A metal-modified polyethylene-based functional carbon material and its preparation method and application

Abstract

The present invention belongs to the technical field of adsorption materials, and specifically relates to a metal-modified polyethylene-based functional carbon material, its preparation method, and its application. The present invention pre-treats polyethylene through a hydrothermal method, thereby reducing the oil yield of polyethylene during the pyrolysis process and obtaining a high carbon yield at a relatively low carbonization temperature, thus overcoming the problems of harsh carbonization conditions and low carbonization rate of polyethylene at low temperatures. By introducing metals during the carbonization process, the present invention not only increases the solid carbon yield, but also improves the adsorption performance of the metal-modified polyethylene-based functional carbon material for harmful substances such as nitrogen and phosphorus in wastewater, resulting in a large adsorption capacity, a high adsorption rate, and a high harmful substance removal rate. The metal-modified polyethylene-based functional carbon material of the present invention is recyclable and has great economic and environmental value. The results of the examples show that the metal-modified polyethylene-based functional carbon material of the present invention has a phosphorus removal rate of 79.3-99.5% for wastewater, a nitrogen removal rate of 80.5-85% for wastewater, and a solid carbon yield of over 60%.

Description

Technical Field

[0001] The present invention belongs to the technical field of adsorption materials, and in particular relates to a metal-modified polyethylene-based functional carbon material and a preparation method and application thereof. Background Art

[0002] Phosphorus, an essential nutrient for plant growth, is widely used in agriculture and industry, making significant contributions to economic and social development. However, with the growth of human activities, phosphate pollution of water bodies has become increasingly serious. Phosphate pollution can lead to eutrophication, which in turn causes oxygen depletion in the water, leading to a series of environmental problems such as the death of aquatic plants and animals.

[0003] At present, the main methods for removing phosphorus from water bodies are chemical precipitation, biological methods and adsorption methods. Chemical precipitation is the most commonly used method for phosphorus removal, but it is mainly suitable for the removal of high-concentration phosphates. When treating low-concentration phosphates, a large amount of chemical agents need to be added, causing secondary pollution. Biological methods do not require the addition of chemical agents during the phosphorus removal process, which is more economical and environmentally friendly, but has higher requirements for the treatment environment and water quality. Compared with other technologies, adsorption methods have attracted the attention of researchers due to their convenience, economy, high selectivity and low possibility of secondary pollution. In particular, functional carbon materials that can be synthesized from waste solid materials (such as agricultural solid waste, sewage and sludge, etc.) are the most widely used adsorbents in adsorption water treatment. Functional carbon materials have a high specific surface area, large porosity, good pore structure and a large number of oxygen-containing functional groups, which are conducive to the adsorption process. However, the existing functional carbon materials generally have insufficient adsorption capacity.

[0004] Polyethylene is widely used as a packaging material and agricultural mulch film, but this also results in a large amount of polyethylene solid waste. Polyethylene is highly stable and difficult to degrade under natural conditions, which can easily pollute the environment. Currently, the main way plastics degrade is through pyrolysis, which has a high pyrolysis carbonization temperature, generally above 1000°C. When the pyrolysis temperature is above 700°C, it mainly produces olefin mixtures and oily aromatic mixtures. When the pyrolysis temperature is low, such as 400-600°C, it produces high calorific value gases, oils, waxes, etc. The yield of solid carbon (coke) produced during the pyrolysis of polyethylene is relatively low. Increasing the temperature can achieve a higher yield, but the cost of preparing functional carbon materials increases accordingly. Summary of the Invention

[0005] The purpose of the present invention is to provide a metal-modified polyethylene-based functional carbon material and its preparation method and application. The preparation method provided by the present invention has low cost, and the obtained metal-modified polyethylene-based functional carbon material has a large adsorption capacity and a high solid carbon yield.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a metal-modified polyethylene-based functional carbon material, comprising the following steps:

[0008] (1) crushing the polyethylene raw material and then subjecting it to ball milling and hydrothermal pretreatment to obtain a polyethylene hydrothermal product;

[0009] (2) mixing the polyethylene hydrothermal product and a metal inorganic substance and carbonizing them to obtain a metal-modified polyethylene-based functional carbon material; the carbonization temperature is 400 to 900°C.

[0010] Preferably, the amount of water added in the hydrothermal pretreatment is 5 to 9 mL / g.

[0011] Preferably, the metal inorganic substance includes one or more of a calcium inorganic substance, a magnesium inorganic substance and a rhenium inorganic substance.

[0012] Preferably, the temperature of the hydrothermal pretreatment is 150-220° C., and the holding time is 12-36 hours.

[0013] Preferably, the mass ratio of the polyethylene hydrothermal product to the metal inorganic substance is 1:2-6.

[0014] Preferably, the carbonization holding time is 0.5 to 4 hours.

[0015] Preferably, the target particle size of the ball milling is no greater than 250 microns.

[0016] Preferably, after the carbonization, the obtained carbonized product is washed; the washing is performed 2 to 3 times.

[0017] The present invention also provides a metal-modified polyethylene-based functional carbon material obtained by the preparation method described in the above scheme, comprising a polyethylene-based functional carbon material and metal ions loaded on the metal-modified polyethylene-based functional carbon material.

[0018] The present invention also provides the use of the metal-modified polyethylene-based functional carbon material described in the above solution as an adsorption material.

[0019] The present invention provides a method for preparing a metal-modified polyethylene-based functional carbon material. The method pre-treats polyethylene through a hydrothermal process to form an aqueous phase, a gas phase, and a solid phase. During the hydrothermal process, some small molecular acids are generated, which reduce the content of alkanes, olefins, and long-chain hydrocarbons, thereby reducing the oil yield of polyethylene during the pyrolysis process, increasing the solid carbon yield of polyethylene, and lowering the carbonization temperature of polyethylene, thereby achieving a high carbon yield at a relatively low carbonization temperature. This overcomes the problems of harsh carbonization conditions and low carbonization rate of polyethylene at low temperatures. The method introduces a metal during the carbonization process, thereby not only increasing the solid carbon yield but also improving the adsorption performance of the metal-modified polyethylene-based functional carbon material for harmful substances such as nitrogen and phosphorus in wastewater. The metal introduced by the method reacts with phosphate to form hydroxyapatite precipitation, which then undergoes ion exchange and coordination complexation to adsorb ammonia nitrogen, resulting in a large adsorption capacity, high adsorption rate, and high harmful substance removal rate. Furthermore, the adsorption and desorption of the metal-modified polyethylene-based functional carbon material are reversible reactions, allowing for recycling and great economic and environmental value. The results of the examples show that the metal-modified polyethylene-based functional carbon material prepared by the present invention can remove 79.3-99.5% of phosphorus and 80.5-85% of nitrogen from wastewater as an adsorbent, and the solid carbon yield is above 60%.

[0020] The present invention also provides a metal-modified polyethylene-based functional carbon material obtained by the preparation method described in the above scheme, including a polyethylene-based functional carbon material and metal ions loaded on the metal-modified polyethylene-based functional carbon material. The hydrothermally pretreated metal-modified polyethylene-based functional carbon material provided by the present invention has a large specific surface area, a porous structure and abundant surface functional groups. The metal ions loaded on the polyethylene-based functional carbon material combine with phosphate ions to form a precipitate, thereby making the metal-modified polyethylene-based functional carbon material have a large adsorption capacity and a high adsorption rate. It can efficiently remove harmful substances such as nitrogen and phosphorus in water bodies, which helps to solve the problem of eutrophication of water bodies. In addition, the metal-modified polyethylene-based functional carbon material provided by the present invention has a low content of alkanes, olefins and long-chain hydrocarbons, and a high solid carbon yield of polyethylene, which overcomes the problems of harsh carbonization conditions and low carbonization rate of polyethylene at low temperatures.

[0021] The present invention also provides the use of the metal-modified polyethylene-based functional carbon material described in the above solution as an adsorption material. The metal-modified polyethylene-based functional carbon material of the present invention can be used as an adsorption material to efficiently remove harmful pollutants in water, and is particularly suitable for removing substances such as phosphorus and nitrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 This is the XPS spectrum of the metal-modified polyethylene-based functional carbon material before and after phosphorus adsorption in Application Example 1 of the present invention;

[0024] Figure 2 This is a scanning electron microscope image of the metal-modified polyethylene-based functional carbon material of Example 1 of the present invention;

[0025] Figure 3 This is a scanning electron microscope image of the metal-modified polyethylene-based functional carbon material of Example 2 of the present invention. DETAILED DESCRIPTION

[0026] The present invention provides a method for preparing a metal-modified polyethylene-based functional carbon material, comprising the following steps:

[0027] (1) crushing the polyethylene raw material and then subjecting it to ball milling and hydrothermal pretreatment to obtain a polyethylene hydrothermal product;

[0028] (2) mixing the polyethylene hydrothermal product and a metal inorganic substance and carbonizing them to obtain a metal-modified polyethylene-based functional carbon material; the carbonization temperature is 400 to 900°C.

[0029] The present invention crushes the polyethylene raw material and then sequentially performs ball milling (referred to as the first ball milling) and hydrothermal pretreatment to obtain a polyethylene hydrothermal product. In the present invention, the polyethylene raw material can be factory-produced polyethylene resin particles or recycled polyethylene solid waste, such as discarded agricultural mulch film and plastic packaging film. Using waste plastic as raw material, the present invention achieves the recycling and reuse of hazardous solid waste, conserves resources, and treats waste with waste, meeting the requirements of sustainable development.

[0030] In the present invention, the target particle size of the crushed particles is preferably 3 to 10 mm, more preferably 4 to 6 mm; and the crushing method is preferably cutting.

[0031] In the present invention, the rotation speed of the first ball mill is preferably 300-1000 r / min, more preferably 400-500 r / min, and further preferably 400 r / min; the ball milling time is preferably 10-60 min, more preferably 20-40 min, and further preferably 30 min; the target particle size of the first ball mill is preferably not greater than 250 microns, more preferably 150-250 microns; the present invention has no special requirements for the equipment of the first ball mill, and a ball mill familiar to those skilled in the art can be used.

[0032] In the present invention, the temperature of the hydrothermal pretreatment is preferably 150 to 220°C, more preferably 160 to 180°C, and further preferably 180°C. The holding time is preferably 12 to 36 hours, more preferably 24 to 36 hours, and further preferably 24 hours. The amount of water added for the hydrothermal pretreatment is preferably 5 to 9 mL / g (the volume of water added per gram of polyethylene), and more preferably 6 to 7 mL / g. Through hydrothermal pretreatment, the present invention improves the carbonization degree of the polyethylene carbonized material, the content of oxygen-containing functional groups, and the specific surface area of ​​the final carbon material, thereby obtaining more active sites.

[0033] After obtaining a polyethylene hydrothermal product, the present invention mixes the polyethylene hydrothermal product with a metal inorganic substance and carbonizes the mixture to obtain a metal-modified polyethylene-based functional carbon material. In the present invention, the metal inorganic substance preferably includes one or more of a calcium inorganic substance, a magnesium inorganic substance, and a rhenium inorganic substance; the calcium inorganic substance preferably includes one or more of calcium hydroxide, calcium oxide, calcium chloride, and calcium carbonate; the magnesium inorganic substance preferably includes one or more of magnesium acetate tetrahydrate, magnesium oxide, and magnesium chloride; and the rhenium inorganic substance preferably includes one or more of rhenium pentachloride, rhenium heptoxide, ammonium rhenate, and potassium rhenate.

[0034] In the present invention, the mass ratio of the polyethylene hydrothermal product to the metal inorganic substance is preferably 1:2-6, more preferably 1:2-4, and further preferably 1:4.

[0035] In the present invention, the method for mixing the polyethylene hydrothermal product and the metal inorganic material is preferably ball milling (denoted as the second ball milling); the rate of the second ball milling is preferably 300-1000r / min, more preferably 400-500r / min, and further preferably 400r / min; the ball milling time is preferably 10-30min, more preferably 10-20min, and further preferably 10min.

[0036] In the present invention, the carbonization temperature is 400-900°C, preferably 600-800°C, more preferably 700°C, and the holding time is preferably 0.5-4h, more preferably 1-3h, and further preferably 2h; the carbonization is preferably staged carbonization; the carbonization preferably includes a first heating, a first insulation, a second heating and a second insulation; the heating rate of the first heating is preferably 5-10°C / min, more preferably 5-8°C / min, and further preferably 5°C / min; the temperature of the first insulation is preferably 300-500°C, more preferably 400°C, and the holding time is preferably 0.5-1h, more preferably 0.5h; the heating rate of the second heating is preferably consistent with the heating rate of the first heating; the temperature of the second insulation is preferably 400-900°C, more preferably 500-800°C, more preferably 600-700°C, and the holding time is preferably 1-4h, more preferably 1-3h, and further preferably 1.5-2h. The present invention uses segmented carbonization to uniformly heat the raw materials in the first heat preservation stage, and carbonizes the raw materials in the second heat preservation stage, converting the metal inorganic matter part into oxides.

[0037] In the present invention, the carbonization step preferably includes washing the obtained carbonized product; the washing detergent is preferably water; the water is preferably ultrapure water; the amount of the detergent is preferably 10 to 50 ml, more preferably 20 to 30 ml; the number of washing times is preferably 2 to 3 times, more preferably 3 times.

[0038] In the present invention, the washing preferably includes the following steps: mixing the carbonized product with ultrapure water, followed by stirring and solid-liquid separation; the stirring time is preferably 5 to 10 minutes, more preferably 7 minutes; the stirring rate is preferably 200 to 300 rpm, more preferably 240 rpm; the stirring method is preferably magnetic stirring; the solid-liquid separation method is preferably centrifugation; the centrifugation speed is preferably 10,000 rpm, and the centrifugation time is preferably 2 minutes. The present invention avoids errors caused by water washing during subsequent adsorption-desorption cycle experiments through washing.

[0039] In the present invention, the product is preferably dried after washing; the drying temperature is preferably 55-80°C, more preferably 60°C, and the holding time is preferably 10-24 hours, more preferably 24 hours. The present invention has no special requirements for the drying equipment, and a common air drying oven in the art can be used.

[0040] The present invention also provides a metal-modified polyethylene-based functional carbon material obtained by the preparation method described in the above scheme, comprising a polyethylene-based functional carbon material and metal ions loaded on the metal-modified polyethylene-based functional carbon material.

[0041] In the present invention, the mass ratio of the polyethylene functional carbon material to the metal ion is preferably 1:0.3 to 0.6, more preferably 1:0.4 to 0.5. The metal-modified polyethylene functional carbon material of the present invention is rich in metal ions and functional groups, and the functional groups include oxygen-containing functional groups, such as hydroxyl functional groups, which are hydrophilic functional groups, which are conducive to the dispersion of the adsorbent in the solution and have a good fixed adsorption effect on nitrogen and phosphorus; the specific surface area of ​​the metal-modified polyethylene functional carbon material of the present invention is 19.60 to 21.72 m 2 / g, the pore size is 26.40~31.83nm, the adsorption capacity is large and the solid carbon yield is high, the adsorption rate is high, and it can effectively remove harmful substances such as nitrogen and phosphorus in water.

[0042] The present invention also provides the use of the metal-modified polyethylene-based functional carbon material described in the above solution as an adsorption material.

[0043] In the present invention, the application of the metal-modified polyethylene-based functional carbon material as an adsorption material preferably comprises the following steps:

[0044] The metal-modified polyethylene-based functional carbon material is mixed with the wastewater to be treated for adsorption treatment.

[0045] In the present invention, the wastewater to be treated is preferably phosphorus-containing wastewater; the phosphorus content of the wastewater to be treated is preferably 50-150 mg / L, more preferably 100 mg / L; the mass ratio of the phosphorus-containing substance in the wastewater to be treated to the metal-modified polyethylene-based functional carbon material is preferably 1:5-15, more preferably 1:8-13, and further preferably 1:10-11.

[0046] In the present invention, the metal-modified polyethylene-based functional carbon material and the wastewater to be treated are preferably mixed by oscillation; the temperature for the adsorption treatment is preferably room temperature; and the room temperature is preferably 25°C.

[0047] In order to further illustrate the present invention, the scheme of the present invention is described in detail below with reference to the accompanying drawings and embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0048] Example 1

[0049] 10 g of polyethylene powder (commercially available polyethylene resin particles) crushed to a particle size of 3 to 10 mm was placed in a ball mill and ball milled at 400 rpm for 30 min. 6 g of the ball-milled polyethylene powder was mixed with 40 ml of distilled water and transferred to a reactor for hydrothermal carbonization at 180°C for 24 h. The product was then dried and dehydrated to obtain a polyethylene hydrothermal product.

[0050] The obtained polyethylene hydrothermal product is mixed with calcium hydroxide in a mass ratio of 1:4 by ball milling; the ball milled product is placed in a porcelain boat and placed in a tubular furnace. Under a N2 atmosphere, the temperature is first increased to 400°C at a heating rate of 5°C / min and kept warm for 0.5h to ensure that the raw materials are heated evenly, and then the temperature is increased to 500°C and kept warm for 2h. The mixture is naturally cooled to room temperature. The carbonized product is mixed with ultrapure water, stirred and centrifuged in sequence to obtain a metal-modified polyethylene-based functional carbon material.

[0051] Example 2

[0052] 10 g of polyethylene powder (commercially available polyethylene resin particles) crushed to a particle size of 3 to 10 mm was placed in a ball mill and ball milled at 400 rpm for 30 min. 6 g of the ball-milled polyethylene powder was mixed with 40 ml of distilled water and transferred to a reactor for hydrothermal carbonization at 180°C for 24 h. The product was then dried and dehydrated to obtain a polyethylene hydrothermal product.

[0053] The obtained polyethylene hydrothermal product is mixed with calcium hydroxide in a mass ratio of 1:4 by ball milling; the ball milled product is placed in a porcelain boat and placed in a tubular furnace. Under a N2 atmosphere, the temperature is first increased to 400°C at a heating rate of 5°C / min and kept warm for 0.5h to ensure that the raw materials are heated evenly, and then the temperature is increased to 800°C and kept warm for 2h. The mixture is naturally cooled to room temperature. The carbonized product is mixed with ultrapure water and then stirred and centrifuged in sequence to obtain a metal-modified polyethylene-based functional carbon material.

[0054] Example 3

[0055] 10 g of polyethylene powder (recycled polyethylene solid waste) crushed to a particle size of 3 to 10 mm was placed in a ball mill and ball milled at 400 r / min for 30 min. 6 g of the ball-milled polyethylene powder was mixed with 40 ml of distilled water and transferred to a reactor for hydrothermal carbonization at 150°C for 36 h. The product was dried and dehydrated to obtain a polyethylene hydrothermal product.

[0056] The obtained polyethylene hydrothermal product is ball-milled with calcium carbonate in a mass ratio of 1:2; the ball-milled product is placed in a porcelain boat and placed in a tubular furnace. Under a N2 atmosphere, the temperature is first increased to 300°C at a heating rate of 5°C / min and kept warm for 0.5h to ensure that the raw materials are heated evenly, and then the temperature is increased to 400°C and kept warm for 2h. The mixture is naturally cooled to room temperature, and the carbonized product is mixed with ultrapure water, stirred and centrifuged in sequence to obtain a metal-modified polyethylene-based functional carbon material.

[0057] Example 4

[0058] 10 g of polyethylene powder (commercially available polyethylene resin particles) crushed to a particle size of 3 to 10 mm was placed in a ball mill and ball milled at 400 rpm for 30 min. 6 g of the ball-milled polyethylene powder was mixed with 40 ml of distilled water and transferred to a reactor for hydrothermal carbonization at 220°C for 12 h. The product was then dried and dehydrated to obtain a polyethylene hydrothermal product.

[0059] The obtained polyethylene hydrothermal product is mixed with magnesium acetate tetrahydrate by ball milling in a mass ratio of 1:6; the ball milled product is placed in a porcelain boat and placed in a tubular furnace. Under a N2 atmosphere, the temperature is first increased to 500°C at a heating rate of 5°C / min and kept warm for 0.5h to ensure that the raw materials are heated evenly, and then the temperature is increased to 900°C and kept warm for 2h. The mixture is naturally cooled to room temperature. The carbonized product is mixed with ultrapure water and then stirred and centrifuged in sequence to obtain a metal-modified polyethylene-based functional carbon material.

[0060] Example 5

[0061] 10 g of polyethylene powder (commercially available polyethylene resin particles) crushed to a particle size of 3 to 10 mm was placed in a ball mill and ball milled at 400 rpm for 30 min. 6 g of the ball-milled polyethylene powder was mixed with 40 ml of distilled water and transferred to a reactor for hydrothermal carbonization at 180°C for 24 h. The product was then dried and dehydrated to obtain a polyethylene hydrothermal product.

[0062] The obtained polyethylene hydrothermal product is mixed with magnesium chloride in a mass ratio of 1:4 by ball milling; the ball milled product is placed in a porcelain boat and placed in a tubular furnace. Under a N2 atmosphere, the temperature is first increased to 300°C at a heating rate of 5°C / min and kept warm for 0.5h to ensure that the raw materials are heated evenly, and then the temperature is increased to 500°C and kept warm for 2h. The mixture is naturally cooled to room temperature. The carbonized product is mixed with ultrapure water, stirred and centrifuged in sequence to obtain a metal-modified polyethylene-based functional carbon material.

[0063] Example 6

[0064] 10 g of polyethylene powder (recycled polyethylene solid waste) crushed to a particle size of 3 to 10 mm was placed in a ball mill and ball milled at 400 r / min for 30 min. 6 g of the ball-milled polyethylene powder was mixed with 40 ml of distilled water and transferred to a reactor for hydrothermal carbonization at 180°C for 24 h. The product was dried and dehydrated to obtain a polyethylene hydrothermal product.

[0065] The obtained polyethylene hydrothermal product is mixed with rhenium pentachloride in a mass ratio of 1:4 by ball milling; the ball milled product is placed in a porcelain boat and placed in a tubular furnace. Under a N2 atmosphere, the temperature is first increased to 500°C at a heating rate of 5°C / min and kept warm for 0.5h to ensure that the raw materials are heated evenly, and then the temperature is increased to 800°C and kept warm for 2h. The mixture is naturally cooled to room temperature. The carbonized product is mixed with ultrapure water, stirred and centrifuged in sequence to obtain a metal-modified polyethylene-based functional carbon material.

[0066] Example 7

[0067] 10 g of polyethylene powder (recycled polyethylene solid waste) crushed to a particle size of 3 to 10 mm was placed in a ball mill and ball milled at 400 r / min for 30 min. 6 g of the ball-milled polyethylene powder was mixed with 40 ml of distilled water and transferred to a reactor for hydrothermal carbonization at 180°C for 24 h. The product was dried and dehydrated to obtain a polyethylene hydrothermal product.

[0068] The obtained polyethylene hydrothermal product is mixed with calcium oxide in a mass ratio of 1:4 by ball milling; the ball milled product is placed in a porcelain boat and placed in a tubular furnace. Under a N2 atmosphere, the temperature is first increased to 500°C at a heating rate of 5°C / min and kept warm for 0.5h to ensure that the raw materials are heated evenly, and then the temperature is increased to 800°C and kept warm for 2h. The mixture is naturally cooled to room temperature. The carbonized product is mixed with ultrapure water and then stirred and centrifuged in sequence to obtain a metal-modified polyethylene-based functional carbon material.

[0069] Example 8

[0070] 10 g of polyethylene powder (recycled polyethylene solid waste) crushed to a particle size of 3 to 10 mm was placed in a ball mill and ball milled at 400 r / min for 30 min. 6 g of the ball-milled polyethylene powder was mixed with 40 ml of distilled water and transferred to a reactor for hydrothermal carbonization at 180°C for 24 h. The product was dried and dehydrated to obtain a polyethylene hydrothermal product.

[0071] The obtained polyethylene hydrothermal product is mixed with magnesium oxide in a mass ratio of 1:4 by ball milling; the ball milled product is placed in a porcelain boat and placed in a tubular furnace. Under a N2 atmosphere, the temperature is first increased to 500°C at a heating rate of 5°C / min and kept warm for 0.5h to ensure that the raw materials are heated evenly, and then the temperature is increased to 800°C and kept warm for 2h. The mixture is naturally cooled to room temperature. The carbonized product is mixed with ultrapure water and then stirred and centrifuged in sequence to obtain a metal-modified polyethylene-based functional carbon material.

[0072] Example 9

[0073] 10 g of polyethylene powder (recycled polyethylene solid waste) crushed to a particle size of 3 to 10 mm was placed in a ball mill and ball milled at 400 r / min for 30 min. 6 g of the ball-milled polyethylene powder was mixed with 40 ml of distilled water and transferred to a reactor for hydrothermal carbonization at 180°C for 24 h. The product was dried and dehydrated to obtain a polyethylene hydrothermal product.

[0074] The obtained polyethylene hydrothermal product is ball-milled with rhenium heptoxide in a mass ratio of 1:4; the ball-milled product is placed in a porcelain boat and placed in a tubular furnace. Under a N2 atmosphere, the temperature is first increased to 500°C at a heating rate of 5°C / min and kept warm for 0.5h to ensure that the raw materials are heated evenly, and then the temperature is increased to 800°C and kept warm for 2h. The mixture is naturally cooled to room temperature. The carbonized product is mixed with ultrapure water, stirred and centrifuged in sequence to obtain a metal-modified polyethylene-based functional carbon material.

[0075] Example 10

[0076] 10 g of polyethylene powder (recycled polyethylene solid waste) crushed to a particle size of 3 to 10 mm was placed in a ball mill and ball milled at 400 r / min for 30 min. 6 g of the ball-milled polyethylene powder was mixed with 40 ml of distilled water and transferred to a reactor for hydrothermal carbonization at 180°C for 24 h. The product was dried and dehydrated to obtain a polyethylene hydrothermal product.

[0077] The obtained polyethylene hydrothermal product is ball-milled with ammonium rhenate in a mass ratio of 1:4; the ball-milled product is placed in a porcelain boat and placed in a tubular furnace. Under a N2 atmosphere, the temperature is first increased to 500°C at a heating rate of 5°C / min and kept warm for 0.5h to ensure that the raw materials are heated evenly, and then the temperature is increased to 800°C and kept warm for 2h. The mixture is naturally cooled to room temperature. The carbonized product is mixed with ultrapure water, stirred and centrifuged in sequence to obtain a metal-modified polyethylene-based functional carbon material.

[0078] Comparative Example 1

[0079] Take 10g of polyethylene powder (commercially available polyethylene resin particles) crushed to a particle size of 3-10mm, place it in a ball mill, and ball mill it at a speed of 400r / min for 30min; take 6g of the ball-milled polyethylene powder and mix it with calcium hydroxide at a mass ratio of 1:4; put the product obtained by ball milling into a porcelain boat and place it in a tubular furnace. Under a N2 atmosphere, heat it to 400℃ at a heating rate of 5℃ / min and keep it warm for 0.5h to ensure that the raw materials are heated evenly, then heat it to 500℃, keep it warm for 2h, and naturally cool it to room temperature. The carbonized product is mixed with ultrapure water, stirred and centrifuged in sequence to obtain a metal-modified polyethylene-based functional carbon material.

[0080] Application Example 1

[0081] Preparation of phosphate stock solution: Dry high-grade potassium dihydrogen phosphate at 110°C for 2 h, cool, weigh 0.2197 g, dissolve in water, transfer to a 1000 ml volumetric flask, add 5 ml of sulfuric acid, and dilute to the mark to obtain 50.0 μg of phosphorus per ml to obtain a phosphate stock solution.

[0082] Preparation of phosphate standard solution: Take 10.00 ml of phosphate stock solution in a 250 ml volumetric flask and dilute to the mark to contain 2.00 μg phosphorus per ml;

[0083] The phosphate stock solution was diluted a corresponding multiple to prepare a phosphate solution with an initial concentration of 100 mg / L. Then, 0.05 g of the metal-modified polyethylene-based functional carbon material of Example 1 was added to the 100 mg / L phosphate solution. The pH of the solution was controlled to 5.35 and oscillated for 1 hour until adsorption equilibrium was reached. The solution in the polyethylene tube was removed and filtered through a 0.45-micron filter membrane. The residual phosphorus concentration in the filtrate was determined by atomic absorption spectrophotometry. The calculated phosphate adsorption capacity was 224.2 mg / L, the phosphorus removal rate was 94.3%, and the solid carbon yield was relatively high, at 68.3%.

[0084] Application Example 2

[0085] Preparation of phosphate stock solution: Dry high-grade potassium dihydrogen phosphate at 110°C for 2 h, cool, weigh 0.2197 g, dissolve in water, transfer to a 1000 ml volumetric flask, add 5 ml of sulfuric acid, and dilute to the mark to obtain 50.0 μg of phosphorus per ml to obtain a phosphate stock solution.

[0086] Preparation of phosphate standard solution: Take 10.00 ml of phosphate stock solution in a 250 ml volumetric flask and dilute to the mark to contain 2.00 μg phosphorus per ml;

[0087] The phosphate stock solution was diluted a corresponding multiple to prepare a phosphate solution with an initial concentration of 100 mg / L. Then, 0.05 g of the metal-modified polyethylene-based functional carbon material of Example 2 was added to the 100 mg / L phosphate solution. The pH of the solution was controlled to 5.35 and oscillated for 1 hour until adsorption equilibrium was reached. The solution in the polyethylene tube was removed and filtered through a 0.45-micron filter membrane. The residual phosphorus concentration in the filtrate was determined by atomic absorption spectrophotometry. The calculated phosphate adsorption capacity was 236.1 mg / L, the phosphorus removal rate was 98.8%, and the solid carbon yield was 61.5%.

[0088] Application Example 3

[0089] Preparation of nitrate nitrogen stock solution: Dry high-grade potassium nitrate at 100°C for 2 h, cool, weigh 0.7218 g, dissolve in water, transfer to a 1000 mL volumetric flask, add 2 mL of chloroform as a preservative, and dilute to the mark to 100 μg per mL to obtain a nitrate stock solution.

[0090] Preparation of nitrate standard solution: The initial concentration of nitrate stock solution is 100 mg / L;

[0091] 0.05 g of the metal-modified polyethylene-based functional carbon material of Example 1 was added to a 100 mg / L nitrate solution and shaken for 12 h until adsorption equilibrium was reached. The solution in the polyethylene tube was removed and filtered through a 0.45 μm filter membrane. The residual nitrate nitrogen concentration in the filtrate was determined by atomic absorption spectrophotometry. The calculated nitrate adsorption capacity was 200.7 mg / L, the nitrogen removal rate was 80.5%, and the solid carbon yield was 68.3%.

[0092] Comparative Application Example 1

[0093] Preparation of phosphate stock solution: Dry high-grade potassium dihydrogen phosphate at 110°C for 2 h, cool, weigh 0.2197 g, dissolve in water, transfer to a 1000 ml volumetric flask, add 5 ml of sulfuric acid, and dilute to the mark to obtain 50.0 μg of phosphorus per ml to obtain a phosphate stock solution.

[0094] Preparation of phosphate standard solution: Take 10.00 ml of phosphate stock solution in a 250 ml volumetric flask and dilute to the mark to contain 2.0 μg phosphorus per ml;

[0095] The phosphate stock solution was diluted by a corresponding multiple to prepare a phosphate solution with an initial concentration of 100 mg / L. Then, 0.05 g of the metal-modified polyethylene-based functional carbon material of Comparative Example 1 was added to the 100 mg / L phosphate solution, the pH of the solution was controlled to 5.35, and the mixture was oscillated for 1 hour until adsorption equilibrium was reached. The solution in the polyethylene tube was removed and filtered through a 0.45-micron filter membrane. The residual phosphorus concentration in the filtrate was determined by atomic absorption spectrophotometry. The calculated phosphate adsorption capacity was 232.3 mg / L, the phosphorus removal rate was 97.9%, and the solid carbon yield was 47.7%.

[0096] XPS spectrum test was conducted on the metal modified polyethylene functional carbon material of Application Example 1 of the present invention before and after phosphorus adsorption. The results are as follows: Figure 1 As shown. Figure 1 It can be seen that the XPS spectrum of the metal-modified polyethylene-based functional carbon material in Example 1 of the present invention has a peak at 135 eV belonging to P 2p The new peak shows that the metal-modified polyethylene-based functional carbon material of the present invention successfully adsorbs phosphate.

[0097] The metal modified polyethylene functional carbon materials of Examples 1 and 2 of the present invention were tested using a scanning electron microscope. The results are as follows: Figure 2 and Figure 3 As shown. Figure 2 and Figure 3 It can be seen that the components of the metal-modified polyethylene-based functional carbon material prepared by the present invention are evenly distributed and have no obvious structural defects.

[0098] The performance test results of Examples 3 to 10 are similar to those of Examples 1 to 2.

[0099] It can be seen from the above embodiments that the hydrothermal pretreatment of metal-modified polyethylene-based functional carbon material provided by the present invention has a large adsorption capacity and a high solid carbon yield, greatly improving the solid carbon yield without a significant loss of adsorption capacity, with a high adsorption rate and good economic benefits. It can efficiently remove harmful substances such as phosphorus in water bodies, and helps solve the problem of eutrophication of water bodies.

[0100] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a metal-modified polyethylene-based functional carbon material, comprising the following steps: (1) crushing the polyethylene raw material and then subjecting it to ball milling and hydrothermal pretreatment to obtain a polyethylene hydrothermal product; (2) mixing the polyethylene hydrothermal product and a metal inorganic substance and carbonizing them to obtain a metal-modified polyethylene-based functional carbon material; the carbonization temperature is 400 to 900° C.; The metal inorganic substance includes one or more of a calcium inorganic substance, a magnesium inorganic substance and a rhenium inorganic substance; The mass ratio of the polyethylene hydrothermal product to the metal inorganic substance is 1:2 to 6; The temperature of the hydrothermal pretreatment is 150-180°C, and the holding time is 12-36 hours; The amount of water added for the hydrothermal pretreatment is 5 to 9 mL / g; The target particle size of the ball milling is no greater than 250 microns; After the carbonization, the obtained carbonized product is washed 2 to 3 times.

2. The preparation method according to claim 1, characterized in that The carbonization heat preservation time is 0.5 to 4 hours.

3. The metal-modified polyethylene-based functional carbon material obtained by the preparation method according to any one of claims 1 to 2 comprises a polyethylene-based functional carbon material and metal ions loaded on the metal-modified polyethylene-based functional carbon material.

4. Use of the metal-modified polyethylene-based functional carbon material according to claim 3 as an adsorption material.

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