A biochar composite material, and a preparation method and application thereof

Abstract

The application discloses a kind of biochar composite material and its preparation method and application, including steps: after drying, pulverizing biomass material, carbonization is carried out, and biomass carbonization product is obtained;After grinding, biomass carbonization product is pulverized, and then mixed uniformly with recycled thermoplastic plastic, then the blend is broken, and hot-pressing is formed;The shaped biochar / plastic composite material is carbonized again to obtain composite carbonization product;After drying, the composite carbonization product is activated by high-pressure steam, and biochar composite material is obtained.The biochar composite material prepared by the method of the application has low cost, strong adsorption capacity, can be formed and has good durability, and can adapt to the adsorption of metal ions of various concentrations.

Description

TECHNICAL FIELD

[0001] The present application relates to the sewage purification technical field, specifically relates to a kind of biochar composite material and its preparation method and application. BACKGROUND

[0002] At present, the technology of heavy metal separation and extraction has chemical method and physical method. Chemical method such as chemical adsorption method, electrolysis method, chelation method etc. Although chemical adsorption method is simple to operate, it is not suitable for the separation and extraction of heavy metal ions in dilute solution;Electrolysis method is suitable for the treatment of electrolytic wastewater, but it is not suitable for the treatment of low concentration heavy metal ion wastewater;Chelation method removes by adding heavy metal capture agent to form chelate with heavy metal ions, although its efficiency is high, but the operation cost is high. Physical method such as ion exchange method, membrane separation method, solvent extraction method, adsorption method etc. Although ion exchange method has good effect, but the cost is high;Membrane separation method is mainly suitable for small batch wastewater treatment, and the treatment efficiency is not high;Solvent extraction method needs to consume a large amount of extractant, which leads to the increase of cost.

[0003] Adsorption method is to use adsorbent (such as zeolite, montmorillonite, carbon material etc.) to adsorb heavy metals in wastewater. This method is simple to operate and has high removal efficiency, among which the plant source biochar material such as bagasse, fruit shell, wood powder and rice chaff has low cost and high adsorption efficiency, and can adapt to the adsorption of heavy metal ions with various concentrations, but the loss of adsorbent is large, and the recycling ability and durability are often poor. In addition, the shrinkage rate of plant source biochar is large after carbonization, and it is difficult to form various shapes. SUMMARY

[0004] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a kind of biochar composite material and its preparation method and application. The biochar composite material prepared by the method has low cost, strong adsorption capacity, can be formed and has good durability, and can adapt to the adsorption of heavy metal ions with various concentrations.

[0005] The present application is realized by the following technical scheme:

[0006] A preparation method of biochar composite material, comprising the following steps:

[0007] S1: drying and crushing the biomass material, then carbonizing to obtain biomass carbonization product;

[0008] S2: crushing and grinding the biomass carbonization product, then uniformly mixing with recycled thermoplastic plastic, then crushing the blend, hot pressing to form a shaped biochar / plastic composite material;

[0009] S3: carbonizing the shaped biochar / plastic composite material again to obtain a composite carbonization product;

[0010] S4: drying the composite carbide after activation by high-pressure steam to obtain a biochar composite material.

[0011] Further, in the 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, banyan, etc., or tropical crops such as sugarcane, etc. Such biomass resources have developed pores, and the biochar thereof can retain rich and developed pore structures and has strong metal ion adsorption capacity. Preferably, the biomass material is selected from one or more of banyan leaves, eucalyptus leaves, sugarcane residues, water hyacinth, wood powder, rice chaff, and rice straw.

[0012] Further, in the step S1, the moisture content of the biomass material after drying is less than 20%, preferably less than 10%.

[0013] Further, in the step S1, the particle size of the biomass material after crushing is 1-10 mm.

[0014] Further, in the step S1, the carbonization is carried out in a protective atmosphere, which 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 at a rate of 5-10°C / min to 300-700°C and holding for 30-300 min.

[0015] Further, in the step S2, the biomass char is crushed and ground to a particle size of 0.15-0.25 mm to reduce the content of macroporous biochar. The crushing and grinding equipment can be a food processor, a traditional Chinese medicine crushing machine, a planetary ball mill, or other crushing equipment with fine function.

[0016] Further, in the 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.

[0017] Further, in the step S2, the mass ratio of the biomass char 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 an internal mixer. The blend is crushed to a particle size of 0.15-0.25 mm.

[0018] Further, in the step S2, an interface modifier is added in the blend to enhance the bonding strength between the biochar and the recycled thermoplastic plastic; the interface modifier is a graft copolymer of the thermoplastic plastic and a functional monomer, the functional monomer is one or more of styrene, methyl styrene, maleic anhydride or glycidyl methacrylate; the grafting rate of the graft copolymer is 0.5-10%.

[0019] Further, in the step S3, the carbonization is carried out in a protective atmosphere, the protective atmosphere can be a nitrogen or argon atmosphere, the time of 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 at a rate of 5-10 ℃ / min to 300-900 ℃ for constant temperature carbonization for 30-300 min.

[0020] Further, in the step S4, the pressure of the high-pressure steam activation is 35 kPa-80 kPa, the temperature is 100-120 ℃, and the activation time is 30-120 min; the drying temperature is 60-120 ℃, and the drying time is 60-600 min.

[0021] The application also provides a biochar composite material prepared by the above preparation method.

[0022] The application also provides an application of the above biochar composite material in heavy metal-containing wastewater treatment, and the biochar composite material is suitable for adsorption of heavy metal ions such as lead ions, chromium ions, cadmium ions and mercury ions, and is also suitable for adsorption of metal ions such as copper ions, iron ions, zinc ions and nickel ions.

[0023] Compared with the prior art, the application has the following beneficial effects:

[0024] In the application, the plant source biomass material with relatively high porosity is selected, and the plant source biomass material is carbonized, which can well retain the pores of the carbon material and reduce the shrinkage of the plant source biomass during the carbonization process, so that the deformation of the subsequent composite carbonized product after blending with the recycled thermoplastic plastic and the good porosity are achieved, and the adsorption capacity of the biochar material is improved.

[0025] In the application, the biomass carbonized product is mixed with the recycled thermoplastic plastic, various shaped products can be simply prepared by means of the thermoplastic forming capacity of the recycled thermoplastic plastic, the loss of the biochar powder is avoided, and the recycling capacity and durability of the biochar material are improved.

[0026] The shaped biochar / plastic composite material is carbonized again, and then activated by high-pressure steam, the composite char can efficiently dredge the pores of the biochar by high-pressure steam, and high-porosity biochar is obtained, so that the adsorption capacity of the biochar is further enhanced, and the method has the advantages of simple process, safe equipment and strong universality.

[0027] The biochar composite material is prepared by using waste plant biomass and waste thermoplastic plastic as raw materials, and has the advantages of low cost, and realizes the transformation and high-value utilization of biomass resources and waste plastics. DETAILED DESCRIPTION

[0028] The application will be further described by specific embodiments, and the following embodiments are preferred embodiments of the application, but the embodiments of the application are not limited by the following embodiments.

[0029] Example 1:

[0030] 100g of large-leaf banyan leaves with a particle size of 1-3mm were put into a tube furnace, nitrogen was passed at a flow rate of 2ml / min for 10min, the temperature was raised to 500℃ at a speed of 5℃ / min, and after carbonization for 300min, it was naturally cooled to room temperature, and then taken out and ground to 0.25mm by a ball mill;

[0031] 70g of large-leaf banyan leaf biochar with a particle size of 0.25mm, 7g of polyethylene grafted with maleic anhydride-styrene with a particle size of 0.25mm, and 30g of recycled polyethylene with a particle size of 0.15mm were mixed uniformly on a mill at 180℃, and then cooled and crushed into a powder with a particle size of 0.25mm by a crusher; the powder was put into a rectangular mold and hot-pressed at 180℃;

[0032] The shaped biochar / recycled polyethylene composite material was put into a muffle furnace, nitrogen was passed at a flow rate of 5ml / min for 10min, the temperature was raised to 500℃, and after carbonization for 180min, it was naturally cooled to room temperature;

[0033] 30g of the carbonized rectangular composite char was put into a high-pressure pot containing 500ml of water with a rated pressure of 70kPa, and steamed at 100℃ for 40min, then taken out and dried in an oven at 120℃ for 300min to obtain a sample.

[0034] Example 2:

[0035] 100g of sugarcane residue with a particle size of 5-10mm was put into a muffle furnace, nitrogen was passed at a flow rate of 10ml / min for 10min, the temperature was raised to 800℃ at a speed of 5℃ / min, and after carbonization for 180min, it was naturally cooled to room temperature, and then taken out and ground to 0.25mm by a ball mill;

[0036] 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 30 g of recycled polypropylene with a particle size of 0.25 mm, mix them evenly, mix them evenly on an open mill at 180°C, and after cooling, use a crusher to crush them into a powder with a particle size of 0.18 mm. Put the powder into a rectangular mold and heat press it into a flat vulcanizing machine at 180°C;

[0037] Put the shaped biochar / recycled polypropylene composite material into a muffle furnace, pass nitrogen gas at a flow rate of 8 ml / min for 10 min, heat it to 800°C, carbonize it for 180 min, and then naturally cool it to room temperature;

[0038] Take 40 g of the carbonized rectangular composite carbonizate 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 min, take it out and dry it in an oven at 120°C for 300 min to obtain the sample.

[0039] Example 3:

[0040] Put 100 g of water hyacinth powder with a particle size of 1-5 mm into a muffle furnace, pass argon gas at a flow rate of 3 ml / min for 10 min, heat it to 600°C at a rate of 5°C / min, carbonize it for 300 min, and then naturally cool it to room temperature. After taking it out, use a ball mill to grind it to 0.18 mm;

[0041] 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 10 g of recycled polyethylene with a particle size of 0.18 mm, mix them evenly through a kneader, mix them evenly on a banbury mixer at 180°C, and after cooling, use a crusher to crush them into a powder with a particle size of 0.18 mm. Put the powder into a rectangular mold and heat press it into a flat vulcanizing machine at 180°C;

[0042] Put the shaped biochar / recycled polyethylene composite material into a muffle furnace, pass argon gas at a flow rate of 5 ml / min for 10 min, heat it to 700°C, carbonize it for 200 min, and then naturally cool it to room temperature;

[0043] Take 30 g of the carbonized rectangular composite carbonizate 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 min, take it out and dry it in an oven at 120°C for 360 min to obtain the sample.

[0044] Comparative Example 1:

[0045] Put 100 g of large-leaf banyan leaves with a particle size of 1-3 mm into a tube furnace, pass nitrogen at a flow rate of 2 ml / min for 10 min, heat to 500℃ at a rate of 5℃ / min, carbonize for 300 min, and then naturally cool to room temperature. After taking out, grind to 0.25 mm with a ball mill;

[0046] Take 70 g of large-leaf banyan leaf biochar with a particle size of 0.25 mm, 7 g of polyethylene and maleic anhydride-styrene graft copolymer with a particle size of 0.25 mm, and 30 g of recycled polyethylene with a particle size of 0.15 mm, mix them evenly on a two-roll mill at 180℃, and then crush into a powder with a particle size of 0.25 mm after cooling. Put the powder into a rectangular mold and hot-press at 180℃ to form a sample.

[0047] Put the shaped biochar / recycled polyethylene composite material into a muffle furnace, pass nitrogen at a flow rate of 5 ml / min for 10 min, heat to 500℃, carbonize for 180 min, and then naturally cool to room temperature to obtain a sample.

[0048] Comparative Example 2:

[0049] Put 100 g of large-leaf banyan leaves with a particle size of 1-3 mm into a tube furnace, pass nitrogen at a flow rate of 2 ml / min for 10 min, heat to 500℃ at a rate of 5℃ / min, carbonize for 300 min, and then naturally cool to room temperature. After taking out, grind to 0.25 mm with a ball mill;

[0050] Take 70 g of large-leaf banyan leaf biochar with a particle size of 0.25 mm, 7 g of polyethylene and maleic anhydride-styrene graft copolymer with a particle size of 0.25 mm, and 30 g of recycled polyethylene with a particle size of 0.15 mm, mix them evenly on a two-roll mill at 180℃, and then crush into a powder with a particle size of 0.25 mm after cooling. Put the powder into a rectangular mold and hot-press at 180℃ to form a sample.

[0051] Put the shaped biochar / recycled polyethylene composite material into a muffle furnace, pass nitrogen at a flow rate of 5 ml / min for 10 min, heat to 500℃, carbonize for 180 min, and then naturally cool to room temperature;

[0052] Put 30 g of the carbonized rectangular composite carbonization sample into an atmosphere rotary furnace, heat to 500℃, pass in 20 kPa of water vapor for 40 min, and then take out and dry in an oven at 120℃ for 300 min to obtain a sample.

[0053] Comparative Example 3:

[0054] Take 70 g of large leaf Ficus microcarpa leaf powder with a particle size of 0.25 mm, 7 g of polyethylene and maleic anhydride-styrene graft copolymer, and 30 g of recycled polyethylene with a particle size of 0.15 mm, mix evenly, mix evenly on an open mill at 180°C, and cool it down to 0.25 mm after crushing it with a crusher. Put the powder into a rectangular mold and heat press it at 180°C;

[0055] Put the shaped biochar / recycled polyethylene composite into a muffle furnace, pass nitrogen at a flow rate of 5 ml / min for 10 min, heat to 500°C, and carbonize for 180 min, then naturally cool to room temperature;

[0056] Put 30 g of the carbonized rectangular composite into a pressure cooker containing 500 ml of water with a rated pressure of 70 kPa, steam at 100°C for 40 min, and dry it in an oven at 120°C for 300 min to obtain the sample.

[0057] Comparative Example 4:

[0058] Put 100 g of large leaf Ficus microcarpa leaves with a particle size of 1-3 mm into a tube furnace, pass nitrogen at a flow rate of 2 ml / min for 10 min, heat to 500°C at a rate of 5°C / min, and carbonize for 300 min, then naturally cool to room temperature, and grind it to 0.25 mm with a ball mill;

[0059] Take 70 g of large leaf Ficus microcarpa leaf biochar with a particle size of 0.25 mm, 7 g of polyethylene and maleic anhydride-styrene graft copolymer with a particle size of 0.25 mm, and 30 g of recycled polyethylene with a particle size of 0.15 mm, mix evenly, and put it into a muffle furnace, pass nitrogen at a flow rate of 5 ml / min for 10 min, heat to 500°C, and carbonize for 180 min, then naturally cool to room temperature;

[0060] Put 30 g of the carbonized composite into a pressure cooker containing 500 ml of water with a rated pressure of 70 kPa, steam at 100°C for 40 min, and dry it in an oven at 120°C for 300 min to obtain the sample. Performance test method:

[0061] Take 200 ml of a standard solution of divalent copper ions with a concentration of 1000 mg / L into a 500 mL conical flask.

[0062] The maximum adsorption capacity of biochar: adopt isothermal adsorption experiment, obtain the isothermal adsorption curve of a certain amount of biochar to metal ions in the solution, and calculate the maximum adsorption capacity of biochar.

[0063] Metal ion removal rate: the content of metal ions is determined by flame atomic absorption method. According to the formula: R = (m0-m1) / m0, the metal ion removal rate is calculated, wherein m0 is the content of metal ions in the original solution, and m1 is the content of residual metal ions in the solution after adsorption.

[0064] Porosity: the porosity of the biochar is measured by a specific surface area and pore size analyzer.

[0065] Biochar loss rate: a certain mass of biochar composite material sample is weighed, the biochar composite material sample is wrapped with gauze, and then is placed in a pressure cooker for a certain time. After being taken out, the sample is dried and weighed. The ratio of the mass difference before and after the steaming treatment to the mass before the steaming treatment is used to evaluate the loss rate of the biochar.

[0066] Shrinkage rate: the volume shrinkage rate is used. According to the ratio of the change amount of the sample size before and after carbonization to the sample size before carbonization, the volume shrinkage rate of the sample is obtained.

[0067] The performance results of the samples are shown in Table 1.

[0068] Table 1: Performance test results of examples and comparative examples

[0069]

[0070] The composite char of Comparative Example 1 is not activated by high-pressure steam, and the porosity, shrinkage rate, maximum adsorption capacity and metal ion removal rate of the prepared biochar composite material are all significantly worse than those of Example 1.

[0071] The composite char of Comparative Example 2 is activated by high-temperature and low-pressure steam. Compared with Example 1, its diffusion and dredging ability is poor, and the porosity of the prepared biochar composite material is low, and the adsorption capacity is poor.

[0072] The biomass material of Comparative Example 3 is not carbonized first, and the porosity is low, the adsorption capacity is poor, and the shrinkage rate is significantly higher than that of Example 1.

[0073] In Comparative Example 4, the biochar is simply mixed with the recycled thermoplastic plastic and then directly carbonized without the step of hot pressing. The loss rate and shrinkage rate of the prepared biochar are significantly higher than those of Example 1.

[0074] The results of the above examples and comparative examples show that, by carbonizing the plant-derived biomass material first, then mixing the biomass char with the recycled thermoplastic plastic, hot pressing, and then carbonizing the shaped biochar / plastic composite material and activating it by high-pressure steam, the synergistic effect of each step is achieved. The prepared biochar composite material has high porosity, strong adsorption capacity, low shrinkage rate, and low loss rate of biochar powder, has good durability, and can adapt to the adsorption of metal ions of various concentrations.

Claims

1. A method of producing a biochar composite material, characterized by, The method comprises the following steps: S1: drying and crushing the biomass material, and then carbonizing the biomass material to obtain a biomass carbonization product; the carbonization is performed in a protective atmosphere, the protective gas is supplied for 5-30 min at a flow rate of 1-100 ml / min; the carbonization is performed at a temperature increasing rate of 5-10 ℃ / min to 300-700 ℃, and then carbonized at a constant temperature for 30-300 min; S2: crushing and grinding the biomass carbonization product, and then uniformly mixing the biomass carbonization product with recycled thermoplastic plastic and an interface modifier on an open mill or an internal mixer at 180 ℃, crushing the blend, and hot-pressing the blend at 180 ℃ to obtain a shaped biomass carbon / plastic composite material; the interface modifier is a graft copolymer of the thermoplastic plastic and a functional monomer, and the functional monomer is one or more of styrene, methylstyrene, maleic anhydride, and glycidyl methacrylate; S3: carbonizing the shaped biomass carbon / plastic composite material again to obtain a composite carbonization product; the carbonization is performed in a protective atmosphere, the protective gas is supplied for 5-30 min at a flow rate of 1-100 ml / min; the carbonization is performed at a temperature increasing rate of 5-10 ℃ / min to 300-900 ℃, and then carbonized at a constant temperature for 30-300 min; S4: drying the composite carbonization product after high-pressure steam activation to obtain a biomass carbon composite material; the high-pressure steam activation is performed at a pressure of 35 kPa-80 kPa, a temperature of 100-120 ℃, and for 30-120 min.

2. The method of claim 1, wherein: In step S1, the biomass material is selected from one or more of the following: leaves of ficus microcarpa, leaves of eucalyptus, bagasse, water hyacinth, wood powder, rice chaff, and rice straw; the moisture content of the dried biomass material is less than 20%; and the particle size of the crushed biomass material is 1-10 mm.

3. The method of claim 2, wherein: In step S1, the moisture content of the dried biomass material is less than 10%.

4. The method of claim 1, wherein: In step S2, the biomass carbonization product is crushed and ground to a particle size of 0.15-0.25 mm; and the recycled thermoplastic plastic is one or more of the following: polyethylene, polypropylene, polystyrene, polyvinyl chloride, polymethyl methacrylate, polyethylene terephthalate, acrylonitrile-butadiene-styrene copolymer, polyamide, and polycarbonate.

5. The method of claim 1, wherein: In step S2, the biomass carbonization product and the recycled thermoplastic plastic are mixed at a mass ratio of 90:10-60:40, and the mixing time is 5-20 min; and the particle size of the crushed blend is 0.15-0.25 mm.

6. The method of claim 1, wherein: In step S2, the grafting rate of the graft copolymer is 0.5-10%.

7. The method of claim 1, wherein: In step S4, the drying is performed at a temperature of 60-120 ℃ for 60-600 min.

8. A biomass carbon composite material prepared by the method of any one of claims 1-7.

9. Use of the biomass carbon composite material of claim 8 in the treatment of wastewater containing heavy metals.

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