball mill, or other crushing equipment with a refinement function.

[0017] Furthermore, in the above step S2, the recycled thermoplastic plastic is one or more of polyethylene, polypropylene, polystyrene, polyvinyl chloride, polymethyl methacrylate, polyethylene terephthalate, acrylonitrile-butadiene-styrene copolymer, polyamide, or polycarbonate, preferably polyethylene, polypropylene, polystyrene, or polyvinyl chloride.

[0018] Furthermore, in the above step S2, the mass ratio of the biomass carbide to the recycled thermoplastic plastic is 90:10 - 60:40, and the mixing time is 5 - 20 min. The blending equipment can be a kneader, an open mill, an extruder, or a Banbury mixer. The blend is crushed to a particle size of 0.15 - 0.25 mm.

[0019] Further, in the above step S2, an interfacial modifier is added to the blend to enhance the bonding strength between the biochar and the recycled thermoplastic; the interfacial modifier is a graft copolymer of a thermoplastic and a functional monomer, and the functional monomer is one or several of styrene, methylstyrene, maleic anhydride, or glycidyl methacrylate; the grafting rate of the graft copolymer is 0.5-10%.

[0020] Further, in the above step S3, the carbonization is carried out in a protective atmosphere, and the protective atmosphere can be a nitrogen or argon atmosphere. The time for passing the protective gas is 5-30 min, preferably 10-20 min; the flow rate of the protective gas is 1-100 ml / min, preferably 2-50 ml / min; the carbonization is carried out by heating to 300-900 °C at a rate of 5-10 °C / min and holding for carbonization for 30-300 min.

[0021] Further, in the above step S4, the pressure of the high-pressure steam activation is 35 kPa-80 kPa, the temperature is 100-120 °C, and the activation time is 30-120 min; the drying temperature is 60-120 °C, and the drying time is 60-600 min.

[0022] The present invention also provides a biochar composite material prepared by the above preparation method.

[0023] The present invention also provides the application of the above biochar composite material in the treatment of heavy metal-containing wastewater. This biochar composite material is not only suitable for the adsorption of heavy metal ions such as lead ions, chromium ions, cadmium ions, and mercury ions, but also suitable for the adsorption of metal ions such as copper ions, iron ions, zinc ions, and nickel ions.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention selects plant-derived biomass materials with a relatively high porosity. First, the plant-derived biomass materials are carbonized. On the one hand, the pores of the carbon materials can be well retained. On the other hand, the shrinkage rate of the plant-derived biomass during carbonization can be reduced, achieving the effects of reducing the deformation of the composite carbide after subsequent blending with the recycled thermoplastic and maintaining a good porosity, thereby improving the adsorption capacity of the biochar material;

[0026] The present invention mixes the biomass carbide with the recycled thermoplastic. With the help of the thermoplastic forming ability of the recycled thermoplastic, various shaped products can be easily prepared, and at the same time, the loss of biochar powder can be avoided, improving the recycling ability and durability of the biochar material;

[0027] The shaped biochar / plastic composite material of the present invention is carbonized again and then activated with high-pressure steam. The composite carbide can efficiently dredge the pores of the biochar through high-pressure steam, obtaining biochar with a high porosity, thereby further enhancing the adsorption capacity of the biochar. This method has a simple process, safe equipment, and strong universality;

[0028] The biochar composite material of the present invention is prepared from waste plant-derived biomass and waste thermoplastic plastics as raw materials, with low cost, realizing the transformation and high-value utilization of biomass resources and waste plastics. Specific embodiments

[0029] The present invention will be further described below through specific embodiments. The following embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the following embodiments.

[0030] Example 1:

[0031] Put 100 g of Ficus virens leaves with a particle size of 1 - 3 mm into a tube furnace, introduce nitrogen at a flow rate of 2 ml / min for 10 min, heat up to 500 °C at a rate of 5 °C / min, after a carbonization time of 300 min, naturally cool to room temperature, take out and grind with a ball mill to 0.25 mm;

[0032] Take 70 g of Ficus virens leaf biochar with a particle size of 0.25 mm, 7 g of a graft copolymer of polyethylene and maleic anhydride-styrene with a particle size of 0.25 mm, and mix evenly with 30 g of recycled polyethylene with a particle size of 0.15 mm. Mix evenly on an open mill at 180 °C, cool and then crush with a crusher into a powder with a particle size of 0.25 mm. Put the powder into a rectangular mold frame and hot press it at 180 °C;

[0033] Put the shaped biochar / recycled polyethylene composite material into a muffle furnace, introduce nitrogen at a flow rate of 5 ml / min for 10 min, heat up to 500 °C, after a carbonization time of 180 min, naturally cool to room temperature;

[0034] Take 30 g of the carbonized rectangular composite carbide and put it into a pressure cooker containing 500 ml of water with a rated pressure of 70 kPa, steam at 100 °C for 40 minutes, take out and dry it in an oven at 120 °C for 300 minutes to obtain a sample.

[0035] Example 2:

[0036] Put 100 g of bagasse with a particle size of 5 - 10 mm into a muffle furnace, introduce nitrogen at a flow rate of 10 ml / min for 10 min, heat up to 800 °C at a rate of 5 °C / min, after a carbonization time of 180 min, naturally cool to room temperature, take out and grind with a ball mill to 0.25 mm;

[0037] Take 70 g of bagasse biochar with a particle size of 0.25 mm, 7 g of a graft copolymer of polypropylene and glycidyl methacrylate - styrene with a particle size of 0.25 mm, and mix them evenly with 30 g of recycled polypropylene with a particle size of 0.25 mm. Mix them evenly on an open mill at 180 °C, and after cooling, crush them into powder with a particle size of 0.18 mm using a crusher. Place the powder in a rectangular mold frame and hot - press it on a flat vulcanizer at 180 °C;

[0038] Put the shaped biochar / recycled polypropylene composite material into a muffle furnace, introduce nitrogen at a flow rate of 8 ml / min for 10 min, heat up to 800 °C, and after a carbonization time of 180 min, cool it naturally to room temperature;

[0039] Take 40 g of the carbonized rectangular composite carbide and put it into a pressure cooker containing 800 ml of water with a rated pressure of 70 kPa. Steam it at 110 °C for 40 minutes, take it out and dry it in an oven at 120 °C for 300 minutes to obtain a sample.

[0040] Example 3:

[0041] Put 100 g of water hyacinth powder with a particle size of 1 - 5 mm into a muffle furnace, introduce argon at a flow rate of 3 ml / min for 10 min, heat up at a rate of 5 °C / min to 600 °C, and after a carbonization time of 300 min, cool it naturally to room temperature. Take it out and grind it to 0.18 mm using a ball mill;

[0042] Take 90 g of water hyacinth biochar with a particle size of 0.18 mm, 9 g of a graft copolymer of polyethylene and maleic anhydride - styrene with a particle size of 0.18 mm, and mix them evenly with 10 g of recycled polyethylene with a particle size of 0.18 mm using a kneader. Mix them evenly on an internal mixer at 180 °C, and after cooling, crush them into powder with a particle size of 0.18 mm using a crusher. Place the powder in a rectangular mold frame and hot - press it on a flat vulcanizer at 180 °C;

[0043] Put the shaped biochar / recycled polyethylene composite material into a muffle furnace, introduce argon at a flow rate of 5 ml / min for 10 min, heat up to 700 °C, and after a carbonization time of 200 min, cool it naturally to room temperature;

[0044] Take 30 g of the carbonized rectangular composite carbide sample and put it into a pressure cooker containing 600 ml of water with a rated pressure of 70 kPa. Steam it at 120 °C for 40 minutes, take it out and dry it in an oven at 120 °C for 360 minutes to obtain a sample.

[0045] Comparative Example 1:

[0046] Put 100 g of Ficus virens leaves with a particle size of 1 - 3 mm into a tubular furnace, introduce nitrogen at a flow rate of 2 ml / min for 10 min, heat up to 500 °C at a rate of 5 °C / min, after carbonization for 300 min, naturally cool to room temperature, take out and grind with a ball mill to 0.25 mm;

[0047] Take 70 g of Ficus virens leaf biochar with a particle size of 0.25 mm, 7 g of graft copolymer of polyethylene and maleic anhydride - styrene with a particle size of 0.25 mm, and mix evenly with 30 g of recycled polyethylene with a particle size of 0.15 mm. Mix evenly on an open mill at 180 °C, and after cooling, crush with a crusher into a powder with a particle size of 0.25 mm. Put the powder into a rectangular mold frame and hot - press at 180 °C;

[0048] Put the shaped biochar / recycled polyethylene composite material into a muffle furnace, introduce nitrogen at a flow rate of 5 ml / min for 10 min, heat up to 500 °C, after carbonization for 180 min, naturally cool to room temperature to obtain a sample.

[0049] Comparative Example 2:

[0050] Put 100 g of Ficus virens leaves with a particle size of 1 - 3 mm into a tubular furnace, introduce nitrogen at a flow rate of 2 ml / min for 10 min, heat up to 500 °C at a rate of 5 °C / min, after carbonization for 300 min, naturally cool to room temperature, take out and grind with a ball mill to 0.25 mm;

[0051] Take 70 g of Ficus virens leaf biochar with a particle size of 0.25 mm, 7 g of graft copolymer of polyethylene and maleic anhydride - styrene with a particle size of 0.25 mm, and mix evenly with 30 g of recycled polyethylene with a particle size of 0.15 mm. Mix evenly on an open mill at 180 °C, and after cooling, crush with a crusher into a powder with a particle size of 0.25 mm. Put the powder into a rectangular mold frame and hot - press at 180 °C;

[0052] Put the shaped biochar / recycled polyethylene composite material into a muffle furnace, introduce nitrogen at a flow rate of 5 ml / min for 10 min, heat up to 500 °C, after carbonization for 180 min, naturally cool to room temperature;

[0053] Take 30 g of the carbonized rectangular composite carbide sample and put it into an atmosphere rotary furnace, heat up to 500 °C, introduce water vapor at 20 kPa for 40 minutes, take out and put it into an oven at 120 °C to dry for 300 minutes to obtain a sample.

[0054] Comparative Example 3:

[0055] Take 70 g of Ficus virens leaves powder with a particle size of 0.25 mm, 7 g of graft copolymer of polyethylene and maleic anhydride-styrene, and mix them evenly with 30 g of recycled polyethylene with a particle size of 0.15 mm. Mix them evenly on an open mill at 180 °C, and after cooling, crush them into powder with a particle size of 0.25 mm using a crusher. Put the powder into a rectangular mold frame and hot press it at 180 °C;

[0056] Put the shaped biochar / recycled polyethylene composite material into a muffle furnace, introduce nitrogen at a flow rate of 5 ml / min for 10 min, heat up to 500 °C, and after carbonization for 180 min, naturally cool to room temperature;

[0057] Take 30 g of the carbonized rectangular composite carbide and put it into a pressure cooker containing 500 ml of water and with a rated pressure of 70 kPa, steam it at 100 °C for 40 minutes, take it out and dry it in an oven at 120 °C for 300 minutes to obtain the sample.

[0058] Comparative Example 4:

[0059] Put 100 g of Ficus virens leaves with a particle size of 1 - 3 mm into a tubular furnace, introduce nitrogen at a flow rate of 2 ml / min for 10 min, heat up to 500 °C at a rate of 5 °C / min, and after carbonization for 300 min, naturally cool to room temperature, take it out and grind it to 0.25 mm with a ball mill;

[0060] Take 70 g of Ficus virens leaves biochar with a particle size of 0.25 mm, 7 g of graft copolymer of polyethylene and maleic anhydride-styrene with a particle size of 0.25 mm, and mix them evenly with 30 g of recycled polyethylene with a particle size of 0.15 mm, then put them into a muffle furnace, introduce nitrogen at a flow rate of 5 ml / min for 10 min, heat up to 500 °C, and after carbonization for 180 min, naturally cool to room temperature;

[0061] Take 30 g of the carbonized composite carbide and put it into a pressure cooker containing 500 ml of water and with a rated pressure of 70 kPa, steam it at 100 °C for 40 minutes, take it out and dry it in an oven at 120 °C for 300 minutes to obtain the sample. Performance test method:

[0062] Take 200 ml of a divalent copper ion standard solution with a concentration of 1000 mg / L into a 500 mL conical flask.

[0063] The maximum adsorption capacity of biochar: Through an isothermal adsorption experiment, obtain the isothermal adsorption curve of a certain amount of biochar for metal ions in the solution, and thus calculate the maximum adsorption capacity of biochar.

[0064] Metal ion removal rate: The content of metal ions was determined by flame atomic absorption spectrometry. The metal ion removal rate was calculated according to the formula: R = (m0 - m1) / m0, where m0 is the content of metal ions in the original solution and m1 is the content of the remaining metal ions in the solution after adsorption.

[0065] Porosity: The porosity of biochar was measured by a specific surface area and pore size analyzer.

[0066] Biochar loss rate: A certain mass of the biochar composite material sample was weighed. The biochar composite material sample was wrapped with gauze and steamed in a pressure cooker for a certain period of time. After taking it out, it was dried and weighed. The ratio of the mass difference before and after the steaming treatment to the mass before the steaming treatment was used to evaluate the biochar loss rate.

[0067] Shrinkage rate: The volume shrinkage rate was used. According to the ratio of the change in the sample size before and after carbonization to the sample size before carbonization, the volume shrinkage rate of the sample was obtained.

[0068] The performance results of each sample are shown in Table 1:

[0069] Table 1 Performance test results of examples and comparative examples

[0070]

[0071] For Comparative Example 1, the composite carbide was not activated with high-pressure steam. The porosity, shrinkage rate, maximum adsorption capacity, and metal ion removal rate of the prepared biochar composite material were significantly worse than those of Example 1.

[0072] For Comparative Example 2, the composite carbide was activated with high-temperature and low-pressure steam. Compared with Example 1, its diffusion and dredging ability was poor, the porosity of the prepared biochar composite material was low, and the adsorption ability was poor.

[0073] For Comparative Example 3, the biomass material was not carbonized first, the porosity was low, the adsorption ability was poor, and the shrinkage rate was significantly higher than that of Example 1.

[0074] For Comparative Example 4, the biochar and recycled thermoplastic were simply mixed and then directly carbonized without the hot pressing and molding step. The biochar loss rate and shrinkage rate of the prepared biochar composite material were significantly higher than those of Example 1.

[0075] The results of the above examples and comparative examples show that in the present invention, the plant-derived biomass material is first carbonized, then the biomass carbide is mixed with the recycled thermoplastic, hot pressed and molded, and then the shaped biochar / plastic composite material is carbonized again and activated with high-pressure steam. With the synergistic effect of each step, the prepared biochar composite material has high porosity, strong adsorption ability, low shrinkage rate, low biochar powder loss rate, good durability, and can adapt to the adsorption of metal ions at various concentrations.

Claims

1. A method for preparing a biochar composite material, characterized in that: The steps include: S1: drying and crushing the biomass material and then carbonizing it to obtain a biomass carbonized product; S2: After the biomass carbonization is crushed and ground, it is mixed evenly with the recycled thermoplastics, and then the blend is crushed and hot pressed. Forming to obtain a shaped biochar / plastic composite material; S3: carbonizing the shaped biochar / plastic composite material again to obtain a composite carbonized product; S4: activating the composite carbonized product with high-pressure steam and then drying it to obtain a biochar composite material.

2. The method for preparing the biochar composite material according to claim 1, characterized in that: In step S1, the biomass material is selected from one or more of banyan leaves, eucalyptus leaves, bagasse, water hyacinth, wood powder, rice bran, and rice straw; the moisture content of the biomass material after drying is lower than 20%, preferably lower than 10%; the particle size of the biomass material after crushing is 1-10 mm.

3. The method for preparing the biochar composite material according to claim 1, characterized in that: In step S1, the carbonization is carried out in a protective atmosphere, the protective gas is passed for 5 to 30 minutes, and the flow rate is 1 to 100 ml / min; the carbonization is carried out by heating the material to 300 to 700° C. at a rate of 5 to 10° C. / min and carbonizing the material at a constant temperature for 30 to 300 minutes.

4. The method for preparing the biochar composite material according to claim 1, characterized in that: In step S2, the biomass carbonized material is crushed and ground to a particle size of 0.15-0.25 mm; the recycled thermoplastic plastic is one or more of polyethylene, polypropylene, polystyrene, polyvinyl chloride, polymethyl methacrylate, polyethylene terephthalate, acrylonitrile-butadiene-styrene copolymer, polyamide or polycarbonate.

5. The method for preparing the biochar composite material according to claim 1, characterized in that: In step S2, the mass ratio of the biomass carbonized material to the recycled thermoplastic plastic is 90:10-60:40, and the mixing time is 5-20 min; the particle size of the blend is 0.15-0.25 mm.

6. The method for preparing the biochar composite material according to claim 1, characterized in that: In step S2, an interfacial modifier is added to the blend, wherein the interfacial modifier is a graft copolymer of a thermoplastic and a functional monomer, wherein the functional monomer is one or more of styrene, methyl styrene, maleic anhydride or glycidyl methacrylate; and the graft rate of the graft copolymer is 0.5-10%.

7. The method for preparing the biochar composite material according to claim 1, characterized in that: In step S3, the carbonization is carried out in a protective atmosphere, the protective gas is passed for 5 to 30 minutes, and the flow rate is 1 to 100 ml / min; the carbonization is carried out by heating the temperature to 300 to 900° C. at a rate of 5 to 10° C. / min and carbonizing at a constant temperature for 30 to 300 minutes.

8. The method for preparing the biochar composite material according to claim 1, characterized in that: In step S4, the pressure of the high-pressure steam activation is 35 kPa~80 kPa, the temperature is 100~120°C, and the activation time is 30~120 min; the drying temperature is 60~120°C, and the drying time is 60~600 min.

9. A biochar composite material prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the biochar composite material according to claim 9 in the treatment of heavy metal-containing wastewater.

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