METHOD FOR TREATING WASTE PLASTIC BASED ON PERSULFATE SYSTEM

Abstract

A method for treating a waste plastic based on a persulfate system is provided. The method includes the following steps: mixing the waste plastic, sulfuric acid, sulfate, peroxymonosulfate, and water, and reacting at 80-140? C. for 3-15 h to complete the treatment; where the waste plastic is polyethylene or polyethylene terephthalate; and the sulfate is copper sulfate or ferrous sulfate. The present invention reasonably regulates and controls each parameter in the reaction process while constructing a homogeneous catalysis system of transition metal activated peroxymonosulfate, and finally directionally converts the waste plastic into C.sub.7H.sub.12 and C.sub.10H.sub.12 fuels, which realizes high-efficiency recycling of the waste plastic, has a simple and convenient working procedure, and has a wide application prospect.

Claims

1. A method for a treatment of a waste plastic based on a persulfate system, comprising the following steps: mixing the waste plastic, sulfuric acid, sulfate, peroxymonosulfate, and water to obtain a mixed solution, and then allowing a reaction of the mixed solution to complete the treatment.

2. The method according to claim 1, wherein the waste plastic is polyethylene or polyethylene terephthalate.

3. The method according to claim 2, wherein the sulfate is copper sulfate or ferrous sulfate.

4. The method according to claim 3, wherein the peroxymonosulfate is potassium peroxymonosulfate or sodium peroxymonosulfate.

5. The method according to claim 3, wherein the waste plastic in the mixed solution has a mass concentration of 1-5 g/L.

6. The method according to claim 5, wherein the sulfuric acid in the mixed solution has a concentration of 5?10.sup.?4-5?10.sup.?3 mol/L.

7. The method according to claim 6, wherein when the sulfate is the copper sulfate, the copper sulfate in the mixed solution has a concentration of 0.08-0.49 mmol/L; and when the sulfate is the ferrous sulfate, the ferrous sulfate in the mixed solution has a concentration of 3-13 mmol/L.

8. The method according to claim 7, wherein the peroxymonosulfate in the mixed solution has a concentration of 3-13 mmol/L. 9. The method according to claim 7, wherein the reaction is performed at a temperature of 80-140? C. 10. The method according to claim 9, wherein the reaction is performed for 3-15 h.

9. The method according to claim 4, wherein the waste plastic in the mixed solution has a mass concentration of 1-5 g/L.

10. The method according to claim 8, wherein the reaction is performed at a temperature of 80-140? C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 is a graph showing the results of types and mass fractions of products according to Example 2;

[0021] FIG. 2 is a graph showing the results of types and mass fractions of products according to Example 6;

[0022] FIG. 3 is a graph showing the results of types and mass fractions of products according to Example 9; and

[0023] FIG. 4 is a graph showing the results of types and mass fractions of products according to Example 10.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The present invention provides a method for treating a waste plastic based on a persulfate system, which comprises the following steps: [0025] mixing the waste plastic, sulfuric acid, sulfate, peroxymonosulfate, and water, and then reacting to complete the treatment.

[0026] In the present invention, the waste plastic is preferably polyethylene or polyethylene terephthalate.

[0027] In the present invention, the sulfate is preferably copper sulfate or ferrous sulfate.

[0028] In the present invention, the peroxymonosulfate is preferably potassium peroxymonosulfate or sodium peroxymonosulfate.

[0029] In the present invention, the waste plastic in the mixed solution has a mass concentration of preferably 1-5 g/L, further preferably 2-4 g/L, and more preferably 2.5-3.5 g/L.

[0030] In the present invention, the sulfuric acid in the mixed solution has a concentration of preferably 5?10.sup.?4-5?10.sup.?3 mol/L, further preferably 6?10.sup.?4-4?10.sup.?3 mol/L, and more preferably 7?10.sup.?4-3?10.sup.?3 mol/L.

[0031] In the present invention, when the sulfate is copper sulfate, the copper sulfate in the mixed solution has a concentration of preferably 0.08-0.49 mmol/L, further preferably 0.10-0.47 mmol/L, and more preferably 0.15-0.42 mmol/L; and

[0032] when the sulfate is ferrous sulfate, the ferrous sulfate in the mixed solution has a concentration of preferably 3-13 mmol/L, further preferably 5-11 mmol/L, and more preferably 7-9 mmol/L.

[0033] In the present invention, the peroxymonosulfate in the mixed solution has a concentration of preferably 3-13 mmol/L, further preferably 5-11 mmol/L, and more preferably 7-9 mmol/L.

[0034] In the present invention, the reaction is performed at a temperature of preferably 80-140? C., further preferably 90-130? C., and more preferably 100-120? C.

[0035] In the present invention, the reaction is performed for preferably 3-15 h, further preferably 5-13 h, and more preferably 7-11 h.

[0036] In the present invention, the specific mechanism for converting a waste plastic into a fuel based on a persulfate system is as follows: [0037] after sulfate and peroxymonosulfate (PMS) are added to the waste plastic, metal ions in the sulfate activate hydrogen peroxymonosulfate (HSO.sub.5.sup.?) to generate high-valence metals, SO.sub.4.sup..Math.?, and .sup..Math.OH. In addition, two HSO.sub.5.sup.?; molecules interact to generate singlet oxygen (.sup.1O.sub.2), and electrons (e.sup.?) react with dissolved oxygen to generate superoxide radicals (O.sub.2.sup..Math.?). The interaction of .Math.OH with the carbon chain (RH) can generate an R.Math.radical. Under the combined action of Cu(III), SO.sub.4.sup..Math.?, .sup.1O.sub.2, and O.sub.2.sup..Math.?, the CC bond of the polymer in the plastic is broken, and finally transformed into C.sub.7H.sub.12 and C.sub.10H.sub.12 fuels.

[0038] The technical solutions provided by the present invention will be described in detail below with reference to the examples, which, however, should not be construed as limiting the scope of the present invention.

Example 1

[0039] Polyethylene (PE), sulfuric acid, copper sulfate, sodium peroxymonosulfate, and water were mixed well to obtain a mixed solution, wherein in the mixed solution, the PE had a mass concentration of 1 g/L, the sulfuric acid had a concentration of 5?10.sup.?3 mol/L, the copper sulfate had a concentration of 0.0813 mmol/L, and the sodium peroxymonosulfate had a concentration of 3.25 mmol/L; and the mixed solution was reacted at 140? C. for 6 h to complete the treatment.

[0040] The obtained sample was naturally cooled to room temperature. 0.9 mL of suspension was taken by using a syringe, and filtered by using a 0.22 ?m organic filter membrane. The filtrate was extracted by using 0.9 mL of methylbenzene after the filtering was completed. Finally, the types of products and the proportions of various substances were qualitatively analyzed by using a gas chromatography-mass spectrometer. The results show that, in the product obtained in this example, C.sub.7H.sub.12 fuel had a mass fraction of 54.48%, and C.sub.10H.sub.12 fuel had a mass fraction of 45.52%.

Example 2

[0041] Polyethylene (PE), sulfuric acid, copper sulfate, sodium peroxymonosulfate, and water were mixed well to obtain a mixed solution, wherein in the mixed solution, the PE had a mass concentration of 1 g/L, the sulfuric acid had a concentration of 5?10.sup.?3 mol/L, the copper sulfate had a concentration of 0.0813 mmol/L, and the sodium peroxymonosulfate had a concentration of 6.50 mmol/L; and the mixed solution was reacted at 140? C. for 15 h to complete the treatment.

[0042] The obtained sample was naturally cooled to room temperature. 0.9 mL of suspension was taken by using a syringe, and filtered by using a 0.22 ?m organic filter membrane. The filtrate was extracted by using 0.9 mL of methylbenzene after the filtering was completed. Finally, the types of products and the proportions of various substances were qualitatively analyzed by using a gas chromatography-mass spectrometer to obtain a graph showing types and mass fractions of the products. As shown in FIG. 1, it can be seen that, in the product obtained in this example, C.sub.7H.sub.12 fuel had a mass fraction of 63.77%, and C.sub.10H.sub.12 fuel had a mass fraction of 36.23%.

Example 3

[0043] Polyethylene terephthalate (PET), sulfuric acid, copper sulfate, sodium peroxymonosulfate, and water were mixed well to obtain a mixed solution, wherein in the mixed solution, the PET had a mass concentration of 1 g/L, the sulfuric acid had a concentration of 5?10.sup.?3 mol/L, the copper sulfate had a concentration of 0.0813 mmol/L, and the sodium peroxymonosulfate had a concentration of 3.25 mmol/L; and the mixed solution was reacted at 140? C. for 6 h to complete the treatment.

[0044] The obtained sample was naturally cooled to room temperature. 0.9 mL of suspension was taken by using a syringe, and filtered by using a 0.22 ?m organic filter membrane. The filtrate was extracted by using 0.9 mL of methylbenzene after the filtering was completed. Finally, the types of products and the proportions of various substances were qualitatively analyzed by using a gas chromatography-mass spectrometer. The results show that, in the product obtained in this example, C.sub.7H.sub.12 fuel had a mass fraction of 0%, and C.sub.10H.sub.12 fuel had a mass fraction of 100%.

Example 4

[0045] Polyethylene (PE), sulfuric acid, ferrous sulfate, sodium peroxymonosulfate, and water were mixed well to obtain a mixed solution, wherein in the mixed solution, the PE had a mass concentration of 2 g/L, the sulfuric acid had a concentration of 5?10.sup.?3.5 mol/L, the ferrous sulfate had a concentration of 3.25 mmol/L, and the sodium peroxymonosulfate had a concentration of 3.25 mmol/L; and the mixed solution was reacted at 80? C. for 12 h to complete the treatment.

[0046] The obtained sample was naturally cooled to room temperature. 0.9 mL of suspension was taken by using a syringe, and filtered by using a 0.22 ?m organic filter membrane. The filtrate was extracted by using 0.9 mL of methylbenzene after the filtering was completed. Finally, the types of products and the proportions of various substances were qualitatively analyzed by using a gas chromatography-mass spectrometer. The results show that, in the product obtained in this example, C.sub.7H.sub.12 fuel had a mass fraction of 0%, and C.sub.10H.sub.12 fuel had a mass fraction of 100%.

Example 5

[0047] Polyethylene terephthalate (PET), sulfuric acid, ferrous sulfate, potassium peroxymonosulfate, and water were mixed well to obtain a mixed solution, wherein in the mixed solution, the PET had a mass concentration of 2 g/L, the sulfuric acid had a concentration of 5?10.sup.?3.5 mol/L, the ferrous sulfate had a concentration of 3.25 mmol/L, and the potassium peroxymonosulfate had a concentration of 3.25 mmol/L; and the mixed solution was reacted at 140? C. for 15 h to complete the treatment.

[0048] The obtained sample was naturally cooled to room temperature. 0.9 mL of suspension was taken by using a syringe, and filtered by using a 0.22 ?m organic filter membrane. The filtrate was extracted by using 0.9 mL of methylbenzene after the filtering was completed. Finally, the types of products and the proportions of various substances were qualitatively analyzed by using a gas chromatography-mass spectrometer. The results show that, in the product obtained in this example, C.sub.7H.sub.12 fuel had a mass fraction of 10.96%, and C.sub.10H.sub.12 fuel had a mass fraction of 89.04%.

Example 6

[0049] Polyethylene terephthalate (PET), sulfuric acid, ferrous sulfate, potassium peroxymonosulfate, and water were mixed well to obtain a mixed solution, wherein in the mixed solution, the PET had a mass concentration of 1 g/L, the sulfuric acid had a concentration of 5?10.sup.?3.5 mol/L, the ferrous sulfate had a concentration of 3.25 mmol/L, and the potassium peroxymonosulfate had a concentration of 6.50 mmol/L; and the mixed solution was reacted at 140? C. for 15 h to complete the treatment.

[0050] The obtained sample was naturally cooled to room temperature. 0.9 mL of suspension was taken by using a syringe, and filtered by using a 0.22 ?m organic filter membrane. The filtrate was extracted by using 0.9 mL of methylbenzene after the filtering was completed. Finally, the types of products and the proportions of various substances were qualitatively analyzed by using a gas chromatography-mass spectrometer to obtain a graph showing types and mass fractions of the products. As shown in FIG. 2, it can be seen that, in the product obtained in this example, C.sub.7H.sub.12 fuel had a mass fraction of 55.93%, and C.sub.10H.sub.12 fuel had a mass fraction of 44.07%.

Example 7

[0051] Polyethylene (PE), sulfuric acid, copper sulfate, potassium peroxymonosulfate, and water were mixed well to obtain a mixed solution, wherein in the mixed solution, the PE had a mass concentration of 3 g/L, the sulfuric acid had a concentration of 5?10.sup.?4 mol/L, the copper sulfate had a concentration of 0.1625 mmol/L, and the potassium peroxymonosulfate had a concentration of 6.50 mmol/L; and the mixed solution was reacted at 140? C. for 15 h to complete the treatment.

[0052] The obtained sample was naturally cooled to room temperature. 0.9 mL of suspension was taken by using a syringe, and filtered by using a 0.22 ?m organic filter membrane. The filtrate was extracted by using 0.9 mL of methylbenzene after the filtering was completed. Finally, the types of products and the proportions of various substances were qualitatively analyzed by using a gas chromatography-mass spectrometer. The results show that, in the product obtained in this example, C.sub.7H.sub.12 fuel had a mass fraction of 62.90%, and C.sub.10H.sub.12 fuel had a mass fraction of 37.10%.

Example 8

[0053] Polyethylene terephthalate (PET), sulfuric acid, copper sulfate, potassium peroxymonosulfate, and water were mixed well to obtain a mixed solution, wherein in the mixed solution, the PET had a mass concentration of 3 g/L, the sulfuric acid had a concentration of 5?10.sup.?4 mol/L, the copper sulfate had a concentration of 0.1625 mmol/L, and the potassium peroxymonosulfate had a concentration of 6.50 mmol/L; and the mixed solution was reacted at 120? C. for 12 h to complete the treatment.

[0054] The obtained sample was naturally cooled to room temperature. 0.9 mL of suspension was taken by using a syringe, and filtered by using a 0.22 ?m organic filter membrane. The filtrate was extracted by using 0.9 mL of methylbenzene after the filtering was completed. Finally, the types of products and the proportions of various substances were qualitatively analyzed by using a gas chromatography-mass spectrometer. The results show that, in the product obtained in this example, C.sub.7H.sub.12 fuel had a mass fraction of 0%, and C.sub.10H.sub.12 fuel had a mass fraction of 100%.

Example 9

[0055] Polyethylene terephthalate (PET), sulfuric acid, copper sulfate, sodium peroxymonosulfate, and water were mixed well to obtain a mixed solution, wherein in the mixed solution, the PET had a mass concentration of 1 g/L, the sulfuric acid had a concentration of 5?10.sup.?4 mol/L, the copper sulfate had a concentration of 0.1625 mmol/L, and the sodium peroxymonosulfate had a concentration of 6.50 mmol/L; and the mixed solution was reacted at 140? C. for 15 h to complete the treatment.

[0056] The obtained sample was naturally cooled to room temperature. 0.9 mL of suspension was taken by using a syringe, and filtered by using a 0.22 ?m organic filter membrane. The filtrate was extracted by using 0.9 mL of methylbenzene after the filtering was completed. Finally, the types of products and the proportions of various substances were qualitatively analyzed by using a gas chromatography-mass spectrometer to obtain a graph showing types and mass fractions of the products. As shown in FIG. 3, it can be seen that, in the product obtained in this example, C.sub.7H.sub.12 fuel had a mass fraction of 6.95%, and C.sub.10H.sub.12 fuel had a mass fraction of 93.05%.

Example 10

[0057] Polyethylene (PE), sulfuric acid, ferrous sulfate, sodium peroxymonosulfate, and water were mixed well to obtain a mixed solution, wherein in the mixed solution, the PE had a mass concentration of 1 g/L, the sulfuric acid had a concentration of 5?10.sup.?3 mol/L, the ferrous sulfate had a concentration of 6.50 mmol/L, and the sodium peroxymonosulfate had a concentration of 6.50 mmol/L; and the mixed solution was reacted at 140? C. for 15 h to complete the treatment.

[0058] The obtained sample was naturally cooled to room temperature. 0.9 mL of suspension was taken by using a syringe, and filtered by using a 0.22 ?m organic filter membrane. The filtrate was extracted by using 0.9 mL of methylbenzene after the filtering was completed. Finally, the types of products and the proportions of various substances were qualitatively analyzed by using a gas chromatography-mass spectrometer to obtain a graph showing types and mass fractions of the products. As shown in FIG. 4, it can be seen that, in the product obtained in this example, C.sub.7H.sub.12 fuel had a mass fraction of 9.71%, and C.sub.10H.sub.12 fuel had a mass fraction of 90.29%.

Example 11

[0059] Polyethylene terephthalate (PET), sulfuric acid, ferrous sulfate, sodium peroxymonosulfate, and water were mixed well to obtain a mixed solution, wherein in the mixed solution, the PET had a mass concentration of 3 g/L, the sulfuric acid had a concentration of 5?10.sup.?3 mol/L, the ferrous sulfate had a concentration of 6.50 mmol/L, and the sodium peroxymonosulfate had a concentration of 6.50 mmol/L; and the mixed solution was reacted at 140? C. for 3 h to complete the treatment.

[0060] The obtained sample was naturally cooled to room temperature. 0.9 mL of suspension was taken by using a syringe, and filtered by using a 0.22 ?m organic filter membrane. The filtrate was extracted by using 0.9 mL of methylbenzene after the filtering was completed. Finally, the types of products and the proportions of various substances were qualitatively analyzed by using a gas chromatography-mass spectrometer. The results show that, in the product obtained in this example, C.sub.7H.sub.12 fuel had a mass fraction of 0%, and C.sub.10H.sub.12 fuel had a mass fraction of 100%.

Example 12

[0061] Polyethylene (PE), sulfuric acid, copper sulfate, potassium peroxymonosulfate, and water were mixed well to obtain a mixed solution, wherein in the mixed solution, the PE had a mass concentration of 4 g/L, the sulfuric acid had a concentration of 5?10.sup.?3.5 mol/L, the copper sulfate had a concentration of 0.3250 mmol/L, and the potassium peroxymonosulfate had a concentration of 9.75 mmol/L; and the mixed solution was reacted at 80? C. for 12 h to complete the treatment.

[0062] The obtained sample was naturally cooled to room temperature. 0.9 mL of suspension was taken by using a syringe, and filtered by using a 0.22 ?m organic filter membrane. The filtrate was extracted by using 0.9 mL of methylbenzene after the filtering was completed. Finally, the types of products and the proportions of various substances were qualitatively analyzed by using a gas chromatography-mass spectrometer. The results show that, in the product obtained in this example, C.sub.7H.sub.12 fuel had a mass fraction of 0%, and C.sub.10H.sub.12 fuel had a mass fraction of 100%.

Example 13

[0063] Polyethylene terephthalate (PET), sulfuric acid, copper sulfate, potassium peroxymonosulfate, and water were mixed well to obtain a mixed solution, wherein in the mixed solution, the PET had a mass concentration of 4 g/L, the sulfuric acid had a concentration of 5?10.sup.?3.5 mol/L, the copper sulfate had a concentration of 0.3250 mmol/L, and the potassium peroxymonosulfate had a concentration of 9.75 mmol/L; and the mixed solution was reacted at 140? C. for 15 h to complete the treatment.

[0064] The obtained sample was naturally cooled to room temperature. 0.9 mL of suspension was taken by using a syringe, and filtered by using a 0.22 ?m organic filter membrane. The filtrate was extracted by using 0.9 mL of methylbenzene after the filtering was completed. Finally, the types of products and the proportions of various substances were qualitatively analyzed by using a gas chromatography-mass spectrometer. The results show that, in the product obtained in this example, C.sub.7H.sub.12 fuel had a mass fraction of 6.95%, and C.sub.10H.sub.12 fuel had a mass fraction of 93.05%.

Example 14

[0065] Polyethylene (PE), sulfuric acid, ferrous sulfate, potassium peroxymonosulfate, and water were mixed well to obtain a mixed solution, wherein in the mixed solution, the PE had a mass concentration of 5 g/L, the sulfuric acid had a concentration of 5?10.sup.?4 mol/L, the ferrous sulfate had a concentration of 9.75 mmol/L, and the potassium peroxymonosulfate had a concentration of 9.75 mmol/L; and the mixed solution was reacted at 140? C. for 12 h to complete the treatment.

[0066] The obtained sample was naturally cooled to room temperature. 0.9 mL of suspension was taken by using a syringe, and filtered by using a 0.22 ?m organic filter membrane. The filtrate was extracted by using 0.9 mL of methylbenzene after the filtering was completed. Finally, the types of products and the proportions of various substances were qualitatively analyzed by using a gas chromatography-mass spectrometer. The results show that, in the product obtained in this example, C.sub.7H.sub.12 fuel had a mass fraction of 0%, and C.sub.10H.sub.12 fuel had a mass fraction of 100%.

Example 15

[0067] Polyethylene terephthalate (PET), sulfuric acid, ferrous sulfate, potassium peroxymonosulfate, and water were mixed well to obtain a mixed solution, wherein in the mixed solution, the PET had a mass concentration of 5 g/L, the sulfuric acid had a concentration of 5?10.sup.?4 mol/L, the ferrous sulfate had a concentration of 9.75 mmol/L, and the potassium peroxymonosulfate had a concentration of 9.75 mmol/L; and the mixed solution was reacted at 100? C. for 12 h to complete the treatment.

[0068] The obtained sample was naturally cooled to room temperature. 0.9 mL of suspension was taken by using a syringe, and filtered by using a 0.22 ?m organic filter membrane. The filtrate was extracted by using 0.9 mL of methylbenzene after the filtering was completed. Finally, the types of products and the proportions of various substances were qualitatively analyzed by using a gas chromatography-mass spectrometer. The results show that, in the product obtained in this example, C.sub.7H.sub.12 fuel had a mass fraction of 0%, and C.sub.10H.sub.12 fuel had a mass fraction of 100%.

Example 16

[0069] Polyethylene (PE), sulfuric acid, copper sulfate, sodium peroxymonosulfate, and water were mixed well to obtain a mixed solution, wherein in the mixed solution, the PE had a mass concentration of 1 g/L, the sulfuric acid had a concentration of 5?10.sup.?3 mol/L, the copper sulfate had a concentration of 0.4875 mmol/L, and the sodium peroxymonosulfate had a concentration of 13 mmol/L; and the mixed solution was reacted at 100? C. for 12 h to complete the treatment.

[0070] The obtained sample was naturally cooled to room temperature. 0.9 mL of suspension was taken by using a syringe, and filtered by using a 0.22 ?m organic filter membrane. The filtrate was extracted by using 0.9 mL of methylbenzene after the filtering was completed. Finally, the types of products and the proportions of various substances were qualitatively analyzed by using a gas chromatography-mass spectrometer. The results show that, in the product obtained in this example, C.sub.7H.sub.12 fuel had a mass fraction of 0%, and C.sub.10H.sub.12 fuel had a mass fraction of 100%.

Example 17

[0071] Polyethylene terephthalate (PET), sulfuric acid, copper sulfate, sodium peroxymonosulfate, and water were mixed well to obtain a mixed solution, wherein in the mixed solution, the PET had a mass concentration of 1 g/L, the sulfuric acid had a concentration of 5?10.sup.?3 mol/L, the copper sulfate had a concentration of 0.4875 mmol/L, and the sodium peroxymonosulfate had a concentration of 13 mmol/L; and the mixed solution was reacted at 80? C. for 12 h to complete the treatment.

[0072] The obtained sample was naturally cooled to room temperature. 0.9 mL of suspension was taken by using a syringe, and filtered by using a 0.22 ?m organic filter membrane. The filtrate was extracted by using 0.9 mL of methylbenzene after the filtering was completed. Finally, the types of products and the proportions of various substances were qualitatively analyzed by using a gas chromatography-mass spectrometer. The results show that, in the product obtained in this example, C.sub.7H.sub.12 fuel had a mass fraction of 0%, and C.sub.10H.sub.12 fuel had a mass fraction of 100%.

Example 18

[0073] Polyethylene (PE), sulfuric acid, ferrous sulfate, sodium peroxymonosulfate, and water were mixed well to obtain a mixed solution, wherein in the mixed solution, the PE had a mass concentration of 2 g/L, the sulfuric acid had a concentration of 5?10.sup.?3.5 mol/L, the ferrous sulfate had a concentration of 13 mmol/L, and the sodium peroxymonosulfate had a concentration of 13 mmol/L; and the mixed solution was reacted at 140? C. for 3 h to complete the treatment.

[0074] The obtained sample was naturally cooled to room temperature. 0.9 mL of suspension was taken by using a syringe, and filtered by using a 0.22 ?m organic filter membrane. The filtrate was extracted by using 0.9 mL of methylbenzene after the filtering was completed. Finally, the types of products and the proportions of various substances were qualitatively analyzed by using a gas chromatography-mass spectrometer. The results show that, in the product obtained in this example, C.sub.7H.sub.12 fuel had a mass fraction of 0%, and C.sub.10H.sub.12 fuel had a mass fraction of 100%.

Example 19

[0075] Polyethylene terephthalate (PET), sulfuric acid, ferrous sulfate, sodium peroxymonosulfate, and water were mixed well to obtain a mixed solution, wherein in the mixed solution, the PET had a mass concentration of 2 g/L, the sulfuric acid had a concentration of 5?10.sup.?3.5 mol/L, the ferrous sulfate had a concentration of 13 mmol/L, and the sodium peroxymonosulfate had a concentration of 13 mmol/L; and the mixed solution was reacted at 80? C. for 12 h to complete the treatment.

[0076] The obtained sample was naturally cooled to room temperature. 0.9 mL of suspension was taken by using a syringe, and filtered by using a 0.22 ?m organic filter membrane. The filtrate was extracted by using 0.9 mL of methylbenzene after the filtering was completed. Finally, the types of products and the proportions of various substances were qualitatively analyzed by using a gas chromatography-mass spectrometer. The results show that, in the product obtained in this example, C.sub.7H.sub.12 fuel had a mass fraction of 0%, and C.sub.10H.sub.12 fuel had a mass fraction of 100%.

[0077] According to the above examples, the present invention provides a method for treating a waste plastic based on a persulfate system, which comprises the following steps: mixing the waste plastic, sulfuric acid, sulfate, peroxymonosulfate, and water, and reacting at 80-140? C. for 3-15 h to complete the treatment. The present invention reasonably regulates and controls each parameter in the reaction process while constructing a homogeneous catalysis system of transition metal (bivalent copper and bivalent iron) activated peroxymonosulfate, and finally directionally converts the waste plastic into C.sub.7H.sub.12 and C.sub.10H.sub.12 fuels, which realizes high-efficiency recycling of the waste plastic, has a simple and convenient working procedure, and has a wide application prospect.

[0078] The above descriptions are only preferred examples of the present invention. It should be noted that those of ordinary skill in the art can also make several improvements and modifications without departing from the principle of the present invention, and such improvements and modifications shall fall within the protection scope of the present invention.