CN110538637A

CN110538637A - Method for converting plastic into carbon nano-structure material

Info

Publication number: CN110538637A
Application number: CN201910907874.8A
Authority: CN
Inventors: 卡马里阿里
Original assignee: Northeastern University China
Current assignee: Northeastern University China
Priority date: 2019-09-25
Filing date: 2019-09-25
Publication date: 2019-12-06
Anticipated expiration: 2039-09-25
Also published as: CN110538637B

Abstract

The invention belongs to the field of plastic recycling, and discloses a method for converting plastic into a carbon nano-structure material. The method can produce the carbonaceous nanostructure material without harmful substances such as H2O2, urea and the like, and heats the plastic by using the salt or the salt mixture at the temperature that the plastic and the salt or the salt mixture are both in a molten state; and then washing and desalting are carried out to obtain the carbonaceous nano-structure material. The resulting carbon nanostructures are present in powder form and contain at least 10 wt% of elemental carbon. The carbonaceous nanostructure material produced has at least 20% by mass of the size of 1-100 nm. The carbon nano-structure material is heated at 450-1300 ℃ in a protective atmosphere or in a molten salt medium to obtain the carbon material with the nano-structure.

Description

Method for converting plastic into carbon nano-structure material

Technical Field

The invention belongs to the field of plastic recycling, and particularly relates to a method for converting plastic into a carbon nano-structure material.

background

Plastics have many excellent properties such as low cost, light weight, high strength, non-toxicity and high corrosion resistance in acidic and alkaline liquids. Accordingly, plastics are used in many applications, including bottles and plastic films in the food and beverage industry worldwide. Due to the widespread use of plastics, annual consumption in excess of 3 million tons has created new global challenges associated with waste plastics.

current strategies to reduce the negative impact of waste plastics on the environment are accompanied by fundamental or practical limitations. Which is discussed below. Recycling waste plastics does not completely solve the environmental challenge, since only a small portion of the waste plastics can be directly reused, the remainder being chemically decomposed, incinerated or buried. Waste plastics can be considered as an alternative fuel, considering that 7 tons of crude oil are basically used to produce 1 ton of PET plastics, which makes PET have a very high calorific value, about twice as high as gasoline.

However, the energy utilization rate associated with incineration disposal is extremely low, involving the generation of toxic gases, causing environmental pollution. The burrs of plastic also cause environmental problems, preventing their degradation for hundreds of years due to their extremely high chemical inertness. Both the burying and the landfill of plastic wastes cause serious environmental pollution problems, endangering the natural ecological balance.

With the rise of biotechnology, the microbial degradation of plastics is receiving more and more attention. Although bacterial degradation of plastics has been demonstrated, its time-consuming nature poses limitations, particularly in large scale operations. Therefore, there is an urgent need to develop an efficient, low-cost and environmentally friendly plastic waste disposal strategy to protect the environment. For example, waste plastic materials can be converted into fibers for concrete, thereby improving its mechanical properties. Another strategy is to convert plastic materials into nanostructured carbon materials for various applications.

For example, Hu et al produce carbon nanodots by air oxidation of plastic materials followed by hydrothermal treatment in a water-based H2O2 solution (Y.P.Hu, Z.J.Gao, J.Yang, H.Chen, L.Han, environmental pollution to fluorescent carbon dots for "on-off-on" sensing of both metallic and phosphorous ions, Journal of Colloid and Interface Science 539,2019,481-8). Elessawy et al used autoclaving and urea to convert PET plastics into carbon nanostructures (N.A. Elessawy, J.E.Nady, W.Wazer, A.B.Kashyout, Development of High-Performance Supercapacitorbased on a Novel Controllable Green Synthesis for 3D Nitrogen dot graphics, Scientific Report 9,2019,1129).

Description of the invention

The invention provides a novel method for converting plastics into carbon nano-structure materials, aiming at overcoming the problem that harmful substances such as H2O2, urea and the like are used in the existing production of carbon nano-structure materials by utilizing plastics.

The specific technical scheme is that the method for converting the plastic into the carbonaceous nano-structure material comprises the following steps:

a) Heating the plastic with the salt or salt mixture at a temperature at which both the plastic and the salt or salt mixture are molten; the weight of the plastic multiplied by 100 is more than or equal to the weight of the salt or the salt mixture;

The salt or salt mixture comprises ZnCl2, SnCl2, a mixture of ZnCl2 and CaCl2, a mixture of PbCl2 and NaCl, a mixture of KCl and FeCl2 and a mixture of LiCl and KCl, and one of the six; the plastic is PET;

b) Treating the molten mixture obtained by step a), washing at room temperature to remove salts; washing is water washing or acid washing; after washing, the resulting suspension is filtered through filter paper or centrifuged to recover the carbonaceous nanostructured material.

When the salt is ZnCl2, the heating temperature is 270-450 ℃.

When the salt is SnCl2, the heating temperature is 250-450 ℃.

when the salt mixture is a mixture of ZnCl2 and CaCl2, wherein CaCl2 is less than 5 mol%, the heating temperature is 400-450 ℃.

When the salt mixture is a mixture of PbCl2 and NaCl, wherein 70 mol% of PbCl2 and 30 mol% of NaCl, the heating temperature is 420-450 ℃.

When the salt mixture is a mixture of KCl and FeCl2, wherein 60 mol% of KCl and 40 mol% of FeCl2, the heating temperature is 400-450 ℃.

When the salt mixture is a mixture of LiCl and KCl, wherein LiCl is 60 mol% and KCl is 40 mol%, the heating temperature is 350-450 ℃.

The carbonaceous nanostructure material prepared by the method and the method for preparing the carbon material with the nanostructure are characterized in that the carbonaceous nanostructure material is heated at the temperature of 450-1300 ℃ to form the carbon material with the nanostructure; the heating is carried out in a protective atmosphere or in a molten salt medium.

Further, the protective atmosphere is nitrogen, helium or argon.

further, the heating is carried out in a molten salt medium, and the selected molten salt comprises NaCl; followed by washing at room temperature to remove the salt from the molten mixture to yield carbon nanostructures.

The method has the beneficial effect that the carbonaceous nano-structure material can be produced without harmful substances such as H2O2, urea and the like. The carbon nanostructures thus produced are useful in a variety of applications, particularly for energy storage devices, such as supercapacitors and batteries, and for water and air purification purposes. The resulting carbon nanostructures are present in powder form and contain at least 10 wt% of elemental carbon. The carbon nano-structure produced has at least 20% of the size of 1-100 nm by mass. The method has low cost, and is environmentally friendly and sustainable.

Drawings

Fig. 1 is an XRD analysis pattern of carbonaceous nanostructured material obtained by heating ZnCl2 and PET to 350 ℃.

Fig. 2 is a UV-visible absorption spectrum of MO after different adsorption times for carbonaceous nanostructured materials obtained by heating ZnCl2 and PET to 350 ℃.

Figure 3 is an SEM morphology of carbonaceous nanostructured material prepared by treating PET with ZnCl2 at 350 ℃ and then washing away the ZnCl2 content.

Fig. 4 is an SEM micrograph of the nanostructured carbon material obtained in example 2.

FIG. 5 is another SEM micrograph of a nanostructured carbon material obtained in the same manner as in FIG. 4.

Fig. 6 is an EDX analysis record chart of the nano-structured carbon material obtained in the same manner as fig. 4.

Figure 7 high resolution TEM micrograph of the product obtained in example 3.

Detailed Description

Example 1

20g of ZnCl2 and 5g of polyethylene terephthalate plastic were mixed and the mixture was placed in an alumina crucible. The crucible was heated to 350 ℃ in an electric resistance furnace at a heating rate of 10 ℃ and held at that temperature for 20 minutes. The furnace was then cooled to room temperature. The XRD pattern of the resulting material is shown in FIG. 1. According to the figure, the product is a mixture of C26H25N3 and ZnCl 2.

Figure 1 XRD analysis of carbonaceous nanostructured material obtained by heating ZnCl2 and PET to 350 ℃.

Fig. 2 shows Methyl Orange (MO) adsorption properties of the produced nanostructured carbonaceous material. For this experiment, a 0.1g/l concentration of MO solution was treated with a 2g/l concentration of nanostructured carbonaceous material.

Fig. 2 UV-visible absorption spectra of MO after different adsorption times for carbonaceous nanostructured materials obtained by heating ZnCl2 and PET to 350 ℃.

The ZnCl2 content of the product was dissolved in water, the carbonaceous nanostructured material was filtered, and the filtrate was dried at 80 ℃ for 2 hours. An SEM micrograph of the obtained nanostructured carbonaceous material is shown in fig. 3, where particles with a size in the range of 10nm to 2 μm and sheet-like entities with a lateral dimension of 1 to 5 μm are present.

Example 2

20g of PET material were thoroughly mixed with 100g of ZnCl2 salt and the mixture was placed in an alumina crucible 50mm in diameter and 100mm in height. The mixture was then covered with another 20g of zncl2 salt. The alumina crucible was then heated at 15 ℃/min to the target temperature of 1300 ℃ and held at that temperature for 1 hour using a muffle furnace (labottery LX 1814). After cooling to room temperature, the product was washed with 1mol/l hydrochloric acid solution at 80 ℃ for 12 hours to remove residual salts and other possible impurities and then successively with deionized water to a pH of about 7. The sample was then vacuum filtered and dried at 80 ℃ overnight.

Fig. 4 shows an SEM micrograph of the obtained nanostructured carbon material. The preparation steps of the material are as follows: the mixture of PET plastic (10g) and ZnCl2 product (50g) was heated to 350 ℃ and stored at this temperature for 20 min. The sample was then heated to 1300 ℃ without any hold time and cooled to room temperature. The resulting suspension was then vacuum filtered using HCl cleaning material.

The material comprises particles having a size of 10nm to 200nm and graphene sheets having a lateral dimension of 2 μm to 20 μm. The BET surface area of the resulting carbon nanostructure material was 879m 2/g. Fig. 5 shows another SEM micrograph of the carbon nanostructure material produced by the method used in fig. 4. The presence of carbon nanoparticles having a size of 1nm to 50nm can be detected. Figure 6 shows an EDX analysis recorded on the nanostructured carbon material wherein the purity of the carbon product was determined to be 99.81 wt%. The material was washed by HCl, and residual HCl in the sample was further removed by heat treatment at 250 ℃ for 1 hour in air, vacuum or argon gas to prepare a nano-structured carbon material having a carbon content of 99.99% by weight. The electrical conductivity of the nanostructured carbon material was measured to be about 10S/m.

FIG. 6 is an EDX analysis chart of the nano-structured carbon material obtained by the same method as in FIG. 4. The nanostructured carbon material prepared above is used as an electrode for supercapacitor applications.

Electrochemical capacitance performance of the nanostructured carbon material was evaluated using a three-electrode system that prepares the working electrode by mixing the nanostructured carbon material, conductive carbon (C45), and polytetrafluoroethylene binder (PTFE) in a mass ratio of 8:1: 1. The mixture was loaded on a 1.2 cm diameter Ni plate at a mass loading of 4.57mg/cm 2. The electrolyte was 6M KOH. Platinum wire and saturated calomel electrode (Hg/HgCl saturated KCl) were used as lead and reference electrodes, respectively. Table 1 shows the capacitance of the electrode material measured at different current densities. At a current density of 0.2A/g, a high capacitance of 268.4F/g was recorded

Current Density (A/g)	0.2	0.5	1	2	5	10	20
								Capacitor (F/g)	268.4	181.5	162	158	132.5	113	82

Example 3

20g of PET material were thoroughly mixed with 100g of ZnCl2 salt and the mixture was heated to 750 ℃ in an air atmosphere without residence time at the highest temperature. The mixture was cooled to room temperature to form a nanostructured carbon material. The nanostructured carbon material is composed of carbon nanoparticles and a carbon nanoflake bearing ZnO nanocrystals. Figure 7 shows a high resolution TEM micrograph of the sample.

The product shows high performance in the adsorption and decomposition of dyes such as Methyl Orange (MO). The solution of the nano-structured carbon material and the ZnO crystal with the concentration of 2g/l can completely remove the MO solution with the concentration of 0.1 g/l. The high adsorptivity of the product is attributed to the nanostructured carbon material. The high catalytic activity of the product is attributed to the ZnO phase.

Example 4

A mixture of 10g PET and 60g SnCl2 was placed in an alumina furnace and heated to 300 ℃ at a heating rate of 10 ℃ per minute and held at this temperature for 1 hour. The sample was then cooled to room temperature and washed with clean water to remove salts from the resulting material. The resulting solid material was washed with HCl (30%) and filtered. Analysis of the sample by XRD confirmed that the obtained nanostructured carbon material comprises C7H6N2O4 and C8H6O 4. Transmission Electron Microscope (TEM) micrographs show that the nanostructured carbide product has a nanostructure consisting of particles ranging in size from 10nm to 300 nm.

Example 5

The mixture PET (10g) and LiCl (24g) and CaCl2(33g) were placed in an alumina furnace and heated to 380 ℃. The temperature was maintained at 380 ℃ for 1 hour and then cooled to room temperature. The resulting material was then washed with clean water and filtered. The grain size of the obtained carbide product is 20nm-400 nm.

Example 6

5g of polyvinyl chloride (PVC) and 50g of a salt mixture (53% by weight of KNO3, 40% by weight of NaNO2 and 7% by weight of NaNO3) were heated to 250 ℃ and stored at this temperature for 1 h. The temperature was then lowered to room temperature, the salt was washed with distilled water and the filtrate was filtered under vacuum. The resulting carbon material has a nanostructure comprising nanoparticles in the range of 10-500 nm. The melting points of the PVC material and the salt are less than 200 ℃ and 142 ℃, respectively. Thus, at 250 ℃, both the PVC material and the salt are in a liquid state.

Claims

1. A method of converting a plastic to a carbonaceous nanostructured material comprising the steps of:

2. The method for converting a plastic into a carbonaceous nanostructured material according to claim 1, wherein the salt is ZnCl2 and the heating temperature is 270 ℃ to 450 ℃.

3. The method of converting a plastic to a carbonaceous nanostructured material according to claim 1, wherein the salt is SnCl2 and the heating temperature is 250 ℃ to 450 ℃.

4. The method for converting plastic into carbonaceous nanostructured material according to claim 1, wherein the salt mixture is a mixture of ZnCl2 and CaCl2, wherein CaCl2 is less than 5 mol% and the heating temperature is 400 ℃ to 450 ℃.

5. The method for converting plastic into a carbonaceous nanostructured material according to claim 1, wherein the salt mixture is a mixture of PbCl2 and NaCl, wherein 70 mol% PbCl2 and 30 mol% NaCl, the heating temperature is 420 ℃ to 450 ℃.

6. The method for converting plastic into carbonaceous nanostructured material according to claim 1, wherein the salt mixture is a mixture of KCl and FeCl2, wherein 60 mol% KCl and 40 mol% FeCl2, the heating temperature is 400 ℃ to 450 ℃.

7. The method for converting a plastic into a carbonaceous nanostructured material according to claim 1, wherein the salt mixture is a mixture of LiCl and KCl, wherein 60 mol% LiCl and 40 mol% KCl, and the heating temperature is 350 ℃ to 450 ℃.

8. A method of producing a nanostructured carbon material using the carbonaceous nanostructured material produced by the method according to any one of claims 1 to 7, characterized in that the carbonaceous nanostructured material is heated at a temperature of 450 ℃ to 1300 ℃ to form carbon nanostructures; the heating is carried out in a protective atmosphere or in a molten salt medium.

9. The method for producing a nanostructured carbon material according to claim 8, wherein the protective atmosphere is nitrogen, helium or argon.

10. The method of claim 8, wherein the heating is performed in a molten salt medium, the molten salt selected from the group consisting of NaCl; followed by washing at room temperature to remove the salt from the molten mixture to yield carbon nanostructures.