Preparation of derived porous carbon based on polystyrene foam, preparation method and application

Abstract

The application provides a polystyrene foam material-based derived porous carbon, a preparation method and application, and belongs to the technical field of waste polystyrene foam material treatment, and the polystyrene foam material-based derived porous carbon preparation method comprises the following steps: pretreating polystyrene foam material below a pyrolysis temperature of the polystyrene foam material to obtain polystyrene foam powder; uniformly mixing the polystyrene foam powder with a metal salt, and then placing the mixture in an anaerobic environment to perform first pyrolysis treatment, so as to obtain primary derived porous carbon of metal-doped polystyrene foam, wherein the first pyrolysis treatment temperature is lower than the decomposition temperature of the metal salt.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of waste polystyrene foam material processing, in particular to a method for preparing derived porous carbon based on polystyrene foam material, a preparation method and application, and more particularly to a method for preparing polystyrene foam derived porous carbon by anaerobic pyrolysis of waste extruded / polystyrene foam board, and a method for removing new pollutants organic phosphates by using polystyrene foam derived porous carbon in water environment. BACKGROUND

[0002] Since the large-scale production of plastic products, due to its light and heat insulation, impact resistance, can be used for preservation and sound insulation, and the manufacturing cost is relatively low, it has been widely used in packaging, construction, transportation and other industries. At present, the global annual plastic waste has penetrated into most parts of the earth.

[0003] Polystyrene foam materials are divided into two types, molded polystyrene foam (EPS) and extruded polystyrene foam (XPS), according to the production process. EPS and XPS are mainly made of polystyrene as raw material, with low thermal conductivity and low water absorption, and can be used in building exterior walls, airport runways, highways, etc. and play a role in heat preservation and moisture prevention. However, even if the foam material has excellent performance, its service life is about 25 years. The waste foam material has a tight closed-cell structure, so it has small density and large volume, is not easy to compress, and has high transportation and recycling cost. At present, the disposal method of waste plastic products is mainly incineration and landfill on site, among which direct incineration will produce more toxic and harmful gases and will produce a large amount of CO2, which goes against the concept of global carbon neutralization; direct landfill will occupy a large amount of land area and cause the release of microplastics, and the natural degradation time and the harm to the environment cannot be estimated.

[0004] The current technologies applicable to the reduction, harmless and resource of polystyrene foam include hydrothermal carbonization, catalytic pyrolysis, air / oxygen pyrolysis and anaerobic pyrolysis. The hydrothermal carbonization technology can effectively obtain solid products, but the gas generated in the carbonization process cannot be discharged from the reaction kettle, and the hydrothermal carbonization technology is currently only in theoretical research, and there is no example of large-scale environmental application; the catalytic pyrolysis hydrogenation technology can effectively depolymerize the foam material, but often produces a solid-liquid mixture that is difficult to separate, reducing the availability of the product; the air / oxygen pyrolysis produces a large amount of CO2; the anaerobic pyrolysis technology is a safe and effective technology for treating solid waste in recent years, and does not have the technical problems of the above-mentioned hydrothermal carbonization, catalytic pyrolysis, air / oxygen pyrolysis, and has been widely used in the resource of environmental solid waste (biomass, sludge, kitchen garbage, etc.). Through the anaerobic pyrolysis technology, solid, liquid and gas products can be effectively obtained, which is suitable for application in the research and preparation of solid carbon materials from waste polystyrene foam. However, the anaerobic pyrolysis technology applied in the process of polystyrene foam is easy to produce volatile monomers, resulting in low yield of derived carbon and reducing the recyclable products of polystyrene foam. Therefore, how to improve the yield of derived carbon is an urgent problem to be solved. SUMMARY

[0005] In view of the above technical problems, the present application provides a method for preparing derived porous carbon based on polystyrene foam, a preparation method and application, in order to at least partially solve the above technical problems, and thus the specific technical solutions provided by the present application are as follows.

[0006] As a first aspect of the present application, the present application provides a method for preparing derived porous carbon based on polystyrene foam, comprising: pretreating the polystyrene foam below the pyrolysis temperature of the polystyrene foam to obtain polystyrene foam powder; mixing the polystyrene foam powder with a metal salt uniformly and then placing it in an anaerobic environment for first pyrolysis treatment to obtain primary derived porous carbon of metal-doped polystyrene foam, wherein the first pyrolysis treatment temperature is lower than the decomposition temperature of the metal salt.

[0007] According to the embodiments of the present application, the above method for preparing derived porous carbon based on polystyrene foam further comprises:

[0008] The primary derived porous carbon of metal-doped polystyrene foam is placed in an anaerobic environment for second pyrolysis treatment to obtain derived porous carbon of metal-doped polystyrene foam, wherein the second pyrolysis treatment temperature is higher than the decomposition temperature of the metal salt.

[0009] As a second aspect of the present application, the present application provides a derived porous carbon prepared by the method for preparing a derived porous carbon based on polystyrene foam material, wherein the derived porous carbon comprises: a porous carbon skeleton and a metal and / or metal oxide anchored on the porous carbon skeleton.

[0010] As a third aspect of the present application, the present application provides a method for removing organophosphate ester, comprising: treating sewage containing organophosphate ester by the derived porous carbon.

[0011] Based on the above technical solution, the present application provides a method for preparing a derived porous carbon based on polystyrene foam material, a preparation method and an application, which at least has one of the following beneficial effects:

[0012] (1) In the embodiment of the present application, since the waste polystyrene foam material has a large initial void and a large hardness, it cannot be directly mixed with metal salt to prepare porous carbon. To this end, the present application proposes to pretreat the polystyrene foam material below the pyrolysis temperature of the polystyrene foam material to change the pore structure of the polystyrene, convert it into a closely arranged structure and destroy the stability of the long chain structure of the polystyrene, so as to obtain polystyrene foam powder for subsequent mixing with metal salt. During the pretreatment process, the polystyrene foam material mainly deforms without loss of monomers, so that the quality of the obtained polystyrene foam powder is almost the same as that of the polystyrene foam material. Subsequently, the obtained polystyrene foam powder is uniformly mixed with metal salt and placed in an anaerobic environment, and the first pyrolysis treatment temperature is controlled below the decomposition temperature of the metal salt for first pyrolysis treatment. Through the first pyrolysis treatment, the polystyrene foam powder can be melted (not carbonized), and the melted polystyrene foam is further mixed with the metal salt, and under the catalysis of metal ions, the melted polystyrene foam powder is crosslinked to form a large skeleton carbon structure, and at the same time, the metal ions are anchored in the large skeleton carbon structure to form a primary derived porous carbon of metal-doped polystyrene foam, so as to utilize the metal ions to reduce the loss of monomers in polystyrene and improve the yield of derived carbon.

[0013] (2) In the embodiment of the present application, the primary derived porous carbon of metal-doped polystyrene foam is placed in an anaerobic environment, and the second pyrolysis treatment temperature is controlled above the decomposition temperature of the metal salt for second pyrolysis treatment, which can remove the anions in the metal salt loaded on the large skeleton carbon structure, improve the stable crosslinking degree of the metal and the carbon skeleton, and finally obtain the derived porous carbon of metal-doped polystyrene foam.

[0014] (3) In the embodiment of the present application, the polystyrene foam is pretreated below the pyrolysis temperature of the polystyrene foam to saturate the surface of the polystyrene foam powder and maintain a high metal coverage on the surface of the polystyrene foam powder through a selective anchoring mechanism, thereby maximizing the probability of metal binding to all available coordination sites of polystyrene, stably obtaining a higher metal content, better cross-linking between the metal and the polystyrene foam, and increasing the retention rate of the polystyrene foam powder.

[0015] (4) In the embodiment of the present application, the prepared derived porous carbon is used to treat wastewater containing organophosphate esters, and the adsorption of organophosphate esters is realized by using the physical adsorption performance of the derived porous carbon and the chemical adsorption performance of the metal ions on the surface of the porous carbon to the organophosphate esters. Compared with the advanced oxidation technology, the treatment process is simple, is not affected by environmental factors, is environmentally friendly, economical, safe, and can be applied on a large scale in water treatment processes. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 A flowchart for preparing the derived porous carbon based on the polystyrene foam in an embodiment of the present application is shown in the figure.

[0017] Figure 2 A schematic diagram of the anaerobic pyrolysis characteristics of the polystyrene foam in Table 1 is shown in the figure.

[0018] Figure 3 A flowchart for preparing the iron-doped polystyrene foam-derived porous carbon in Embodiment 1 of the present application is shown in the figure.

[0019] Figure 4 A graph showing the adsorption performance test results of different polystyrene foam-derived porous carbons on halogen-containing organophosphate esters, taking tris(2-chloroethyl) phosphate (TCEP) as an example at different concentrations is shown in the figure.

[0020] Figure 5 A graph showing the adsorption capacity test results of different content of iron-doped polystyrene foam-derived porous carbons on alkyl-containing organophosphate esters, taking tripropyl phosphate (TPrP) as an example in Application Example 2 is shown in the figure.

[0021] Figure 6 A graph showing the removal rate test results of different content of iron-doped polystyrene foam-derived porous carbons on alkyl-containing organophosphate esters, taking tripropyl phosphate (TPrP) as an example in Application Example 2 is shown in the figure.

[0022] Figure 7 A graph showing the adsorption capacity test results of different content of iron-doped polystyrene foam-derived porous carbons on chloro-containing organophosphate esters TCEP in Application Example 2 is shown in the figure.

[0023] Figure 8The test result graph of the removal rate of the organic phosphoric acid ester TCEP containing chlorine groups by the derived porous carbon of the iron-doped polystyrene foam with different contents in application example 2

[0024] Figure 9 The test result graph of the adsorption capacity of the organic phosphoric acid ester TPhP containing benzene rings by the derived porous carbon of the iron-doped polystyrene foam with different contents in application example 2

[0025] Figure 10 The test result graph of the removal rate of the organic phosphoric acid ester TPhP containing benzene rings by the derived porous carbon of the iron-doped polystyrene foam with different contents in application example 2

[0026] Figure 11 The test result graph of the adsorption capacity of the organic phosphoric acid ester TCEP containing chlorine groups by the derived porous carbon of the polystyrene foam doped with different metals

[0027] Figure 12 The test result graph of the removal rate of the organic phosphoric acid ester TCEP containing chlorine groups by the derived porous carbon of the polystyrene foam doped with different metals

[0028] Figure 13 The test result graph of the removal rate of the organic phosphoric acid ester TCEP containing chlorine groups by the derived porous carbon of the polystyrene foam doped with different metals in different water bodies. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with specific embodiments and with reference to the drawings.

[0030] In view of the problem that volatile organic monomers are easily produced in the process of applying the anaerobic pyrolysis technology to the preparation of derived porous carbon from polystyrene foam materials, resulting in a low yield of derived carbon, the present application provides a method for preparing derived porous carbon based on polystyrene foam materials, so as to prepare derived porous carbon based on polystyrene foam materials. Specifically, by introducing metal salts into polystyrene foam materials, the metal-doped assisted polystyrene foam cross-linking carbonization technology is used in the anaerobic pyrolysis process to separate solid products from waste polystyrene foam materials, increase the yield of polystyrene derived carbon, and apply the porous derived carbon prepared based on polystyrene to the removal of organic phosphoric acid esters, effectively remove the new pollutant organic phosphoric acid esters in water bodies, and realize the value utilization of waste polystyrene.

[0031] Specifically, as a first aspect of the present application, the present application provides a method for preparing derived porous carbon based on polystyrene foam material, comprising: pretreating the polystyrene foam material below the pyrolysis temperature of the polystyrene foam material to obtain polystyrene foam powder; uniformly mixing the polystyrene foam powder with a metal salt and then placing it in an anaerobic environment for first pyrolysis treatment to obtain primary derived porous carbon of metal-doped polystyrene foam, wherein the first pyrolysis treatment temperature is lower than the decomposition temperature of the metal salt.

[0032] In the embodiment of the present application, the pretreatment of the polystyrene foam material below the pyrolysis temperature of the polystyrene foam material changes the pore structure of the polystyrene, converts it into a closely arranged structure, and destroys the stability of the long-chain structure of the polystyrene, thereby obtaining the polystyrene foam powder for subsequent mixing with the metal salt. In the pretreatment process, the polystyrene is mainly deformed without loss of monomers, so the quality of the obtained polystyrene foam powder is similar to that of the polystyrene foam material. Subsequently, the obtained polystyrene foam powder is uniformly mixed with the metal salt and then placed in an anaerobic environment, and the first pyrolysis treatment temperature is controlled below the decomposition temperature of the metal salt for first pyrolysis treatment. In the first pyrolysis treatment process, the polystyrene foam powder can be melted, and the melted polystyrene foam can be further uniformly mixed with the metal salt. The catalytic effect of metal ions is used to cross-link the melted polystyrene foam powder to form a large-skeleton carbon structure, and at the same time, the metal ions are anchored in the large-skeleton carbon structure to form primary derived porous carbon of metal-doped polystyrene foam. In this way, the use of metal ions reduces the loss of monomers in polystyrene and improves the yield of derived carbon.

[0033] According to the embodiment of the present application, the pretreatment comprises: placing the polystyrene foam material in a reactor, heating to 150-300℃ at a heating rate of 2-10℃ / min in an anaerobic environment, and performing heat treatment for 1-3h to obtain polystyrene foam powder. The heating rate can be 2℃ / min, 5℃ / min or 10℃ / min; the pyrolysis temperature during the pretreatment process can be 150℃, 200℃, 250℃ or 300℃; the time for pyrolysis treatment can be 1h, 2h or 3h; and the anaerobic gas in the reactor is nitrogen or argon.

[0034] In the embodiments of the present application, it is known from the pyrolysis characteristics of polystyrene foam that, at room temperature to 350℃, polystyrene foam mainly deforms without monomer loss, and the mass of the obtained polystyrene foam powder is close to the mass of the polystyrene foam material, for example, about 2g of polystyrene foam powder is generated from 2g of pretreated waste extruded polystyrene foam. The method of the absolute oxygen heat treatment includes: performing the absolute oxygen heat treatment through a tube furnace, and the specific operation method can be: performing the absolute oxygen heat treatment through nitrogen, vacuumizing once and maintaining for 10-15min, after the negative pressure value of the air inlet pressure gauge is unchanged, then performing the air-vacuum reciprocating extraction for 3 times, after the air extraction for 10-15min, starting to run the tube furnace to perform the heat treatment.

[0035] According to the embodiments of the present application, the metal salt includes any one of iron salt, nickel salt, cobalt salt and lanthanum salt, wherein the metal salt can include any one of metal chloride, metal sulfate and metal nitrate, such as iron chloride, nickel chloride, cobalt chloride, lanthanum chloride, iron sulfate, nickel sulfate, cobalt sulfate, lanthanum sulfate, iron nitrate, nickel nitrate, cobalt nitrate and lanthanum nitrate, etc. The mass ratio of the polystyrene foam powder to the metal ion is 1:0.03-0.25, preferably 1:0.05-0.25%, such as the mass ratio of the polystyrene foam to the iron ion (Fe 3+ ) is 1:0.03, 1:0.1, 1:0.15, 1:0.2 or 1:0.25. The polystyrene foam powder and the metal salt in the ratio range can help the metal salt to be fully crosslinked with the molten polystyrene foam powder in the first pyrolysis treatment process; if the metal salt is too little (such as less than 1:0.03), the polystyrene foam still has volatilization problems in the first pyrolysis treatment process, so that the problem of low polystyrene foam material recycling yield cannot be solved. It should be noted that the organic metal salt is not used because its decomposition temperature is low, that is, the polystyrene foam material has not started to melt, the organic metal salt has already decomposed, and the organic metal salt generally exists in the form of complex, so there is almost no single metal ion. Therefore, the inorganic metal salt is preferably used in the present application.

[0036] According to the embodiments of the present application, after the polystyrene foam powder and the metal salt are uniformly mixed, the mixture is placed in an absolute oxygen environment to perform the first pyrolysis treatment, wherein the heating rate of the first pyrolysis treatment is 2-10℃ / min, such as 2℃ / min, 5℃ / min or 10℃ / min, and the temperature of the first pyrolysis treatment is 300-450℃, such as 300℃, 350℃, 400℃ or 450℃. At the first pyrolysis treatment temperature, the polystyrene foam powder melts and has a melt crosslinking reaction with the metal salt, and at the same time, under the catalysis of the metal ion, the polystyrene monomer is crosslinked to form a large skeleton carbon structure.

[0037] According to an embodiment of the present application, the method for preparing the derived porous carbon based on the polystyrene foam further comprises: placing the primary derived porous carbon of the metal-doped polystyrene foam into an anaerobic environment for a second pyrolysis treatment to obtain the derived porous carbon of the metal-doped polystyrene foam, wherein the temperature of the second pyrolysis treatment is higher than the decomposition temperature of the metal salt.

[0038] In an embodiment of the present application, the primary derived porous carbon of the metal-doped polystyrene foam is placed into an anaerobic environment for a second pyrolysis treatment to remove the anions in the metal salt crosslinked with the carbon skeleton, which is conducive to the stable crosslinking of the metal with the carbon skeleton and the stable metal content.

[0039] According to an embodiment of the present application, the primary derived porous carbon of the metal-doped polystyrene foam is placed into an anaerobic environment for a second pyrolysis treatment, wherein the temperature of the second pyrolysis treatment is 550-1200℃, such as 550℃, 750℃, 1000℃ or 1200℃, for example, when the metal salt is ferric chloride, the first pyrolysis treatment temperature is set to 350-450℃, and the second pyrolysis treatment temperature is set to 550-650℃; when the metal salt is nickel chloride, the first pyrolysis treatment temperature is 350-450℃, and the second pyrolysis treatment temperature is 650-800℃; when the metal salt is cobalt chloride, the first pyrolysis treatment temperature is 350-450℃, and the second pyrolysis treatment temperature is 750-1000℃; when the metal salt is lanthanum chloride, the first pyrolysis temperature is 350-450℃, and the second pyrolysis treatment temperature is 750-1200℃; and the time of the second pyrolysis treatment is 1-3h, such as 1h, 2h or 3h.

[0040] In an embodiment of the present application, the second pyrolysis treatment at a temperature higher than the decomposition temperature of the metal salt can remove the anions adsorbed on the metal salt crosslinked with the carbon skeleton, while stabilizing the metal content, to prepare the derived porous carbon of the metal-doped polystyrene foam with better performance.

[0041] According to an embodiment of the present application, before the second pyrolysis treatment of the primary derived porous carbon of the metal-doped polystyrene foam, it comprises: removing the metal salt not combined with the primary derived porous carbon through a washing process, which comprises ultrasonic treatment of the primary derived porous carbon of the metal-doped polystyrene foam with an alcohol solvent, and cleaning with water. The alcohol reagent includes methanol, ethanol, etc.

[0042] In the embodiment of the present application, the surface of the polystyrene foam has been saturated by the first pyrolysis treatment, and a high load is maintained on the surface of the polystyrene foam by the selective anchoring mechanism of the metal salt, so as to maximize the probability of the combination of the metal and all available coordination sites of the polystyrene foam powder. In the process of mixing the polystyrene foam powder and the metal salt, an excess amount of the metal salt can be added to ensure that the metal salt is fully crosslinked with the molten polystyrene foam powder and the volatilization of monomers is reduced. However, the presence of the excess amount of the metal salt can cause metal agglomeration in the second pyrolysis treatment, thereby affecting the performance of the derived porous carbon. In this regard, the present application proposes to clean the primary derived porous carbon doped with the metal polystyrene foam to wash away the excess amount of the metal salt that is not crosslinked with the polystyrene foam powder, so as to remove the residual ligand (metal salt) by washing, avoid metal sintering and agglomeration in the second pyrolysis treatment, and obtain stable and higher content of the metal.

[0043] Figure 1 For the process diagram of preparing the derived porous carbon based on the polystyrene foam material in the embodiment of the present application, the following steps are included:

[0044] Step 1: The polystyrene foam material is placed in a reactor, and is heated to 150-300℃ at a heating rate of 2-10℃ / min in an anaerobic (inert gas) environment for 1-3h of anaerobic heat pretreatment, so as to obtain the polystyrene foam powder.

[0045] Step 2: The polystyrene foam powder is mixed with the metal salt and is uniformly ground, and the addition amount of the metal salt is X%, which is 3wt%-25wt%.

[0046] Step 3: The mixture in step 2 is placed in a reactor, and is subjected to the first pyrolysis treatment in an anaerobic (inert gas) atmosphere, and the pyrolysis temperature is lower than the decomposition temperature of the metal salt, such as the pyrolysis treatment temperature is 350-450℃, the heating rate is 2-10℃ / min, and the pyrolysis time is 1-3h, and the product obtained in this process is called the primary derived porous carbon doped with the metal polystyrene foam, namely the primary derived porous carbon.

[0047] Step 4: The primary derived porous carbon is cleaned with an alcohol reagent, and is centrifuged after ultrasonic treatment for 1-2h each time, and is washed with water once after reciprocating multiple times, and is dried in an oven at 60℃.

[0048] Step 5: The cleaned primary derived porous carbon is placed in a reactor, and is subjected to the second pyrolysis treatment in an anaerobic (inert gas) atmosphere, and the second pyrolysis treatment temperature is higher than the decomposition temperature of the metal salt, such as the pyrolysis treatment temperature is 550-1200℃, the heating rate is 2-10℃ / min, and the pyrolysis time is 1-3h, and the product obtained in this process is called the derived porous carbon doped with the metal polystyrene foam, namely the derived porous carbon.

[0049] As a second aspect of the present application, a derived porous carbon is provided, which is prepared by the method for preparing a derived porous carbon described above, wherein the derived porous carbon comprises: a porous carbon skeleton and a metal and / or metal oxide anchored on the porous carbon skeleton.

[0050] In the embodiments of the present application, the polystyrene foam is pretreated below the pyrolysis temperature of the polystyrene foam, so that the surface of the polystyrene foam powder is saturated, and the metal salt is anchored in the carbon skeleton through a selective anchoring mechanism, so that a high metal coverage is maintained on the surface of the polystyrene foam powder, the probability of the metal being combined with all available coordination sites is maximized, the crosslinking between the metal and the polystyrene foam is better, a higher metal content can be stabilized, and the retention rate of the polystyrene foam powder is increased.

[0051] As a third aspect of the present application, a method for removing organophosphates is provided, which comprises: treating wastewater containing organophosphates by using the derived porous carbon described above.

[0052] In the embodiments of the present application, the derived porous carbon prepared is used to treat wastewater containing organophosphates, and the physical adsorption performance of the derived porous carbon and the chemical adsorption performance of the metal ions on the surface of the porous carbon and the organophosphates are utilized to realize the adsorption of the organophosphates. Compared with the advanced oxidation technology, the treatment process is simple to operate, is not affected by environmental factors, is environmentally friendly, economical, safe, and can be applied on a large scale in water treatment processes.

[0053] According to the embodiments of the present application, the organophosphates include at least one of an alkyl group-containing organophosphate, a halogen group-containing organophosphate, and a benzene ring-containing organophosphate. The alkyl group-containing organophosphate takes tripropyl phosphate (TPrP, C9H 21 O4P) as a research example, the benzene ring-containing organophosphate takes triphenyl phosphate (TPhP, C 18 H 15 O4P) as a research example, and the halogen-containing organophosphate takes tris(2-chloroethyl) phosphate (TCEP, C6H 12 Cl3O4P) as a research example.

[0054] The present application is described in detail below in combination with specific embodiments and drawings. It should be noted that the embodiments provided by the present application are only for illustration, but are not limited thereto.

[0055] The yield of the polystyrene foam derived porous carbon is calculated as follows:

[0056] Yield = (polystyrene foam derived porous carbon / polystyrene foam material) * 100%.

[0057] The yield of the primary derived porous carbon of the metal-doped polystyrene foam from the first pyrolysis process was calculated as follows:

[0058] Yield = (primary derived porous carbon of the metal-doped polystyrene foam - iron amount) / polystyrene foam material

[0059] The yield of the derived porous carbon of the metal-doped polystyrene foam from the second pyrolysis process was calculated (ICEP-OES test after calculation) as follows:

[0060] Yield = derived porous carbon of the metal-doped polystyrene foam * (1 - metal content %)

[0061] Comparative Example 1

[0062] Comparative Example 1 is the pyrolysis of polystyrene foam material in a tube furnace under anaerobic conditions to obtain derived porous carbon, and the specific experimental process is as follows:

[0063] The polystyrene foam material was placed in a tube furnace, and the pyrolysis temperature was increased from room temperature to 150-850°C at a heating rate of 5°C / min, and pyrolysis was carried out at this temperature for 2h to obtain derived porous carbon of the metal-doped polystyrene foam (XPS) at different temperatures. The yield of the derived porous carbon obtained is shown in Table 1.

[0064] Table 1. Pyrolysis yield of derived porous carbon of the metal-doped polystyrene foam at different pyrolysis temperatures in Comparative Example 1

[0065]

[0066] By anaerobic pyrolysis of conventional organic waste (such as biochar, sludge or kitchen garbage, etc.), a large amount of biochar can still be prepared above 300°C, and the anaerobic pyrolysis of polystyrene foam material is different from the above materials. As can be seen from Table 1, the higher the pyrolysis temperature of the polystyrene foam material, the lower the yield of the derived porous carbon of the polystyrene foam, so it is necessary to overcome the problem of low product yield in the preparation of polystyrene foam derived carbon.

[0067] Further, the anaerobic pyrolysis characteristics of the polystyrene foam material were tested, and the specific test results are shown in Figure 2 .

[0068] Figure 2 The anaerobic pyrolysis characteristics of the polystyrene foam material in Table 1 are shown in the schematic diagram.

[0069] As Figure 2As shown, the polystyrene foam material is subjected to anaerobic pyrolysis treatment under nitrogen protection, only deformation occurs in the range of room temperature to 350℃; the mass decreases rapidly in the range of 350-500℃; almost no product is generated when the temperature is greater than 500℃. Therefore, it is difficult to recover the product of polystyrene foam material, and it is more difficult to recycle the solid product, and how to improve the anaerobic pyrolysis product of polystyrene foam material is currently urgent to solve. In view of this, the present application proposes to perform anaerobic pretreatment on the polystyrene foam material below the pyrolysis temperature of the polystyrene foam material, and obtain polystyrene foam powder. Then, the obtained polystyrene foam powder is mixed with a metal salt and subjected to first anaerobic pyrolysis treatment, the metal in the metal salt is used to catalyze the cross-linking of the polystyrene foam powder to form a Fe-C skeleton carbon structure, the metal salt is used to fix the carbon, reduce the volatilization of polystyrene monomer, and improve the recovery rate of the pyrolysis product of polystyrene foam material.

[0070] Example 1

[0071] This example 1 is the preparation of iron-doped polystyrene foam derived porous carbon by using anhydrous ferric chloride as a metal salt according to the present application.

[0072] Figure 3 The preparation flow chart of the iron-doped polystyrene foam derived porous carbon in example 1 of the present application.

[0073] As shown in the preparation of iron-doped polystyrene foam derived porous carbon includes the following steps: Figure 3

[0074] 1) Preparation of polystyrene foam powder: place the polystyrene foam plate material in a reactor (such as a tube furnace), in an anaerobic environment (nitrogen atmosphere), heat to 300℃ at a heating rate of 5℃ / min, and perform anaerobic pretreatment (i.e. heat treatment) for 1.5h to obtain polystyrene foam powder (FXPS powder).

[0075] 2) Preparation of primary derived porous carbon of polystyrene foam with different metal doping amounts: 1g of polystyrene foam powder is respectively mixed with 0.1452g of anhydrous ferric chloride (polystyrene foam powder mass: Fe 3+ mass = 1:5%), 0.2904g of anhydrous ferric chloride (polystyrene foam powder mass: Fe 3+ mass = 1:10%) and 0.7261g of anhydrous ferric chloride (polystyrene foam powder mass: Fe 3+ ​The mixture of the modified polystyrene foam and the metal salt was mixed and ground together, and then placed in a tube furnace for the first pyrolysis treatment in a nitrogen atmosphere (oxygen-free). The first pyrolysis treatment temperature was 450°C, the heating rate was 5°C / min, and the pyrolysis time was 1.5 h. The primary derived porous carbon with different metal doping amounts was obtained, namely 5% FXPS450, 10% FXPS450, and 25% FXPS450.

[0076] 3) Alcohol cleaning: The primary derived porous carbon with different metal doping amounts was cleaned with ethanol (ethanol grade not required, but the higher the purity, the better), and then centrifuged after ultrasonic treatment for 1.5 h each time. After three reciprocating times, the product was washed with water once and dried in an oven at 60°C. The obtained products were 5% FXPS450E, 10% FXPS450E, and 25% FXPS450E, and E represents alcohol washing.

[0077] 4) Second pyrolysis treatment to prepare derived porous carbon: The cleaned product (5% FXPS450E, 10% FXPS450E, and 25% FXPS450E) was placed in a reactor for the second oxygen-free pyrolysis treatment in a nitrogen atmosphere. The pyrolysis treatment temperature was 550°C, the heating rate was 5°C / min, and the pyrolysis time was 1.5 h. The final product was obtained, which was named 5% FXPS450E550, 10% FXPS450E550, and 25% FXPS450E550, respectively. The yield of 5% FXPS450E550, 10% FXPS450E550, and 25% FXPS450E550 is shown in Table 2.

[0078] Table 2. Yield of iron-doped polystyrene foam-derived porous carbon pyrolysis in an oxygen-free atmosphere

[0079]

[0080] As can be seen from Tables 1 and 2, after the polystyrene foam material was modified by loading anhydrous ferric chloride, the yield of the derived porous carbon was effectively increased, and with the increase of the Fe doping content, the yield of the polystyrene foam-derived porous carbon also gradually increased, and the yield of 25% FXPS450E550 was higher.

[0081] Further, the specific surface area of the pyrolysis product in Example 1 was tested, and the specific test results are shown in Table 3.

[0082] Table 3. Specific surface area of polystyrene foam-derived porous carbon with different iron doping contents

[0083] Sample Specific surface area (cm 3 / g) XPS 550 The solid after pyrolysis was blocked by oil and the specific surface area could not be measured 10% F XPS 450 98.34 10% F XPS 450 E 174.56 10% F XPS 450 550 100.54 10% F XPS 450 E 550 292.34

[0084] As can be seen from Table 3, by doping polystyrene foam powder with metals, the obtained polystyrene foam derived porous carbon has a higher specific surface area than polystyrene foam derived porous carbon without metal doping.

[0085] Further, by using the same method as in Example 1, polystyrene foam derived porous carbon doped with nickel, cobalt and lanthanum metals was respectively prepared, i.e., 10% nickel doped polystyrene foam derived porous carbon (10% NXPS450E550), 10% cobalt doped polystyrene foam derived porous carbon (10% CXPS450E550) and 10% lanthanum doped polystyrene foam derived porous carbon (10% LXPS450E550) were prepared, and the specific surface area of the prepared polystyrene foam derived porous carbon was tested, and the test results are shown in Table 4.

[0086] Table 4. Specific surface area of nickel / lanthanum / cobalt doped polystyrene foam derived porous carbon

[0087] Sample Specific surface area (cm 3 / g) 10% N XPS 450 E 550 190.37 10% C XPS 450 E 550 137.38 10% L XPS 450 E 550 100.97

[0088] As can be seen from Table 4, by doping polystyrene foam powder with different metals, the obtained nickel / cobalt / lanthanum polystyrene foam derived porous carbon has a higher specific surface area than polystyrene foam derived porous carbon doped with lanthanum.

[0089] Application Example 1

[0090] The polystyrene foam derived porous carbon prepared in the present application has excellent performance and can be applied to a water environment system to remove new pollutants.

[0091] New pollutants refer to toxic and harmful chemical substances discharged into the environment, which have characteristics such as biological toxicity, environmental persistence, biological accumulation, etc., and which have a great risk to the ecological environment or human health, but have not yet been included in management. Organic phosphates are a class of new pollutants that can be widely detected in water bodies, soil and sediments, dust and air, and organisms. According to structural properties, organic phosphates can be divided into alkyl-containing organic phosphates, halogen-containing organic phosphates and benzene ring-containing organic phosphates, among which halogen-containing organic phosphates include tris(2-chloroethyl) phosphate (TCEP), tris(1,3-2-chloro-2-propyl) phosphate (TDCIPP) and the like. Modern sewage treatment technologies cannot degrade organic phosphates containing chlorine groups and benzene rings, which is one of the reasons why chlorine-based organic phosphates exist widely in the environment.

[0092] In the present application example 1, different polystyrene foam derived porous carbons are applied to wastewater containing organic phosphates, and different polystyrene foam derived porous carbons are used as adsorbents to adsorb and degrade organic phosphates with different structures, so as to expand the removal capacity of metal doped polystyrene foam derived porous carbon for organic phosphates.

[0093] First, select halogenated organic phosphates from the water system, specifically tri(2-chloroethyl) phosphate TCEP (C6H2O). 12 Using Cl3O4P as the research object, the adsorption performance of different polystyrene foam-derived porous carbons on TCEP was tested by controlling the TCEP concentration in the kinetic adsorption experiment. Table 5 shows the preparation conditions of different polystyrene foam-derived porous carbons.

[0094] Table 5. Preparation conditions of porous carbon derived from different polystyrene foams

[0095]

[0096] Adsorption kinetics experimental conditions: The influent concentration of TCEP before adsorption was 1 ppm; the air bath shaker was set at 25°C and 180 rpm; the adsorption time was 24 h; and the concentration ranged from 0.01 g / L to 1.2 g / L for TCEP adsorption experiments. Specific adsorption results are as follows: Figure 4 As shown.

[0097] Figure 4 The graph shows the adsorption performance test results of different polystyrene foam-derived porous carbons in halogen-containing organophosphates, taking tri(2-chloroethyl) phosphate (TCEP) as an example, at different concentrations.

[0098] Depend on Figure 4 It can be seen that the polystyrene foam-derived porous carbon obtained by direct pyrolysis of polystyrene foam at 550℃ (XPS550) has a low removal rate of TCEP, even at a TCEP concentration of 1.2 g / L, the removal rate is less than 10%. The removal rates of TCEP by 10% FXPS450, 10% FXPS450E, and 10% FXPS450550 polystyrene foam-derived porous carbon are similar, with 10% FXPS450E showing a slightly better removal rate. The reason for this is that while ethanol washing can expose the vacancies on the surface of the polystyrene foam-derived porous carbon, which is beneficial for adsorbing TCEP molecules, many heteroatoms still remain on its surface, thus the removal effect on TCEP is not significant. The removal efficiency of 10% FXPS450E550 polystyrene foam-derived porous carbon is also superior, approaching 100% at a TCEP concentration of 0.2 g / L. Therefore, the adsorption performance of polystyrene foam-derived porous carbon after the second pyrolysis treatment is significantly better than that of other polystyrene foam-derived porous carbons that have not undergone the second pyrolysis treatment. Figure 4and the above Table 3, the reason for the analysis can come from two aspects, on the one hand, the excess metal salt which is not combined with the primary derived porous carbon is washed away before the second pyrolysis treatment, avoiding the subsequent sintering, because the metal sintering affects the material adsorption performance and occupies a large number of active sites, thereby affecting the adsorption of TCEP; the other aspect is that through the second pyrolysis treatment, the impurities (such as anions in the metal salt) existing in the primary derived carbon skeleton can be pyrolyzed and removed, avoiding the influence of impurities on the adsorption performance (TCEP contains chloride ions, if there are chloride ions on the surface of polystyrene foam derived porous carbon, it will affect its adsorption performance) at the same time, more active adsorption sites are exposed.

[0099] Further, by analyzing the Figure 4 , it can be obtained that the iron doping after the second pyrolysis treatment has good adsorption performance on the derived porous carbon of polystyrene foam. Therefore, the influence of different contents of Fe doping on the adsorption performance of organophosphate will be further studied, that is, the influence of 5% FXPS450E550 (low concentration of doped metal iron salt), 10% FXPS450E550 (appropriate concentration of doped metal iron salt) and 25% FXPS450E550 (high concentration of doped metal iron salt) on the adsorption performance of organophosphate will be studied.

[0100] Application Example 2

[0101] In this application example 2, common alkyl-containing organophosphate TPrP (C9H 21 O4P), chlorine-containing organophosphate TCEP (C6H 12 Cl3O4P) and benzene ring-containing organophosphate TPhP (C 18 H 15 O4P) are taken as research objects. By studying the iron-doped polystyrene foam derived porous carbon with different contents to adsorb and degrade organophosphates with different structures, the removal capacity of iron-doped polystyrene foam derived porous carbon for organophosphates with different structures is expanded, and the applicability and breadth of iron-doped polystyrene foam derived porous carbon for organophosphates are verified.

[0102] The adsorption kinetics experiment conditions in application example 2 are: air bath shaker temperature control at 25℃, rotation speed 180rpm, adsorption time selection: 0, 5, 15, 30, 60, 120, 240, 360, 480, 720, 1440min.

[0103] Figure 5 The adsorption capacity test results of iron-doped polystyrene foam derived porous carbon with different contents in application example 2 on alkyl-containing organophosphate, taking tripropyl phosphate (TPrP) as an example, are shown in the following figure: Figure 6The removal rate test results of the derived porous carbon of the iron-doped polystyrene foam with different contents on the removal of the alkyl-containing organophosphate ester, taking tripropyl phosphate (TPrP) as an example, are shown in the figure.

[0104] It can be seen from Figure 5 and Figure 6 that the derived porous carbon of the iron-doped polystyrene foam with different contents has different adsorption performances on TPrP in the 24h adsorption kinetics experiment. Specifically, the adsorption capacity of the derived porous carbon of 5% FXPS450E550, 10% FXPS450E550 and 25% FXPS450E550 polystyrene foam all shows an upward trend with time, but the adsorption capacity tends to be balanced after 200 minutes, which is specifically shown as follows: in the 24h adsorption kinetics experiment, the initial adsorption capacity of 5% FXPS450E550, 10% FXPS450E550 and 25% FXPS450E550 is all 0, and the 24h adsorption capacity is 47.25mg / g, 37.84mg / g and 19.66mg / g respectively, and the corresponding 24h removal rate is 93.52%, 99.05% and 76.78% respectively. It can be seen that 10% FXPS450E550 almost completely removes TPrP within 24h, which cannot be achieved by 5% FXPS450E550 and 25% FXPS450E550, and the adsorption capacity of 10% FXPS450E550 is also at a high level, so the potential of 10% FXPS450E550 is greater in practical application.

[0105] Figure 7 The adsorption capacity test results of the derived porous carbon of the iron-doped polystyrene foam with different contents in application example 2 on the chloro-containing organophosphate ester TCEP are shown in the figure. Figure 8 The removal rate test results of the derived porous carbon of the iron-doped polystyrene foam with different contents in application example 2 on the chloro-containing organophosphate ester TCEP are shown in the figure.

[0106] It can be seen from Figure 7 and Figure 8It can be seen from FIGS. 1 to 3 that the adsorption capacities of the different iron-doped polystyrene foam-derived porous carbons for TCEP in the 24 h adsorption kinetics experiment are different. Specifically, the adsorption capacities of the 5% FXPS450E550, 10% FXPS450E550 and 25% FXPS450E550 polystyrene foam-derived porous carbons all increase with time, but tend to be balanced after 200 minutes, and the specific performance is that the initial adsorption capacities of the 5% FXPS450E550, 10% FXPS450E550 and 25% FXPS450E550 are all 0, and the 24 h adsorption capacities are 47.40 mg / g, 38.19 mg / g and 21.34 mg / g, respectively, and the corresponding 24 h removal rates are 93.81%, 100% and 83.43%, respectively. In view of this, the 10% FXPS450E550 can completely remove TCEP within 24 h, and has a relatively high adsorption capacity, so the potential of the 10% FXPS450E550 is greater in actual application.

[0107] Figure 9 FIG. 4 is a test result diagram of the adsorption capacity of the different iron-doped polystyrene foam-derived porous carbons in Application Example 2 for the benzene ring-containing organophosphate TPhP; Figure 10 FIG. 5 is a test result diagram of the removal rate of the different iron-doped polystyrene foam-derived porous carbons in Application Example 2 for the benzene ring-containing organophosphate TPhP.

[0108] From Figure 9 and Figure 10 It can be seen from FIGS. 1 to 3 that the adsorption capacities of the different iron-doped polystyrene foam-derived porous carbons for TCEP in the 24 h adsorption kinetics experiment are different. Specifically, the adsorption capacities of the 5% FXPS450E550, 10% FXPS450E550 and 25% FXPS450E550 polystyrene foam-derived porous carbons all increase with time, but tend to be balanced after 200 minutes, and the specific performance is that the initial adsorption capacities of the 5% FXPS450E550, 10% FXPS450E550 and 25% FXPS450E550 are all 0, and the 24 h adsorption capacities are 47.40 mg / g, 38.19 mg / g and 21.34 mg / g, respectively, and the corresponding 24 h removal rates are 93.81%, 100% and 83.43%, respectively. In view of this, the 10% FXPS450E550 can completely remove TCEP within 24 h, and has a relatively high adsorption capacity, so the potential of the 10% FXPS450E550 is greater in actual application.

[0109] Further, 10% nickel-doped polystyrene foam-derived porous carbon (10% NXPS450E550), 10% cobalt-doped polystyrene foam-derived porous carbon (10% CXPS450E550), and 10% lanthanum-doped polystyrene foam-derived porous carbon (10% LXPS450E550) were prepared, and the adsorption performance of 10% NXPS450E550, 10% CXPS450E550, and 10% LXPS450E550 for TCEP was tested by adsorption kinetics experiments.

[0110] The adsorption kinetics experiment conditions were: air bath shaker temperature control 25°C, rotation speed 180 rpm, and adsorption time selection: 0, 5, 15, 30, 60, 120, 240, 360, 480, 720, and 1440 min.

[0111] Figure 11 The adsorption capacity test results of different metal-doped polystyrene foam-derived porous carbon for chlorine-containing organophosphate TCEP are shown in the following figure: Figure 12 The removal rate test results of different metal-doped polystyrene foam-derived porous carbon for chlorine-containing organophosphate TCEP are shown in the following figure.

[0112] From Figure 11 and Figure 12 it can be seen that the adsorption performance of iron-doped polystyrene foam-derived porous carbon with different doping amounts for TCEP is different in the 24h adsorption kinetics experiment. Specifically, the adsorption capacity of 10% NXPS450E550, 10% CXPS450E550, and 10% LXPS450E550 polystyrene foam-derived porous carbon all showed an upward trend with time, but the adsorption capacity tended to be balanced after 200 minutes, specifically: in the 24h adsorption kinetics experiment, the initial adsorption capacity of 10% NXPS450E550, 10% CXPS450E550, and 10% LXPS450E550 was 0, and the 24h adsorption capacity was 33.25mg / g, 36.37mg / g, and 31.10mg / g, respectively, and the corresponding 24h removal rate was 84.78%, 88.82%, and 70.60%, respectively. Therefore, for TCEP, the adsorption capacity and removal rate of 10% CXPS450E550 are better.

[0113] Application Example 3

[0114] In this application example 3, a certain lake and the effluent of a certain reclaimed water plant were used as the research object, and the effect of different metal-doped polystyrene foam-derived porous carbon in practical application was studied.

[0115] Experimental conditions: 1 ppm of TCEP was added to ultrapure water, lake water and sewage respectively, and then 0.2 g / L of 10% FXPS450E550, 10% CXPS450E550, 10% NXPS450E550 and 10% LXPS450E550 were added respectively for 24 h of adsorption experiment. The adsorption experimental conditions were the same as in application example 2, and the sampling test time was only 1440 min.

[0116] Figure 13 Figure 1 shows the test results of TCEP removal rate of chlorine-containing organophosphates in different water bodies using porous carbon derived from polystyrene foam with different metal doping.

[0117] from Figure 13 As can be seen from the results, in the TCEP removal rate tests in different water bodies, 10% FXPS450E550 > 10% CXPS450E550 > 10% NXPS450E550 > 10% LXPS450E550. Furthermore, the four types of polystyrene foam-derived porous carbon have slightly higher TCEP removal capabilities in ultrapure water than in lake water and wastewater, but the overall removal capabilities are not significantly different, ranging from 2% to 5%. The removal rates of 10% FXPS450E550 and 10% CXPS450E550 in various water bodies are almost all above 85%, indicating that they effectively adsorb TCEP in practical applications. 10% NXPS450E550 achieves a removal rate of over 75% in various water bodies. While 10% LXPS450E550 has a weaker TCEP removal effect, it still achieves over 60%. Experimental results show that polystyrene foam-derived porous carbon with different metal doping is effective in removing TCEP from different water bodies. Different metal doping polystyrene foam-derived porous carbon can be selected for water treatment adsorption applications according to different water quality conditions.

[0118] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a derived porous carbon based on polystyrene foam, comprising: pretreating a polystyrene foam below a pyrolysis temperature of the polystyrene foam to obtain a polystyrene foam powder; mixing the polystyrene foam powder with a metal salt uniformly and then placing the mixture in an anaerobic environment to perform a first pyrolysis treatment to obtain a primary derived porous carbon of a metal-doped polystyrene foam, wherein a temperature of the first pyrolysis treatment is lower than a decomposition temperature of the metal salt; and placing the primary derived porous carbon of the metal-doped polystyrene foam in an anaerobic environment to perform a second pyrolysis treatment to obtain a derived porous carbon of the metal-doped polystyrene foam, wherein a temperature of the second pyrolysis treatment is higher than the decomposition temperature of the metal salt.

2. The method of claim 1, wherein, the primary derived porous carbon of the metal-doped polystyrene foam before the second pyrolysis treatment comprises: removing the metal salt not combined with the primary derived porous carbon by a washing process, the washing process comprises ultrasonic treatment of the primary derived porous carbon of the metal-doped polystyrene foam with an alcohol solvent and cleaning with water.

3. The method of claim 1 or 2, wherein, the metal salt comprises any one of an iron salt, a nickel salt, a cobalt salt, and a lanthanum salt. a mass ratio of the polystyrene foam powder to the metal ion is 1:0.03-0.

25.

4. The method of claim 3, wherein, the metal salt comprises any one of a metal chloride, a metal sulfate, and a metal nitrate.

5. The method of claim 1, wherein, the pretreatment comprises: placing the polystyrene foam in a reactor, heating the polystyrene foam in an anaerobic environment at a heating rate of 2-10℃ / min to 150-300℃, and performing a heat treatment for 1-3h to obtain the polystyrene foam powder; the anaerobic gas in the reactor is nitrogen or argon.

6. The method of claim 1, wherein, the heating rate of the first pyrolysis treatment and the second pyrolysis treatment is 2-10℃ / min, the temperature of the first pyrolysis treatment is 350-450℃, the temperature of the second pyrolysis treatment is 550-1200℃, and the time of the first pyrolysis treatment and the second pyrolysis treatment is 1-3h.

7. A derived porous carbon produced using the method of any one of claims 1-6, wherein, the derived porous carbon comprises a porous carbon skeleton and a metal and / or a metal oxide anchored on the porous carbon skeleton. 8.A method for removing an organophosphate, comprising: treating wastewater containing an organophosphate with the derived porous carbon of claim 7.

9. The method of claim 8, wherein, the organophosphate comprises at least one of an organophosphate containing an alkyl group, an organophosphate containing a halogen group, and an organophosphate containing a benzene ring group.

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